millband

Over the weekends driving through Wales (v.nice) I've started getting the "overboost" cutout problem (not so nice). It sounds like classic oil contamination of the sensor, as the oil level is a bit high at the moment.

I've read the FAQ, but I was wondering if anyone has any pictures of which bit to take off, and also what exactly is "brake cleaner from an aerosol"? Any other handy hints too?

Cheers,

Stephen

PS Yes, I'll do a search too...

Jon Brown

I've got a 97turbo and it has been fitted with the latest sensor that cuts out at 1.2bar. My car still over boosts, even after all the cleaning and oil level tricks. To solve the problem my dealer put a restrictor into one of the lines, to reduce the boost. It's a fine line between limiting the boost so the car doesn't cut out and going as quickly as possible. I've had the restrictor in the car for about 2yrs and it's okay(not ideal). It bugs me now and again to think that my cars producing more boost than I can use? What's the solution? Are there aftermarket parts that can sort this? FYI, the restrictor is a small round piece of plastic with a hole drilled through it. Smaller hole, less boost.
Over boosting must do wonders to engine mounts and the transmission?

millband

It's a total pain - I'm going to get the dealer to look at mine too. Have a look

AndyMc

Hi Jon

You say that a smaller hole in the restrictor lowers the boost,on my car it is the other way around.
The restrictor on my car is in the first hose just after the outlet of the turbo.The factory restrictor was 1.2mm and I changed it to 1.3mm. This lowered the boost on my car especially the peak just as the turbo spins up at around 3000rpm (which was where mine was overboosting).

This stopped the overboost but by 6000rpm the boost was down to 8-9psi 3-4 psi lower than with the other restrictor,I have now swapped back to the 1.2mm and have found that if I clean the restrictor and boost solenoid every couple of months the overboost stays away.
To clean the restrictor and solenoid I disconect the pipe on the outlet of the turbo and fill it full of gunk then go for a spin.

I can tell when a clean is due in a couple of ways.The first is that the peak boost around 3000rpm starts to rise, normally 14-15 but rises to 16-17psi, even though the held boost is about the same (13psi).
The other way is that the solenoid goes quiet,it normally clicks just above tickover

I have never had any trouble with contamination in the other pipe that runs from the inlet manifold to the MAP sensor

Hope this helps

Andy

PS I think most cars have a restrictor from the factory the dealers just change the size of it.
I tried a 1.5mm restrictor first and the peak boost was only 9psi and the car was well slow so its size is very important.

[This message has been edited by AndyMc (edited 06-05-2000).]

Jon Brown

Definately the larger the hole the quicker it goes. My car's a 97 turbo and my dealer swapped out the original solenoid and replaced it with a 3 way unit(1.2bar). The restrictor is in the pipe that exits from the centre(axially) and faces downward and inwards to the engine bay. I removed the restrictor the other day and it started to over boost(3k - ish). My dealer recommended brake cleaner or a similar solvent to clean the solenoid. Perhaps I'll try that again and see how it goes.

millband

Andy,

I'd like to clean mine, but as I'm a duffer I need detailed instructions! What do you mean by "gunk"? Also, where exactly do you disconnect the pipe?

Cheers!

millband

Well, a result of sorts. My dealer said they'd clean it out, but actually fitted a restrictor instead. Seemed to fix the problem (but I've not been far yet), wait and see if I notice a performance drop.

Mmmmm....