BOV on a supercharger [Archive]

Blackcoog

07-31-2007, 09:07 AM

Anyone ever heard a BOV on a supercharger? You'd only see this on a blow through setup and you'd only run a blow through setup if you had issues moving the MAF before the supercharger. Since I'm running a blow through setup I have a BOV.

Normally on a turboed car you hear it release pressure for a split second when you let off the throttle. On mine it dumps pressure at the same time but since it's a supercharger and it's being run off the belt the supercharger continues to pump so unless you are under 2k rpms it continues to hiss the entire time if you continue to decelerate without putting the clutch in. It's kind of neat but also kind of annoying if you want to drive it daily and stay someone unnoticed. My wife said it sounds like a snake. :rofl: I think the sound is amplified because it's in the fender well area behind the bumper. I may pickup a bypass and run a tube down under the car so I can't hear it as well. For reference I have an Apexi dual chamber BOV.

ModCougar

07-31-2007, 10:09 AM

Hmmm...that's pretty cool. I bet it would get annoying though.

PREDATOR

07-31-2007, 10:20 AM

Hmm... weird :crazy: I know what you're talking about but I've never seen anything like that before.

FastCougar

07-31-2007, 10:25 AM

Why not go with a recirculating valve? Sure, you don't get that moster BOV sound when you shift, but it would be even more of a sleeper then and it's daily driving delight.

cvsmightymouse24

07-31-2007, 12:56 PM

Yeah i agree with trevor.....running 100% atmosphere is annoying and gets old after awhile. Put a recycling tube on and the sound will be decreased by a lot!!!

Blackcoog

07-31-2007, 01:07 PM

FastCougar

07-31-2007, 01:28 PM

I don't think you understand...there is no place to recycle the air to. Reference the pictures on my site: 3L Duratec (http://www.3lduratec.com/supercharger.html)

The air should be recycled after the filter before the supercharger, but the filter is bolted to the supercharger so that isn't an option.You know, I was thinking that right after my reply. Why not divert it, like a waste gate setup and run some tubing down behind the engine and out the back of the car. At least that way, the sound won't be right under the hood. The majority of the noise from a BOV comes from the shape of the exiting orifice. Relocating this orifice much farther back with some tubing will dissipate the sound considerably. Not to mention, what sound is generated is now being exhaled somewhere than in front of the driver, so it will be much less noticeable.

Clutch

07-31-2007, 03:58 PM

This isn't related but reminded me. You can now run a wastegate on a supercharger. A magazine i subscribe to had a guy cog his supercharger for 20 something pounds and put a wastegate on the supercharger to limit the air being compressed, he reached peak hp and tq faster because the supercharger was spinning faster from the start but then doesn't rise until you adjust your wastegate/boost controller.

Dom1013

07-31-2007, 04:10 PM

since it's a supercharger and it's being run off the belt the supercharger continues to pump

...I wouldn't see a turbocharger being any different, don't think the compressor on it stops spinning completely in between shifts either...im sure it keeps moving air also, should react the same logically when u let off the throttle:shrug: but I'm sure there's gonna be some difference in the two. Second, I love the sound of boost and anything related to it, it will never get annoying to me, and if it does my system could always drown it out...

AndyMan

07-31-2007, 08:55 PM

..... :disgust:... i want this right now

PuckPuck

07-31-2007, 09:06 PM

I heard of a setup (never seen it though) where a recirculating BOV was used as a make shift wastegate. Essentially after xxx #s of boost, the BOV opens up and recirculates between the filter and the SC. This allows you to run a smaller pulley for boost at lower RPMS, while still maintaining a workable boost limit.

The downside for you is you would need to build a 3-4" pipe for the filter to hook into, and recirculating tube. Also I would imagine that this type of setup would put far more wear on the SC itself and the bearings wouldn't last as long as with a larger pulley

Drewmanfu0

07-31-2007, 09:15 PM

Maybe I overlooked something...But why not move the MAF so its a suck through?

FastCougar

07-31-2007, 09:34 PM

Maybe I overlooked something...But why not move the MAF so its a suck through?Absolutely no room for it ... if you could even lengthen the wires to the other side of the engine bay.

Blackcoog

08-01-2007, 07:52 AM

Absolutely no room for it ... if you could even lengthen the wires to the other side of the engine bay.

There is a slight possibility of running a very sharp bend straight down through the washer tank hole but the discharge piping is also in the way so it would be a huge pain in the azz. Eventually I may try to figure something out.

papatedroach

08-03-2007, 09:36 AM

what about attaching the maf right to the supercharger inlet, cutting a hole and running a very short pipe through the inner fender, and stick that dome shaped filter you have inside the fender?

Blackcoog

08-03-2007, 10:49 AM

Just about the only room currently in the fender for a pipe is being used up by the discharge pipe. There are supports for the fender if you try to go straight out from it. Not to mention it's a 3" pipe instead of the 2.5" pipe which barely fit for the discharge tube.

warmonger

08-07-2007, 03:29 PM

Use a standard bypass valve and use a nice polished 1" aluminum tube and stick it right through the end or even the side of your air filter. If it is K/N type or foam type you should be able to seal it to the filter and make it look good anyway. That way bypassed air dumps right back inside the filter to muffle it and outside air still has to be drawn through the filter.

Blackcoog

08-22-2007, 08:08 AM

I'm looking for a bypass valve now so I can quiet the car down. Any idea if there standard bypass valve will work for my application?

SuperchargersOnline.com :: Product: Bosch By-Pass Valve (Black, Direct Replacement) (http://www.superchargersonline.com/product_detail.asp?PartNumber=SODC-BP1)

They even sell a kit with this bypass but it's a bit over priced for clamps and hosing:

SuperchargersOnline.com :: Product: SCOL By-Pass Valve Assembly (Black, Universal Kit) (http://www.superchargersonline.com/product_detail.asp?PartNumber=SODC-BP)

It sucks that I have this niced polished unit currently and have to switch to this unit above. The one I have now is an Apexi Dual Chamber BOV (http://www.raceinspired.com/pc-662-23-apexi-twin-chamber-blow-off-valve-universal-all-cars.aspx) and it blows off in all directions and if it were in any other location than the fender well it would probably be fine. Oh well maybe I can put it up for sale and get something for it.

gamiller

11-02-2007, 01:14 PM

Like Blackcoog, I'm considering whether a bypass valve (BPV?) would serve me better than a blow-off valve (BOV). Any comments from those using BOVs? For those who aren't aware, the difference between them is whether the excess air is recirculated or vented to atmosphere. In my case, my A/F pegs rich from the time my BOV opens until I again open the throttle. I think this might be the reason I am getting CELs/DTCs for System Too Rich; the engine computer is being fooled by the BOV. The PCM has already calculated the amount of fuel needed to mix with the amount of air metered by the MAF. When most of this metered air is vented to the atmosphere by the BOV, the PCM is left with only one resort: modify the fuel trims in an attempt to bring the air-fuel mixture back to stoichiometric.

FastCougar

11-02-2007, 02:29 PM

I have the TiAL 50mm BOV and I can only hear it ever so slightly ... not annoying AT ALL. Gary, have you watched the video in my sig yet? I shift twice during that run and you can't hear the BOV at all. Matter of fact, I can here my wastegate flutter more than my BOV. It's a great setup ... I love the TiAL stuff!

gamiller

11-02-2007, 02:37 PM

FastCougar

11-02-2007, 02:49 PM

The "rich condition" last miliseconds and I'm sure isn't hindering power at all. If anything, it helps cool the combustion chamber.

Blackcoog

11-02-2007, 03:01 PM

My case with the BOV is different as my BOV is before the MAF. I have no issues with dumping air. My BOV definitely isn't quiet though. I think my setup is louder because the BOV is in the fender well area which amplifies the sound.

Unless you would rather keep the sound of the BOV a bypass valve should keep your air/fuel in check. You should pick up one of those BOV that can also be used as a bypass valve so you can test your theory.

gamiller

11-02-2007, 05:54 PM

The "rich condition" last miliseconds and I'm sure isn't hindering power at all. If anything, it helps cool the combustion chamber.

Yes, the BOV is open less than a second, but my A/F pegs rich for several seconds afterward - until I again tip the throttle. As I explained, this is only to be expected when all the air for which the fuel was metered gets expelled.

Q: I installed a blow off valve, it sounds really cool but my car stalls when I let off. Why?

A: First of all, the reason this is happening is because the Air Flow Meter on our cars measures
the air coming in through the flapper door. It senses this air and adjusts the fuel mixture
accordingly. When you let big rush of air out of the intake system, you are letting out a
bunch of air that was just measured. The fueling will still dump the fuel associated with
that air and cause an over rich condition. This will cause your car to stall momentarily or
in some cases actually turn off. Once the BOV has closed and the intake system will return
to it's normal state and work again.

Blackcoog, I might test out my idea, but I was looking for confirmation of my suspicions. The way I understand things, if I was to recirculate the air, it would have to be re-introduced after the MAF but before the turbo.

gamiller

11-02-2007, 06:22 PM

Looks like TurboXS makes bypass valves in addition to their lineup of blow-off valves. Maybe I can swap mine out.

Racing Bypass Valve Type H34 vents excess pressure back into the car’s air intake making the valve ideal for Mass Air Flow (MAF) metered cars where venting to atmosphere can create a "rich" air/fuel ratio right after the valve goes off. The Racing Bypass Valve Type H is CNC machined out of billet aluminum and brass. Valve operation, while louder than most stock valves, is quiet compared to a BOV that is vented to atmosphere like our BOV-H or BOV-H-RFL. The RBV-H34 comes standard with a 34mm OD anodised aluminum hose adapter for the inlet.

FastCougar

11-02-2007, 06:42 PM

Gary ... I'm not sure how a diverter valve vs. a blow off valve would help your problem. If the TB is closed the car is running rich for an extended period, recirculating the air BEFORE the TB will do nothing for your rich condition ... UNLESS, you have your IACV feed line routed incorrectly. In my setup, my IACV feed line is placed BEFORE my BOV. However, thinking about it, if it's place AFTER your BOV, the engine would run rich because the air that should be reaching it is now being diverted through the BOV. So, my question to you ... how is your IACV line routed ... pre or post BOV?

gamiller

11-03-2007, 06:39 PM

So, my question to you ... how is your IACV line routed ... pre or post BOV?

I'm not aware of an IACV line in my configuration. I'm using the 3L UIM, so my IACV is atop the UIM, just after the TB. There is a chamber, I think, where the TB mounts to the UIM that is used by the IACV. From memory, the only line I have connected to the intake side of the plumbing is the valve cover breather line, which is just before the turbo.

FastCougar

11-03-2007, 08:14 PM

Ahhh ... nevermind ... I misspoke. My IACV is after the BOV and it doesn't seem to make much difference.

Turbo Zetec 'tour

11-03-2007, 10:38 PM

I dont have a problem with my HKS SSQV. honestly i would rather see it run too rich for a second or two than too lean. remember rich=safe, lean= boom. :D

gamiller

11-03-2007, 11:24 PM

Yes, it's a good rule-of-thumb to err on the side of running rich, but we have the ability to fine tune. I'm not nit-picking here. I've already had problems from running too rich, including:
* failure to pass emissions due to CELs
* failure of emissions components including oxygen sensors and the catalytic converter
* wasting fuel