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Old 09-12-2005, 08:18 AM
RICE RACING RICE RACING is offline
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Join Date: Oct 2003
Location: Utopia
Posts: 511
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We dynoed a Toyota supra with auto gearbox and it made following

470rwkw on 11.0:1 AFR 12 deg timing 34psi boost
470rwkw on 12.5:1 AFR 12 deg timing 34psi boost
471rwkw on 12.5:1 AFR 18 deg timing 34psi boost

We have dynoed FSAE engines and made no difference in power or torque from 10.8:1 AFR to 13.9:1 and all ratios between. Some of the gains are over stated for pure power differences, all I have experienced over the years points to this especialy if you have a racing derived ignition system that is capable of firing the air/fuel mix regardless of mixture.

What you gain in BSFC you loose in total energy mass thrown into the engine (less fuel = less power) but its net effect is quelled by increased BSFC). If your ignition system is marginal then you can make big gains with running leaner more acceptable mixtures.

If fuel efficiency is not an issue (def not for street or sprint race circuit car) as time spent on WOT and high revs is very small percentage of duty esp on street than I simply set up cars with maximum fuel cooling rate even with WI as durability is enhanced, any marginal gains in power "and they are very marginal" running leaner mixtures are not worth the hassel unless your fuel system capacity is stretch (not enough injector) or as stated before you need "racing fuel efficiency gains for longer time on track to increase pit window etc.

I generaly use 10.8:1 to 11.8:1 in all applictions running pump 98 octane and up to 36psi boost pressure on 8.5 to 9.0 compression.
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