supercharger boost increase = please explain!

[smidge]

hey guys, i'm trying to convince someone that putting a bleed valve on the yellow line near the UFO will up the boost on the supercharger

can someone please explain to me how that ups the boost? as i thought a pulley change was the only way to spin the supercharger quicker for more boost


please explain!!

 

[Snikty]

Haha I am probably the only one who will appreciate the humour of 'please explain'!

Anyway, as far as I understand the s/c unit is capable of more boost so by using a boost controller on that line you could regulate your boost level (and increase it)but only to a certain point, at which point you would need to alter pulleys or whatever. I seem to recall baz saying once that the s/c will do 1 bar or something like that. You would only need to alter pulleys if you wanted to go higher than what the actual unit was capable of, and like all cars the stock setting are below what the unit is capable of, so there are gains to be made without altering the unit. did that make sense?

 

[Baz]

I'll explain!!!!:laugh:
From what I understand is you bleeding air off the yellow vac line ,what it actually doing is holding the bpv slightly open and the turbo is supplying the extra boost. Sounds weird I know but I have a swith on my s/c to turn it off and if I do turn it off and put the shoe in at say 2k rpm I see roughly 0.2bar boost coming through from the turbo until 4500rpm then 1-1.2bar after that to 7k.If the bleed valve is taken out or closed off and the s/c is swithed off you get 0 boost. Its fooling you really but I find the car pulls alot nicer.
The proper way obviously would be to put a different pully on there.

Beware of some small idling problems from bleeding unmetered air,things usually stablize after a few seconds

 

[linz0577]

so on a bleed valve with a 3 way inlet outlet thing do you plumb the middle connection in after the maf? so meters the air flow meter.i just want to know if i need to get a 3 way inlet type or a 2 way basically just cut yellow vac line and put it in between. cheers lads

 

[Baz]

so on a bleed valve with a 3 way inlet outlet thing do you plumb the middle connection in after the maf? so meters the air flow meter.i just want to know if i need to get a 3 way inlet type or a 2 way basically just cut yellow vac line and put it in between. cheers lads

Yeah exactly what I've done(Y) very little adjustment gives me a bar boost so be careful I had 1.8bar at one stage,make sure its lockable(Y)

 

[linz0577]

cheers mate. look in your paypal.

 

[Ed]

The SC will make MUCH more boost. You don't need to touch the pulleys at all....

 

[smidge]

Ed, just curious how that works i would have thought with the clutch engaged it can only spin up to a certain RPM and only a pully would make it faster and only spinning it faster would actually make it pump more air, if its capable of more, where is the excess air being bled off to?

 

[warren]

s/c

ok ed how can you increase the boost on the s/c without changing pulleys??

 

[Ed]

You all seem to forget that the supercharger boost is controlled by the BYPASS VALVE.

It works in EXACTLY the same way as a turbo waste gate. Why do you think that we all get these 'ufo' issues? ITs when the damping of the bypass control valve is not working correctly so it goes into mechanical oscillations, causing the boost fluctuations.

I suspect that if you fitted a mini suspension damper from say a RC car to the butterfly valve in the bypass control valve supercharge boost would probably be totally smooth and the 'ufo' issues would not occour.

Anyway my point is, when you reach 0.7 bar the bypass valve begins to open to bypass air and thus control supercharger boost. IT also HAS TO DO THIS to enable turbo bypass once the turbo is on boost.

Another point to remember is that the SC is at all times assisted by the turbo, even when the turbo is in a region where it cannot sustain itself. This is because the supercharger will create a great deal more exhaust gasses spinning the turbo far sooner than it would otherwise, thus making boost and meaning the supercharger has less work to do, but again it has to be controlled via the bypass valve to work correctly.

Get it ?

If you bleed off some of the boost that opens the bypass control valve then it will open at a higher boost pressure and more s/c boost as a result.

Those things will make more than 1.5 bar if running without any boost control. You would instantly hit the ECU boost/load cut with that....

Ed

 

[Baz]

You all seem to forget that the supercharger boost is controlled by the BYPASS VALVE.

It works in EXACTLY the same way as a turbo waste gate. Why do you think that we all get these 'ufo' issues? ITs when the damping of the bypass control valve is not working correctly so it goes into mechanical oscillations, causing the boost fluctuations.

I suspect that if you fitted a mini suspension damper from say a RC car to the butterfly valve in the bypass control valve supercharge boost would probably be totally smooth and the 'ufo' issues would not occour.

Anyway my point is, when you reach 0.7 bar the bypass valve begins to open to bypass air and thus control supercharger boost. IT also HAS TO DO THIS to enable turbo bypass once the turbo is on boost.

Another point to remember is that the SC is at all times assisted by the turbo, even when the turbo is in a region where it cannot sustain itself. This is because the supercharger will create a great deal more exhaust gasses spinning the turbo far sooner than it would otherwise, thus making boost and meaning the supercharger has less work to do, but again it has to be controlled via the bypass valve to work correctly.

Get it ?

If you bleed off some of the boost that opens the bypass control valve then it will open at a higher boost pressure and more s/c boost as a result.

Those things will make more than 1.5 bar if running without any boost control. You would instantly hit the ECU boost/load cut with that....

Ed

Thats a ####ing Excellent post, I did understand it just did'nt have the vocab to explain

 

[warren]

boost

ok i didnt fully understand it ed but i will talk to baz in person and im sure he can explain to me what that all ment haha but thanks for the info anyway(Y)

 

[smidge]

thats top info. Whats the little solenoid that pokes its rod out inside that butterfly valve??

 

[Ed]

That holds the valve open at idle I believe to stop the air having to pass the s/c I cannot remember the exact conditions it works under its been a while since I looked at that.

 

[Baz]

Always wondered what that was for. You get my Pm Ed

 

[linz0577]

what is the ECU boost/load cut limit as i plumbed my boost controller in and it won't let me turn it up anymore than 1 bar but i know some of you are running 1.2 bar how do you do this with out it hitting the limiter?

 

[Baz]

what is the ECU boost/load cut limit as i plumbed my boost controller in and it won't let me turn it up anymore than 1 bar but i know some of you are running 1.2 bar how do you do this with out it hitting the limiter?

Not gona really be getting enough fuel John

 

[linz0577]

ahh i see... remap time