DRE1615

I think you hit a point of diminishing returns in horsepower. You get to a certain point where you need to have a huge jump in hp or a huge drop in weight. But I think stock for stock there is a big difference in times. Kind of how the 335i and M3 are so close in times even with such a hp difference. It boggles me too.

SilverBull

How do you get "heat soak" without a turbo? I thought that only referred to FI cars. This car doesn't seem to be a real 1/4 mile friendly car. More of a open road track car maybe.

ToothDoc

It's not really 1/4 mile friendly - the suspension isn't compliant enough. If we put some real soft springs in the back, we'll have more weight transfer and we'll see an improvement in the launches (60'). That alone could be worth 2/10ths or more. That's why some of the modded 335 guys are doing low 12s while still only trapping 110-112. Softer suspension - FWIW, I have ridden in a modded 335 that was lowered and had aftermarket suspension - but it still was SOFTER than the IS-F.

I noticed "heatsoak" also. I only did 3 runs in one day but didn't do anything to keep the engine cool. I went 110, 109 and then 108 mph. Slower and slower as it got hotter and hotter.

nuttybar08

Hi all...this is my first post and I thought I'd chime in about the "heat soak" issue. LS2 GTO drivers see this problem frequently and it's directly related to the IAT (Intake Air Temperature) sensor location. The sensor gets too much feedback from engine heat (vice strictly reading the temperature of air entering the intake) and that in turn pulls timing even when ambient temperature isn't really hot enough to warrant it. *POOF* there goes your power, and it is really pronounced on those cars, enough so that the IAT sensor relocation mod is pretty popular.

I assume that the high compression Lexus V8 has a similar sensor although it may be called something else. It might be worth the time to check its location to see if it's vulnerable to "heat soak" and if that in turn is retarding timing. It would certainly explain the OP's problem and why the car posted a better time after resting. Also the LS2 problem was readily apparent with the butt dyno...the cars noticeably lost power when high IAT's were sensed. Is anybody else experiencing this?

Anyway, I'm really interested in the IS-F and hope to test drive one soon. The wife is on board.

Nad1370

The IAT is part of the MAF sensor, which I think is located on the air filter box or intake plumming.
Also Coolant temps affect power as well. IF you have high IAT's and CTemps, you'll be running lower ignition timing ramps. Therefore lower HP.

I often do logs when I drag my Evo8. I found out sitting there idling while waiting for your turn will increase IAT's significantly which lowered my timing ramps by 2-3 degrees. No knock just set on a lower timing scale.

Although my best trap speed is always acheived while hot lapping. I'm guessing airflow through the iat on the turn around will keep the temps near ambient instead of baking under that hot hood.
I can see cooling off for 45-1 hr can also give you great results as you've shown DRE.