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Posted by: ww914 May 12 2013, 06:15 PM

I don't trust my tach and my rev light died. Thinking of installing a rev limiter. What do you guys think?

Posted by: wndsrfr May 12 2013, 07:51 PM

For the /4 "Buttercup" I'm on SDS injection & ignition so rev limiting is built into the fuel map program....got it set at 6750rpm.
"Kermee" the /6 is on a crankfire unit and it has a three stage "soft" ignition cutout that operates to keep it below 7200rpm.
I have touched the limiter now and then when enthusiasm overtakes clear thinking...

Posted by: SirAndy May 12 2013, 09:39 PM

Same here, came build-in with the engine brain ...

Posted by: koozy May 12 2013, 11:18 PM

If you have a distributor, just run a simple rev limiting rotor. You don't really need one since typically the high rev stuff that destroys engines are done on downshift and the rev limiter won't save you from that. If you can't trust the tach, you shouldn't trust a shift light either. If you have had the car for some time, I'm betting you can trust yourself to know when to shift without relying on a mechanical devise to tell you.

Posted by: McMark May 12 2013, 11:34 PM

He's got a Mallory. No rev-limiting rotor.

You could go with an MSD unit, and as a bonus multi-spark. Lots of people are running them reliably, but there are enough failure stories out there to take notice and keep it in mind.

Posted by: koozy May 13 2013, 12:05 AM

Replacing the shift light is an option I'd consider. Honestly, a rev limiter wouldn't be any better unless you tend to ignore the shift light. One thing you don't want to do is use the rev limiter as a shift indicator so..... The light may work better for some folks.

Posted by: ww914 May 13 2013, 06:33 PM

Mike

I think you're right. I should know when to shift this car. Summit Racing is going to replace my shift light. I will set it way before I reach redline.

Mark

What do you think the safe redline should be?

Posted by: Randal May 13 2013, 09:32 PM

If you are running on the edge at an autox it's difficult or just plain impossible to watch the tach.

Having a shift light and sophisticated rev limiter, i.e., one that first cuts electronics then fuel, is very valuable.

And the bigger and more well placed (in line of sight) the shift light the better.

Posted by: SirAndy May 13 2013, 09:37 PM

I see an app for the Google glasses in our future!

Posted by: Randal May 14 2013, 11:36 AM

Sign me up!

Posted by: wobbletop May 14 2013, 12:08 PM

MSD-6AL

Posted by: yeahmag May 14 2013, 04:42 PM

Mallory 6AL

Posted by: ww914 May 14 2013, 04:46 PM

What are the advantages of either MSD or Mallory ignitions other than gaining a rev limiter?

Posted by: yeahmag May 14 2013, 05:00 PM

The Mallory 6AL (my preferred unit) has a built in pot for adjusting RPM in 250RPM increments and puts 500V to the coil with multi strikes below 3K RPM. That means I can run plug gaps in the .045" range, starts and idles like a champ, and will create a light show if one of your plug wires comes loose.

Posted by: McMark May 14 2013, 11:00 PM

Fuel mixture at idle is always a bit erratic because of low flow velocity and low mixture 'swirl'. The MSD and Mallory 6AL will fire the spark plug multiple times instead of just once. Those multiple strikes increase the chances that the poor mixture will actually ignite. This function goes away around 3000 rpm because 1) the coil can't support it and 2) it wouldn't have much affect at those RPM anyway due to proper air fuel mixture/port velocity/swirl.

The increased voltage to the coil will allow for larger spark plug gaps (as Aaron mentioned) which increases the size/length of the spark. A longer spark comes into contact with more fuel mixture, and also increases chances of ignition.

Posted by: Matt Romanowski May 15 2013, 06:47 AM

The new MSD boxes have the same adjustable RPM limit right on the box. The old ones took pills.

Posted by: toadman May 16 2013, 08:29 PM

Are the MSD and Mallory units you are talking about being used on fuel injected or carbed engines?

Posted by: yeahmag May 16 2013, 09:17 PM

I only see them in carb'ed motors with motor work. No need on a stock or near stock motor.

Posted by: 914z May 23 2013, 01:59 AM

Mike,
One big question is WHY DO YOU NOT TRUST YOUR TACH? It's pretty cheap to have it re-built. The best rev limiter is of course your foot and your brain. A light (idiot light) can refuse to work at the most inopertune time, i.e. when you rely on it.
Have the tach rebuilt and set the face of the tach so that the red line is pointing straight UP.
Also, as some one said a rev limiter WILL NOT work on an over revved down shift or missed shift. I race and I have only over revved once; cost me a new engine, $10,000 adds up real quick, so you only do it ONCE. That is unless you need a new engine.

Posted by: Downunderman Jun 2 2013, 07:43 PM

I run two shift lights, upshift set at 7,100 and downshift set at 5,000. Giving it a buzz on a downshift is how motors get destroyed.

Posted by: MikeSpraggi Jun 11 2013, 03:45 PM

MSD-6AL. Works for me for the time being.