I met a guy with a 1st gen Eclipse and is in the process of rebuilding it. He owns his own shop. So, I went there with my friend and I asked him what BOV is he using. He is using 2 BOVs, 1 Greddy type-s and a Turbo XS( i don;t remember which one) Is there any type of purpose in using 2 BOVs?



Brian
West Melbourne, FL

1998 Mitsubishi Eclipse RS(White)
1965 Ford Falcon

Mods: AF/X UDP, NGK-BKR5E spark plugs, Custom CAI. Best et...16.31 @ 85.50 mph with custom ram air intake.

Originally posted by honcal98rs
I met a guy with a 1st gen Eclipse and is in the process of rebuilding it. He owns his own shop. So, I went there with my friend and I asked him what BOV is he using. He is using 2 BOVs, 1 Greddy type-s and a Turbo XS( i don;t remember which one) Is there any type of purpose in using 2 BOVs? Brian West Melbourne, FL 1998 Mitsubishi Eclipse RS(White) 1965 Ford Falcon Mods: AF/X UDP, NGK-BKR5E spark plugs, Custom CAI. Best et...16.31 @ 85.50 mph with custom ram air intake.

unless his turbo flows sooooo much air that one BOV couldnt possible vent it all, no. but my turbo is so big im running 3 BOV's :P

Both Thedawg and I know of somebody that is running a Greddy Type-S and a Tial unit at the same time. It makes a cool loud Pfffft...Whoooosh.

To answer your question Brian (and I'm doing this because my name is Brian too :))

The reason why someone would use two BOV's as opposed to just one (which is the way most are set up) lies in the function of a BOV.

I'm sure you know that the turbo pressurizes the intake tract forcing air into the motor (hence my name). When the throttle plate closes, when the driver lets go of the accelerator, the pressurized air has nowhere to go. It can't go into the engine because the throttle plate is closed and preventing air from passing (at least in large quantities). Soooooo, it goes the other way in the intake. This is a problem, as the air now works AGAINST the turbo, and causes the wheels to slow, sometimes stop and I've even heard that it can cause them to go the other way. This is called compressor surge. It's bad. Very bad.


To avoid this problem, people put BOV's on the intake pipe. These are basically valves that open when vacuum is present (like when someone gets off the gas, closes the throttle plate and manifold vacuum exists). When that happens, vacuum sucks the BOV's valve open and now, the pressurized air has a place to go, out the BOV! Not back into the turbo.

Now, to answer your question, the reason why people would have 2 of these is to vent more air. If for some reason, there's a HUGE amount of air to vent, at high pressure, there's a possibility that one BOV doesn't have enough time to vent all the air quick enough to prevent compressor surge. So you use two.


Wow, my hands hurt.

Brian

Damn man that had to of been the best explination I have EVER read here on 2gnt. You even explain in detail what maybe to others as the obvious but some don't know. Good job man!

Points for you!

Originally posted by ForceFed420a
To answer your question Brian (and I'm doing this because my name is Brian too :))

I'm going to comment because my name is Brian, too. :thumbsup

I had figured this was why one would want two BOVs, but I wonder what sort of CFM you would need to be flowing before you would consider something like this. Furthermore, would you just T into the vac line that runs to the first BOV? As in, run one vac line to the BOVs, and T it off just before them? I don't see how having a proprietary line for each would be anything more than a bit of redundancy just in case. :shrug

The reason for people having 2 is simple. They have to out-do the other rice that runs in Uncle Bens back yard. I personally saw a guy with a *ugggg* hyundai scoop that had 5, yes 5 bov's on his intake pipe. He sourced them from old 1st gen dsm's and 3000 gt's and then jb welded it to the damn thing. Quite gheto. If I ever see someone running 2 of them on a car that does not have more than 1000 hp I will turn them into ricecop.com and let the flaming begin.

Originally posted by DR1665
I don't see how having a proprietary line for each would be anything more than a bit of redundancy just in case.

I advise you always get a signal from the upper intake and never use a T. It's just a good rule of thumb. If you really need to use a T then be sure it's going to a MAP sensor or something of that nature cause it's never going to let any air in.

You sure one of them wasn't a relief valve a.k.a. a "pop off valve"? It's just like a BOV but instead of opening with vaccuum it has a spring that you set to a certain PSI and if you get a boost spike or your wastegate fails then the pop off vavle opens and reliefs the pressure so you don't go over the set tension. Like if you're boosting on stock internals and don't want to risk getting over 8psi. Just another safety measure.

Originally posted by a_miller_76
You sure one of them wasn't a relief valve a.k.a. a "pop off valve"? It's just like a BOV but instead of opening with vaccuum it has a spring that you set to a certain PSI and if you get a boost spike or your wastegate fails then the pop off vavle opens and reliefs the pressure so you don't go over the set tension. Like if you're boosting on stock internals and don't want to risk getting over 8psi. Just another safety measure.

thats what i was thinking

Damn thats what I've been needing. Where can I get a few? :P

I've seen a supra with 6 BOV's in line...

Evan B
97 GS- FOR SALE
90 GSX-sold
Stamford CT
EvMan2345@aol.com

The only car i ever saw with more than one was in a magazine about a month ago and this guy was pushing anywhere between 800-1000 whp with a big ass turbo...if you don't have this numbers and have 2 bov then just admit that you're just another ricer :nono