overboosting

[pete]

recently bought 85 turbo most of the time turbo boost remains below 8 but sometimes on hard acceleration goes up to 10.Is that anything to worrry about. Is it ok to drive keeping boost low

[Dave Freeman]

Hi, Pete, not sure what the limits are on your model but over boosting can cause major damage to the engine. Suggest you take it very easy. Best get it sorted ASAP.

One of our other members should be able to advise, in the meantime best not to drive it hard.

Dave

[Trevsked]

I would say that that is far too much for the standard car which should be 7 to 7.5 psi I believe. Either the wastegate is sticky or the gauge is faulty. Either way you would do well to sort it pronto.

Trevor.

[dazmans3]

Hi

If I recall, The LC engine should be 0.5 bar. & the HC should be .75 bar (approx just under 10 psi) I am not at home so haven't got my notes ect handy.

You should have a mechanical overboost valve, located under the fuel regulator, set to approx 10 psi if I recall, so as long as that is working then you should be ok for now. If it goes off then you may hear a high pitch whistle. However if your wasitegate is sticking then would get that looked at pronto, as the Mech release valve is only a back up, to prevent damage to your engine.

The lower half of the External wastegate can be removed for inspection & cleaning up, most likely cause is rust inside the housing. Just something to consider is that the spring inside here could have been adjusted to increase boost. Also be careful of the Diaphram, I am not sure of availability of these now & can be eaisly damaged. They did cost in the region of

[pete]

how do you check out the gauge

how can i test if the gauge is faulty

[dazmans3]

I had mine Rolling road tested last year, which proved my gauge was showing close to what it should. You could get/fit a seperate boost guage, as a temp fit, to check the boost.

[cly_mitchell]

First you need to find out if you have an LC or an HC. LC's boost will max out at 8.5 psi, while an HC can take 10 psi. There is a pop off located on the plenum. It should pop off at 15 psi. Its is very easy to hear during full power gear changes. If your pop off is stuck or your waste gate is malfuctioning you could have an over boost situation. This will soon lead to a engine rebuild situation. That will lead to a wallet collaspe situation.

Cheers

Clay

[andydclements]

how do you check out the gauge

how can i test if the gauge is faulty

If you can find a decent mechanic with an accurate pressure gauge you don't need the car running to test the gauge, you can simply have the two linked up to a pressure fed supply, and if yours reads the same as a calibrated one, it's fine.

[pete]

thanks for that got a mechanic to try that on monday

[pete]

had gauge tested today and it seems to be reading all over the place . Do not know whether to try and replace it or put up with the old one

[andydclements]

Unlike the more modern ones which have warning lights to let us know something is wrong you will rely heavily on a gauge to tell you if the wastegate is doing its job. I'd say replace it, if you can't get / don't want to replace like for like then find a discrete place and mount an after market one somewhere.

[pete]

thanks for that think i will try the aftermarket route