You're thinking of a Roots blower. The Roe PD does spin according to the crankshaft, same as the Paxton, but the Power Valve releases the extra air back into the non-pressurized side of the intake making the blower "idle" and allowing vacuum to the intake runners. The screws spin, but don't actually make any boost or use any hp to turn until boost is built.
Ted
Yup. the old by pass valve. Should have remembered that...but If the pulley is turning the screws, it would seem to be using HP? ...just like any of the other pulleys driving things on the engine. They all take some HP.
500 ft lbs of torque at 1800 RPM means a bigger explosion in the cylinders at 1800 RPM. A bigger explosion means more stress on the components. If you look at the boost curves above, you will see that there is, therefore, far less stress on a Paxtonized engine. With that said, the Vipers before 2000 had forged pistons and were/ are very strong engines. 2000 to 2002 things got weaker with cast pistons. The Gen III and Gen IV engines are not as strong as the pre 2000 Gen II engines. If someone disagrees, please jump in.
I guess the real proof is in how long things last. I'll let my cast piston miles and experience speak for me. There are very few reading here that have a driven a Viper as many miles as we have. About 83,000 to date. Lots of hard miles on the 00 car.
I agree.
Larry Macedo put 9-1 Ross pistons in my engine back in 2003. I recommend all cream puffs get a piston change for sc and Nitrous just for longevity and reliability.
Ted
5 Pound Roes absolutely do not need forged pistons to run just fine. Again, my miles speak for themselves. I am completely satisified with my 'little' set up. I have no desire to go further as drivability is the deciding factor for anything we do to the cars. I could jump in our 80,000 mile car today and drive across the country. We'll be in the 100,000
driven Viper mile club next year. Few can say that.
Really? Here's a copy/paste from
Roe Racing Performance Parts
What kind of maintenance does the Supercharger add?
Next to none. The oil in the unit does not come from the engine oiling system, which gets contaminated from blowby and the combustion process. Therefore, the compressor oil stays cleaner and in better condition longer. We suggest the case oil level be checked at each engine oil change. The oil color will be the first indication that a change is due, which should be at approximately 50,000 miles.
Ted
I changed the oil this spring for the first time at 2 years/21,000 miles. It was still very clean, but a little low. I would have had to add an ounce or so. It was between the marks. I never had to add oil over the 2 year period.
The problem is....you would need the IAT sensor after the s/c on the Roe. I had an Autometer on mine in the intake. It would drop about 50 degrees in a third gear pull with the w/m. The longer you were on the throttle the more it would drop.
Exactly right about the IAT location. Engineers have told me that the actual intake charge temp is not linear to the pre SC temp. That being said, I have dialed in the VEC IAT function to where I have one card which is good from 30F to 100F. Like the stock pcm, I let the mixture go rich for cooling after 126F IAT (I set that number). I have yet to see that temp on my Vipair 2000 car -- no matter the outside temp. The non - Vipair car has seen 140F on similar days. I have made over 200 log runs since 5/06. Upgrading to VEC 3 capabilities (IAT function) last year was kind of like starting over. There was a definite learning curve getting the parameters in line with each other.
Although not linear, I consider the post sc air charge temp to be a relative number to the airbox IAT when using the WB readings as the end result to set the IAT function parameters. It's not perfect, but my AFR tuning has shown it to work quite well enough for me.
Steve
