advice on rev counter

[wurzelgummage]

hi - i had a pug 106 cup car with an E48. the car was crashed but running when i bought it so i reshelled it to non gti body that i already had (now starting and running again). i destroyed the gti dash like a moron by shorting out different inputs in an experiment and now i want to put an after market rev counter and temp indication in the car - i'll use the old standard analog dash from the 2nd car to give me oil light and battery light. anyway my knowledge of automotive electronics is pretty limited and i want to know what aftermarket tacho i can use to take a signal directly from the e48? - i know the gti digital dash had been driven from that pin. all of the aftermarket examples on ebay carry cavets about what it will and will not work on - any simple plug and play advice appreciated

[stevieturbo]

I'd imagine there are very very few aftermarket rev counters that would not work from the DTA's output.

[wurzelgummage]

thanks stevie - could you enlighten me as to what the tacho o/p signal actually is? is it pulses which are counted by the guage? or is it voltage proportional to speed? or is it some kind of modulating frequency that is translated by the guage?

[Rob Stevens]

It's pulses the rev counter counts, some time ago Allan made a software change so you could use an 8 cylinder engine on a 4 cylinder rev-counter (or whatever). This is software selectable in 'general engine settings' however if your E48 is very old it may not have this facility, check before buying a rev-counter that can't do this its self. Check the E48 by conecting to PC and checking that this function is not greyed out.