As the IS-F debut draws closer Lexus has wisely chosen to keep the actual horsepower of the high performance motor a well kept secret, mentioning only a figure somewhere in excess of 400 hp.
A few months ago Car and Driver reported that the 5L V8 had made as much as 483 hp in an (at the time) IS 500 mule. In April Road & Track also ran an article about future Japanese sports cars, where it said that Toyota was developing a new Supra and Lexus IS 500. Both would be powered by the same 5 liter V-8 putting out 450 hp and 383 lb-ft of torque in the Supra and detuned slightly for the IS 500 (IS-F). So many sources seem to indicate that Lexus may lead both the RS4 and the M3 and slightly trail the Mercedes-Benz C63 AMG in overall horsepower.
With this taken into consideration, Lexus also repeatedly says the car will have more than 350 lb-ft. Given that the 4.6L motor produces 367 lb-ft, it stands to reason an out and out performance motor could have substantially more hp/liter than the 4.6L motor and a slightly less torque peak that a higher horsepower peak would imply.
Now if Lexus only gets the same 82.6 hp/liter from the 5L motor that it has wrung from the LS 460's 4.6L V8, the car would then produce around 413 hp. But this seems a bit overly conservative since the RS4 and new V8 M3 are both producing similar power with less displacement. Reason would dictate that Lexus should have a similar hp/liter ratio if the engine can maintain a similar redline.
So what is the $64,000 question? How much power will the new IS-F actually have when it comes to market? Give us your answer below, and of curse feel free to comment as well.