No incorrect.
The adiabatic efficiency of the 2.4L shown in this graph is over 90%. It's the scale on the left.
I put that up for the general info. I'm actually using a 2.8L compressor. The 2.4 was too small and one of the biggest reasons I never released the kit. Wait until later tonight and I'll put up more info. I just had to stop and look to see if any other engineering types looked at the graph.
I'll make one comment about stress on the engine for now, the Viper motor is not built to handle upper RPM's. When has anyone heard of a Viper engine failing at WOT and 4,000 RPM? I never have. Anything I ever hear of is over 5,000 RPM, but more on that later tonight.
Regards,
Sean
Sorry Sean but you are incorrect. I was talking about adiabatic efficiency (the thermal efficiency of converting rotating energy into pressure energy) . The red line. Not volumetric efficiency. Volumetric efficiency is where centrifugal chargers really fail, thus the resulting non linearity of the flow curve. 78-80% adiabatic efficiency is generally regarded as the peak efficiency of the twin screw charger. 90% would get you a Nobel prize. Yours is showing a peak of about 65% which seems a bit low. Maybe the test pressure is outside of the optimal characteristics for that particiluar device. I would prefer to see a 3-dimensional map of efficiency versus flow and pressure and determine the correct size based on the best thermal efficiency. Especially if an intercooler is not included and the inefficiency results in increased inlet temperatures.
I could tell it was not a workable solution - too little flow for the consuming engine. It would probably work well for a 7 liter though.
As far as the stress and engine life. Please do not mix up combustion, valvetrain dynamics and stress. Stress is the translation of force into mechanical elements. The factors that cause things to fatigue. RPM only increases the frequency for the compression side of it. RPM does increse the inertial side of the equation (tensile direction), which does indeed increse the component stress as it is the delta from max to min that causes fatigue (note the S in an S-N curve is not the peak stress but the stress range from minimum to maximum). And in this case the minimum would be a negative value when, say for example, the rod is in tension, and positive when in compression. And yes, the tension forces may exceed the compression forces. That is why missed shifts resulting in very high revs fail the conn rods. In tension if you analyze the fracture.
As far as the rest of the driveline the primary component of fatigue failure is indeed torque. Added rpm, or horsepower, is a significant factor for differential bearing failure but not much else. Compare a 200 hp Honda with a 200 hp anything else and you will see the difference. Torque is the twisting force that the mechanical bits must handle. I will avoid the reflected inertia side of the equation which also leads to driveline failure as it does not pertain much to this audience.
I will leave the valvetrain comment aside. I studied valvetrains in college and had valvetrain engineering responsiblity for about a decade. Including several published documents on the topic of valvetrain dynamics. We could have a very interesting conversation if you wish to go that direction.
. If you install the Roe kit and decide you don't want it I'm certain someone here will gladly take it off your hands. Not to mention that Sean will be with you every step of the way. Go for it.
Hey, when are you gonna be up so we can terrorize these Vettes and Ferrari's and Porsches around here??
