Quote:
If the SIR does what it's said to be able to do, then I think the idea is a modern solution to an issue that will confront IT from now on as more modern and powerful cars become candidates for IT. However, the E36 situation needs some tweaking. At the moment we have:
RX7 target HP = 181 rwhp
181 rwhp * 14.8 lb/hp = 2680 lb race weight
BMW with 27mm SIR target hp = 220 hp crank = 180 rwhp assuming 18% driveline loss
180 rwhp * 14.8 lb/hp = 2665 lb race weight
So, the E36 should drop from 2850 to 2665 with the restrictor, or to keep it at the current weight a less restrictive SIR should be spec'd to give it 193 rwhp. 193 rwhp * 14.8 lb/hr = 2850 lb.
Adders and subtractors: They cancel out
BMW has bigger brakes and more torque than RX-7. RX-7 has lower CG and better aero, so it's a wash.
Fred
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Never seen a wash with 200+ ft/lb torque across 3000 to 4000 rpm spread against 130-134 ft/lb and very short span. With your numbers the RX7 must make 222-225 crank HP---lots of luck. If the bimmer has that driveline loss you need to do some homework.