Balance rates

[dwight schneider]

The Fermanat, thanks for the great information. Hope you see this and reply, sounds like you have a great handle on this. My 2006 3500 LBZ 100,000 miles, has new turbo, erg blockoff, 4" cat back exhaust, synthetic engine oil, has a second efi live tune specifically for improving towing mileage, tires all at 75psi on truck 80psi on trailer and still only gets 8.8mpg at best at 60 to 65mph. I have tried locking in 5th gear and it was actually 6.8mpg on the flat in Kansas no wind great day for mpg testing. Two shops have told me balance rates are good. But based on your information I have 12 to 14MM3 and 13 to 15MM3. According to your figures this puts several cylinders out, as my readings are similar to other examples here? This thing is killing me and it is an otherwise great truck, almost all options, drives nice, rides nice with a load. Any ideas, or just change the injectors?

 

[THEFERMANATOR]

Whos tunes first off? Second I would try and clean the injectors before replacing them. Also be CERTAIN the tune in the truck is stock, or uses stock fuel and timing tables at idle or else the balance rate numbers are worthless.

 

[dwight schneider]

The Ferman, couple of edits on my last reply. It does not come up yet where I can see it so I assume it has to meet the moderators approval prior to posting. The 'in drive fuel flow averages 18, and I think I said 14 (wife was hurrying me to go). I also have the basic Fass lift pump installed. It has a Banks filter, kept clean and very lightly oiled.

The other thing with the balance rates, I have seen as high as 10 and -6.8 at times checked when engine is fully warmed up driven for and hour or two other times the numbers are well within specs based on GMC guide. Then 2 hours later there will be significant spreads with one or two, particularly #8 out to 8 or 10 again. To me this says there is probably wear, springs and seats and O-rings not in great shape?

The truck had done 18 mpg empty once and nearly 20 once empty over the Colorado mountains, Vail & Loveland passes. But will generally only do 12 to 14 empty, weird. I have had the truck into a couple of the supposedly top shops that do lots of performance work in Denver and two GM dealers and they all say, 'it is in great shape, mileage should be better but it is a 1 ton, drive slower.' Really 60 & 65 is killing me! I am ok with 70 but 75 would be even better empty. Our trailer is not heavy either 10,000 even. I gave up a Dodge 1 ton that got 16 to 18 towing for this thing! Makes me want the dam Dodge back?

 

[dwight schneider]

Whos tunes first off? Second I would try and clean the injectors before replacing them. Also be CERTAIN the tune in the truck is stock, or uses stock fuel and timing tables at idle or else the balance rate numbers are worthless.

Thanks for the quick reply. The truck was originally tuned by Wade at Diesel Day Dreams in Thornton CO. Wade's towing tunes were 30 HP and 80 HP but I am not sure what he did on timing, supposedly everything kept very close to stock conditions. His program did change the transmission shifting, don't remember the details. The last tune is by Powerup Diesel Steve Shelley out of Montana. Steve says his tune on the LBZ is about 60 HP with more low end torque. Trans back to stock with Steve's tune. Diesel Day Dreams ran a chemical cleaner through them. Or are you saying to pull them and have them cleaned? The truck ran 80,000 miles prior to my buying it with low loads and no lift pump. Turbo was very gummed up.

 

[THEFERMANATOR]

For cleaning the injectors I like to use 1 gallon of diesel, i bottle of GM upper engine cleaner, and get 2 sections of hose about 3 feet long(1/2" and 3/8"). Mix the bottle of cleaner in with the diesel, disconnect the fuel lines at the rear drivers side of the engine, hook up the 2 pieces of hose, run them into the can of cleaner/diesel mix, then run the truck for 20 minutes, then shut it off for 20 minutes. Repeat this process until the mix is gone. The GM cleaner is REALLY good stuff, and when you shut it off, it gives it time to soak i nand break deposits loose, then you start it back up and it flushes the gunk out. As to your tuners, diesel day dreams has a good rep from what I could find, but couldn't find any info on the other place(not always a bad thing). I will say most tow tunes are not good for milage as tow tunes normally keep you on boost to help with throttle response, limit smoke output, and keep EGT's down. True economy tunes will lower boost, raise the timing through the roof, and probably bump some rail pressure into it. All of which are bad for tow tunes. As to trans shifts, I personnaly like to leave them alone on the 6 speeds for the most part. The 6 speeds already have pretty good shift points to them IMO, and I see no real reason to alter them for most. And since you say you have a dually, it's never going to get great milage. Also are you hand calculating your milage or going off the lie o meter. The factory DIC is KNOWN to be WAY off on some trucks, hence why most call it the lie o meter.

And anytime you have fluctuating balance rates like this, it is normally a good idea to also do a compression check on the engine. Since you're not the origanal owner, you have no idea what was done to it before you. it is most likely injectors, or high fuel temps causing your issues, but a compression test is good peace of mind. For your truck, I would reccomend a good DSP2 tune with an economy tune for running empty, and then an optimized towing tune. And while I'm thinking about it, how are you checking balance rates? Your milage does sound a bit low to me, but not out of the realm for a dually. I know I have my tunes running around in several single rear wheeled trucks getting an honest 21MPG on interstate at 70-75, and one in a DURABURB getting some pretty good numbers hauling his camper across country towing. How did the milage compare when it was stock to tuned?