Tach Signal Masking

[BottleFed70]

Been having some tach signal noise/dropout problems with EDIS and it was mentioned that adjusting the tach signal masking settings might help. So, I'm trying to come up with some target numbers.

The way I understand EDIS; the EDIS module sends the PIP signal with the same frequency as each ignition event.

On a V8 with a redline of 6500RPM, that should make a maximum of 26,000 (8 x 3250) ignition events per minute.
26,000 ignition events per minute = 433 ignition events per second
433 ignition events per second = 2.3Milliseconds between ignition events

So theoretically, I should be able to set my tach signal mask as high as 2.2 milliseconds?
Could someone verify if my math and theory are correct?

Thanks!

[BottleFed70]

Turns out 2.3ms is way too high for a V8 using EDIS. Starting ignoring legitimate RPM pulses at around 3300RPM. Looks like my math was wrong somewhere and I doubled the time window. Setting it at 1.1ms seemed to let it rev right up to 6000RPM+

[David_S]

To configure Code 2.89 with MT 2.25p3 I am just going through the same exercise as you but with a 6 cyl (max rpm around 4,000) .

Using your calc methods my tach signal mask could be set up to 5mSec, or 2.5 if I halve it.

Have you "corrected" your maths? If the tach signal from the EDIS module is true RPM and the ignition correction is done by the EDIS module on receipt of the timing info from MS then this would account for your double value.

Or am I off-beam again?

David

[BottleFed70]

Well, the math I did in my 1st post is definite wrong. I'm not sure why tho.
Seems to get a correct number, you would want to use 1/2 of the value that my math comes up with. Maybe because it's a square wave or something and the MSII needs to see both the rising and falling edge?