Overboost fuel cut...

Does that mean it's broken?

No, it means it is working properly. Sometimes, with rapid throttle opening just off boost, the boost can build faster than the waste gate, and on a Saab, the APC valve can open. When this happens, the pressure switch that monitors boost cuts the fuel and spark for a second. Boost drops and gives you a noticable thump. You naturally back off.

A quick scary thump is marginally better for the engine than boost related knock, possible holed pistons, burned valves and blown headgaskets.

Has the boost been upped then? Surely there is no way it can be designed to overboost and have to cut off to the point of danger as standard...?

MR2 turbo had the same thing, you could increase the boost so much before it would cut in, some people removed it, it would also cut the boost if the engine wasn't warm enough to save damaging it.

Not modded in anyway, other than the factory intended aero tune which is=20 higher boosting than the standard 2.3 high pressure turbo.

The engine will take 20psi without head/piston/rod issues or mods.. Standard fuel cut is at 13.8psi, with standard boost somewhere arround=20

All a lot of the off the shelf staged packages do is raise the rev=20 limiter, raise the boost cut and play the fuel/ignition maps. Injectors,=20 etc are all good. Some people even just put a panel filter in instead an=20 induction kit and get really good results. Go with an induction kit and=20 freer exhaust and you can get huge benefits.

This is a speedparts stage 3 for the aero.

And Maptun goes upto stage 7

--=20 Carl Robson Audio stream:

Not modded in anyway, other than the factory intended aero tune which is higher boosting than the standard 2.3 high pressure turbo.

The engine will take 20psi without head/piston/rod issues or mods.. Standard fuel cut is at 13.8psi, with standard boost somewhere arround

All a lot of the off the shelf staged packages do is raise the rev limiter, raise the boost cut and play the fuel/ignition maps. Injectors, etc are all good. Some people even just put a panel filter in instead an induction kit and get really good results. Go with an induction kit and freer exhaust and you can get huge benefits.

This is a speedparts stage 3 for the aero.

And Maptun goes upto stage 7

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shame all that power is wasted through FWD though :(

I had something similar today in the Range Rover...

Still playing nicely, so nothing broken.

It's behaving impeccably.. scary really..

And now it is working, you are thinking of selling it for an LPG'd 4.2 Thought this one was a keeper.

Correct. The standard machine is wayward until you're in top gear on a wet road. :)

It's the Swedes trying to be sensible about things. :)

It can feel quite dramatic, but if you were to log the data, it isn't anywhere near as big a bump as it feels. Just as in most machines, you might feel the a/c compressor cycle in with a bit of a bump, but it makes almost no difference to the machine.

It will be a keeper if I can find a way of generating enough cash to properly LPG it, but I'd want a really good multipoint setup and underfloor tanks with a small reserve petrol tank. I had the tanks I want on my last gas Rangie, but they're worryingly expensive and unobtanium secondhand. This means I'd be looking at >£2k to gas it as I'd want it done and at the moment I just can't justify spending that much on it.

It's a bit of a quandry really, I've got it running really nicely, albeit with the boost backed off significantly. Also, it's a one off, so if I sell it I won't be able to replace it with another one the same, so my train of thought is to sell it for £2500 and find a really nice 4.2 with the LPG conversion I want (and have some cash to do the Czech trip I've been putting off for the last couple of months). Sounds weird, but after having one with that setup I really don't want to go back to having a huge tank in the boot as Range Rover boots are pretty woeful for the size of car.

I figure I can either continue running this until it's worth proper money (I don't think that's too far away), or I can buy a really nice

I thought boost cut in a Rangie would be it blowing a piston through the side of the block and leaving a puddle of oil so big the americans would consider invading it.

Fraser