EEHack Cylinder Balance Test

[ltxdave]

I recently downloaded eehack and was playing around with the cylinder disable feature and cylinder strength test. When I manually disable cylinders 1-4, the result is very noticeable. 5-6 not do much so and 7-8 almost undetectable. When I run the cylinder strength test, it shows 1-4 in the mid to low 40s for cylinder strength and 5-8 in the upper 50s, low 60s. I have two questions based on this.

Should I be looking for a mechanical problem with these results?

My logic tells me that the cylinders that yield the least change in engine operation would be the weakest cylinders, why is the result opposite of that?

The car is a 383 lt4 with Afr heads long tube headers and a cam with about 232 duration at 0.050 lift. I'm only seeing 65-70 kpa at idle, so are my results normal? The car does not feel like its weak or has a mechanical issue.

Thanks in advance for any help.

[spfautsch]

What is the LSA of that cam, and what is your idle spark timing? 65kpa @ idle seems low. Have you checked for a vacuum leak?

[ltxdave]

IMAG00325.jpg

Cam card.

I have no vacuum leaks that I can find. Everything is fresh with only break in miles on it so far.

[spfautsch]

What's the static compression ratio, and have to done any tuning?

[ltxdave]

About 10.8:1. I have been trying to tune for several weeks. These results are with added timing at idle and stock MAF tables.

[spfautsch]

For tuning idle, did you use the control section in eehack to find the timing (and target rpm) that gives best map reading with lowest advance?

Your cylinder balance test is more or less consistent with what I've been seeing only mine idles around 45kpa and is a 355. My cam is similar lift and duration but 113 lsa so possibly less choppy than yours.

The test looks at MAP and RPM variance to calculate a relative cylinder strength, so my numbers are skewed towards the lower idle vacuum.

------------------
CYLDROP Memo :: 
(Higher is better...)
CYL1=29.3 CYL2=30.0
CYL3=33.1 CYL4=33.0
CYL5=34.8 CYL6=34.6
CYL7=35.7 CYL8=36.3

I wouldn't fixate on the balance test too much, but I would check again with some starting fluid to see if you don't have a vacuum leak somewhere. That idle vacuum seems pretty weak to me. How does it drive?