Sounds like the valve might be a bit open?

 

I had put in the pink spring which I believe is the lightest one, I think it came with the green one. Maybe its just too light for my setup? I'll try the green one tomorrow and see what happens.

 

Whatever spring you put in. Start the car and let it idle. If the valve is open/fluttering, then it needs more tension, so got a bit tighter. Keep doing that until it stays closed on idle.

If you do a big swing in the other direction then you might find it doesn't open quickly enough off throttle and you'll get surge. Better off starting loose and tightening in small increments.

 

I had gotten the plumb back version since I didn’t plan on doing any vta, but it doesn’t seem to have the adjustability that the dual port has. I think you can only change tension by changing springs or adding shims on the PB version. Now that I’m reading back to y’all’s comments I think you guys have the dual port. I’ll see if I can exchange this one to make things easier.

 

Y'all sent me on a reading journey lol. According to GFB the requirements for a SC bov are completely different since it's always "in boost" and the Kompact BPV is designed to stay open at idle, which is probably causing the CEL.

 

It’s all about dialing in the spring rate. You’ve gotta have something that’s adjustable. On idle the BOV recirc or VTA will be blasting air, at least partially. This also depends on your pulley. With the 100mm pulley, you can always hear the BOV venting into the intake as it’s forcing more air than the engine needs at idle.

 

Yeah, which means it's not like a turbo you don't adjust it to be closed at idle. That in turn could freak the MAF out. Best case is what Timboj is doing and convert to MAP for tuning.

 

The Turbosmart instructions state it should be closed at idle:

"With the engine at idle the exhaust port should be closed off by the piston – the piston should be hard against the seat and not floating or moving"

Makes sense as the engine is very much in vacuum, not "in boost".

 

This is from the Turbosmart instructions:

Makes sense as the engine is very much in vacuum, not "in boost".

This is from a log today. 95mm pulley. Over 4000rpm and around 20% throttle. The SC is still not providing enough air to create positive pressure.

 

From my experience using a proper BOV (Turbosmart Kompact Dual Port Pink Spring) and an improper BOV (HKS Stock). When the valve is too stiff and the motor is not at a load that can use the boost being provided you will get compressor surge. So at 4k 20% throttle you can still be at vacuum and still being provided boost. The boost is not able to be utilized because of 20% throttle so it is vented or recirculated. The easiest way to understand all this is just VTA for a while, you will hear exactly when the car is venting or using the boost.

You don't need to go through the trouble of converting to MAP just for this. You just need a BOV that allows you to dial in the specific rate that you need based on your pulley.

 

For the valve you have yes, for the recirculation only valve it says it will be open.

 

Somewhat correct but not absolute, few things to note there are different requirements for bov/bpv for superchargers. Turbosmart sells units specifically stating for superchargers, the Kompact is NOT one of them. You said it yourself, you still get some surge.

Most supercharger setup will be blowing off at idle,and off idle, that is problematic for people like Matt and I as we don't want a bov, we want a bpv, so we need to recirc that air at idle, which his valve is doing, and he's getting MAF codes.

Supercharger specific units

What GFB says about it as well

 

The Kompact Dual Port is a recirculating BOV and that is how I have mine set up. You can VTA or plug the VTA, or recirc via both 34mm ports. Or you can do a combo of both which I don't recommend. Matt's problem is he got the one that is not adjustable for spring pressure. The dual port is adjustable, you put the softest spring in and then you tighten it only enough to cover the O-ring. Now you recirc and you have no compressor surge. The valve will stay open at idle ensuring no surge and flowing back into the intake tube pre-blower.

 

Matt, I recommend looking into a Procharger valve, they have both recirc and vta.

 

Considering the spring pressure of the hks bov, it's got to be closed at idle and its pure recirc. I had assumed the plumb back version of the kompact would work the same way, but I didn't read enough, especially the part about being open at idle is how that particular bov is supposed to work, and my car did NOT like it lol. The dual port version, which they do include a block off plate to make it pure recirc like the original bov, is actually adjustable via turning the top. I did already purchase the dual port which should be here Monday or Tuesday. What I'll try is to get the new bov to have a similar spring pressure to the original, and if the car acts the same, I'll lighten the spring load from there. Working backwards here may get me closer to where I want it to be without having to deal with pissing off my motor and S/C.

 

I think recirculation is tripping some up here. Actual recirculation makes sense in a MAF setup where the relief is taking place after the MAF. Because that would be measured air and therefore helps driveability to have it added back into the air circuit.

The configuration for the HKS kit makes no difference whether you're venting to atmosphere, the intake or both, because the bypass is pre-MAF.

If you do pure intake venting (like the standard vent with the kit), you're adding additional air between the filter and the blower. If there's enough pressure the path of least resistance for that air is to push straight back out the filter. At higher loads that's exactly what's happening. On the other end of the scale it's probably momentarily negating the need more more air to be sucked through the filter.

This is why MAF/MAP/atmosphere/intake vent don't really matter for this kit. They will all work pretty similarly. However getting the right balance of spring pressure absolutely matters.

I actually agree that minor venting at idle should be okay within reason. That said, my config is proof that no venting at idle is perfectly fine. And that has nothing to do with my hybrid atmo/"recirc"

 

Let us know what happens, I know I'll be looking for a supercharger specific valve.

 

Then explain why he has a CEL then? I get what you are saying but as I said a while back, I don't entirely agree, I don't want the intake track open to atmosphere at ANY time, personal preference. If there are supercharger specific valves, that's what I'll be using, not a turbo valve, even if it "works".

 

Listen to this car, you can tell the valve is open even when cruising, and it has a very fast response time, that's how it should be. I just don't want the intake open so it will be filtered one way or another.

 

Oh and the other thing we've not talked about at all during this conversation is tuning. It matters.

Let's say for arguments' sake that in my configuration the blower is adding more air than the engine requires for idling at 800rpm, and I'm not venting any excess pressure. If nothing in the tune was changed, my engine would be idling high/too high. You could then lower ignition timing to reduce torque, which lowers rpm. So it's entirely plausible that my tune (which I do play around with a lot) is balancing a no-vent at idle scenario.

@dark I know we're going to agree to disagree on this, and I'm not trying to stir you up, but it doesn't need to be supercharger specific bypass. The function any bypass performs is relieve air, and in the case of the Kompact that I use and Matt will use, it can be dialed in to behave however you like (recirc/atmo/spring pressure). Unless there's some other function we haven't discussed/and I'm not aware of, I don't know what you'll gain from one?