junk240sx

With MAF, is it usualy recommended to recirculate the air back into the intake manifold?

IF SO, would a scenario like this work? I've heard that some place their MAF closer to the intake manifold (after the turbo and IC). If that's the case, I can imagine placing the BOV right between the IC and Turbo. Then any air going out of the BOV won't throw off the MAF. What do you guys think?

JR.h1jax0r

the car will still only read volume. the air is condensed, so more air is crammed into the same volumetric space. The car will think you have X amount of air coming in when you really have more than that due to compression. Then X amount of gas will be sent, but you really have more air than the car thought and you run ultra lean. A true reading has to be taken before the turbo when the air is uncompressed. Mass Air Pressure (MAP) sensor can be safely placed after the turbo and IC (it's usually situated into the intake manifold) because it reads the pressure the air is giving out. it's also the only sensor that i would say works with a BOV, otherwise you need to run a recirculating bypass valve.

junk240sx

Oh well, I just wanted a loud BOV and thought that might work. But as long as the BOV recirculates back into intake manifold then I can still use the MAF right?

ftrs13

actually you could do that without problems. that is why its called a mass air flow sensor, because it measures mass and not volume.

people have done it successfully. the only problem is that you have to have an intercooler because if the charge air temps go up, as they will, you will ruin your MAF.

junk240sx

Hmm...two people telling me two different things. What do I do? :S

Well, I DO have an intercooler. Since I"m using ghetto piping, I guess I could move it around fairly easy just to test things out. Just hope I don't ruin the MAF....not a cheap replacement.

skatanic28

ive heard of a few people doing that and its workin for them
there was some concern with the pressure backing up during shifts and causing a bad reading, but apparently thats negligible. when i finally get the money i plan on the blow thru though.
make sure ya have a couple inches on each side of the mafs too.
let me know how it turns out

noss

have you ever considered a hybrid bov if you want the noise but you want your car to run well with a maf?

this is from the gfb (go fast bits) catalog. turbosmart also sell a similar item.


the reasons the problems occur is because you are releasing the air to atmosphere that has already been metered by the mass air sensor, and when it blows off, the ECU will be injecting the wrong amount of fuel into the cylinders. the engine temporarily runs extremely rich.

its not hard to overcome this problem and many people around the world run vent to atmosphere bov's on maf cars.

also there shouldnt be any pressure build up when running a bov, as its job is to release any build up pressure to prevent damage to your turbo & throttle plate. if you are experiencing problems, your bov is too small.

junk240sx

Good info! THanks.

Speaking of this topic though, it would SEEM that if you just vent it then, you could possibly get backfire after letting off gas after full throttle?

It would seem logical doesn't it? You're driving full throttle and you push let go of the gas and push clutch in to shift...BOV opens and releases all pressure...ECU shoots tons of fuel and you run super rich instantly, shooting a flame out the back....and spooling the turbo up and ready for the next gear and with a spooled turbo.

Prob not but sounds like that's how it would be.

noss

yeah the purpose of the bov is for the turbo to keep spinning at as higher rpm as possible.. therefore limiting lag & expensive damage. if the bov wasnt there, the air would hit the throttle plate, travel back down to the turbine & then slow it/stop it/spin it backwards which ruins the bearings..

you wont shoot flames out the exhaust unless your exhaust pipe is extremely hot. the larger your exhaust the cooler the gasses will flow & therefore the cooler exhaust pipe, which means no flames

also keep in mind that if unburnt fuel is passing through your cat converter it will damage/melt it.. obviously as a result this blocks your exhaust up & you lose hefty ammounts of power.

chriswgsx

I vent my BOV. It will feel like it wants to stall out a little if you go from positive boost to neutral fast, but it doesn't stall. From the factory i believe the sr20 is recirculating, but i really don't have many problems. In my eclipse i use an hks vpc which replaces the mass air flow sensor. I think you could find one with a chip for an sr20. i don't know about the ka. i also don't even know what you are running. Ka or Sr?

emericanchaos

the point of a BOV is to relieve pressure in the intake tract. when you let off the accellerator the throttle plate closes with the turbo still spinning. this causes pressure to rise in the intake plumbing. the valve allows you to 'blow off' pressure either by releasing to atmosphere or blowing it into extra plumbing and/or plumbing it behind the throttle plate and into the manifold where there's more volume.

the idea of a BOV in general is to blow excess pressure off and prevent turbine compressor damage. nothing to do with keeping the turbo spooled. that would be the reason to upgrade to a stiffer valve.

Romeyo07

Compressor surge is bad, Mkay........

element

if you have a recirculating bov, will you still get that bov sound? the loud "PSSSHHHHH" ?

i'm thinking probably not, but i'm not a turbo guru....

ftrs13

no, you will not get a loud psst, in fact on mine I get none at all. but its a factory BOV from eclipse, on low boost.

it will be muffled by the piping, and probably wont give much to any sound.

noss

ok, so if you had no bov at all, and the boosted air in the intake slams up against a closed throttle plate, where do you think it is going to go? you think its just going to sit there like its at a red light and wait for the throttle plate to open again? no its not. sure pressure is going to build up a bit, but it is going to go backwards towards the turbo to try to relieve this pressure, and then in turn attempt to spin the turbine backwards and in some cases it actually will. that is why the turbine is damaged. i didnt forget about turbine damage, as i said:

the same reasons a bov prevents damage is also why the turbo will maintain higher boost levels between gear changes.. it is the effect i just described that causes both the lag on gear changes and the damage. this is common sense basics of turbos if you agree with it or not, that is the way it is.

this is from mrt, a highly respected performance shop for wrx's in australia, you can find the page i quoted from here

http://www.mrtrally.com.au/performance/howbov.htm

need i say more? i'm not the type of guy to shoot my mouth off with false information. i'm not here to waste peoples time.