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Discussion Starter #1
I just picked up a 2002 2500hd w/ the 8.1, Allison combo, to tow my Cummins around :D. I was wondering what you guys are doing to boost the power, are the custom programs worth it, what about intake or exhaust? The thing has decent power, but Im use to driving 600hp Cummins so this is a little on the slow side.

And does anybody get over 13-14mpg, w/ the Allison Tranny? From searching, I know Ramv does, but he's got that light duty tranny. :flipoff2:
 

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Id tow the 8.1 with the cummins....:D

Opening up the exhuast helps a bunch on 8.1. As far as tuners/Mpg increase well im stepping aside pissing wars about to begin. :D
 

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Holy Beaten dead horses.

1. Exhaust
2. Good Quality intake
3. Tune

A tune net's some large gains even on 87 fuel with that beast. The trick is Torque Management as the Allison does a lot of it so your limited on shift speed and quality. I'd be willing to bet on a 8.1 you would see a 2 mpg improvement in a good custom tune (LS1 Edit, HP tuners). The canned tunes (order the PCM over the internet) aren't bad but the leave a lot of power on the table.

If you want to go all out you can always get some good heads (HUGE HP gains) and be about the same on fuel consumption.
 

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I've got the Dodge V10, good friend of mine has an 01 Chebby with the 8.1.....we were talking about mileage the other night and how much is sucks....I asked him what mileage he got in town:

9.7

How about on the freeway?

9.7

Towing?

9.7

:D

With some mods, you might get 12mpg on the highway.....if you find something cheap that gets you there, post up.....I have given up on MPG, I get 10 regardless and refuse to put any money in the truck....
 

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Do a 180 deg thermostat. Mine stopped burning oil when I did, and it gives it more timing when towing since the ecu starts pulling timing around 210 i think.

Oh and for the record, I am in the 13-14 range. I have got better tanks but its all back highway cool days, at like 65 mph. If i bump to 85 mph I am 12-13 range.

Towing i can get 5 mpg (12 000 lb at 80+ mph in 100 deg heat with head wind) but normally get 7-8 with 10-13 000 lb in the mtns. I have seen 9-10 with the 10 000 lb trailer if i stay at 65 or so or away from the big hills.

Diesel Place has a good gasser section.

Black Bear tune is supposed to be good, also, some free flow mufflers. Raylar likes the SW headers but not sure I would put the $$ or effort into it.

Best bang for the buck is a Raylar cam and valve train (or CC valve train) for $750 + install + custom tune. Should be 425hp+ (450 I think is what Ray figured with exhaust mods) at the crank.

There is a guy out in your neck of the woods (20052500HD I think or something on Dieselplace) who has done a few cam installs and tunes including the Allison, with good results.
 

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I recently put a nice comp cam in my 8.1 and have driven it for about 100 miles so far. the power gains is nuts.

Tune, intake, exhaust. If you can spring for it, go LTs. stock manifolds are kinda junky. The stock exhaust tubing is also WAY too big and runs duals way too far back. Bein these motors dont make much power above 5k, run 2.5 from manifolds to a y pipe, 3" single after...Going to a corsa catback (and keeping catforward stock...) i gained tons of power, but ive yet to get around to redoing manifolds to muffler tubing. soon enough...

Intake tube sucks. atleast replace that. the spectre kits for the SBC will work, just takes a lil adjustment and is like 100-125 shipped. I still can't justify 300+ for a k&n.

Justin at blackbear knows these motors pretty well from what ive gathered talking to him. he helped me some with my tune when i was writing it. they are VERY responsive to tunes, just like all the other newer GM trucks. My old motor didn't take much additional timing, but the new one seems to like it. Remove as much tqm as you like, and remove some of the tqm at shifts if you want. I had all mine pulled for a while and it would chirp at a prepped track going into 2nd every time. haha.

if you wanna get into the motor, a new cam will help out tons. mines 218/224 .510/.510 114 lsa. Biggest off the shelf cam for comp camps. currently its idled at 525 rpm and doesn't stumble. you can barely hear that its got a cam in the exhaust. Theres so much motor there that what would be a "moderate" sized cam on a small block is a small cam in these motors. Ive yet to do rockers, but they will help out a good bit im sure up top. Ill hold off till i find a deal since they dont make much difference in normal city/highway driving.

If the typical bolt on + cam/valvetrain doesn't cut it, theres either forced induction or raylar intake/heads. thats just too much money for my blood and the power im making now is awesome. im really expecting a low 14 sec pass on stock sized tires this spring in the 1/4 from a 6500 lb truck dry...
 

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Discussion Starter #9
RamV I just searched those sites, good info. Thanks.
 
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