Lextasy89

The ISF and M3 are running very similar times.. even with the ISF having an extra 76 ft-lbs of torque.. i think the reason for this would be the axel rations:
2008 BMW- 3.85
2008 Lexus ISF- 2.94

I think if a 3.85 gear was made for the ISF that it would be alot quicker in the 1/4 mile than the M3.. just a thought...

RX Renesis

yes having a higher axle ratio will have better acceleration, BUT having a higher axle ratio means the isf will be cruising at a higher RPM given the same speed which means using more fuel... also the higher axle ratio will mean lower top speed for better acceleration...

i dont think lexus put in 8 gears just for the fun of it... the 8 gears are there for better acceleration and also lower rpm at cruising speeds....

Lextasy89

yea im just saying that for those people really into 1/4 mile times.. you could really lower the times by matching the M3 axel ratio.. and you would be faster in it in the 1/4 mile and keep the lead after..

ToothDoc

Yeah, but each individual gear is much shorter to offset the taller diff ratio. If you actually look at OVERALL gearing, the M3s first 6 speeds match the IS-F's first 6 gears VERY closely. The 7th and 8th are just overdrive gears for fuel efficiency which would never be used in a race track.

IS350jet

Correct, with 8 speeds the ISF doesn't need a 3.85 ratio. If it did, the gas mileage would be horrendous.

kt22cliff

I haven't driven IS-F so I don't know for sure what speed equates to max RPM in each gear but you would NEVER use 1:1 6th gear in any tracks regardless and the 5th gear is mostly likely unnecessary as well except maybe the longest of the longest striaghtaways. For comparison, E46 M3 which has 1:1 5th gear and the 6th gear overdrive and those two gears are not touched.

Mr.NA_T

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