Porsche Turbo Problems

[Mark Latty]

I have recently purchased a car from California(I'm in Canada), am fairly new to the porsche cars. Cannot get the turbo to work
properly. There is no boost but have tried the obvious such as
plugs, wires, vacuum leaks etc. Any suggestions where I go next?

There are no rpms over 4000...

[dyerkes]

Mark,

Just responded to your other post...I have a little bit more insight with this post. I would suggest you post your issue on the following website as well www.911turbo.com . There are alot of very astute Porsche owners there as well, but the website is totally dedicated to turbos.

The turbo has a cutoff switch designed to shut down the fuel pumps should the system overboost. If your absolutely sure that you truely have no boost, this should not be a factor. Can you describe in a little bit more detail what happens when your engine reaches 4K RPM. Do the engine momentarily stop, or does it remain flat that RPM?

Thanks,
David
1986 911 Turbo

[Jim Smolka]

Sometimes a clogged cat will keep it from developing the max HP. Does it simply not go past 4K, or just feel like there is no HP above 4K?

[Mark Latty]

Dave:
Thanks for your reply
The engine remains totally flat with no boost, it has a separate boost gauge in addition to the original one. The gauge for the boost is located near the intake bypass piston. I have checked the bypass piston spring and gaskets and replaced the gaskets. I thought I had the problem solved by the looks of the old gaskets, but apparently not.
Can you explain a bit more about the cutoff switch?

[David]

I'll second the recommendation for www.turbo911.com

It would help if you'd give us more info such as year, mods, does it have a cat, etc. Some close up pics of your engine compartment might help to see if there are obvious problems.

[Mark Latty]

This is a 1983 911 Turbo Carrera. Supposedly it is a 3.6 and the engine has been modified by Andial Racing in California. Not sure if it has a cat, never looked for it...I will try and get some pics to post.

It was supposed to be dyno'd at approx 400 horse about 6 months ago and a 1973 volkswagon could blow the doors off it right now!

[RussianBlue]

I fixed a 1977 turbo with similar problem.
But it sounds like your car has special mods...
First find out if the turbo is spinning and working at all.
Th problem on the 77' was a froze up shuttle valve, it's inside of all that tubing heading from the the turbo to intake intake.
Your 83' should have this part as well, and if it's frozen or sticking - you will not get any boost. The car will run like a very nice SC.
# 3, 4, 5, 6, 7, 9, and 20 etc on diagram[img]

http://forums.pelicanparts.com/uploads4/83turbo1101254334.jpg[/img]

Hmm not sure if pic will work, hang on

[RussianBlue]

Ok link works but you will have to magnify it some.
I would try this next.
If that does not work then I suggest selling the car to me for 3 or 4k

Ha j/k but let me know if that helps.
4|3X

[Mark Latty]

I just posted some pics of the car at http://www.pelicanparts.com/gallery/Mark_

[hobieboy]

Hi Mark,

It could be a stuck-open wastegate. But if you have no RPM beyond 4000, I think you may have a bigger problem. Does the engine not want to turn after 4000? Have you done a leak down/compression test on it?
Are you sure ignition & fuel are good?

[dyerkes]

Mark,

The oveboost protection is made up of two components: (1) a boost sensor which is screwed into the intercooler; and (2) a overboost relay located in the enginge bay fuse box (a yellow relay). I believe the stock sensor is rated for 1.2 bar, once it exceeds this limit it creates a ground and signals the overboost relay, which in turn shuts down your fuel pumps. But based on the fact that your vehicle doesn't seem to be building boost, its not the reason for your inability to build boost.

As others had noted the likely culprits are a stuck wastegate valve, or a non-functioning turbo, or a leaks in your exhaust, or leaking seals in the piping leading to the IC.

David
1986 911 Turbo

[carmad]

You may have a hole in the wastegate diaphragm, which is the black part in the picture, or the piston is stuck open. Check the wastegate with some compressed air on the connection on the side of the wastegate body.

[beepbeep]

Hole in wastegate diaphragm will cause motor to overboost and hit the overboost fuel-cutout switch, not limit the boost.


Check if your boost gauge is connected to right place, check for cracks/leaks, check if turbo shaft is free to spin (take off the intake hose and spin it with your fingers).

If you cannot rev more than 4000 RPM then you have other problems than turbo boost.

[Mark Latty]

Was in the garage tonight and checked the things that were suggested,
removed the wastegate assembly, checked the valve seat, diaphram assembly and spring. Everything was free and moving nice and clean, lubed everything up, but made no difference in the performance. It was also suggested that pressure be applied to the wastegate assembly to see if movement occurs, but seems ok.
Removed turbo pipes and spun the turbo freely, looks like everything is ok there also.
Checked the cat, but without the removal of the complete exhaust system i have not done this, is there an easier way to check, possibly with a vacuum gauge?
I have taken some pics of components in the engine compartment to see if anyone can determine what a few of the mods are for. One is an Andial computer modual in the dash and hooked up to a reostat and relay assembly which controls a fuel shut-off and a turbo gauge. Can anyone explain how this works or why it is there?
Also, there is a pic of the pressure line that is hooked to the bigger gauge for boost (gauge is working). Someone asked me where the pressure for the boost was picked up, its there in the pic.

[Mark Latty]

Forgot the pics in my last post....thanks for all your help...

[RussianBlue]

Check my first post and check your shuttle valve... it's a piece that never gets checked even at a rebuild.
It's in the 2nd pic you posted and in the diagram I posted.

Your last pic is of an aftermarket component desined to prevent triggring of the fuel cut-off in modified engines ie - higher boosted and quicker spools. I forget what it's called but it's not your problem most likely.

Keep us updated and goodluck!

[Quicksilver]

Simple suggestion. Try calling Andial. They will talk to you and they have records of the work that they perform so they might have an idea of where to start.

Also, does the turbo spin? The bearing could be frozen or a foreign object could be jamming it.

Wayne

[Tinker]

Mark,

Are the O rings and boots between the turbo and the intake in good condition and not leaking? MAke sure the intercooler is correctly seated.

The Andial box is probably a fuel enrichment device that adds fuel under boost conditions.

Are you sure this motor doesn't have a "dial a death" or adjustable boost knob somewhere?

I think you should be seeing some boost on the gauge prior to 4000 rpm even if it won't pull beyond that.

Tinker

[gsxrken]

I'm not even clear whether your car will rev past 4,000 or not.
Did you ever witness the car boosting before? What'd the PPI say in this regard? We'd love to help, but garbage in, garbage out...

[Mark Latty]

Hey guys
Just wanted to let you know that I found the problem. It was a plugged cat. A piece had broken off and turned sideways in the discharge and that's the reason there was no turbo boost etc.

Thanks so much for all your help. I couldn't have figured it out without your help.

Took it for a ride after finding the problem...It's a rocket !!!!