ALFAGTV6.COM

Jose_76 · Post by **Jose_76** » Wed Mar 29, 2006 1:49 am

How can I re-calibrate my Rev-counter? It works, but shows much higher revs than real.

SamW · Post by **SamW** » Wed Mar 29, 2006 3:11 am

Yes, if you take it completely apart there is a little screw on top of the mechanism that will adjust it.

Jose_76 · Post by **Jose_76** » Wed Mar 29, 2006 3:15 am

Thanks, SamW

I've just downloaded a sound generator program, so I can get any frequency associated to a determined rpm. I just don't know (still) how to connect the sound card exit to the rev-counter and what's the right swicth on it!!!

Jose_76 · Post by **Jose_76** » Wed Mar 29, 2006 12:03 pm

I've just put the rev-counter apart and tried to see how it goes, but I couldn't get any pulse on it. Please help.

Here I got two pictures of the rev-counter before and after dissasembling it and what I could find out.

SamW · Post by **SamW** » Wed Mar 29, 2006 2:01 pm

Not sure what you are doing, but you can get a volt meter that has a rpm guage on it, then disassemble the tach (rev counter) and just sync them up, but don't change the starting point, just adjust the screw.

Jose_76 · Post by **Jose_76** » Wed Apr 05, 2006 12:10 am

Ok, I found the adjuster and it's not the one marked in the previous picture.

Using a program, I got a 300Hz (to match 6.000rpm) square signal out of my speakers, but only 0.5 Volts amplitude (should be 6-12V). I plugged the negative pole o it to the ground on the tach and the positive to the center bolt (marked with a red arrow in the pic.). I also fed the Tachometer with 9V DC (- to the upper bolt and + to the lower bolt).

I got no response on the Tacho

, but I don't know if I plugged something wrong or if the square signal is just to weak.

gtv6fan · Post by **gtv6fan** » Wed Apr 05, 2006 4:25 pm

To claibrate this correctly you really need to be measuring the output at the coil using an old tach and dwell meter. SOund is was FIA uses to show you the nifty little rpm gauge one the screen and is only accurate to 1000 or so rpm.

Jose_76 · Post by **Jose_76** » Thu Apr 06, 2006 7:53 am

I think I finally did it!! I just have to compare with a stroboscopic lamp to be sure. I'll post the solution as soon as I can confirm it's OK

And it's easier than I thought!!!!

Daniel · Post by **Daniel** » Wed Jan 03, 2007 6:27 pm

Hey Jose,
Did you come up with a solution for this?
I'm trying to work out what signal type a GTV6 tacho needs - 12v square wave, signal to ground or voltage spike

I also need to know what signal the tacho output of the Bosch Motronic M1.7 computer on a 24v is.
Pretty soon I'll need to get these two to talk to each other and I'll need to recalibrate my tacho to match.

Jose_76 · Post by **Jose_76** » Mon Jan 08, 2007 6:14 am

Sorry for the delay.

At first, I fed the tacho with 12V DC and got the 50Hz signal from the output of the transformer of my computer's speakers

, but as then I could only adjust it at one ponit (1000rpm, or 1200rpm if 60Hz) it's not very accurate.

Then I could have access to an oscilloscope and a signals generator, so I could feed the tacho with sinusoidal signals 9-12V AC and 50-300Hz, and adjusted it to the highest. If you adjust it on the lowest then the error is very important when you reach 6000rpm (about 500rpm), and I prefered to have an error about 300rpm on the tacho at idle that vanishes as it goes up.

One more thing: the tacho was quite sensible to poor amplitude signals, that is that it gave different readings when fed with 9-10V both in AC and DC. Must check.

Hope this helps.

Daniel · Post by **Daniel** » Mon Jan 08, 2007 12:47 pm

Yep, just have to get my hands on a signal generator.
Thanks for the help.

How to calibrate Rev-counter on GTV6?