I was reading through a thread the other day that mentioned that RPM can have a BIG effect on compression results.

I have a couple of questions because i check my compression every other month at the least.
First, I'm trying to figure out, what is the highest engine rpm the starter could achieve.
Second, what is the required rpm for a comp test.
Third, IS hooking up a battery charger while doing the test wrong?

90% of my test have been without the batt charger.

The results are always higher by 3-4 psi on the first rotor I test. (battery loosing juice?)


I recently did one with a batt charger hooked up. ON low setting.. Not charging just to keep the batt. even.

I ended up with 100 f and 100 r. For the first time i got dead even results with batt charger on there. But. The results were about 4 psi higher than ever before.
SO did the batt charger increase the rpm of thew engine.

 

The higher your starter RPM the higher your compression. Divide 250 by the RPM that your starter was going. Then multiply that result by your compression results. Then you'll have your final compression @250 RPM.

 

I dont know how fast the engne spun with the charger on it..

HOw fast could it spin?