I was just wondering about peak power and torque numbers, lets say your car's peak power is at 5K and torque at 6K, redline is 7K, isnt passing the peak points going to be a disadvantage since they both start to fall, yea you can shift at lets say 62K revs and youll be making the gear ratios shorter, just something that came to mind and if anyones played around with numbers to see if its any quicker or not

 

are you just talking about shorter gearing in general? if so, theyre plenty of people with s2000's with 4.57 or 4.77 gears

 

nah talkin bout shifting points, i mean once youve come to the peak power of the gear, why keep going all the way down to redline, maybe 200 revs or so later, just shift to the next gear

 

Usually peak power is higher in the rev range since power is TQ x RPMs so even if TQ is falling with higher revs you are doing more revs to get more power.

I think the idea is hard to understand but yes the power will fall at higher revs (past peak power) you do want to shift but the later you shift that mean the higher youre engine will be in the nect higher gear.

I think idealy you want when you shift to the next gear to be at a good point in the TQ (near peak).

Just a made-up example.

Lets say peak TQ is 4000 rpm and peak power in 5000 rpm and redline is at 6000 rpm.

If you shift at 5000 and it puts you back at 3000 rpm you may not accelerate as well as shifting at 6000 but getting back in the next gear at 4000 (instead of 3000).

I lot can be done with gears to imporve acceleration and not a lot of people appreciate gear ratio like they understand HP and TQ but don't understand the whole picture.

 

Because you will be out of the powerband for the next gear. This is the theoretical idea/advantage of CVTs, they constantly keep the car in the powerband with infinite ratios...

 

yea guys, it does make sense that for the next gear you wont be in the powerband

 

yeah, if peak torque is 6k, peak power would have to be at least that high. 5k peak power doesn't make a lot of sense. You have to gauge the where you fall in the power band of the next gear. All cars will be a little different.

 

To be higher in the rev range for the next gear. Although the power would be "dropping off", you'll usually land at the rpm suited to keep you in the fatter parts of the powerband for that next gear.

 

Well, if you shift at 62K's your engine is gonna blow up.... =P

 

Most of you are looking at it the wrong way.

Let's say your 1st gear is a 4:1 and 2nd gear is 3.5:1, the car redlines at 7000 rpm but makes max power and consistent torque at 6000 rpm (and drops off torque thereafter).

If you multiply the 1st gear ratio by 85-90% of the peak torque, it will invariably be more than the 2nd gear ratio multiplied by 100% of the peak torque.

Ergo, you have less "apparent" torque at the wheels, which means the car will accelerate more slowly.

There are some cars where short shifting (which is what this is called) makes sense, but generally most cars benefit from being wrung out all the way to redline.

Of secondary importance, the higher you rev in one gear, the less "fall off" you'll get in the next gear, meaning you'll be at a higher power/torque peak as you shift to a higher gear.