What can be done (if anything) to maintain boost levels as revs rise above 5K rpm.

Is this actually safe??

I have a MBC which helped matters, but boost still falls away above 5K.

Am I chasing something which I can't (or shouldn't) have

Cheers,

Marty

 

usual for the boost to tail off to save the engine..

Depending on the drop you are talking of course..

probably a drop of between 0.1 and 0.2bar is normal roughly depending on the year and whether remapped etc..

What boost is it running and what year is it?

JGM

 

It's a MY98 UK car with full de-cat.

I fitted a MBC, set to "just under" fuel cut (found by experimenting), but since then have fitted an FCD and managed to up the boost to about 16psi or so.
I have a Knocklink and get no signs of det' unless I hit the rev limiter.

It would seem that the MBC is about maxed out at 16 psi or so (or is it the TD04?) as the adjustment up to 15psi was quick, but the next 1psi took a lot of adjustment.

The boost has always tailed off towards the top end of the rev range...like you say, to save the engine (that's how they are set up I believe), but I just wondered if it WAS actually the same on all cars and if it was safe to do anything about it?

I think I read that on certain EBC's (Apexi maybe) you could set boost levels at every 500rpm. Will this be the case right up to higher revs..ie above 5K?

Just digging for info really.

Cheers,

Marty

 

Yes what you are saying is correct.. the Apexi will allow you to do that.

Or you could by pass the standard boost controller and just run the MBC so it would control the boost and therefore it would not tail off..

But you are risking the engine by doing that and you do so at your own risk.

I believe on the 97/98 ecu there is not much choice with remapping, replacement ecu only really.

The TD04 must be getting to its flow limit and is possible why you had trouble getting the extra 1psi.

JGM

 

The TD04 will allways tail off at higher revs as it cant physically produce the boost for those revs.
Another factor in it can be the wastegate can actually be opened buy the exhaust pressure at high revs,which can be counteracted by tightening the actuator arm by 1 or 2 turns to help keep it shut.
On my old scoob,tightening the actuator arm by about 2 turns helped me to keep max boost(set at 1.05bar) till about 6k revs instead of tailing off at about 5k.

easy