V2 S-trim bov or bypass valve

I am installing a V2 s-trim this weekend and was wondering if they have a noticeable whine when under boost. I also see some guys running a bov instead of a bypass valve. I am using a blow through slot style maf. Which should I use?

You can hear the whine of them at idle, even though they aren't quite as loud as the v1. When you mash on the gas, it all depends on how loud your exhaust is if you will hear the whine over it or not. As for the bpv vs bov, they have different advantages.
BOV Pro's
1 It doesnt recirculate hot compressed air back intake the intake tract and through the supercharger.
2 Doesn't require a hose running to the valve to the intake tract like a bpv, which large hoses are sometimes hard to route without pinching them.
3 Usually outflow most bpv's given a quality bov versus a quality bpv.
Cons 1 Bov's create more noise due to the constant venting of air to the atmosphere until it loses vacuum signal and the boost is routed to the engine.You will hear a constant blowing noise at anything under hard acceleration.

BPV Pro's
1 Conversion of blow thru maf isn't needed.
2 The sound of constant air being dumped under conditions other than heavy acceleration isn't nearly as loud because it is being recirculated. It still can be heard because the amount of air being recirculated varies with engine rpm and sc speed.
Remember also, that a bpv can be used as a bov also. It can be setup to dump to the atmosphere just by not connecting the discharge hose to the air intake.
Most kits utilize a standard bosch type bpv. Its relatively inexpensive, at around 64 dollars from summit. It uses a 1 inch hose routed back to the inlet pipe. Im currently using the standard bpv, and even though its recommended only up to 12 psi, i see 15 lbs of boost without it bleeding off. As far as which you choose, its based upon your preference. Here is a junky vid of my car idiling in the garage, You can hear the supercharger whining faintly, but it is louder in person. Btw, my bpv is being vented to the atmosphere in that video also. [video=youtube;bUtaUGXVW0c]https://www.youtube.com/watch?v=bUtaUGXVW0c[/video]

How much boost are you going to be running? And why the BOV/BPV in the first place? Does the kit come with it or something? I would figure the supercharger already has a mechanism to re-route air when the throttle plate closes. Plus with a BOV, won't you be running rich with a MAF?

mcglsr2 said:

How much boost are you going to be running? And why the BOV/BPV in the first place? Does the kit come with it or something? I would figure the supercharger already has a mechanism to re-route air when the throttle plate closes. Plus with a BOV, won't you be running rich with a MAF?

Click to expand...

Most kits come with a bpv now days. Some of the old kits that made 5 pounds used to not come with them. Superchargers are spinning constantly, even at idle producing more airflow than what the engine needs. Thats why some supercharger engines surged really bad, they didnt have a bpv to vent the unneeded airflow. The bpv is referenced with a vacuum line, so when the engine is under light load or idling and the vacuum is high, it holds the bpv open and allows it to bleed off the pressure. When you mash the gas, engine looses vacuum signal and the bpv closes, reroutes the air through the intake and the boost builds. The bpv also lets the air divert when the drivers lets off the throttle, thus closing the throttle blades. If this uneeded air rushed into the closed throttle blade, it would be reverted into the intake plumbing, then the compressor housing possibly damaging the supercharger. As for the running rich with a bov, either a chip and a tune is needed to correct fueling issues along with larger injectors, or as in most kits, it comes with a fuel management unit. The fuel management unit (FMU), is also vacuum/boost referenced just like the bpv. When the fmu loses vacuum, it ramps up fuel pressure at a predetermined rate to prepare for the oncoming rush of more air.

Ah, okay. I would sort of expect a BPV for a supercharger. The BOV is new to me on superchargers - my experience is more in the turbo realm of things, and even there BOV's strike me more as a fad than a requirement. All depends on setup of course. So basically the tune/piggy-back is tricking the computer - meaning the computer measured more air, and it thinks it's getting it, but it's not, so the piggy back pulls back some fuel, even though the computer thinks it's giving the right amount.

I'm not sure how a tune fixes this without the computer tables themselves being boost referencing? Or at least changing to 2 or 3 Bar MAP?

Why run a BOV instead of a BPV as the system seems designed for?

When a tuner tunes the car, they will have a map sensor hooked up to the car, but its just part of the various sensors they hook up to it to aid in tuning. A tuner sc kit doesnt include the FMU, you are left to tune the car for additional fueling using larger injectors and a getting a tune. Also in the tuner kits, the timing curve is left up to the tuner to reprogram also and doesnt include a boost timing master that reduces timing based upon boost reference. The standard full kits, they include the FMU, which is boost/vacuum referenced to increase fuel pressure, which makes the injectors flow more than they normally would, compensating for increased airflow. Here are the main reasons for going to a bov. You have to remember, the bpv recirculates air. And air that has been compressed already, has been heated up which s going to raise your IAT temps. Instead of fresh air being drawn through the airfilter and the maf, the same air is just being rerouted back to the inlet of the supercharger. The higher the IAT's the less aggressive your timing advance can be without having detonation. Also cooler air is more dense, and creates more horsepower. Plus their were a few other reasons i pointed out earlier.

Thanks for the information!

I ran a bov with my SC..

I have the bpv that came with the charger. I will probably run it and see how it goes. I am not sure how much boost my setup will run. Going to try and get it all together this weekend.

If you are blow thru you can run either one. The venting has to be done differently. . If it's a draw thru you need to run a bypass valve. .

Here is the maf I am using [h=5]VMP Blow-through 75MM MAF housing and SCT BA5000 MAF sensor[/h]
How hard is this going to be to use since I am non-intercooled. I am also going to be using a stage 2 Snow water/meth system?

Depends on how you set it up.. I use vmp blow thru maf.. You have to have s certain amount off straight pipe for your maf.. maf can't be too close to your bov or bypass valve cus you'll get turbulance.. it's hard to say with out seen How to plan on running it.

Do you have any pics of your setup. I have some other guys saying that I have to go intercooled to have enough room for it.

I wish I had someone close who could help me with this.

Some are recommending I get a cxracing intercooler kit.

That's what I did. . Let me find pics...

If you are gonna run meth injection, I wouldn't worry about having an intercooler plumbed up unless you already have all the pieces to do it. Alot of guys run without an intercooler or meth injection, but they have to live with less aggressive tunes, which correlates to less total timing.

I would rather run without the intercooler. My issue is finding a place to mount my maf listed below. I have been told that I will not have enough room to mount the 75mm housing along with the meth injection nozzle and bypass valve.[h=5]VMP Blow-through 75MM MAF housing and SCT BA5000 MAF sensor[/h]