HAILERS

Does anyone run without a BOV? What harm will I experience in the short run running without one?

BlaCkPlaGUE

oh christ.. please mods lock this thread right now! its gonna turn into a huge disagreement like last time!

Read this thread, the 6 or so pages of it and im sure that you'll find an answer

https://www.rx7club.com/showthread.p...ight=point+bov

HAILERS

I sorta, almost, kinda read that one. I think I'll go with what WhiteFC says if he replies to this one. I think he has run without one before. I could be wrong. Let's say when I boost...I let off the throttle with some ease instead of letting all off at once? I will get one, bov, but not for several days.

RamCon

why not just use the stock T2 BOV if your worried? should be easy to find one in the wrecker's...

HAILERS

I have to weld. glue, afix a nipple on the new fmic piping to do that. The Tuboii bov I chunked on the shelf for now. I'm thinking of soldering a nipple on the new pipe and reinstalling the old turboii bov. Just thinking of it. Ain't doing it ...yet.

If I solder a nipple on....do I have to drill a hole in the new duct? (late Saturday humor_)

WAYNE88N/A

I'm still getting over the initial shock of you starting a thread with a question...

.........

OK, I'm all better now...

With all the gauges and gadgets you have, and realizing you're the one in control of the throttle, I say go for it...

Then again, I don't run with those fuel-sucking maintenance nightmare engine destroying animals known as turbochargers, even though you keep telling me to get one

Maybe I'm just a little jealous because I don't have one......................Naaahhh

HAILERS

I consider the turboII cars trouble free compared to the non-turbo, gas sucking, aux port sticking, slow mobile n/a's. With the turbo car I can acutally merge in traffic and actualy accelerate in fifth gear. P.S. I have both types. Sometimes I actually drive the n/a and it's really a fun car.

Oh! Did I mention that Turbo cars don't hesitate???? humor

WAYNE88N/A

They don't, lol? You haven't been reading all of the threads started the last couple of days, then. Digi, for one, has got one going right now (hesitates/ surges at WOT, I think)...

One of these days I might actually get a turbo for a "fun" car, but it doesn't make much sense for my 100 mile a day daily driver

I don't have any problems merging into traffic- something must be wrong with yours. Need any help with it?

HAILERS

***I don't have any problems merging into traffic- something must be wrong with yours. Need any help with it? ***

YES! Tell me where a shop is within five minutes of my house, who can weld on a Greedy BOV for five bucks or less, including the BOV. And it wouldn't hurt if they came over and picked up the car and returned it in thirty minutes.

WAYNE88N/A

More humor?

You don't know anybody around you with a little TIG unit? What about RP in Dallas? You know, the little city directly to the east of you...

RotaryResurrection

iTrader: (8)

A BOV is really only necessary for a smaller type turbo like a stock rx7 turbo and other turbos on small displacement engines like imports. Some of the domestic turbo cars, take a grand national for example, came with a larger turbo. Same for deisels. No BOV on those vehicles. The reason is because compressor surge can harm a smaller turbo...it has less rotating intertia because it has less mass. IT is easier for surge to slow down or even reverse direction of these smaller turbos. THe bigger ones don't have to worry with it because theyre much stronger. Severe surge on a small turbo can actually break the shaft in half.

With that said, the main thing you'll have a problem with when running no BOV and stock fuel injection, is surge actually interferes with your AFM. IT can pass through the turbo compressor side and cause the flapper door or cone to slam shut which plays hell with your injection...it basically would cut fuel and cause the car to sputter momentarily. I have seen this happen on some cars before...and not on others.

IF you're easy with it Im sure there won't be any problems.

Terrh

iTrader: (7)

the reason diesels have no BOV is because they have no throttle plates!
Lots of cars don't have a BOV and last a long time.. my metro turbo has no BOV, some older porsche 911's don't either.

I wouldn't call stock TII turbos "small".. they're much bigger than turbos on DSM's/WRX/etc.

RotaryResurrection

iTrader: (8)

smartass

Let me rephrase that. Some vehicles have large turbos, such as those turbos that come on large displacement domestic engines or diesels. Those larger turbos can withstand surge without any problem.

White_FC

Dare I say it again... ok.. you've made me do it..

You wont have any problems not running a BOV HAILERS, and yes when I was running my turbocharged N/A engine before I killed it, I didn't have a BOV, the turbo is still in factory showroom condition

and I really... REALLY don't want to start another shitfight here.. but...

"The reason is because compressor surge can harm a smaller turbo...it has less rotating intertia because it has less mass. "

Care to explain why requiring less force to turn it backward, which doesn't happen for some seconds mind you, would harm the turbo more?

Anywho, I've pretty much said my piece in that 'other' thread.

RotaryResurrection

iTrader: (8)

I've been told my respected turbo builders that they've seen smaller import turbos broken as a result of surge. I tend to take their experience over anyone's word or speculation. I have not personally had any turbos tear up running with no BOV, but I have had cars where the surge interfered with the afm.

White_FC

Ah I see, fair enough then, it's just i've heard that a turbo repair place said not running a BOV wouldn't help the turbo last any longer.
This was a T25 on a 2ltr motor. (ie, small)

Strange.. so many differing oppinions.

Well, I never had a problem.. (running either the stock AFM or later on my microtech)

HAILERS

I've been playing it safe and have only boosted to around five psi max. I can hear a tingle. tinkle sound when I let off. I thought it was a rattle in the dash at first. Acutually it sounds like detonation/ping more than anything else. But it's only when I let off the pedal, so I ASSuME it's not detonation.

It's a newly rebuilt, no shaft play at all turbo and I did not hear this tinkle prior to the new fmic.

I'll probably buy a BOV from that outfit in the suburbs of Ft Worth (Dallas/Garland) called RotaryPerformance.

Or maybe I'll weld on two nipples and use the factory BOV. One nipple for the BAC(WHICH I MISS VERY MUCH). While I have a good idle at 850, I find no bac means you have a lack of the ability to fine tune the idle without the bac. IMHO.

About the AFM door slamming shut: I have a problem with that idea. When you let off the throttle on a RX7, the fuel injectors go to zip/zero output. Shutoff. That's normal and a product of the tps/ECU. So I don't see how that could cause a problem. Shut the fuel pump off?????? Well the fuel rail maintains pressure for over twenty minutes when you turn the key to off is my answer for that. And if you have a bov, does it not open and let that pressure in the turbo outlet duct route back to the front of the turbo, where the afm is sitting? I think so.

On the other hand I might just leave it as is and go for broke (GO FOR BROKE, the motto of the 100th infantry battalion in WWII, or the one, puka, puka if you will. all nisei).

RotaryResurrection

iTrader: (8)

I can only convey my ideas and my experiences. Your ideas and experiences may not be the same. You asked the question, not me.

Only at a ZERO throttle situation. What about, for instance, climbing a hill at medium throttle where you build 2-3psi and at the top you let out a little but not all teh way...where is that pressure going to go? You saying fuel should be cut then, too? So if that pressure did go out and interfere with the afm door, you're saying that fuel shutoff would be desireable and normal then?

I would say your answer is wrong. IF you've ever been in an s4 car with a fuel cut switch and flipped it off while driving under load (just for the hell of it) you know that the engine dies off before you can count to 1001. You cant seriously expect me to believe that this wont cause stumbling or hesitation at the very least. This is what I experienced in a couple of FMIC cars with stock EFI and no bov. Severe bucking was mainly noticeable when going from medium to light throttle, not so much from medium to none or heavy to none.

White_FC

Hmm werid, I never had that problem with my old turbo setup with the AFM.

HAILERS

If anything, the stock BOV would more likely close the flap in the afm, not the car without a blowoff valve. Where do you think the pressure from the BOV (stock) goes anyway? I gotta put a pressure sensor in my intake duct someday....soon.

So I can sleep better....I bought a BOV from RotaryPerformance this am. One that vents to the atmosphere and gasses lillte old ladies who smoked too much in their youth.

So while I'm here.........I got to thinking about the stock bov and using it instead of making RP richer. So I thought too much about it. The stock bov only deals with the trapped pressure in that small intercooler and piping to the throttle body. So if you have a huge fmic, you have much more volume to deal with what with the extra piping and tripple size intercooler (over stock). That's why I went with a external (?) bov.

Hmmmm. I wonder if the tinkling I heard was the afm vane doing a tinking job. Open, shut, open, shut with surging pressure when I let off. I've got a way to find out. Just look at the output voltage of the afm on the SAFC or a meter.

RotaryResurrection

iTrader: (8)

Okay, if you know so much about everything, why even ask for other opinions, just to categorically shoot them down?

RotaryWeaponSE7EN

iTrader: (6)

Oh God not again.....

HAILERS

IF you look at the last remark, you'll see I was giving your thoughts consideration. That tinkling sound I was hearing, that I'd never heard before, could be the vane in the afm slapping against its stop. The tinkle sound only happen when I gently boosted to three to five psi and it happen when I let off the throttle. And it wasn't detonation because it happen when I let off, not during acceleration.

If I knew so much about everything I wouldn't be posting so many questions. Your the touchy sensitive type, ehh? Cheeeez whizzz. Don't visit any political sites on the web for your own sake.

RotaryResurrection

iTrader: (8)

No, I mean I try to help out, but personally I could give a rat's *** whether or not you're satisfied with what I have to say. It just doesnt make any sense, to ask for people's help or ideas, and then tell them how you think they're wrong on every count. I mean, what's the point?

Cybaster

as some of us call it here, the stock "BOV" is called the air bypass valve (not to be confused with the bypass air control valve) anyways.... that vents the air back into the intake box....so why would that cause the afm door to shut?? it is designed to vent the air back in, so (and i've seen in other forums, online, elsewhere) that the air bypass valve is a better choice, venting the unused air back to the intake box.... however, those forums/people say there is a limit... the air bypass valve cannot handle such a big pressure from aftermarket turbos, so compression surge may happen, since it cannot route the air back into the intake box in time... (hence we all call it the STOCK bov) and so an atmospheric vent BOV (note: that is why it is called a Blow OFF valve, it blows the air away...(not really blow but u get the idea)) needs to be used and vent the air out to nowhere....