Changing exhaust on a 79 sc eliminates the rev limiter?

[FinallyGotOne]

As a few of you know I backdated my exhaust to a 1974 heat exchanger and OEM 74 muffler. Now I can run my rev through the maximum tac without any issues.

I was just curious how this has happened?

[javadog]

Originally Posted by FinallyGotOne

Now I can run my rev through the maximum tac without any issues.

What does this mean, 'zactly?

Elaborate in plain English, please.

JR

[Porsche_monkey]

Do you have the rotor based rpm limiter? It is difficult to believe these two events are related...

[Kemo]

maybe you had a clogged up exhaust and couldt rev all the way... longshot guess

[FinallyGotOne]

Well it used to cut out at about 6500 RPMs and stutter. I believed that was the rev limiter? Am i mistaken? would not surprise me if i am.

But since the work was done i run clean through the bottom of the tachometer without any cutting out.

[mb911]

doubt its exhaust related although it will rev easier with free flowing exhaust it has nothing to do with the limiter itself

[Bill Verburg]

On a '74 the rev limiter would be in the distributor rotor

6500+/-200 is the correct limit for a '74 2.7 CIS engine

[Doug Steinel]

If this car is a '79 SC with a Bosch CD unit, I think the CD unit has the rev limiter built into it. Changes in the exhaust should have nothing to do with it.

[Bill Verburg]

Originally Posted by Doug Steinel

If this car is a '79 SC with a Bosch CD unit, I think the CD unit has the rev limiter built into it. Changes in the exhaust should have nothing to do with it.

They changed from the ignition cutoff to the fuel cutoff when cats came w/ the cars. The old ignition style cutoff could ruin a cats day pretty quickly

[javadog]

Assuming you still have the stock tach, it should have markings to 8,000 rpm. From your description it sounds like you are revving your engine higher than this. Unless you have a really nice race motor, that is way past the safe limit for any 911 engine I can think of. Might I suggest that you not do this?

What model 911 are we talking about here? What engine?

JR

[FinallyGotOne]

yep, stock 911 sc. white guages only go to 7000 rpm. pretty much stock. so what i was experiencing was a fuel cut off then not a rev limiter? so there is no fuel cutoff anymore. And sure i don't rev to that all the time, mostly just around 5500 rpms or so when i'm trying to accelerate hard.
Whn i autoX it I bury the tach in 1st and 2nd never really need to go to 3rd.

[javadog]

Originally Posted by FinallyGotOne

yep, stock 911 sc....Whn i autoX it I bury the tach in 1st and 2nd never really need to go to 3rd.

You really shouldn't run the engine that high. It's way past the power peak and really not safe. You're liable to break something.

JR