how do rpm guages work?

[Z.hb71]

so i saw the trailtech rpm gauge for rc's and i noticed that their is just a ring that goes on the bottom of the spark plug and no sensor, how does this work? does it pick up pulses or sparks from the coil or plug or something?

 

[Cupton79]

The one with the ring is a temp sensor that goes under the spark plug.. you just take the crush washer off and put the sensor ring in it’s place and tighten the plug down... the RPM gauge wraps a wire around the plug wire multiple times and then tie it back to itself... 2 totally separate gauges.. both work very well.. I have both on my Baja

 

[Z.hb71]

The one with the ring is a temp sensor that goes under the spark plug.. you just take the crush washer off and put the sensor ring in it’s place and tighten the plug down... the RPM gauge wraps a wire around the plug wire multiple times and then tie it back to itself... 2 totally separate gauges.. both work very well.. I have both on my Baja

ok but stil, wrapping a wire around another then, how does it work?

 

[Polar_Bus]

digital RPM gauges are "inductive pickup". You wrap the sensor wire around your sparkplug wire and the electrical ignition pulse is read each time the plug fires. The CPU does the conversion math and outputs an RPM based either 4 stroke or 2 depending on how you have the unit configured.

 

[Cupton79]

It senses the pulse.. here’s a pic of how I wrapped it... been working fine for almost 2yrs now

 

[Z.hb71]

digital RPM gauges are "inductive pickup". You wrap the sensor wire around your sparkplug wire and the electrical ignition pulse is read each time the plug fires. The CPU does the conversion math and outputs an RPM based either 4 stroke or 2 depending on how you have the unit configured.

mm makes sense, thanx.

 

[Milo]

The TTO type uses pulses through the coil wire like a CT (Current Trasformer). Others are optical and I’ve not looked at how those work and some are magnetic similar to a CT but more like a solenoid.

Sorry for the baffling explanation.

 

[Phill2]

This is the one I have on mine
https://www.ebay.com.au/itm/Inducti...sh=item1ef398f59a:g:u40AAOxyJX1TFCMX:rk:11??0
Works well

 

[1Coopgt]

So silly question. Why would someone want one of these? It's not like we can over rev these engines . And you can't monitor the gauge while you're running the car.

 

[Z.hb71]

So silly question. Why would someone want one of these? It's not like we can over rev these engines . And you can't monitor the gauge while you're running the car.

It's just to see peak rpm I guess.

 

[1Coopgt]

Sooooooo after you max it out that first time with the gauge it's kind of a waste after that? Granted they are cheap so I guess it doesn't matter .

 

[Phill2]

So silly question. Why would someone want one of these? It's not like we can over rev these engines . And you can't monitor the gauge while you're running the car.

They're very handy when tuning esp if you have a Go Pro facing it to tune HSN

 

[Z.hb71]

Sooooooo after you max it out that first time with the gauge it's kind of a waste after that? Granted they are cheap so I guess it doesn't matter .

I guess. Or like Phill said, for tuning

 

[Polar_Bus]

So silly question. Why would someone want one of these? It's not like we can over rev these engines . And you can't monitor the gauge while you're running the car.

A tach , a stopwatch and a big parking lot are the only TRUE ways to tune your engine to it's full potential. With a tach and a stopwatch you can fine tune your engine and track the data. Once you establish peak power and RPM's and the quickest acceleration (on pavement, NOT dirt) richen the high speed needle 1/16 of a turn to maintain a safe mixture. I've been tuning 2 strokes for the past 30 years, and it's difficult to efficiently tune a RC because your not IN the vehicle feeling the performance losses or gains, you can only observe. Now you have to rely on your ears. If you hear a 2 stroke detonate crackle, it's too late as internal damage has already occurred . Reading a sparkplug "chop" is another advanced tuning method but you really need a magnifying glass to read the insulator. 2 strokes are tough to master the tune, but always remember, it's better to foul a $2.00 plug than melt a $50 top end, so be prudent and give up a few hundred rpm's and stay on the rich side of your tune.

 

[1Coopgt]

Interesting . I don't race so I don't think I need to be quite that persis . I've got a good ear for tuning and I make sure not to lean the engine out .

 

[Milo]

I have mine for tuning, although it’s not really needed as mentioned, but it handy to see on the transmitter. Temperature is more improtant though which I can also see.

 

[Polar_Bus]

Temperature is more improtant though which I can also see.

Agreed, I have a tach and to further protect my "investment" a temp guage is next on my purchase priority list. Not too worried about it in the upcoming cooler temps, but definitely have one for the hot summer season.

 

[Cupton79]

I’ve had a temp gauge on mine for a while.. not sure how hot is too hot though... I’ve noticed mine seems to run its best around 300-320ish of course that’s at the plug... the cylinder is usually about 100 degrees cooler checkin with an infrared temp gun...

 

[Z.hb71]

I’ve had a temp gauge on mine for a while.. not sure how hot is too hot though... I’ve noticed mine seems to run its best around 300-320ish of course that’s at the plug... the cylinder is usually about 100 degrees cooler checkin with an infrared temp gun...

ok i think ill need a temp 1 too.

 

[1Coopgt]

I picked up a temp gun to monitor the boat motors and the ESC's . So it can pull double duty now . I honestly don't think I'll use it that much for the buggy. I'll just become paranoid . That's the last thing I want . This hobby is suppose to help me relax and keep me busy . I wouldn't no what is to hot anyway .