Modifying tach signal?
10-09-2008, 10:28 PM
#1
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Join Date: Feb 2004
Posts: 7,785
Modifying tach signal?
I'm having a hard time finding a tach that will work with the twin in my bike. I know Shindy makes a nice electronic tach but are a bit pricey. The only other tach besides the crusty Drag Specialties mini tach will work but only read up to 8k is a Apexi tach. This is HMT so I can't see spending 2-300 dollars for a tach. My question is there anyway I could reduce the signal the tach is seeing by half since tach like Autometer and whatnot usually only at four cylinders and go up from there. Could I install resistor between the wiring from the tach to the coil? I mean what is on the inside of a aftermarket tach that adjust the signal from when you switch from 4 to 6 or 8 cylinder?
10-09-2008, 11:30 PM
#4
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Join Date: Dec 2002
Posts: 1,463
Re: Modifying tach signal?
Use a frequency divider latch type circuit.
http://www.electronics-tutorials.ws/...r/count_1.html
Takes pulses in and gives half the pulses out.
http://www.electronics-tutorials.ws/...r/count_1.html
Takes pulses in and gives half the pulses out.
10-09-2008, 11:33 PM
#5
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Join Date: Oct 2005
Location: St. Augustine FL
Posts: 3,936
Re: Modifying tach signal?
Originally Posted by TunerToys
Use a frequency divider latch type circuit.
http://www.electronics-tutorials.ws/...r/count_1.html
Takes pulses in and gives half the pulses out.
http://www.electronics-tutorials.ws/...r/count_1.html
Takes pulses in and gives half the pulses out.
10-09-2008, 11:46 PM
#6
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Join Date: Dec 2002
Posts: 1,463
Re: Modifying tach signal?
Yep, you could filter down the signal from the engine, and shape it up into a square wave for the flip flop. One it's a square wave of the proper voltage (logic levels are 0 to 5vdc), you can do just about anything with it. As long as you find a tach that can read that same square wave, you are good to go. Even if the tach has to have a larger signal, you can amplify the square wave
Craig
Craig
10-10-2008, 12:20 AM
#7
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Join Date: Apr 2006
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Re: Modifying tach signal?
if you set input on 4cyl with a tach redline of 8k, a single cyl 2-stroke could fire 16k rpm and register as a 4cyl spinning 8k
same with super duper rev happy cars. 4cyl that revs 12k+ set to 8 cyl on tach and it reads 14k as 7k on the 8cyl setting
same with super duper rev happy cars. 4cyl that revs 12k+ set to 8 cyl on tach and it reads 14k as 7k on the 8cyl setting
10-10-2008, 12:24 AM
#8
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Join Date: Feb 2004
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Re: Modifying tach signal?
My electronic skills kicked the bucket after I left the air force nearly ten years ago. Can you actually buy one or do you have to build it? The schematic almost looks like a relay type circuit with the four ternimals it would have. Enlighten us Craig on where we would find a frequency divider latch type circuit.
10-10-2008, 05:55 AM
#9
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Join Date: Sep 2008
Posts: 118
Re: Modifying tach signal?
Originally Posted by stillnoturbo
I'm having a hard time finding a tach that will work with the twin in my bike. I know Shindy makes a nice electronic tach but are a bit pricey. The only other tach besides the crusty Drag Specialties mini tach will work but only read up to 8k is a Apexi tach. This is HMT so I can't see spending 2-300 dollars for a tach. My question is there anyway I could reduce the signal the tach is seeing by half since tach like Autometer and whatnot usually only at four cylinders and go up from there. Could I install resistor between the wiring from the tach to the coil? I mean what is on the inside of a aftermarket tach that adjust the signal from when you switch from 4 to 6 or 8 cylinder?
10-10-2008, 08:36 AM
#10
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Join Date: Oct 2005
Location: St. Augustine FL
Posts: 3,936
Re: Modifying tach signal?
i just want one of my cheap CDM tach's to work on my CDM scooter. the most RPM it will ever see should be about 12k and thats a ways down the road. stock is about 8.5-9k.
someone help a nog out, i can solder things together, but i really know nothing about how they work
someone help a nog out, i can solder things together, but i really know nothing about how they work
