# Unsure what area this relates to but im struggling with an ignition map

• June 20th 2010, 03:07 PM
powermandan
Unsure what area this relates to but im struggling with an ignition map
Im trying to write a microcontroller program to run the ignition in my car.

However im struggling to interpret values from a table properly if the value i need falls inbetween the values in the table, im not convinced the method im using does a very good job.

Going by the image i have attached what would be the value for advance be if the load was 67 and the RPM was 4600?

thanks

Dan
• June 20th 2010, 11:15 PM
earboth
Quote:

Originally Posted by powermandan
Im trying to write a microcontroller program to run the ignition in my car.

However im struggling to interpret values from a table properly if the value i need falls inbetween the values in the table, im not convinced the method im using does a very good job.

Going by the image i have attached what would be the value for advance be if the load was 67 and the RPM was 4600?

thanks

Dan

Linear interpolation:

1. Assume that the increase between 60 and 80 or 4000 and 5000 respectively is proprtional. That means: To reach the 67 you have to calculate: $67 = 60+(80-60) \cdot \frac{7}{80-60}$. So the increase is $\frac7{20}$ of the difference of the 2 corresponding values.
Now calculate the 2 values in the 4000 and 5000 column.

2. The increase in the last row is $\frac{600}{1000} = 0.6$ of the difference between the 2 corresponding values in the last row.

3. Now calculate the increase between the newly calculated values.

4. I've attached a table with the results.
• July 13th 2010, 06:11 AM
powermandan
Thank you very much