Post by
martins_240sx »
https://forums.nicoclub.com/martins-240sx-u49295.html
Mon Feb 22, 2010 7:58 am
okay to answer your question mrgreeneyes about the blockage...yes i know its late but i have been searching and calling so many people and here is my results. from the start all of my research has come from the 8v92 detroit deisel that i work on that is twincharged in exactly the same setup as i am running. but due to more knowledge in this situation many of these "2 stroke" engines twincharge due to the facts that they cannot suck in enough air in naturally so there are slight differences in my final results....lots and lots of math... so from there i got a hold of my buddy from steve wills racing who runs federal mogul and got contact info to another guy who inturn "schooled the hell out of me" in the world of twincharging. He told me that you can due a bunch of math and spend hours to find out your end goal of boost only to find out when you bolt it together that you are no where close to what you thought. he said there are so many variables that it is pretty much a trial and error situation. but the one thing he couldnt stress enough was... the supercharger will never ever never be a restriction to the turbo...I will explain later... but the turbo will always be the restriction culprit. Explanation, The supercharger rotates and takes a certain amount of air in with every rotation through its lobes, nothing can stop this action from happening. by adding a turbo all you are doing is cramping the air into those lobes even further. so instead of every rotation supplying atleast 14.7pounds(barometric pressure), it will supply that and whatever you add to that. Now where the restriction comes from in the turbo is at the exhaust turbine, in the form of backpressure. if the exhaust cannot escape then it will become backed up and give the illusion that the SC is becoming a restriction. by simply increasing the size of the turbo you can continue to force feed the SC. But with this being said, when you compress air you will get heat and lots of it, so the real trick in this setup is going to be combating the air intake temperature to keep the volumetric efficiency of the supercharger up. Water meth injection! simple fix. he also said on his drag car he monitors boost from 3 places1. turbo 2. after supercharger (actual boost pressure)3. Turbo exhaust (measures the back pressure)
by running a length of tube away from the exhaust with a boost gauge hooked to it you can measure how fast the boost in the exhaust raises in comparison to the actual TURBO boost pressure. if it raises higher and faster than the turbo then you have just discovered a blockage at your turbo and need to increase turbo size to match your goals...
He also stated that if im going for a steady boost pressure say my 20psi then all i have to do is hook my wastegate up to the intake actual boost pressure and wont have to worry about my turbo over boosting. Instant power. this is nice since my turbo could boost anywhere from 7-12 psi depending on rpms and volumetric efficiencies of the SC to get me to 20 psi. even those numbers might be to high for the turbo... but like he said i should monitor in those 3 places and thats what im goin to do...especially since he is old as dirt and is now rich as s*** and laughs at cars that can only run 10s 9s 8s 7s...crazy fast stuff. he might know a little. hope this helps...if there is any more questions ill try to answer them to the best i can.
