Thread: Wastegate size?

Control.

If you run a mid/large frame turbine with a small gate, and you're running low boost, it's harder to control your boost, therefore creep and spike are highly probable.

C'mon you should know this!

Sometimes I feel like the collective forum knowledge just takes a dive backwards a handful of years at a time.

Coheed, we've been over this.

Do we have to do it again?

I bet you won't do it! Here, let me do it for you...

http://www.sr20-forum.com/turbo/16477-basics-boost-control-wastegates-how-turn-up-boost.html

Actually that link doesn't have any info about wastegate sizing...
I don't know if I feel like searching for the threads on it though.

Okay this came up in the first couple of seconds of searching: http://www.sr20-forum.com/turbo/3208-wastegates.html
It's really odd that I never chimed in on that thread...
However, it is obvious by your first post in that thread (Cliff) that you've been paying attention. And post #4 by Fastspec2 covers the basics very well so Coheed you should read it.
Also javierb14 makes a great point in post #18 about wastegate priority and how that can change the required wastegate size.

With my SC6262 I will be running a Tial 38.

From fastspec2


I was being the devil's advocate here. Fastspec sums it up perfectly, the wastegate size can be smaller as the limits of the turbo are reached.

I am trying to provoke thought. Ideally you could run no gate, and make a ton of boost, up to the turbo's limits. But that doesn't necessarily mean you need a large gate on a turbo on low boost. I've run a 38mm tial on 3psi spring on a T67 turbo through, effectively, a 4.4L engine without ANY creep at all.

The only case you would ever need a large gate when running low boost on a large turbo, is if the turbine housing is sized to provoke boost creep. IE, small exhaust housing.

A small gate would control boost pressures until the flow capabilities were exceeded. For instance, running that 38mm tial on 3psi spring created ZERO creep. However, once boost was turned up to 9psi there was severe creep issues all the way to 16-17psi that were very difficult to control and tune. We ultimately changed exhaust housings to effectively fix the issue, so it did.

I wish I had a boost curve that could predict at what flow rate you would get creep, but unfortunately it is hard to predict until it happens. But it is a curve, and linearity cannot be accurately projected until you try it.

I honestly think that most people wont get creep issues unless the turbo is large, 500hp capable, and the wastegate placement is not ideal.

All that being said, my log manifold had terrible wastegate placement, but I never had creep issues until running over 25psi. At that boost level in 4th and 5th gear the car wanted to charge for 30+psi. But on low boost, this was never the case.

Just food for thought.

with my 60 trim T3 with the .82 turbine housing and tubular manifold i was running, i would have nasty boost creep with running my Tial 38mm, It had a 1bar spring in it but with the boost controller off it would hit 19-20psi by redline no matter what i did. It will sit at 14.7psi till about 6500 or so then rise slowly to 20psi by redline. It was a simple matter of that it was too small for the turbo i was running and the boost and power levels i was running.

Thats why with this 6765 that im gonna run i went to a 50mm Synapse wastegate. Ill probably adjust it to hit 18-19psi. It has full adjustment which is a really nice thing so your not having to swap out springs. Then use my electronic boost controller to go to 30-35psi maybe more. But you should have your spring set to the lowest psi you want to run.

Hey ashton, did you ever try running lower boost to see if you still got creep? I never had any issues with my 38mm creeping until running over 24psi. Seeing as how it would creep, I didn't feel it was safe for 100 octane anymore. Hence why all of my dynos have never exceeded 24psig.

Right now I have twin V38 wastegates for a total of 76mm of uber wastegate peen.

yeah with two, i would highly doubt that you have any creepin going on. As for the boost levels. Never went anything lower than the 1 bar spring pressure which again in the end would make 19-20psi by redline. It would be worse at lower levels as to run lower boost levels you would need to allow more exhaust gas through the wastegate to keep the levels down. So if it was doing that at 1bar and seeing 5-6psi of creep i would imagine lower levels would be worse.