tach
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Melting Slicks
Joined: Dec 2008
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From: Mystic CT
tach
Hi got the chip from Brian bate and tach works now. But how accurate or linear can be expcted from a l98 '91 tach?
Yes I adjusted the trim pot back and forth looking for a good compromise and thinking getting it good between idle and 3000 and worry less about above 5000 makes sense as the power will be gone by 5500 for sure.
Yes I adjusted the trim pot back and forth looking for a good compromise and thinking getting it good between idle and 3000 and worry less about above 5000 makes sense as the power will be gone by 5500 for sure.
Last edited by ddahlgren; Dec 26, 2017 at 03:25 PM.
Team Owner
Joined: Sep 2003
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Hi got the chip from Brian bate and tach works now. But how accurate or linear can be expcted from a l98 '91 tach?
Yes I adjusted the trim pot back and forth looking for a good compromise and thinking getting it good between idle and 3000 and worry less about above 5000 makes sense as the power will be gone by 5500 for sure.
Yes I adjusted the trim pot back and forth looking for a good compromise and thinking getting it good between idle and 3000 and worry less about above 5000 makes sense as the power will be gone by 5500 for sure.
You don't care where it parks with KEY-OFF - just @ 0 with KEY-ON NOT RUNNING!!
Thread Starter
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
It does the key on thing reading zero and not the question. The question is accuracy +- how many rpm?
Team Owner
Joined: Sep 2003
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Accuracy is going to be 'your' interpretation of what you see tach vs scanner or C68. Maybe you'll post back with 'your' interpretation so others could maybe compare!!! Scanner is much easier read for the RPM range you mention.
Your car, your tach & your repair - a WYSIWYG moment
Thread Starter
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
It is a hassle to assemble install run car and then remove disassemble tweak trim pot assemble install and run again if needed several times. The C68 last I looked gives a number that is multiplied by 400 to get RPM from my memory. That would indicate the C68 can only offer either +- 200 RPM or could be -399 +0 RPM or -0 +399 RPM. A scanner is much better as I am sure closer than that. I am going to use a function generator and high quality o'scope that will do Hz calculations internally to drive the tach and get the best fit curve. I need to sort out the oil temp sensor and ha to be wiring or sensor as the gauge in the cluster tested ok.
Team Owner
Joined: Sep 2003
Posts: 25,414
Likes: 2,745
It is a hassle to assemble install run car and then remove disassemble tweak trim pot assemble install and run again if needed several times. The C68 last I looked gives a number that is multiplied by 400 to get RPM from my memory. That would indicate the C68 can only offer either +- 200 RPM or could be -399 +0 RPM or -0 +399 RPM. A scanner is much better as I am sure closer than that. I am going to use a function generator and high quality o'scope that will do Hz calculations internally to drive the tach and get the best fit curve. I need to sort out the oil temp sensor and ha to be wiring or sensor as the gauge in the cluster tested ok.
Thread Starter
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
I did and he told me the trim pot may need adjustment to get it dialed in. There are other components on the board that could age and personally know an OEM tach is not all that accurate none of the gauges are from what I have seen.
