I was reading on the net somewhere that the fc stock
tach can be adjusted to get it close to a correct figure
when running the 20b, any one know what is needed to
adjust the tach?
I have opened it and looked in there,, I see 2 pots
that look like they could be adjusted but I am unsure
which is the one to mess with...
I could just start adjusting the thing but I thought I
would ask first..

matt
ps. reted,, i know you know the answer to the above
question, question is will you offer up this little bit if
help?

 

There is an adjustment screw.&nbsp Sorry, I can't give you an accurate description of the location, as I haven't done this in over a year; the screw should be close to the tach are on the IC board though.&nbsp We used to calibrate the tachs with a dedicated microprocessor (STAMP) that was programmed just to output a negative pulse tach signal.&nbsp The other way to do it is to use an inductive timing light with an RPM display (i.e. Snap-On timing gun) and adjust until it matches that number with the stock tach.



-Ted

 

there are 2 adjustment screws on that board,,,
one with a plastic frame and one that is metal,,
just thought you might remember which one was the one.

matt

 

so no one can tell me which one to adjust ?

 

http://members.tripod.com/~grannys/rx7tachrecal.html

BTW, if you use this jury-rigged signal generator method, the 20B would read the signal at a 2700rpm calibration target, and the 13B would be 3600rpm.

Edit: I screwed up the 13B info, but I fixed it now. Sorry.

 

thank you evil

matt

 

evil> i assume that i would be setting it to the v6 value?

matt

 

I guess that's an easier way to look at it. Sure, 2-rotor = V4, 3-rotor = V6, 4-rotor = V8. The same goes for aftermarket tachs and EMS units which don't have a "rotary" setting.

 

From the grave.

I was wondering how accurate this is setting it at the V-6 setting?
I did what was described in the grannySS link and my tach seems to be closer
to accurate but I don't think it's right on.

 

Anyone know how to modify a 1st gen tacho for a 3 rotor?

 

^ It shows you how on the grannyspeedshop link (see post #5). Just follow the steps for a V-6 conversion. I just want to know if the tach reading is accurate after doing this, or how do I check it?
With a timing gun like Ted suggested?

 

i compared it to the haltechs reading