RPM from a DMM, SJ CDI mod questions...

[smoofers]

Hey all,

So I am thinking of modding the rev limiter on my 91 SJ. I read all the posts on how to do it and am confident in my abilities....

My question is, since I don't have a tach, has anybody tried to catch the charge coil wires and read them with a multimeter? I figure as long as I am at or under 140hz (~8400rpm) I should be good....

Any input?

 

[93rx7]

I've been looking into doing this on my square too.. 6000rpm just isn't enough!

I'm just confused on what I need to buy, there is a lot of different info in the thread on here.

 

[Matt_E]

Hey all,

So I am thinking of modding the rev limiter on my 91 SJ. I read all the posts on how to do it and am confident in my abilities....

My question is, since I don't have a tach, has anybody tried to catch the charge coil wires and read them with a multimeter? I figure as long as I am at or under 140hz (~8400rpm) I should be good....

Any input?

You'd need twice that, 280 hz. Both plugs fire twice per crank revolution.

 

[orangefinger]

send your cdi to keefer

 

[Cliff]

ive got an almost new enhancer if your intersted

 

[Moondance]

send your cdi to keefer

x2

 

[smoofers]

Eh, no need to send it off.... you guys can send your CDI's to me though, cause I'm done and it works....

 

[Mouthfulloflake]

what are you going to re-seal it back up with?

I have to do one for superx2.

 

[smoofers]

For now I just sealed it back up with some blue RTV silicone..

 

[93rx7]

For now I just sealed it back up with some blue RTV silicone..

Can you list the 3 parts you soldered on there?

 

[smoofers]

Can you list the 3 parts you soldered on there?

-Two 36k ohm 1% tolerance resistors @ 20cents a piece
-One 100k linear dashpot (single-turn) @ $1.25

Since I don't have a tach I pre-set it at like 70k ohms, I installed it, reved the motor to the moon, turned it all the way up, reved it and it bounced the limiter at probably 6800 RPM (guess) and then turned it down about an eighth of a turn so I would estimate it is at ~80-90K ohms. If I had to guess, I would say it is set at about 7500-8000 RPM, but I won't know for sure untill I put a tach on it and can set it accurately.

The actuall thread in the tech FAQ doesn't really tell you much, you just kinda have to take a leap of faith. The potting compound on my CDI was pretty soft and I was able to gently pry it of the circuit board with a 90 degree pick. I cut the plastic with a dremel wheel. The dashpot resistor setup metered at ~60-160k ohms by itself. After soldering it in and just metering the leads where they met the circuit board they resistance went from about 40-55k ohms (min to max).

 

[SQUARE JOEL!!!]

I have a tiny tach if you need to use it

 

[smoofers]

I have a tiny tach if you need to use it

Hell yeah!!! If you would let me borrow it for a weekend or so that would rock! You are welcome to ride with me, I know it would do you some good. Keep in touch dude!