Tachometer Filter Question
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Advanced
Joined: Jul 2004
Posts: 95
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From: Ontario
Tachometer Filter Question
I am hooking up a 75 tachometer to my HEI system. I have read that you need to have a tach filter installed to protect spikes to the tachometer. Can someone tell me what this filter looks like and do I really need it? If I do need it, how do I install it?
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
A tach filter is "installed between the Tachometer and the Ignition Trigger Source (usually the coil) this filter traps, redirects, and dissipates the high voltage spikes and surges that are emitted by any late-model high-energy ignition system. Also modifies the sharp up-and-down spikes into a semi-square wave signal for steady pointer readings and faster pointer response."
Here's what is looks like and where to buy one (among several online stores):
Tach filter at Ecklers
Here's one that looks more like the original and for less $$:
Tach filter at eGauges.com
Check some of the other CF supporting members. I'm sure several carry them.
I've read reports of the tach acting crazy without one.
Here's what is looks like and where to buy one (among several online stores):
Tach filter at Ecklers
Here's one that looks more like the original and for less $$:
Tach filter at eGauges.com
Check some of the other CF supporting members. I'm sure several carry them.
I've read reports of the tach acting crazy without one.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
A tach filter is "installed between the Tachometer and the Ignition Trigger Source (usually the coil) this filter traps, redirects, and dissipates the high voltage spikes and surges that are emitted by any late-model high-energy ignition system. Also modifies the sharp up-and-down spikes into a semi-square wave signal for steady pointer readings and faster pointer response."
Here's what is looks like and where to buy one (among several online stores):
Tach filter at Ecklers
Here's one that looks more like the original and for less $$:
Tach filter at eGauges.com
Check some of the other CF supporting members. I'm sure several carry them.
I've read reports of the tach acting crazy without one.
Here's what is looks like and where to buy one (among several online stores):
Tach filter at Ecklers
Here's one that looks more like the original and for less $$:
Tach filter at eGauges.com
Check some of the other CF supporting members. I'm sure several carry them.
I've read reports of the tach acting crazy without one.
and yes without it, you are going to get silly readings...
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
I ran without one for a while because I couldn't find one. (That was about 8 years ago.) I noticed the needle wasn't as steady as tachs on my other vehicles, but that's not why I put one back on. A C3 owner at a local Corvette show thought that not having one could affect the printed circuit board in the dash, but he didn't know for sure. I still don't know if the printed circuit has anything to do with the tach, but I certainly didn't want another problem on top of the hundreds I didn't expect in the first place. I noticed, however, that the tach is very steady with a filter in the circuit.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,847
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The reproduction tach filter is listed in the forum special section of our site at this link.
http://willcoxcorvette.com/product_i...ducts_id=26320
You can run the tach without the filter, but you are also susceptible to interference from HEI and the square signal.
If you want to see an original filter, I just posted a video above and I actually had one sitting on the bench and held it up.. pretty clear view.
Willcox Inc.
http://willcoxcorvette.com/product_i...ducts_id=26320
You can run the tach without the filter, but you are also susceptible to interference from HEI and the square signal.
If you want to see an original filter, I just posted a video above and I actually had one sitting on the bench and held it up.. pretty clear view.
Willcox Inc.
Advanced
Joined: Mar 2006
Posts: 52
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I replaced the filter on my 1979 works well. I replaced the Ignition system to a MSD. Do not need it any more. It is disconnected and still on the Intake. Send me your address and I will send it to you. If it dose not work you are out nothing. It will just endup in the trash, otherwise. cleonwingard@hotmail.com
