Ok, im in the process of doing a intake mod, and I was told by a reliable source that instead of just putting a check valve at the end the tube where the stock BOV is vented back to the intake, I should put an aftermarket BOV.

Do any of you have any suggestions as to what kind of BOV I should get (performance wise.. not for the sound lol)

What kind of BOV do stock s4 RX7's come with? (Air operated or spring loaded) Arnt air operated better? Should I try to find an air operated BOV like the HKS SSQ?

Some people say that the stock BOV on some cars operate better that most aftermarket ones... is this true in the case of RX7's?

Would using a BOV on a stock car cause any problems?


Im getting most of my info on general cars... not RX7's specifically, thats why im asking these questions, to clear things up.

Thanks alot

 

From what I remember using vent-to-atmos BOV on a car with a MAF will create a momentary rich condition because you are losing air the MAF has already metered.

As for an aftermarket BOV I wouldn't even bother until you start creating more pressure. Many people like the 1G Mitsu BOV's.

 

Damn, I dunno where to even start...


-Ted

 

Why don't you go ahead and find a place.

 

Ok...


-Ted

 

I dunno what this "air activated or spring loaded" thing means, but they all work basically one way...

A BOV is simply a vacuum actuated valve that vents the temporary spike in pressure due to the abrupt closing of the throttle under boost.  Without this function, the turbo goes into compressor surge which will kill the turbo.

When you lift off the throttle (under boost), the high vaccum caused by the decel will trigger the BOV to open it's valve, releasing the pressure spike in the intake tract.

The spring in the BOV is there to prevent the BOV opening under boost, when it's not supposed to.

If you want to keep the stock hoses, I think the TurboXS BOV is probably the easiest to adapt.  Other aftermarket BOV's (especially the Japanese ones) require an adapter pipe and/or mount flange.

Some BOV's can be vented back into the intake or open-vented to atmosphere.

In theory, the BOV causes a momentary rich condition (i.e. flames out the exhaust) when it does trigger, but my GReddy Type-S almost never does this on my car.  Maybe it has to do with proper adjustment of the TPS and BOV pre-tension?


-Ted

 

Boink. Reted said it...

The stock unit is said to be good for stock boost only.

I got the Apexi FC kit because it was the cheapest.
This kit can't be routed back into the intake because of the odd drilled holes it has all around the BOV.

 

hey Ted-
Why is it the greddy or any other -to atmosphere- BOV) does not create a vacuum leak, whereas the stock one does (when not cycled back to the intake). I am lost on that-

Hard to explain what i am asking, hope that made sense-

 

I can get a TurboXS Type S BOV from a guy I know for pretty cheap.

If I get this BOV can I recirculate the air back into my stock intake?

Thanks

 

Those BOV's are designed to work for "street" use, and have a very-well sealed valve internally.

"Race" units are not sealed that well.  The HKS Race units all leak slightly.



-Ted

 

I think this is the only one you can use if you want it to recirculate.
http://www.turboxs.com/rbv_h25.htm


-Ted

 

OK, so the stock one always release a slight amount of air whereas, aftermarket (eg. greddy, turbosmart, etc) have a stiff enough spring to hold the pressure.
Also i am pretty sure that turbosmart makes one for the rx-7 that recirculates-


*edit* no they don't just double checked

 

I personally use the Turbo XS Type S. And I like it ALOT. Little louder then I would care for, but thats one of the trade offs.

And I dont get big fireballs out of my car either. Proper tuning is a great thing.

Rat

 

I was the one who suggested going to an aftermarket BOV.

If your going through all the trouble of getting rid of the stock intake (box, TID etc) you might as well replace the BOV. Can you use the stock one? Yes of course but as mentioned you'll need to add a check valve to it so it doesnt leak. Check valves can be found at Home Depot but they just look like ***. There are enough reasonably priced BOV's on ebay that it just makes sense. If you don't have the money for a BOV right now, just put the project off for a bit till you do. You'll be glad you put a real BOV on and not some Home Depot hack job believe me. As for the use of and aftermarket BOV with the stock MAF, I have yet to see a problem. DSM's seem to have an issue with it but it's been my experience FC's don't have any issue that one should be concerned about

I mentioned to this user in another forum that he's heading down the usual road. Less restrictive intake means more boost, more boost requires an FCD and more fuel. Lots of kids have popped motors because of these simple type mods.

 

Guys, if your stock bypass is failing/leaking, there are some stronger ones available from Bosch. They're not all metal bling bling, but they've been shown to work just as well as most of the aftermarket ones (and they are cheap):

http://www.ecstuning.com/stage/edpd/...&productID=581

These are the same ones Porsche uses on the 996 turbo. Hell, I even have some waiting to go on my Audi S4. I know they work well, even for people running over 1.2 bar (18-19 psi).

 

Aside from "looking like ***," there is nothing inherently wrong with the homemade blow-off. Aftermarket BOVs are nice, but if the bypass and check-valves are in good condition, you're not going to get any more added benefit from an aftermarket. (With the exception of maybe the sound they make.)

 

whoever said that info about atmosphere vented bov and the "rich condition" is wrong. it would be the same as stock. before you vented this "metered air" to the atmosphere it was sent back to the TID right by the airbox, and then treated as fresh air and metered again.

 

Yes, and now its not metered...

 

Your missing the point. If the bypass air was sent back into the intake stream AFTER the MAF then yes if you vented it to atmosphere all of a sudden there would be less air than it was "expecting" But because the air is sent back BEFORE the MAF it's metering it all over again, so if it's there or not it doesnt matter. The MAF meters the flow regardless of the bypass valves contribution.

Now I agree the stock BOV and a check valve work fine, but it does look like *** in my opinion. Like I said aftermarket units are so plentyfull and reasonably priced there's no need for such a ghetto mod.

 

Uh, as rx7_turbo2 mentioned, the stock BOV vents back downstream of the AFM, so your statement is wrong.

It is still air that has already been metered by the AFM.


-Ted

 

forum hiccup... what did they do with all that dang money we donated? Go to strip bars?

 

So lets assume that the ECU is programmed for that extra air recirculated back into the motor after the throttles are released.

Either way, there is air thats no longer going back into the intake stream, which is potentially causing a "rich" condition.

 

Ted is right about air being accounted for, and the probability of a rich condition.

Basically the throttle closes, and the motor uses up the air in the manifold: causing a vacuum. The turbo will continue to spin and pressurize the intake up to the throttle body, even with the exhaust flowing much less. The manifold vacuum actuates the bypass valve, which opens to alleviate the extra pressure being built against the throttle body (which thus keeps the compressor from surging). The air is vented post AFM, and is expected (by the software) to be readily available when the throttle re-opens and the turbo goes back to spooling.

With a blow-off-valve: If you are heavy on the throttle, off throttle, and then quickly back on again: you're going to be losing a lot of "metered" air. This (like Ted said) can cause it to run richer than with a bypass. How bad will the rich condition be? I don't know. It's probably going to noticably effect your throttle response between shifts, but how badly is something that's hard to guess. Ask someone who has a BOV.

 

I'm going to have to go pull out the stock TID from the depths of my garage. I can't for the life of me remember where the stock BOV vents the air to, I was thinking it was back to the airbox, but am I wrong, maybe it's back into the TID AFTER the MAF?

Oh good god it doesnt matter people. A zillion owners have done this mod and open vented their BOV's using the stock ECU and I have never heard of anyone having a problem.