E46Fanatics - View Single Post - S54 custom turbo setup
View Single Post
Old 11-13-2012, 12:59 AM   #109
Registered User
Join Date: Dec 2011
Location: nc
Posts: 63
My Ride: 04 m3
Originally Posted by Cipri View Post
I use this car for drag so this is why I don't need full boost to soon.
In the wastegate I use the smallest spring 0.2 BAR.
Great build!! Excellent fabrication!!
Just my opinion on your boost. Your header is a very efficent design it directs the air at the turbo but not so much the wastegate. Your wastegate is opening before your max boost but the majority of the exhaust is just bypassing it from velocity of the air and going to the turbo. This is showing in your dyno. From your dyno I would say your wastegate is opening at 3500 rpm and from then on its creeping to your max boost. When running low boost these sort of problems occur as you go higher in the boost your tubo will start working off of pressure instead of the velocity. The wastegate becomes more of a pressure relief, then wastegate placement does not effect being able to control boost. This also becomes more of a problem when you run a larger more efficient turbine because this lowers the pressure in the header also.
To test this on your car you can use a ball and spring manual boost controller. Make sure to have race gas in it incase it goes high, fast, early.

To remedy this you can relocate the wastegate with the direction of exhaust flow or put in a second wastegate. It might help a little if you move your wastegate closer to the collector this will also decrease volume in the header and anytime you decrease volume in a header you have a great side effect of decreasing spool time.
The reason you get faster spool from less volume is when a exhaust valve opens it raises the pressure in the header faster and higher. The more volume in the header the slower the pressure will be raised.
A split exhaust housing reduces the header volume by half. That is if its on a split header with two wastegates one for each side.

I built a 22re toyota truck that would hit 14lbs or 1 bar at 1200 rpms. The header was a log design with very little volume. I also built a 302 with a small turbo but it was a v8. I kept the exhaust tubing small but since it was a v8 the volume was still too much for fast spool.

Last edited by turbotoy2791; 12-04-2012 at 08:26 AM.
turbotoy2791 is offline   Reply With Quote