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Author Topic: a real tach  (Read 21709 times)

Reply #45September 04, 2009, 05:19:19 am

92EcoDiesel Jetta

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Re: a real tach
« Reply #45 on: September 04, 2009, 05:19:19 am »
Andrew, thanks again for telling me about the Jimbote method otherwise I'd still be trying to fit a Mercedes tach in the cluster lol. I am curious what size is the Ford probe? The square hall effect pickup I'm using is about a 3/4" cube. Gasser tachs that run off the ignition coil is seeing pretty high voltages and has circuitry to attenuate that voltage. I had to bypass that circuitry and also use magnets for the triggers to get higher voltage to the tach chip in order for it to work with the pickup that I am using. My guess is the Ford probe pickup must put out a much higher voltage than what I'm using, thus my question to its size.
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Reply #46September 05, 2009, 07:51:18 pm

92EcoDiesel Jetta

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Re: a real tach
« Reply #46 on: September 05, 2009, 07:51:18 pm »
Thanks for the pic Andrew. Is the Ford probe magnetic? i.e. if you put an iron screw on it, does it stick? Have you installed the tach yet? I'd suggest getting the tach and probe working on the bench with an AC motor of known RPM, before wiring it up in the car.
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Reply #47September 10, 2009, 08:47:58 am

92EcoDiesel Jetta

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Re: a real tach
« Reply #47 on: September 10, 2009, 08:47:58 am »
Andrew, magnetic is GOOD! They have higher outputs than non magnetic. Let us know when you get yours working.

I've not driven the Jetta much till today, so the epoxy's been curing all this time and I've rev-ed the engine a bit and the magnet triggers on the crankshaft pulley hasn't fallen off lol.  Here's a pic at 55 it's doing 2500 rpm. Is that about right for a 92 Ecodiesel?

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Reply #48September 10, 2009, 11:39:50 am

92EcoDiesel Jetta

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Re: a real tach
« Reply #48 on: September 10, 2009, 11:39:50 am »
Quote from: libbybapa on September 10, 2009, 10:23:02 am
Sounds reasonable.  Have been here and done the math?



Not sure if I did it right but per GolfJettaTransRatio.xls , I plugged in 2500 rpm on the row for the AVX transmission got 82 km/h in 5th which is 50.95 mph. About 3 to 4 mph slow.

But from http://scirocco.org/gears/ I plugged in tire size 185 65R 14, 4.25 final drive, 0.75 gear ratio, 2500 rpm and got 54 mph, which is what I am seeing on my speedo.

Here's a video of me shifting gear merging into highway traffic. (click to play). Video starts with 2nd gear and ends in 5th.



« Last Edit: September 10, 2009, 12:14:17 pm by 92EcoDiesel Jetta »
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Reply #49September 10, 2009, 11:52:49 am

92EcoDiesel Jetta

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Re: a real tach
« Reply #49 on: September 10, 2009, 11:52:49 am »
The end of the video shows at 3000 rpm it's doing 65 mph. I plugged the numbers into http://scirocco.org/gears/  and got exactly 65 mph. ;D
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