8.1Gasser help.

[8.1GASSER]

Well guys, after a few months of not being around I have joined again, if anyone has any questions relating to the 8.1 I'm here to help, I have many mods done to my truck and know the in's and out's of these trucks, so go ahead and post, we need to get this forum going before we lose it.
http://images.cardomain.com/member_img_a/374000-374999/374975_13.jpg

[GMC-2002-Dmax]

Nice Looking Truck :D

GMC ;)

[tswartos]

could u give a run down of mpg u get?

ive heard good things about the 8.1 in a bigger chassis and wonder how it is in the pickup.

[8.1GASSER]

Tim, a quick rundown on my mpg, some others will vary, On the highway with nothing in tow truck gets anywheres from 12 to 14 mpg. In town is a solid 10mpg. When towing 5k at 70-75mph I get around 10mpg. Now remember that I have larger than stock tires and the gear reduction associated with them has helped my mileage when empty, and will hurt it for around town driving. Hope this helps.

[biker Wayne]

Since you asked if anyone has any questions about the 8.1, I some questions. I drive a Dmax/Alli, but a friend has an 8.1 in a new, 37 foot motorhome. He said the dry weight is around 19,000 pounds and GVW of 22 or 23,000 pounds. He is also going to pull a cargo trailer with a Goldwing. I'm guessing the trailer and bike may weigh about 2000 pounds. I haven't told him yet, but I think he is going to be disappointed in the horsepower and performance with that much weight. Which mods adds the most hp/torgue for the money? What can he do for $2000 that won't compromise the durability of the engine? He has a 5 speed Allison 1000 like goes behind the Duramax.
I have added the Juice to my diesel, and WOW, what a difference in towing. It is absolutely UNBELIEVABLE!!!!
Your comments would be appreciated.

[bobojay]

I could sure use some upgrade ideas on ours. We are very dissappointed in the towing power of this motor. I know, I should have gotten a 4:10 axle, but that's water under the bridge now.
I've been thinking of a Volant air intake. I have bought a Grannatelli Mass air flow sensor, but not installed yet, and lastly, a Superchips controller.
Our biggest problem that just annoys the hell out of me is the constant downshifting/upshifting when the least little incline is encountered. Worse when the cruise is activated. It'll stay downshifted running at 3700 rpm at 65 mph for miles and miles if I allow it. I know this was a problem with the early Duramax/Alli. combos, but a flash upgrade mostly cured that.

Got any ideas on this. Otherwise the truck is wonderful.......

[Duramax@Mattawa]

Just to add my results. I have a 2001 8.1 with 20,000 miles. Last summer took a 5 week vacation pulling a 38.5 ft Avion 5'ver. Truck and tlr weighs 24,100 lbs. Averaged 8.5 over 5000 miles. Currently have 9.5 slide in camper loaded (don't know weight) and get about the same 8.5-9 mpg. Empty mileage will run about 12-13. I'm pleased with the power (Pull off in Mt. was equal to stock Duramax) Absolutely love the tranny. The tow/haul is amazing.

[8.1GASSER]

Biker Wayne & others, sorry for the late response(been away this weekend), First things first, the dmax and the 8.1 are completely different animals, that run on opposite sides of the RPM spectrum. The dmax is nice since you can add the juice and be done if you want, with major gains. The 8.1 on the otherhand, takes a bit to coax the power out of it. Currently I am running The Other Guys headers, Flowmaster cat-back, Direct Hits ignition, UPD intake, modded MAFs, and Superchips tuning. Truck with 35" tires dyno'd at 300hp and 440ft/lbs. at the tire, the outcome will be different with smaller tires(the 35's chew up quite a bit of power). This may sound like a lot of work and $$ but if you shop around you could do it for $2,000 or less. Now for best bang for the buck mod, my green would be on a Superchips, or Predator tuner. Or for alittle more saving time a supercharger.
Biker Wayne, No doubt that your friend is going to be pulling high revs, towing that load, whereas a dmax would be purring down low. I have towed with both and cruising on the highway they are very comparable, once you hit a hill they both will pull it fine, but at way different rpms.

[8.1PWR]

Has anyone installed a Helix or Airaid throttle body spacer on the 8.1L? Has oneone used the Hypertech programmer? And do you have to run premium gas if you use the programmer. I allready run the K&N intake system and did not notice any difference in power or fuel economy. I don't want to spend any more money on things that don't work.

[dave p]

read trailer life report 8.1 vs duramax. the 8.1 will take a duramax loaded or unloaded. pull up beside one and find out. if the duramax was so hot why did everybody get the juice? dave p

[DmaxMaverick]

^

Because we can


BTW
Trailer Life is grossly mistaken. Personal experience says otherwise.

[Colorado Kid]

Originally posted by dave p:
read trailer life report 8.1 vs duramax. the 8.1 will take a duramax loaded or unloaded. pull up beside one and find out. if the duramax was so hot why did everybody get the juice? dave p I'll admit I haven't read the report. I'll also tell you that your statement does not correspond with my observations of how my D-max and my father-in-law's 8.1/Allison (with 3.73 rear) handle the same trailer, and I'm still stock.

Perhaps Trailer Life tested near sea level. . . we don't get down into the thick air much but I'd say my F-I-L's truck comes closer to mine at 5,000 feet elevation than it does at 11,000 feet.

The 8.1L is by no means a dog, in fact it does better than any other gasser I've seen for pulling a load, but the only way it'll out run my D-max is if I forget to shift.

There is one other way . . . the speed limiter on the 8.1L is a bit "softer" than on the D-max, on a downgrade his will creap up to about 99 MPH while mine holds firm at 97 MPH (With the 5'ers in tow, and neither of our wives woke up while we were checking this out. . . unfortunately my 5 year old ratted us out.) :rolleyes:

Somewhere on I-80, he could pull slowly ahead on the down grades but the mighty 'Max stayed at 97 MPH on the uphill too. . . not so the 8.1L. :D

[8.1GASSER]

ColoradoKid makes a good point about altitude. Quite simply the 8.1 will not hang with the Max as you go up in altitude, mainly because of the turbo on the Max, now if the 8.1 had a SC or turbo then all would equal out again.

[84 C2B2]

Just thought I'd throw my name into the 8.1 gas gang. My old truck is an 1984 Military P/U. 6.2 and a few modifications. Just got tired of working on it at it's beck and call and not my schedule. Picked up a really nice 2002 K2500HD CC LT. Had only 12.5K miles on it. Modicfications are a cat back flowmaster muffler and pipe, spray=in bed liner, and a Warn 12K winch and bumper. Fully loaded. Never felt this good about a truck before. Nothing in the works at the moment for modifications since I will not trailer the rest of this year. Just want to get used to this "White Knight" as my son calls it. I'll be checking in now and then to keep updated on performance mods.

Jerry