96C4S

check all hoses.

Staffan

The fuel cut is violent, teath in the steering wheel kind of thing, scares you.
I clearly misunderstood the "bogging", I would say it's pretty unlikely that it is related to overboost.

Since you haven't done anything else than changing headers I agree with the others about checking the hoses.

I friends 964 turbo had a leak between the turbo and the intercooler and had the same type of behaviour. I had black puffs when I had a leak between the intercooler and the BOV (Blow Off Valve, located behind the intercoolers left side), who knows what happens with the metering plate when you have a leak, it could create black puffs, but not constant black smoke, do you have that?

Since the turbo had to come off when changing headers I would start looking at the hoses around the turbo. I would start there for sure.

If it turns out that it isn't an air leak and your mechanic has verified it's running extreamly rich and just dies from to much fuel at boost, then you could suspect that there is a problem with the WUR (warm up regulator, located below the intercooler to the right of the throttle body). But, there are two good arguments against that, first this is not what you want and second it's very rare with coincidences (spelling), in 98% of these sitiuations it's something that has been "fiddled around" with.

Vincent C.

if the intercooler was removed, make sure the o ring is seated properly and not hanging out on one side, also make sure the short hose off the divert valve is on the intercooler properly and the hose clamps are tight, the hose off the turbo must be on correctly as well....

Staffan

OP, keep us posted on your progres.
Read about a guy who had a car with a modified WUR, it bogged under boost.
He changed a spring in the WUR, this is what he wrote:

OK, so now back to the spring in the WUR. My on boost enrichment pressure was very low. I set it this way because of the power I had and needed the fuel up top. As a result I ran into a problem. On initial acceleration/boost it would trigger the enrichment. I knew I didn't need any enrichment until 4500 rpm's and running <8-9 psi. BUT, the ernichment was getting triggered at 4 psi (which is by the stock spring). I would bog like no other, and it was just horrible.

So, I put a stiffer spring (right around 8psi now) in the WUR to counter this, and it worked. No more bog at acceleration where I would run pig rich otherwise.

pnoob2

well i found out my car was running rich due to a popped hose between the turbo and the i/c . I have fixed it 3 times and yet it keeps popping off. my mechanic has suggested to me that I may need a new hose OR my waste gate is getting stuck open popping the hose off from excess boost. Either way it sounds expensive =( on top of that he suggested I install a Blow off valve to relieve the turbo of boost between shifts.

benzyne

I would recommend that you get a new mechanic as the one you have is giving bad advice. Installing a blow off valve is not a good idea since the 964 has a recirc valve which does a similar thing. Venting boost into the atmosphere will mess up the fuel mixtures since it is metered air. Read this post: http://forums.pelicanparts.com/showt...c+valve&page=2

If you are overboosting enough to pop the hoses off, then you should definitely confirm that your wastegate is functioning properly. If it is not then your new to you car will be bye bye very soon.

Find a good mechanic that knows 930 and/or 964 3.3 Turbos before your current mechanic royally screws things up.

fritz k.

+1
and in addition i would guess there is no need to change the hose because your problems should be caused actually by improper mounting.

if the hose pops off from the charger: there is small collar on top of the charger outlet. be sure that the clamp sits below that collar, it will fix the hose.

removing greasy residues from the inner part of the hose with brake cleaner or similar is helpful.

fritz

Staffan

Great news!
If the hose looks okay no need to change imo.
Like Fritz wrote, it's probably just a mounting issue.

Unless your fuel cut switch is grounded (which you want to check), that thing will cut your fuel at overboost, so that will tell you if you have a problem with the WG or other things causing overboost.

pnoob2

ok here is the update....the hose was taken off for me to look at ...and it does look like the turbo side is deteriorating the edge where the clamp attaches is crumbling so i bit the bullet and paid $400.00 for a new hose =( to test my boost levels , my mechanic tapped a boost gauge and noticed i was consistantly boosting 13lbs....which is around .9 bars ? That seems in line with my 1bar spring. So I doubt its the wastegate. Hopefully after the new hose gets in I am good to go. As for the blow of valve i will tell him to hold off on it then

Staffan

Overall it sounds good, your WG is most probably ok.
You might want to shop around next time, that hose should be less than $200 usd (still a crime though).

To test your BOV (which is, and should be of the re-circulating kind), drive the car in 3rd at 4.000 rpm, let go of the throttle, you should hear a "woosh" sound, if not your BOV is likely toasted.
I did a poll a few years back, the BOV is one of the parts that do break on these cars (about 50% of the cars), luckily an aftermarket BOV is not that expensive. Again, you want the re-circulating kind or you turn your turbo into a jet engine. I bought a Forge BOV, but there are others available.

pnoob2

damn where do you find the hose at $200? I searched everywhere and no one had it. apparantly it was the hose... the car runs PERFECTLY now =)

Staffan

Well that's great news!
$137 usd at FVD
http://shop.fvd.de/us/en/Porsche-0/9...arger-965.html