Max Bar on a stock 930 engine

[Widebodycab]

I have a completely stock 930 3.3 engine.

Today I took it for a spin and reached 1.3 bar of boost.

Just wandering if that's normal for a stock engine and whether it should boost up more than that.

[T77911S]

NO!
you should have heard detonation from the engine. (pinging).

are you using the factory boost gauge.

verify the hose connection from the waste gate to the IC.
you should also have an over boost switch on the IC.

[Jeff NJ]

Stock boost is about 0.7 bar. With proper mods and gas, you can go higher (I am at 1.0bar), but the overboost relay should shut it down at about 1.1-1.2bar for your own safety.
So if it truly is all stock, your wastegate and overboost relay are not working and you shouldn't drive it on boost until you fix it, lest your motor goes boom.

Also, the boost gauge in the dash is often wrong, so don't rely on that.

[Widebodycab]

Right, so even the though the VDO gauge goes to 2.0 bar, the factory engine should boost between 0.8 and 1.0

There was no sound of pinging at 1.3.

Would it matter if it was a euro spec engine?

where would I find the overboost relay?

[Speedy Squirrel]

First, see if you have the overboost switch connected. It is in the upper intak, and looks like this:

Originally Posted by Widebodycab

Right, so even the though the VDO gauge goes to 2.0 bar, the factory engine should boost between 0.8 and 1.0

There was no sound of pinging at 1.3.

Would it matter if it was a euro spec engine?

where would I find the overboost relay?

[Les Paul]

What gauge were you reading that off of? If it's the aftermarket vdo and that goes in the clock hole they tend to spike. Do your pull in 4th with full boost.

[Widebodycab]

Originally Posted by Speedy Squirrel

First, see if you have the overboost switch connected. It is in the upper intak, and looks like this:

Good news! Yes I do have the overboost fitted. Identical to your photo

[Widebodycab]

Originally Posted by Les Paul

What gauge were you reading that off of? If it's the aftermarket vdo and that goes in the clock hole they tend to spike. Do your pull in 4th with full boost.

Yes it's the large full size gauge that replaced the clock.

the boost gauge figure was from 2nd gear. I'll have to try 3rd and 4th.

[turbo nut]

That is for the guage the overboost is a small one wire sensor

[Jeff NJ]

So the infamous yellow relay is the overboost relay, but I don't think it was on every year. If you have it, it is in the rear left corner of your engine bay, near the cdi.
What year is yours?

[turbo nut]

Mine is a 82 the overboost switch is in the manifold. Mine looked like a old vw beetle oil pressure switch (but it is not)

[Widebodycab]

This is the type of turbo on the car. I think it's a KKK31? Anyone know if this is the stock one?

[Widebodycab]

Correction. It's A KKK 3LD which tells me it's a stocker.

Good for 1.0 bar.

I'll see if I can find the over boost relay and go from there.

[Jeff NJ]

Originally Posted by Widebodycab

Yes it's the large full size gauge that replaced the clock.

the boost gauge figure was from 2nd gear. I'll have to try 3rd and 4th.

If you are actually getting 1.3 or more bar because the wastegate is failed and the overboost circuit is broken or disabled, I'm not sure that testing it in 3rd or 4th gear for a long pull at full boost is a wise decision.

Test your wastegate first. Can you regulate the pressure on your compressor down to 10psi or so or do you have a mitivac?

Test your overboost circuit too. I am sure that is detailed here somewhere.

Testing the accuracy of the gauge by potentially overboosting and putting holes in your pistons is not the best first course of action. IMO, of course...

[turbo nut]

This is the over boost sender

[Widebodycab]

So I can't see any yellow wire near the boost gauge sender unit.

Here is a photo of the CDI are.

Anyone tell me which one is the ivwrboost rwlay (if I even have one).

Engine is 1980 eurospec

[Widebodycab]

Thanks turbo nut

I found it!!

Now I'll work out how to an overboost test

[turbo nut]

Unplug it if it runs the system is not working. If that wire is unplugged it will not let the fuel pumps run. If it will not start that is good and if it is truly over boosting that sender is bad

[Speedy Squirrel]

I always get those mixed up. Thanks for setting things straight.

Originally Posted by turbo nut

This is the over boost sender

[mark houghton]

So many experts on here anymore that I can't offer much that hasn't already been suggested. Still, I'll say that 1.3 bar is waaayyy too much for a stocker. Short little bursts maybe...maybe, but not sustained. .8 bar is the stock setting for the waste gate to release, and a guy can probably approach 1.0 bar occasionally 'cause the good Dr. Porsche probably built in a fair safety margin. But don't push it.

So, three things: Either your WG is malfunctioning, your boost gauge is off calibration and you're actually only boosting to .8 (nothing new there), or some previous owner put a stiffer higher boost release spring in the WG. Since your overboost switch didn't trip and presuming it's working and not just shorted out, then you may not have overboosted at all.