What tach to buy for a Rotary?

[bill f]

Could one of you guys/girl care to enlighten me? Do I ask for a 6 cyl/8 cyl/12 cyl unit?

My understanding of the ignition process is that each rotor has three firings per excentric rotation, and that means six. However, that is the equavalent of a 12 cylinder engine, is it not?

I'm confused, and in need of information. Please?

Thanks.

Bill

[This message has been edited by bill f (edited October 02, 2003).]

[bill f]

Oops. I ment three excentric rotations per rotor rotation...now I'm really confused!

Help!

Bill

[paulydee]

Well Bill I am not sure what tach to buy, but I have been told as far as shift lights are concerned you have to buy a RPM pill that is half the RPM you want the light to go off at (i.e. 4000RPM pill for 8000RPM light activation). Doen;t answer your question but might shed some light ont he subject.

PMD

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Paul D'Angelo
73 ITS CENDIV
Indy Region
www.iridiumracing.com

[Speed Raycer]

Any tach that can be set to 4 cyl will work.

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Scott
It's not what you build...
it's how you build it

<A HREF="http://www.pfmracing.com" TARGET=_blank>
www.pfmracing.com </A>

[bcarter]

Autometer Tach that goes to 10,000 works great for me. Attach to the leading coil.

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G. Brooke Carter
Wheat Buckley Racing
# 10 Challenge Car
2003 Class Champion
Calgary, Alberta

[Speed Raycer]

Why the Leading? I've always heard the trailing so that you know if the trailing goes out or not.

[RX767]

With inspiration from the movie "Spinal Tap", I bought the VDO Tach. that goes up to 11. ( it must be better)

The directions made no mention of rotary engines. I called the company and spoke to one of their engineers. It is wired to the lead coil and I set the switches for a 4 cylinder engine.

Bill Emery
Glen Region
ITA#23

[bcarter]

I forget why leading, I'll have to dig out my paperwork and see if I wrote it down.

I have it on leading and it works.

If trailing goes down, you won't need a tach to tell you, you'll just go slower and it'll sound rough.

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G. Brooke Carter
Wheat Buckley Racing
# 10 Challenge Car
2003 Class Champion
Calgary, Alberta

[Speed Raycer]

Ok, that makes sense. I think I'll keep it the way I've got it that way it'll be obvious whats going on instead of me trying to trouble shoot at the track when I get the 5 minute call

I had my trailing go out on me after I tossed a fan belt (must have smacked the ignitor or something) and didn't notice any change in how the car ran except that my tach was dead. The first time in our new RX7 I ran an entire T&T w/o the trailing (tach wire was on the leading MSD). If the trailing makes that big of a difference, I can't wait til the next T&T now that I've got it rewired!

[ITA240]

"that goes up to 11. "(Bill Emery)

"that's like, one bettuh.(spoken in my best terrible british accent)"