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NathanUK NathanUK is offline
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Join Date: Nov 2006
Location: UK
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Originally Posted by beepbeep View Post
As I said before, EFI or not EFI, it doesn't matter. It's a matter of mass flow and pressure delta. You can calculate this.

A 3.3L spinning @ 6000 revs and boosting 1.2 bar @ 92% VE and intake temp of 35 deg. C would suck roughly 50lbs/min worth of air and produce around 450hp worth of power assuming certain efficiency (which I assumed from expirience). CIS flapper is nothing else but a "second throttle"...if CIS car produces 450hp it will gulp certain amount of air. If CIS makes it slightly less effective when producing that amount of power, it will need >even more< air+fuel.

Roughly, you take this figure (50lbs/min, 2.2 pressure ratio) and plot it into compressor map. If you are way out of efficiency island, your turbo isn't suitable.

That being said, GT35R 68mm, 56 trim is pretty spot-on for this case, landing in 72% efficiency island,to the right of the middle 79% best-case spot . GT40R is nice too, but suitable only if you are chasing really high power...which brings you back to certain other things (like, will engine handle it).

Here's K27 map (you need to convert kg/s to lbs/min):

Here's GT35R map (red line drawn by me for 1.7 bar application):

Calculate suitable mass flow and pressure ratio, choose A/R that suits your engine, lay out the maps and pick the turbo that suits you best according to your needs the best.

PM me your adress and I'll send you Excel spreadsheet to calculate mass flow if you cannot do it yourself.

I found this on the web Is it fairly accurate?
1 KG/sec = 132 lbs/min approx equals 1771.812 CFM

Also, is that K27 map for the 7200?

Thanks Goran.
1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.
Old 08-11-2007, 03:27 AM
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