Why does my tach go bizzerk when I get it close to the engine? It works on a nitro engine just fine. I assume it's stray EMP from the ignition system.....but how do I cure it?

Nevermind....I'll find the answer elsewhere.

Let me know what you find out. Mine does the same thing. I can't get anything close to an accurate count with mine. There's just no way a 100cc engine with a 27" prop turns 11,000rpm...

Sorry you didn't find an answer in the 3 hour alloted time period.

The LHS owner is a friend of mine, I called him and I did find that having a resistor plug would possibly help along with shielding the plug wire...but neither fix would be guaranteed.

Thanks for the reply....I get frustrated when there are 22 hits and no replies....makes me feel like an outsider.

It just means that those looking at the post don't have the answer. I don't either but I can tell you that the resistor plug/sheilded wire thing doesn't make a diference. All my gas engines are that way except the 3w, which uses a shielded wire but a non resistor plug.

None of it makes a difference. I can't obtain consistent rpm numbers with my H-9 tach either. At least from the back I can't. From the front things improve but who wants to stand there at wide open throttle. I've gone so far as to paint a flat black stripe on the back of a prop to see if things got better. They didn't.

I suffered a similar fate with a Hangar 9 unit that had my G23 turning APC 17x6 showing a very similar rpm. I now have a One Touch tach from Cermark that I am quite happy with.

Karol

I bought a Glowbee and it worked fine for a couple years.I went to gas and couldnt get consistent Rpm readings from behind,front,left side of prop,right side,ect..One time i had a 21cc echo pushing a 16x8 MAS at 12,00 plus.I accidently left it outside after i got pissed when i was getting these fanominal readings[it rained that night].I bought the TNC tach from Dons and i can stand with my legs against the stab and take accurate readings now from 3 feet away.{Behind the engine].Close to $100.00 with shipping but it works great.

if you have the the sun shining on the back of the prop it seems to help... I've got the h9 tach with the voltmeter... EATS batteries.

Take the battery out when you're not using it. Same thing happens with an Eagle Tree Dashboard. Hard on batteries when left in the unit.

Well it's not really a answer but I have a globee and a TNC and both give goofly readings unless I get just the right spot and oddly enough it is with the tac almost touching the cdi box so go figure
I know it's better out near the tips the tnc will work father away but it still likes the outside 1/3 of the prop
I don't know why they don't make a simple plug in tach that could go in like with the senor seem like a simple pulse counter and led display would do the trick
maybe an electron guru will make one and get rich

I've tached both glow and gas with my TNC from the stab area with solid readings. Gas seems easier. It must be the larger props. I've never worried where the sun was in relation to the props.

I've used both the TNC and the H-9. The TNC is a far superior product but you do pay for the difference. As in anything else, quality still comes at a higher price.

An odd note about using the standard Hall sensor for rpm readings. I have an Eagle Tree system with most of the whistles and bells. The instructions note that when all the other conditions are right you can use the hub magnet foir the Hall sensor for the unit's rpm impulse. You have to use a separate pick up sensor though. If you try to wye off the hall sensor and disconnect the power lead from the leg of the wye going to the telemetry transmitter you short out the ignition. The reason for disconnecting the power wire is because you don't want two power sources to the telemetry unit. Using the ignition battery via the power wire to power the unit means you get telemetry only when the ignition triggers.

Bottom line is you will flip that prop from here to Chrsitmas and the engine won't start until you unplug that rpm lead from the ignition hall sensor.

all of the optical tachs can easily misread -badly-- if reflection is incorrect .
the H9 seems to like about a foot distance and then you must get light correct-
On my ZDZ engines - the ignition has a output which is directly read and is accurate - why the rest of the ignition guys ignore this -is likely a cost issue.

It doesn't get any more accurate than reading th hub magnet. 3w has a similar arrangement with later ignition units.

Thanks for all the replies. I did find this [link=http://www.tinytach.com/tinytach/gasoline.php#]tach[/link] . 40 bucks.....Think it'll work?

I'm not very positive about how it might work with a shielded high tension lead.

You might havr to make a short extension wire to go berween the plug and the ing high tension led to the unit can get a signal
I would call them first and tell the what you are going to use it on a sheilded high tension lead