testing a tachometer for a 4cyl e30 on a 6cy

[irish44j]

Guy has a 318 tach that I want to buy to replace my broken one. He doesn't know if it works, since he got it mistakenly for his 325. If he plugs it into his car will it do ANYTHING? I know the rpm's would be off due to a different cylinder pulse rate, but in theory I would think that it would still read SOMETHING.

Anyone know if this is the case?

Or if there's another way he can test it?

[MR 325]

Yes, it should still give a reading. Just a totally wrong one.

[irish44j]

cool, that's what I needed to verify. Thanks.

[nando]

it will work fine if you have the correct coding plug. there's no physical or electronic difference between a 4 cyl or 6 cyl tach. that difference is in the coding plug itself. of course a 325 will have the wrong coding plug since that's a 7k tach and the eta comes with what, a 5.5k tach?

[bmwm42]

yup just switch coding plugs