Want some help here !

[Maze]

Hi all ,

i want to know the standard value of comprission test to calculate it in persantage (%).

ex: if the cly.1 = 14
cly.2 = 13
cly.3 = 10
cly.4 = 13.5

whats the total value in (%) !!

and there is a different from engine to engine in this standard value ..?

 

[s130]

One has to be clear about what you are trying to measure.

Generally when it comes to engine compression measurements then the manufacturer may specify a figure of X +/- a unit value or percent value.

When this data is not available then you are left comparing accepted values for a given compression ratio and/or cylinder variance.

Genrally 10% to 15% varience is considered as acceptable in a road going car. Motorsport / performance cars will generally have tighter values. I don't know for a fact but I would expect an F1 engine to be at least less than 5% and probably less than 2% or 1% varienance.

You firgures have 14 and 10 at the limits so this a 40% variance. Or +/- 20% from the mean.

In the absence of a target/recommend value then the variance/difference between values becomes the guiding point.

In your example cylinder 3 is low compared to the others.

Another way of looking at this is 13 + 10% = 14.3
13 - 10% = 11.7

Again cylinder 3 is low compared to the others.

If you compare 14 to 10 then it is a 40% difference.