Into the weeds engine design for fuel efficiency discussion.

[Dave_J]

For a Dodge D150 and towing....

I think I'd find a wrecked Dodge Ram 1500 with a Magnum 5.9 and steal all the wiring and computer too.

Bore it 0.040" and 4" stroke it to 410 and use some UTAwsom parts.

A Magnum "Voodoo" style fast rate lift 262 to 268 Degree cam advanced 4 to 8 degrees.

Deep sump Kevco 8 quart oil pan with a scraper, run 6 quarts. Stock volume oil pump with a Kevco Oil pump cover. Use the 3/4 groove 360 Main bearings. Open up the main bearing feed holes to the oval hole in the block.

The Mag engines are already larger Oil passage like the Sanborn mod done to LA blocks

Then use a HP Tuner to flash the computer.

A prepped A-500 trans and a set of 3.21:1 gears

This shoud give about 415 HP and over 500 Lb/Ft torque from 1500 to 5000 RPM

 

[mhuppertz]

.035" Quench on iron heads allow higher static compression ratios without detonation. As partially stated above, thin rings reduce friction and also measurably reduce heat load into the water jacket. An intake manifold with high velocity runners helps with better cylinder filling and swirl, and aid in scavenging. If you want to have a little fun get a cam with a little more overlap that has timing events that increase dynamic cylinder pressure if your static is a little low. Whiplash cams do this pretty well, as well as Thumper and Bootlegger cams. On a big block I recomment an original Torker. Even though it is a single plane, the long straight, relitively small cross section runners make a ton of torque on the dyno tests I have seen, and from my own experience they really kick butt on 303's and 440's. Also (on a big block) 2" long tube headers with 24" collector extensions and a crossover will really braoden out the torque curve not not affect higher RPM power. And if you are running a carburetor, highly recommend a Thermoquad. If you put a wideband O2 sensor in each collector you can tune them with metering rods, jets and springs to perform very close to fuel injection. If running fuel injection, highly recomment a throttle body solution becasue the older intakes and head ports are designed for "wet" flow, and becasue the additional cooling and evaporation rates help fuel economy, torque, and helps control detonation. In hot climates water/meth injection is very effective, even on a naturally aspirated engine. And if you ever have to take off a head, you will be astonished at how carbon free the combustion chambers, pistons and valves are. They look new after a ton on miles. Multi-spark is a great choice, and the facory hall-effect distributors work perfectly for street or strip. Don't forget back-cut valves, minimum spring weights for the cam, plunge cutting the bowls and blending, and to run the factory stamped steel rockers if your spings are singles with a damper and your lift is close to .5" or so. They are very light, and becasue of the design are cushioned by a hydrodynamic oil wedge just like the bearings, so almost no friction. Of course this assumes a hydraulic flat tappet cam.

 

[Bewy]

This thread was about fuel efficiency. Agree with much of the above post except for Torker intake & Whip/Boot cams. These cams have a lot of overlap & your HP is going straight out the tail pipe instead of pushing down on pistons. Torker is not a good idea for fuel economy & are misnamed.
Good fuel economy requires an intake with a strong carb signal for precise, non-wasteful fuel delivery, & the big open plenum in a Torker or single plane intake does not provide this.

 

[273]

Point of this thread is discussing engine building strategies for both fuel efficiency and running on cheap gas.


@mpgmike I am hoping you might be willing to share some of the latest info on the topic.


Part 1: Combustion chamber design.

Assume a couple givens:

Good quench is a given in this hypothetical, no matter the type head chamber involved.

Also the theoretical engine will be a street engine. Jack of all trades 1500 to 5000-5500 rpm. Some would consider it a truck motor based on the rpm, or daily driver, call it what you will.

1 A: Cylinder head chamber design.

What (if any) cylinder head chamber type offers the most in terms of efficient burn? All things like compression ratio and quench being equal, is there an advantage to a heart shaped closed chamber (IE magnum small block head),a bathtub closed chamber (think 60s big block 516 head), and a regular open chamber like a 906 or J head. Assume each has appropriate piston to achieve quench.

Which chamber shape could run on the lowest octane fuel all else being equal? Or asked another way, which
could run the highest compression ratio on 87 octane?

1 B: Piston top design. Is the flat top closed chamber combo the best for efficiency and low octane tolerance, or would a step head piston set up for quench in a closed chamber be? Not talking about the 80's giant pop up dome pistons here, think KB pistons with the step designed for quench.

1 C: Mods to be considered to 1A and 1B: Given is to relieve all sharp edges. What about Signh grooves? Are they beneficial for either fuel mileage or octane tolerance? How many grooves and what part of the chamber should the grooves be pointed towards?

How about dimples in head chamber or on piston top? What if any benefit would chamber relief cuts around the valves or a 15 degree top cut in valve job have in efficiency terms? Does either effect swirl in the chamber and if so in what way?

Related article: A New Diesel Piston That Increases Power And Reduces Emissions


If there is any interest in the topic, part II will be about the rotating assembly- ie bore v/s stroke, rod ratio, pistons and rings, etc.

Depends what we're talking here, actually recoup the money spent plus a sizeable savings in a reasonable time frame? I'd say that's generally a waste of time, say you spend $ 3000 a year in gas and spend $ 3000 to save 20% that would take 5 years just to recoup, and 20% over a well tuned engine would be huge gain.

Now if your talking decent mileage for a given power that's different cause hp cost dollars and doesn't over matter if it's recouped, still wouldn't go to crazy expenses to gain mpg cause over a certain point fuel mileage is hard to gain, My Avenger with all it's fuel mileage tech only gets 5 mpg better than my old 5th Ave and I did zero to get the best out of my 5th Ave.

For mileage I'd say besides a good tune and exhaust, cam cr gearing gonna be the lowest hanging fruit above that gains will tend to be small per mod and generally $$$ per mpg gain will go up. For NA power that won't overall kill mpg good heads will be best bet.

 

[273]

Thanks AJ, lots of good info.

Much more helpful than being told to buy a small car which is what my post about specifics was in response to.

I am curious as to thoughts on bore v/s stroke. Bore sizes for newer v8 LS and Hemi are all close to 4 inches. Is this due primarily to emissions, fuel economy, or do both go hand in hand because of a more complete burn?

Small bore with long stroke probably has a slight advantage but is it enough to worry about.

Your building a truck engine so idle-3500 rpm or so is what's most important, to build NA power in that range would be mainly be from displacement, VE% and CR obviously anything to increase efficiency in that range, and VE% doesn't mean strangle your engine to death.

Realistically a well put together /6 to 440 ain't gonna be a huge difference especially with similar performance. It takes a certain amount of hp to move your car down the road, mpg comes from how efficiently the engine makes it at part throttle, there's not a huge efficiency gap in the engines were talking about unless you do something seriously wrong design wise like a huge cam etc...

 

[Brooks James]

My recipe which I have most of the parts for:

1967 closed chamber 273 heads on a 69 318, to raise compression

Doug's D453 headers 1 5/8 tubes

Edelbrock Streetmaster 318, designed for economy and torque,
from idle to 4500

400 cfm AFB or a Thermoquad

Custom ground cam for high vacuum and economy

MP dizzy with adjustable vacuum canister

MSD 6AL and MSD 8680, dash controlled timing

Aluminum 833 overdrive 4 speed with OD .72 ratio combined with a
2.94 8 3/4 axle should give about
2.20 axle ratio, If I can get some 2.76's it would go down to 2.00 !!


IF gas gets crazy $, I'll be putting it together, or if my son stays in Colorado, it would be a great interstate cruiser to get out there

 

[Dale Davies]

Point of this thread is discussing engine building strategies for both fuel efficiency and running on cheap gas.


@mpgmike I am hoping you might be willing to share some of the latest info on the topic.


Part 1: Combustion chamber design.

Assume a couple givens:

Good quench is a given in this hypothetical, no matter the type head chamber involved.

Also the theoretical engine will be a street engine. Jack of all trades 1500 to 5000-5500 rpm. Some would consider it a truck motor based on the rpm, or daily driver, call it what you will.

1 A: Cylinder head chamber design.

What (if any) cylinder head chamber type offers the most in terms of efficient burn? All things like compression ratio and quench being equal, is there an advantage to a heart shaped closed chamber (IE magnum small block head),a bathtub closed chamber (think 60s big block 516 head), and a regular open chamber like a 906 or J head. Assume each has appropriate piston to achieve quench.

Which chamber shape could run on the lowest octane fuel all else being equal? Or asked another way, which
could run the highest compression ratio on 87 octane?

1 B: Piston top design. Is the flat top closed chamber combo the best for efficiency and low octane tolerance, or would a step head piston set up for quench in a closed chamber be? Not talking about the 80's giant pop up dome pistons here, think KB pistons with the step designed for quench.

1 C: Mods to be considered to 1A and 1B: Given is to relieve all sharp edges. What about Signh grooves? Are they beneficial for either fuel mileage or octane tolerance? How many grooves and what part of the chamber should the grooves be pointed towards?

How about dimples in head chamber or on piston top? What if any benefit would chamber relief cuts around the valves or a 15 degree top cut in valve job have in efficiency terms? Does either effect swirl in the chamber and if so in what way?

Related article: A New Diesel Piston That Increases Power And Reduces Emissions


If there is any interest in the topic, part II will be about the rotating assembly- ie bore v/s stroke, rod ratio, pistons and rings, etc.

A lot to consider with that. First is what are you cconsidering towing and how often. Back in the '60's people that towed the larger Airstream holiday trailers all drove large cars with big block engines, preferrably in the 450 CID range. Trucks at the time were plain work vehicles with few options, not like the gussied up dancehall girls they are today. If you intend a lot of towing, a big block is the way to go. A small block can be stroked and built to produce the torque required for towing, but there just is not the beef needed for longevity. There is a reason big industrial engine blocks are built from cast iron 1" to 1 1/2" thick. They have a high duty cycle, meaning they run at max or close to max design power for weeks. Our automobiles operate at light duty cycles, small throttle openings for cruise most of the time with short bursts of max power to pass or merge.
If your intended use is fairly "pedestrian" most of the time and tow occasionally and not real heavy, a stroked small block may be the best choice. A 4" stroke 5.9 Magnum may be a good choice with a fairly short duration, high lift cam to build torque.
Flat top pistons with 2 valve reliefs tend to produce better burn capability. The piston crown, depending on your head gasket, should protrude out of the block about 0.005". Chevy Gen 3 are supposed to be 0.008" above the deck surface. The Chevy rings are about 1.5mm wide or 0.060". That is 1/16". 1mm or 1.2mm rings generate less friction and you want them up fairly high.
Back to the original question; open chamber heads are prone to detonation, slow burn rates and poor emissions. In early emissions engines NOx was being looked at and increasing combustion chamber volume was a quick and inexpensive way to drop the compression ratio. High compression tends to generate the higher combustion temperatures that create the NOx. EGR was also used to reduce combustion temperatures.
Since moving on to sophisticated fuel and ignition control systems this can be mitigated. Now port and combustion chamber design that promotes swirl is encouraged. Whether the chamber is heart shaped or D shape, a good quench is desired. Porting of the intake should open up the cylinder wall side of the port. Any work on the cylinder center side of the port should be minimal, mostly cleanup of ridges from casting. The port bowl should have a bias or angle compared to the valve of about 10° pointing toward the cylinder center. This promotes swirl. There is a do not touch area of unshrouding between the chamber wall and intake valve from about the center of the valve head up to the quench pad. Any work there will tend to cancel swirl and work against you.
For the exhaust, angle the port bowl the opposite direction to the intake, as that is where the flow wants to generally go. If there is a bit of a quench pad on the sparkplug side, round that edge of to let the exhaust follow around and into the port. On the main quench pad, lay back the edge to direct exhaust into the port.
For a street oriented engine with fairly restrictive exhaust ports, unshrouding the valve and cutting the valve and seat for a 40° seat can aid low lift flow. The intakes will benefit with a 25° or 30° back cut.
Not sure about incorporating the Somender Singh grooves. If you do decide to try them, I think 1 to 3 angled to enhance the intake induced swirl as the piston is aproaching TDC and the plug is sparking may be beneficial.
If it will fit under the hood, a dual plane airgap manifold works for a broad torque curve. If you go with an airgap, use a carb with annular discharge boosters like the AVS2. The Rochester Quadrajet triple booster functions well also.
For exhaust, a tri Y header improves low and mid torque.
I would recommend watching David Vizard's Powertec 10 Youtube videos on porting. Yes most is Chev and Ford, but the principles apply and you adapt differences. He gets fairly detailed on the Ford E7 head and 289 for valve unshrouding and where to and not to.
Two Powertec 10 videos to watch are Ep80 and Ep86. These pertain to the UTG initiated Mission Impossible project on a 318. Ep80 discusses some of what I related about open chamber heads. DV is investigating milling the head 0.100" to get some quench.

 

[mgoblue9798]

I do not know.
But I'm always willing to guess;
A four inch bore, give or take a lol, makes enough room for typical valve sizes, and for them not to be shrouded. Any smaller and you soon have to give up either valve diameter, or inter-valve support, or they get to be shrouded.
Long strokes allow more power-stroke time, at cruise rpm, to extract energy.
An old 318 had a cam of 240/248/112. In at 2* advanced this was 130 degrees for compression and 122* for power.
Now, 122* for power extraction is a stinking long time in terms of crank rotation. By the the time the exhaust valve opens, and with an SCR of sub 8/1 , the pressure of those hot exhaust gasses are almost back to atmospheric pressure, having release all they had to give. This is great for fuel economy. Even for making torque.
But those same 122* of power-extraction, if you want to make power, steal a lotta time from the exhaust cycle, and so those are usually the first to get sacrificed./ A typical power stroke for making street-power will be close to or less than ~105*..
If you think about this;
When the piston gets to 122* ATDC, it is slowing down and is just 58* from the Bottom of it's travel. My guess is that in a 3.315 stroke engine, this is less that 1" from the bottom.
But say you had a 3.58 stroke engine, this same 122 degrees would put the piston further from the bottom..... Which means, you can run more exhaust duration, and still have a similar amount of power extraction clock-time. And if you think about that long enough;
you might get to thinking about comparing the fuel economy potential of two same engines except one with a 3.315 stroke and the other at 3.58.
But if you did think about that, rightaway you might think what if I put a one-size bigger cam into the 3.58 engine. With say 7* less power-stroke and those 7* given to the exhaust stroke.
Rightaway the 3.58 stroke would make more power and torque at low-rpm, by virtue of the greater cubic inches. But with the bigger cam, it will also make more midrange and hi-rpm power.
but with a similar amount of clock-time spent in the power-stroke while cruising, should make similar fuel-economy.
And if you think about this long enough, there's a good chance you will conclude to never again build a 3.315 stroke SBM, but if you did; it sure as chit would not be at 8.0 Scr, lol, Nor with a pizzazz 240/248/112 hydraulic cam.
From the decks down, there is nothing wrong with a 318LA. I mean spec-wise it is almost the same as a 340, save the overbore. And it is almost the same as a 360, save for a bit of of bore and stroke.
What the 318 has lacked since 1972 has always been compression.
People say it doesn't matter that much, and under racing conditions they are sorta right. Once the rpm is up, cylinder pressure, or lack of it, becomes minor compared to the operating rpm.
and, while cruising, it is again almost a non issue, at typically posted speed limits.
Where/when cylinder pressure matters is exactly where a streeter operates. Namely; on/off the throttle, banging back and forth between stall and shift-rpm in First gear, and especially when getting into second.
And it's not just the pressure I'm talking about. It's about the activity that happens in the intake manifold.
The higher your cylinder pressure is, by deduction, the smaller the total chamber volume has to be. And the smaller it is, the quicker it will respond to the falling piston on the intake stroke.... because..... a big chamber acts like an Air-spring; you can stretch it a long way before the plenum even knows it's there because it is busy listening to 3 other air-springs on every revolution. It be like, the plenum is saying" yeah yeah, I'll get there in a sec." Whereas with a small chamber, the falling piston puts a good pull on the plenum, demanding attention like, right NOW dammit!
This translates to an engine that is always ready to rock, just stab the pedal and hang on! As you can see, this has ZERO to do with the Compression stroke! Yet the only way to get this kind of throttle-response, Normally-Aspirated, is with a hi-compression ratio.

IDK anything about emissions, and pretty much don't care,
cuz IMO, it ain't cars that are a problem.
IDK anything about what factories think.
or IMO, even if they think at all. lol.

Oh almost forgot; B/S ratios;
273 is 3.63/3.315= 1.095, baseline
360 is 4.00/3.58= 1.117, this 1.02% bigger than 273
318 is 3.91/3.315= 1.179, this is 1.056 bigger than the 360
340 is 4.04/3.315= 1.219, this is 1.034 bigger than the 318

If a bore to stroke ratios have anything to do with fuel mileage,
a 360 should, when similarly equipped........ make BETTER fuel economy than any 318 ever built, and even rival a 273, the difference going to internal friction, which we can do something about. And you may know this; my 367 was once combo'd to exceed any factory 273 fuel economy spec ever published, for a car at 3650 pounds (me in it); I mean smashed it.
So there is that, .......... but it wasn't similarly equipped, lol.

@AJ/FormS I have been crunching numbers for dynamic compression and V/P using the Wallace racing calculator. This is what it came up with:


Static compression ratio of 9:1.
Effective stroke is 3.56 inches.
Your dynamic compression ratio is 8.59:1 .
Your dynamic cranking pressure is 179.44 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 8.59 :1.
V/P (Volume to Pressure Index) is 228

Assuming an iron closed chamber head with .040 quench, sodium exhaust valve, and polished chamber and pistons, what octane fuel would you expect this to require?

 

[mgoblue9798]

Depends what we're talking here, actually recoup the money spent plus a sizeable savings in a reasonable time frame? I'd say that's generally a waste of time, say you spend $ 3000 a year in gas and spend $ 3000 to save 20% that would take 5 years just to recoup, and 20% over a well tuned engine would be huge gain.

Now if your talking decent mileage for a given power that's different cause hp cost dollars and doesn't over matter if it's recouped, still wouldn't go to crazy expenses to gain mpg cause over a certain point fuel mileage is hard to gain, My Avenger with all it's fuel mileage tech only gets 5 mpg better than my old 5th Ave and I did zero to get the best out of my 5th Ave.

For mileage I'd say besides a good tune and exhaust, cam cr gearing gonna be the lowest hanging fruit above that gains will tend to be small per mod and generally $$$ per mpg gain will go up. For NA power that won't overall kill mpg good heads will be best bet.

You are correct about the cost to build an engine and ROI. I am building one anyways regardless, and have everything on hand to do so with the exception of a cam.

Cost savings add up quicker on a working truck engine than a typical passenger car due to the lower mpgs involved.

 

[Bewy]

The dynamic comp ratio is based on the intake valve closing event; ie how much air does the cyl trap. Since intake port & the attached intake manifold runner flow can vary tremendously, I find it a useless calculation & it beats me why people use it....

 

[Hysteric]

Point of this thread is discussing engine building strategies for both fuel efficiency and running on cheap gas.

The difference between efficiency and performance is the richer side of stoich. Since you want to go into the "weeds" per say I would suggest first grasping what the foundation of engine design really relates to which is "combustion"

Here's the advice I was given from the guy who new more than I'll likely ever to get the chance to figure out in regards to chryslers:

With the Chrysler engine having a long rod ratio the piston dwells for longer at TDC so the opportunity for a dished piston is there for a different reason than a Chev etc. Dishing the piston gives a better chamber because the flame kernel is further way from metal in every direction so thats good.
It makes the plug more central when viewed from the side if you get what I mean. But the reason for doing it with a Chrysler is different to a Chev. Doing it in the Chrysler long rod engine is not just that the piston clearance is there but its to create a longer flame path before the flame extinguishes against a surface while the rod is dwelling at TDC. 1.8 stroke rod ratio motors are different gas production to shorter rod ratio motors. They have more complete burn with less HC wastage. they are awesome to work with, unfortunately theres not much Chrysler racing stuff here in Oz.

As for combustion:

"The most important stage is the preparation prior to ignition. When that is not right, as in this engine, the flame kernel doesn't grow fast enough and the result is a lower cylinder pressure at an equivalent crank position to a good kernel. The flame kernel is a growth of laminar conditions to around 20mm diameter, then the conditions change to turbulent flame and the speed of burn is much faster. What you have to know is its droplet size and the vaporization that influences the speed of both laminar and turbulent flames. So when an engine has large droplets its needs a lot of heat to vaporize them in the time available.
When I say to you guys that a particular engine hasn't got enough vaporization that is what I'm commenting on. How it looks inside the cylinder is like this, the AFR at ignition time is leaner than the average of the cylinder, lets say the average is 12.8 but at ignition time the AFR around the plug is AFR 14, the flame is going to grow slow and some of the flames energy is going to used in vaporizing the fuel thats not gas yet. So the flame kernel doesn't generate enough heat and you dont get a TAN plug, you also run the risk of extinguishing the flame if turbulence is poorly directed. The kernel uses up about 10% of the mixture then the conditions transition to turbulent. Once the flame is turbulent it cant be extinguished. However the conditions toward the remainder of the chamber ahead of the flame kernel front are still under vaporized, therefor requiring energy from the advancing flame front to vaporize mixture ahead of the front, not an efficient way to go. It's the burn angle duration between 10 and 90% that matters. Good burns are in the range of 15 to 25 degrees. Burns of engine with poor vaporization can be as long as 45 degrees. THAT'S WHY some engines make best power at timings like 38 to 45 degrees compared to another that best at 28 degrees."

Spend some time reading this:



This is the basic scenario of combustion in a cylinder from start to end.
1. Fuel is converted from liquid form to gas form. The amount of chemicals that are converted prior to ignition determines the regularity of the flame kernel and the strength of it. The temperature of the air during the compression time determines the number of fuel molecules that are heated via convection and turned to gas ready to burn.
2. Its not enough to just work on vaporization, the fuel molecules have to be spread throughout the chamber in a homogenous state. In designs for emissions it is deliberately done to create lean areas in the center of the chamber and a different mixture at the sparkplug and the outer areas of the chamber. The jury is out on the effectiveness of these approaches. For racing the approach is for an even spread of mixture because that allows a consistent tune throughout the chamber. In other words the design should prevent you from having to correct a lean detonation in one area by flooding it stupid elsewhere to bring the problem area under control.
3. The spark ignites the mixture present at the plug location. The initial flame growth is a laminar flame. Its laminar until its approx 12mm diameter. It takes approx 10 degrees of crank rotation at ANY RPM to achieve that diameter. The AFR of the mixture has hardly any effect upon the flame during its laminar stage. The burn speed is smooth and consistent during laminar flame. The burn speed is variable with the RPM but its not variable per event due to any factors like AFR Its varied a little bit by the vaporization because a droplet of un-vaporized fuel hit by the laminar flame front absorbs energy from the flame. Anytime energy is absorbed from a flame the flame speed is slowed. The arc energy is the most influential factor to the flame kernel. The energy field from an arc of the power of a crane HI-6 is approx 6mm radius. That’s the size of the laminar limit of the flame kernel. The power of the ignition is paramount to vaporizing the fuel load in that zone and achieving a stable flame kernel under high RPM conditions. The flame kernel is basically unstoppable once it reaches 12mm diameter.
4. At 12mm diameter and beyond the flame changes to a turbulent flame. Its starts to fold over on itself and looks like one of those bed donnas, quilts or cover things that are made of pockets of insulation type material. The pockets formed from stitching is what the flame starts to do, it forms that way from advancing and slowing rates within the original laminar form. Its like a stage of transitional flow in a pipe. It is at this time that mixture can be injected into the flame from areas like the squish bands. Injecting this fresh mixture into the fledgling turbulent flame supercharges its burn rate, its takes off ridiculously fast once you shove the squish in there.
5. The now fully turbulent flame is now at near TDC piston position and its burnt about 60 to 70 % of the mixture mass. Its at this point that you need to consider if your fuel has low octane chemicals in it(eg street unleaded) and you should start to gas them now so that if they decide to detonate they will at least be doing it on the power stroke and the detonation energy could be used for advantage. Does this wring a bell in your head about how one particular EMC winner for years was doing it?
6. By 14 to 18 degrees after TDC the mixture should be about 90 to 90% mass burnt and the cylinder should be at max pressure. It varies in position because of rod ratio and things like that that effect the mechanical efficiency of the engine and the location of your particular engines best peak pressure point. (PPP) But the PPP is in that Zone. That’s why we have computers to adjust the ignition timing so we can fiddle around in the top end and find the PPP.
7. Note at the PPP we have not completely burnt the fuel mass,we have only burnt 95% of it. That’s because we need the remaining 5% to chase the piston down the bore and to provide some energy to the exhaust pulse. If we don’t have enough energy for the exhaust pulse we cant scavenge the cylinder ready for the next charge. You can alter the exhaust pulse energy in many ways. Anything that alters the valve opening point, anything that changes burn time, anything that alters burn percentage at PPP, and the list would go on and on.
8. All this time some of the burn energy is going into the water jacket and some energy is transferring to the piston. If the piston is ascending, then that part of the energy is returned to the chamber and its used to keep improving the burn (hopefully, and not to start melting stuff) If the pistons descending then its converted by the crank/rod assembly to torque.
9. The unused energy from the burn (that which is not converted to torque etc) is exhausted as heat and pressure and speed of gas flow. We measure with thermocouples the temp and discuss in the pits if its rich or lean etc but in reality its rubbish. We should be discussing if we have enough exhaust retention or removal from the chamber and we should be discussing if the gas is CO or CO2 and we should be discussing if the gas temperature is assisting us in vaporization of the next charge and asking if there a better way that may have some advantages with less of the disadvantages of retention. Reading the spark plugs is a way to start discussing these factors.

That should keep you entertained for a while. Good Luck!

 

[273]

The difference between efficiency and performance is the richer side of stoich. Since you want to go into the "weeds" per say I would suggest first grasping what the foundation of engine design really relates to which is "combustion"

Here's the advice I was given from the guy who new more than I'll likely ever to get the chance to figure out in regards to chryslers:



As for combustion:

"The most important stage is the preparation prior to ignition. When that is not right, as in this engine, the flame kernel doesn't grow fast enough and the result is a lower cylinder pressure at an equivalent crank position to a good kernel. The flame kernel is a growth of laminar conditions to around 20mm diameter, then the conditions change to turbulent flame and the speed of burn is much faster. What you have to know is its droplet size and the vaporization that influences the speed of both laminar and turbulent flames. So when an engine has large droplets its needs a lot of heat to vaporize them in the time available.
When I say to you guys that a particular engine hasn't got enough vaporization that is what I'm commenting on. How it looks inside the cylinder is like this, the AFR at ignition time is leaner than the average of the cylinder, lets say the average is 12.8 but at ignition time the AFR around the plug is AFR 14, the flame is going to grow slow and some of the flames energy is going to used in vaporizing the fuel thats not gas yet. So the flame kernel doesn't generate enough heat and you dont get a TAN plug, you also run the risk of extinguishing the flame if turbulence is poorly directed. The kernel uses up about 10% of the mixture then the conditions transition to turbulent. Once the flame is turbulent it cant be extinguished. However the conditions toward the remainder of the chamber ahead of the flame kernel front are still under vaporized, therefor requiring energy from the advancing flame front to vaporize mixture ahead of the front, not an efficient way to go. It's the burn angle duration between 10 and 90% that matters. Good burns are in the range of 15 to 25 degrees. Burns of engine with poor vaporization can be as long as 45 degrees. THAT'S WHY some engines make best power at timings like 38 to 45 degrees compared to another that best at 28 degrees."

Spend some time reading this:



This is the basic scenario of combustion in a cylinder from start to end.
1. Fuel is converted from liquid form to gas form. The amount of chemicals that are converted prior to ignition determines the regularity of the flame kernel and the strength of it. The temperature of the air during the compression time determines the number of fuel molecules that are heated via convection and turned to gas ready to burn.
2. Its not enough to just work on vaporization, the fuel molecules have to be spread throughout the chamber in a homogenous state. In designs for emissions it is deliberately done to create lean areas in the center of the chamber and a different mixture at the sparkplug and the outer areas of the chamber. The jury is out on the effectiveness of these approaches. For racing the approach is for an even spread of mixture because that allows a consistent tune throughout the chamber. In other words the design should prevent you from having to correct a lean detonation in one area by flooding it stupid elsewhere to bring the problem area under control.
3. The spark ignites the mixture present at the plug location. The initial flame growth is a laminar flame. Its laminar until its approx 12mm diameter. It takes approx 10 degrees of crank rotation at ANY RPM to achieve that diameter. The AFR of the mixture has hardly any effect upon the flame during its laminar stage. The burn speed is smooth and consistent during laminar flame. The burn speed is variable with the RPM but its not variable per event due to any factors like AFR Its varied a little bit by the vaporization because a droplet of un-vaporized fuel hit by the laminar flame front absorbs energy from the flame. Anytime energy is absorbed from a flame the flame speed is slowed. The arc energy is the most influential factor to the flame kernel. The energy field from an arc of the power of a crane HI-6 is approx 6mm radius. That’s the size of the laminar limit of the flame kernel. The power of the ignition is paramount to vaporizing the fuel load in that zone and achieving a stable flame kernel under high RPM conditions. The flame kernel is basically unstoppable once it reaches 12mm diameter.
4. At 12mm diameter and beyond the flame changes to a turbulent flame. Its starts to fold over on itself and looks like one of those bed donnas, quilts or cover things that are made of pockets of insulation type material. The pockets formed from stitching is what the flame starts to do, it forms that way from advancing and slowing rates within the original laminar form. Its like a stage of transitional flow in a pipe. It is at this time that mixture can be injected into the flame from areas like the squish bands. Injecting this fresh mixture into the fledgling turbulent flame supercharges its burn rate, its takes off ridiculously fast once you shove the squish in there.
5. The now fully turbulent flame is now at near TDC piston position and its burnt about 60 to 70 % of the mixture mass. Its at this point that you need to consider if your fuel has low octane chemicals in it(eg street unleaded) and you should start to gas them now so that if they decide to detonate they will at least be doing it on the power stroke and the detonation energy could be used for advantage. Does this wring a bell in your head about how one particular EMC winner for years was doing it?
6. By 14 to 18 degrees after TDC the mixture should be about 90 to 90% mass burnt and the cylinder should be at max pressure. It varies in position because of rod ratio and things like that that effect the mechanical efficiency of the engine and the location of your particular engines best peak pressure point. (PPP) But the PPP is in that Zone. That’s why we have computers to adjust the ignition timing so we can fiddle around in the top end and find the PPP.
7. Note at the PPP we have not completely burnt the fuel mass,we have only burnt 95% of it. That’s because we need the remaining 5% to chase the piston down the bore and to provide some energy to the exhaust pulse. If we don’t have enough energy for the exhaust pulse we cant scavenge the cylinder ready for the next charge. You can alter the exhaust pulse energy in many ways. Anything that alters the valve opening point, anything that changes burn time, anything that alters burn percentage at PPP, and the list would go on and on.
8. All this time some of the burn energy is going into the water jacket and some energy is transferring to the piston. If the piston is ascending, then that part of the energy is returned to the chamber and its used to keep improving the burn (hopefully, and not to start melting stuff) If the pistons descending then its converted by the crank/rod assembly to torque.
9. The unused energy from the burn (that which is not converted to torque etc) is exhausted as heat and pressure and speed of gas flow. We measure with thermocouples the temp and discuss in the pits if its rich or lean etc but in reality its rubbish. We should be discussing if we have enough exhaust retention or removal from the chamber and we should be discussing if the gas is CO or CO2 and we should be discussing if the gas temperature is assisting us in vaporization of the next charge and asking if there a better way that may have some advantages with less of the disadvantages of retention. Reading the spark plugs is a way to start discussing these factors.

That should keep you entertained for a while. Good Luck!

Really what's the OP gonna do with this?

Not saying he can't get a bit better than factory, take the 360 which is good work truck engine from 71-2002 there little difference in intown mpg throughout the years and a bit more on the highway mainly down to OD and aerodynamics and even the Hemi only had a slight improvement, with all the Chrysler and industry engineers spending billions over 30 years
basically all we got better performance with similar mileage.

 

[Dale Davies]

The difference between efficiency and performance is the richer side of stoich. Since you want to go into the "weeds" per say I would suggest first grasping what the foundation of engine design really relates to which is "combustion"

Here's the advice I was given from the guy who new more than I'll likely ever to get the chance to figure out in regards to chryslers:



As for combustion:

"The most important stage is the preparation prior to ignition. When that is not right, as in this engine, the flame kernel doesn't grow fast enough and the result is a lower cylinder pressure at an equivalent crank position to a good kernel. The flame kernel is a growth of laminar conditions to around 20mm diameter, then the conditions change to turbulent flame and the speed of burn is much faster. What you have to know is its droplet size and the vaporization that influences the speed of both laminar and turbulent flames. So when an engine has large droplets its needs a lot of heat to vaporize them in the time available.
When I say to you guys that a particular engine hasn't got enough vaporization that is what I'm commenting on. How it looks inside the cylinder is like this, the AFR at ignition time is leaner than the average of the cylinder, lets say the average is 12.8 but at ignition time the AFR around the plug is AFR 14, the flame is going to grow slow and some of the flames energy is going to used in vaporizing the fuel thats not gas yet. So the flame kernel doesn't generate enough heat and you dont get a TAN plug, you also run the risk of extinguishing the flame if turbulence is poorly directed. The kernel uses up about 10% of the mixture then the conditions transition to turbulent. Once the flame is turbulent it cant be extinguished. However the conditions toward the remainder of the chamber ahead of the flame kernel front are still under vaporized, therefor requiring energy from the advancing flame front to vaporize mixture ahead of the front, not an efficient way to go. It's the burn angle duration between 10 and 90% that matters. Good burns are in the range of 15 to 25 degrees. Burns of engine with poor vaporization can be as long as 45 degrees. THAT'S WHY some engines make best power at timings like 38 to 45 degrees compared to another that best at 28 degrees."

Spend some time reading this:



This is the basic scenario of combustion in a cylinder from start to end.
1. Fuel is converted from liquid form to gas form. The amount of chemicals that are converted prior to ignition determines the regularity of the flame kernel and the strength of it. The temperature of the air during the compression time determines the number of fuel molecules that are heated via convection and turned to gas ready to burn.
2. Its not enough to just work on vaporization, the fuel molecules have to be spread throughout the chamber in a homogenous state. In designs for emissions it is deliberately done to create lean areas in the center of the chamber and a different mixture at the sparkplug and the outer areas of the chamber. The jury is out on the effectiveness of these approaches. For racing the approach is for an even spread of mixture because that allows a consistent tune throughout the chamber. In other words the design should prevent you from having to correct a lean detonation in one area by flooding it stupid elsewhere to bring the problem area under control.
3. The spark ignites the mixture present at the plug location. The initial flame growth is a laminar flame. Its laminar until its approx 12mm diameter. It takes approx 10 degrees of crank rotation at ANY RPM to achieve that diameter. The AFR of the mixture has hardly any effect upon the flame during its laminar stage. The burn speed is smooth and consistent during laminar flame. The burn speed is variable with the RPM but its not variable per event due to any factors like AFR Its varied a little bit by the vaporization because a droplet of un-vaporized fuel hit by the laminar flame front absorbs energy from the flame. Anytime energy is absorbed from a flame the flame speed is slowed. The arc energy is the most influential factor to the flame kernel. The energy field from an arc of the power of a crane HI-6 is approx 6mm radius. That’s the size of the laminar limit of the flame kernel. The power of the ignition is paramount to vaporizing the fuel load in that zone and achieving a stable flame kernel under high RPM conditions. The flame kernel is basically unstoppable once it reaches 12mm diameter.
4. At 12mm diameter and beyond the flame changes to a turbulent flame. Its starts to fold over on itself and looks like one of those bed donnas, quilts or cover things that are made of pockets of insulation type material. The pockets formed from stitching is what the flame starts to do, it forms that way from advancing and slowing rates within the original laminar form. Its like a stage of transitional flow in a pipe. It is at this time that mixture can be injected into the flame from areas like the squish bands. Injecting this fresh mixture into the fledgling turbulent flame supercharges its burn rate, its takes off ridiculously fast once you shove the squish in there.
5. The now fully turbulent flame is now at near TDC piston position and its burnt about 60 to 70 % of the mixture mass. Its at this point that you need to consider if your fuel has low octane chemicals in it(eg street unleaded) and you should start to gas them now so that if they decide to detonate they will at least be doing it on the power stroke and the detonation energy could be used for advantage. Does this wring a bell in your head about how one particular EMC winner for years was doing it?
6. By 14 to 18 degrees after TDC the mixture should be about 90 to 90% mass burnt and the cylinder should be at max pressure. It varies in position because of rod ratio and things like that that effect the mechanical efficiency of the engine and the location of your particular engines best peak pressure point. (PPP) But the PPP is in that Zone. That’s why we have computers to adjust the ignition timing so we can fiddle around in the top end and find the PPP.
7. Note at the PPP we have not completely burnt the fuel mass,we have only burnt 95% of it. That’s because we need the remaining 5% to chase the piston down the bore and to provide some energy to the exhaust pulse. If we don’t have enough energy for the exhaust pulse we cant scavenge the cylinder ready for the next charge. You can alter the exhaust pulse energy in many ways. Anything that alters the valve opening point, anything that changes burn time, anything that alters burn percentage at PPP, and the list would go on and on.
8. All this time some of the burn energy is going into the water jacket and some energy is transferring to the piston. If the piston is ascending, then that part of the energy is returned to the chamber and its used to keep improving the burn (hopefully, and not to start melting stuff) If the pistons descending then its converted by the crank/rod assembly to torque.
9. The unused energy from the burn (that which is not converted to torque etc) is exhausted as heat and pressure and speed of gas flow. We measure with thermocouples the temp and discuss in the pits if its rich or lean etc but in reality its rubbish. We should be discussing if we have enough exhaust retention or removal from the chamber and we should be discussing if the gas is CO or CO2 and we should be discussing if the gas temperature is assisting us in vaporization of the next charge and asking if there a better way that may have some advantages with less of the disadvantages of retention. Reading the spark plugs is a way to start discussing these factors.

That should keep you entertained for a while. Good Luck!

A good description. More to it than that. Rod to stroke ratio has proven to have a minor effect. For a street engine this is not a torque or power issue. Now a long rod tends to reduce piston slap.so the engine runs quieter.
The carburetor booster venturis begin the atomization and vaporization of the fuel. The atomization is a factor of the air speed and turbulence, which shatter the droplets into tiny droplets. To get a visualization, connect a timing light. Any cylinder will be fine. You just need the strobe light. With the air cleaner lid off and the engine running, shine the timing light down the carb venturi. You need to open the throttle a bit to get the main circuit supplying fuel.
Now if you can find a throttle body injected engine, do the same. The injection at about 15PSI instead of the carb at atmospheric, does a lot better job
of atomizing the fuel. A good part of why injection gives lower emissions and better fuel economy. Of the droplets that get into the cylinder, during the initial burn, only at the surface vaporizes. What burns is the vapor around the droplets. As combustion continues, the heat causes more of the droplet to vaporize. Large droplets probably do not burn and they finally vaporize in the hot combustion gases going out the exhaust valve.
So vaporizing the fuel and air extremely well before entering the cylinder should be a good thing right? Welll, not so fast. As we learned in school science class, a bit of alcohol on the back of your hand evaporated, vaporized, very quickly and felt cold. The vaporizing fuel takes heat out of the air to vaporize. This can and does cause the air to contract slightly. However, working counter to this is the vaporized fuel takes up more volume.
Now also in school.science we learned water is an amazing chemical. Its volume decreases as the temperature is reduced to freezing, but then it expands after becoming its solid state, ice. Further cooling causes it to expand. Now that water when heated expends in volume until it boils or vaporizes. This vaporization consumes huge amounts of enegery, heat. One liter of water at 205°F becomes 1,600 liters of steam at 213°F. I describe this as an indication of the volume change as the state changes, even with minimal temperature change.
The lesson here, we need some vaporized or gaseous fuel to start combustion with the rest in very finely atomized droplets. This is partly why first port injection and now direct injection work for economy and emissions.
Carburetors: atmospheric pressure.
Throttle body injection: about 15PSI
Port injection: about 50 PSI to 100PSI
Direct injection: 500PSI to 1500PSI
Then we get into swirl and tumble in the combustion chamber. 4 valve heads tend to produce tumble. Any effect this has on combustion falls away as the RPM increases. Swirl functions to benefit the combustion throughout the RPM range. 2 valve engines tend to produce swirl, but is affected by the port location in relation to the intake valve. In most cases judiscious grinding on the cylinder wall side of the bowl will create a port bias. This is the angle of the bowl compared to the valve stem. Swirl is mixture motion in the cylinder/combustion chamber. Quench also creates beneficial mixture motion. This mixture motion aids quick combustion requiring less ignition advance.

 

[Dale Davies]

Really what's the OP gonna do with this?

Not saying he can't get a bit better than factory, take the 360 which is good work truck engine from 71-2002 there little difference in intown mpg throughout the years and a bit more on the highway mainly down to OD and aerodynamics and even the Hemi only had a slight improvement, with all the Chrysler and industry engineers spending billions over 30 years
basically all we got better performance with similar mileage.

A friend from years ago bought a Super Bee that a previos owner had installed a 426 Hemi into. They had also installed a Corvette IRS with the stock 3.07:1 gearing. On the highway that car would get 21.3 MPG US. Suppose the trans was updated with an OD and dual throttle body sequential injection was installed. Lots of air flow with excellent fuel management. I can envision 25+ MPG.
The car still had the drum brakes on the front with the Corvette discs on the rear. Really needed the front brakes changed to discs.

 

[Dale Davies]

Show me an instance where a larger engine gets better mpg for a road going vehicle.

Larger engines create excess power which is a waste in every regime except acceleration and ascent. Longer strokes, bigger bores, and large cam profiles all waste energy in order to gain power outside of the cruise regime, but average mpg is dominated by cruise.

When cruise mpg is the goal, minimizing ci is the lowest hanging fruit.

OP says he wants to tow - but does tow mpg matter as much as unladen? Without those details it's impossible to figure out which end of the displacement spectrum to be on. Knowing a max grade, weight, and operating elevation would make figuring out the minimum requirements a lot easier.

Also, typically a smaller engine with a turbo will out power and out mpg the larger na engine in almost every case. It can maximize torque when needed and use fuel sparingly when it's not. It's no secret why oems have had a love affair with boost in ecino cars for some decades.

There is a dance here. Too small an engine will be working its *** off with a heavy load. The dance part is how often you waltz and how often you Tango.
If you tow a trailer mainly only for 2 weeks for summer vacation, go with the smaller engine. If hauling a work trailer all week, the larger engine will not work as hard, may get a bit better economy and will last longer.

 

[Dale Davies]

Guys I appreciate the input but I am really only looking for answers to the specific questions I mentioned in my posts above.

All the general stuff mention I have a good handle on already. I didn't mean for this thread to be a catch all for fuel mileage ideas.

I am specifically looking for input on the types of parts I outlined in terms of fuel efficiency and octane tolerance.

I would choose quench heads. A 318 or 360 Magnum. In addition to the other videos I mentioned, try Powertec 75. A bunch of this is inexpensive things you can do while the engine is apart, to develop better combustion efficiency. This promotes torque and fuel economy.

 

[Phreakish]

There is a dance here. Too small an engine will be working its *** off with a heavy load. The dance part is how often you waltz and how often you Tango.
If you tow a trailer mainly only for 2 weeks for summer vacation, go with the smaller engine. If hauling a work trailer all week, the larger engine will not work as hard, may get a bit better economy and will last longer.

Fuel is energy. Engines turn it into work/power. Work or power required is determined by drag (both aero and friction) and incline.
Proper gear choice and driveline loss will make any two engines near identical, assuming both will produce power in excess of what's strictly required. A smaller engine has far fewer challenges to efficient combustion and extraction of that energy. From friction down to the dynamics in the combustion chamber. Larger bores, longer strokes, and engine weight will all play into the calculation and so yes there is a balance, but the 'smallest capable design' will always win the fuel consumption competition.

An over-sized engine will generally be more durable and easier to operate. But that has exactly zero to do with maximizing MPGs.

 

[Dale Davies]

Fuel is energy. Engines turn it into work/power. Work or power required is determined by drag (both aero and friction) and incline.
Proper gear choice and driveline loss will make any two engines near identical, assuming both will produce power in excess of what's strictly required. A smaller engine has far fewer challenges to efficient combustion and extraction of that energy. From friction down to the dynamics in the combustion chamber. Larger bores, longer strokes, and engine weight will all play into the calculation and so yes there is a balance, but the 'smallest capable design' will always win the fuel consumption competition.

An over-sized engine will generally be more durable and easier to operate. But that has exactly zero to do with maximizing MPGs.

Exactly. Now if we look at engine displacement and watch the carburetor. Holley has a power valve that most seem.to relate to easily. The Edelbrock and Rochester accomplish the same thing in a different way, power fuel enrichment. If we choose an engine of sufficient displacement to accomplish our requirements, without getting into the enrichment strategies, we will likely get better fuel economy. The new Chev 1500 trucks with the 2.7L turbo banger engine are an inyeresting case study. Essentially if you jam 5.4L of air through a 2.7L engine, you should get the equivalent power or torque out. Watching towing videos of those, they seem to work out really well for towing and economy. When not towing the economy should be much better than a 5.4L, or in the General's case, 5.3L V8. That cylinder deactivation, DoD or AFM appears to be problematic with engine noise and failed lifters.
It will be interesting to see how the Stellantis Hurricane engine works out. I wonder how re engineering a slant six with 7 main bearings and a DOHC 4 valve hesd would work out. Seems to be close to what the Hurricane is but stood up. An A body or say Volare with a 225 and DOHC would still be able to have a low hood line, with the advantages of the DOHC breathing. A head could be made by cutting up Mazda or Ford 2.3 or 2.5 heads and weld them together. Custom cams would be expensive for a one off, but it would be an interesting experiment. A timing cover would need to be fabricated. Could even try the VVT. The Mazda/Ford bores fit in to the realm of O/S for a slant. Compression height would be a sticking point. Maybe the 2.2L turbo pistons.

 

[Hysteric]

The injection at about 15PSI instead of the carb at atmospheric, does a lot better job
of atomizing the fuel. A good part of why injection gives lower emissions and better fuel economy. Of the droplets that get into the cylinder, during the initial burn, only at the surface vaporizes. What burns is the vapor around the droplets. As combustion continues, the heat causes more of the droplet to vaporize. Large droplets probably do not burn and they finally vaporize in the hot combustion gases going out the exhaust valve.

Not really. You may want to read and think about this paper:

Why Gasoline 90% Distillation Temperature Affects Emissions with Port Fuel Injection and Premixed Charge

 

[273]

A friend from years ago bought a Super Bee that a previos owner had installed a 426 Hemi into. They had also installed a Corvette IRS with the stock 3.07:1 gearing. On the highway that car would get 21.3 MPG US. Suppose the trans was updated with an OD and dual throttle body sequential injection was installed. Lots of air flow with excellent fuel management. I can envision 25+ MPG.
The car still had the drum brakes on the front with the Corvette discs on the rear. Really needed the front brakes changed to discs.

Highway driving is easier to increase if that's where you spend major of time clock at lot of miles a year gearing lockup OD etc... could be worth while improvements, intown is a different story unless it's little encono box most cars i've driven gets mpg in the teens my Avenger RT gets 19-22 mpg probably one of the better fuel mileage cars I've had.

 

[273]

Show me an instance where a larger engine gets better mpg for a road going vehicle.

Larger engines create excess power which is a waste in every regime except acceleration and ascent. Longer strokes, bigger bores, and large cam profiles all waste energy in order to gain power outside of the cruise regime, but average mpg is dominated by cruise.

When cruise mpg is the goal, minimizing ci is the lowest hanging fruit.

OP says he wants to tow - but does tow mpg matter as much as unladen? Without those details it's impossible to figure out which end of the displacement spectrum to be on. Knowing a max grade, weight, and operating elevation would make figuring out the minimum requirements a lot easier.

Also, typically a smaller engine with a turbo will out power and out mpg the larger na engine in almost every case. It can maximize torque when needed and use fuel sparingly when it's not. It's no secret why oems have had a love affair with boost in ecino cars for some decades.

The smaller engine usually does get better but generally by a mpg or two intown maybe slightly more on highway, if you bring the smaller engines NA power to that of the larger engine bet mileage would be more similar. i always thought mpg is how efficient the engine is a part throttle to make the required HP needed at that moment to maintain speed aka not very much and smaller engine is generally slightly more efficient at doing so. But less effective to make larger power in the few moments it's required.

I always found peppier cars generally better in fuel mileage cause I'd tend to drive easier with them.

 

[Bewy]

A smaller capacity engine will always get better mileage than a bigger capacity engine. Nope, & I stated this very early in this thread. There are many variables that have to be considered.

 

[Ottmundr]

Have you considered the 3.6 pentastar? Pick-n-pull maybe? The more I learn about it the more I like it.

 

[Dale Davies]

Have you considered the 3.6 pentastar? Pick-n-pull maybe? The more I learn about it the more I like it.

Personnally I am not a fan of the Pentaturd. Took one look when they first came out and I was a mechanic at a Dodge Jeep dealer, and decided I did not like it. Your results may differ, and that is OK. The old faithful 318/360 are readily available, so they are relatively inexpensive. Real easy to work on, while the Pentaturd with its DOHC and VVT can be a nightmare. The wiring would be a PITA.

 

[mgoblue9798]

Have you considered the 3.6 pentastar? Pick-n-pull maybe? The more I learn about it the more I like it.

I have that engine in my 300 and combined with the 8spd I love it. Don't know that it would be up to towing duty though.

I have thought that the 3.6 8spd combo in an A body should be capable of knocking down 30mpg though.