Stock tack off 500prm!!
Thread Starter
Team Owner
Joined: Mar 2001
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From: Boston, Dallas, Detroit, SoCal, back to Boston MA
Stock tack off 500prm!!
Had the car dynoed Saturday.
When compared to the dyno's It was off 500rpm :mad
I had to "bury it" to get it on the rev limited.
Stock tack showed 6500, I think, the scale only goes to 6000 :nono:
Time to get an aftermarket tach w/ shift light, and mount it directly in front of the stock POS! :smash:
When compared to the dyno's It was off 500rpm :mad
I had to "bury it" to get it on the rev limited.
Stock tack showed 6500, I think, the scale only goes to 6000 :nono:
Time to get an aftermarket tach w/ shift light, and mount it directly in front of the stock POS! :smash:
Race Director
Joined: May 2001
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Re: Stock tack off 500prm!! (BrianCunningham)
You know a friend of mine says the same thing, but here's the deal. If you know the tach is off by 500 then just adjust your shifting accordingly. In my case the tach needle is just about to touch the vertical trim between the tach and the speedo when it hits the rev limiter. I know that so I shift just before that. It's not like it's gonna be off 500 one day and 100 the next.
Anyway, I have thought about the shift light, hidden in the A/C vent. As far as an aftermarket tach, it's not worth butchering the inside of the car IMHO.
Anyway, I have thought about the shift light, hidden in the A/C vent. As far as an aftermarket tach, it's not worth butchering the inside of the car IMHO.
Burning Brakes
Joined: Aug 2000
Posts: 984
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From: Cincinnati OH
Re: Stock tack off 500prm!! (BrianCunningham)
I wonder if you could just remove the needle and reposition it so that it reads accurately at redline. I seem to remember watching one of those tnn gearhead shows where they replaced a gauge panel with a different color one and they just marked all the needle positions, removed the needles, replaced the "paper" panel and put the needles back on, so it seems like it should be doable.
Team Owner
Joined: Aug 2000
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From: San Pedro CA
Re: Stock tack off 500prm!! (Vince Ivanc)
nice idea, but I don't think it will work... the tachs, like speedometers, are showing error with GREATER speed, not less.
my tach is accurate at 2500 for emission tests, but I have no idea if it is accurate at redline...
my tach is accurate at 2500 for emission tests, but I have no idea if it is accurate at redline...
Melting Slicks
Joined: May 2000
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From: Andersonville TN
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Re: Stock tack off 500prm!! (bogus)
Strangely, many C4's experience a progressive drift in the tach getting off. I think it has to do with a resistor cooking and losing its resistance. It conditions the signal. Do a seach on tachs, and there was a long post a while back.
Lee
Lee
Drifting
Joined: Nov 1999
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From: St. Paul MN
Re: Stock tack off 500prm!! (bogus)
I have the way-cool digital dash. I just put in a MSD Digital6 Plus ignition. I set the rev limiter to 5500 to start out with. The dash only shows 5000 when the rev limiter cuts in. I would tend to think the MSD box is correct and the engine is at 5500. So I'm thinking that's about how far off my tach is. I did just buy a scan tool so I can check it with that also but my car is tucked in now for the long winter sleep, bummer.
Drifting
Joined: Jul 2001
Posts: 1,896
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From: New Bern NC
Re: Stock tack off 500prm!! (BrianCunningham)
I have a new Auto-Meter tach on the 95 and it shows 200 rpm lower than the factory tach. Now, I don't know whick one to trust. I may send in the Auto-Meter for a calibration check. Sid.
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Team Owner
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From: SE NY
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Re: Stock tack off 500prm!! (Bob86ZZ4)
The ECM is only counting pulse rate from the dist so I'm confused at why our tachs are off.
I could see how an analog Tach could read high but our digi dash tachs should only be off on the low side and then only if the ECM misses a pulse or two.
I've not seen the tach signal on a scope but would think the signal conditioner is only a (relatively) low pass circuit to remove any spikes. If it triggers off one plug it would be 50Hz at 6,000rpm and only 400Hz if it triggers off each plug fire.
Does anyone have a clue what's inside the conditioner module?
I like the idea of a shift light behind the A/C vent.
NOTE: My error Gordon says there are two pulses (a large and a small one) per fire so the max frequency is 800Hz at 6,000rpm.
[Modified by 65Z01, 8:11 PM 12/3/2001]
I could see how an analog Tach could read high but our digi dash tachs should only be off on the low side and then only if the ECM misses a pulse or two.
I've not seen the tach signal on a scope but would think the signal conditioner is only a (relatively) low pass circuit to remove any spikes. If it triggers off one plug it would be 50Hz at 6,000rpm and only 400Hz if it triggers off each plug fire.
Does anyone have a clue what's inside the conditioner module?
I like the idea of a shift light behind the A/C vent.
NOTE: My error Gordon says there are two pulses (a large and a small one) per fire so the max frequency is 800Hz at 6,000rpm.
[Modified by 65Z01, 8:11 PM 12/3/2001]
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Re: Stock tack off 500prm!! (65Z01)
My tach as well as Mackey's is off by at least 500. I shift when my tach is past 6,000 and the rev limiter hasn't kicked in yet.
Mackey has an aftermarket tach mounted to the steering column, no butchering needed, matter of fact, it looks like it belongs there. Don't have a pic.
Mackey has an aftermarket tach mounted to the steering column, no butchering needed, matter of fact, it looks like it belongs there. Don't have a pic.
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Re: Stock tack off 500prm!! (Mr Mojo)
My tach as well as Mackey's is off by at least 500. I shift when my tach is past 6,000 and the rev limiter hasn't kicked in yet.
Mackey has an aftermarket tach mounted to the steering column, no butchering needed, matter of fact, it looks like it belongs there. Don't have a pic.
Mackey has an aftermarket tach mounted to the steering column, no butchering needed, matter of fact, it looks like it belongs there. Don't have a pic.
Thread Starter
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From: Boston, Dallas, Detroit, SoCal, back to Boston MA
Re: Stock tack off 500prm!! (Mr Mojo)
Mackey has an aftermarket tach mounted to the steering column, no butchering needed, matter of fact, it looks like it belongs there. Don't have a pic.