LUCKY DAVE

Yesterday I was protested, the (slow *** whiny worm) complaining I must have a modified boost control because I'm so much faster a driver than him. Like that would make a 5 second difference
Ok fine, so I allowed the tech Czar to install his cheap plastic uncalibrated gauge in line with my fuel pressure regulator and we went for a lap.
The results, 1.05 bar spike (or maybe steady, I couldn't see the gauge) and the tech **** assigned me 7 points for "modifications to boost" which kicks me up a class, and accused me of cheating
The car is an '89, and all stock as far as I know (I've had a lot of it apart over the years) except for a test pipe.
Just how much boost should this car make, and most importantly what deviation, or "tolerance" should be expected for a 21 year old car? How close was one car to another in the first place? After all, it's a rather crude vacuum controlled diaphram system, not too sophisticated......

DanR

0.75 bar stock I think on an 89

Oddjob

Stock boost is 1.75 bar abs or 0.75 bar gage. Factory spec is +/- 10%. Which is a little ambiguous as that could be calculated as + 10% of 1.75, which would be 1.925 bar abs, or 10% of 0.75 bar gage which is 0.825 bar gage. So its in your best interest to argue that its 10% of 1.75 bar abs. (note: I have had this discussion with scrutineers before...).

If your car is spiking to 1.05 bar gage, something is not right. Either something is modified in the boost control system, something is not working right in the boost control system, or the gage is incorrect.

Was it an instantaneous spike, then immediately dropped to .8 bar gage (or so). Or did it hold the 1.05 for 1000+ rpm? What did the boost drop to by 5500 rpm? What gear was the test done?

fast951

I recently dynoed a MY89 951 with a completely stock and fresh boost system. We did see a spike in boost of 15-16psi in the lower RPMs, then it dropped to 10.8psi.

968turbos2

If he installed it inline with the FPR vacuumn line then the spike was probably caused when the throttle shut while shifting. It should be inline with something on the manifold itself. The fpr line will spike when the throttle closes before the blowoff vavle releases pressure. Right?

jerome951

My stock '89 boosts to ~14psi for a second before leveling off @ ~10.5. If you're exceeding 1 bar on the initial spike I think you have something wrong.

Van

I posted this last year thinking people would find it in a search...

https://rennlist.com/forums/944-turb...-pressure.html

carlege

LOL you smoked him