Printable Version of Topic

Click here to view this topic in its original format

914World.com _ 914World Garage _ Need opinions...BOV or Bypass valve??

Posted by: Mueller May 10 2005, 04:25 PM

blow off valve venting to atmosphere or a bypass valve???

with my car being as "rice" as it is, a loud BOV almost seems like a natural

Posted by: bd1308 May 10 2005, 04:28 PM

BOV.......Gotta have it....the bypass just doesn't do the turbo justice.

Posted by: Aaron Cox May 10 2005, 04:28 PM

get the chirping kind so you fit in with the ricers

Posted by: Andyrew May 10 2005, 04:29 PM

Explain to me a bypass valve...

You dont have to get one of the ricey superloud bov's...

Fine one that flutters... Bwbbwbwbwbbwbww... I like ours... Not a PPPPSSssshh

lol

Posted by: Mueller May 10 2005, 04:32 PM

QUOTE (Andyrew @ May 10 2005, 03:29 PM)
Explain to me a bypass valve...

You dont have to get one of the ricey superloud bov's...

Fine one that flutters... Bwbbwbwbwbbwbww... I like ours... Not a PPPPSSssshh

lol

from what I've read, the bypass dumps the air right back into the intake....how, I have no idea, seem strange, but that is what is installed on the factory Audi/VW's 1.8T and such.....guess it is quieter........

Posted by: Aaron Cox May 10 2005, 04:34 PM

just run a noisy one....

like you canhear it anyway

Posted by: bd1308 May 10 2005, 04:36 PM

bypass quieter much

Posted by: lapuwali May 10 2005, 04:51 PM

Blow off valve just vents the excess air between the turbo and the throttle plate out to the atmosphere. Less plumbing, more noise. A bypass valve is basically the same thing, but it directs the atmospheric vent back into the plumbing before the turbo. This is not only less noisy, but it can theoretically help keep the turbo spinning with the throttle closed.

If I were designing my own turbo plumbing, I'd study every photo and diagram of recent WRC turbo systems I could lay my hands on. The data is scarce, but it's clear they have excellent turbo setups, and they seem to all do something with the bypass system to reduce lag to an absolute minimum.

Posted by: bondo May 10 2005, 05:39 PM

If you're using any kind of airflow measuring device with your FI, you have to use a bypass valve. Otherwise you're losing metered air and you'll run rich every time it activates. If you aren't measuring intake air it's just a matter of preference. More plumbing vs. more noise. Our WRX had a blowoff valve on it when we got it (and it has a mass air flow sensor.. so it would run funny after it vented) It was kinda cute at first to be going around making PFFFT-SHWEEEE! sounds all the time, but it got old real quick. Fortunatley it came with the stock bypass valve too. I put the BOV on ebay and got $200.

Posted by: Mueller May 10 2005, 06:08 PM

well it looks like the bypass is the way to go with the FI so it does not get too disturbed....thanks...

Posted by: bondo May 10 2005, 06:13 PM

If you really want the sound you can get one of http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7973971363&category=33742.

Posted by: TimT May 10 2005, 06:24 PM

http://www.rudtnersracing.com/LRP.wmv

Get a BOV... we use them on all our turbos. and have no issues with mixture going off when it opens, then again we dont mass meter the air, we set up the EFI using manifold pressure and throttle position..

Alot of aftermarket BOVs also allow you to plumb them as as bypass valves so you can go either way with the installation.. simpler (ie KISS theorum) is usually the best route..

I guess it all depends on your priorities, all a bypass valve is, is a quiet blow off valve..

six of one half dozen.... etc.

Posted by: lapuwali May 10 2005, 08:20 PM

QUOTE (Mueller @ May 10 2005, 04:08 PM)
well it looks like the bypass is the way to go with the FI so it does not get too disturbed....thanks...

I'd agree that the bypass is the way to go, but keeping a speed-density ECU (like your Link) happy isn't the reason. With the MAP sensor on the far side of the throttle plate, whether the valve vents to the air or the intake is irrelevant. With a MAF system (think L-Jet, or most current OEM setups), it's an issue. I'd stay with the bypass because I think the blow-off valves sound dorky.

Posted by: Maltese Falcon May 10 2005, 08:39 PM

Mike, use a Bosch bypass valve (late 930 style) - cheap and will handle the air folw on your T-IV just fine. If you want better go Tial...uses the Bosch principal but made from billet. The "Free-spool up" is what you get with this...and you'll still get some good blow off noise. If your using CIS on your design, stay away from a BOV--it basically gives you a big vacuum leak on decel, and a bigger problem to drive around
Good to meet you at the Classic !

Posted by: Mueller May 10 2005, 08:42 PM

QUOTE (Maltese Falcon @ May 10 2005, 07:39 PM)
Mike, use a Bosch bypass valve (late 930 style) - cheap and will handle the air folw on your T-IV just fine. If you want better go Tial...uses the Bosch principal but made from billet. The "Free-spool up" is what you get with this...and you'll still get some good blow off noise. If your using CIS on your design, stay away from a BOV--it basically gives you a big vacuum leak on decel, and a bigger problem to drive around
Good to meet you at the Classic !

likewise meeting you....too bad you didn't toss me the keys to your car, but I forgive you for that,

I have an aftermarket programmable fuel injection, so no worries there about the CIS issues....

Posted by: MattR May 10 2005, 08:46 PM

Some guy on a ricer forum (wrx forum iirc) put a turkey caller in his BOV, so when he shifted his car sounded like a turkey. now THATS an idea

Posted by: Maltese Falcon May 10 2005, 08:59 PM

Turkey whistle ? LOL -- prolly a good sequel of Fast/ Furious ...maybe Fast & Featherless

Posted by: ! May 10 2005, 09:03 PM

Vroooom, chuf, chuf, chuf......

Posted by: iamchappy May 10 2005, 09:05 PM

I have never noticed any problems with a Tial BOV and my CIS setup.

Posted by: phantom914 May 10 2005, 10:05 PM

QUOTE (MattR @ May 10 2005, 06:46 PM)
Some guy on a ricer forum (wrx forum iirc) put a turkey caller in his BOV, so when he shifted his car sounded like a turkey. now THATS an idea

I think I want to turbo my car just so I can do that.

Andrew

Posted by: Brett W May 10 2005, 10:46 PM

The Bosch unit is junk. Pick up a DSM unit on Ebay. They are much better. Not cheap plastic and it will hold 15-20 PSI if you crush it. It also has a hose nipple to run it as a bypass unit or leave the hose off and just let it vent.