earl

I have been told that running a blow off valve on a drag race only set-up is un-necessary. To me, everytime you let off the throttle from a boost position, it will throw the compressor into a surge condition. Overtime, this would be hard on pistons, valves and the turbo itself. What's your opinions?

B18EG6

I dont know how accurate this is, but I was told...BOVs arent on them because they dont care about the longevity of the motor.

Again, just passing on what I've heard...

bambooluv

Well if you look at the cars that run with and with out it you can pretty much make out a decision .I talked to Greg ( stephs crew chief ) awhile back on weather or not to run one. WEll like you said earl everytime you get off the pedal theres suge. he dosent run one because of the tranny which is basically a auto he said, where in you really dont need one because the pedals to the meadl the full pass. but he did have problems with the tranny he said and suge blew some shiet up. if you look at his intake manidfold and hood theres holes in it and fiberglass repair .So i think it should stay.-pdang

D-Man

i dont see many turbo race cars without BOVs.I guess id only try it if i was using an automatic tranny and didnt have to lift on gear changes.

Full-Race Geoff

yep, auto trans no bov, manual trans, use a bov.

BlueShadow

yep that's what I was thinking too...dont they have heavy duty hydraulic or pnuematic sequential trannies, with which they just shift without letting off the throttle?

ninesecteg

not really necessary on todays big shaft turbo's. innovative turbo will tell you the same thing.

cock head

yep, auto trans no bov, manual trans, use a bov.

Why?

CzanSOHC

Because the butterfly vavle in the throttle body does not slap shut w/ an auto trans.


[Modified by CzanSOHC, 10:23 PM 1/4/2003]

rice4life

iTrader: (3)

even with auto tranny, you still have to let off the gas at the end of the track, and you're usually at full boost at the end of the track. on manual tranny, you can use full throttle shift to keep the throttle open.


[Modified by rice4life, 10:43 PM 1/4/2003]

cock head

yeah but what about when you let of the gas in an auto, I drive a 5 speed and when I shift I don't lift of the gas while raceing, so does that mean I dont need one either?


[Modified by therumblingteg, 6:45 AM 1/5/2003]

TurboITR

earl you just gotta lock geoff up in a closet and get him to finish the design for the BOV to vent back into the manifold collector like all those rally cars have

Full-Race Geoff

ive been looking into that even more have you seen what it really is like? its crazy bro... a mini engine...

earl

Yeah, Nick, Ola did tell us that.
However, say you get a little crossed up in a drag race. You let off the gas for an instant and throw the turbo into a surge condition. You put your foot right back into it. What will happen? Does the surge bog out the engine to where it takes too long to recover or can you come out of the surge to a clean full boost? To be honest, I don't have a clue...

Sonny

What if you're full-throttle shifting it? I'd assume that most of the fast drag cars do this, no? Manual trans or not...most standalones support this feature, no? I know that you can do it with Hondata (albeit, it's nog an ignition cut) and I'm pretty sure that you can do it with the others as well.

Sonny

Full-Race Geoff

look at it this way. a bov cant do anythign bad, so why not run it?

earl

What if it is leaking boost and you didn't know it?

hondaswaper

not on a Greddy type R with the stiff spring

Full-Race Geoff

wont you be able to tell on the dyno? the spring rate and valve behavior wont change.

integra_gsr98

Boost leak tests are always a good thing. I'd imagine a stiff spring in a Greddy Type-R would be good for at least 40 psi. I know guys are pushing the Type S as high as 30.

And you can always re-route back into the intake pipe to make sure your spent air is put to good use between shifts or when you let off the throttle.

rice4life

iTrader: (3)

i dont think it's a good idea to re-route the air back into the intake pipe if you use a regular air-air intercooler because the compress air is hotter than the ambient air. if you have a liquid-air intercooler with ice in the tank, then the compress air might be cooler than the outside air. just a thought.

BudaKai

I think the main concern is that you have to spool up again if you let it blow-off. With their cars I'm sure they can afford to rebuild turbo's and buy new ones. Osn't Steph using a modified VW microbus tranny?

I tend to agre with that, but even with an air-liquid you don't fully cool the air back to ambient so you can get a compounding temp. As in everytime it runs through, it gets hotter. How-ever with a 8 sec pass I don't think it really matters.

TurboITR

i think the main concern is backpressure coming through the pipe pushing the BOV valve back down...

but im no engineer which is why i leave it to the experts...i cant wait to see someone (cough geoff cough) come up with a design for this...


[Modified by TurboITR, 1:06 AM 1/6/2003]

VaporTrail

I would run one for the sake of longevity. Plus, if you don't have anything venting pressure, then you run a chance of losing a i/c connection when you do lift, which with high hp FWD's is a somewhat common thing. I would use one or two HKS SSQ race valves, their design makes boost leaks near impossible.


[Modified by VaporTrail, 3:23 AM 1/6/2003]

Cyber ITR

prolly they dont use bov , cuz they dont wanna spend time building up the boost again , hell they usually do flat shifting anyway
i've seen so many drag GTRs with air-shifted gearbox , they never let the throttle off