voodoo51

I have not only hot start problem with my car.
Now it accelerate like naturally aspirated car. I see boost on the gauge from time to time but the car accelerate without kick.
The turbo seems to be ok.

What could it be?

mel_t_vin

Sergey, your hot start problem has been fixed, correct?

But now, you're down on boost? All the time? Has it always behaved this way or is this a recent problem?

What max boost does your in-dash gauge show during a wide open throttle pull to 6000 in second and third gear? 0.6, 0.4, 0.2 bar? As the accuracy of factory electrical gauge has been called into question on more than one occasion, it would really help if you purchased a mechanical boost gauge to give you a better indication of manifold pressure.

voodoo51

Yes hot start problem has been fixed.
I see boost increasing from 0 to 0,8 bar for example with open throttle.
This problem was all the time I bought the car. Sometimes gauge shows increasing boost sometimes not when full open throttle. But anyway there is no kick in acceleration at all

mel_t_vin

And you should see 0.8 bar at WOT in 2nd, 3rd, and 4th gear...that is the factory set boost limit.

So, if/when the needle does not move off its lower stop during WOT [0 bar], I'd expect the car to feel very slow/sluggish, as, in the absence of any boost, the engine essentially becomes naturally aspirated, operating at a [low] 7:1 compression ratio.

But, you sometimes see 0.8 bar on the gauge? And when you do, you feel a substantial punch in acceleration? Are you saying this is an intermittent problem?

voodoo51

Yes sometimes boost increasing on gauge sometimes not. When it does I don't feel any punch, the car accelerate slowly (as non turbo car).
The problem of showing the boost on the gauge is intermittent. And problem of slow acceleration is permanent.

voodoo51

I also need to buy ignition cable set. Could you please advice to me good manufacturer and seller of ignition cables?

Maybe this one?
http://www.fvd.de/de/en/Porsche-0/91...__930_-89.html

mel_t_vin

The factory electronic [boost] pressure sender is mounted to the front of the CBV [compressor bypass valve] assembly, located below the intercooler and to the left of the throttle body, and is reading boost pressure just in front of the throttle butterfly. It doesn't make sense that the gauge would indicate positive pressure [0.2, 0.4, 0.8] but you don't feel anything in the seat of your pants. While the gauge is known to be inaccurate [+/- 20%?], I would first replace your pressure sender [930.606.103.00] and sealing ring [900.123.106.30] and then look to install a mechanical boost gauge.


Again, the intermittent boost indication [without actual boost] is strange. The fact that you have very little to no boost can probably be attributed to one of several things: a) failed [open] wastegate, b) boost leaks [o-rings at compressor discharge pipe, intercooler inlet, and throttle body inlet], or c) collapsed exhaust/catalytic convertor.

Is your '86 running with a cat? If not, I would first test the wastegate for proper operation. If it is functioning correctly, then I would replace the 3 intake o-rings.

mel_t_vin

I suspect FVD/Brombacher knows a thing, or two, about Porsches [correct application, '74-'83 911, '75-'89 930]. That looks to be a very nice set of cables.

voodoo51

Bought this cables. Fit good.
We changed air filter and turbo is alive. But I still didn't feel kick and acceleration is very smooth

mel_t_vin

Sergey, have you driven or ridden in another 930?

If you don't feel a significant "kick" around 3500 rpm in 2nd or 3rd gear, you most definitely have an issue...low/no boost. This could be attributed to several things: 1) torn/leaking O-rings at the compressor discharge, intercooler inlet, or throttle body inlet, 2) clogged catalytic convertor/muffler, and/or 3) faulty turbocharger.

I would check things in that order. Good luck!

voodoo51

Allen I have never driven another 930. It's very rare car here...
Thank you for your help. We will check all in this order.

voodoo51

I also need to order heater control cables, because mine are rusted.
Could you please advise where can I buy them? FVD doesn't have them.

mel_t_vin

Sergey, here in the US, we [conveniently] have Porsche dealers in every major city. Most people order parts from Sunset Porsche in Beaverton, OR, because their policy is to sell parts at [wholesale] cost plus ~20%, whereas most other dealers sell at cost plus 60-80%, or more. Can you order from the States?

From what I recall, those rubber o-rings are not very expensive. It's been a few years since I replaced mine, but I think they were all in the USD $5-$15 range.

One more easy/quick thing to check before you start buying parts. You could have a failed/open wastegate. Could that, in itself, cause your no-boost condition? I'm not certain...but, it's very easy to check.

Start your car. Let it run for a minute, or two. Briefly put your hand near/on the wastegate discharge pipe going to the small muffler. This pipe should be cold, as there is no reason for the wastegate to open, and vent exhaust, with your car sitting/idling in the driveway. If this pipe is warm/hot, the valve inside your wastegate is frozen/rusted open, venting exhaust, at all times, around the turbine, preventing it from making [full] boost. Does that make sense?

voodoo51

Allen, thank you so much!
Yes, I can order from USA I hope.
We will do this test.

voodoo51

I also have an issue with shifting gears (first and second) after 15 minutes and more driving.
It is very hard to shift second gear when the car is hot. I have to push harder and more over it is difficult to locate the right path.

And when the car is cold it is almost no problem to shift gears. Just a little bit.

We tune the clutch twice but it didn't help.

What could it be?