eyeball kid

Forgive the tyro aspect of this question but I'm troubled:

I'm in traffic this morning (ambient is 25 F) on 270 South Bound (aka hell) when traffic opens up before me to reveal a half mile of open road. I'm in fourth doing 60 mph and punch it speed climbs to 90 (theoretically speaking, of course) and boost gauge on dash hits 2 bar. Suddenly (like WTF was that sudden) the car seems to have snagged a carrier arresting hook, boost drops to 0 and if I weren't wearing a belt "Porsche Airbag" would have been imprinted on my forehead (receding hairline). Car gathers boost again and runs normally from that point on.

Stock 88 951 with LR Club Sport Wastegate and LR boost enhancer and new DV and vacuum lines.

So: What was that--It scared the **** out of me (no really, luckily I had a spare pair in my gymbag)?

And, given that it was (as I suspect) the result of some part of the engine doing its job i.e. dumping boost, what part was that?

And, is that a normal function of that part? I was on boost for like 3 sec. My vw 1.8t and Audi 2.7tt can boost for much, much, much longer. Is something malfunctioning?

And, if something is malfunctioning, can I replace it with a part that is a) outrageously expensive, b) made of billet aluminum, and c) located in a place where I can point to and explain to my already green with envy middle aged friends (You know this is really a cheap mid-life crisis compared to the usual slash and burn one's marriage thing) that this makes it go faster?

Thanks in advance

fbgh2o

Have you checked the intercooler hardpipe connectors. Based on my limited knowledge, you might have blown a coupler off... there are numerous posts about this happening to people here on Rennlist

Oops missed that part - sorry....

theedge

Yes, start with the couplers. Look or feel underneath them as well, in case you split one along the bottom. Also try to look at the long L shaped one that goes from the turbo itself to the passenger side hard pipe.

Jeremy Himsel

Sounds to be like it went into overboost / limp mode. Some carbon build up on the WG valve, sticky LBE, cold temps, or a malfunctioning cycling valve could have caused it to temporarily overboost. I'm assuming you have the stock chips since you didn't list it as a mod? You could have split a coupler, but if all is well again and it builds boost properly the I'm guessing that something stuck. I've had this happen with stock and Tial WG's.

jc in rb

factory overboost protection.back your boost enhancer down a turn or 2.my car does the same.stock chip right ?

eyeball kid

Yes stock chip. I'll check the pipes and back down the LBE. Just got back from driving it home and bumped it up against 2 bar without any repeat of the drama.

jlturpin

I have seen soldier joints in the dme cause similar, erratic symptoms. Like you turned off the key, no fire but fuel delivery continued. When the engine came back to life, the engine back fired and shot a flame out like the car should have been in a James Bond Movie. The car in questions belongs to a 30+ year Porsche Master Technician, factory trained who knows these cars inside and out. Once he repaired the DME soldier joints the car has not done this again.

This may not have anything to do with your issue and it may be a simple over boost protection, but I have never had it completely shut any of my 951's down for a few seconds and return to normal. When I have had over boost conditions with factory chips, I had to cycle the ignition for it to return to normal operation.

alxdgr8

+1 more for boost cut

333pg333

It wouldn't be the i/c tube/connections if the car went back to normal a short time later.

Rogue_Ant

Exactly.

Overboost protection kicked in...


-Rogue

eyeball kid

Does over boost always necessitate an ignition cycle? This was like BAM--there go the dentures then cruising along just fine seconds later.

Rogue_Ant

When the DME detects overboost it cuts ignition the same as over-revving.

Looks like it is time to upgrade your chips.


-Rogue

eyeball kid

I'm game for that, but is that the answer? Does overboost resolve that quickly or does it take an ignition cycle? Had it out again today and tried to replicate conditions and it did not happen. Gremlins? How can I shake this sense that something very bad is about to happen?

Rogue_Ant

The DME has to detect overboost for a certain amount of time before it shuts down...
As far as gremlins, are you up to date on the basic maintenance (timing belt, grounds, plugs / wires, cap / rotor, ect)?


-Rogue

eyeball kid

Yes to all except for grounds which I have not checked. Interesting suggestion.