View Full Version : rev-limiter

10-14-2003, 01:58 AM
I was wondering if it is possible to over-rev a motor, even if it has 7000rpm fuel cut off. I know if a motor is over-reved, it can spin a bearing or throw a rod. I have a 99 cobra with a 7000rpm fuel cut-off. I did something stupid the other day, I was driving at about 3000rpm in 4th gear with 4:10 gears and I shifted into 3rd, the motor immediately climbed to 6000rpm and then I immediately shifted back into 4th, being afraid I would over-rev and spin a bearing. Is it possible the sudden jump in rpm's could of damaged the motor even though I didn't hit 7000rpm. I drove the car hard after that and it runs perfect. Also, should the oil pressure gauge be right in the middle or towards the high end a little, it's usually towards the high end a little, fluctuating back and forth between the middle. I use Redline 5w-30 synthetic, the best in the bussiness. Later:eek:

10-14-2003, 07:22 AM
I had a MSD DIS4 installed and set it up at 6700rpms so i could avoid over revs such as that and eliminate (i hope) detonation.

10-14-2003, 08:43 AM
Yes you can over-rev the engine and cause damage by downshifting from say 90mph into 2nd gear or something like that. If you downshift and are below the revlimit then no, you won't cause any damage. That what downshifting is for....so you can hit your power band and GO!!

Pulling to redline you'll hit the fuel cutoff which prevents the engine from spinning faster than it should. Downshifting into too low a gear at two fast MPH will overspin the motor because the tranny will whip the engine up to speed beyond what you could do by using the gas pedal.

10-14-2003, 02:53 PM
Oh, and you didn't hurt your engine at all if you did what you said you did. My cobra has gone as high as 7800 rpms before. :eek: It's fine. :) Momentum will carry your engine to a higher rpm than your rev limiter. If you have your car in neutral, and slowly bring up the revs to 7000, then try to give it more gas, it won't go any higher, but if you just floor it right away, the rapid increase in rpms will bring your rpms well above 7000. In my 7800 case, I was beating on my car and at the top end of second gear (5900-6000) I broke traction and the tach climbed really really high. Can't ignore the 5 inch monster tach in your face. Definatly over 7500 rpms. Almost 8000. Car did buck pretty good on the rev limiter (i have ignition rev limit as well as fuel). Engine held up as advertised.