I just put a used gauge cluster out of a Si/Ex civic into my 95 CX civic hatchback. After driving it for a day the speedometer seems to be correct but I am not sure about the tachometer. After the car is warmed up it idles at around 800-900 rpm and when I am driving I seem to be shifting at around 3000 to 3500 rpm. I also took note that going around 35 in third gear on a level road that my rpms were 2000. I don't know much about cars but when the red line is at (I think 7000) and the most I dared rev the engine (based on sound) before shifting was around 4500, and like I said usually shifted at 3500, something doesn't quite seem right but maybe I am just wrong.

More information about my car:
The most stripped down model you can get (ie no power lock, windows, A/C)
The previous owner I highly doubt did any modifications to the car (she was an old lady) the one owner before her I am not sure but don't think there were any modifications done to the engine.
Engine: 1.5L 70hp with 170000 miles.
Engine was in good condition when bought at 155000 (previous owner had kept receipts of regular maintenance) and mechanic verified good condition.

So basicly is the tachometer reading the rpms correctly?

 

an Si cluster is way off isn't it? you have a 1.5 SOHC non-vtec... and i'm unsure... but don't those two motors have totally different RPM ranges?

 

Yea, there like day and night.

 

that's what i thought. so most likely, your Si gauge cluster is nowere near accurate. i mean, my sol's 1.5L redlines @ like 6400 rpm. i believe the Si motor that year redlined @ like 8000 even. i think that's right, not sure. anyway, hit a junk yard and get the correct gauges, or @ least a tach. see if that helps i guess.

 

factory tach is usually good + 200 RPM and gets worse the higher the RPM... 6000 and up if i remember correctly. as far as the accuracy goes, your tach looks to be ok with the numbers you're giving for shifting and 3rd gear rpm at 35mph. thought the tach is marked for a different motor, the RPM readings should still be accurate.

 

i would figure 5000 rpms' on one motor, is still going to be 5000 rpm's on another motor...as long as the guage plugs in and works, they should read the same RPM's...no matter what the motor.