Bypass Valve or Blow-Off Valve??

VY5Speed · #1 03-09-2007, 10:23 PM

Howdy, not sure if this is the best place for this but anyway...

In a supercharged system (Particualy a VY V6) can you change the Bypass valve to a Blow-off valve?

I have been doing some reading but im stil not 100% sure...

As far as i can understand, this is possible with a centrifugal supercharger??

Feel free to comment and correct me on any of this.

Cheers,

Raptorsc · #2 05-09-2007, 06:55 AM

Quote:

In a supercharged system (Particualy a VY V6) can you change the Bypass valve to a Blow-off valve?

No, all VS - VY Ecotecs are the same, they have an air flow meter and once it meters the air going to engine you cannot let that air back out to atmosphere, if you do engine will run excessively rich when cruising or may not run at all.

Quote:

As far as i can understand, this is possible with a centrifugal supercharger??

The same apply's to a centrifugal supercharger installation as well no matter who makes/supplies it.

The only exception is when you remove factory ECU and install a MAP sensed aftermarket ECU, then you can do what you want but plenty of other problems can come along then as well.

Questions always welcome

kranky_wagon · #3 16-09-2007, 05:13 PM

so is there any way at all to have the blow off valve a MAP sensec ECU? wat are the other problems you would find?

Raptorsc · #4 16-09-2007, 06:37 PM

There is always a way to have a BOV on a MAP sensed system but maybe you mean't MAF sensed.

The problems are very rich on decleration and idle, there are partial plumb back/external vent valves from APS which give sound for a bit (what you want) and then go into plumb back mode, work quite well.

Thats one way to do it, the valves are around $350 but designed for this situation.

fmlycar · #5 22-07-2008, 11:02 AM

Quick question. Would a turbosmart kompact dual port bov with adjustable spring tension be suitable for the cetrifugal set up with afm. Trying to get around that pigeon sound

Raptorsc · #6 22-07-2008, 05:12 PM

To be honest I do not know if any of these aftermarket valves are a good thing for centrifugal chargers, but you shouldn't have a pigeon sound, do you have the BOSCH valve?

fmlycar · #7 23-07-2008, 06:18 AM

I do have a bosch valve but at part throttle cruising and closed throttle decelerating it flutters like it's not holding the correct position either open or closed. Do you think it's possible that it's plumbed the wrong way? As the instructions with my kit didn't say how to install it. Also, Tim, could you PM me your postal address. I've been meaning to send you that paper work and lost your address.

Raptorsc · #8 23-07-2008, 06:49 AM

Kurt

To fit the BOSCH valve correctly determine which of the 2 hose fittings has a 10mm x 10mm plastic tab that extends down off the main valve body, the barb that features this little piece is the air IN tube.

It is very strange that it should be producing Pigeon sounds as these valves work faultlessly. It could very possibly be the wrong way around, if not then we can move to next possibility.

Happy to assist as always

Raptorsc · #9 23-07-2008, 06:52 AM

Actually just had a second thought on this, you have an intercooler, this means you should be running 2 of them otherwise you will get compressor surge which is heard as "fluttering" and it will eventually take out your Vortech, in fact surge which shows itself as a continous flutter is the very worst type and will destroy any centrifugal supercharger.

Raptorsc · #10 23-07-2008, 06:57 AM

Actually just had a second thought on this, you have an intercooler, this means you should be running 2 of them otherwise you will get compressor surge which is heard as "fluttering" and it will eventually take out your Vortech, in fact surge which shows itself as a continous flutter is the very worst type and will destroy any centrifugal supercharger.

fmlycar · #11 23-07-2008, 12:08 PM

So then running a dual port valve can only be a good thing then. Just going to see if I can get the one with the correct size inlet. Not sure if it's 20mm or 25mm.

VN_Luke · #12 23-07-2008, 12:26 PM

I had a similar issue in my setup (yet to verify that it's resolved) (AFM turbo setup, afm located on the intake side of the turbo)

basically, without the blowoff valve, it would 'flutter' - and you'd get air shooting back through the turbo, and then BACK through the AFM - it could be clearly seen on the logs for the AFM as 'waves' of air (it's a hot-wire afm style sensor, and it was measuring the air TWICE, once ont he way on, and again on the way out during the 'flutter')

Of course with an atmo BOV it was shooting 'measured' air out into the atmosphere, and fuelling for air that wasn't in the system

so what I've done now is run a plumb-back style bov, with a spiraled long (2m?) return hose, and increased the volume between the turbo intake and AFM as much as I can.

hopefully this will be enough to stop the 'blown out' air going back out the AFM (or minimise it enough so it's not an issue)

I also came up with an idea of using ANOTHER AFM on the outlet of the BOV - then 'negating' the value read by that AFM from the other - which should hopefully trick the ecu into fuelling for the correct amount of air.

This might be a good solution if you reallllllly want the BOV sound.

fmlycar · #13 23-07-2008, 05:35 PM

My AFM is not far before the throttle body but the bypass valve is before the AFM. Spoke to turbosmart today and they advised that the bosch valve is past it's efficiency and that a dual port with the centrifugal supercharger spec spring is my solution. Once it's all fitted I will let everyone know my result and post part numbers for future reference.