Frequency controller

Hope this is the right section

I'm currently attempting to istall a set of digital dials into my car. I've got most of it wired up but i'm having the following problems:

Rev counter: Reads about 50% more than it should. I expected this due to the car being a 6 cylinder and the clocks coming out of a 4 cylinder

Speedo: Hooked up to the correct wire, when i'm doing 20, it's reading 15 on the clocks and when i'm doing 30 it reads 20.
I've asked this question on a car forum that i'm a member of and one of the members has pointed out that both the rev counter and the speedo will take their readings from the sensors and input to the clocks as a frequency


Is it possible to assemble a small piece of circuitry that would allow me to adjust the frequencies received from each item and either speed it up or slow it down till i get the correct ratio ?

I'm fairly new to electronics so please try and keep any advice in laymans terms

Any help or links to parts that i need would be greatly appreciated

If it is off, then it is off by an integer ratio. This came up once before. I posted a circuit that multiplied the frequency of a pulse train by 2/3. Look at my postings here, about a year ago...

MikeMl said:

If it is off, then it is off by an integer ratio. This came up once before. I posted a circuit that multiplied the frequency of a pulse train by 2/3. Look at my postings here, about a year ago...

Click to expand...

That works for the tach, but the speedo needs a frequency multiplication of about 1.5, which is more difficult. Conceivably you could double the frequency and then multiply by 3/4.