Hmm.... boost spikes.... All stock.

[lamp3]

Hey guys, I'm running all stock and getting a spike to close to 10psi. This happens in 2nd, 3rd, or 4th gear. It only happend when im higher in the revs, and i roll into it until its and partial boost then nail it. It will shoot up to close to about 10psi the drop back down to 5 the back up to around 6 and hold. WTF?? Any ideas??

[ONRAILS]

Hey guys, I'm running all stock and getting a spike to close to 10psi. This happens in 2nd, 3rd, or 4th gear. It only happend when im higher in the revs, and i roll into it until its and partial boost then nail it. It will shoot up to close to about 10psi the drop back down to 5 the back up to around 6 and hold. WTF?? Any ideas??
Mine does the same... except I am at 8psi. I was told it was normal.

[KyRaceFan]

internal wastegates are crap, and just cant keep up with the sudden exhaust flow, and so it spikes a little bit.
Theres plenty of fuel for a quick spike like that, so dont worry about it ok?

[kwiktsi]

This is a good post for all the guys who try to blame spike on an MBC to read :)..

As for the gates, internal gate work in an effecient setup, having a tiny turbo on a 10:1 motor and trying to prevent spike is going to be difficult regardless of the gate. I have had a few 400+ hp cars using internal gates with dead accuracy- it is not the internal gate, it is the entire setup :).

Spike is caused by the delay in the time it takes the boost signal to travel to the gate and the gate to react- a 5 psi spring is a 5 psi spring regardless of the gate type- the smaller, faster spooling the turbos tend to "out run" the boost signal and pass the set point before the gate gets a chance to react.. The advantages of external gates are really no more than better flowing (prevents creep, not spike) and ease of adjustability (ability to change springs)
Joe



internal wastegates are crap, and just cant keep up with the sudden exhaust flow, and so it spikes a little bit.
Theres plenty of fuel for a quick spike like that, so dont worry about it ok?

[kwiktsi]

Oh yeah, you are partly right :), but small turbos on a high compression motor will pretty much out spool any gate.

Joe


internal wastegates are crap, and just cant keep up with the sudden exhaust flow, and so it spikes a little bit.
Theres plenty of fuel for a quick spike like that, so dont worry about it ok?

[lamp3]

Ya, I thought it was the turbo out running the wastegate. So I've ruled out vacume leak then I assume. Good to see your back to posting Joe. Always nice to get an opinion from someone we all know has their head on straight ;).

[KyRaceFan]

I was keeping it simple Joe, but yea your info as always, is dead on. :)

[kwiktsi]

Yeah, I knew what you were getting at- but a lot of people who might read this might not, so I just wanted to clarify :).
Joe

I was keeping it simple Joe, but yea your info as always, is dead on. :)