Boost Control Issue - need direction on next step

mblum

NOOB
Thanks for all the input guys, this will be my weekend project.

I have plenty of room around the DP puck, it's 1-5/8" OD. It doesn't locate perfectly centered around the wastegate hole on the turbo so when I open up the hole I will only remove material in the direction to help re-center it and not where it's closest to the edge.

One thing I noticed last night when messing with the STD waste gate is how easy it is to pull the push rod our to attach it onto the DP puck arm. With 2 fingers I can easily pull it 1/2". Is that normal for a STD gate? On the HD unit I can hardly pull it 1/8" with 2 fingers and that's with me trying not to let it slip from my fingers. I know it's not a very technical way to compare gate spring pressures but the HD gate is easily 4 time stiffer. Is that normal or is my STD gate weak?
 

Mr.Spool

Well-Known Member
One thing I noticed last night when messing with the STD waste gate is how easy it is to pull the push rod our to attach it onto the DP puck arm. With 2 fingers I can easily pull it 1/2". Is that normal for a STD gate? On the HD unit I can hardly pull it 1/8" with 2 fingers and that's with me trying not to let it slip from my fingers. I know it's not a very technical way to compare gate spring pressures but the HD gate is easily 4 time stiffer
Springs get weak over time.
 
Port the wastegate hole as recommended. Then, use the HD actuator with a spring or springs between washers on the threaded wastegate rod secured with double nuts. The springs counteract the heavy spring in the HD wastegate allowing for lower cracking (opening) pressures. Apply regulated air pressure to the wastegate and set boost levels to your liking by messing around with different springs and/or spring tension (moving the double nuts around). I was able to adjust the boost from my Bison 6266 to 14# - 32# with a modded HD wastegate.
 

mblum

NOOB
I wanted to post up my results.

Previously the WG hole size was .900" x .940", it was alittle obround, and was giving me the boost creep mentioned in this thread. From the searching I did it sounds like this is already bigger than the stock WG hole and whoever did it fillet the transition into the exhaust housing.

So I opened it up to 1.00" and put a smooth fillet around the transition of the WG hole to exhaust housing. I kept the HD WG actuator on the car and it took alittle adjusting to find the happy spot between the preload on the WG arm and the RJC MBC but I'm happy to say I now can go WOT with a stable 23-24 psi across the whole run.
Initially there was a bit of a boost spike when the turbo was spooling up before the WG opened but that has been tuned out. It spools really quick too🙂

This is where I wanted to be before putting Alky on it, I wanted my boost to be under control so I didn't have two things to be tuning at once. Once Alky is on I will turn the boost up more, but felt 23-24 was a good starting point.

While I had the exhaust housing off I decided to skim cut the surface the DP mounts to, it was pitted and noticed that the DP leaked alittle before. Took .006" to clean it up.
 

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