Boost Control Issue
07-04-2010, 09:42 PM
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Boost Control Issue I run a hallman mbc with a 38mm ultra wastegate. I have 14#'s of spring in the gate. The problem is that at high elevation around 7k to 9k DA I can turn the boost controller all the way & can't make more than 15#'s of boost.
But when I'm at let's say 2k DA I can make more boost than I want, I've never exceeded 17-18#'s.
Does this sound like I need more spring in the wastegate? I always hear people saying that you can double the #'s of boost vs. the gate spring pressure but maybe it doesn't apply to a MBC?
I don't know how bad my back pressure may be. It is a small tc78 on a 346 with good heads. I run a 3' section of open down pipe.
But when I'm at let's say 2k DA I can make more boost than I want, I've never exceeded 17-18#'s.
Does this sound like I need more spring in the wastegate? I always hear people saying that you can double the #'s of boost vs. the gate spring pressure but maybe it doesn't apply to a MBC?
I don't know how bad my back pressure may be. It is a small tc78 on a 346 with good heads. I run a 3' section of open down pipe.
07-05-2010, 06:02 AM
#2
Yeah on my 97 talon originally had 10psi springs and couldn't really get past 20psi and am at 1900 feet here in Regina altitude. We can get density air days sometimes almost double that.
I went to 20psi base and went to 25psi in that car but didn't push past 30 but pretty sure could have. Goal was to be able to hit 40psi tops. Run turbosmart manual controller in that car.Blew clutch to hell and parked that car last few years so never did crank it up past 25psi.
On my 99TT running base 7ish springs and seem to hit that no problem but haven't tried to go double them yet. Have eboost2 though in that car. 38mm tial gates on each turbo.
Putting in 10psi springs shortly when install new LG turbos. Plan to go to maybe 20psi max with them.
Maybe its just that you can't get as much boost out of you setup at higher altitude.
You can do an experiment carefully. Unhook line to gate and see what boost level you can get too. I would have said also check for boost leaks and possibly sticking gate but at lower altitude you do hit higher boost levels. So don't think you have problem in those areas.
I went to 20psi base and went to 25psi in that car but didn't push past 30 but pretty sure could have. Goal was to be able to hit 40psi tops. Run turbosmart manual controller in that car.Blew clutch to hell and parked that car last few years so never did crank it up past 25psi.
On my 99TT running base 7ish springs and seem to hit that no problem but haven't tried to go double them yet. Have eboost2 though in that car. 38mm tial gates on each turbo.
Putting in 10psi springs shortly when install new LG turbos. Plan to go to maybe 20psi max with them.
Maybe its just that you can't get as much boost out of you setup at higher altitude.
You can do an experiment carefully. Unhook line to gate and see what boost level you can get too. I would have said also check for boost leaks and possibly sticking gate but at lower altitude you do hit higher boost levels. So don't think you have problem in those areas.
07-06-2010, 03:01 PM
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OK, I installed a 17# spring in there. It is 70 degrees today & it is hitting 16# of boost with the controller turned all the way out.
It will be a few weeks before I go racing in the mountains again so we'll see.
I am installing N2O also to see how it will work up there.
It will be a few weeks before I go racing in the mountains again so we'll see.
I am installing N2O also to see how it will work up there.