Manifold KPA to PSI

[Mike T]

After my new motor was broken in and before I had a boost gauge or a PL I made a couple of short WOT pulls through the 1-2 shift while watching the manifold KPA's on the Translator Pro climb to 200. The online calculator converted 200 KPA to 29 PSI so I backed the boost down. My car seems to tolerate high boost well but I don't think it was possible that the manifold pressure was really 29 PSI. Am I maybe missing something that should be factored into this equation?

 

[Eric Stage I]

200 kPa is 14.5psi boost.

 

[Mike T]

200 kPa is 14.5psi boost.

Now I am really confused as I am sure that you are right but since your reply I check another online calculator that converted 200 to 29 as well? The other thing is that after backing the boost down I installed the PL & a new boost gauge that both now confirm 21 psi? I don't understand how this could be?

 

[VIN7]

100kPa of that 200kPa you are reading is atmospheric pressure so you subtract 14.7 psi. What do you see on PL for manifold pressure at key on, engine off? Should be close to 100kPa if you are near sea level.

Mike

 

[Mike T]

That's it! Now the conversion makes since I'm @ 57 feet and around 101. I thought for a while that I may have screwed up and let it hit 29 psi on pump gas for split second. Now what I still don't quite understand is that the car will hit 20-21 psi in the higher gears even after backing it down from the original setting.

 

[Chuck Leeper]

Known as boost creep.
Puck too small?
Exh hsg need porting?
Waste gate mechanism screwed up, binding?
Gauge wrong?
Exh back psi too high?

 

[Mike T]

Chuck I am going to say no to all of the above except for maybe back pressure. I do have the original exhaust pipe from where the cat use to be to just before the rear axle. I have an 85 gtq housing, a THDP with a good size puck, a new precision HD actuator that I tweaked until everything was perfectly aligned, brand new autometer boost gauge and a new three bar bap sensor. I will attach a PowerLogger file to see if it looks like boost creep. BTW to view PL file MAF is set to 768 and MAP is 3 bar.