Tachometer Inaccuracy, anybody else?

[Onizuka]

He guys, I was on a dyno again this weekend and it has confermed my suspicions that arose the last time I was on the dyno. My tachometer reads higher than actual engine RPMS. Both my greddy emanage and the dyno software conferms this. around 7850-7900rpms on the tach equals about 7500 actual engine rpms. The percentage differense is accrose the board too. If the tach reads around 900rpms at idle its really at about 825rpms.

Has anyone else noticed this inaccuracy while using the 91-94 tach with a s13 sr?

[ETTInnov04]

Factory tachs are not necessarily the most accurate. I know my friends MKIII supra is like this, his SAFC reads lower than the tach does. By no means am I suggesting you go buy one of really cool and crazy 5" tachs... Just saying that it is not just an issue to the KA tach with SR

[Onizuka]

Well Ive been thinking it might be because of minute differences in electronics between the KA and SR tach. Each are calibrated for their own circuts and respective motors, small resistence changes could effect their accuracy.

Does anybody with the 9000rpm(7500rpm redline) SR tach still have the same problems?

[own3d]

its a fact that most car manufactures stock tach's are off. hell in my 626 it had a fuel cut at 7,600rpms and i could peg the tach at 8,000 for almost a second in first gear before itd cut out.

[Luke]

I remembe reading an article about factory tach's being very inaccurate. They used the example with a mustang where they would rev the engine and the needle would be so slow that when they lifted the throttle, the tach was still moving up the rpms.

Although, i don't seem to have any inaccuracy issues with my 93 DOHC tach. I don't have any other electronics to completely confirm that, but I have hit the rev limit and it was around the 7500 range.

[ibzbro]

you need to use the sr tach. the ka tach reads a different signal. the same is ture when using a ka sohc tach with a dohc engine, the numbers won't be right.

[TougeTune180]

would the same go for the tach completely not working? my 91 tach doesnt want to work at all, except spmetimes when i twist the key to start it will bounce like twice, then freeze again. any ideas?

[S13240]

From what I remember a while back on FA, after 3500 rpms or something on the 91-94 tach, it gets very inaccurate.

[NY S13 SR]

I have the Apexi Rev Speed meter and the Super AFC, they both read lower than the SR tach swapped into the dash. They read the same, only the dash tach is different. I'll have to compare on the dyno which is correct, didn't remember to check last time.

______________________Jeff Hheavythrottle.com