It's summer here and pretty hot. Seems my Comptech SC'd (no aftercooler, donations accepted) is continually pumping hot air back into the intake tract and causing the car to stumble if I apply throttle whilst cruising.

Today I remove the bypass valve from under the intake pipe and capped the flange (just used electrical tape for now). The valve is still on the end of the rubber hose but it now discharges compressed air under the bonnet.

I was surprised at how much air it was pumping at idle and also how hot it got when I gave it some throttle. I've got a 4", 8lb pulley so that just makes it worse. No wonder it was causing the engine to choke. Took it for a drive and the diffence was very apparent on a short run around the block. Long time testing will tell though.

I'm going to cap the intake connection properly and get a shorter hose for the bypass valve so it just sits under the pressurised side of the intake pipe.

 

I have the Vortech SC with AC, and as far as I understand it, this setup uses a blowoff valve that vents directly to the atmosphere.

 

That's right. The Comptech bypasses back to the intake. I assumed this was a CARB thing but isn't the Vortech CARB approved?

 

I live in the Netherlands so CARB approval is not an issue, but I agree it is marketed in the USA as being CARB approved.

 

I always thought that the fact that Comptech was carb approved was one of its selling points over vortech, but I may be wrong.

 

In the US the comptech has to be legal in all 50 states, the non aftercooled version I am referring. I believe because of california, it has a bypass valve. California I believe its illegal to blow off into the atmosphere, so the bypass valve makes it 50 state legal. In most states though the blow off valve could still be legal.

JP

 

I thought they were both CARB-exempt?

 

No.

The comptech recirculates the air into the intake. Hence its all good, anywhere.

I dont think the vortech is legal in cali, but I could be wrong.

AusS2000, you confirmed what Ive been suspecting for a while. Time to go to a smaller pulley, AC and a blowoff valve.

 

It is just compressed air, why can't you blow it off to the same place you got it? Not like you are blowing off exhaust or a mixture, what am I missing here?

 

I think what you are missing is the fact that these laws are set by bureaucrats (As opposed to people with intelligence).

You might find this goes back to the old days pre-Fuel Injection. In those days you would have the carburettor before the turbo/SC, so the pressured mix was fuel/air.

Either that or the sort of pollution CARB are concerned about is noise pollution.