GraphiteAccord

what the topic says, i would like to see what it looks like. I have an idea, just not complete...I would like to do this to my setup before i put it all together.

GraphiteAccord

GraphiteAccord

^^

SiRkid

geoff should have some..i dont off hand.. i have a vid of supra on the dyno with one... but the link is down now..sorry

GraphiteAccord

its cool. my friend's MR2 has it right after the compressor in the charge piping...i told him where most people with honda's put it, and he freaked out...I guess we put them too far away from the compressor...

SiRkid

i still cant see the advantage of putting it closer to the comp.... i mean when the throttle plate closes , thats where the air is being turned around and sent the other way...so you woul dthink basically pretty close to the tb would be the best spot?

GraphiteAccord

thats what i though, but i guess the bov is more efficient close to the compressor because it catches the air before it hits it...which still doesn't sound right to me. geoff needs to intervien in this asap...because i don't understand it at all.

Elite Hatch

Yah my friend has an SR20DET In his s14 I was wondering why his BOV is on the turbo side

Full-Race Geoff

youre absolutely right, it gets the signal from the throttle plate then lets the air leaving the compressor get out faster.

BTW the end tanks are a great place for a BOV. Thats where the BOV is on my personal car, and on some customers

true

I don't think it matters where you put it on a street car. We don't have lab equiptment handy. You won't notice a difference. Think about it...the purpose is to release the pressure when it senses vacuum. Ever open an air compressor valve? It doesn't car what direction air is moving..(it's not) it just rushes out. Now what do you think is faster....your foot pushing the throttle down, or the compressed air rushing back up the pipe? I have my BOV right on pipe after the IC...people talk smack all the time..it's just another common myth...like priming the turbo. You won't notice spool differences and you get bling factor because its in the bumper outside the car.

Full-Race Geoff

sorry bro, but i strongly disagree with you. it may not be a monumental difference, but there is a difference.

when designing everything to work as well as possible, these things do add up.

and it matters more on a street car than on a race car.

true

That's cool if you strongly disagree ; but, you put it on compressor side of IC and most people put it as close to TB as possible. You are saying with your setup its easily noticable the different between the 2? It's almost impossible to test, but I'm not sure I buy it. I had mine close to TB at one point, and now mine is right after IC. I cannot notice a difference. How do you measure it? If we had lab grade testing equiptment we could calculate which is more efficient, but I don't think anyone on the street could notice any difference as to the placement of the BOV on their chargepipes... No matter where you put it, it's going to be the lowest pressure point in the closed loop system. So all points on it should be near equal.... You said it's the correct way to do it, but you didn't list the reasons/advantages (that i could find) Maybe you could do that for me. Thanks.

FFgaeson

HHAHA UR BOV IS GAY STFU PLS THX

true, just drive the freaking car and stop building it already

Full-Race Geoff

there is a pressure drop across an intercooler, you arent considering also. i will post more in detail later i dont have the time right now

true

Sorry GAYson, IM TRYING TO DRIVE IT, BUT I Have to learn how to drive stick first. I keep stalling it.

Geoff...yeah good point about the pressure drop...but the %'age drop in relation would be _pretty_ constant at any given pressure right? (within reason) I look back later tonight. Thanks.


[Modified by true, 9:28 PM 11/15/2002]

Full-Race Geoff

i meant to post earlier but forgot until now, that a very very simply way to test it is with a tiny mass airflow meter, like from a 200sx 1.6 liter se, those thigns are micro. just run the hotwire sensor and see the difference in airflow between the upper tube and pre IC. theres even more reasons why but i need to finish a cpl manifolds, so ill get to this later

Full-Race Javier

i would place the blow off valve nearest to the compressor. by doing so, it relieves the pressure/force nearest the turbo which in theory, reduces shock waves.

compressible flow fluid dynamics is an extremely difficult to model.
"large pressure gradients(blow off valve) and or sudden expansions(blow off valve) sometimes cause rapid growth of boundary layers, distorted velocity profiles, and flow separations." from Intro to Fluid Mechanics by Fox and Mcdonald

shock wave movies
http://www.itsc.com/MovSWD.htm

flip1199

Sorry but i'm not even gonna try to understand that...I'll just take your word for it

vtec65

Try blowing through a straw while clamping one end with your finger. Would it be easier to allow air to esacape by letting go of your finger or letting go with your mouth? If you let go of your finger you would have to use some force to blow the air through the straw before the air escapes. Is it a big difference? My mouth says yes. Its easier to let the air escape closer to its origin.

SiRkid

ok, i think i understand it..
but i always thought it was the air going back towards the turbo from the throttle body that you had to release. i guess i had it wrong... hmm.
I will most likely put my BOV before my i/c(after turbo)!

TheSwift1

hahaa...i think he just opened the first page in his "intro" book and wrote it here...lol...

j/k..

Full-Race Geoff

actually its my fluids book, and bring it back (for the 2nd time!!) haha

that is not the first chapter, i think its like chapter 4... hehe

GOLDBERG

so wheres the best place for the BOV???would putting it close too the intake manifold be good??or closer too the turbo?anyone got pics?

Farnsrocket

Wow, I learn something everyday.
I too, always thought it was the air coming back from the closed throttle plate that was released by the BOV. Now that I think about it, I never realized the role of the vac line from the BOV you're describing......to sense vaccuum and open the BOV.....right?
Let me put this idea out and see what people have to say.
If you have the BOV close to the turbo and it releases the compressed air, won't the turbo then have to re-charge the intercooler and charge pipe before the engine gets boost????
On the other hand, if the BOV is close to the throttle body, the turbo only has a foot or so to make up before the engine receives boost.
Granted, this is probably minimal, but you said every bit counts.

true

Vtec65, your straw test is invalid because we are dealing with compressed air. Unless you keep got a 50 trim in your mouth of course.

I know we can get into math and theory of compressed air operation but my point is that I don't believe anyone will be able to tell, not that anyone is incorrect.

Here's my thought.....

Imagine a 4' straight section of 3" pipe getting attached to an air compressor. Take a pen and punch through the pipe at ANY given point and the air rushing out will be rediculous. The air on EITHER side of the puncture wound will turn direction and rush out. However, once you close it, the air will immediately be pressurized at the same constant. Our reality is gonna be a little different becaue we have air coming out and air going in the intake....but if you could freeze time, there is no 'flow'. Basic BOV antics is that it's used to release the charge when the throttle plate closes in order to stop the compressed air from slaming into the plate and creating a reverse shockwave that STOPS the compressor, or even In some cases spins it backwards! (am I right?) Now back to my orignal thought in the previous post........at the point you tap the charge system to release that air, It's been my experience that I can't tell a difference. I'm under the impression that even if you have the BOV in the most mathmatically in-effecient spot -- after the BOV closes the entire sysem will be re-pressurized quicker then you can turn your head to look at your boost gauge.

Geoff and Javier definetly know their **** and went to school so props on the calcs/thoery...I don't think a human can notice a difference though. I couldn't at least...


[Modified by true, 4:31 AM 11/17/2002]