Overboosting BAD! Arrg....

[Colza]

Its always been a bit of a problem. Previously it had been blamed on the amazingly efficient intake and exhaust, and a dump pipe that slightly fouls the wastegate flapper. Ive always had the feeling that these were just excuses cos i couldnt be bothered to find the real reason.

Anyway, with the new turbo now on (which spools hell fast and make the car generally haul ass!) the problem is now much worse. On the old turbo we ported the wastegate as much as we could to help stop the overboosting. The new turbo doesnt have the porting, and to double check that it is not any fault off the exhaust, i took it off and went for a boost fun!

With the exhaust off (ie. perfectly flowing exhaust and perfectly flowing wastegate) it still overboosts just as bad. Suggestions anyone?

It will boost normally to 10psi, then hold for a sec, then rapidly accelerate off to 15 and the fuel cut :-/

[crooky]

A hole in the wategate actuator diaphragm?

[Colza]

It happened on both the old turbo and the new, and i wouldnt have thought they would have been selling a reconditioned turbo with a faulty actuator. I am gonna take off the actuator bar and wire the gate open to see if that controls the boost. I have a feeling it is not going to help tho :-/

[civic_killer]

maybe you just a small hole in one of the vacumm hoses going to the turbo, and will only leak once the boost get high enogh? Just replace all the vac hoses and see, vac hose is cheap anyway.

[Colza]

Have established that all timings are coorect and there are no vac/boost leaks that i can find :-/

Ok, the current plan is to get my external on asap. I am still mildly concerned that i am covering up symptoms rather than fixing problems tho...

Any one have any thought/words of warning to add?

I mean when you think about it, an engine that makes lots of boost isnt exactly a bad thing... whether its supposed to or not

[city_cabriolet]

except the fuel cut part...

[Kam]

Try checking the throttle position sensor.  It might be out.  The previous owner of my car had the same problem and said that's what it was.  Dosn't make too much sense to me but it's worth a try.

goodluck
kam

[Bino]

The most common reason why a turbocharged car will over boost, is a waste-gate that's too small to properly control the exhaust gases.  In my mind, if you're going put on an external wastegate, that is the perfect solution to the problem.  I tend to doubt you'll be covering up any other problems, you'll merely be properly solving this issue.

This is just an opinion though
Good luck

[Colza]

I have just been quoted $450 for a new equal length manifold with provision for the external that leaves the turbo in its existing location. Sounds bloody awesome to me, so i think thats the way I will be heading unless something interesting happens over the next week or so. Cheers for all the advice guys ;D