My S/C is HKS & doesn't have a BOV.
The other two popular S/C do have BOV, anyone know why?

When I let off gas, boost goes down but makes no sound (Not that I want
any , I like it to be sleeper), just curious if there's any design difference?
between BOV vs no BOV S/C?

I've been running FI for 8 month, everything is perfect, nothing broken, knock on wood.

 

haha weren't you curious 8 months ago?
i think it is because of the possibility of overboosting with a turbo, whereas superchargers are belt-driven

 

that's a wastegate's function

a BOV is to keep the compressed air from damaging the turbo when the throttle plate shuts and the air has nowhere else to go but backwards

the bypass valve on the vortech and ATI pretty much are there for the same reason

I don't know the HKS's design well enough to comment

 

makes sense. i thought the terms wastegate and BOV were interchangeable. my mistake.

 

There are many stock turbo cars with no bov. How do they not end up damaging the turbo?

 

Most have recirculation valve same as JWT.

 

HKS is a rotrex design and does not require one

 

I know, I just don't know it's piping and it's exact design as a kit

I've never seen one in person or an install manual or many detailed pics

 

Well, it's actually very close to a CSC so you COULD put a Vortech bov on it (would be an interesting project).

 

Well Im not for certain on this , but the HKS being rotrex design or not . It has to have a way of releasing the psi built up in the system . And it would be my guess that it does have a bypass BOV that recirculates the air .Thats why he doesnt hear any thing . Im sure you could put on a normal bypass valve on it .

I think the different design of the Rotrex is jn the gear box and how it build rpm . It has more than one speed that changes gears . How exactly it does it is not known by me for sure . I read about it , but cant remember the exact explination.

^^^^^ EDIT ,,,that is the new Rotrex SC...not avaliable here in the USA .

 

I'm reading through corky bell's "Supercharged!" It's a great book, I recommend it for anyone who's really interested. As far as the differences between a blow-off valve, bypass valve, recirc valve, and waste gate, I think it's more or less the following:

Blow off valve: as sentry said, it's used to release the pressure in the piping between the compressor and throttle when the throttle is suddenly closed and the compressor has residual pressure. This effect is worse from turbos more than SCs, because the SC will slow down rapidly with RPM, where a turbo has to "spool down."

Bypass valve/recirc valve (2 possible setups): when under vacuum, it opens and allows the engine to "suck" from the filter side of the compressor. (My truck had this setup). OR when under vacuum, opens a valve (like the vortech has) which vents excess pressure to atmosphere or back to the intake side of the compressor.

Wastegate (turbos only): controls the amount of exhaust flow through the turbo thereby limiting boost.

 

also protects the butterfly valve

 

Although it doesn't have a BOV, HKS S/C must have a by pass volve of some sort, I step off gas, the boost immediate drop to -20 PSI, same as idle.