Anybody replace their Bypass Valve with a BOV ?

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

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?

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/partdetail.asp?autofilter=1&part=VOR%2D8D103%2D001&N=700+115&autoview=sku

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

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

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

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

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

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

most of the time the car is making around 12psi

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.

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

I don't use the MAF anymore, so it doesn't matter to me at all if the air doesn't recirculate.


Thanks!

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.

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.

Blowoff valves are closed all the time until the throttle is shut under boost and there is a small spike in pressure.

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.

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?

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?

:yes:

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.

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

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


See 2nd post above.. That's what TIAL told me.

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?

Very good points Jeff. I copied your post to TIAL ..

Their response

Yes it will stay closed. you also have the pressure of the spring working for you which gives the top load a little advantage. There is a small line going to the top, but the area it has to fill is also very small.

The BOV’s have held 80+psi in competition, 20 will be no problem


Could we look at this sort of like hydraulics?

Very good points Jeff. I copied your post to TIAL ..

Their response

Yes it will stay closed. you also have the pressure of the spring working for you which gives the top load a little advantage. There is a small line going to the top, but the area it has to fill is also very small.

The BOV’s have held 80+psi in competition, 20 will be no problem


Could we look at this sort of like hydraulics?

Well with a strong spring I could see it hold with 80 PSI as they say, but a weak spring that would be required to let it open in all vacuum conditions no way! There will be a PSI limit well below 80PSI for that weak spring. Like I said I hope it works at your boost levels. When you get that thing installed go for a few full boost runs with someone watching your boost gauge closley and watch for the old bouncing needle.

I just took my car out for a ride, and my Vortech bov bypasses air anytime there is a vac. condition-idle, cruise etc.
The mondo unit can be adjusted just like a fuel press. reg.
Steve

I just took my car out for a ride, and my Vortech bov bypasses air anytime there is a vac. condition-idle, cruise etc.
The mondo unit can be adjusted just like a fuel press. reg.
Steve

Steve,

Is this what you have?

http://www.vortechsuperchargers.com/product.php?p=24

If so, that is a bypass valve, not a Blow Off Valve..

Similar but different.

Thanks,

Sean

That is exactly what I have.
So, does a bov need a vac line connected? Do they just "pop off" their seat, do to the excess pressure spike caused by the throttle blade being slammed shut, overcoming the spring?
Thanks, Steve

Steve,

A BOV does indeed use a vacuum line. They put a spring in there to assist in keeping the valve closed. The vacuum line reads boost, then vacuum suddently and the valve pops open to release the pressure on the one side.

I think the main difference is the spring, I am not positive, but I don't believe Bypass Valves use springs. I think they use a different type of acctuator to open and close.

Sean

Well with a strong spring I could see it hold with 80 PSI as they say, but a weak spring that would be required to let it open in all vacuum conditions no way! There will be a PSI limit well below 80PSI for that weak spring.
Why? If its 80psi under the valve you will have 80psi + the spring pressure on the other side to keep it closed.
Have run a tial copy this season widh a spring i had in the garage and i havent had any problem yet, Cant fo sure say if i have a "bouncing needle" beacause the boostgauge only goes to 20psi and the needle sits thight at the bottom of it.

Why? If its 80psi under the valve you will have 80psi + the spring pressure on the other side to keep it closed.
Have run a tial copy this season widh a spring i had in the garage and i havent had any problem yet, Cant fo sure say if i have a "bouncing needle" beacause the boostgauge only goes to 20psi and the needle sits thight at the bottom of it.

You need another boost gauge :D The reason I say that is the spring that will allow the valve to open under vacuum at idle will have to be very weak. the design of most of these type valves only push/pull on a small area of the top of the valve and the boost will be pushing on the entire face of the valve, it is pounds per sqaure inch so you have more sqaure inches being pushed on. I'm not sure I can explain this well without drawing a picture but all BOVs have a boost limit the spring pressure is the way they increase this. some use shims some are adjustable and some you actually change the spring. Does this make any sense?

This is the BOV Im using...works great for me...as I said, its open past 12hg..under that its closed and does not leak.


http://discountpowerparts.com/catalog/images/TurboXS%20BOV-H-RFL.jpg





Adjusting the Racing Bypass Valve

The Racing Bypass Valve spring tension will need to be adjusted if the valve vents pressure prematurely or causes rough idling. Adjustment is done as follows:

CAUTION: Use care when removing valve cap. Cap is under tension due to spring load.

1. With the engine turned off, CAREFULLY screw the cap off the main body of the Racing Bypass Valve in the counter clockwise direction.

2. Remove the spring from the Racing Bypass Valve. D o not remove any other internal components.

3. Take one (1) of the ad j usting packer washers and place it into the main body. Ensure that it is sitting flat inside the piston.

4. Replace the spring and the cap and retest the vehicle.

5. If the vehicle does not run smoothly or if a reduction in maximum boost pressure occurs, add additional packer washers as per steps 1 through 4 above.

is the above pic a TurboXS RFL. i will be buying one for my lt1 if it will open under vacc.

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

most of the time the car is making around 12psi



from a block away it sounds like a Chinook on crack...:D. jk sounds great..


pip

is the above pic a TurboXS RFL. i will be buying one for my lt1 if it will open under vacc.

yes, its the RFL-H


from a block away it sounds like a Chinook on crack...:D. jk sounds great..


pip

lol ......:o

Are u guys running BPV's because of your MAS , or would a regular BOV work on my 93z with a MAP sensor.

From what i understand the turbo does not give enough air to the engine during idle. therefor the BPV opens allowing more air into the engine bypassing the turbos.

Im prob way off but someone please point me in the right direction.

Thanks

So, I finally got this put on my car. The Tial BOV stays open at idle, but does not close until 4 PSI, then it stayed closed all the way to 15#'s where I blew off my hose going from the blower to the throttle body.. Tried a couple more runs and had the same issue..

So, I am calling Tial to get a different spring to close it at 0 PSI, not 4 :)

But the good news is, it held the boost up top.. well, most of it so far.

glad to hear! let us know whats happening once you change the spring

thanks for being the guinea pig, please let us know what the secret combination is.

Ok, so I tried the next spring up and it stayed closed pretty much until I was in boost and backed off, causing a high boost spike, then it opened. So, I went to the hardware store and bought a similar spring to the one I had and started cutting coils off of it. Now, I have it set to it stays open at idle, and closes between 5 and 7 inches of mercury on my vacuum gauge. It stayed closed all the way to around 5000 RPMs where I was seeing 16#'s of boost on my gauge. My car is not tuned at all for the new setup, so I am not going to rev it to 6500+ just to see if the valve stays closed. I can tell you it seems to work perfect with this spring and I notice I get into boost faster now. I am pretty sure the POS bypass valve from ATI was leaking before. Now I can hear the valve closing and the car sounds completely different.

So, now for some tuning and we'll see what happens on the dyno when I rev it up and get some high boost runs in.

Sweet! Keep us posted

any updates?

Sean,

Hows it going man?

How has this setup been working for ya?

Hope all is going well!
Claude

Hey Claude,

Long time no talk.

After I did the BOV, I took the car off the road for the winter. I ended up replacing the seals in the D1 while I had it down, and a few other tweaks, like methanol :)

I took the car out for the first time last night, just did some tuning runs. Still seeing 15+#'s of boost at 5000 RPMs, I maxed out my map sensor, I only have a 2 bar MAP sensor hooked up to the DFI. My brother-in-law has a 3 bar so I am going to borrow his and see what it looks like. The car is so rich right now, I haven't turned on the meth yet, and I am seeing 9.5:1 - 10.5:1 across the board, that's with 22 degrees of timing and no intercooler.

Seems like the BOV is working fine, so, I will try to get some more tuning in, then tune for the METH and go from there..

Took the car out again last night. This time with a 3-bar MAP sensor. I also swapped out the plugs because I was having a miss problem. Went with NGK R5671A-9 this time, I had the R5671A-8's before. All I can say is WHAT A DIFFERENCE! The car pulled strong through the entire RPM range, was 11.7:1 AFR all the way through the RPM range, so I still have some room to move. The 8's I had in there must have been a little too hot, because these new plugs have cleaned up the car so nicely. It runs so much smoother and cleaner the entire time.

Now for the fun news..

The MAP Sensor showed 15#'s of boost at 4500, 18#'s of boost at 5200 RPMs, and then I shut it down to check the AFR levels and make some adjustments. DId another pull, saw the same thing, and blew the intake hose off the throttle body. I had 0 tools with me, so I drove it home. I am sure I am going to see 20+#'s out of this D1.

This BOV has been working great for me. I am going to get some DYNO time this week hopefully so we can double check the tuning and make sure the BOV is staying shut. It must be though, when it opens, it dumps so much air, I doubt I would see boost levels like I am seeing.