could someone explain boost pattern to me?

[Davegtt]

What does this mean:

"Standard boost pattern is 10-8-10 psi"

I am sure the answer will be simplae and I will look a fool

Dave

[iaint]

The pattern for 1st turbo-changeover-2nd turbo

Basicall there\'s a slight dip in boost at ~4.5k RPM and the secondary turbo spools up.

Iain

[Davegtt]

Ahh I see, can the turbos be set to different bosst levels then? and if you have a bigger secondary turbo is the momentary dip a little more? I\'e 8 - 6 - 12 ?

Cheers

dave

[boltoa]

Only if you\'ve got a boost controller set to do it. By default, the ECU will control the turbo precontrol/wastegate such that the boost stays as close to 10psi as possible (except for post 96 models, which I believe go 12-10-12). Doesn\'t matter how big the turbos are unless you change the control.

Also, if you reduce back pressure by changing the exhaust system (catless, straight through, etc), the dip may not happen at all, or possibly spike - ie 10-12-10. This is when you can run into overboost cutoff problems.

For a very interesting website on how boost control works, see here.

Hope that helps

Andrew

[Davegtt]

Hmm interesting thanks mate, I have a pretty good indication of how vacuum controls turbos etc as I have a Gt Turbo at the moment and have changed the mass of hoses in favour of simplicity.

Interesting that you get a boost spike on free flowing exhausts.

Dave

[Davegtt]

wow, really good site! thanks mate