Over-rev or Redline? - Sportbike Forum: Sportbike Motorcycle Forums
 
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post #1 of 6 (permalink) Old 10-01-2007, 06:22 PM Thread Starter
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Over-rev or Redline?

I have recently learned what over-rev is... Over-rev reffer's to the rpm of a motor after it's peak torque is produced. Such as if a torque curve ends at 12 but the bike redlines at 15, anything about 12 is considered over-rev. When a engine is in over-rev there is usually a drop in torque sometimes quite a significant drop. I am wondering whether or not it is faster to shift at the redline or shift at the end of the torque curve? I have my own theory that it is best to go to the redline because you are in a lower gear even if the hp drops wich means harder acceleration. If anyone can verify this it would be nice to know.

P.S. If anyone wants to say depends on the bike I specificaly wish to know about a 2007 Kawasaki Ninja ZX6R.

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post #2 of 6 (permalink) Old 10-02-2007, 05:29 AM
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It depends on the bike, and it depends on the track, and how agressive you want to ride. Getting to within 1000 rpm of redline starts to put serious strain on your engine. So if you aint gotta, dont do it.
The main reason for the over rev is so that you dont find yourself having to shift when you are all the way leaned over, it gives you a touch more time to get out of the corner.




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post #3 of 6 (permalink) Old 10-03-2007, 11:30 AM Thread Starter
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THanks for the imput but I am wanting to know for a straight line, I understand it's purpose for cornering but I am wondering is it faster, (not neccisarily better) to shift at the torque curve even if you will be in a lower gear if you wait to shift until the redline?

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post #4 of 6 (permalink) Old 10-03-2007, 11:33 AM
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In a staight line, disregarding engine wear, you are best of shifting just a few hundred rpm past peak HP (which is not always the same as peak torque)




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post #5 of 6 (permalink) Old 10-08-2007, 11:21 AM
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If your just wanting to know what is best on a straight line such as which is fastest drag racing then it depends on where your peak power is in the rev range. Say your bike redlines as 12k and your peak power is made at 10k or 10,500 then you'd probably wanna shift just after you hit that mark. Mainly because your in a straight line and your more than likely WOT and by the time you go to let off gas and clutch in your already close to redlining and its always better to shift too soon than to hit redline since your power will drop off significantly once you hit the rev limiter and you won't be carrying as much power into the next gear

I was at the drag stip and I was waiting till right about redline to shift and a guy I was there with who runs there all the time told me to shift about 1k or 2k rpms sooner than redline cuz your moving so fast through the revs by the time you clutch in and hit the next gear your already about to redline. It helped me get a faster time by doing this.
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post #6 of 6 (permalink) Old 10-10-2007, 04:04 PM Thread Starter
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Mathamatics do come in handy.

THanks that is exactly what I was looking to hear... I did some reasearch on the internet and did a hella lot of math. Basicly it depends on gearing and peak hp as you guys have suggested but for anyone else who reads this....
Basicly for your first two shifts you want to go right to your redline. This will produce your best time if your gear ratios are the same as the average sport bike, However this is harder on your bike. Once you get past those two first gears into third and up you should be able to shift anywere from just after your peak power and up.
In otherwords simply push it hard for your first to gears and shift just after (about 1500 rpm after to be exact) your peak power for the rest. This should give you your best possible time.


In case anyone is wondering what average gear ratios are... I belive they are about.
1st:2.6
2nd:2.1
3rd:1.7
4th:1.6
5th:1.4
6th:1.3

Remember also this is only the correct time to shift if you have plenty of over rev and your peak power is well before you redline.

If anyone has anything theyd like to add let me know.

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