BOV to atmosphere instead of powerpipe.....ok?

I did it for three years and no problems. Switched tuners once and each of them gave me an awkward eye until they tuned it and found no issues. It will always depend on your combo. Take it from me, someone who has done it, and not someone who theoretically will tell you thier opinion.

My advice: Try it WITH A REAL BOV and not a bypass. If you do not nose dive between gears you "should" be good. Always get an s/c car tuned, but if you have no issues you will be fine.

You will be dumping metered air. If this is something you want to do, you need to move the mass air sensor to be in between the blowoff valve and the throttle body(blowthrough setup)

Technically, you have a very slight vacuum leak with the bypass valve venting to atmosphere. To make it really work correcty as a blowoff valve you need to connect a check valve at the end, which creates the problem....finding a check valve that is large enough and strong enough to withstand the heat and pressure. This may be totally different with a supercharger and i may be completely wrong about the check valve, but i know that on my Merkur i tried it and spoke with a bunch of guys on the Merkur forum and they all told me i needed a check valve on the end because it was leaking air at idle...apparently the engine doesn't make enough vacuum to keep it shut unless you're driving. In the end it sucked either way and i hooked it back up properly as a bypass valve and it runs much better.

fiveohwblow said:

I did it for three years and no problems. Switched tuners once and each of them gave me an awkward eye until they tuned it and found no issues. It will always depend on your combo. Take it from me, someone who has done it, and not someone who theoretically will tell you thier opinion.

My advice: Try it WITH A REAL BOV and not a bypass. If you do not nose dive between gears you "should" be good. Always get an s/c car tuned, but if you have no issues you will be fine.

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Or take it from me someone that has tried it vented and it didn't work? If your bypass valve is actually a bypass it will be open at idle which WILL pull unmetered air. It will not work with it vented. Period.

Cobra912 said:

I was really curious to why it would be a problem if it was vented to atmosphere?? Isn't it just purging overboost so to speak while mainting a certain amount of pressure in the discharge tube?

Sorry guys but I'm a newb at supercharging as this is my first one...........

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Yes you are correct thats what it does so just route it back into the powerpipe. Or you can get a true blow off valve. I'd work with what you have personally.

bentley429 said:

Or take it from me someone that has tried it vented and it didn't work? If your bypass valve is actually a bypass it will be open at idle which WILL pull unmetered air. It will not work with it vented. Period.

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It did work for three years. Period. But whatevers clever. I would always suggest running with the bypass if you have that option as it is the better of the two.

fiveohwblow said:

It did work for three years. Period. But whatevers clever. I would always suggest running with the bypass if you have that option as it is the better of the two.

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If you made it work with a real blow off valve I would like to know how because you are the only person Ive ever heard of it working for. Always willing to learn just hard to believe something that shouldn't work you know?

I feel ya! I honestly cannot tell you the "why" it worked so well, just that it did. Both of my tuners were skeptical but both more than satisfied with the results. Realistically, they probably tuned it out but I know it just blows metered air which makes the mixture rich. As we all know, for power rich doesnt help but it also doesnt encourage detonation. If your mixture doesnt get too rich it runs like normal... I just know it worked well for three years until the Greddy type RS blowoff broke. The rubber grommet that allows the valve to open/close broke and I decided the bypass was better since I increased the boost to 12 lbs. I have a Vortech SC with an Anderson Ford Motorsport Powerpipe.

So it was a blowoff valve? Was it opening at idle?

bentley429 said:

If you made it work with a real blow off valve I would like to know how because you are the only person Ive ever heard of it working for. Always willing to learn just hard to believe something that shouldn't work you know?

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I guess you missed my post...it worked just fine for me . Here's a pic of the ghetto hardware store check valve.. (the white hand grenade looking thing above the alt.)



Then i got curious and even tried the biggest PCV valve i could get my hands on, but i was suspicious that it was too small in diameter and wasn't venting fast enough so i ditched it...




So yeah, putting a check valve at the end of the bypass valve will make it function just like a blowoff valve. It'll even make it go "whoooooosh" like everyone loves, but it won't make it any faster or run any better than plumbing it the way a bypass valve should be ran.

85_SS, is that a mass air car? I don't know much about 4cyl turbos and even less about merkurs. If it were speed density, it wouldn't matter. But with a mass air car, it is not good to dump metered air.