I have recently had a hayward and scott exhaust fitted to my 2000 Legacy GTB (tiptronic) and ever since this under full throttle at around 5000rpm there is a sharp break in the power for a fraction of a second causing quite a jolt down the drive train - has anyone any ideas as to what could be causing this?

Boost spike, maybe, followed by boost cut.

Did you remove the centre cats?
Have you got a boost guage fitted?

It should peak at around 1bar, hold steady at 0.9bar.

Anything sustained over that, boost controller gonna object.

Mark

Thanks for the reply. I haven't got a boost gauge fitted - is it easy to do/recommended? The new system runs from 'Y' piece backwards as one pipe with one rear silencer so presume the centre cat is no longer there - from memory the original centre section had two silencer boxes with a single silencer in the rear section. My gut feel is that there is two much boost - how can i limit /get over this?

Sounds to me that the centre cats have been removed, causing a spike.
As for a cure, not sure.

Join the 'legacyb4' group on 'yahoo groups', a wealth of knowledge there.


Fitting of a boost gauge is easy, if you use the 'vac' type, not electronic.
Instructions will be with it.

Mark

Many thanks for your response Mark. The legacyb4 site is certainly useful though i need to do a bit more work on it yet.

Interestingly i couldn't get Optimax at the weekend and filled up with BP superunleaded since which the problem has disappeared - how vital is it to run on Optimax???????

Best regards

Steve