SC Rev limiter ?

[911Brian]

During my autox today, I noticed that I hit 7k on the tach for a brief moment. Should't I have a rev limiter to prevent me from doing that.

I don't think I did any damage. It was for a very brief moment.

Thanks

[cowtown]

A centrifigul rev limiter should be built into the rotor of your distributor.
The rotating weight will short the spark signal to ground if overreved.

But this will only work if you are trying to accelerate through the rev limit. If you miss a shift (like downshifting into second at 70) the rev limiter will not help you. It can't protect against the mechanical overrev.

If you only (!) went to 7k and it was just for a second, and if the car runs fine, you're probably ok.

[Schrup]

Brian, I bounce off my rev limiter pretty regular. It kills the power at 6800 rpm. I do not have a rev limiter on my rotor, I assume it is in my cd box. Do some research, here's a good thread to start with.
3.0 rev-limiter

[ronb]

at my last DE my instructor had the revs pegged at 7k for around 30 sec until I noticed that he hadn't shifted and pointed at the tach. It didn't cut out, it just stayed at 7k...I was alarmed that he had done some engine harm, but he said not (his reason for pegging it was that he was used to his own car an SC with a much louder exhaust so it sounded like it wasn't at the limit). Should I be concerned; the car has run fine for the subsequent 2,000 miles

("notice...and point" are mild euphemisms)

[david914]

You may not have the rev limiter style rotor. Pull off the distributor cap and have a look. It'll be pretty obvious if you have a "normal" rotor or a rev-limiting style. I have a non-limiting rotor on my car and hit close to 7K every so often. Doesn't seem to hurt. I would be more worried hitting 7K without the motor under load, such as missing a shift.

[Bill Douglas]

On one occassion I was at 7,000rpm for about a minute, that was years ago and the car is fine. I think if you don't blow it up at the time you are ok.

Euro SC's have a funny looking rotor that cuts the rev's and US cars have an electrical cutout, I could be wrong but I think this is how the story goes.

[911Brian]

Wow! You guys are fast. Thanks for the responses. It did run fine after so I don't think I did any damage. It was under load at the time.

[Early_S_Man]

ROW SC's have the rev-limiting rotor ... 7000 rpm.

USA SC's have a rev-limiter which cuts off the fuel pump, fed pulses from CDI-unit ... same as drives the tachometer, set at 6500 rpm, because, I suspect, USA cars had a high percentage equipped with cruise control, which will cause the rev-limiter to activate if clutch is depressed while cruise control is active!!!

I know of nothing that would cause USA cars to 'need' a 6500 rpm limit ... other than a falling power/torque curve.

[rdane]

I have a '79 US car. I have hit the limiter once while at 7K+ for a number of seconds. Car acted like it was out of gas. Once it slowed the compression restarted it and away we went.

I shift between 6.8 and 7K on a regular basis and no limiter kicking in.

I would throttle anyone who held my car at 7K for 30 seconds.

[banjomike]

The people at pelican insisted that a 79 SC motor does not use a rev limiting rotor, the CD unit is the limiter, though I have seen 7k on the tach too, and never hit the limiter. Who knows?

[1980SC]

Originally posted by banjomike
Who knows?

We know.

As far as 3.0 SC's :

Euro = rev limiting rotor to cut spark.
USA = speed limiting relay that cuts power to the fuel pump. (not the CDI box)

-Rob
1980sc euro (with rev-limiting rotor)

[ronb]

Mine just stayed at 7k without loss of power...which means what?

[john walker's workshop]

the limiter is a black plastic box, attached to the SIDE of the left front cowl area, just ahead of the gas gauge, and behind the hood hinge. it has kind of a raised X on the front. not to be confused with the other relays that mount on the floor of the cowl area. they can also go bizerk, and cause some jerky driving. unplugging it fixes that problem, but deletes the over-rev effect.

[911Brian]

Thanks John! I will check and see if mine is even hooked up.

[rdane]

"Mine just stayed at 7k without loss of power...which means what?"

I suspect it just means you didn't hit the limiter.

[1fastredsc]

I wouldn't be worried about damaging the motor with 7k revs either. If damage were done, you'd know it, either a rod shooting out the side of you motor or a bent valve. 7k isn't that big of a deal anyhow unless you own a carrera and run the risk of breaking the weak rod bolts that they came with.

[david914]

Hmmm. I've never hit the rev limiter either, and I've owned the car since 1995. Either it's broken or it was disabled somehow by a PO.

[SpeedracerIndy]

Originally posted by 1980SC
We know.

As far as 3.0 SC's :

Euro = rev limiting rotor to cut spark.
USA = speed limiting relay that cuts power to the fuel pump. (not the CDI box)

-Rob
1980sc euro (with rev-limiting rotor)

Exactly what I found out. You can always add the rev limiting rotor also. Can't hurt anything by adding a second rev limiter especially if one of them doesn't work. I have a 6800 limiting rotor. Just make sure you have a pop-off valve incase you get an intake backfire from a loss of ignition but no loss of fuel delivery. Pelican does not carry rev limiting rotors for SCs. I had to get mine from Vertex for $20.

[rdane]

I am told a SC P&Cs would have hard time hitting anything it you go a bit past 7K reving the engine in normal shifting. I suspect the limiters are 7100 to 7300 some where. My "limited" experience is you'll also have to hold it there awhile to get it to cut your fuel line supply. I would supspect not hitting them over not having them as much as I have revved my car since the first experience. I run it up to 7 on the track most every shift, I just don't run it past 7 or drive at 7K. Haven't hit the limiter since.

Like Souk, the first one scared me a lot

[Schrup]

My limiter kicks at 6800 rpm religiously, scares the poop out of me if I'm not expecting it. The car lurches pretty hard from the loss of power.