I cant see my self driving a car that builds its max HP at 6,000 wonder why the new STi has a 9k rpm tack (marketing?)...if its not going to be usefull over 6k? Definatly a sweet car but only time will tell if the USDM STi will have the STi fun factor...


areg

 

Huh... I think the JDM STi makes 280hp @ 6000rpm as well but most likely the HP rating will be higher than that... maybe

300hp @ 7500rpm?

look here http://www.subaru.co.jp/impreza/sedan/09/09_02.html

And now, I am going to show you that 300hp@6000rpm and 7500rpm are both just as good.Let's build a simple model to compare

them.

Assuming that we have 2 cars, one JDM spec which we assume that it makes 300hp @ 7500rpm, then we have the USDM spec makes

300hp @ 6000rpm.

We assume that both cars will reach the same speed at their peak HP rpm in every gear. which is 6000rpm/7500rpm for the

USDM/JDM respectively. That is when in 1st gear at peak HP rpm, both cars will be traveling at 60km/h. 100km for 2nd and 150

for 3rd.

one more condition is the tire size, which I will use 225/45/17 for my calculation. The tire circumference is about 199.27

cm, which I round it to 2 meters. Still with me so far?

Now we will calculate the torque that the each engine makes at their peak HP rpm.

HP = TQ /5252 * rpm

USDM 300hp@6000rpm = 262.61lb.ft@6000rpm

JDM 300hp@7500rpm = 210.08lb.ft@7500rpm


Then we will calculate the torque that's applied to the driving axle at peak HP at every gear.

In 1st gear

USDM 300hp@6000rpm doing 60Km/h overall gear ratio will be 12:1 TQ @ axle is 262.61 x 12 = 3151 lb/ft

JDM 300hp@7500rpm doing 60Km/h overall gear ratio will be 15:1 TQ @ axle is 210.08 x 15 = 3151 lb/ft


In 2nd gear

USDM 300hp@6000rpm doing 100Km/h overall gear ratio will be 7.2:1 TQ @ axle is 262.61 x 7.2 = 1890.8 lb/ft

JDM 300hp@7500rpm doing 100Km/h overall gear ratio will be 9.0:1 TQ @ axle is 210.08 x 9.0 = 1890.8 lb/ft


In 3rd gear

USDM 300hp@6000rpm doing 150Km/h overall gear ratio will be 4.8:1 TQ @ axle is 262.61 x 4.8 = 1260 lb/ft

JDM 300hp@7500rpm doing 150Km/h overall gear ratio will be 6:1 TQ @ axle is 210.08 x 6 = 1260 lb/ft


Conclusion: The engine makes peak power at a higher rpm will be able to use a shorter gear ratio, but it is also making less

torque at peak power rpm, so the shorter gear ratio just compensates for that. Now how a car will perform still depends on

the overall curve of power distribution with respect to a given rpm and lots other factors.

Of course, watching the rev building up is exciting, and high rev engine sound different, too. But performance wise you ain't

gonna suffer.

It's just like the Z06 engine VS the Ferrari 360 engine. The 360 sounds way better IMHO, but I think the Z06 got more torque

at the low end, so if you screw up and your rpm drops to below 3K on vette & 4k with the 360, perhaps the Vette will got more power at the lower end. Of course it depends on a lot of factors, but just trying to give you some ideas.

Hope this helps