I recently rebuilt my motor and installed megasquirt. I finally got megasquirt running very well and am ready to run more boost.
I have a tial 38mm external wastegate. I had the 8psi spring in... I changed it to the 1 bar (14 psi) spring. The boost remains the same.
I was under the assumption that a 1 bar (14 psi) spring would allow 14psi of boost and if I wanted MORE I needed a controller... Is that not true? The gate is opening around 5-6 PSI and I can barely get it to creep to 8 PSI...
Right now I have a single vacuum line running from the manifold to the side port of the waste gate.
#109712, "RE: Wastegate and Boost Pressure" In response to Reply # 0
Looks like an issue with the spring perhaps. Hook up a simple regulator to a compressed air line and test when the wastegate opens by adjusting the compressed air.
That will determine what is going on with the gate.
#109713, "RE: Wastegate and Boost Pressure" In response to Reply # 1
Originally posted by CODE4 Looks like an issue with the spring perhaps. Hook up a simple regulator to a compressed air line and test when the wastegate opens by adjusting the compressed air. That will determine what is going on with the gate.
I did that in the beginning of the summer and it was all good... But I will have to do it again.
Am I wrong in my thinking though? If I have an external gate with a 14PSI spring it should at least not open until 14PSI? Or will it open slightly while building and that allows too much pressure out?
I am also running directly into the side port of the waste gate and venting to the atmosphere out of the top port. It is my understanding the top port will only be used when using a boost controller.. correct?
This is the first time in 4 years of having the car turbo that I actually WANT the boost to go above 8PSI! haha
#109714, "RE: Wastegate and Boost Pressure" In response to Reply # 2
Is it possible that someone sold you the wrong spring? Were they different in size or color? I know the springs for my Tial wastegate have a little paint on them to identify the rating. The 1 Bar spring and 0.6 Bar spring are both blue. The 1 Bar one is larger though. You are correct that the upper port is only for the electronic boost controller. You can expect the wastegate to open partially before you hit its rated boost pressure. Every psi of boost tries to compress the spring further and open the valve further. It should hit a happy place and maintain boost pressure around its rating. Don't expect it to be dead-on though. You need a boost controller to really dial it in and minimize early opening.
#109715, "RE: Wastegate and Boost Pressure" In response to Reply # 3
Originally posted by Corbin Is it possible that someone sold you the wrong spring? Were they different in size or color? I know the springs for my Tial wastegate have a little paint on them to identify the rating. The 1 Bar spring and 0.6 Bar spring are both blue. The 1 Bar one is larger though. You are correct that the upper port is only for the electronic boost controller. You can expect the wastegate to open partially before you hit its rated boost pressure. Every psi of boost tries to compress the spring further and open the valve further. It should hit a happy place and maintain boost pressure around its rating. Don't expect it to be dead-on though. You need a boost controller to really dial it in and minimize early opening. Corbin '95 ESI-T Now with more power and fewer leaks Humble servant of the Wiki
After more driving and testing it looks like it is not the wastegate. I am definitely leaking boost right around the 5-8 psi range. I am going to check everything else out for leaks but I suspect it is the blow off valve.
I have a greddy type RS. I believe I only have the lightest spring in the BOV. I am going to find the other spring and see if that will keep it closed. I tightened it all the way to the "hard" side and it still leaked at about 7PSI and also fluttered.
#109716, "RE: Wastegate and Boost Pressure" In response to Reply # 4
If a brand name, aftermarket BOV leaks at all, I would check the vacuum line routing. If you get the routing backwards, it can open and vent your boost at WOT. Even the light spring should be fine for 7 psi.
#109717, "RE: Wastegate and Boost Pressure" In response to Reply # 5
Originally posted by Corbin If a brand name, aftermarket BOV leaks at all, I would check the vacuum line routing. If you get the routing backwards, it can open and vent your boost at WOT. Even the light spring should be fine for 7 psi. Corbin '95 ESI-T Now with more power and fewer leaks Humble servant of the Wiki
Hmm... I have a vac line hooked up from the BOV to the intake manifold... That's all there is to it... I don't think that is backwards.
#109720, "RE: Wastegate and Boost Pressure" In response to Reply # 6
At least on my Type S, there is an upper and lower chamber on the BOV. If you connect to the wrong one, it will open as boost rises. If the RS only has one port, then I don't know. Maybe a ripped diaphragm? That would leak air pressure out of the upper chamber and not resist the force applied by boost on the other side of the valve. With a weak enough spring, boost in the piping could force the valve open.
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