Tachometer

[Randy Van der Ree]

Hey guys, does anyone knows whats the relationship between electrical frequency of the tachometer output ( GSXR-600) and RPM ??

[Randy Van der Ree]

Hey guys, does anyone knows whats the relationship between electrical frequency of the tachometer output ( GSXR-600) and RPM ??

[Ben Beacock]

the tach output runs at half the frequency of the engine RPM. (if that makes sense)

[Randy Van der Ree]

1 RPM = 1/2 Hz?

[B Lewis @ PE Engine Management]

Normally for a 4-cylinder the tach expects a signal that occurs twice per rev. Typically the tach signal follows the number of ignition events per revolution. For an 8 cylinder it would be 4 pules per rev. I don't know if that is the case for the GSXR, but other bikes are like that.

[Evan]

We use an R6 engine, and it's the same for us, but it's 1 RPS = 1/2 Hz, not 1 RPM. That would mean that 1 RPM = 0.00833 Hz. Assuming the systems are the same with the two engines, the reason that this relationship exists is because it takes it's signal off of just one cylinder's coil circuit, which only fires every other rotation.
-Evan Martin
Ryerson FSAE

[Randy Van der Ree]

Now we have a discordance, because, if the tach acts like brian says, 1 rev -> 2 pulses at the output. 1rps = 2Hz.... 1rpm=0,03333Hz

[Evan]

Yes that is true, there is a disparity. I don't know why such is the case, but I do know that our tach signal is as described. One sure way to know is that if we hook up to an inductor coil to a single plug (tricky with the coil on plug setup, but we have done it when trying different things), the signal ends up the same, and such a setup could only result in the output that I said we were getting. One nice thing to note about taking it off of one cylinder is that the calibration is defined by the fact that it's 4 stroke, not the number of cylinders the engine has, assuming there aren't any doubled plugs on a single coil as is popular with some V-6 setups. But all that has nothing to do with fsae. Also, of course the resolution of the tach is worse than if more samples were taken, but it doesn't seem to be a factor.
-Evan Martin
Ryerson FSAE

[Randy Van der Ree]

The Real fact now, is if we have two pulses per revolution. or a pulse every two revolutions.
and then we will know if the frequency of the tach would double the rps or would be the the half.
Evan I don´t see how can I prove this fact, on the way that you are describing it.

One sure way to know is that if we hook up to an inductor coil to a single plug (tricky with the coil on plug setup, but we have done it when trying different things), the signal ends up the same

[Ali]

Hi,

We used a GXSR-600 for our 2004 car. There's a tach signal wire from the stock ecu that feeds the gixxer's orig dash tachometer. I took a reading using an oscilloscope: RPM = Signal freq * 60 i.e. at 10K rpm, Signal freq= 10000/60=166.67Hz. We compared it with an actual tach reading from our power commmander software (which gives actual tacho numbers)

Regards,
Ali, National University of S'pore FSAE 2004

[Evan]

Randy;

Sure, that method proves it. We know that the plug fires only once per cycle on the R6 engine, and therefore there is only current going to the plug once every 4 strokes, or every two rotations. The signal we get off an inductor coil allows the tach to function in the same manner (ie calibrated), as the signal from the ecu. Therefore, both signals must be the same; 1rps = 1/2 Hz. Granted this isn't a good way to calibrate the tach, as it is a little backwards, we just stumbled upon it whilst trying a few different things. We also used an oscilloscope to find out the right way later. Hope that explanation helps with what I was trying to say.
Finally, our problem here is a huge magnitude off, so try it the one way, and if your engine redlines at 6000 indicated rpm, you know somethings up... as would a redline of 24,000 rpm, if it's the other way around.
-Evan

[techneaz]

hi,
can any one tell me wat is the output from the tach lead comin out of the stock ecu of a honda cbr f4i 600cc? is it by any chance 5 v square wave pulse.

[techneaz]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ali:
Hi,

We used a GXSR-600 for our 2004 car. There's a tach signal wire from the stock ecu that feeds the gixxer's orig dash tachometer. I took a reading using an oscilloscope: RPM = Signal freq * 60 i.e. at 10K rpm, Signal freq= 10000/60=166.67Hz. We compared it with an actual tach reading from our power commmander software (which gives actual tacho numbers)

Regards,
Ali, National University of S'pore FSAE 2004 </div></BLOCKQUOTE>



hi ali,
can u tell me wat output does the tach output lead from the ecu give? cos people told me it will be 5v square wave output. is it true? i cant test it with our engine cos its will take few more weeks to start it

waitin for ur reply