Any ideas where the rev limiter is on a 90 C2

[D Hanson]

Have Ruf chip, intakes and etc. The Ruf guage marks 6,800 as red line. I was not paying attention today on the highway and hit perhaps 7,200 rpms in 2nd. No lag, no drop-off in power, no funky sounds, just kept pulling.

Do some chips remove rev limiter completely. I had intended to keep this car below 6,600 just to be safe. It was just this dam SUV mom yacking on her cell phone, not paying a dam bit of attention and me trying to get around her and I pegged it hard.

[Jim Smolka]

The rev limiter is part of the chip inside of the DME. Aftermarket chips often increase the RPMs allowed

[D Hanson]

I am sorry, poorly worded question. I am just curious if I even have a rev. limiter programed into the chip that is currently installed in car, and if so, any idea what rpm would be max. I cannot image a rev limiter of 7,400 or higher without redoing the inside of the motor.

[masraum]

your best bet would be to call a Ruf dealer, I think there is one in Canada called "Weissach".

I can't imagine that Ruf would completely remove such an important piece of safety equipment as the rev-limiter.

If your tach says 6800 then let it run to 6800. They wouldn't design the tach that way if it weren't capable of doing it.

[svandamme]

i don't see the need for a rev limiter, i know how far the engine is allowed to go, and shift when before i get there
since a rev limiter doesn't do a thing if you have a bad shift, it don't see how it would be a safety device..

[SpeedracerIndy]

Originally posted by svandamme
i don't see the need for a rev limiter, i know how far the engine is allowed to go, and shift when before i get there
since a rev limiter doesn't do a thing if you have a bad shift, it don't see how it would be a safety device..

Ya, I used to think that too. Then one day I shifted into second at redline, and the gear shifter popped out of gear when I punched it (tired 2nd syncro). VROOOOOOOM, WAY past redline. I don't even want to know how high I got it. I just count my blessings that I didn't do any damage. Needless to say, the very next day I ordered a 6800 rpm rev limiter. Cheep insurance.

[svandamme]

a rev limiter doesn't limit the revs if you shift accidently down instead of up, at leat that's how i have been told...

edit: i guess popping out of gear is the same thing as a misshift
except the rev limiter would work... but then again , unless you do this on a daily basis, it shouldn't kill the engine , it's not good, but unless you overrev it for 2 minutes straight, i guess the chances of actually killing it are slight

[masraum]

Granted a rev-limiter will not help if you put the car in 1st at 80, but if you try to put the car in second and miss while fully in the gas it will protect the engine. Imagine that you are coming out of a corner hard on the gas and at 4500rpm one of your driveshafts lets go. I don't want my stock motor to hit 9000rpm for even a short time. If the valves float you can end up with valve to piston contact.

I know where the rev limiter is, but it's still possible to hit the rev-limiter. Most of use do on a regular basis. I don't as often as I used to, but it still happens.

Yes, I stand by my statement that a rev-limiter is a safety device and a good thing to have.

[D Hanson]

I was merging on an on ramp through heavy traffic with this slow arsed SUV in front of me blocking the merge lane. I nailed it, pulled around the suv, looked down to shift and then noticed the 7,200. Not happen alot, but I have done this before.

So it safe to assume I have no rev limiter, or is it actually set higher and I could go higher if I wanted.

[svandamme]

some cars, 2.4S for example , have factory rev limiters of 7300 , maybe others go higher?

[Jack Olsen]

The rev limiter is definitely a safety device, especially on a 964, where the connecting rod bolts are notoriously weak.

Even with your 2.4 S, and no rev limiter, it would be possible to destroy the motor in far less than 2 minutes.

[ChrisBennet]

Originally posted by svandamme
i don't see the need for a rev limiter, i know how far the engine is allowed to go, and shift when before i get there
since a rev limiter doesn't do a thing if you have a bad shift, it don't see how it would be a safety device..

It's not a problem on the street. I can't count the number of times I've hit the rev limit at the track though. You just can't hear the motor the way you can in "normal" driving.
-Chris

[D Hanson]

Regardless, I apparently am not the expert driver some of you guys are and I am prone to letting those RPMs soar in traffic situations.

To be safe, could I get a rev limiter programed onto my Ruf chip without changing any other mapping/information on that chip?

[masraum]

I believe the answer is yes, if you can find a knowledgable tuner.

I know that if you had a 3.2L car Steve W could, and has even shown how on this board, but I believe the 964 chip would be a little different. I'm sure Steve Weiner at Rennsport Systems in Portland Or would be able to help too, but you'll probably want someone closer to home.

[Jack Olsen]

The RUF chip almost certainly has a rev limit on it. You should call them and find out what it is. If you have not modified the internals of a 964 motor (especially those connecting rod bolts), then you should definitely not raise the rev limit.

[Steve W]

The rev limiter is certainly within the chip. It is a single value within the eprom, and is computed by taking the hex value, converting it to decimal, and multiplying it by 40. As the maximum a hex value can be is FFh, which is equivalent to 255 decimal, the maximum a rev limit can be set is 255*40 or 10,200 rpm, essential no rev limit. If you are not able to find out what the limit is, just let me know and I can read it and find out what it is exactly. It can be reset by erasing and reprogramming this single hex value.

[ischmitz]

How about putting one of the dual chips into your car. With the flip of a switch you can change between the stock chip and the performance chip.

I you want you can get the performance chip with the rev limit set to stock for peace of mind.

In general I think the rev limiter is a safety decive. I have hit mine more than once when things got wild. I first get I can't even get the pedal to the metal before it prevents total engine destruction. But also in second it has prevented disaster for me.

Ingo

[ischmitz]

Originally posted by Steve W
The rev limiter is certainly within the chip. It is a single value within the eprom, and is computed by taking the hex value, converting it to decimal, and multiplying it by 40. As the maximum a hex value can be is FFh, which is equivalent to 255 decimal, the maximum a rev limit can be set is 255*40 or 10,200 rpm, essential no rev limit.

Steve, are you sure the 964 motronic use the same single value coding for the rev limit like the 3.2?

Ingo

[Steve W]

Looks like it to me Ingo - is there something that I'm not aware of?

[KTL]

I recall reading that increasing the rev. limit increases the inertial load on the rotating motor components by the square of the speed increase.

So an increase of the rev. limit from say 6250 to 7000 is a 12% increase in speed. 1.12 squared is about 1.25 So some of your internals (crank ends, pistons & wrist pins, conrods, rod bolts.... ) are seeing a 25% load increase. That's a big increase.

I'm no engine builder by any means. Just something I read in a turbo book.