alternitive to BOV idea

[matt1967]

This is nothing I plan to do, to my car, but it was an Idea I had for those with manual trans's and turbo's. what about rather than running a BOV, run an extension off the carb hat, like a big chamber that can hold maby 1 gallon or better of air, put a butterfly valve between it and the carb hat, but a good valve, using teflon or some kind of seal so it is perfect with no leaks, then control it with linkage from the throttle on carb/ Throttle body so it opens when the throttle is fully closed, but can only be fully closed or fully open ( slider's and cams could do this ). that way the turbo could always be spooled and not have backpreassure on the turbo, could even have a BOV set at a low preassure to enshure this. on an automatic, this effort would be useless but on a manual, could be helpful.

 

[wallaka]

Sounds overly complicated for little to no gain. If it even works.

A properly wastegated and BOV-equipped car (and right size turbo) has little spool time anyway.

Besides, what happens when the valve opens? A huge surge of compressed air...doesn't sound too good.

 

[matt1967]

Sounds overly complicated for little to no gain. If it even works.

A properly wastegated and BOV-equipped car (and right size turbo) has little spool time anyway.

Besides, what happens when the valve opens? A huge surge of compressed air...doesn't sound too good.

it wouldn't surge too much, if the carb hat had a 2" or so pipe running to the chamber ( valve would be on the chamber side ), it would flow at a lower preassure than under full boost, because there would be more area for the same amount of air.

 

[Anonymous]

like a big chamber that can hold maybe 1 gallon or better of air

too small.

 

[XFlow_Fairlane]

it would pressuize before you even finished lifting off the gas pedal.

 

[I66coupe]

Couldn't you seal the trunk and run the pipe back there? :roll:

 

[wallaka]

Should run it into the passenger cabin. All the extra oxygen will make the reflexes better.

 

[Anonymous]

on an automatic, this effort would be useless but on a manual, could be helpful.

I don't see why. A BOV just releases the pressure that's there when the throttle closes....the turbo is still spinning. When the BOV closes as the throttle opens again, boost will be there. (if you are shifting right)

 

[Anonymous]

In a "normal" factory turbo setup (volkswagen, saab, audi) the "blow off valve(BOV)" is called a recirculation valve and it is the same thing except... instead of the excess air being vented to the atmosphere it is recirculated to the inlet side of the turbo (between the air box and turbo compressor housing). This is done because the excess air will have oil residue and sometimes a small amount of fuel so for environmental purposes shouldn't be vented to atmosphere. A BOV and a recirc valve do the same thing, they don't allow air to stack up against the throttle body which in turn back feeds to the compressor wheel dramatically dropping compressor speed resulting in Lag/respool time. All turbos will slow when you shift a manual because you let off the throttle creating a large vacuum (no engine load) in the engine which reduces exhaust gasses which slows the turbine/compressor. A fast acting BOV is about the best way to keep turbo reaction time to a minimum, but a properly sized turbo also has alot to do with the reaction time. If the turbo is too large and takes forever to spool anyway there is a good change it will take longer to react even with a good BOV.

my 2 cents
Nate

 

[wallaka]

In a "normal" factory turbo setup (volkswagen, saab, audi) the "blow off valve(BOV)" is called a recirculation valve and it is the same thing except... instead of the excess air being vented to the atmosphere it is recirculated to the inlet side of the turbo (between the air box and turbo compressor housing). This is done because the excess air will have oil residue and sometimes a small amount of fuel so for environmental purposes shouldn't be vented to atmosphere. A BOV and a recirc valve do the same thing, they don't allow air to stack up against the throttle body which in turn back feeds to the compressor wheel dramatically dropping compressor speed resulting in Lag/respool time. All turbos will slow when you shift a manual because you let off the throttle creating a large vacuum (no engine load) in the engine which reduces exhaust gasses which slows the turbine/compressor. A fast acting BOV is about the best way to keep turbo reaction time to a minimum, but a properly sized turbo also has alot to do with the reaction time. If the turbo is too large and takes forever to spool anyway there is a good change it will take longer to react even with a good BOV.

my 2 cents
Nate

The MAIN reason that the OEM's do it that way is to not throw off the computer. The amount of air in the system stays metered correctly.

 

[Anonymous]

The MAIN reason that the OEM's do it that way is to not throw off the computer. The amount of air in the system stays metered correctly.

Correct. If it would blow into the atmosphere, you are venting METERED air = very bad and engine runs very rich.

The reason for the bypass valve is to circulate the metered air back through so the engine doesn't go rich. I will have the same system on my turbo'd 1997 GT.

 

[66Sprint6]

For the money you would spend doin that, plus the effort, just put a BOV on there and KNOW itll work right. If you dont like that, put a recirculating BOV and run the recirc. hose back into the intake in front of the turbo.
Matt