CSC boost limiter
Thread Starter
Launching!
Joined: Sep 2008
Posts: 225
Likes: 47
From: Dayton, OH
CSC boost limiter Part of my over the winter plan is to convert to dual fuel and have my V-3 Si rebuilt. Ceramic bearings, remove the oil slinger and convert to engine oiled and a billet Ti impeller and the inlet opened up accordingly.
I will run it on a sbe until I get the bottom end rebuilt with forged pieces, probably next year.
It makes 705 WHP on 93 + M1 at around 13 PSI of boost with a 3.4” pulley. I want to limit the boost to about the same level to start.
I know I can put a restrictor plate on the intake but would raise IATs.
If I put a wastegate with 14 PSI springs on the SC air discharge and leave the upper and lower ports open the wastegate should start to open somewhere less than 14 PSI and be fully open by 14 PSI, bleeding off the top end of the boost. If it opens too much too low I can up the springs to 15 or 16.
Also the wastegate may provide better control and adjustability than a restrictor plate. It would also moderate the exponential rate of boost increase that is characteristic of a CSC.
Has anyone done this successfully?
I will run it on a sbe until I get the bottom end rebuilt with forged pieces, probably next year.
It makes 705 WHP on 93 + M1 at around 13 PSI of boost with a 3.4” pulley. I want to limit the boost to about the same level to start.
I know I can put a restrictor plate on the intake but would raise IATs.
If I put a wastegate with 14 PSI springs on the SC air discharge and leave the upper and lower ports open the wastegate should start to open somewhere less than 14 PSI and be fully open by 14 PSI, bleeding off the top end of the boost. If it opens too much too low I can up the springs to 15 or 16.
Also the wastegate may provide better control and adjustability than a restrictor plate. It would also moderate the exponential rate of boost increase that is characteristic of a CSC.
Has anyone done this successfully?
TECH Fanatic
Joined: Dec 2019
Posts: 1,129
Likes: 478
Yes, people use wastegates to boost control supercharged setups fairly often. They typically do it for a very different purpose.
Why are you doing it? You have a belt driven supercharger. Boost isn't going to increase on its own.
Why are you doing it? You have a belt driven supercharger. Boost isn't going to increase on its own.
Thread Starter
Launching!
Joined: Sep 2008
Posts: 225
Likes: 47
From: Dayton, OH
Thanks for the reply. I am still learning about CSC's.
I am upgrading from Si to Ti and want to keep the 3.4" pulley to keep the boost response at lower RPM's but limit the top end boost until I rebuild the sbe with forged parts. I also want to experiment with moderating the exponential boost.
An Si pushes 287 CFM at 26,000 Impeller Speed and 1,150 CFM at 52,000
A Ti pushes 658 at 26,000 Impeller Speed and 1,323 CFM at 52,000
So with the same upper pulley you get 371 CFM which is 229% more air flow at 26,000 RPM (3,220 engine RPM) with the Ti but more than I want for now at the top end.
I am upgrading from Si to Ti and want to keep the 3.4" pulley to keep the boost response at lower RPM's but limit the top end boost until I rebuild the sbe with forged parts. I also want to experiment with moderating the exponential boost.
An Si pushes 287 CFM at 26,000 Impeller Speed and 1,150 CFM at 52,000
A Ti pushes 658 at 26,000 Impeller Speed and 1,323 CFM at 52,000
So with the same upper pulley you get 371 CFM which is 229% more air flow at 26,000 RPM (3,220 engine RPM) with the Ti but more than I want for now at the top end.
