RE: Supercharger bypass valve operation patprimmer (Publican) 23 Dec 08 09:08 Maybe the OP will chime in with some more details of the project so we can specify what would actually be required. The Mercedes bypass on this particular model is electrically operated though, functionality that might as well be used. Although if the point of the system on the OP's project was complete driveability at the expense of some outright performance then it may be a viable approach. Some of the G-lader positive pressure is 'wasted' in pusuit of smooth transition, more than would be seen using an electronically controlled bypass. The VW G-lader system gives good tip-in as the pressure is fed in smoothly, but using electronic controls can give alot more accurate control over the air path. The GM blower has neither clutch or bypass. If you only wish to defend your original unhelpful snappy attitude by backtracking then what you post does not assist the persons original question, does it? RE: Supercharger bypass valve operation izzmus (Automotive) 22 Dec 08 19:39Ĭome on Pat, the original question has some interest and valid discussion. 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. 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.
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