Cheating up the tach

[XXX#40]

im not sure if it is actually that easy, i have messed with that kind of stuff before. Not on karts or anything, just trying to make a tach work with engine it wasnt designed for (2 stroke vs 4 stroke, oem tach kinda stuff, i dont remember the exact details)

tachs count the number of voltage spikes, they dont necessarily care about the height of the spikes (which is what resistors or capacitors would change) as far as i understand. correct me if im wrong

we used them in rc racing to change amp draws and spikes, so with the correct combo could cause it to miss some of the spikes?
We had a problem with the 3, if you put the wire in the wrong place, or didnt wrap it right, it would read incorrectly

 

[XXX#40]

No sir, I have messed with mine and it will change the RPM readout on the display depending on the multiplier you select, but this is on the older M3, not the newer ones as I don't own one to test.

so you have programmed it to read 5000 rpms and took it out and ran it and thats all it read was 5000 rpms max recall?
Im not saying it couldnt be software related, they jailbreak just about all stuff that runs on software so it wouldnt surprise me

 

[flattop1]

Older auto tachs you could change with resistor across the two terminals , anolog .
Digital may not be that simple . The mychron is induction , the digatron im not sure
I do know how and where you run the tach wire affects it . User controls imho only set parameters . Single cylinder two stroke counts every igntion spark adjusting for a 4 stroke or cylinder change would only double or half the count . Would not actually change it from say 5500 to 5000 .
I would say it has too be external , knowing some go to all lengths to cheat id be wrong . Ive looked inside a digitron (bad display) quickly shut the lid .

 

[flattop1]

so you have programmed it to read 5000 rpms and took it out and ran it and thats all it read was 5000 rpms max recall?
Im not saying it couldnt be software related, they jailbreak just about all stuff that runs on software so it wouldnt surprise me

I'm on board with this , if max is 5000 thats all it will show .
Same as having lap times set wrong , it wont count the laps .

 

[Renegade]

If you use your tach to tech be prepared to greet a steady stream of karts wanting "Wanting their rpms checked" . Actually you will have to "Check" each one multiple times as they adjust them. Sport of like the steady parade of fuel scientist's wanting their latest concoction tested.

 

[1fasttiller]

so you have programmed it to read 5000 rpms and took it out and ran it and thats all it read was 5000 rpms max recall?
Im not saying it couldnt be software related, they jailbreak just about all stuff that runs on software so it wouldnt surprise me

No, not exactly that simple. It is a multiplier and is used for different types of ignition systems. You change the multiplier, the RPM's read accordingly to whatever you changed it to. For example, I can set it to /2 and it will only read 50% of the actual RPM value.

 

[JPMKarting]

If you Set the RPM limit on the mychron at 5400, it won’t read past 5400

 

[XXX#40]

No, not exactly that simple. It is a multiplier and is used for different types of ignition systems. You change the multiplier, the RPM's read accordingly to whatever you changed it to. For example, I can set it to /2 and it will only read 50% of the actual RPM value.

I fully understand how to set up a mychron, I said as much, that those just set parameters even the 3 had a warning light, but it doesnt set it where no matter how many rpms you turn it will still read it, you still cant make the tach read 5000 and it read that max recall every lap.
It would take the software to see the program in dos to make those kind of changes..ie crack the mychron software.
Our home track uses their own tach so its a none issue for us, and everyone agree''s with its findings of course there isnt any money in that class either just bragging rights, and the class is structured for the local guys between 2 tracks, we figure if you wanna travel be prepared to make changes to those rules or move up to AKRA/NKA

 

[XXX#40]

Where you at Mychron Mike? is he still around?

 

[XXX#40]

You are correct you can set max rpm, to 5000 and it wont read above 5000, but it wont act like it would if thats the true RPM, above 5 it would start back at 2500, very easy to see Cameron said.
See I never go that deep, as long as I get lap times and max/min rpms per lap im good, I dont try to cheat so theres that

 

[JPMKarting]

You are correct you can set max rpm, to 5000 and it wont read above 5000, but it wont act like it would if thats the true RPM, above 5 it would start back at 2500, very easy to see Cameron said.
See I never go that deep, as long as I get lap times and max/min rpms per lap im good, I dont try to cheat so theres that

Point being, if the tech man is going off my tach on the kart, and mine is set to read 5000, it doesnt matter if it "acts" or "sounds" like it is turning 6500.....the rule was met when the tach never flashed over the RPM limit.

I'm not saying its right or wrong, I'm just saying thats how it can be done, and thats why it doesnt make any sense to use the competitors tach to read RPM. Thats like having them torn down, but letting them bring their own no-go gauges to the tech shed.

I dont really understand why everyone wants to twist these predators up anyway, any one I ever used was flat over 5000 RPM.

 

[XXX#40]

Point being, if the tech man is going off my tach on the kart, and mine is set to read 5000, it doesnt matter if it "acts" or "sounds" like it is turning 6500.....the rule was met when the tach never flashed over the RPM limit.

I'm not saying its right or wrong, I'm just saying thats how it can be done, and thats why it doesnt make any sense to use the competitors tach to read RPM. Thats like having them torn down, but letting them bring their own no-go gauges to the tech shed.

I dont really understand why everyone wants to twist these predators up anyway, any one I ever used was flat over 5000 RPM.

Here it was always understood the track tach would be used and would be the final word.
I agree on the above 5, its just making noise

 

[Bob Evans]

Single cylinder two stroke counts every igntion spark adjusting for a 4 stroke or cylinder change would only double or half the count .

All clones and Briggs small engines with magneto ignition fire on every revolution. Every time the magnet passes under the coil the ignition fires.
FWIW

I suppose it would be possible to make a low pass RC filter (resistor, capacitor) that would attenuate frequencies above 5K, or 5000 rpm. Kinda like a graphic equalizer, but there would be a lot of Kentucky windage involved getting it to trigger at just the right levels. Even then the tach would just quit reading when the signal got too low.

 

[Chris Cooper]

"I suppose it would be possible to make a low pass RC filter (resistor, capacitor) that would attenuate frequencies above 5K, or 5000 rpm. "

You're on the right track Bob (no pun intended)... Low pass (or high pass) filters can do exactly that - mask frequecies the tach is seeing based on the resistor/capacitor combination. We use R-C filters at work to minimize electrical 'noise' on sensors.

 

[Bob Evans]

"I suppose it would be possible to make a low pass RC filter (resistor, capacitor) that would attenuate frequencies above 5K, or 5000 rpm. "

You're on the right track Bob (no pun intended)... Low pass (or high pass) filters can do exactly that - mask frequecies the tach is seeing based on the resistor/capacitor combination. We use R-C filters at work to minimize electrical 'noise' on sensors.

Yeah, I made a pretty bad miscalculation there in the frequencies, 5000 rpm would be something like 83 hz, or more accurately, pulses per second.
If you could block 1 out of 10 pulses, then the motor could be turning 5500 with the tach reading around 5000.
Sounds kind of far fetched to me, but the mychron is a computer after all, so I'm sure it's subject to reprogramming

I'm just kind of thinking out loud here because I have no personal knowledge of any of this going on.

 

[CarlsonMotorsports]

If you use your tach to tech be prepared to greet a steady stream of karts wanting "Wanting their rpms checked" . Actually you will have to "Check" each one multiple times as they adjust them. Sport of like the steady parade of fuel scientist's wanting their latest concoction tested.

That is EXACTLY what happens. Same as the fuel chemists.
When you see the same kart 3 times before the first heat race -- you know something's up.
This is particularly true with the baby champs (Subaru engine with governor) and Predator classes using a governor.
I have not seen it played out in the LO206 the same since their rev limiter is digital (ie in the coil) rather than mechanical with the governor, but tech men still need to check them with YOUR OWN tach - trust me, I've seen plenty of differences in tachs. Some, I am convinced were meddled with.
My veteran ears can still tell the difference of 5000 rpm and 5500 rpm.

Yea, where is Mychron Mike (or Devan, or whomever) these days. Their input would be much appreciated.

 

[alvin l nunley]

Amazon has multiple handheld, noncontact and contact, tachometers. I'm not absolutely sure, but one of them looks like it has a wire with a clip-on device that probably clips on the spark plug wire. With the noncontact type you have to put a reflective tape somewhere on the engine, didn't really say where, I'm guessing it's the flywheel. Most of them are very inexpensive, some were right around $100.
My guess is that Micron could come up with a quick an easy solution to check RPMs.

 

[krtrcn]

Im no software or computer guru, but if someone is that desperate to win, then they need to get their priorities straight.
I know that in my experience with having my engine rpms checked. My tach is disconnected from the sparkplug wire a the tech mans is put on. Once the engine is started the tech man revs it up not me.
If his tach reads above the set limit then Im DQ'ed. Its that simple.
So if I've tinkered with my tach it's taken out of the process, then why mess with it.

Jmo

 

[Slick27]

That's just one reason I stay away from the stock appearing class......cough cough I mean Predator classes

 

[flattop1]

Im no software or computer guru, but if someone is that desperate to win, then they need to get their priorities straight.
I know that in my experience with having my engine rpms checked. My tach is disconnected from the sparkplug wire a the tech mans is put on. Once the engine is started the tech man revs it up not me.
If his tach reads above the set limit then Im DQ'ed. Its that simple.
So if I've tinkered with my tach it's taken out of the process, then why mess with it.

Jmo

This seems pretty simple . It would add a little time and trouble at the scales though .