15.0 mpg to 21.6 mpg!

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A 30 or 40 mile run really is nothing. You need to put at least 250 miles on it before filling. I can take my '03 mini van and go on a flat road 25 miles at 55 mph and get almost 27 mpg. If I average it for a whole tank on the road, I'm lucky to get 23 mpg.
 
318willrun said:
A 30 or 40 mile run really is nothing. You need to put at least 250 miles on it before filling.
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You guys are misunderstanding the point. I'm not using 21.6 mpg, and not using my "mpg test route" as a measurement of "real world" mpg. I've already stated as such (see post #6). I don't expect to go ride around town and get 21.6 mpg. I never said such a thing.

My "mpg test route" ... IS A METRIC! In order to make an apples-to-apples comparison of my set-up before and after changes. 250 miles of varying traffic conditions from one day to the next, combined with varying weather conditions (from one "test" to another) would measure real world conditions sure enough. It would not provide me with a quick/easy/accurate/relevant measurement from one jetting change to the next. 250 miles would take hours / days to complete. I want more quick and direct data bringing to light what my jetting change is doing (outside of what I observe on the AFR gauge). My "mpg test route" takes about an hour to get a reasonable metric.

And 21.6 mpg let's me know that the 1405 is doing a much better job at atomizing fuel (cruising along) than the 1407 was. Most of the time it is running about 14.7 AFR on my current set-up. I'm going to get my POWER mode AFR richer, but I think I can hit 22 mpg once I get my CRUISE AFR to ~15.5.

7milesout
 
And I'm saying you could loose a 1/4 gallon at the pump from one fill up to the next, and in that short of distance it would bump the mpg up 3 or 4. Unless you ran your fuel line to a 2 gallon can that you can see exactly when it's full from on trip vs the other trip, then a 30 trip is almost worthless. How do you know the nozzle clicked at the exact same amount of fuel? Even if you clicked it till it came out, you could still vary from fill up to fill up, and that's huge on a 30 mile trip. That's why I said at least 250 miles so that 1/4 to 1/3 gallon from tank to tank won't have near the impact and will get you very close. That's why Rustyratrod said a few tanks for more accuracy.
Nobody is saying you didn't gain mpg, just saying a 30 mile trip is dust in the wind
 
Overall, I think the work is sound, the scientific method is in full effect, the statistical analysis just needs a few more data points.
Would be a shame to waste such good effort on a change in density due to fuel temperature or atmospheric conditions (so more trips certainly wouldn't hurt), but the OP is definitely putting in more effort than most when it comes to tuning, and the results are definitely in the right direction.

Don't beat the guy up because one data point MIGHT be an outlier.
 
I fill it till it clicks. Then I continue s l o w l y until I see it backflow up the filler neck. As consistent as I can fill it. I'm probably going to ruin the vapor return components and charcoal canister too, right?
 
Its a reasonably metric for comparison. Far better than what most people do.

I don't think my engine would idle AT ALL at 14.7 AFR. And when I ignore that AFR gauge and set idle based on the Edelbrock manual, I wind up in the 13.0 range anyway.
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Yup. What your engine wants is basically what should be expected. The only part of Edelbrock's diagram that appears to be a simplification is using rpm instead of load. Its actually easier for most of us when given in rpm although there are some high load, mid and low rpm situations; mre so with trucks than hot rods.

As far as this goes
... Guess the Big 3 have been doing it wrong for the last 100 yrs.
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it is based on an incorrect assumption. Running over 14:1 AFR at idle is a relatively recent phenomenon and is not naturally what most engines like best. It works with higher idle speed, timing to match, and in concert with the catalytic converter to reduce emmissions in several areas at once. Some observations on this here Heat riser affect wideband? - Page 2 - racingfuelsystems.myfunforum.org

The attached is from "Walter B. Larew, “Carburetors and Carburetion” At the time he wrote his book on carburetors he was a retired Brigadier General who taught Military Science at Cornell, among his other accomplishments. He published this carb book in 1967." (This was originally posted on the racingfuelsystems forum but that's undergoing some changes so isnt visible there at the moment.) Desired Carburetor AFR Characteristics At Different % Load - racingfuelsystems.myfunforum.org
The mixture ratio "F" is shown in terms of Fuel to Air.
----
0.0833:1 Fuel to Air = 12:1 AFR
0.077:1 Fuel to air = 13:1 AFR
0.0714:1 Fuel to air = 14:1 AFR

High OL VT AFR.jpg
 
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mattax - Thanks for the info. Maybe I should have title the thread differently and added a list of disclaimers to the first post. But I'm not on the NY Times best seller list, so writing clearly is not my strong point. To put it as clearly as I can, finding a means to achieve maximum mpg (whether realistic or not) provides me with a data point. That data point provides me with feedback at least on how well my carb and set-up is atomizing fuel. And provides me with "better" or "worse" than before. I was surprised to see that number. I've triple checked my numbers, and considered what I may have done to skew the results. Nothing.

Other feedback is gleaned from the AFR gauge, crankability, buttometer, tank range, etc. I'm not trying to create a 72 Scamp with an LA 360 to be a hyper-miling commuter. What I want is to be able to crank it and run down the road with a feeling that it won't carburet any better, I'm wasting nor more fuel than I can help, and the engine is not being damaged due to poor carburetion / timing / etc. I'm getting there. Drawings for my 7930's should be done today.

And - when I was given this car, it was a slow-dawg. It took nearly a whole battery, and a gallon of fuel to crank (from cold). I took it to the drag strip under those conditions and took data there also. There was a ~55 Chevy, (Bel-Air looking) car there. It was dragster loud, and had big fat tires. It looked ominous, and sounded mean. It was the first car I lined up with. I cut a .134 light (hadn't been on the strip in YEARS), and he cut a .135. But from the mash of the peddle, he blew me away. Yet he ran a 14.2. That solidified my quest for a 13.99 second ET.

Now my Scamp sounds much better (new exhaust from header to tailpipe), runs so much better, and fully functioning brakes. I have yet to do tires and a rear diff (just say NO to open diffs). But if my Scamp can drive to the track, and beat that car, while on 14" 215/60's ... I will have a grin from EAR TO EAR. At that point I think I will drive and enjoy, and concern myself with the aesthetics, and show car type details.

I appreciate you guys who give me motivation and help. For those who are nitpicking, I don't think bad of you. I think you misunderstand my point ... because I'm not effective on making my point clear. I love Mopar's and I am absolutely enjoying dialing this car in. It's a great car. Had a youngster drive by yesterday giving me a big thumbs up out his car window (I don't expect young kids to like this car, but I've been surprised how many actually do). I had 2 different guys in 1 day (a month or so ago) ask me if I were willing to sell it. It is a phenomenal vehicle, and all I want to do is make it better.

20170827_142043.jpg



7milesout
 
7milesout said:
And - when I was given this car, it was a slow-dawg. It took nearly a whole battery, and a gallon of fuel to crank (from cold). I took it to the drag strip under those conditions and took data there also. There was a ~55 Chevy, (Bel-Air looking) car there. It was dragster loud, and had big fat tires. It looked ominous, and sounded mean. It was the first car I lined up with. I cut a .134 light (hadn't been on the strip in YEARS), and he cut a .135. But from the mash of the peddle, he blew me away. Yet he ran a 14.2. That solidified my quest for a 13.99 second ET.

Now my Scamp sounds much better (new exhaust from header to tailpipe), runs so much better, and fully functioning brakes. I have yet to do tires and a rear diff (just say NO to open diffs). But if my Scamp can drive to the track, and beat that car, while on 14" 215/60's ... I will have a grin from EAR TO EAR. At that point I think I will drive and enjoy, and concern myself with the aesthetics, and show car type details.

I appreciate you guys who give me motivation and help. For those who are nitpicking, I don't think bad of you. I think you misunderstand my point ... because I'm not effective on making my point clear. I love Mopar's and I am absolutely enjoying dialing this car in. It's a great car. Had a youngster drive by yesterday giving me a big thumbs up out his car window (I don't expect young kids to like this car, but I've been surprised how many actually do). I had 2 different guys in 1 day (a month or so ago) ask me if I were willing to sell it. It is a phenomenal vehicle, and all I want to do is make it better.

View attachment 1715095203


7milesout
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I forget what you have for a motor/exhaust/gears. I think it was a 360? Anyways, if it's a 360, you'll have no problems getting into the 13's, even if it has 2-something for gears.
 
360 / 727 / TTi headers, X-Pipe, Borla Pro-XS (str8 thru) / 3.55 open diff. Will be procuring an Eaton True-Trac after tires. But I can't decide whether to stay with the 3.55 or go smaller (in the direction of a 3.23 or beyond).
 
IMO the title is OK. Its an attention getting headline and this forum is a part of the new media anything. I've seen and heard much worse leads, and don't mean the NY Post alien baby stories. :razz:

You'll know its cruising too lean when the engine starts surging. Also you'll have to find by experimentation when the cruising is more on the main circuit than the idle. Don't be surprised if its above 50 mph. For reference, on my setup with Holleys its been above 60 mph. The Carter/Eddy may be lower.

As far as this being better than the Eddy 750 goes, that's not surprising based on what Tuner and others have observed. There's been some manufacturing differences from the Carters that can create some odd fueling. This one always stuck in my head.
The 1407 750 CFM uses the same casting for the primary cluster as the 625 CFM carbs in spite of the fact the venturi minor diameter is 5/16” or so lower in the 750 body. This places the exit of the booster venturi that much above the “vena contracta” in the air flow, the result is the “booster signal” is not obtained in the correct location and the metering is erratic, the A/F wanders rich and lean as load and RPM vary as the throttle position is changed.
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Of course it can be fixed as can all the other anomolies. Its just not what most of us expected when we first went out and bought an aftermarket carb.
:lol:
More from where that quote came from in the first two pages here
Edelbrock 1407 - Speed Talk
 
7milesout said:
360 / 727 / TTi headers, X-Pipe, Borla Pro-XS (str8 thru) / 3.55 open diff. Will be procuring an Eaton True-Trac after tires. But I can't decide whether to stay with the 3.55 or go smaller (in the direction of a 3.23 or beyond).
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With that combo, 13's is a sleep walk (providing you hook up). 12's if it has around a .470 lift cam and something for an aftermarket converter.
 
318willrun said:
With that combo, 13's is a sleep walk (providing you hook up).
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I hope. And with pizza cutter 215's, the open diff has got to go. A TrueTrac is what I will go back with. Maybe $150 more than other posi type diff's, but I think it will be worth the premium. At this time, I think I'm going to stick with a 3.55 gear. That should put me about 4,800 - 4,900 rpm crossing the quarter mile line. Since it's not an interstate queen, I'll deal with it on the few occasions I take to the super slab.
 
very nice ride.
I hope you are not using that open element. If so your tune is for 100+ underhood air. A cold air intake system via sealed hood scoop or hose setup is a must IMO.
 
mderoy - It's open, like you see. I'm not planning to change the hood, maybe ever. Do you have any links to a hose setup? It's something I would consider. Seems to run just fine how it is though. Thanks for mentioning it ... that's something that has never crossed my mind.
 
Shawn's Dart 3.jpg
You can use DIY cowl induction. Also try one of the smaller Thermoquads. small primaries with large secondaries. Best of both worlds. mileage and performance.
 
spl440 said:
View attachment 1715095631You can use DIY cowl induction. Also try one of the smaller Thermoquads. small primaries with large secondaries. Best of both worlds. mileage and performance.
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What kind of numbers? My 273 4 speed gets right at 20 hwy. if I drive it like a grandpa. I have a o/d 833 that could improve things.
 
toolmanmike said:
What kind of numbers? My 273 4 speed gets right at 20 hwy. if I drive it like a grandpa. I have a o/d 833 that could improve things.
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It is actually a built 360. The car has no stripes,mags or scoops. Looks like a grandpa's car. 360, 4 speed and a 460 lift cam and 222 duration a .050. 3.23 with 26 inch tire and sure grip. still needs more tire. at about 70 mph at about 3200 rpm getting 16 mpg. around town less, only because my foot is in it all the time.:rolleyes: And a/c blowing cold.
 
RPM@ 60 mph should be 2000 or less. All the late model o/d cars get the best mileage there. Kinda doggin' a HP engine but that cam in a 360 is pretty mild. 16 isn't bad. Closer to 20 I bet with a o/d.
 
spl440 said:
agree with an O/D, but do not like the factory O/D gear split. thinking of the Passon hemi O/D.
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Kind of crazy, 273's aren't supposed to be torquey but I can accelerate through the gears normally and skip 2nd. and go from 1st. to 3rd. or skip 3rd. and go from 2nd. to 4th. without issues. The 833 od. is basically a 3 speed with 4th. as a o/d. I wouldn't see much difference. 1966 833's do have a lower 1st. gear ratio. Maybe that helps.
 
7milesout.
If you want some thoughts on your other goal, ET under 14.2.

I'm running about 15.7 AFR accelerating, and 14.7 AFR cruising.
At part throttle, the 15.7 may be OK. Just to review, the engine should go leaner and leaner as the load increases (part throttle acceleration). Somewhere over 60% throttle, it will need to start going richer or it will not continue to accelerate. It may be 70%, 80% or 90% depending on the engine. By 100 % it should be in the range of 12.5-13.2 AFR.

I'm going to move the step higher on the rod so the acceleration richening comes on sooner. I'm hoping this will eliminate the 1.5 second lean spike. (1.5 seconds after pulling away from a dead stop).
Is the lean spike accompanied by a flat spot in acceleration? If there's a flat spot and the idle system has enough fuel flowing (no hesitation with gentle acceleration), then its the accelerator pump that needs adjusting.

My current setting only runs about 12.7 AFR at WOT, and I want to bring it to 12.2.
Its worth an experiment but that would be pretty rich IMO.
Have you been through Edlebrock's charts showing the effect of rod/jet combos ?
They're in the back of some of their Carb guides that are downloadable pdf
 
mattax,

The below table comes right out of the Edelbrock carb manual. I look at that manual daily. I'm an engineer and have had to write some similar manual type info. And it's not easy to write that kind of stuff and be clear. The Edelbrock manual is very well written. I've gone further and created my own Microsoft excel carburetion tables. Which made it clear to me that I was stuck too lean on POWER, and too rich on CRUISE. Actually, I could stay where I am on cruise. But to be safe, I want to richen up the POWER. Based on my tables, and understanding how the metering rods work with the jets, I have designed my own metering rods. I'm working that out as I type.

And yes, my 1.5 second lean spike has a dead spot feel to it. It feels EXACTLY like it's running out of gas. And ... it is. I've adjusted the pump. Doesn't matter the setting, it's still there. Because when a driver lightly pushes the pedal, and holds it there, to gently accelerate, the engine consumes the limited amount of the shot. Unless your foot keeps pushing down, and manually activating the pump, the pump shot stops. It needs that pump shot spread out more, under light acceleration. When I slam the throttle down, it responds very nice, no hesitation, no dead spot, just spinning tire(s). Based on that, I'm not going to try to mess with the pump shot. My goal is 13.99, not to turn my Scamp into a Camry! :D

But what I'm doing to address the 1.5 second lean spot is, my metering rod blends the POWER portion up into the CRUISE section. And I'm running the biggest springs. My hope is that the biggest springs push the rods up enough when vacuum is first reduced (pushing the throttle from a dead stop) enough to get into the my more aggressive blend. I'd run a bigger spring if I had it, because while cruising, my engine seems to make enough vacuum to hold that rod down in the jet. A bigger spring may be the next thing I experiment with.

The below WOT numbers, I can't remember where that came from. But as my engine was approaching 12.2, I could feel it pulling harder. Could be that the rpms were coming up and just generating more power, but I don't think so. I had not felt that increase feel of power except when it was moving from 12.7 or so to right at 12.2. It did feel strong. And that AFR is safe, so I'll tune for that again.

7milesout

7milesout said:
I don't think my engine would idle AT ALL at 14.7 AFR. And when I ignore that AFR gauge and set idle based on the Edelbrock manual, I wind up in the 13.0 range anyway.

WOT
12.8:1 - Lean best torque
12.2:1 - Mean best torque
11.76:1 - Rich best torque
11.01:1 - Fastest flame speed in cylinder

Right out of the Edelbrock carb manual below. The table below compared with the numbers above is what I'm shooting for.

View attachment 1715094711
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JMO

Don't tune to a number, tune for performance/mileage. That 12.2 number is only a suggested point and will vary greatly depending on engine, fuel, load and other factors.

For WOT, take it to a track and tune it for best MPH. That is where the engine is happiest at WOT. If it happens to be 12.2, OK. Likely won't be 12.2.
 
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