I am offering a new IGNITION TACH FILTER for those customers who desire to take the DIY path to installing GM EFI on their vehicle. There are two significant obstacles to installing GM EFI (and making it work properly by the way) on any given engine. The main issue is being able to re-calibrate the chip inside the ECM for the new engine. This issue is handled by my GM EFI DIY Tuning Guide found in another link on this site. But another technical challenge is getting an RPM signal into the ECM when your distributor is not directly compatible with GM EFI. As my DIY guide explains on my site, GM EFI systems require a distributor with a magnetic pickup to be directly compatible. All GM HEI distributors from 1975 to 1995 are directly compatible and allow the ECM to control ignition timing. Some Ford, AMC, and Chrysler distributors are compatible as well. But many older engines with points type distributors and those with Pertronix ingnitors are not compatible, THAT IS UNTIL NOW.
I have designed and am now offering for sale an IGNITION TACH FILTER for GM EFI systems. This electronic circuit is a noise filter and conditioning circuit that converts the 12 volt pulse at the ignition coil negative terminal into a 5 volt square wave signal with the same frequency as the engine RPM. This circuit is needed because connecting the ECM RPM Reference High wire directly to the ignition coil negative terminal will cause the ECM to be over-driven due to noise and the high voltage. When the ECM is over-driven it registers over 6000 RPM at all times, even at idle. Obviously, the engine will not run under these circumstances. The IGNITION TACH FILTER is required when connecting a GM ECM to any early model points distributors or those with similar electrical characteristics. In laymans terms this circuit will allow you to run a GM EFI system on a Ford Model T or any other pre-1970 engine.
The IGNITION TACH FILTER is an electronic circuit board with 5 wires. The 5 wires are connected to 1) the ECM Reference High pin, 2) the ECM Reference Low pin, 3) the ignition coil negative terminal, 4) a 5 volt power source (MAP sensor 5 volt reference works fine), and 5) an engine ground. The circuit board is enclosed and sealed in a steel housing for protection from physical damage and for electrical noise shielding. The steel housing has a 3/8" hole for bolting it to the engine block in proximty to the distributor.
The downside to using this IGNITION TACH FILTER is that you can't control the ignition timing with the ECM. My DIY guides on this site explain how to achieve timing control on older engines. The gist of it is you have to convert your distributor to a magnetic pickup.
The IGNITION TACH FILTER is now available for $50 plus $11.95 for flat rate US Priority Mail shipping in the USA. Non-USA purchases will require extra shipping. Email me for the cost. To purchase an IGNITION TACH FILTER send a $61.95 check or US post office money order to:
Customefis
PO Box 804
Hamilton, GA 31811
To order an IGNITION TACH FILTER by credit card click on the Buy Now button below. Click on the button to order an IGNITION TACH FILTER only. Other products are ordered elsewhere on this site.
If you found this IGNITION TACH FILTER on Ebay and want to purchase one, DO NOT click on the Ebay BUY IT NOW auction. Instead click on the BUY NOW button on this page and save $5. Ebay charges a final value fee on each item sold so I have to pass that fee on to the customer. Again, DO NOT CLICK ON THE EBAY BUY IT NOW AUCTION IF YOU WANT TO SAVE $5.
Be sure to include your return mailing address with the payment or email me with that information.
As I mentioned above, all DIY information regarding GM EFI systems is located in a password protected section of my website. Once you have purchased my DIY GM EFI Tuning Guide email me for the password to the hardware information.
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