Inductive Tachometer

[deerio]

So I wanted to try messing around with the NIKKI carb since I have a vacuum gauge and thought it might be a good idea to do a little tuning... I have no tachometer available but I also did not want to spend too much on one since it would only be used for tuning purposes at this time. I ended up purchasing a cheap inductive tachometer and it works great!

My problem at the moment is that I need to know which setting on the tach is correct for the E1 motor.

My options on the tach are:
#1 - Spark plug firing twice per revolution

#2 - Spark plug firing once per revolution

#3 - Spark plug firing once per two revolutions

I guess I'm confused partly because I'm not sure what is considered a revolution? Is it the entire cycle from intake to exhaust? Or is the intake/compression and power/exhaust stroke both considered each a revolution? I've also read a little bit on wasted sparks which confuses me even more.

Any thoughts?

[difrangia]

Once per two revs. The distributor makes one rev per two revs for the crank. The igniter (distributor in this case) determines spark count.

I'm not personally familiar with crank fired engines, but I'd envision them firing once per rev with one being wasted on a four stroke engine at the top of the exhaust stroke. I'd guess that if there were a crank fired two stroke, none of the spark would be wasted.

[deerio]

Thanks Steve, I was thinking you'd be one of the first to reply! I think that's what I had selected but I'll double check once I get home.

If true, then I had the idle set around 750rpm and was able to get a steady max vacuum of about 18mmHg... The motor does sound better and a bit peppier, as well as less boggy when revved quickly, so I suppose I did something right?

[deerio]

Well I guess #3 one spark per two revolutions definitely isn't the correct setting for this inductive tach... It ends up showing idle as 2500-2600 and even just a quick blip of the throttle will shoot it upwards of 6k and possibly a redline past 9k LOL... Even if I tried there isn't enough adjustment on the throttle screw to bring the RPMs down enough.

Under the #2 setting, one spark per revolution, idle shows as 1250-1300... However, in order for me to get it down below 1000 the adjustment screw would have to be all the way out, and there isn't much adjustment between it and the mixture screw to keep it stable...

When using the #1 setting, two sparks per revolution, idle is fairly steady around 700... However, when I rev it up, the redline probably won't show past 3500...

Really tempted to just get a regular tach but I'd atleast like to know how this whole thing is supposed to work

[63 320]

strange way of marking the tach settings usually they are marked 4 cyl, 6 cyl, and 8 cyl.
The readings you got at idle make it seem that 1 is 4 cyl, 2 would be 6 cyl and 3 would be for 8 cyl engines

[deerio]

It's strange to me as well... Any ideas how high the E1 actually revs up to? If it's not far from 4k then the #1 setting seems believable.

[63 320]

it is rated 60 hp at 5000 rpm not sure myself how high they can rev. past that