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My friend swears his factory Tach is accurate. I told him my 89lx was 1k rpms off @6000rpms according to the dyno and my PMS.

So how accurate is your Tach?

Mike
 

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I use an autometer shiftlite, and the factory tach hits perfectly at the RPM the shiftlite is supposed to turn on. So I know it's accurate(at least mine is) up to 5400 rpm.
 

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It probably is accurate or close at a steady rpm, but it cannot handle quick movements whether they are accelerating or dropping (like on a slow, high rpm shift)

When i had a shfit light at 5200, I saw anywhere from 4800-5200 on the tach. at a 5400 light, I saw anywhere from 5000 to 5500. Sometimes was accurate, often was not.

Mine is dead on at idle and probably at cruise, etc. ut certainly way far off when accelerating.

Your friend is risking some bad damage trusting the factory tach.
 

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When I go racing, the Autometer Monster tach vs. the stock tach reading can vary as much as 600 rpm on my car after 5000. Also, at idle, every now and then I'll show a 50-350 rpm difference, though that seldom happens.
 

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On the Dynojet, mine was off 100rpm at 2000 and 150 rpm at 6000rpm. I don't know about how quickly it reacted in between.
 

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Had an Autometer tach in for awhile. Didnt need it. Sold it. Factory tach in my car was right on or within 100 rpm. I drag race a ton, and really didnt need the extra tach. I dont use a shift light as I vary my shift points in the higher gears. ;)
 

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My best friend is an electronic engineer and actually designs tachs where he works. Most tachs are +/- 3%. Or no more than 1 pointer width off (about 100 rpms). Its less accurate at low and high RPM's. I had several of his tachs in my car and my stock unit is fairly accurate. I do suggest a good tach if you drag race alot.
 

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Re: How accurate is the factory 95 Tach?

mike89lx said:
My friend swears his factory Tach is accurate. I told him my 89lx was 1k rpms off @6000rpms according to the dyno and my PMS.

So how accurate is your Tach?

Mike
So who's your friend Mike?
 
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