Sean94Z

I know this has come up before, I have done the search and looked through most of the threads concerning this. I understand the differences between the two. The bypass valve stays open in vacuum and bypasses some of the air you are making while the blower is spinning at idle and cruising. The BOV only opens AFTER you have made boost and releases the air, then closes again while cruising. I don't use the MAF anymore, so it doesn't matter to me at all if the air doesn't recirculate.

Has anyone replaced the spring in a BOV so it will open under vacuum ??? If so, it would function the same as a bypass valve. I can do this a lot cheaper than buying ATI's Race Valve which is $415.

ATI told me that with my boost level, the pro-flow surge valve is probably leaking and not bleeding the extra pressure off fast enough when I back off the throttle. So, I need to do something different.

Pictures? Facts?

Cheers,

Sean

Sean94Z

In my continuing search for knowledge, I wrote Tial's tech support ...

My E-Mail.

I am thinking about using one of your BOV's in my supercharger application. My question is, will the BOV stay open at idle (i.e. under vacuum) to act as a 'bypass' valve to release some of the air the supercharger is producing at idle and while cruising, and then under boost, close completely and then open completely when I close the throttle?
Would I need to shim or change the spring for this?

Their response:

We make a -3psi spring exactly for what you described

I know No Limit Motorsports has the -3psi springs, so if you order it from them, they should be able to swap out the spring for you
Jake
TiAL Sport


So, I suppose the second part of the question stands: anyone do this yet?

ZBLKHELLRZR

I know NA$TY off of LS1tech had a BOV on his prochagred car before switching to a Turbo had done this. It didn't work out too well actually either from the car always sounded like the BOV was sputtering. I seen videos of it and it didnt' sound right and the minute he switched over to a BPV the car ran like a top.

Now will this apply to you? Can't say but just off the one person who has done it you may just be better getting a bigger BPV. Get a Mondo through summit as they can be had for under 300 and will move the air. http://store.summitracing.com/partde...5&autoview=sku

I got lucky and got my ATI Race bpv for under 300.00 new.

Sparkz28ss

I run a TurboXS RFL BOV... its open at low engine speeds on the highway in 5th and 6th gear.

... it starts to open at 12hg and is fully open around 15hg...so when im just loafing down the highway its open a little...cant really hear it unless you know what it sounds like

StripedFomula

how does it sound and how much boost are you running?

blown69nova

I run a Vortech Mondo bov, and it absolutely does bypass air under vac., you should hear my car on the freeway!
Bypass valve/ blowoff valve do the same thing, the difference is that people route the bypassed air back to the air filter side because of the maf sensor and it's quieter. If you have a car that uses speed density you can simply blow the air off when not needed, ie. under vac. or throttle closed.
Thanks, Steve

Sparkz28ss

I think it sounds good..i had a vid of it some place

most of the time the car is making around 12psi

mzgp5x

Upgraded to a D1 Procharger, and replaced my bypass valve with a hks_BOV. My MAF was located on the intake side, and, the BOV on the engine intake after the intercooler. It ran very rich in part throttle closed loop. I went to twin evolution motor sports bybass valves with the retun to the blowr intake downstream of the MAF. Runs much better.

Loosing air after it has been measured by the MAF will lower afr.

Hope this helps. (LT1 383 - D1) B.

Sparkz28ss

yup, thats why you move the MAF back to the stock location...then it will run like a champ

Sean94Z

Thanks!

Ponyhntr

This is incorrect. Bypass valves and Blowoff valves are indeed different. Bypass valves are open under any vacuum condition (idle, cruise, decel), and Blowoff valves are closed all the time until the throttle is shut under boost and there is a small spike in pressure.

Routing it back into the inlet tract is just referred to as recirculating the bypass/BOV.

Sean94Z

Everything I have been told is that this is completely dependent on the spring installed inside the BOV. If the spring is strong enough to hold the valve closed while in vacuum, it does, otherwise, it opens just like a bypass valve, then closes when under boost as the two sides are pressurized, and then opens again when you back off the throttle and vacuum returns.

I am ordering the Tial 50mm BOV and the -3 PSI spring. I will let you know how I make out.

Jeff 96 SS

Ya let me know how that works out for you. I hope it works but have my doubts. I have seen BOVs that won't stay closed at certain boost levels because the spring is not strong enough to keep it closed and they will flutter at high boost. What you have to remember is that the vacuum line is only pulling or pushing on a small part of the plunger and the boost is pushing on a 50mm valve more area to push on so who is going to win?

Ponyhntr

Ponyhntr

I was not aware that there were - psi springs for BOV's.