Silvia Club of NSW

Heya,

I was playing with the sil on the weekend and noticed that my tacho and power fc rpm (fc commander) tell me 2 different things. The tacho seems to be reading high or the power fc low, not really sure which to believe. My Bee-R is set at 7000 - 7100 RPM, well that’s what the tachpo says anyway. I checked my fc handset and it says I only hit 6500 rpm.

I am not sure which one to believe as if my tacho is wrong then I will be missing out on 500 rpm of my power band. Is there anyway I can test what it really is?

It is an S13 which was originally a CA18DET which was converted over to SR20DET. Dunno if this makes a difference.

Any help would be greatly appreciated.

Cheers
Kirk

you could turn the bee*r off....they eat SRs for breakfast anyway.


chances are the tacho will be out, and the PFC reading good.

from experience most factory tachos and speedos aren't calibrated very well.

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formerly 3AM

Yep,

Trust the pfc over the factory tacho any day.

I have a pivot stepper motor tacho with inbuilt shift light and it's spot on with the pfc rpm.

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meh

Yeah I know the bee-r isnt that good on engines but I tend to hit the limiter a lot, so I figured it would be better than the limiter on the power fc which I believe is a fuel cut, I just don’t want to lean out at the limit due to this and blow a ring land or ring

if you had a CA or RB maybe. but on an SR, the PFC limiter is definetly safer. even tho its a fuel cut,

The problem with the Bee*R and SRs is due to the rocker setup, and the fact the Bee*r does not know crank position, the Bee*R can force the valve off its seat, you can get a gap between the rocker and top of the valve = smashed rocker arm or broken valves...

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formerly 3AM

Back to the tacho thing....

both are receiving a 'digital' pulse....

the PFC counts and then displays the readout... very accurate because its digital - digital!!!

whereas the dash tacho has to average the pulses in order to convert them to an analogue readout..... Not very accurate because you are converting digital to analogue

also the dash tacho is a 'moving coil meter' which are very hard to get accurate unless you have limitless cash to purchase stepper motors as mentioned before...

Hope this helps

Cam.

Cool, so they are both getting their information from the same place....hmm, well I guess I should change my shift light to suit the real rpm level then too.

Thanks fellas

The PFC is what is actually driving the engine, so it knows the exact rpm.

The factory tacho is an electromechanical, analogue gauge that's pushing 20 years old.

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The Engine Whisperer - fixer of things