Tremec Speedo Sender unit pulses

[Grease Monkey]

OK, so i've got the sender unit in and the speedo's showing around 10% too high (i think) with a setup of 8009 pulses per mile, so lets say it should be around 8500 ppm.

Working backwards I measured my tyre at 2.05m circumferance. A mile is 1609 metres, so i need 784.9 revs at the wheel per mile.

OK, now my Diff is 3.54:1 so i need 2778.5 revs at the propshaft per mile.

Assuming the sender gives one rev per rev of the propshaft and that my guess of 8500 is correct, this means the sender gives 3.06 pulses per revolution, which sounds a bit odd.

Anyone know how many pulses the tremec sender is supposed to give per rev of the prop?
(I'm running standard 245/45ZR17s through a 3.54 diff via a TKO3550)

[andywsussex]

Adrian,

Don't know for sure what a Tremec's supposed to do, but alot of senders that rely on an induced pulse (such as Dax's for the Smiths speedo) seem to expect the passing of 4 prop bolts per shaft revolution. The problem with this is that they seem to lead to an instability at speed (as Dave B's said before and I've found out - I'm now planning on installing my own tags for only 2 pulses per rev) - something to do with op-amp saturation I'd guess. It could be that Tremec have used 3 permanent magnets to overcome this. And the .06 is the inaccuracy because 8500 isn't exact?

Are you on Toyo T1-S's? If so, I know it'll depend on tire pressure, etc., but Toyo's site gives figure for revs/mile to save you working it out - 809.
http://www.toyo.co.uk/index.php?fuseaction=car.t1-s

Andy

[Grease Monkey]

They're Toyo T1-R but i guess they're the same circumferance.

OK so based on 809 r/mile thats 2863 r/mile at the prop, assuming 3 pulses per rev thats 8591 pulses per mile.

May well go with that for Thursday, guess i can bugger about with it on the day if required.