lost 3-4 psi boost

[fast03]

truck is running good just not super strong. watched the boost gauge and saw I lost about 3psi wide open. I logged a run and saw actfrp was down to 19-20k during hard runs. New filters about 2-3k ago lift pump running well. I will have to change the filters again, and I cannot hear a boost leak, but is there anything else? Thanks for any ideas

 

[fast03]

Bump for other ideas

 

[TrentNell]

Bump for other ideas

What kind of fuel are you commanding ? could be small boost leak are the EGT's higher than normal ?

 

[fast03]

Thanks Trent. Commanded is up to 45k, desired will be 23k-24k and actual is 19k-20k. I did not run a quarter mile, just some short runs, that I would normally see 33-34psi. Everything seems normal otherwise. I am getting the new filters, but I do not think I would lose so much psi over the fuel pressure loss. I will have to log the shift points, but it seems like the TC may not be locking up early under hard acceleration until 3rd. I can feel it lock with moderate throttle in 2nd. No codes either.

 

[TrentNell]

Thanks Trent. Commanded is up to 45k, desired will be 23k-24k and actual is 19k-20k. I did not run a quarter mile, just some short runs, that I would normally see 33-34psi. Everything seems normal otherwise. I am getting the new filters, but I do not think I would lose so much psi over the fuel pressure loss. I will have to log the shift points, but it seems like the TC may not be locking up early under hard acceleration until 3rd. I can feel it lock with moderate throttle in 2nd. No codes either.

What pulse width is your tune running ? just trying to see if your lack of fuel is causing less heat and would equal less boost . then would go from there on what else could be the culprit .

 

[fast03]

Running the Mcrat race tune. I cannot remember off the top of my head, but thinking it was 3400 at the top

 

[McRat]

Your charger is gated, correct? Could it be the gate?

Also remember that even a gated charger works on pressure ratio, not PSI at the gauge. In very hot or thin air, the gauge will read lower.

Example: If the base pressure is 14 psi (normal air), and the gate is at 3:1, the gauge reads 28 PSI. (14+14+14 minus base pressure of 14)

If the base pressure is 12PSI it will read 24 PSI (12+12+12 - 12)

Tuning on an LB7 normally does not cap the boost since it's gated. If DA was the same, then look for leaks, fuel system restrictions, air inlet restrictions, and turbo damage.

 

[fast03]

Thanks Pat. temp and pressure should be ok here in So Cal. weathers been good. I will check the stuff you noted. Filters coming today and will go through it all. I gotta be ready to give it my all to beat Kat this year at the pull Saturday.

 

[LBZrcks]

Mike L had a boost leak and I think he traced it to the boots on his intercooler pipes. Might wanna check those.

 

[fast03]

Thanks Jason will do

 

[LBZrcks]

Steve there is also a tool that slips on to one of the intercooler tubes and you hook up to a compressor and start building pressure slowly to help find leaks easier. Some dealers should have the tool.