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Boost creep

Boost Control

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I m building a 5cyl audi cepa engine with a G30 and tial 44 wastegate.

The problem is that without boost controler the boost pressure increase with the RPM.

I m wondering if the manifold can be the cause.

Picture of the manifold:


Hello just need a bit more information about what spring pressure are you using and what is the exhaust housing size and an approx horsepower at the wheels at say 3000 4000 5000 6000 rpm and what boost are you seeing at these rpm points. what is the ignition map numbers and what fuel are you using this will give me a better idea of a possible cause the more we know the better we can help

Regards Ross

Hello thanks for the answer.

I have 1bar springs and i would like to have 1b4 1b5 on all the range 3000 to 7000rpm for 500 600hp

I use E85 fuel.

For the timing map we put the maximum on the dyno but we start at 1b2 at 3500rpm and increase to 1b5 at 7000rpm with a mecanic control.

I use dash4 hoses for the plumbing of the tial 44.

For you do you think that the manifold have a bad design ?


Salut Jean Raoul!

Well, boost creep can be caused by a couple of things. Wastegate that is too small, bad manifold design, retarded ignition timing (acts like an anti-lag), dump tube design, to name a few.

I ended up having boost creep problems with a GTR last year, and it was a bad manifold design. I had to add a second wastegate to the manifold. One test I did to confirm is make a pull on the dyno without any wastegate installed. Be careful not to burn anything though! I ended up having like 12 psi of boost with the wastegate port open to atmosphere.

Here's a link to my post : https://www.hpacademy.com/forum/boost-control/show/boost-creep-on-rb26-single-turbo

Hope it helps!



thanks for the answer . Yes i see your post.

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