Not Recirculating Bov

[duffman1278]

Not too many manufacturers use atmospheric BOV's, they use diverter valves.

Diverter valve, meaning diverting air towards a different path, or aka recirculated, aka BOV.

[OM3GA]

Makes Sense.

[TimTurboZ]

I thought the actual use for a aftermarket BOV was when you run higher than stock boost levels so much so that the stock recirc valve doesn't properly do the job thus causing compressor surge. Buying an aftermarket BOV and recirculating it is what you do if your stock one isn't up to the task. Or you buy one and vent it to the atmosphere and it sounds cool But if you run it before the MAF then the ECU doesn't make your car run rich between shifts or when you let off the throtle because it never reads the air that is lost. Only issue is IDK/can't think of any car that runs the recirc valve/BOV before the MAF.....Hence why people will relocate their MAF and won't have any issues

If anything I said was wrong my bad

[biggie]

I has blow through and open BOV so I can hear that sweet JDM sound. Yeah that's it.

[OM3GA]

Yeah a blow through maf setup is the only way to vent the bov to atmosphere. Well besides a standalone obviously.

[spolitte]

Yeah a blow through maf setup is the only way to vent the bov to atmosphere. Well besides a standalone obviously.

Don't forget cars with MAP sensor instead of MAF

[OM3GA]

Im talking SR/KA/CA/RB specific

but i wont

[kouki munster]

As I said earlier, most maf cars, not running blow through, can get away running open atmosphere bov, but they will be more prone to stalling and be more likely to shoot flames/back fire during shifts. My car did just fine untill my stock tuned ecu crapped itself, and the only reason it back fired and shot flames is because the injector o-rings were a leaking at the time.

And for the guy that says that compressor surge is not bad and that it does not kill turbos, do you even know why it happens and what is going on while its happening?

Gather round every one, here comes a quick rundown on compressor surge and why it is bad.

Compressure surge happens while the turbo is spooled and making positive pressure in the intake track, when the throttle is quickly closed the pressurized air moving at a high rate of speed into the engine begins to bounce back and forth between the closed throttle plate and the compressor wheel on the turbo that is spinning at 100k+ rpm. When the air bounces off the compressor wheel it causes it to greatly reduce speed/stop spinning/spin the opposite direction for just an instant every time it bounces. This puts a very large load on the bearings in the turbo and causes them to wear out quicker.

A recirculation valve vents the pressurized air that would be bouncing back and forth, to before the turbo where it gets sucked back in to continue circulating untill the throttle is re-opened, this is the best of both worlds as it maintains good response and greatly reduces or eliminates compressor surge. The open atmosphere bov just dumps the air out, it sacrifices response but gives you the jdm tyte sound that drops the lady's underwear. (also easier to set up and gives a cleaner looking engine bay)

[mrgreeneyes]

lets see a show of hands as to who has ACTUALLY KILLED A TURBO by running no BOV.

who has REALLY had it happen to THEM personally? and if you just killed a T25 thats 20 years old, that doesnt really count.... its a 20 year old turbo....

and when you say "it will kill it", you need to be more specific. what are the REAL WORLD timeframes for life? turbo only lasts 5 years now? what if they are only running 12psi?

it sounds like a lot of you are just regurgitating internet mechanics' words. aka "my buddy said this, and he sure does know an awful lot, gee willikers"

besides. who the hell cares about T25 non-bb lifespans anyway. they are disposable at the $100 or less it costs to acquire one, and the $40 to rebuild it.

get your heads out of your asses and open your minds to the possibility that there are alternatives to the drivel that youve been spoonfed thusfar.

/rant.

[S14toRPS13]

lets see a show of hands as to who has ACTUALLY KILLED A TURBO by running no BOV.

A valid point. I blew my old HKS GT2530 pushing around 20 psi, but it didn't happen during light driving when I was getting the slight compressor surge. It happened under full throttle when my bov was fullly functioning. Like I said before, most people I know who runs 240's, DSM's, and Subies all run atmospheric BOV and haven't had issues for years. Once again, the debate goes on....

[kouki munster]

lets see a show of hands as to who has ACTUALLY KILLED A TURBO by running no BOV.

who has REALLY had it happen to THEM personally? and if you just killed a T25 thats 20 years old, that doesnt really count.... its a 20 year old turbo....

and when you say "it will kill it", you need to be more specific. what are the REAL WORLD timeframes for life? turbo only lasts 5 years now? what if they are only running 12psi?

it sounds like a lot of you are just regurgitating internet mechanics' words. aka "my buddy said this, and he sure does know an awful lot, gee willikers"

besides. who the hell cares about T25 non-bb lifespans anyway. they are disposable at the $100 or less it costs to acquire one, and the $40 to rebuild it.

get your heads out of your asses and open your minds to the possibility that there are alternatives to the drivel that youve been spoonfed thusfar.

/rant.

Thats not realy a good question to ask, because how many people do you know that don't have some sort of a bov on their turbo car? How many factory turbo cars don't come with recirc. valves?

I can't really say how long they will last without a bov, I'm not an engineer and I don't have the resourses to to do the testing to find out, but anyone with decent mechanical understanding will be able to grasp the concept of compressor surge, what is going on to cause it, the forces that are applied to the shaft and bearings in the turbo, and be able to understand that it can decrease the life of the turbo. But by how much is hard to say because there are other things that need to be factored in that affects how long a turbo will last.

Also just because the motor came stock with a non bb t25 doesn't mean thats what is still on it. People that spend $1000+ on a upgraded turbo like the piece of mind knowing that a bov of some sorts will help prolong the life of their investment.(And some just like the sound)

[mrgreeneyes]

but if theyve spent "$1k+" then its probably ball bearing and is a moot point, good sir.

and its a PERFECT question to ask... too many people are quick to say "this is bad" but without ANY tangible proof or real life experience. its ALL hearsay from this point.

everybody overthinks/ too quickly spends money on "go fast" parts, just because they are common does not make them ideal.

there will ALWAYS be a tradeoff. overall turbo life vs response/minimal boost loss between shifts...

you can take a wild guess as to which id learn towards.

[TheRealNap0le0n]

i dont see how you can say not running a BOV helps response.... if you are stopping the turbo when you close the throttle then it has to spool up again anyways....

sooooo if you run a properly set up BOV you will have better response...

and if it really is a factor to have no lag period you can just run a flat shift program in the ecu that way you dont have to close the throttle to shift....

in the end whether you are spending $140 on a reuilt SR t25 or $1000 on a BB turbo whats another ~$200 or so for a good BOV

[mrgreeneyes]

ummmm maybe cus it doesnt bleed the BOOOOOOOST thats in the charge pipes/IC....

think a little bit there boss.

and i wont buy a BOV cus turbos are cheaper than BOVS.

[TheRealNap0le0n]

which brings me back to flat shifting....

if the fact that bleeding BOOOOST when you shift is the only thing keeping you from getting a BOV then why not save the turbo by getting a BOV so it doesnt surge when you are piddling around town and when you are at WOT when you need the BOOOST you can flat shift thus by-passing the BOV from letting the BOOOST out...

best of both worlds..... think about that a bit hoss...

[mrgreeneyes]

alright cool.

ill buy a bov now. whats the coolest one to get?

[TheRealNap0le0n]

the hks ssqv sounds like a laser.. pew.....

im just giving options instead of telling ppl NOOO DONT BUY THAT ITS USELESS!

but im sure you think compressor surge sounds awesome

[ILoveMyRHS13]

Sarcastic Keegan is sarcastic.

You watch, us Lancaster kids will start the "BOVs are gay" trend.

[mrgreeneyes]

im just giving options instead of telling ppl NOOO DONT BUY THAT ITS USELESS!

but im sure you think compressor surge sounds awesome

the "option" part is legit. ill give you that. recirc'ed is viable. i dont prefer it. ill spend that $200 on gaskets/etc.

i LOVE surge noises

im glad to see youre starting to see my sarcasms and can roll with em. too many people on here get butthurt.

IF i were to run a BOV, id DEFINITELY run recirc'ed from the hot pipe. but for what my car is for and my personal preference, ill be running no BOV

[Magnum375 Jr.]

Hahaha, Yeah, I'm def. gunna say that a BOV is def useless vented to atmosphere, and it kills the life of other parts, like a starter, OMG, if i had a dollar for every time i've had to restart my car because i roll up to a light and put the car in nuetral while decelerating, and it dies, I'd have a BB turbo by now. Seriously, recirc is how it came stock, you think they did it for a reason???? But I'm a fan of no BOV too, its the best way to keep boost response. I am so looking forward to my new setup coming soon.

[kouki munster]

ummmm maybe cus it doesnt bleed the BOOOOOOOST thats in the charge pipes/IC....

think a little bit there boss.

and i wont buy a BOV cus turbos are cheaper than BOVS.

Yes used stock t25's are cheaper than a good bov, and if thats all the power you want then go for it, but the guys that want more power than the tiny stock turbo can provide(raises hand) and have spent the $1000+, like having a bov for the piece of mind that it will help to extend the life of their turbo weither it be ball bearing or journal bearing by reducing extreme forces on the bearings.

Also I don't think that there are to many turbos that get to the point of bearing failure, because as the bearings wear shaft play will increase, that will cause the oil seals to give out, make it start to smoke, and cause the car to run poorly which would be the point where most turbos will be replaced/rebuilt.

Also recirc. valves don't bleed pressure out of the charge pipes, they just provide a path for the air to continue circulating untill the the throttle opens back up or untill the pressure in the pipes drops.(the engine finaly uses all the extra air) If you think about it, it would seem that a recirc. valve would give better response because it keeps the air in the pipes and keeps the air from bouncing back and forth and slowing the turbo. But I think I'm just over thinking the whole thing now.

[mrgreeneyes]

ok, to clarify, im more interested in the transient response of spool/"despool" while in mainly 3rd or 4th gear for grip driving, and holding nice boost at the top of 2nd and 3rd for drift.

most of the time on longer courses (what are available to me) i stay in one or two gears the whole time so i dont need to release pressure nearly as often as the average joe.

i definitely see your point about recircing, BUT it DOES bleed PRESSURE, but places the air MASS at LOWER pressure right in front of the turbo which will be pulled in via venturi effect into the turbine inlet.

and once my freshly rebuilt blacktop is in the car, ill be running t25(rebuilt), oem inj and oem maf/tune. i still plan to run NO BOV with my later setup which will consist of S15BB, 700cc inj, Z32 Maf, and tune. that setup should put me right around/over 300whp with incredible response.

ive noticed your engine bay looks clean Koukimunster and that you seem to make good power, id be interested to see the specs on yours

oh, here's a shark pic collection


Modified by mrgreeneyes at 11:43 PM 12/28/2009

[OM3GA]

This thread has good argumentive information.

Those shark pictures are an amazing addition as well and im not being sarcastic.

[kouki munster]

My setup is a good bit laggier than what you are going for, full boost just just after 4k, but it hits like a ton bricks. I can break traction at will in 1st and 2nd on 15 psi, add 3rd gear to that at 23 psi.

I'm running a s14 sr, stock short block, unported head, arp head studs with cosworth hg, stock intake manifold, crower 264 cams with springs and retainers, tomei exhaust manifold, and a t2 flanged 20g with a td06 hot side.

For engine management I'm running a haltech ps1000 and a set of 740 cc injectors, which are just big enough to keep up with the 20g.

I haven't put it on a dyno yet as the waste gate actuator that is shipped with the turbo is worthless,(can't hold higher pressures throught the full rpm range) but I've seen similar setups make just north of 400. (Over 450 with race gas)

What exhaust manifold are you planning on running? Based of your want for maximum response, I would suggest you get the stock manifold extrude honed. I was originaly planning on running a honed stocker but when I started pricing it the tomei was only about $100 more and I figure it gives about the same response as the as a honed stocker would.

Edit: The shark pics are freaking awesome.

[OM3GA]

Nice setup, im definitely going with the Tomei manifold as well, i love that thing.

[J14cm7]

There is alot of good info here guys and the debate seems to come down to what purpose you are using your car for and whether or not you like replacing your turbo. I just had a general question because after hard runs my car usually stalls if i dont rev the engine afterwards. I have a S14sr20det stock engine. Greddy FMIC, HKS BOV, stock sr MAF. My BOV is mounted cold side and its atmospheric. I know whats causing the stall and am alot more knowledgeable now after reading this forum. In your opinion is it better recirculate it into the intake after the MAF, OR, mount the MAF hot side or possibly even cold side after the BOV? Also i would imagine that this would cause you to get your hot pipe REfabricated if you ever decided to upgrade the MAF in the future. I hope this doesnt spark another debate but one should be better than the other. Also dont say eliminate the BOV cause i already have it and i like it so its staying. besides garrett T28 turbos arent cheap.

Thanks in advance

[bersh240]

im confused.doesnt all this just depend on your personal setup?my bov is vented to atmosphere. it makes funny noises. but i dont have boost response issues..

[kouki munster]

You would be better off recirculating it, the main reason being it will be eaiser to add a bung between the turbo and maf and run a hose from the bov to said bung. Otherwise your going to have to cut the charge pipes, plug the hole for the bov,(if its in the same general area as mine) and have the bov flang moved.

[kouki munster]

With a small factory turbo only the most anal of people(response junkies) will notice(or care) a loss in response between open atmosphere, recirc. or no bov at all.

[OM3GA]

Where can you get said bungs? I need to get one for my hotpipe to use a boost source for my waste gate also, but id like to be able to find 16mm/ 5/8" bungs as well.