I'm doing my first install of the Racepak and I've got a question about clutch slip sensor placement. The clutch side is pretty straight forward my question is:
Is it better to have the output or wheel slip sensor mounted at the motor sprocket or at the actual wheel sprocket
Most of us read off the engine output sprocket, John at PMFR can set you up with the proper mounting bracketand collar.
We read are''s off of the back wheel. We put the magnet's in the rear rotor.(4 of them)
Thanks , I've got little room in the front sprocket area ( chain drive conversion on Vmax ) and was looking at the flat face of the Sertco sprocket at the rear. Tony is the reason for 4 magnets instead of 2 because of the larger diameter the magnets are at
It doesn't really matter where you put the magnets, with the RacePak DataLink software you can always make anything you want from it. Though I rather have it on the outputshaft of the gearbox, as it does more revolutions, thus giving more accurate reading at the start.
That's also the reason you want more magnets, again more accurate reading at the start. It isn't really a problem with egine RPM, as the engine is already running. It is a problem with axles which do not rotate at the beginning of the run, like clutch-out/gearbox-inand gearbox-out/Rear wheel. The same for front wheel.
If you "only" have two magnets, in the worse case you almost need a full revolution before it can determine the RPM, and this is the avarage RPM of the period of time it needed to measure it. The actual RPM is a lot higher at that moment in time. Therefore we use 6 magnets on the output shaft of the gearbox. With the almost 2:1 final drive ratio we can accuratly measure the first 60degrees worse case (30 degrees best case) on the rear wheel, which translates in a little over 16" (8" best case).
To put it into perspective, if we had 2 magnets on the rear wheel, it would have been a little over 97" worse case, which is thefull rollout of the 31" rear tire.
You might think: "What is 97 inch on a quarter mile". The thing is that it's the most important 97" of the run, which takes the longest.
In our case with a 31" tire and a 1.1 60ft time (a constant 3G pull),97" means:
A bit more than 4 tenths of a second into the run;
The bit where we go from 0 to almost 30MPH.
The part of the run where the wheelspin started.
It's perfectly clear to me now.
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