Single turbo Impala still overboosting!
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On The Tree
Joined: Apr 2010
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From: Philly
Single turbo Impala still overboosting! Here's some info about the setup:
Its a 355 LT1 with a 60mm knockoff garret turbo.
The problem is that I'm still overboosting even after installing a 4.351lb spring in the tial 44mm wastegate.
I noticed that after installing the manual boost controller the wastegate wouldnt open up at all with the 10lb spring in it. I installed the smaller spring in it yesterday and now the wastegate begins to open around 5lbs but I cant give it more than half throttle with out it overboosting.
Is it gonna be up to the tune at this point or is it a mechanical issue?
Its a 355 LT1 with a 60mm knockoff garret turbo.
The problem is that I'm still overboosting even after installing a 4.351lb spring in the tial 44mm wastegate.
I noticed that after installing the manual boost controller the wastegate wouldnt open up at all with the 10lb spring in it. I installed the smaller spring in it yesterday and now the wastegate begins to open around 5lbs but I cant give it more than half throttle with out it overboosting.
Is it gonna be up to the tune at this point or is it a mechanical issue?
Thread Starter
On The Tree
Joined: Apr 2010
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From: Philly
I'm trying to post a pic of the wastegate location. For some reason it wont upload.
The wastegate is located just below the passenger side exhaust manifold. Its dumped and not recirculated.
The wastegate is located just below the passenger side exhaust manifold. Its dumped and not recirculated.
Thread Starter
On The Tree
Joined: Apr 2010
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From: Philly
The diaphragm looked good when I replaced the spring and yes I do have it refferenced at the lower port on the wastegate.
Before the boost controller was added the wastegate did open up right around 10lbs when I had the 10lb spring in it but if I pushed the throttle down pass half throttle the engine would over boost.
As far as the ball and spring, the boost controller was already put together when I bought it. I opened it up and replaced the spring with the supplied heavier tension spring after finding that the wastegate wasnt opening with the lighter spring.
Before the boost controller was added the wastegate did open up right around 10lbs when I had the 10lb spring in it but if I pushed the throttle down pass half throttle the engine would over boost.
As far as the ball and spring, the boost controller was already put together when I bought it. I opened it up and replaced the spring with the supplied heavier tension spring after finding that the wastegate wasnt opening with the lighter spring.
The only thing I was getting at with the ball/spring BC being hooked up backwards is that I would essentially become a check valve
If everything is hooked up correctly and the WG is sound then I would look to WG priority being the problem
Post some pics of where and how the WG is plumbed/mounted up
If everything is hooked up correctly and the WG is sound then I would look to WG priority being the problem
Post some pics of where and how the WG is plumbed/mounted up
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Teching In
Joined: Feb 2011
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The diaphragm looked good when I replaced the spring and yes I do have it refferenced at the lower port on the wastegate.
Before the boost controller was added the wastegate did open up right around 10lbs when I had the 10lb spring in it but if I pushed the throttle down pass half throttle the engine would over boost.
As far as the ball and spring, the boost controller was already put together when I bought it. I opened it up and replaced the spring with the supplied heavier tension spring after finding that the wastegate wasnt opening with the lighter spring.
Before the boost controller was added the wastegate did open up right around 10lbs when I had the 10lb spring in it but if I pushed the throttle down pass half throttle the engine would over boost.
As far as the ball and spring, the boost controller was already put together when I bought it. I opened it up and replaced the spring with the supplied heavier tension spring after finding that the wastegate wasnt opening with the lighter spring.
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On The Tree
Joined: Apr 2010
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From: Philly
You need to reinstall the soft spring in the mbc. The heavier spring will make more boost. The mbc will only allow you to raise your boost over your wastegate spring pressure. So I would remove the mbc and see if it lowers your boost. Also, make sure the top of your wasegate is vented. If the top port is blocked, it will cause the problem you are having.
I"ll be sure to swap the spring back out 2marrow and to make sure the wastegate isnt plugged.
does your boost controller have the vent hole in it? if that hole is even a little bit too big it will overboost.
check it with a compressor, and check it again with your hand on the vent hole
check it with a compressor, and check it again with your hand on the vent hole
Shouldn't the wastegate be located right at the turbo flange so it can vent pressure from both sides of the engine? Seems it is only venting exhaust pressure from the pass. side and the driver's side is going full bore right into the turbine housing.
People run there waste gate on one bank all the time over on performancetrucks.net all the time. The first thing u should do is take off the boost controller and run right off the spring.
Turbo match... What are the specs on that turbo??
A 60mm on a 355" engine, depending on the specs could be the cause of the over boost...And the 1 side w/g mentioned doesn't help, either.
Have you checked system back psi??
A 60mm on a 355" engine, depending on the specs could be the cause of the over boost...And the 1 side w/g mentioned doesn't help, either.
Have you checked system back psi??
Last edited by Old Geezer; May 9, 2011 at 07:13 AM.
Thread Starter
On The Tree
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From: Philly
It doesnt matter anymore becuz the wheel is f'd up now. My turbo sounds like a supercharger!
Time for a bigger turbo. I already have plans of changing the exhaust routing to the turbo.
Teching In
Joined: May 2011
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+1...this is correct. Run the gate on spring only to see if the compressor still wants to "overboost". If it doesn't, you have a boost controller installation or mechanical error. If it does, you have a wastegate issue.
wow this site is sad when people are advising him that his current gate position is satisfactory
and if you guys actually read the thread he says he was running with no conroller and he still couldn't go more than 1/2 throttle without overboosting
and if you guys actually read the thread he says he was running with no conroller and he still couldn't go more than 1/2 throttle without overboosting