Cyrus951

Now that my gauge came back from autometer, I've had the privelege to get some correct readings. In 2nd and 3rd gears, I get a max boost of only 12psi (under full throttle) Is this normal? What are the normal boost numbers under 2nd and 3rd?

Also, in 1st, I opened full throttle, and near the redline, the factory "!" idiot light flashed, then went off. Is this the overboost protection?
And, what should the gauge read when idling? (mine reads -10)

Thanks.

Songzzz

Idling should run between -16 to -20. At what rpm is the idle when warm?

-10 is definitely too low, could be a vacuum leak. Make sure the gauge is properly installed, check the back and see if the nylon tube is fully in.

Cyrus951

What boost should I be seeing in the lower gears?
I'll double check the tubing..

Songzzz

Are you running MBC? I have no idea what stock boost is, but typically, you should not see full boost until Gear 3 or 4.

Cyrus951

Car is stock, I'm just running some nameless "superchips"

Tom M'Guinn

Check your oil. When it is low, the ! light can come on under hard launches and hard cornering. Always a good idea to keep the oil topped off on these cars anyway. 12 psi is in the range of normal for a completely stock 951. As for your vacuum at idle, it should be 16-19 In.Hg's or so. You might want to put a mechanics vacuum guage right on the manifolf to get a true reading. If it is really only 10 inches, that is too low in my experience. Mine runs at least 16 inches when warm, and starts to get lumpy under 12 or so.

hosrom_951

If you had CHIPPED the car, then you should read somewhat over 12psi, more like 15~16psi in the range........stock is 11psi (if my memory serves me right).

Tom M'Guinn

I think that depends on the chips. APE had the banjo bolt to bump boost, weltmeister and others shimmed the wastegate, but some were just chips with no boost enhancement (other than as a byproduct of better a-f and timing improvements).

Cyrus951

On an 89 turbo the stock is only 11psi?

hosrom_951

That is what i recon. Coz from 86~87 Porsche used a KKK26/6 Turbocharger and a single port wastegate (i think). But from 88+ The turbo was upgraded (changed) from a KKK26/6 to a KKK27/6 (larger compressor housing) along with a dual port wastegate. Boost pressure was kept the same (i think) but because of the changes made to the turbocharger and wastegate, more power was generated. Im saying single port and dual port wastegates because i know that there are differences, it may not be exactly what i meant by dual port, but there ARE differences.

Tom M'Guinn

Must be a slow day on rennlist. This kind of post normally gets a flood of response. Anyway, the 86, 87 and non-S 88 all used a K26/6. The 88S and the 89 used a K26/8. The 8 hot side pushed a little more boost up top. The K27 was not used on factory 944 turbos. All 944 turbos had the same wastegate, a single port design.

porshhhh951

pretty much exactly what Tom said. The k27 was never used on 944turbo's. The 88 turbo S and 89 car's did use a larger hot side(turbine ....NOT COMPRESSOR) which was 8 instead of 6. All 944 turbo's use a single port wastegate.

11psi is completely normal for a stock 89 car. The light going off could be alot of things. Is it just this light or do any other's go off as well(the emergency light go's off along with the oil light to tell you that it's oil) If the car is running normal and pull's it's prolly not a big deal. If you HG reading is only 10 then you DO have a vac. leak someone. Make sure as people already said that your new gauge is infact installed correctly and then start checking line's one by one. Unfortunately there are a ton of them so this might take a little while. Goodluck.

Danno

"On an 89 turbo the stock is only 11psi?"

Yup, from the manual, it says that anywhere between 9-12psi is normal for these cars stock. The non-S Turbos start dropping boost at around 4500rpm while the TurboS hangs onto max-boost a little longer and doesn't drop until 5800rpm or so. They end up at around 7-9psi by redline.

Also max-boost will typically be lower in the lower gears with the highest boost levels generated in 4th & 5th gears.

hosrom_951

Sorry, i knew that but got the numbers mixed up (i knew i messed up some where) Are you SURE the wastegates are the same? maybe not DUAL PORT like i meant, but there are differences right? either in mounting position or something....

Danno

Haven't noticed any differences in the wastegates. The TurboCup cars did have a wastegate with a narrower body, but the spring-rates and valve sizes used were the same. And they were all single-port wastegates.