Measuring RPM on a rotary engine?
#1
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Measuring RPM on a rotary engine?
I just bought an automotive DMM, it has a tach settings for 3,4,5,6,8 cylinder engines. I want to set the idle etc, etc and would like to avoid running back an looking at the dash to do it
QUESTION: would any of these settings give me the true rpm on my '91 N/A?
Also, where would you connect the beast to take the reading?
QUESTION: would any of these settings give me the true rpm on my '91 N/A?
Also, where would you connect the beast to take the reading?
#6
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The test connector at the trailing coil (the furthest front coil set) will give you the reading of a 6 cyl. This is what I have used for remote starts that monitor RPM, and it is generally very accurate.
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Mark, the green connectors?
I'm at work, so I can't look at them, but are you referring to the single
green colored test connector that you normaly ground or the ones near by?
green colored test connector that you normaly ground or the ones near by?
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#8
Former Moderator. RIP Icemark.
Re: Mark, the green connectors?
Originally posted by asherwood
I'm at work, so I can't look at them, but are you referring to the single
green colored test connector that you normaly ground or the ones near by?
I'm at work, so I can't look at them, but are you referring to the single
green colored test connector that you normaly ground or the ones near by?
#9
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OK, here is the theory on this. For every revolution of the eccentric shaft, each rotor will fire once. This is a total of 2 firings/revolution. On a 4-cylinder boinger, 2 of the cylinders will fire once for each revolution (otto cycle, each cylinder fires every other time it reaches TDC). Therefore, 2 firings/rev = 4 cylinder, all day and forever, even! On the 89+ cars, both the leading and trailing coils have a tach wire on them. I believe that both of them output at exactly the same frequency, since the trailing and leading trigger signals are the same, with the exception that the trailing coil has an additional select signal, to pick the coil. I believe that the tach is derived from the timing signal, not the select, and they are therefore the same, that is 4-cylinder equivalent.
Well, that's my story and I'm sticking to it!!!
Irv, Keith's dad
Oh yeah, if you are going to measure tach right off of the coil, you must use leading (front) coil, since each trailing coil fires only 1/revolution, the equivalent of a 2-cylinder!
Well, that's my story and I'm sticking to it!!!
Irv, Keith's dad
Oh yeah, if you are going to measure tach right off of the coil, you must use leading (front) coil, since each trailing coil fires only 1/revolution, the equivalent of a 2-cylinder!
#11
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Soo, which is it? 4 or 6cyl? The DMM I'm using doesn't say anything about rotary (of course) but has 3,4,5,6,8cyl options and it says to multiply the reading by the number of cylinders selected.....
**I'm using the induction coil/signal pick-up clamp ("clamps" loosely around spark plug wire to detect the current) provided with the DMM
**I'm using the induction coil/signal pick-up clamp ("clamps" loosely around spark plug wire to detect the current) provided with the DMM
#13
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Hey, I used the search function. The function EVERYONE complains about people NOT using. I want answers, was thinking I might get some from this thread. I DGAF if its 12yrs old. Why should I start a new thread?
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Try it on 6 cylinder setting.
Induction clamps are tricky too,so you gotta set them "just right".
Last edited by misterstyx69; 01-18-13 at 01:57 AM.
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a two rotor has a spark event every 180 degrees of crankshaft rotation, just like a 4cylinder. a 3 rotor has a spark event every 120 degrees like a 6 cylinder.
#18
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Right on! Thx guys! -I assume that I still multiply by 4 as well? Or? -Tryin' to verify if my starter is cranking fast enough....don't believe it is...
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