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I have a set of turbos from COSMO 13B RE, the seem identical to the ones from my previous FD. For this project the car is going to get a computer which can't run sequential turbos. So I need to convert them to NON sequential. I have searched far and wide and found much info about the conversion and the wastgate porting, but there is some conflicting information. Specificly it is what to do with the turbo pre controll. Some say to cut it out and plug the shaft hole, some say weld it open, and some say weld it shut.
What is the reasoning on this, anyone please?
The other question is regarding wastegate overporting. I have allready over ported the wastgate into an oval shape so that the stock flapper covers about 90% of the hole and cant get stuck in. This is well above the 75% rule, but I am wondering if anyone has replaced this flapper with a larger washer or possibly piston engine valve, if so it could be oppened up into a much larger oval withought removing to much structural material. Has anyone done this, and is it worth it?
I have also a question about the wastegate porting in an full non sequential setup.
My question is,why dose peoples say that u need to port the wastegate to give more boost in the lower rpm range?
And i have here a prob to get the gasget here in Germany if i would port mine.
Is anybody out there to get my the right infos about the wastgateporting and the needing gasket between the first Turbo and the exhaustmanifold on the Twins.
I have never actually driven a car with an over ported wastegate, my previous FD was ported right to the edge. But after reading this thread I did buy the book.
Any advice on the turbo pre controll, I have had one person say to cut it out on the no pistons forum, anyone else..
I can speak to this subject, since I've actually measured it. The turbo precontrol valve has a neglegible effect on flow. However, when the main (secondary) port open, flow will tend to come from behind the valve and circulate through the manifold in a reversed direction. I, personally, would leave it [the valve] closed as it appears to reduce the pressure at the turbine inlet when open.
Insofar as the overporting the WG is concerned, I don't think it is necessary and would not recommend it. Unfortuanately, there is much conjecture in the thread you cited. I would recommend the you cover the entire port (with exhaust valve material) if you want to have a decent spool. If you want to further increase WG capacity beyond the a standard ported one, add a radius to the short side edge leading into the valve making the floor as wide and flat as you can at the entry point. This will yield better results.