Hey there gents,

Specifically regarding a supercharged setup: Where is the best place to place the bov? Most people do it post IC before the TB. My particular situation is this: The KW kit has the BPV post-blower, basically right after the coupler, so essentially uncooled charge being recirculated into the intake pipe. I've seen a lot of people eliminate this BPV due to the flutter (it's too small, even VTA I've still heard the compressor surge on dyno runs). BOV eliminates this at the cost of it being loud and obnoxious any time you're not on the throttle and it's venting air (after a pull, cruising around etc).

What I wanted to do is still retain the recirculate function to hopefully alleviate some noise. My plan was to use a TiAL QRJ bpv with the large vband mounting flange welded onto the charge piping and weld a 38mm coupler to the air intake pipe as the -92 blower cannot use the normal KW elbow that has the recirc inlet molded in. So overall it'll be a much larger valve with larger vent ports; I'm hoping that will eliminate the surging and fluttering. I believe the stock fitting sizes on the pipes and BPV is 25mm, so 38mm is a 50% increase in size and airflow which will hopefully eliminate or minimize the surging to negligible levels.

Anyway the main question is where is the ideal placement for it to recirc? The KW piping has the provision on the pre IC charge pipe; I was going to cut that bung off and enlarge the hole and weld on the larger vband fitting for the QRJ. The only thing though is this will recirculate the uncooled charge air back into the supercharger inlet. Is this a big deal? Regardless I'll be doing some piping changes but I'd like to retain as much of it as I can, so if I can re-use the stock location without a problem I'd prefer that over relocating the valve to the post IC pipe. The other thing is it places the valve in a much more convenient location and a straight shot to the air intake pipe if I keep the BPV on the pre IC charge pipe as opposed to moving it over to near the throttle body. It would definitely look a little cooler in the engine bay to see the BPV more visible, but I'm not really after the aesthetic, in fact, I'd prefer not to see it if it's not a VTA blowoff valve such as the Q. Then this decision would be easy; I'd mount the Q basically pre-TB like this:

 

the reason for putting the bov between the throttle body and intercooler is not because its "cooled air" vs "uncooled air" it has to do with preventing the throttle body being slammed shut. when you let out at 9k rpms and the throttle closes it remains cracked just enough to idle, the excess boost pressure can push the throttle plate closed completely or more than it should even if for just a split second. by placing the bov closer to the throttle body it prevents this symptom. really you can put your bov just about anywhere and you'll be fine.

 

If your looking for a better diverted valve setup, I can verify that the forge diverted valve for vw & audi 1.8t setups is a direct plug & play into the kw kit.

I actually use the 1.8t adapters on my hks ssqov for my setup because of my love for bov noise

 

I have the HKS kit and i have fitted the BOV pre intercooler.

That way when cruising the hot dumped air will just get vented out of the valve rather than go through the intercooler and the air that the engine needs to use will be cooled by the intercooler. When you come on boost the intercooler will already be nice and cool and you will benefit from cooler inlet temperatures, i cant see the point of wasting the intercoolers capacity by cooling air you are then going to dump out of the BOV

I'm not sure if i go with the whole risk of it damaging the throttle body by having it before intercooler. When the BOV opens the air will rush backwards away from the throttle towards the BOV. Whats far more critical is choosing a BOV that is oversized so that it is easily able to vent the excess pressurised air. Fitting a larger vacuum line to the BOV also improves response

 

/\ what this man says

Only other point is that a correctly sized/located BOV also takes stress off the supercharger itself.. and that’s a good thing.

 

So specifically in a recirculated setup it would be ideal to locate it as close as possible to the blower for the above reasons. What I mainly wanted to know is it ideal to recirculate the hot air dumped from the valve back into the supercharger inlet? I'd imagine it would be well over 200+* F. I've looked into other supercharger kits for other platforms and they either straight up use a blowoff valve or they have a bypass valve venting to atmosphere with an air filter on the outlet. I'm sure in order for KW to sell and have these kits warranted by Rotrex their design needs to be reviewed by Rotrex themselves to ensure optimal operating parameters.

 

I retained KW location however i capped the port going into the hose for the supercharger so instead of circulating air back into the blower it dumps into the atmosphere

 

Quite simply dumping to atmosphere is the best option for many reasons.

If the hissing sound is to much for you, get a bov with a port and stick a small section of hose on it and direct it to the underside of the car.

 

I have done this on my car.

BOV points down towards the road but i found this kicked up loads of dust and covered the engine bay and air filter in no time. I attached a length of cold air feed hose to the BOV and then ran it so it blows out the side of the passenger wheel well. If you were really clever you could probably split the air and use it to cool your brakes. Although the air is hot it will still be alot cooler than the heat build up in the discs. It would be an interesting experiment to try.