High EGT, Low boost pressure???

[BAIrwin]

Hello everyone. I'm just wondering if I have low turbo boost pressure compared to others? I have a stock HX35 turbo with the boost elbow plugged. The highest boost pressure I have ever seen is approx 25-27 psi. (OD off, 7% grade hill pulling camper). Is this normal or do I have a boost leak or some other problem? I've owned the truck since 2003, 50K and the truck has always run well. I'd like to have a bit more usable power before getting into high EGTs. When pulling my camper many times before cresting a hill the EGTs will get too high and I have to take the OD off (thus slowing down and the engine rpm racing). I have lots of power available, just not usable power before the high EGTs. Any thoughts as to how I can solve this? Thanks in advance for any replies.

1997 2500 4x4 12 valve Cummins, auto, X-cab long box, fuel plate removed, full-forward AFC housing, ground end of rack, replaced cupped washer with a flat washer, 4K springs, turbo wastegate elbow plugged, Goerend TC & VB upgrade, Dipricol gauges (exhaust, trans, boost) 230K, KDP repaired.

 

[BigPapa]

Welcome to TDR BA.

A few questions to help us help you:

• What do you consider "High EGT's"?
• Where do you have the thermocouple located?
• What do you consider "engine RPM racing"?
• At what speed do you take it out of overdrive?
• What's your R&P ratio?

 

[Bob4x4]

No fuel plate is a clue

 

[GAmes]

With no fuel plate and the wastegate closed the boost should easily exceed 30, even with stock injectors. I'd be looking at the boots and testing the intercooler for leakage.

 

[BAIrwin]

Thanks for the reply:

• What do you consider "High EGT's"? (redline on the Dipricol EGT gauge...1250 deg F)
• Where do you have the thermocouple located? (before the turbo on the exhaust manifold)
• What do you consider "engine RPM racing"? (having to drop the OD before cresting a hill, I know the engine max readline is around 4300 rpm??, however I don't feel comfortable running the engine at 2500 rpm+ for any length of time, it just doesn't seem right the engine blaring away...)
• At what speed do you take it out of overdrive? (at whatever speed the EGT redlines, when pulling a trailer up a shallow hill usually between 55-65mph)
• What's your R&P ratio? (if you mean rear axle ratio I believe its 3.54:1)

I also have a 4" exhaust.

 

[Wiredawg]

No expert here, but have you ruled out intercooler/hose leak? Low boost and high EGTs are related to each other.

Just another thought.

Cheers, Ron

 

[Road Dog]

The redline is around 3200 rpm but the 12V has a governor to limit rpm to 2700-3000. The engine can run at full speed all day long.

Generally when climbing hills I keep the rpm in to 2200-2800 range and egt below 1200F. My temp sensor is in the exhaust manifold ahead of the turbo and I have 3.54 gears, stock injectors and an HY35 turbo which tops out at 17psi. I'm not in a hurry.

 

[BAIrwin]

I've visually looked over the intercooler & hoses, I don't see anything obvious. If a small leak is present, are there any tips on troubleshooting this?

 

[GAmes]

Building a pressure testing apparatus only requires some PVC, a shraeder valve and shop air. IMO you have more than a small leak. One likely source is the lower boots rubbing on the inside of the fenders. Charge air coolers have been known to fail, thus the tester.

 

[BigPapa]

Building a pressure testing apparatus only requires some PVC, a shraeder valve and shop air.

AND, a spray bottle of soapy water.

Check it just like you would look for a hole in a tire.

 

[BAIrwin]

OK thank you. Is there a specific place I should install this valve? Do I need to block off any of the air ducting before doing the test?

 

[Road Dog]

Here's an example of a DIY tester: boost leak tester

 

[BAIrwin]

Excellent article! I'll have to try making one of these. Thank you very much everyone for all of your help, it's much appreciated