# Rev Counter Problem need info on a signal divider

• Drisruptor

#### Drisruptor

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 .

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 .

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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## What is a rev counter?

A rev counter, also known as a tachometer, is an instrument used to measure the speed at which a vehicle's engine is rotating. It displays the number of revolutions per minute (RPM) of the engine.

## What is a signal divider?

A signal divider is an electronic component used to divide a signal into smaller portions. It is commonly used in circuits to reduce the amplitude of a signal or to create multiple copies of a signal for different purposes.

## What is the problem with the rev counter and signal divider?

The problem with the rev counter and signal divider is that the signal divider may cause inaccuracies or fluctuations in the reading of the rev counter. This can result in incorrect readings of the engine's RPM and can affect the overall performance of the vehicle.

## How can the rev counter problem be solved?

To solve the rev counter problem, it is important to use a high-quality signal divider that is specifically designed for use with rev counters. It is also important to properly calibrate the signal divider and rev counter to ensure accurate readings.

## Are there any other potential solutions to the rev counter problem?

Yes, there are other potential solutions to the rev counter problem. Some rev counters may have built-in signal dividers that can be adjusted to improve accuracy. Additionally, some newer vehicles may have digital rev counters that are not affected by signal divider issues.