Rev Counter Problem need info on a signal divider

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Discussion Overview

The discussion revolves around a problem related to signal processing for a car's rev counter after changing the engine from a 4-cylinder to a 2.5 V6. Participants explore potential electronic solutions to adjust the pulse signal from the new engine to match the requirements of the rev counter.

Discussion Character

  • Technical explanation
  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant describes the issue of the new engine providing 3 pulses per revolution compared to the previous engine's 2 pulses, leading to an overreading of RPM on the rev counter.
  • Another participant suggests that changing the memory chip in the ECU to one that matches the new engine might be a simpler solution for better performance.
  • A different approach is proposed involving two chips: using a CMOS 4070 XOR gate to multiply the signal by 2 and a CMOS 4017 decade counter to divide the signal by 3, with additional components for signal buffering and pulse stretching.
  • One participant expresses a lack of electronics knowledge and requests diagrams for building the proposed solutions.
  • A suggestion is made to consult a specific company for additional assistance or products related to the issue.

Areas of Agreement / Disagreement

Participants present multiple competing views on how to address the signal adjustment problem, with no consensus reached on the best approach.

Contextual Notes

Participants express varying levels of familiarity with electronics, which may affect the feasibility of proposed solutions. There are also assumptions about the compatibility of components and the specific requirements of the rev counter that remain unaddressed.

Who May Find This Useful

This discussion may be useful for automotive enthusiasts, electronics hobbyists, and individuals facing similar issues with engine signal processing and rev counter calibration.

Drisruptor
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Hi

i know that this is probably not the best place to look for help but i have been to a lot of forums with no real result . The problem i have is that we changed the motor on my car form a 4 cyl 2l witch gave me 2 pulses per revolution to a 2.5 v6 but this motor gives 3 pulses . its form a separate wire from the ECU . the only other info i have is that the signal does not come from the coil on the car , at idle the signal is 25 Hz and above 2500 rpm its 125Hz . to give a idea how mutch its over reading with the old motor at 120km/h in top gear it was sitting at about 3500 rpm , same speed on new motor its about 5500 rpm . the info i got was that i need to divide the signal by 1.5 and that Possibly a 4046 cmos part with x4 output and a bit of logic to divide it back down by 6 would do the job.

The main problem is me because i never had a chance to learn about electronics , the only time i can build something is if i have a diagram :redface: .

Thank You for your time
 
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Drisruptor said:
Hi

i know that this is probably not the best place to look for help but i have been to a lot of forums with no real result . The problem i have is that we changed the motor on my car form a 4 cyl 2l witch gave me 2 pulses per revolution to a 2.5 v6 but this motor gives 3 pulses . its form a separate wire from the ECU . the only other info i have is that the signal does not come from the coil on the car , at idle the signal is 25 Hz and above 2500 rpm its 125Hz . to give a idea how mutch its over reading with the old motor at 120km/h in top gear it was sitting at about 3500 rpm , same speed on new motor its about 5500 rpm . the info i got was that i need to divide the signal by 1.5 and that Possibly a 4046 cmos part with x4 output and a bit of logic to divide it back down by 6 would do the job.

The main problem is me because i never had a chance to learn about electronics , the only time i can build something is if i have a diagram :redface: .

Thank You for your time

Welcome to the PF. It might just be simpler to change the memory chip in the ECU to the one that matches the new engine. Is that a possibility? Probably get better performance with the correct ECU chip as well.
 
I think you can do it with two chips. First, you want to multiply by 2. Use the CMOS 4070 exclusive OR (XOR), and put the input signal into two inputs of the same exclusive XOR, with one signal delayed by say 100 microseconds by using an RC delay circuit. Each input pulse in will then give two pulses out, separated by 100 microseconds. Then to divide by 3, use a CMOS 4017 one-of-ten decade counter, and use the "3" output to reset the counter (you may have to invert the signal by using one of the unused XORs), the reset signal will then be a divide by 3. You may want to buffer this output with a transistor. You may also want to use a one-shot (monostable) to stretch the output pulse.
 
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