Dump/Blow off valve on 4AGZE how???

[lassetn]

How can i get an Blow off/dump valve og my stock 4AGZE in AE86



pleace Help im crasy about the sound

[jamiemirror]

If you have AFM 4AGZE, better forget about the sound (and why you need BOV with SC anyways???).

[Mux213]

Damn, I can't find the link, but that little gadget that makes the pfff sounds when you shift gear to make people believe you have a BOV springs to mind

It sure does sound cool, I have seen SC's with BOVs but I have no idea if they really add anything other then the sound.

[nmwisima]

The gze has a small BOV of itself, which makes sure pressure wont go higher than 0,8 bar.
But its for safety, not for sound. You can tap that valve if you re to use a bigger pulley, but there is almost no way you ll make the engine sound like a turbo one.

Placing a BOV will probably just cause trouble.

[Lauren]

An SC does not need a 'blow-off' valve because the supercharger is driven by the crank, also the SC is after the throttle body, not before it so all the issues surrounding turbine stall on a turbo are irrelevant.

In a nutshell you cannot do it and even if you could it would be totally pointless.

I'm guessing you already have a big pulley fitted and have junked the ABV?

With a big pulley the SC has a very distinctive sound of its own, that is arguably far better than a BOV popping and banging like a cow with excess wind.

(BTW for those that don't know me on here, i'm expert in anything to do with the 4AGZE having had and modified them for the past 6 years.)

[NoHachi]

Quote:An SC does not need a 'blow-off' valve because the supercharger is driven by the crank

Actually, an SC does need a blow-off valve...just like any compressor really. I think the GZE SC already has a anti-surge-valve fitted integrally into the housing.

The need for a surgevalve of BOV is the same between turbo's and SC's. When you suddenly shut the throttle (whether this is before or after the compressor) you get a high pressure area after the compressor and low pressure in front of it. Air tends to flow from high pressures to low pressures and this tendency will start to work against the normal flow direction of the turbo. If this lasts long enough, the end result is something called "compressor surge" which is basically air flowing in the reverse direction through the compressor.

A turbochargers wheel will stall when this happens and needs to be spinned up again when you open the throttle. A bov can improve response time.

A supercharger heats the air every time it passes through it as a result of adiabatic compression. The SC obviously cannot stall because it is always spinning from the crank. What happens is that some air flows back through the compressor, equalises pressures, flows back again into the plenum, flows back into the compressor etc etc. This air gets very hot and can lead to knocking etc. So you use a bypass valve that can equalise pressures whenever there is a vacuum before the compressor. Its a BOV that doesn't dump to atmosphere but back into the intake pre-compressor.

You can do the same thing to a turbocharger BOV, in fact most OEM manufacturers do. This air is already compressed, so dumping it to atmosphere would be a waste. If you dump it before the compressor, it needs to compres the air less and consumes less energy doing so, heats the charge less and responds faster.

[Lauren]

NoHachi Wrote:Actually, an SC does need a blow-off valve...just like any compressor really. I think the GZE SC already has a anti-surge-valve fitted integrally into the housing.

The need for a surgevalve of BOV is the same between turbo's and SC's. When you suddenly shut the throttle (whether this is before or after the compressor) you get a high pressure area after the compressor and low pressure in front of it. Air tends to flow from high pressures to low pressures and this tendency will start to work against the normal flow direction of the turbo. If this lasts long enough, the end result is something called "compressor surge" which is basically air flowing in the reverse direction through the compressor.

A turbochargers wheel will stall when this happens and needs to be spinned up again when you open the throttle. A bov can improve response time.

A supercharger heats the air every time it passes through it as a result of adiabatic compression. The SC obviously cannot stall because it is always spinning from the crank. What happens is that some air flows back through the compressor, equalises pressures, flows back again into the plenum, flows back into the compressor etc etc. This air gets very hot and can lead to knocking etc. So you use a bypass valve that can equalise pressures whenever there is a vacuum before the compressor. Its a BOV that doesn't dump to atmosphere but back into the intake pre-compressor.

You can do the same thing to a turbocharger BOV, in fact most OEM manufacturers do. This air is already compressed, so dumping it to atmosphere would be a waste. If you dump it before the compressor, it needs to compres the air less and consumes less energy doing so, heats the charge less and responds faster.

No it doesn't not on the 4AGZE. The only reason that the GZE has an ABV is for releasing excess boost when it actuates at 0.8 bar.

When you fit a big pulley you remove or blank off the ABV. No ill effects result of this. You have to do this to release the increased boost of the big pulley.

Pressure isn't an issue on the SC because the SC is not before the throttle body. In fact a GZE is more responsive when the ABV is taken out of the equation. From your reasoning you would need a BOV on an NA.

Don't forget the SC is on a clutch so it is not engaged all the time. Airflow will spin it slowly.

I fully understand the reasoning for a BOV on a turbo setup, but it is not the same on the SC setup on the GZE.

[Erik_dk]

you can get bov on your 4agze, but you need to modifi it a bit.. i have it on my.. you have to move the throtle body to after the compressor.. the you can get bov on it:-)

[MartG]

Seems a bit pointless - making quite major modifications to the inlet tract and throttle body just to fit something you don't actually need anyway

As the SC on the GZE is after the throttle body, there is no pressure build up when you close the throttle ( if anything you get an instant vacuum ) so no BOV is needed.

[ae86]

He only like the sound of PFFFFFFFFFFFFFFFFFFFFSSSSSSSSSS
BOV on a4agze is not done.
Use a open filterbox and hear the screaming sound of the charger