What are 'normal' LB7 boost pressures and EGTs?

[Mark Rinker]

After two weeks and ~3,500 towing miles, my new digital gauge (thanks, JK) shows a max attained boost of 21.5 and max EGTs of 760.

Driver reports that nominal (loaded cruise at 65mph) observed boost is 3 lbs and EGTs are ~400 degrees.

This is the first data I have from a Duramax. Seems low compared to my 6.5. Are these numbers 'normal'?

[More Power]

Sounds like your pyro is located downstream of the turbo.... Temps there will be 100-300 deg cooler than when measuring in the exhaust manifold.

Stock boost pressures typically run anywhere from the high teens to low twenties. Some of this depends on the air filter or intake system in use - lower with the stock air box and paper filter, higher with a performance air filter and/or air box.

Also, you might have a look near the end of TDP's 2002 gauge install piece (http://www.thedieselpage.com/members/duramax/dmaxgage.htm) to see more info about typical LB7 pressures and temps. :)

Jim

[Mark Rinker]

The pyro sender is in the exhaust manifold, as in the article. We wanted to use the best known methods - following the recommendations here on the DP.

I am almost too embarrassed to admit this, but the gauge default was Celsius, rather than Farenheit. (Oddly, the boost default was LBS, rather than BAR.) My eyes aren't what they used to be, and I finally looked REAL close and saw the tiny "C" instead of the "F". Dooogh...! :)

The nominal EGT figure he observed would then be 750, more in range with my 6.5 EGT experience.

The 1400 peak temp for last week was a bit worrisome - plenty toasty. I did some test runs with trailer and skidder in tow, about 11K lbs. 1400 can be reproduced at will with a heavy foot and heavy load - but only happens when 'dual fueled'. On diesel alone, the same run will produce 1200 degree temps, by comparison.

[More Power]

The stock LLY's we've run during the Pull-Off would reach 1400, the stock Dodges would run at 1400, and the stock PSD 6.0L would run at about 1250. The Edge/Att installed on Lil Red has recorded as high as 1787 during a 1/4-mile run (w/additional programming and nitrous)... ;) This is OK for a few seconds... I know some who have seen 2000 without a prob.... :eek:

A wise racer once told me not to look at the EGT gauge during a run.... :D

Jim

[Mark Rinker]

I feel much better. Never saw 1200 with the chipped 6.5. Must not be enough fuel present.

Trying to set things up to maintain a ~600 degree EGT at cruise, loaded. More boost needed, I think...

Question: What boost setting would you be comfortable with, towing 10K for hours on end? Mine seem very low (~3-5 lbs) in comparison to 6.5 settings of 10-12 nominal under load.

Does the Duramax have the same boost 'sweet spot' like the 6.5 - where climbing EGTs begin to drop off, as boost pressure is increased?

[Jomar]

Mark, I have found out that using T/H mode in the tranny when towing will drop the egts noticeably.

Jomar

[mark45678]

flat cruise nothing in tow 4lbs of boost , 550~600 *F post turbo. Pulling a hill loaded stock fueling 22 ~24 lbs of boost and 1000*f post turbo with aftermarket 4 " pipes and strait threw sound trap. I have seen as high as 32lbs with the juice turned up and 1150 *f post turbo. I think the stock waste gaste is set at 30~32 lbs.