I wish I had the cash to drop on a Dually Ram... Even though I just want the engine.

 

Yup, I'd love a Cummins motor, Allison tranny, and Dana Axles. I've gotta pick and choose and now that I've found some really stout tie rods, I've going GMC. D-max has proved to be a great motor built by Isuzu and that will just flat haul with some cheap mods.

 

actually ford brought back the excursion with powerstroke option this year. you dont hear about it because of the low sales. it is def a niche market. most people that want big suvs dont want the noise or smell of diesels for some reason

also tony, that is a good point with no hills - but the displays have notoriously been off a few mpg - esp if there is ANY programer on the truck. but even assuming a few mpg off, that isnt too bad. anything has to be better than the 12-13 real world mpg on 5.3 or 6.0 motors.

 

Yeah, my Z71 used to get just plain bad economy when stock. Maybe 13mpg avg and NEVER more than 17mpg freeway. Now with 33" tires and 3.73:1 gears I can muster (is that the correct word here? ) 15.5-16.5mpg avg and 19-20mpg freeway only...that's in an ECSB 4x4 LT package. I can get those numbers due to my tune. My avg economy now is almost what my straight freeway used to be!

I 100% believe GM purposely detunes vehicles so much inorder to meet the CAFE (Corp Avg Fuel Econ) limits for each year. It's truly amazing how just a simple tune can make the vehicle so different...don't forget the tune I also believe is the main difference between the 99 and 00+ trucks and each "HP increase" GM pretends to make.

When I was lookin' at that LLY I told those dudes at the lot and they were like " you get what kind of milage in your Z?"

 

19-20 mpg with 33" and 3.73???? are you sure that your spedometer is corrected for the tires and gearing? it just doesnt make sense that ANY tune could MAKE ADDITIONAL milage with things working against you like heavy heavy rotating mass and worse gearing in an auto. just wondering. i have never heard of anyone getting anything close to 20 mpg with big tires and gearing on the highway!

 

Yes, I was standing beside Allen when he tuned my truck so I know my speedo is scaled for the tires and shift points.

Well have you ever looked at the timing tables, abuse mode, and TqMgt setting of these trucks? I believe I was NEGATIVE 8-10* from about 3500rpm-6000rpm...something like 40* was being pulled. Abuse mode was on anytime...I think it was over 1mph and 1500rpms. BTDC at idle I think was ~7* LOL.

Basically the truck had no power at all, it was running and that's about it. Hell it probably could have run off of 75 octane gas if it were available. The tune made it drive soooooooooooo much better. It moves out of the way far easier now as it has timing advance! It's truly a different vehicle.

Also I cruise on the freeway. My speeds are fron 65-72mph. Any faster or slower and the truck lugs very badly. That's the ideal cruise speed for time vs economy. Driving styles/habits determine your economy. I have all my fuel receipts (sp?) that show the economy I gained...I keep them for 1099 Tax reasons too.

 

so you are saying i could potentially (or anyone could) get say 18-19 mpg on a stock yukon like mine? (5.3L 3.73 4wd stock everything) with this nelson tune? if so i am very interested. any performance gain would be a plus too!

 

Well it depends on how you drive. I also have NO TqMgt at all left, I had it all totally deleted...I think that has something to do with it. Also I have a maxed tune that burns 93 pump gas. Also I'm a FIRM believer that TqMgt helps kill these transmissions. Toss all the line pressure dumping and just some timing pulling would be okay until you toss a TransGo in there.

If you have stock tires, I don't see how 20mpg is going to be out of the question. But it's all on how you drive.

Trucks need to cruise at ~2000rpm around 60-65mph. Mine at 70mph is like 1800rpms. It drags, not really bad but it's noticable.

I think 1BADHD picked up 2-3mpg with his custom tune from Wester (over a Predator if I recall) and Tiburon also picked up some stout gains even with a cam with a custom tune from Allen.

Anything that you can do to increase the efficiency of the motor should give power and economy...full exhaust on my F-150 got me almost 2mpg more on it! High flow intakes, ported heads, mild cams, etc. IMO, you can have power and economy you just must draw the line somewhere on the cam as I think that's what makes/breaks the economy. Intake duration like 208-214* is about all I'd go for to keep the economy. Just gotta tune it all in the end to work well together.

 

From what the plant manager in Janesville told me, the current Suburban/Tahoe platform was not designed with the Duramax in mind. Too bad, since I'm now driving a 2003 diesel Excursion (ordered it new and paid $41,400 after all the rebates were factored in). Then again, I wasn't crazy about GM moving all 3/4 ton Suburban production to Mexico, so I might not have bought one anyway, especially if I had to deal with the poor build quality of another Suburban built south of the border.