Manifold companies need to focus on this stuff more. This is great info, I'm surprised I missed it.
There is always constant discussion about what is the proper diameter wastegate to get. Some say, "38's always work." Some say,"44 is the shit." And even some just say, "Hell, toss a 60mm on and you'll never have to worry!" Regardless of what they say, there's a reason behind it all. The proper wastegate size is all determined by how well your manifold is build, where your wastegate is located, and how it is placed.
First off, the point of a wastegate is to take exhaust flow away from the turbine. When you have a wastegate at a straight 90* angle, the exhaust flow tends to pass it by, and very little exhaust gases actually flow towards your wastegate. There are manifolds with 90* wastegate angles, but they have made it so there is more flow towards the wastegate by "tear dropping" the entry. Here is a Full-Race manifold for example:
The exhaust flow gets brought into the wastegate in a very smooth flow. Without this, the exhaust gases just pass by and create boost creep. The following photos, thanks to Full-Race, show this perfectly:
Even Precision knows their stuff (although their journal bearing turbos leak like a siv ). Here is what they have in their manual:
Hope this information was helpful
Manifold companies need to focus on this stuff more. This is great info, I'm surprised I missed it.
This is very valuable for anyone fabricating there own turbo manifold or are looking for a proper manifold for there build. Though I have always been a big advocate for running the largest wastegate that you can fit.
Definitely good information and definitely something most builders and fabricators miss or don't think of
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I'm glad you guys find this to be a good read. I really enjoyed reading this, so I had to post it.
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Loved reading this. I never even thought about the angle of my WG. Great info! I'm still pretty noob to turbo technicalities, so this will surely be a facepalm question, but....what do the spring ratings mean? Saybi have a 38mm WG with a 10 lb spring. Does that mean the WG opens at 10psi?
Pretty much exactly so it will open and dump exhaust once it reaches the springs psi /pressure rating and it is also the least amount of boost you will be able to run unless you get a 4 port I think with a 4 port boost solenoid you can cut the boost level in half to say 5 psi .I don't have one as of yet but am looking into them so I can run less boost in 1st and second and not have to back pedal so often .I run a twin scroll set up with 2 gates both have 7 psi springs in them and I love having twin gates as it doesn't creep at all up top and it spools insanely fast down low .
You are right, kinda. The spring pressure is the LOWEST boost you can run, no questions asked. A 4 port solenoid, or any solenoid/boost controller can never cause boost to be less than the spring pressure, it can only raise it. The nice thing about the 4 port, is that it can raise it a LOT above spring pressure. Generally a 3 port is good for like 2.5x spring pressure, so a 3 psi spring will top out at (on the high side) 10-12 psi, whereas the 4 port can make probably over 30 psi with that 3 psi spring.
Well I've actually been discussing running 2 three port solenoids to reduce the boost pressure and was pretty certain it was possible and thought a 4 port can do the same but I have yet to delve into this aspect of my build so I'm not certain yet .I am sure in the near future I'll have a good education on the exact workings of either (2) 3 ports or one 4 port but I hope it can be done .What you say does make sense though I guess I'll just have to do a little more research on it .I will say this I've def made over 30 psi with a 3 port and a 7 lb spring in the gates
trying to find it but on CRSX there was a manifold that was designed more for wastegate than turbo. Was a sick manifold.
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