weird boost pressure difference

[bscottie]

anybody ever seen different boost pressure because of tune? happens with my car, totally baffled on this one

 

[Charlie Sheen]

Can't help you with the tune part, but I did get different readings when using different power sources.

 

[bscottie]

well I am in tune hell and cant get out, I am "experimenting" with tunes I have which were from old setups, hard to believe no viable source for tuning in Nor Cal, dammit!!!!!!!!!!!! no change in pulleys, gages, or power supplies, just tune change, very odd

 

[Dex]

I would take a drive south to ST. You start messing with tunes you fuck your motor. First hand experience...

 

[bscottie]

was hoping to see ST a month or so ago when he was going to come North a little bit, dont really want to drive the car as is 400 miles, what a bitch of a problem.

 

[Charlie Sheen]

I think Adam is planning another dyno-fest at the Whipple factory in Fresno, I'll let you know when I catch the date(s).

 

[bscottie]

if it is gonna be soon that could possibly be very good, talked to a guy today about some tune mods via the internet. desperate tims call for desperate measures. will be glad to have ST take a shot at my car

 

[TexasBlownV8]

Are you talking WOT or partial throttle?

FWIW, if the same systems are enabled/disabled between the tunes, you shouldn't see any difference. The SC head unit is still going to produce the same amount of boost at a given rpm, regardless of the tune.
However, the boost seen at the intake manifold CAN be affected by what other emmission control systems are enabled. For example, if the egr valve is open, you could loose some boost through the egr tune into the exhaust.

I've used several tunes, and never had boost affected by the tune (of course, assuming you are talking about the same boost at any given rpm). And as mentioned, part throttle vs wide-open can make a difference.

 

[bscottie]

WOT, its a little weird, I know I just need a tune, thanks for the comments

 

[TexasBlownV8]

The other quick-thing I can suggest is to make sure you BOV/BPV is working properly and not sticking. When I was putting my system together, a new out-of-the-box BOV was defective and would not close under boost.
But if you are seeing consistent boost differences and values from different tunes and the values are the same per each tune (ie, tune A has X psi at some rpm, change to tune B and it has Y, change back to tune A and it goes back to X), then your issue is not likely the BOV.

How much difference are you actually seeing? Have you mapped it out on paper or in a spreadsheet to see what boost vs. rpms are actually occuring? I used a video camera caputing the movements on an analog boost gauge and the tach at the same time, over several runs; then wathced the video back slowly, plotting rpm/boost values in an Excel spreadsheet. There was a little variation, but not much.

Also, are you aftercooled or not?

 

[joedls]

I had a similar problem that was driving Greg at RET crazy. My car made boost on the baseline run. He loaded his tune in and it quit making boost. He figured out that it was something in the IMRC table that was keeping the bypass valve open, I think. Once he figured that out, I was making boost again.

 

[bscottie]

dont believe it is the BPV, I am not after cooled, swap tunes and you see the difference on the gage, seeing about 1 1/2 psi difference, almost 2, think I will just go shoot the car, I have a 9mm I haven;t shot in a while.