jhenson

My '03 idles about 5k RP and cruising reads about 15-17k RP. Been driving my buddies '07 since my tranny is getting redone and his idles about 8k and cruising runs right around 20k. Why is there such a big difference between these year models? Hopefully my CP3 isn't on the fritz!!

PoorMansCat

Software....

StealthDiesel

Lots of variables here..

The 2003-04 engines run lower rail pressures even though the CP3's are identical to the later 5.9L engines.

A programmer can really increase rail pressure, especially a non-Smarty programmer like the Diablo or Bully Dog or PPE.
A Smarty with the rail pressure parameter set to high levels will really increase rail pressures.

The early Autometer rail pressure gauges were not calibrated correctly & they read high.

Your buddy might have a pressure box installed like an Edge EZ, TS MP8, ATS Atomizer, etc..

jhenson

My truck has the BullyDog Downloader and the rail pressure reads the same no matter what setting it's on.....my buddy on the other hand has a Smarty and he says he has the rail pressure set to default.....but, he does however have the Autometer guages as posted above..maybe that's the difference. On a WOT run his RP guage will spike and hold at 30k until he lets out of it. That just seemed a little off to me but a while back he kept throwing a code for high rail pressure but since doing the injectors it hasn't popped back up. Kinda has me wondering.