Power balance test

[halz]

Here's a new one to me: an engine power balance test. Has anyone else heard of this?

This test was performed by the people who recently tuned and ajusted the carbs on my L24. When I questioned them more closely, they told me that the test is a truer assesment of the performance of each cyclinder than a straight compression test. Here's what they do:

The engine is connected to electrical diagnostic equipment which allow the rpm to be accurately measured. With the engine warm and at idle, one plug lead at a time is disconected and the drop in rpm is measured as a % of the idle rpm. So, if my engine idles at 750rpm and the power balance test records a '10' when the cylinder is disconnected, then 10% of 750rpm is a 75rpm drop when that cylinder is not firing.

The results for my engine were: 1=5.2, 2=3.5, 3=8.7, 4=8.5, 5=8, 6=11.

This is interpreted to mean that cylinders 1 and 2 are contributing the least effort to the overall engine performance since rpm drops the least when they are each disconnected in turn. Compression on these cylinders is fine - so there must be other reasons they are not performing as well as the other 4... weak valve springs?, poor spark?, something else?

your thoughts?

[260Zed]

Was the place you went to part of a chain? Or a specialist? Do you know the equipment they used? Sounds like and interesting test to have done.

Luke

[halz]

Was the place you went to part of a chain? Or a specialist? Do you know the equipment they used? Sounds like and interesting test to have done.

Luke

No. Yes. Don't know. They are called "Carburettor Exchange" in Fremantle, Western Australia. You could have a chat to them. the man to speak to is Daryl Wardle, 08 9335 1769.

[Alfadog]

It sounds like a very interesting test. I'm jealous you have someone that THOROUGH over there. I'd really like my carbs to be all tuned up perfectly. Excuse my ignorance for a moment but....... with a SOHC straight 6... are you sure all 6 cylinders are meant to contribute equally? :stupid:

[gramercyjam]

Yes. Although I know it as a standard diagnostic. Helpful for quickly pinpointing performance problems. If compression is fine as you say, I'd look at ignition issues.

[beandip]

I agree this is an interesting test and it can be performed by doing the same thing and watching the tach and watching the RPMs . I do this when locating a missfireing cylinder . The interesting part for me is having a print out showing the numbers. I dont think weak valve springs , or the compression test would show it . Unless the the testing is done at uper RPM . I would look at Spark plugs , Plug wire or dist. cap.