Vindicare Posted April 15, 2008 Share Posted April 15, 2008 Hey guys, just a few questions and a little bit of self reasoning here. Okay, I've decided I want to supercharge my engine To be different(and I like the idea of a low rpm power band). Now, I had originally purchased a M90 to undertake this with, but I've since started looking at twin screw superchargers instead. I've considered getting a whipple charger but from what i've seen they only sell as small as a 2.4L supercharger. If i were to use such a large supercharger on a 2.8, Could I underdrive it to Get a desired power output and not adversly effect power delivery? Would doing this turn the car into a "pig" to drive around as the charger is saping a larger amount of power for a certain boost level? Would doing this have a similar effect as a very large turbo used in the same instance? Any help would be cool, Thanks! Aaron Quote Link to comment Share on other sites More sharing options...
(goldfish) Posted April 16, 2008 Share Posted April 16, 2008 I'ld look more at the cfm of the units than the Liters. Off hand I think that that could be fine depending on the pulley size and boost levels you wanted. Quote Link to comment Share on other sites More sharing options...
Vindicare Posted April 16, 2008 Author Share Posted April 16, 2008 well im assuming from the tech details that it can push 1274cfm, and i assume that is at it's max speed of 16k rpm, which i wouldn't' go near. So if i were to say spin it at 1.3 crank speed, it would only spin the blower to 9100. I dont know, im just throwing numbers around Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted April 16, 2008 Share Posted April 16, 2008 Calc For Roots type of Superchargers ((Super Charger Disp X Pulley Ratio X 14.7)/ (½ Engine Displacement)) - 14.7= Boost Pressure Quote Link to comment Share on other sites More sharing options...
Vindicare Posted April 16, 2008 Author Share Posted April 16, 2008 dont happen to know what type of variables need to go in that do you? like litres, CID?... Using litres it says i will only make 21 PSI, which for such a large blower i couldn't see that being right as the blower is being pushed to 10500 rpm at redline using a 1.5 pulley ratio. Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted April 16, 2008 Share Posted April 16, 2008 I am doing a weber blow through using an Eaton M62, 1 liter disp. With a 2.5 ratio I calculate at 11.5 psi of boost. With the flow losses it will most likely be about 10 PSI or less at the carbs. Look up the efficiency of the supercharger to find out how much pressure is lost due to blow by. The intercooler and piping will also cause pressure loss. I am not looking at high RPM power 4 to 5 grand is about as high of an RPM that I plan on rapping the thing. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 17, 2008 Share Posted April 17, 2008 Beware of confusing the Roots type blower with the Lysholm Screw design of the WhippleCharger. The thermal advantages result in a much more efficient compressor. In industrial Applications, a Lysholm Screw in single-stage applications will easily run to a 4:1 Pressure Ratio and is more limited by auto-ignition point of nearby materials than the compressors' ability to compress air efficiently. I have seen lysholms pumping with discharge manifolds glowing dull red where operators lit their cigarettes off them! A Roots blower is limited in automative applications for the street to under 20 psi, usually. A Lysholm could easily run to 54psi, but at 20 psi the heat generated from a superior design and less internal recirculation will make much more power at the same boost level. They have normally six 'minipulses' per revolution, whereas the Twisted Lobe Roots would have at least three pulses where the pressure spikes and stabilizes... in either case, the superchargers are most efficient at 'optimal tip speed'---offhand I forget what it is, but overspeeding a Lysholm results in far less efficiency losses than underspeeding it. I would see if you can get an optimum tip speed number from technical support, and target your tip speed to be in that general area. Roots blowers just go to hell efficency-wise when under-speeded, resulting in a lot of HEAT. Same thing happens with their overspeed performance, because of the heat generated by the over-pressurizing pulse and the inherent blowback in their design. I digress... Quote Link to comment Share on other sites More sharing options...
Vindicare Posted April 17, 2008 Author Share Posted April 17, 2008 Does anyone know where i could find out this type of information. Regardless the 2.3l unit would produce far too much boost at max speed. However, being that it pushes more air per revolution, could I not bleed of excess pressure with a waste gate type arrangement. thus letting me have a certain pressure in the plenum but having the FLOW at all RPM's to keep away from pressure drop, and havepower available at most places in the rpm range? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.