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The mkiv Supra Owners Club

Overboost in higher gears


samdale

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Car is vvti TT6. It's been off the road for a little while, whilst I do some work to it, fitting BPU parts. The only one that should have made any difference in I've fitted a CW FCD. Cats are still in place currently.

 

Doing pulls in 2nd or 3rd gear seems pretty normal, both turbos coming online as they should and making ~0.8bar boost.

However if I try this in 5th or 6th I noticed boost increase to 1.2bar (where I let off). I thought with the restriction of the cats still in place this wasn't really possible? Obviously I'll be taking it easy until decats, wideband, BC and fuel pump are fitted but in the mean time, what's happening?

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It shouldn't be possible really. Perhaps your cats are dead, what other BPU parts did you fit?

 

If you've fitted a boost controller or any other boost control it will still goto 1.2 bar but the heat in the exhaust because of the cats will be extreme.

 

Usually fuel cut would protect you but as you've installed the FCD it wont.

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Car is vvti TT6. It's been off the road for a little while, whilst I do some work to it, fitting BPU parts. The only one that should have made any difference in I've fitted a CW FCD. Cats are still in place currently.

 

what's happening?

 

What was the other work? Only that the FCD won't have affected boost made, ie if it's boosting to 1.2 now with the FCD fitted alone before it was fitted it would have been hitting fuel cut, which you'd have noticed!?

 

Have you changed cat back since last autumn, tinkered with any pipes etc?

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Could be boost controller set up.. or boost creep?

 

My TT auto on low boost on the BC is 1.0 bar, fine in first and second but in third it will creep to 1.1 or 1.15 which I need to investigate. I have noticed the weather makes a difference too

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You read correct! No BC, just FCD and intercooler have been fitted so far.

 

Installed before my ownership is blitz NSR cat back, blitz turbo timer and an old defi link unit with boost gauge.

 

Edit: I've been plenty fast enough in it that I would have hit the original fuel cut pre FCD install.

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