Ramcharger exhaust 2-1/4 duals or single 3"

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gliderider06

gliderider06

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My stock 87 Ramcharger 318/4bbl with manifolds. Currently has 2-1/4 duals from the manifolds, 2 cats and turbo muffs that exit behind rear wheels. I am in a quest for the best fuel mileage out of a non OD and carbureted beast. I play around and have done great with it so far. 13.5ish mpg. If I recall when I put the duals on it I actually lost some mpg in doing so.
My thoughts today are if I put a y pipe in behind the cats and run a single 3" back. I'm thinking that if I do so , I could possibly increase some backpressure and maybe some torque and gain some mileage. A single 3" should still flow well enough for a stock 318 and not be too restrictive.
Thoughts?
 
Did you do any carb tuning after the dual exhaust? Do you have a wide band O2?

When you compared mileage, was the pre-dual exhaust from the summer and the dual done during the winter? What I'm getting at is they change the fuel composition fro winter time, and its different that summer fuel and in the testing we conducted the winter fuel gets worse mileage in an apple for apples testing environment over summer fuel. Your regional seasonal change will dictate when that happens. Also, the weather alone will change your mileage, wind, puddles, snow, mud etc will effect your mileage if your conducting testing on the same road.
 
your bottleneck for efficiency is always at the manifolds and then where the Y hits the single cat. If you can open that up, that's where it will make the biggest difference. Whether you go 3" or duals after the single cat, really only is a visual and slightly different sound.
 
Ccas said:
your bottleneck for efficiency is always at the manifolds and then where the Y hits the single cat. If you can open that up, that's where it will make the biggest difference. Whether you go 3" or duals after the single cat, really only is a visual and slightly different sound.
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It has true duals on it now and has been on for almost 5 years now. I would go From the 2 cats into the single 3" back from there. I don't need to do anything, but if I could gain something I might try it.
Thanks
 
dano said:
Did you do any carb tuning after the dual exhaust? Do you have a wide band O2?

When you compared mileage, was the pre-dual exhaust from the summer and the dual done during the winter? What I'm getting at is they change the fuel composition fro winter time, and its different that summer fuel and in the testing we conducted the winter fuel gets worse mileage in an apple for apples testing environment over summer fuel. Your regional seasonal change will dictate when that happens. Also, the weather alone will change your mileage, wind, puddles, snow, mud etc will effect your mileage if your conducting testing on the same road.
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I put the exhaust on almost 5 years ago. I brought it from 9ish mpg to over 13. I drive the same roads to/from work in the truck and generally fill up at the same station to keep my variables the same as possible. My biggest improvement was putting a fresh rebuilt 318 in it last spring.
Thank you
 
I would think the 2 cats would represent the greatest restriction to create back pressure. How many cell are they? Most emission replacement are 600 cell. Switching to 3" post cat probably won't do anything. I think a wide band and tune on the carb would be the next move I would make if this mine to champion. Going from 9 to 13 is commendable but to a point the weight, aerodynamics and efficiency of the trans, transfer case (?), front and rear end become a power absorber.
 
gliderider06 said:
It has true duals on it now and has been on for almost 5 years now. I would go From the 2 cats into the single 3" back from there. I don't need to do anything, but if I could gain something I might try it.
Thanks
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ok, got it. I don't think leaving the dual cats and going back to a single Y and 3" tailpipe will affect your mileage nor performance. However, if those downpipes and Y are not mandrel bent, that could make a a difference. The whole idea of performance and efficiency is to get the exhaust gases away from the heads as quick as possible. Mandel bends, headers, Crossover etc up in the front of the system all have the biggest effect. As you get further back, it's much less important unless you really restrict the back.
 
Just as an example and not a direct apple to apple comparison.... on my old ‘79 Magnum, fully loaded minus the moon roof w/a 360/904/8-1/4 w/2.76 gears on 26 inch tires weighing in at 3800 with very little fuel.....

I added/changed some parts to the 360. The stock cam remained but swapped on a factory iron intake and a 600 Edelbrock. The exhaust off of the manifolds was at 2-1/4 with an H pipe before the twin high flow cats which were legally needed at the time into turbo mufflers to the bumper.

All in all it was a nice but modest gain. The engine was Chrome box triggered at first but then switched out for a MSD 6A. After much attention was applied to tweaking the best I could get out of it mileage wise (the primary side of the carb of course) I managed the best of 20, though 19 was most consistent. The MSD was responsible for some of that mileage. Approximately 2+ mpg were found after more tuning.

It did pass emission testing very well. The testers were even a bit confused and hesitant to let it go out the door asking a bunch of questions and wondering why it was passing as almost a brand new car.

Now I do realize that there is a bit of a weight difference as well as a aerodynamic difference in a big way, but as I said, just as an example..... tune away! Keep on it. Finding what your looking for can only so good but get it as good as you can.
 
Just run open headers. Screw um all.
 
In my way of thought, necessary backpressure is a myth. Making the engine pump exhaust out with the pistons against a restriction just wastes power that could be used elsewhere. I know my car runs better with open headers than through 2-1/2 inch duals. 1-1/2 tube X 2-1/2 inch collector headers or magnum manifolds (Magnums for automatic or hydraulic clutch application) would be a good move. Are you having to pass sniffer test on emissions? Have you put manual hubs in place of the outer couplers so you can fully disconnect the front axle instead of just the left side via the CAD (centrally activated disconnect)? You can lock still your hubs manually and use the 4WD on demand as needed, but not have to run the right side axle and spider gears all the time when you don't plan on using 4WD. If you could get by with a high flow converter, I'd look at running a single 3-1/2 system.
 
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So, I do have to pass the sniffer test in Delaware. Last inspection I failed the emissions test with a 601ppm HC ( needing <600) I kept trying, but without cats, they refused to pass me. I got a pair off Ebay, welded them in and passed emissions. This was with a worn out 318 and the original carb that was untunable. It now has a fresh stock 89, roller cammed 318, cast spreadbore intake and a eddy 1406, HEI ignition, and the exhaust as mentioned. The 1406 has gotten me the best mileage (and drivability) so far. I tried 2 different spreadbore Holleys, a square bore and a thermoquad. I still have a factory quadrajet to still try. The eddy has been good. I make a change and run 2 tanks of fuel to see the results. I use the same gas station and my route to and from work is unchanged.
I never thought of the front hubs at all. I thought that they were disengaged when in 2wd. I will look into the manual hubs especially if it will give me an advantage of mpg and I rarely use 4wd in Delaware. It will be easy enough to turn the hubs before pulling out of the garage if it ever snows here.
Thanks everyone!
 
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Move to a location that doesn't require inspections. Over and done.
 
Garrett Ellison said:
In my way of thought, necessary backpressure is a myth. Making the engine pump exhaust out with the pistons against a restriction just wastes power that could be used elsewhere. I know my car runs better with open headers than through 2-1/2 inch duals. 1-1/2 tube X 2-1/2 inch collector headers or magnum manifolds (Magnums for automatic or hydraulic clutch application) would be a good move. Are you having to pass sniffer test on emissions? Have you put manual hubs in place of the outer couplers so you can fully disconnect the front axle instead of just the left side via the CAD (centrally activated disconnect)? You can lock still your hubs manually and use the 4WD on demand as needed, but not have to run the right side axle and spider gears all the time when you don't plan on using 4WD. If you could get by with a high flow converter, I'd look at running a single 3-1/2 system.
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^^^^^^^^^^^^^this and remove the cats ---------jmo
 
I had a 84 ram charger 4x4. 318 2 barrel. Single exhaust. Best mileage was 14 mpg. Put on dual exhaust with a H pipe then it improved to 18 mpg. Put on manual hubs then 19 mpg. I put in a mileage plus torque converter then hit the magic 20 mpg. Kim
 
I prefer a good HP single exhaust for a small cube engine like a slant or 273 or 318. Such as a good mandrel bent Y pipe off the mannyfolds into one of those Flowmaster Ys and out with a 3" single. Just one peon's opinion.
 
You should be getting at least 18 MPG out of that. Your Quadrajet with lowered float height lowered to smog 318 settings will help a lot. If you were able to nearly pass emissions without a pair of cat's, a single high flow cat should get you into compliance easily. It takes a 3.25 inch pipe to equal the end surface area of two 2-1/4 inch pipes, so go 3-1/2 with something like this "neighborhood friendly"
Jones Exhaust F626-7D Jones Exhaust Full Boar Full Flow Truck Series Mufflers | Summit Racing
Or if you can stand the drone
Cherry Bomb 87527CB Cherry Bomb Glasspack Mufflers | Summit Racing
 
Thanks for that Garrett! I just put two of those Jones in my cart. Ive been looking at Jones mufflers for a while, didnt know they made a 3 1/2 in/out.
 
I thought I’d share another hack we use on our 4x4s involving the front axle. Being that it’s only being used when we are in low enough traction to actually need it, we usually either run a mini spool or Lincoln Locker in the front diff. The vacuum actuator ( we swap to aftermarket cable actuators for reliability) on the CAD provides open differential when the hubs are locked. But when you actually need four wheel drive, that locked front axle will pull you places you that make everybody wonder what makes your rig work so well. And for a whole lot less than putting a locking differential in.
 
I have put a few hundred thousand miles on 2wd Ramchargers and have only ever seen regular 18-19mpg highway on my 92 5.2 magnum. For those that are unaware, that is 600miles+ per 35gal tank! If someone is doing that on a tall 4wd, I'm skeptical, but bravo!

For reference, going from the the stock exhaust on my 90 5.9 tbi to 1 5/8 headers and 2.5" duals w\ welded ultraflows with turn downs (no over axle) was worth a bit more than 2MPG. ROI was noticed immediately. Other things i did for MPG was thinner diff fluids (e.g. synthetic and not the 140wt), elec fan on my 93 (magnum viscosity fans sound like planes taking off), 1-2deg more timing (on EFI distributors you can only set initial). Some sort of multi-spark ignition box helped a bit too though i honestly don't recall how much.

before do *anything* that costs with the exhaust, i would try a test to see what there *is* possible to be gained. e.g. no cats, turn down after muffler. If its not immediately noticed ROI, i put it back together as it was and spend cash saved on more gas or towards buying something thats not a 4wd truck.
 
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