So a couple months back when we tuned my R, we found that the tach wasn't reading the RPMs completely accurately. At idle the tach was off by 100-200rpm. I figured no big deal. Idle is set at 800rpm and the tach usually reads at 900rpm. At higher rpms, however, the difference gets a hell of a lot bigger. So much that the tach reads that my VTEC engagement is anywhere between 7800-8100rpm. We set engagement at 7400rpm (best power, weird huh). Well in summary, thanks to this little issue, I can't fully trust my tach towards the redline (just a tad over 9,000rpm).

Is there any easy way to fix this? Or am I stuck buying a new gauge cluster?

 

The factory tach is more of a suggestion that an absolute. I forget what the error is, but yours may be within reason.

 

Ya I heard that factory ITR tachs do this quite often. Still doesn't make this less annoying. I don't really care to bounce off my rev limiter every time I want full power though...

 

http://pivotjp.com/product/sg/...6.wmv

right click save as.

 

^^^ WTF, I've never seen one that far off.

factory tachs are never exact, and the quality of parts in them... well it's a wonder they are as close as they are.
the best way to get it more accurate is to pull the needle with some serious electronic equipment (waveform generator and o-scope) and reinsert the needle where it should be.
All though it will only be accurate at that RPM, anything up or down from there will be a % off like usual.

I did this to mine a while back, 5k was the target, idle and redline are closer than I can see at a glance.
Shift lights work better than the tach anyway.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DejaVu88 &raquo;</TD></TR><TR><TD CLASS="quote">I don't really care to bounce off my rev limiter every time I want full power though...</TD></TR></TABLE>

If the tach is optimistic (i.e., reading higher than the actual revs), how would you accidentally hit the limiter?

Your easiest solution would be to determine the error at redline, and learn to adapt to it.

 

This is why you run a giant autometer tach.

 

about 400 RPM's on the high side for most Honda's

 

Or the Brockway Engineering R290 Data logger, I've had this for a couple years now and just recently installed it and love it. Shows and records RPMS/MPH/Engine Temps/Exhaust Temps/AF Ratio/Timing, and quite a few other things, it's pretty nifty, also has it where it reads everything metrically...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">

If the tach is optimistic (i.e., reading higher than the actual revs), how would you accidentally hit the limiter?

Your easiest solution would be to determine the error at redline, and learn to adapt to it. </TD></TR></TABLE>

If I was going for full power, and the difference between the tach. and actual RPMs is sporadic at higher RPMs, then I still don't know when to shift. If I shift at say, 9,300rpm according to the tach, but the difference in that particular situation is 600rpm, then I'm shifting 300rpm shy of the redline (which was originally 9,300rpm in the first place). If I am going for max power, I want to squeeze every bit out, don't ya think? So if that difference is smaller, and I go higher on the next run, that'd leave me bouncing off the rev-limiter.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DejaVu88 &raquo;</TD></TR><TR><TD CLASS="quote">

If I was going for full power, and the difference between the tach. and actual RPMs is sporadic at higher RPMs, then I still don't know when to shift. If I shift at say, 9,300rpm according to the tach, but the difference in that particular situation is 600rpm, then I'm shifting 300rpm shy of the redline (which was originally 9,300rpm in the first place). If I am going for max power, I want to squeeze every bit out, don't ya think? So if that difference is smaller, and I go higher on the next run, that'd leave me bouncing off the rev-limiter. </TD></TR></TABLE>

Go aftermarket then. I don't think there's any way to calibrate the stock tach.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DejaVu88 &raquo;</TD></TR><TR><TD CLASS="quote">If I was going for full power, and the difference between the tach. and actual RPMs is sporadic at higher RPMs, then I still don't know when to shift. If I shift at say, 9,300rpm according to the tach, but the difference in that particular situation is 600rpm, then I'm shifting 300rpm shy of the redline (which was originally 9,300rpm in the first place). If I am going for max power, I want to squeeze every bit out, don't ya think? So if that difference is smaller, and I go higher on the next run, that'd leave me bouncing off the rev-limiter. </TD></TR></TABLE>

The difference generally won't vary much, if any. If it's optimistic by 500 RPM at redline, it will normally be 500 RPM each time. I assume by your mention of "runs" that you're referring to drag racing, in which case a large aftermarket tach (perhaps with a shiftlight) would be your best bet, as others have already suggested.

 

Yeah it seems that is my option if I want to get solid figures. I just hate polluting my interior with gauges, and I love staring at that gauge cluster so much. O well, I guess I'll have to break down before my next outing to the strip.