Boost drop twin turbo
Thread Starter
Staging Lane
Joined: May 2014
Posts: 61
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Thanks Stevie, I think I'm getting close and I think they are sized wrong,
im seeing about 5psi back pressure, and when the gates open lose all spool, then boost comes back out the front, it happens at 7psi with 7 springs, 15 with 15 springs and 18 with 18 springs,
aside from being too big, I have a 6mm hose going straight to the wastegate, is this too big?
cheers Tom
im seeing about 5psi back pressure, and when the gates open lose all spool, then boost comes back out the front, it happens at 7psi with 7 springs, 15 with 15 springs and 18 with 18 springs,
aside from being too big, I have a 6mm hose going straight to the wastegate, is this too big?
cheers Tom
9 Second Club
Joined: Nov 2003
Posts: 13,616
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From: Norn Iron
6mm is perfectly fine.
And as said before, the only way air can come out the front of the turbo is if there is compressor surge.
If the w/g opens....which of course they will do it will happen gradually in relation to load/boost and this will never cause boost to blow back out the compressor.
And as said before, the only way air can come out the front of the turbo is if there is compressor surge.
If the w/g opens....which of course they will do it will happen gradually in relation to load/boost and this will never cause boost to blow back out the compressor.
Thread Starter
Staging Lane
Joined: May 2014
Posts: 61
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I only have 5-6psi pre turbine pressure with about 15psi boost,
Most things I read people are the other way with more pre turbine/lower boost.
Have sent the turbos back to the shop and he is changing the compressor wheel down to a 57mm and keep the 68turbine.
Can't see the back pressure gaining put hopefully stops the surge..
Thanks for your help stevie, hopefiully
Most things I read people are the other way with more pre turbine/lower boost.
Have sent the turbos back to the shop and he is changing the compressor wheel down to a 57mm and keep the 68turbine.
Can't see the back pressure gaining put hopefully stops the surge..
Thanks for your help stevie, hopefiully
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
It really depends on many things, but yes that is pretty low, could just mean your exhaust/turbine is very efficient given the engine size.
Which it probably is simply because you've a lot of turbine for a relatively small engine.
On mine, most of the time I've a pressure ratio of EGBP:MAP of 0.5:1 so EGBP is almost always lower than boost pressure.
There is no real reason you want backpressure to rise, you want it as low as you can get it.
Which it probably is simply because you've a lot of turbine for a relatively small engine.
On mine, most of the time I've a pressure ratio of EGBP:MAP of 0.5:1 so EGBP is almost always lower than boost pressure.
There is no real reason you want backpressure to rise, you want it as low as you can get it.
