Evening guys, I'm about to start a big turbo build, got a room ful of goodies I've currently got a brand new efr 6258, but already decided its to small and want to buy a bigger one and sell that on. I bought the 6258 without doing any maths, this time i want to do it properly.................so! I hear lots about boost pressure, what figure should i be aiming for 15 psi or 30 psi. I'd like to achieve about 500, but not have the turbo running its nuts off. It needs to be street usuable, also got a wet NOS kit ( thatll be purely 1/4 mile useage) and a meth kit. The ecu is an emerald k6 with 3 switchable maps, use just use map 1 for street, map 2 for clever gits and map 3 for the strip, so thinking i could keep a large turbo under control. also got quaiffe lsd clutchmasters fx400 6 puck clutch ie rods supertech inconel valves arp flywheel bolts arp head stud kit arp pinion ring bolts emerald k6 homemade tubular exhaust mani homemade inlet mani with vr6 throttle body seimens deka 750 injectors bosch 044 pump pinion brace homemade
As a rough guess i think you need about 1450kg/h of air to acheive your 500bhp. I assume this is a 1.8t? To make a 1.8t flow that amount of air you will need to be around 34 psi or 2.5 bar - gauge. Thats making the power at 7500rpm.... A good book if you want to do all the maths yourself is (Heywood - Internal Combustion Engine Fundamentals) But a quick google found this spreadsheet will help you along the right lines in terms of the calcs you need to make for basic numbers. Its in american units but thats helpful as the EFR compressor maps are in lb/min also... http://www.bescaredracing.com/sti/turbo/TurboSelectionWorksheet.xls However the size of turbo you will need to flow enough air for 500hp is probably EFR7064 sized. I guess whether thats big enough for you or not depends how "street usable" you want the car to be.
As said above, it is about air flow to get your power Pressure is a function of resistance, Higher flowing heads, bigger cams, inlet and ESPECIALLY the exhaust manifold will make a huge difference I would look at the graph, I don't know the BW range but if it is rated at (say 400hp), you could easily have it in the 450 range in the graph, just down on compressor efficiency , as long as youu keep it away from surge Also remmeber a quick spooling well balanced 450hp car will be faster than an old school laggy narrow band 500hp car pretty much evey where you drive it
