Cut-Off to Prevent Over Rev???

[theeaman]

i have heard mention that some performance motors have a safety cut-off that prevents the driver from over reving the motor.

does the nsx have this feature? i not interested in testing this on my own and hope someone more knowledgeable than myself has the answer.

aman

 

[Lud]

Yes, the NSX ECU has a rev limiter.

Like all electronic rev limiters, it can only stop you from over-revving with the throttle. If you downshift into too low a gear for your speed, you will still over-rev.

It doesn't hurt anything to hit the rev limiter with the throttle. In fact you should probably try it sometime just so you know what it feels like, so you won't freak out if you ever hit it unexpectedly.

Note that some aftermarket chips raise or eliminate the rev limiter. I would not recommend going over the stock rev limiter on a stock engine.

[This message has been edited by Lud (edited 16 January 2003).]

 

[nsxtasy]

The redline for all manual transmission NSXs is 8000 RPM and I believe the rev limiter kicks in somewhere between 8200 and 8300 indicated on the tachometer.

 

[dgaetano]

If the engine is cold the limit will be lowered. It doesn't raise to 8000ish rpm until your engine temp is reading normal. I think it starts somewhere in the middle 6000 rpm range with a cold engine. This is how the two 96's I've owned work anyway.

-Daniele
1996 NSX-T (red/black)
1997 Honda CBR 1100XX

 

[nsxtasy]

Originally posted by dgaetano:
If the engine is cold the limit will be lowered.

Oh goodie, now I get to use the favorite phrase of the incompetent mechanic:

"They all do that."

 

[Vytas]

Woodwork at Honda mentioned to me that while testing the NSX, they ran the car at redline constantly bumping the rev limiter for a few miles. It does what it's supposed to and very well to protect the engine.

 

[dgaetano]

Originally posted by nsxtasy:
"They all do that."

Damn you man. OK, more specifically: if the engine is cold the ECU will lower the throttle cut off, just like it raises the idle. Once the engine has warmed up enough (in the eyes of the ECU) for the idle to return to normal, the throttle cut off will be set to red line.

Note that this can be a problem. For example, you're leaving work and you end up at a red light with a corvette that needs schooling. In the rush of the moment you forget that the effective redline of your cold engine is about 7K so you trip the throttle cut off. Bad for the ego, and perhaps not so good for the car. No, I'm not speaking from experience, and this did not happen to me last Tuesday.

-Daniele

(Who does not actually condone racing Vettes. They don't get that many days a year where their car is not in the shop, so be a sport and let them have their fun)

 

[Lud]

It's not particularly good to rag out your car before it has warmed up.

 

[nsxtasy]

Originally posted by dgaetano:
In the rush of the moment you forget that the effective redline of your cold engine is about 7K so you trip the throttle cut off. Bad for the ego, and perhaps not so good for the car.

It's not that it's bad for the car to hit the 7K rev limiter when it's cold. It's bad for the car to be flooring the throttle before it has a chance to warm up, and it would be worse for the car to reach the 8000 RPM redline when it's cold. That's exactly why they make the redline lower until it has a chance to warm up.

If you feel the need to mash the go pedal, wait until the car is warmed up before doing so. This is generally good advice for any car, not just the NSX.

 

[Tony Montoya]

I think I hit the rev limiter in 2nd gear with the automatic transmision. I forgot I was shifting manually and I wondered for a second or two why the car wasn't changing gears.