all of a sudden only boosting to 1.5 bar

[ERAU944]

on my way home today, the 951S only would boost to about 1.5 bar. the car is stock, with the exception of the bypass valve (which has been fine also, i just replaced it a few months ago). other than that, the car runs normally and sounds just fine, it's just down on power and it's only building about 1/2 a bar of boost.

any help would be appreciated!

[nynor]

how far up the stock gauge does the boost needle go? could be going into limp home mode, or you have a major boost/vacuum leak.

[Porsche-O-Phile]

"limp home mode".

Or a plugged cat.

Or a boost leak (check the clamps at the intercooler & intake).

Do you know the procedure using an LED on the test port to determine limp-home mode codes? I can dig it up if you need it.

[ae1969]

or the impellers on the compressor side are mangled to bits.............

That is such an uplifting thought.

[ERAU944]

alex - that thought makes me queasy!

i doubt that's it though.

i'm thinking it's a vacuum/boost leak - although i'm not certain. i took the air line off the bypass valve to test its operation (works fine), and drove it again - same thing. after that i noticed the vac line i had just moved was disconnected at the T near the fuel rail. i didn't get to test it again however, it'll have to wait 'till tomorrow.

thanks for the replies, i'll let y'all know what happened.

Mike

[ERAU944]

p.s. i doubt it's limp-home mode, my roommate's old '87 hit that a couple times when he had some overboost issues with chips he was running. the car builds boost, just not what it should.

[soxnail]

If you are getting 0.5 bar boost then the car will not display any "codes". Normally in limp mode the car only has 0.2 bar. That said if you are using the car's gauge to see the boost it may be hard to tell what its showing.
The first thing I would look at is exhaust leak/block preventing the turbo from spooling up. Of course I assume that you have done the "pinch line" test to see if the car makes proper boost or not. If it makes proper boost with the line to the wg pinched off then ignore my comment about the exhaust.
Sox

[nynor]

when my car shows 1.5 on the stock guage, it is building a little over 10PSI, which (i believe) has been validated as normal for this altitude. this is also within stock boost range. the boost range for the S model is the same for the non-S, it just holds it to red-line.

[Luis de Prat]

Hey Mike, it's been a while!

What about your cycling valve? Ever replaced it? Maybe it's leaking or not working right?

Nice seeing you again.

[Lawrence Coppari]

The 'y' you speak of also handles positive pressure that holds the bypass valve shut. Nice easy fix if that is the problem. There is another 'y' near the cycling valve.

[nize]

if the cycling valve fails, it will fail in 'open' mode, which would result in the same symptoms as cripple mode, making only .2bar of boost (1.2 on the stock gauge).

is your car stock? do you have LBE, banjo restrictor jets, or any other boost mod? what chips are you running?

[ERAU944]

i pity the fool!

well, today i FINALLY took the car back out of the garage. the weather's been decent enough to ride almost every day since i posted the question. it looks like the tube that had come out by the damper was the culprit, the car drives normally now.

Luis! good to see you again too, it's definitely been awhile. i think last time we exchanged PMs it was on rennlist... haven't been there since. in fact, i had just replaced the cycling valve, and maybe that's why the hose worked loose (from me monkeying around with the line). at any rate, good to see you again, if you ever need anything and you're in south florida, look me up! Email works best for me, i rarely check PMs, or the board. the motorcycles are just too fun to ride, and too fuel efficient to drive much anymore. hopefully that'll help me save up for some track time.

Mike

[ERAU944]

btw, nize, the car is completely stock, barring some exhaust leaks that one day i'll get to deal with