MikeR90S

I hit the rev limiter in my '74 911S (CIS injection) all the time, engine spins up very fast in 1st and 2nd gear... it uses a centifugal weight on the distributor rotor that breaks the conductive path at 6500 rpm. When you hit it, it makes the engine stutter, but it will stay at a constant 6500 rpm while stuttering. Pretty benign and great for when you don't want to upshift right before a braking zone. Early mechanical injection 911S had the same system but with a higher (7500 rpm?) cutout.

That said, I've hit the rev limiter on my '06 S2000 once. Scared the crap out of me so I took my foot off the gas, it was like the motor just shut off. So much for advanced electronics.

WhiteS2k

As I said before, I don't see any practical workable solution other than to bounce. Let's say there is a 1000 RPM "gap" between the cut-off and restart, so when the engine hits 9200 fuel is cut off, and the RPM slowly drops down without fuel until it hits 8200 and the fuel is turned back on. Now as long as the driver's foot is on the gas, it will rise up to 9200 RPM in no time at all and the fuel is cut off again. The cycle will repeat as long as the driver keeps the foot on the gas. I don't see how any "learning" ECU can prevent this bouncing without introducing unsafe conditions (obviously one possible mode is to completely shut down the engine after bouncing off the rev-limiter a few times, but that would be extremely unsafe).

SpitfireS

WhiteS2k Posted on Jul 11 2006, 10:29 PM
Point taken

I was thinking about the F1 speed/rev limiter.
They drive in the pit lane @ a fixed speed / revs in a (I think) predetermined gear.
It all depends on how fast this bouncing back and forth takes place I guess.

My personal experiences with the rev limiter are that you "hit a brick wall".
Even when it kinda caught me by surprice (little time to get of the throttle).
With a ON/OFF limiter one may expect some bouncing to occur in such a situation?

The F1 cars seem to "not go any faster and/or stop increasing revs".
Thats what I call Sophisticated Behaviour

Latest news is that Microsoft is going to make F1 ECU's in 2008.
So when they hit a rev limiter they get a BSOD.

WhiteS2k

That is certainly another option. But think about this: You are trying to pass a slow moving big rig, you see a gap in the opposing traffic and pulled out, but in your excitement, you pressed down on the gas a little too hard and it hit the rev-limiter. The "smart" ECU then limits your rev (or your speed) to a lower max. There you are, crawling along trying to pass while the opposing traffic is heading for you. What now? I can just see the law-suits waiting to be filed.

circa86

F1 cars also have a rev limiter i am sure, a speed limiter is alot different from a rev limiter, a speed limiter, also know as bloody cruise control (for the love of god!)

I guarantee you F1 cars have a rev limiter somewhat similar to the S2000's, which btw is exactly like every electronically controlled fuel injection car ever.

are you saying it would be better if when you got to the fuel cut it just held the engine at that RPM???? are you kidding me??

the rev limiter "bounces" because your ECU assumes you aren't a complete idiot and that you will take your foot off the gas and shift up, if you are willing to do an experiment haha. ...

just put your car in nuetral and floor it until your engine stops running.

a rev limiter isn't for your conveinience, it is for your engines convenience. please drive all of your friends manual cars and bounce off the rev limiter repeatedley, they will give you the answer to your question in fist or foot form.

this thread is absolutely stupid btw

Planets

Not all cars bounce. I have driven cars that when you hit redline, it's like hitting a brick wall, ala the s2k's cold 5k limiter.

SpitfireS

WhiteS2k Posted on Jul 12 2006, 03:06 AM
How about shifting to a higher gear?
A smart ECU would detect you shifing wouldn't it?
It would reset the lower max it used for a second or so and off you go.

Anyway...
Maybe we should stop talking about this.
It seems like we upset people too much

xviper

Don't let this get you down. You can upset a fat kid with a limitless credit card in a candy factory. This forum is like a candy factory and there are always fat kids and there's always some fat kid who sees the cod liver oil. Their mommas should make them ................................

WhiteS2k

Sorry, can't stop talking about this. I guess I am the fat kid in the candy store.

Anyway, are you talking about a "smart" ECU that would also "shift to a higher gear" FOR you when you hit the rev-limit? Now we are talking about an automatic transmission. If the ECU is that smart, it would have stopped you before you hit the rev-limiter also.

But if "YOU" (the driver) shifted to a higher gear, then you are talking about human behavior. A smart human driver would never repeatedly hit the rev-limiter. And if we have a smart driver, who needs a smart ECU?

The only reason for the "bounce" with the rev-limiter is because the driver keeps on doing it.

SpitfireS

WhiteS2k Posted on Jul 12 2006, 05:40 PM

Nah.. I wasn't talking about you

No, NO!
What I mean is this:
Lets take your "overtaking example".
You shift back to (lets say) 2nd when you see the gap in the opposing traffic, push the trottle to WOT and steer to the left to overtake while making left blinker blink (all in one )
Top down of course and you miss your shifter beeper because that truck makes a lot of noise. (it uses a Richmond Final Drive )
Now suddenly the car doesnt go any faster (rev limiter keeping revs & speed at a constant while still @ WOT trying to overtake).
Al of that ^^^ without the "hitting a brick wall" feeling.
Once you notice that the car doesn't go any faster, you, the driver, shifts to 3rd and off you go.
You merge back into your lane without any problems.
That truck driver never even noticed you took an extra 1.5 seconds to overtake.
Also because it was a lot faster then he/she expected anyway.....

Now thats what I mean.
Is Honda R&D reading this too?