Diesel Tuner's Blog

Duramax engines have always come with solid turbos. However after miles and miles of whistling and boosting, your turbo may have problems. Or you may have other issues, that make you think your turbo has problems. This is very common as most drivers watch boost, keeping an eye on how much PSI they're making. It stands to reason that if your peak boost drops, your turbo has a problem. This is usually not the case though. More often then not, when we diagnose this symptom we find there are other problems leading to a lower than expected boost number. 

Target boost numbers for the following RPO's are as follows (PSI)

2001-2004 LB7- Stock 20-22, tuned 24-26, tuned with PPE boost valve 28-31.  Failure will occur near 34psi

2004.5-2016 Stock 22-24, Mild tune 27-28, Hot tune 33-35

The factory map sensor which electronically measures boost on a 2001-2004.5 trucks only reads to 22-24 psi, 2006-2016 MAP sensors read to 37 psi.  If you want to read boost numbers higher you'll need an aftermarket gauge. 

Too often trucks come into our shop experincing high EGT's, turbo lag, excessive smoke output, and bad fuel mileage which are all symptoms of a boost leak. It is so common to develop a boost leak that we now require all trucks to have a leak down test done prior to strapping them down on the dyno. What's funny is, most truck owners that we do identify boost leaks on never even knew they had one. The reality is that even if you can hit peak boost, you may have a leak, especially if you have a variable vane turbo. Variable vane turbos will change vane position and other operations to try to compensate for the reduced level of boost pressure in the intake system. Leaving you driving around without an idea that your turbo efficiency has taken a hit.