Interesting read for those of you questioning the "BOV or no BOV" movement

[Tony-R32]

^ i love that vid, bov on a bike!

[mike300zxt]

Mightycarmods did a vid on HP and BOV.

No measurable difference between none, recirc and atmospheric.

/thread

Lol, sorry, but that vid was useless!

Of course there is no difference on a single gear dyno pull...the BOV doesn't do anything during the pull!!! It doesn't do anything until you let off the throttle to shift gears. Now if they did a 1/4 mile dyno simulation, that would tell us something useful. As the article mentioned, a BOV or no BOV caused poorer performance on the track because of power lost between shifts (not during a signle gear dyno run).

Without getting technical...

BOVs sound cool, reak havok on emmisions, and generally cause power loss between shifts. Adjusting the tune can minimize these issues, but cannot eliminate them on a MAF-based tuning system. Cars running a MAP based system don't suffer as badly from emissions issues, but will still experience slight power loss as you are giving up pressurized air. This comes from experience with dyno tuning & air-caring GT-Rs, GTS-Ts, plus turbo VGs, VQs, SRs & KAs. BOVs can make cars with other issues more susceptible to stalling between shifts, but cars with working AACV's and no major boost/vacuum leaks generally won't stall. Cars with BOV tend to fowl spark plugs quicker, causing further power loss over time. Many BOVs can also be hooked up as recirc valves.

Recirc valves (used on stock on GT-Rs, GTS-Ts, 300ZX's, R35's, etc) reduce boost spikes between shifts, and do so without causing issues with emissions or power loss. Recirc valves are the best bet, especially for people still running a MAF-based tune.

No BOV/Recirc causes the tune/emissions issues mentioned in the article, and also cause the airflow to reverse, which will cause lag when back on the throttle. Lag = power loss between shifts.

If you want the BOV sound while keeping all the benefits of the stock recirc setup, you can use most aftermarket BOVs as recirc valves as well.

I don't care what your butt dyno says, and a single gear dyno run doesn't tell us anything. Do 1/4 mile simulations on the dyno, and you will see a measurable difference between BOV, recirc and no BOV (with recirc loosing the least power between shifts). Edit: unless you're doing full throttle shifts, in which case no BOV is fine.

Again i have to say i dont entirely trust these accusations.. I've run my turbo at 15 psi for 2 years now with some spikes ramping up past 16psi without an issue.. This thing STILL has no shaft play, oil leaking or blown wheels..

Running stock turbos at high boost on a stock fuel system and stock tune causes excessive heat. Excessive heat makes the wheels fragile and prone to shattering, and also increases bearing wear. It also tends to lead to poor engine compression. A surge on the intake side doesn't really have much impact on the exhaust wheel unless there is so much shaft play that intake surge causes the shaft to move far enough that the exhaust wheel hits the exhaust housing. Of course if there was that much shaft play, it was time for a new turbo anyways

At Ztune, we demonstrated that stock turbos could run 28PSI with a proper tune and water methanol injection to keep things cool. In fact, pushing things to the limits, we found that ring lands on the stock pistons break before the stock turbos would when maintaining a proper A/F. And even getting the ring lands to break required excessive ignition timing.


So basically, a proper recirc setup leads to the best all-around performance (i.e. least power loss between shifts). If you want the BOV sound, use aftermarket BOVs, but set them up as recirc valves. If you run no BOV or recirc, then you're loosing power unless you're doing full-throttle shifts. Probably a good replacement for you aging stock recirc valves as the internal springs get weak over time. Most BOVs come with a fitting (or have one available) to set them up as recircs. When you turn up the boost, get a proper tune, and you can make some reliable power!

[Zacho]

BOVs sound cool, reak havok on emmisions, and generally cause power loss between shifts. Adjusting the tune can minimize these issues, but cannot eliminate them on a MAF-based tuning system. Cars running a MAP based system don't suffer as badly from emissions issues, but will still experience slight power loss as you are throwing off AFRs, and giving up pressurized air. This comes from experience with dyno tuning & air-caring GT-Rs, GTS-Ts, plus turbo VGs, VQs, SRs & KAs. BOVs can make cars with other issues more susceptible to stalling between shifts, but cars with working AACV's and no major boost/vacuum leaks generally won't stall. Cars with BOV tend to fowl spark plugs quicker, causing further power loss over time. Many BOVs can also be hooked up as recirc valves.

Uhhh...

How do you throw off afr's when a map based will fuel correcting to the air loss providing you are tuned properly...the bov would be pre-tb and the map sensor is after.

[mike300zxt]

Uhhh...

How do you throw off afr's when a map based will fuel correcting to the air loss providing you are tuned properly...the bov would be pre-tb and the map sensor is after.

Looks like I got caught up in my rant! Good catch, you're right. On a MAP system a BOV doesn't throw off AFRs, but it does still cause some lag/loss of power between shifts when hooked up as a BOV instead of a recirc.

[nelsonmxmarc]

Well, in theory, any BOV that does NOT recirculate is a loss. As long as air is contained in the system (No bov / recirc) you're far better off performance wise. Then it all comes down to thousandths of a second in terms of gained time shifting, power increases off shifts, and so forth..

[M13]

Lol, sorry, but that vid was useless!

Of course there is no difference on a single gear dyno pull...the BOV doesn't do anything during the pull!!! It doesn't do anything until you let off the throttle to shift gears. Now if they did a 1/4 mile dyno simulation, that would tell us something useful. As the article mentioned, a BOV or no BOV caused poorer performance on the track because of power lost between shifts (not during a signle gear dyno run).

Without getting technical...

BOVs sound cool, reak havok on emmisions, and generally cause power loss between shifts. Adjusting the tune can minimize these issues, but cannot eliminate them on a MAF-based tuning system. Cars running a MAP based system don't suffer as badly from emissions issues, but will still experience slight power loss as you are giving up pressurized air. This comes from experience with dyno tuning & air-caring GT-Rs, GTS-Ts, plus turbo VGs, VQs, SRs & KAs. BOVs can make cars with other issues more susceptible to stalling between shifts, but cars with working AACV's and no major boost/vacuum leaks generally won't stall. Cars with BOV tend to fowl spark plugs quicker, causing further power loss over time. Many BOVs can also be hooked up as recirc valves.

Recirc valves (used on stock on GT-Rs, GTS-Ts, 300ZX's, R35's, etc) reduce boost spikes between shifts, and do so without causing issues with emissions or power loss. Recirc valves are the best bet, especially for people still running a MAF-based tune.

No BOV/Recirc causes the tune/emissions issues mentioned in the article, and also cause the airflow to reverse, which will cause lag when back on the throttle. Lag = power loss between shifts.

If you want the BOV sound while keeping all the benefits of the stock recirc setup, you can use most aftermarket BOVs as recirc valves as well.

I don't care what your butt dyno says, and a single gear dyno run doesn't tell us anything. Do 1/4 mile simulations on the dyno, and you will see a measurable difference between BOV, recirc and no BOV (with recirc loosing the least power between shifts). Edit: unless you're doing full throttle shifts, in which case no BOV is fine.




Running stock turbos at high boost on a stock fuel system and stock tune causes excessive heat. Excessive heat makes the wheels fragile and prone to shattering, and also increases bearing wear. It also tends to lead to poor engine compression. A surge on the intake side doesn't really have much impact on the exhaust wheel unless there is so much shaft play that intake surge causes the shaft to move far enough that the exhaust wheel hits the exhaust housing. Of course if there was that much shaft play, it was time for a new turbo anyways

At Ztune, we demonstrated that stock turbos could run 28PSI with a proper tune and water methanol injection to keep things cool. In fact, pushing things to the limits, we found that ring lands on the stock pistons break before the stock turbos would when maintaining a proper A/F. And even getting the ring lands to break required excessive ignition timing.


So basically, a proper recirc setup leads to the best all-around performance (i.e. least power loss between shifts). If you want the BOV sound, use aftermarket BOVs, but set them up as recirc valves. If you run no BOV or recirc, then you're loosing power unless you're doing full-throttle shifts. Probably a good replacement for you aging stock recirc valves as the internal springs get weak over time. Most BOVs come with a fitting (or have one available) to set them up as recircs. When you turn up the boost, get a proper tune, and you can make some reliable power!

thx Mike!

I did find the vid entertaining however.

[RHDskyline]

This thread should be stickied, cause there is a lot of good info in it

[RHDskyline]

Im in the market for a Blow off valve for my sr20det actually. It had a vent to atmosphere one on it. But it is broken now so i need a new one. Ive been doing a lot of research and it looks like the Recirculation BOV will be the better choice for any car using MAF's. Now i read that if you have a tuneable ECU, or you get it tuned with a VTA BOV, you can eliminate the stall problems when coming to a quick stop or the split second of the engine running rich.


I think im going to go for a Recirculating one as i am going for a sleeper look with my 240. Stock body, i painted the front mount black so its hopefully not that visible. and not having the sound from a BOV will help