I am using a stock 97 GN turbo, and wish to reduce the boost. I think I understand the logic of these controls, but want to tap your minds for further understanding. Right now it puts out about 8 lbs of boost. I wish to reduce it to about 5. Will putting a stronger spring on the waste gate actuator accomplish this? The actuator pot has two lines, one is manifold vacuum, the other is boost reference. Can someone elaborate on how these two interact in operation? Thanks.

Sam

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sounds like you have the push pull type of wastegate actuator. Putting a stiffer spring would in a sense add boost. boost builds against the diaphram and eventually has to overcome the pressure of the spring. so putting a stiffer one would add to it. Putting a lighter or softer spring would reduce the pressure. One could use a really light spring for say 1# of boost and then add a Manual Boost Controller (MBC) under the hood to adjust upward from there. An MBC acts like a controlled bleed valve so the pressure builds in the intake and goes through the line to the MBC, which bleeds off at a rate of 4#, add that to the 1# spring in the actuator and you would have 5# of boost. I hope it makes sense.
Intake-Hose-MBC-hose-Actuator.
Google MBC and you will see some of the setups in the pictures that should help a lot. Normally people use it to increase boost but will work to reduce as well if you use a lighter spring. Even an external helper spring on the actuator (to help open it) would also work but then you have to guess the boost with how much the srping helps reduce. Ill stop here as I will continue with more ways and only make it worse. Hope this helps.
Pohlman

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225, Offenhauser, Holley 350, A833OD, 3:55, GM HEI,99 Durango starter
BOOSTED! WH1C, BIG FMIC, 10#
Operation Noble Eagle 03-05
Operation Iraqi Freedom 05-07
Operation Enduring Freedom 12- 13

Why not get a manual boost controller? Like this: http://www.garage16.ca/ProductDetails.a ... e=FMICB051

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1965 Plymouth Belvedere II Turbo Project - SOLD
2002 Subaru OBS
1995 Lexus LS400 Race Car

The MBC is used to increase boost not reduce it. He needs to find a way to reduce it first (lighter spring) then go with the MBC. If it works out that he doesnt want to ever change it from 5# then maybe just the correct spring would work. As outlined in my first post, theres ways to do it but have to choose one first.

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225, Offenhauser, Holley 350, A833OD, 3:55, GM HEI,99 Durango starter
BOOSTED! WH1C, BIG FMIC, 10#
Operation Noble Eagle 03-05
Operation Iraqi Freedom 05-07
Operation Enduring Freedom 12- 13

Maybe I am not looking at this right, but the it looks like the spring is a compression spring that is compressed when the waste gate is closed. It looks like the spring assists in the opening of the waste gate. Now, maybe I have this backwards. It is an internal wastegate from a stock GN, and you cannot actually see it work. Maybe the spring is what keeps it closed, and I hve this all wrong, conceptually. I am going to try and find the article in the Grand National site that I used to install it in the first place. I used to have it bookmarked, but now more.

Thanks for the responses. For some reason my e-mail did not give me a heads up, and I did not realize the responses had come in.

Sam

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Another way to do it would be to change the position of the rod linkage. It's the rod w a nut and threads. W/out seeing it I won't say which way to turn it but if you adjust it the correct way then it will induce boost creep sooner and lower your boost overall.for numbers: boost builds, waste gate starts to open at say 5psi and is fully open by 9 psi. All based on the length of mechanical linkage. Change the linkage setting and it will start to open sooner. Hope this helps, otherwise I'll go looking for the GN site too.

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225, Offenhauser, Holley 350, A833OD, 3:55, GM HEI,99 Durango starter
BOOSTED! WH1C, BIG FMIC, 10#
Operation Noble Eagle 03-05
Operation Iraqi Freedom 05-07
Operation Enduring Freedom 12- 13

Thanks. I actually put the adjusting turnbuckle into that rod as the GN site suggested, and thought lengthening the rod opened the wastegate sooner. But that has been awhile now. If that is true, then the spring assists opening the gate. But actually, that makes no sense to me, logically. So I must be thinking backwards about how it opens.

Last night was band practice, and I have had no free time to go check it out. I did open the hood and stare at it if that counts.

Sam

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I found tons of these clips on you tube. http://www.youtube.com/watch?v=rogCn4AJYsY

It seems the spring does assist opening. So the trick is to make the spring stronger, or compress it more as this guy did. There are more, and I am going to watch them all.

Sam

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I bet some hardware store springs and trial and error can get you where you want to be.

Lou

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