See FAQ731-376: Forum Policies for tips on use of eng-tips by professional engineers for professional engineers I also noticed the vast majority of real professional knowledgeable full time working professional engine designers are not bothering with this thread. To be frank I really can' be bothered contributing to this. I can understand OEM investing huge resources and going to all the trouble to squeeze some extra power out of a restricted space and still retain reasonable economy, but a hot rodder chasing maximum power is really wasting a lot of time and effort and really decreasing safety to save a minimal amount of fuel. The bent throttle shaft problem does not exist if the throttle is upstream. The bypass valve synchronisation problem does not exist if the blower is not clutched and there is no bypass. I'm talking about all those systems where the supercharger is not clutched and where the throttle is in the inherently safe position upstream of the supercharger.Ī roots blower does not consume much power when it runs in a manifold pressure that is typical at closed throttle. RE: Supercharger bypass valve operation patprimmer (Publican) 22 Dec 08 05:55 Pat, which charging systems are you referring to? All systems use this bypass open at idle, if the SC is clutched. Where is your throttle placed? Do you use the electromagnetic clutch? What is the car used for? Using this method would result in a very noticeable moment when the gate changes position and would probably break something eventually. It was also fitted with a clutch.Īlternatively, applying full voltage to the actuator will hold it closed. The old MR2 SC just operated the valve when MAP determined. In reality the control is a mix of these two plus other factors. Closing the valve at very low MAP levels would offer the supercharger to work when it is needed, but the valve must then stay closed as the pressure rises. Using a linear coefficient over a certain rpm range and TPS signal would be the easiest. It would then be up to you how to control the valve. The TPS and MAF sensors can both offer an electronic signal that can be sampled and converted into a duty cycle by a simple chip and circuit, or you could use an already interfaced chip with PWM functionality. The bypass should normally be operated using a pulse width signal to give proportionality. J79guy RE: Supercharger bypass valve operation 70btdc (Automotive) 22 Dec 08 05:32 Yes, the newer cars' bypass valves tend to close "slower", but this is a function of several parameters that the VCM monitors to give the smoothest torque rise. A pure MAP controlled valve is stone simple, but you may have to slow the valve rate a bit by restricting the sensing line. The ultimate would be to use a pure microprocessor controlled bypass valve and the necessary programming to control it to give smooth operation, and yet reasonable throttle response, but in your particular application you don't indicate the end-use, so I can only relate what experience I've had with Eaton superchargers that have bypass valves. The Ford Thunderbird 3.8L supercharged cars had pure MAP actuated bypass valves, and yes, the boost rise was fast giving great throttle response, but you could quite perceptably feel the boost come on, and the cars were a bit "lumpy" to drive. In a racing application this may be acceptable, but for daily driving, it can get annoying. Ok ive started the engine with the hood open and i can hear a noise on acceleration and deceleration, ill describe it best i can, it is coming from just behind the oil filler (grey rocker cover between the radiator and the oil filler, that area of the rocker cover, not the red rocker cover area) i would describe it as a slack chain type of noise, i say this because the timing chain on bikes sounds like this when the cam chain adjuster is wore out, is this normal? I think the car will need to be under load for it to leak real pressure, there is no obvious hiss.Back to the OP, mechanically operating the bypass valve, obviously is the most simple method, but can lead to some abrupt boost pressure changes, and thus effect driveability. Would it be intermitant though, if its a split pipe on the S/C, with your suggestions of diagnosis that is, if it is leaking some were, would it give me an engine light? Surely there is a sensor monitoring the pressure? If the S/C is worn or wearing out would that give me low pressure and make it loose power with no engine light? I need to sort this out, my last bill for the air injection valve and to wipe the code and reset the engine management was £240!! Is there a work shop manual (book is better IMO) i need to get my overalls on and the jack out and start testing bits!
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