What is your rpm @ 70 80 in 5th gear = for gsr
How high does 2nd gear go ? i believe mine is 68 - im just suspicious

at 70 im at 3700 - nearing 4k at 80

this accurate?

<U>UPDATE AT THE BOTTOM - plz look if you know how to readjust tach</U>


Modified by Chemicalviper at 1:17 AM 10/21/2003

 

my tac in my cluster is 300 rpm higher than what my Field vtec controller says. (which is right).

 

thanks that helps me so much lol

 

Every tach is different.

 

This is somewhat of a redundant question -- the speedo that you are using as a "yardstick" for measuring the accuracy of the tach is MUCH less accurate (and influenced by a greater number of factors) than the tach itself.

Maybe you should be asking if the speedo is accurate according to your engine rpm.

Either way, the numbers that you have given seem to be about right.

 

Here is the rpm vs speed equation I figured out -- using this, you will be able to figure out your top speed in any gear, speed at a given rpm in any gear, etc..

speed x wheel revs per mile = (rpm x 60)/(gear ratio x final drive)

 

<U>UPDATE</U>

My tach gets gradually off - less than 100 at idle - but at redline its almost off by 400 by 8200 rpm - Is there anyway to fix it ? Maybe with the screw holding the needle in at the back of the cluster?

By the way i figured out its accuracy with my VAFC.

 

bump

 

well it also depends on your tranny also. gsr tranny - 5th gear - 80mph should be on 4000k....like dead on

 

nah man ya didnt read hehe - at 70mph ... my tach shows 3700rpm ... but the vafc shows true rpm is 3500 .....

My question is how to readjust it so its back to normal. Nothing to do with tranny I BELIEVE - its the needle.

 

oh ok im sorry...didnt read on me

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by greebler &raquo;</TD></TR><TR><TD CLASS="quote">my tac in my cluster is 300 rpm higher than what my Field vtec controller says. (which is right).</TD></TR></TABLE>I got my guage the tach and vafc and they are not all the same You think if I put my autometer tach to my msd box it would get a more accurate signal?

 

OEM tachometer is never accurate. I wouldn't worry about it that much.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by greebler &raquo;</TD></TR><TR><TD CLASS="quote">my tac in my cluster is 300 rpm higher than what my Field vtec controller says. (which is right).</TD></TR></TABLE>

same.

you find out when you are on the dyno. But lots of things can varry the OE tach which is usally slow from the factory in the first place.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chemicalviper &raquo;</TD></TR><TR><TD CLASS="quote">= for gsr How high does 2nd gear go ? i believe mine is 68 - im just suspicious</TD></TR></TABLE>

if you are getting up to 68 in 2nd gear then you are revving almost to 9 k. There is a speed/RPM calculator on http://www.car-videos.com at 8200RPM a gsr will hit 64mph in 2nd gear.

 

so there is no way to readjust needle?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chemicalviper &raquo;</TD></TR><TR><TD CLASS="quote">so there is no way to readjust needle?</TD></TR></TABLE>

Nope.
The oem tach is only capable of going so fast in it's closed loop setup. Light mods, lightened flywheels, etc are all enough to throw it off.

If you're worried about it, do what I did.
Buy a small 4" 10k rpm tach from autometer, or wherever and mount it to your steering column. It works like a charm, and allows you to get a true tach reading, and not one that's 400rpm late.

 

if your tach is 400rpm's off, then when you shift at the redline on the oe tach, dosen't the rev limiter kick in before you even get to the 8,200rpm mark on the oe tach? And isn't this a big deal? I know chemicalviper floated a valve from over reving, even though he was shifting at redline.

 

Bleh - only one way to figure out ... goto 8 grand and slowly rise rpms see if it does redline at 82 on tach but it hink its 78 on vafc - .... this will be fun ahh god.