so I need to control the boost on the super charger, now on other SC's I see thay have a butterfly valve that opens and diverts air out of the intake so a pre-set boot pressure is not exceeded. My question.
. where is the excess pressure diverted to! Im assuming it has to be diverted to the inlet somewhere, but is it diverted to before or after ther throttle body!
beblowin,
Jun 18, 11:20pm
dont know what type of supercharger you got but sounds like you need to change your pulley ratio to reduce max boost pressure but if you got a turbo thats different again.
jsbike,
Jun 18, 11:44pm
its twin-charged, supercharger and turbo. Supercharger boosts to 10psi till around 3200rpm, then the turbo takes over and boosts from 7-14psi. The reason I need make the supercharger boost vairable is I want to be able to adjust the sc boost so its always adjusted to be boosting 1-2psi less than the turbo. I need the pressure difference between the sc and turbo to operate a bypass valve, so when the turbo boosts more than the sc, the sc is bypassed and turns off. A but hard to explain without pics
ola_bitchola1,
Jun 18, 11:48pm
toyota used a air bypass valve set at 8 psi to vent excessive boost most people bypass them to run more boost cusco made an adjustable item but their rare to find . It does this by bypassing the pressurised air back into the intake manifold
jsbike,
Jun 18, 11:49pm
into the intake before or after the throttle body!
solster,
Jun 18, 11:52pm
Is this one of the VW Golfs!.I have the M90 Supercharger on my Holden.only way to adjust boost is via the pulley!
ola_bitchola1,
Jun 18, 11:55pm
i cant remember exactly id have to have a look at my racecar to be sure
jsbike,
Jun 18, 11:59pm
no, its an nissan, rb25det neo engine, fitted with a big turbo, hence the fitting of a SC to give boost before the turbo comes in, and also it will make the turbo spool up sooner than normal as there will be more exhaust gasses at low rpm seeing the SC will be boosting. I have heard of the VW twin charge system, which was where I copied the bypassvalve I made.
Idealy I need to leave the SC pully on the SC as its electricly clutched, like an air con compressor. This will let me completly dis-engage the SC when its the turbo doing the work, and not give the engine any more drag. Also at idle it will be completly dis-engaged.
jsbike,
Jun 19, 12:01am
cheers for that!
solster,
Jun 19, 12:27am
jsbike, i would like to see a photo of that!
jsbike,
Jun 19, 1:01am
No pics at moment, basics are. turbo which has a short outlet pipe that goes to a throttle body, after the throttle body are 2 more throttle bodies side by side, this is my bypass valve. When one is fully open the other is fully closed. On the end of this bypass valve is a pnumatic actuator (its a turbo wastegate actuator), this gets a pressure line form the turbo.
In theory it should work like this.you boot it and the main throttle body opens the single one aftter the turbo outlet), this lets the SC suck in air and produce boost, rpm comes up and the turbo starts to build boost, as this happens the actuator on the bypass valve moves, this closes the bypass valve to the SC (and therfore slowly stopping the SC from producing boost)and opens it on the other side so the boost from the turbo is able to bypasses the SC and goes straight in the intercooler. The VW system as far as i know is the same except that the bypass valve only bypasses the SC rather than also blocking it off like my one does. I'll have to take some pics when its in a more assembled state. At the moment the motor is on a stand, making brackets and mockup pipes etc
beblowin,
Jun 19, 1:25am
how much boost do you require and are getting and what sort of boost pressure is the motor built for! are you trying to over come boost lag by having the s/c fitted then having too much boost because the turbo kicks in!
jsbike,
Jun 19, 1:48am
No, I just need to know where to vent excess pressure if it turns out the SC makes more than 10psi seeing I cant change pullys easily. In theory, when the sc is set up right (ie it makes 10psi) there is no way there will be too much pressure when the turbo kicks in, as when the turbo kicks in, pressurer form the turbo will activate the bypass valve and this valve has the function of bypassing the sc as well as closing off the inlet to the sc so it cant make boost.
The point of this system is not to make more power, max power should not change. its the having boost bfore the turbo kicks in Im doing this for, diveability.
beblowin,
Jun 19, 2:17am
you may cover come this by turning the s/c off when the turbo takes over
beblowin,
Jun 30, 5:00pm
in other words turn the s/c clutch off at the required rpm
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