Tachometer Conversion

[convert2diesel]

Dr. Lee:

Read your article regarding the conversion of a gasser tach to use the ESS on the 6.2. Have just recieved the prototype engine from Jamie for my Buick Roadmaster conversion and am wondering if your design would be applicable to the factory tach used in the early 90s GM cars. This would simplify my job no end.

Was even toying with the idea of using four magnets on the front damper and a magnetic switch to give me the four pulses per rev needed for the gasser tach. If I can do this electronically it would save me a great deal of tinkering.

Any insight on this would be appreciated.

Bill

[CleviteKid]

If the factory tach is for an eight cylinder gas engine, and uses the firing signal as it input, that should work. One advantage of my signal conditioner is that you can build and test it for about $5 of Radio Shack parts. Then you will know for sure. I think it would be wonderful to use the factory in-dash tach for your project. And we all want to see pictures and read about the results when you are done!

Dr. Lee :cool:

[convert2diesel]

Last time I fooled around with a tach on a gasser the only thing I worried about was the "point gap" (does that age me or what). My concern is that with the newer electronic ignitions, have they gone to the sine wave generator in the gasser's as well or have they just modified the circuits to allow a make break system?

Have been toying with the idea of making this conversion a comercial product and will be taking copious pictures to construct an instruction manual. Will keep all posted on progress. Hopefully the month of August (if it follows my usual project time line you can include September as well) to get the car and camper ready for three weeks in your part of the country in October.

First to visit Jamie again, then New Orleans and finally the panhandle and Orlando/Dismal World (we keep doing that!).

Thanks for the info

Bill

[mhagie]

I can vouch for Dr. Lees tach conversion.
I copied his set up and it works perfectly, it was a bit of a hassle at first cause the tach I used had the dip switch assy assembled bas akward, after I reversed the settings it worked fine.
GMCTD gave me assembly instructions that had the entire assembly barley larger than a pop bottle cap.
Look in my truck pics a pic of the transistor thingy is located there.......Merle

[convert2diesel]

Dr. Lee:

Many thanks for your research and final design. Made up my first electronic assembly over the weekend and it worked, much to my surprise.

Only two things that I have noticed, and perhaps it is the fault of my neophite attempt at electronic manufacturing. Don't worry IBM, I doubt I will ever be a threat. When I first start it up, the tach jumps up about 200 RPM when the glow plugs turn on and off with afterglow. Increases with lower voltage ????

After it comes off advance and engine idle drops below 800 RPMs, the tach jumps all over the place from zero to 800. Increase the speed over 800 and it steadies out to deadly accurate. Perhaps the lower voltage at idle is screwing it up. Any comments?

To those interested the bio-Buick lives and is happily gurgling along with a minimum of post transplant rejection. Helps to keep GM with GM and keeps the engineering to a minimum. Still have a few issues but it should be ready for a trip to see Jamie in a couple of weeks.

Will try to work up some pics and descriptions to show.

Thanks again

Bill