JTurtonRX_7

hmm im going to take my bov off of the stock system just to test it. If it blows my old crusty stockers oh well I guess its single time.

TheAsset

iTrader: (11)

haha that made me laugh.

JTurtonRX_7

Just took it of and did some initial testing, I was expecting some flutter but no it just sounds like a lower pitched bov. On a side note stock non seqs dont hit 10 psi til almost 5k in 2nd gear, never really noticed that before lol and ive been DDing it like this for years

Viking War Hammer

iTrader: (8)

My HKS BOV leaks... hmm

S2000ToRX7

Bov's are not needed ran without one for 20k on my s2000 when i was turbo'd people think it will surge the turbo but it wont. you have nothin to worry about. :-D keep everyone posted just so you can prove most wrong. :-D



Edit i was at 650 whp to at 26 psi. and beat the hell out of it at that.

arghx

iTrader: (3)

Ok it's been a year and almost 3000 miles of boosting. Turbo hasn't blown yet, no noticeable problems.

junito1

https://www.rx7club.com/members/thatpoorguy-131086/

I tried to see if he made a thread about it. BUt this forum member claims his stock twins shaft snapped due to his vacuum line comming of his BOV.
I searched a little but not much info on it.
HE has the carnage in his photo album

I personally used to own an 86 300zx turbo. besides the fact that z31 engines run 5-6 psi. The factory POV(pop off valves) do get plugged for performance and ran up to 13.5 psi like that.

Its up in the air. MY z ran without one for 2 years. And my 7 has used one for 5 years.

djseven

iTrader: (56)

Ive been running 13psi on the stock twins with it deleted for a little over 1k miles now. My turbos already smoked a little bit on startup for a few seconds and Ive seen slight traces of oil in the IC lines in the past before deleting it. Nothing has changed since deleting the bov, still same amount of smoke and no increase in oil in IC lines.

I was hoping it would be devastating to the turbos or somehow blow the engine so I could get motivated to install a fresh rebuild in my car but no dice. I will be running my 500R without a BOV whenever I find time to install it.

Double_J

iTrader: (28)

Lots of reading in here.

I have a couple of questions. Dj did you notice any performance improvements on the twins? If you actually boost higher between shifts do you need to retune the car to accommodate the extra cpl psi? Could that explain why the one car above was jerking, even though it ran quicker times?

Finally if you delete the bov that is almost the same concept as running the re circulating bov right?

arghx

iTrader: (3)

First of all, remember that 3rd gen car and a 2nd gen with a standalone EMS don't have an airflow measuring device in the intake, so there are no potential driveability issues related to that.

Now on a recirculating BOV (an air bypass valve) the pressure waves are relieved through the valve to the low pressure (inlet) side of the turbo, before the blades. Without an air bypass valve the air goes back through the turbo itself and out the inlet.

The debate is whether, upon lifting the throttle, relieving the pressure through the turbo itself (no air bypass valve at all) will damage the turbo or hurt response. One argument is that it will quickly cause damage to the turbo. That has been mostly refuted. I haven't had a BOV operating for a couple years now, but with my projects and the way I drive my car that's about 5000 hard miles boosting anywhere from 16 to 21psi.

Some say running no air bypass valve will shorten turbo life over time. There are a couple turbo cars that have been mentioned which came without one from the factory. As for longevity debates in these Rx-7 applications, well there are people like me testing this just for the heck of it really.


The whole debate about turbo spool and response which surrounds air bypass/blowoff valves is tricky. There is a lot of marketing hype around aftermarket BOV's because people are trying to sell products. There is also more anecdotal evidence indicating the opposite--that BOV's don't really make much of a differerence, or that they actually hurt response. And that's the kind of thing that is frustrating to sort through. What compounds the confusion is hearing claims from people with airflow meters (Evo, STi), because keeping that sensor happy can also improve the way the car drives. I think one of the only way to settle this will be to get datalogs from a turbo tachometer but Google tells me they are like $1600.

StavFC

$425

http://www.atpturbo.com/mm5/merchant...egory_Code=BCS

How hard fitting is, esp to non Garrett turbos, I have no idea.

CBR

Cant believe this thread went 5 pages(i only read 2),why dont people listen to people that have been there done it! rx72c has proven that you dont need one,I have ran many turbo track cars with out bov's without any issues and they responed better between gears without ya gay bov.all with plain bearing turbos aswell.
rx72c I feel ya pain buddy,trying to explain to people how **** happens and they just dont listen because they THINK it cant work

djseven

iTrader: (56)

I notice less pressure drop between shifts but it is minimal. I am using a mazdaspeed short shifter and shifting using the clutch like a normal person drives on the street. You arent going to see vast response difference, it was just another thing to delete from the engine bay. Getting used to the sound is a little difficult, I prefer my car to be quiet and it is far from it with the BOV deleted. Ive since put another 1k miles or so on the car since the last post with no ill effects.

Frostycrowd

iTrader: (9)

I am now at like 3k miles without a BOV.

My reasoning is that if I have an antisurge housing that can prevent true harsh on throttle surge I doubt a flutter with no throttle is goin to hurt it.

arghx

iTrader: (3)

Damn. That's not a bad price considering the other options. I bet it's some kind of square wave signal that can't be easily/cheaply datalogged though.

[IMG][/IMG]

And that's why the Mazda describes the factory air bypass valve as a noise reduction device...

beefhole

iTrader: (29)

^I'm not running one right now. I re-did my IC setup and just didn't get a flange on my new piping for one. I don't drive too much, and when I do, I don't boost too hard (needs tune, waste gate). However, it really does sound ODD. The fluttering on my car is very loud. Personally, I prefer NO noise. I want to put one back on and route it to the filter/turbo inlet.

Supercharged FC

iTrader: (7)

So I haven't read every post because I am lazy, but anyone who works in the industry fears the terms "unexpected/unintended motion" in a DFMEA review. Toyota had some fun with that one. Not running a BOV can cause this.

The all of the stock cars (that I know off) that do not run a BOV/POV have a fuel or ignition cut programmed in, which is not ideal in IMO. On a race car it's no issue, but anyone who has had a car surge on them knows it can be difficult to handle. My car use to surge at the top of 1st & 2nd gear causing me to bounce off the rev limiter. (I had sticky secondary throttle plates, stiff BOV, and I run a map sensor) If you get blocked from passing you can end up swapping paint. Either way you don't get out of the corner right.

I understand that with all new equipment and a good tune you may not need one but who wants to worry? A BOV is cheap. I run a CXracing BOV, supercheap and works great.

The best theory I've heard is that you can only have two of the following fast/cheap/safe in a race car. Most of us go cheap and fast.

That's my two cents...

SmogSUX

iTrader: (12)

Cheap BOV endup costing you more. I had a Jeg's one that came on a TII I picked up. It stuck open/closed too slow and caused some issues. With my current setup running the Greddy Type S it isn't an issue. If I were to build my setup again I wouldn't use a BOV. But it would cost me more to redo the piping to get rid of my bov flange, so BOV is staying for now.

thewird

iTrader: (8)

What does compressor surge due to mismatched turbo have to do with not running a BOV? Unless I mistook what your trying to get at?

Not running a BOV, isn't about cheaping out. It's that fact that it may in fact not be needed, one less thing to fail, cleaner engine bay, and that it possibly increases turbo response after a shift since the IC/pipes don't depressurize. A lot of members that have tried it have claimed it does have a noticeable affect on boost response after a shift.

I run an undersized BOV on my car and it flutters every time i shift which gives the car a unique sound. I've been considering removing it but haven't decided yet hehe. It's one of those things I'll probably get to when everything else on the car is the way I want it running.

thewird

arghx

iTrader: (3)

I don't think anyone in here is advocating that you run a turbo that is mismatched to your engine. This can cause damaging compressor surge under heavy load driving and there is no debate about that. That type of compressor surge is separate from the question of what should happen to the charge air after you close the throttle.

Btw, I was dynotuning a streetported GT40 FD on Friday and the Turbosmart BOV was causing a massive boost leak. We were wondering why we couldn't break 300 to the wheels at 14psi on a Garrett GT4094R turbo. It took us a while to figure it out because the atmospheric wastegate dump was so loud that you couldn't hear anything else. Of course a good BOV that has been installed and adjusted properly will not cause a boost leak.

Supercharged FC

iTrader: (7)

Let me clarify,

Depending on your system and the condition of your parts you can have a "surge" with a matched turbo. For me it occurred at high RPM shifts (7500 + rpm) near redline in low gears in combination with a sticky throttle and a stiff BOV. It took all three of these conditions to cause the issue. It theory it can happen any time you have a turbo.

I sorry but "clean engine bay and one less thing to fail" sound like excuses. Not knocking your opinion, I just don't agree.

I understand running no BOV can decrease spool time after shift but if you have the right turbo you should not have delays between 2-3, 3-4, and 4-5. In 1-2 shifts it can be beneficial IMO to have a slight drop in boost/power so you don't light the tires up. It's kind of like the auto-traction method (shift above peak torque).

Maybe people have issues with BOV because they shift slow, and don’t put enough right foot into it.

Frostycrowd

iTrader: (9)

^
I am missing your point, your turbo surging has nothing to do with the BOV so why are you claiming it caused the problem?

rx72c

iTrader: (8)

CBR. dont waste your time. i am learning slowly. People do not want the word from people with real world experience who are willing to share info you have to pay good money for. They would rather go on their own theories.

djseven

iTrader: (56)

You have an issue somewhere. With HKS downpipe(restrictive), resonated midpipe, and Greddy SP I hit 10 lbs around 38-3900rpms in second.

Supercharged FC

iTrader: (7)

Any body data log pressures before and after throttle plates yet? If the pressure spike is the same with and without BOV I would buy into this, but I would have to see more than "I haven't had issues yet". That's not a good way to find out IMO.