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beepbeep beepbeep is offline
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Join Date: Jun 2001
Location: Sweden
Posts: 5,564
Hello. I'll try to help you. What you have in front of you is compressor efficiency map. It's farely useful as it indicates how much air supercharger can flow w/o being inefficient. Then it's a matter of calculating how much air your engine will swallow at certain boost/RPM and plotting it into the map.

Typical 300hp ROW 3.3 engine running stock boost will gulp around 0.26kg of air per second at pressure ratio 1.7.

Your graph is in m^3 but we can assume that 1 m^3 of air weights 1.29kg at zero deg. C and 1 bar athmospheric pressure. It means that 0.26kg air is .26/1.29=0.201 m^3. Muliply it with 60 sec and you get 12.1 m^3 per min.

If we assume same VE for 3.6L engine and decide to take out 411hp at 6000 RPM and 0.9 bar, it crunches down to roughly 0.35kg/sec and 16.28 m^3 air per min.

I plotted red dot in the graph for 300hp and green dot for 411hp.

3.3L, 300hp @ 5500 RPM
17kW (23hp) to drive the blower
65% supercharger efficiency
93 deg. C discharge temperature
roughly 8000 RPM blower revs (numbers are missing in graph, i assumed this by counting the lines)
345cc injectors are needed assuming 80% duty cycle
total fuel flow 100L/h at target fuel pressure (presumably 3 bar+boost).

3.6L, 411hp @ 6000 RPM
27kw (37hp) to drive the blower
64% supercharger efficiency
110 deg. C discharge temperature
roughly 11000 RPM blower revs (numbers are missing in graph -||- )
460cc injectors are needed assuming 80% duty cycle
total fuel flow 133L/h at target fuel pressure (presumably 3 bar+boost)

These numbers are calculated by using apprximated VE for stock 930 engine. YMMV.

So your supercharger is good for roughly 500hp but if you use it in normal fashion (300-400hp, 0.7-0.9 bar) it will be dead center on it's efficiency map and use between 25 to 40hp of power (to be substracted from engine).

So now it's just a matter of using the pulley that gives you boost you choose.

I used VE that is comparable to 3.3 930. Yours might be little higher, due to bigger ports etc.

When it comes to WBO2 equipment, I recomend Innovative LM1 and LMA-3 (AuxBox). Just buying a box that logs AFR's only won't help you much. You need something that will log AFR, RPM and MAP to begin with. LMA-3 can do this. Reasonable compression ratio to use with 0.7-0.9 bar of boost would be around 7.5:1 to 8.5:1, depending on fuel used and ignition curve.

P.S. Good turbocharger will have best case efficiency of 70-75% in best case and will rob less power from the engine. Now you understand why we don't see that many superchargers in OEM cars But if supercharger is what you want, Lysholm is probably the best supercharger around!
Thank you for your time,

Last edited by beepbeep; 03-11-2008 at 12:07 PM..
Old 03-11-2008, 11:46 AM
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