20.5 mpg Dodge RAM ABA testing run

[ECONORAM]

Okay, I finally got out and did some ABA testing. I have gone back and forth between happy and sad with my results. At first I thought 20.5 averaged (at 65 mph, 70*, no a/c) from 4 runs (2 each way, and the hi and low thrown out) was good. Then I realized I am running a 91 octane performance tune which gives me about 1.5 mpg. So I initially thought all my aero panel work was in vain. Later I realized my tests were done with a tankful of E10, which drops my economy about 10%. Considering the truck's EPA numbers are 14/17, it looks like I am making headway.

Mods thus far: clutch fan delete (replaced with Efan), exhaust Ypipe replaced w/Flowmaster unit, exhaust manifolds insulation wrapped, Trueflow intake air filter, Superchips 91 tune, Mobil1 5W-30 oil, AMSOIL ATF, full wheel covers on factory 20" wheels, 50% belly panel kit, LEER topper.

I do not have a super flat area for testing; rather a pretty flat 3 mile stretch (with gentle grades) on I-44. Each end has a slight uphill, so numbers could probably be a teeny bit better. With such a short stretch, I decided to change my usec/gal setting to a little less than half the normal value (004486 vs 009486) to get bigger readings for fuel consumption. (only adjusting one digit made it easier to restore once testing was done) I used ratios to convert it back to real fuel use. I tried this after doing a couple test runs before where I could see little difference (if any) either direction at the normal setting.

I hope to test again this week or next with my HO cams installed, and then with a muffler delete. True, the cams test won't be ABA, as I don't want to reinstall the OEM cams--that was a lot of work!

[deathtrain]

i would not touch the cam. you might disable the MDS plus you need to have someone that really knows the 3rd gen hemi tuning. I know alot about these motors I have the 07 charger. same motor. a guy that is real good and backs up his tunes is LXmod guy out of dallas. if you run the idea of MPG tunes i beat he will be up to it.

[Blu3Z3rg]

Do you have the 4.7?
I have a quad cab 4x4 4.7 dakota myself
I have gotten 20+ straight up highway, but my average is just over 16.
I'm wondering how much a PITA the y-pipe was for you, and was it effective?
I just did a Y-pipe back exhaust of 2.5" and am hoping that it helps move that 5000 lbs around a bit easier.

Also, do you think you gained a good bit from the E-fan? which one did you use?
Stock dakota is 15 ave mpg, and I'm getting 16+ with my few mods. Hoping for more, but not getting it yet.
gl and gj!

[brucepick]

Good on all the work you've done so far. With EPA Highway of 17 and you're getting 20.5 approx, that's a really good improvement - more than 20% above EPA already.


I think aero mods are definitely going to help you. I'm guessing that in Texas you do lots of highway miles, 60 mph and above. I got a lot of benefit from my belly pan on the Civic, and most of that benefit seemed to come from the front section between bumper and firewall. The planned wheel covers are a good idea.

Think about a tapered cap, one that gets shorter at the rear. I saw some discussions and pics of those in the Aerodynamics subforum. Should be pretty easy to build one that actually helps your aerodynamics. If you want to make it look cool or macho, you'll need to tackle that separately.

Oh yeah - tires. If yours are knobby off road capable ones, consider tires with a smoother highway tread. And in any case, air them up to the max imprinted on the sidewall. And check pressure often.

Mostly we find that better flowing intake and exhaust don't help fuel economy a whole lot. They improve the max power output you can achieve, if the original provided some restriction. Remember, you're likely only using a tiny percentage of the engine's available power. At the low throttle levels used in hypermiling, the amounts of air in and exhaust out are far below the capacity of even a bone stock system - in my humble opinion, of course. Three inch pipes can help at wide open throttle at max rpm. You're likely at 1/3 throttle and 1/3 max rpm most of the time, so 1/3 * 1/3 = 1/9 of max/max air and gas flow. Am I close in my guess?

[mcrews]

good job!!!
trucks are tuogh.
Think about going up a size on the tires (ex 245 to 255) when you go to buy them again. as brucepick said, it's about lowering the rpm on the road

[Frank Lee]

Lowering the rpm via bigger tires on the F150- even only one puny size up- did not help fe in the least.

[mcrews]

Originally Posted by Frank Lee

Lowering the rpm via bigger tires on the F150- even only one puny size up- did not help fe in the least.

could be the difference isn't negligable???


ANd back to the poster.........tell me again why you wont aba the cam??? ?

[Frank Lee]

I had tried an even bigger oversize and fe went down with that too.

Big Dave reports similar results.

The piston speed on my F150 at 55 mph is well below the 1000-1200 that is generally considered optimal for fe. It is right on the threshold for downshifting all the time, even empty, so I guess it's quite possible that trucks with ODs are already lugging?

[mcrews]

oh that makes perfect sense!

I should have stated that. I was assuming he was at bone stock size.
absolutely you can get past the uptimum rpm, especially on a truck.

[Frank Lee]

Probably a YMMV thing. My F150 has the tallest axles available; shorter ones might respond differently.

I'm of the opinion that older trucks- say, '70s without deep ODs- should benefit from oversized tires. I know they rev quite high.