Overboost protection - I think - Help please

[Hilux]

I went out for the second time in my new car [] and it was faultless until suddenly it cut out very briefly, like hitting a wall so I pulled off the d/carriageway onto a slip road and when at a tee junction it stopped. It started immediately and `seems` ok

I read somwhere (have searched but cant find) that this is an overboost protection? and cuts fuel if over boost is found? Correct?

Where did I read this and the solutions/fixes etc for it?



PS: the former owner said I shouldnt touch the throttle when starting it, is this true? (88 944 turbo)


PPS: whats the recommended idle for the above car please?



Thanks in advance chaps/chapesses

 

[Diver944]

Yes that does sound like the overboost kicking in. It will happen if on a standard car if you make more than 0.9 bar of boost for several seconds and is just the ECU cutting fuel to the injectors. It will reset if you switch off and on, or drive gently for a few minutes.

Look under the bonnet at the front of the engine and see if you have a boost enhancer like the one pictured below. You need to undo the red locking nut and then screw out the blue housing by one turn. Tighten the locknut and go out for a boost. Keep reducing it by one turn until the overboost does not kick in. You may find you have to loosen it over the winter with lovely cool air, and then tighten it again when the summer comes.

Yes, don't touch the pedal when starting, and the idle should be 800-900rpm

 

[danmason]

Yes, don't touch the pedal when starting

why is this? not that I've ever felt the need, just wondered.

 

[Fen]

Run it on Optimax if it isn't already; that lets you get a surprising amount more out of it as it isn't boost itself, it's knocking that cuts the spark.

 

[sawood12]

Did you have to stop or did you just stop in case there was something wrong?

When I first got my car I had a similar experience. Everything was fine afterwards but it happened again a couple of weeks later but this time I managed to look down at the rev counter to see it in the red so it turned out to be the rev limitercutting in. I was simply caught out as to how fast the revs can climb in a turbo when on full song. It's a testiment to how smooth the engine is cause in other cars i've had the engine starts to sound like it's being tortured before the rev counter gets anywhere near the red line.

Now I am much more used to the car I have avoided getting the rev counter into the red and i've had no problems since.

I believe that the loss of power in the event of the overboost protection kicking in is alot more violent than the rev limiter since it drastically cuts the fuel and puts the engine into a safe mode which can only be reset by restarting the engine. The rev limiter doesn't totally cut out the fuel and ignition, it just cuts fuel and ignition to one or two cylanders to prevent the revs getting dangerously high, but you can continue driving as normal once it's kicked in and the revs have dropped.

 

[Hilux]

this time I managed to look down at the rev counter

I know it was boost protection as 1) it wasnt a soft or hard cut rev limiter and 2) Having tracked westy`s and Ginettas I ALWAYS look at the rev counter as it gets to the red line unless I have a rev/change gear light (which I will be fitting soon on the r/h windscreen post) anyone fitted one on this forum? Does the EMS have a facility for this?

see if you have a boost enhancer like the one pictured below

I do have one thanks for the advice. I will mostly be playing with it soon.

Run it on Optimax if it isn't already; that lets you get a surprising amount more out of it as it isn't boost itself, it's knocking that cuts the spark.

Seconded, filled up today and it ran faultlessly and `seemed` to perform/pick up better. Mind you it was warmer too.


Boy I really really really love this car, its everything and more (and I`ve driven and owned a few very interesting cars) The handling and ride is truly sensational.

OFF TOPIC - Can you run on track days with slicks without adding baffles etc to the sump?

 

[Hilux]

Finally got round to doing this today.

Wound it out 1 turn, works fine, no overboost ........................however..............

It seems slightly slower, turbo lag seems marginally increased.

Before when it overboosted it really whistled round and pulled brilliantly, now (it may be me) but it doesnt `seem` quite so quick and the turbo noise is less of a whistle and more like a resonating whoosh.

Can you undo them too much?

 

[Diver944]

Yes it's a totally linear movement, so you 'could' turn it back half a turn if you want to, but then you'll start kicking yourself if you just trigger the overboost again during an overtake manouver.

Remember also that the air is a lot warmer now than when this thread started so you get less boost because of that also.

When I had a boost enhancer I used to turn it down in winter then back up again in winter [8|]