Wireless tach pick up

[Craighell]

Hey folks,

I have a need to hunt down a kit or plans or complete working assembly. Reason for this goofy mthod rather than just a simple clamp on inductive pick up:

I have a chassis dyno for motorcycles. Getting access to plug wires is easy on Harleys and import bikes (prior to 1986), but late model sport bikes have so much body work, it can take 30 minutes to get the tank, sidepanels and sometimes airbox removed. Then I sometimes discover the bikes have a coil in cap set up that only allows me a low voltage signal.

I do have the ability to perform the above , but most customers are so cheap, they think that the $30 base dyno run shouldin clude the 1/2 hour to disassemble their bike and the 1/2 hour to reassemble it as well.

So, since I building my own BS2 based interface for the dyno (to include Wideband O2 data logging) I figured I might be able to pick up ignition signal with out removing body work. Sometimes I can see the plug wires with just a little body work removed, but thre is not enough room for the clamp to get in there. Hence the antenna idea.

I like the idea of disassembling a timing light though. Sounds like I would at least get an isolated signal. I'll have to look into that if I can't find an antenna or quick 'wire-wrap' method.

Thanks for any help.
Craig

 

[BartSimpson]

Funny, I just ran across a similar circuit a couple of days ago that caught my attention. The circuit is entitled "Speed-limit Alert" but it's based on detecting spark pulses in a 'wireless' fashion. It's rather informative yet brief discussion and I have no idea if the circuit has ever been tested, but it looks detailed enough. Go to:

http://xoomer.virgilio.it/fladelle/Page23.htm

My appology if the link is no good. Let me know as I can scan my printed copy & send it.

Rick

 

[yoyo133]

Most bikes already have tachs. If not, an easy way (assuming the wire is more accessible) is to tap off the alternator before it gets to the rectifier and read the pulses off of it. Virtually all 2-stroke outboard motors use this method for the tach. Generic outboard tachs are readily available, cheap and are adjustible for 2,3,4,6,12 pole alternators etc.. Not wireless but perhaps a solution.

 

[Craighell]

Thanks Bart, that may be the answer to my needs and wants. I'll have to try it out.

Yoyo; The need for the pick up is not replacement of the factory tach (many cruisers don't have tachs or the tachs on the bikes are not very accurate - Hondas are highly optimistic - the 400cc CB1 only turned a little over 10,000 rpm when its tach read 13k!). Rather, the dyno software can not give torque readings without getting a tach reading.

Why not just use the inductive pick up?
The inductive clamps either will not work on coil-in-cap set up on most modern sportbikes or require cutting of customers wiring to the cap/coil. Customers want the torque readings and bitch 'till you get the body work off then sh*t when you tell them you're going to do some minor surgery to their wires. That's when they say 'Oh no, don't separate the wires just put the body work back on. I'd rather have hp vs mph readings than torque-hp vs rpm and a mangled harness'. Guess how many customers graciously offer to pay for the wasted labor?

The antena would let me do that. Since I'll be throwing out the stock dyno interface stuff to use my own, this seems like the way to.

Thanks,
Craig

 

[BartSimpson]

Craig, one more thing that just came to mind. A while back when living in the Seattle area we were forced to get our cars smog checked every couple of years at a state-run test facility. They have you drive into a bay & up on their dyno. Then the sniffer probes are placed into your tailpipe (the car's I mean). Then they place a tach pick-up gizmo on top of your hood to read the rpm's. There is no need to lift your hood, and they usually don't. So for what it's worth, a quick bit of calling around might find you all the manufacturer's information of the instrument so you don't have to reinvent the wheel.

For what it's worth.

Bart