Hi Mike,

I thought you may know what others can't answer accurately. I have asked before about correct boost pressure for my car and people usually end up telling me what their cars produce, this is no real use unless it is the same model, which to date it hasn't been.

I run a MY05 STI PPP Type UK, do you know (in PSI) what it should produce ?
out of interest, I would like to know pre PPP as well.

Hope you can help.

Cheers

Simon

 

lot's of views I see, but no Mike....................

 

I have exactly the same car and I'm sure it's 1.2bar on my Subaru boost gauge (sorry doesn't indicate PSI)

 

Cheers for your input. Mine is in PSI and I can read a peak of 20PSI under certain conditions and it drops back to between 15 and 16 PSI at the high end of the rev band. Normally 18 / 19 PSI peak.

 

Might help,

20 PSI = 1.378 bar
19 PSI = 1.310 bar
18 PSI = 1.241 bar
17 PSI = 1.172 bar
16 PSI = 1.103 bar
15 PSI = 1.034 bar

 

Cheers, a useful table. Now we need the official figure in either PSI or Bar and both me and Grollysti will know if it is right to spec.

 

The boost pressure displayed on a gauge will vary. This is due to the boost target pressure being set as an absolute value, not gauge.
This means that depending on the atmospheric pressure the 'correct' boost could vary by approx .05 bar or 0.7 of a psi
The boost target pressure is also varied by rpm, typically the target boost is reduced as the revs increase above 5500rpm.
Hope this helps explain why there is no finite answer to your question !

Andy

 

Thanks for your answer Andy. I understand what you are saying, but wouldn't Subaru or Prodrive (somewhere) have am actual peak or steady boost pressure that is the benchmark as standard or after PPP ? They say the PPP increases the boost, but how much by and from what original figure. I guess mine is about right as I timed it last weekend from 4 standing starts and hit 4.5 sec's 0-60 and with a bit of bog down 5.1 sec's so it can't be far out as Prodrivr book the MY05 STI PPP at 4.6 from memory (figure quoted for MY04 but press releases at the time said it was the same performance.

 

I Guess Mike must be on his hols then ?

 

The PPP STI UK boost profile is heavily compensated depending on intake temp also. Anything over 20 degrees C results in a graded reduction in midrange boost, in my experience.

FWIW at low intake temps I've seen 34psi absolute held to 5000rpm in midrange tapering to 28psi by 6000rpm, which is held to 7600rpm. Or roughly 19.5psi to 13.5psi MRP. Intake temps between 20-30 degrees tend to result in ~18psi in the midrange.

Cheers

Simon

 

It's not an intake temperature compensation as low as 20C.
The upper limit on the wastegate duty cycle map will have an effect on the maximum boost achievable as intake temperatures increase. This is due to the decrease in intake air density and a requirement for the turbo to work harder.

Andy

 

Gotcha

 

Hi Andy

I just wondered how the AVCR on my car "knows" about the intake temps ??

and...........any answers on the NOS ??

Cheers

Shaun

0.6 MPH to get to 200 MPH.......did you drop the ariel ??

 

Shaun it doesn't, the ecu can't do anything even if it wanted to as the AVC-R is independant of it entirely. If you are going to run NOS then change mains and big ends first to somethiong better as a minimum.

Bob

 

The ECU can't do anything with the boost but it can pull back the ignition timing and add more fuel if it considers the engine is becoming unduly stressed.

I'm away on hol for a week tomorrow, will discuss N2O on return.


Andy

 

Hi Bob

Thanks for the post.... I think this is a case of "a little bit of knowlege is dangerous" !!!

Cheers

Shaun