Thanks Steve, I am certainly not looking for perfect matching of EGTs, in fact just non sooted plugs would be fine.Steve Brown wrote:Hi - the C90 and O-200 are notorious in their poor mixture distribution. This is mainly due to the tortuous long inlet tubes, the offset nozzle and the design of the cold spider positioned so close to the throttle valve.
There is no time for the mixture to fully atomise before it is 'split' so this configuration causes the fuel droplets to be directed onto the spider walls, which re-liquifies and dribbles neat into one or two inlet tubes resulting in a richer mixture.
The one piece venturi exacerbates this further because it is a far 'clumpier' casting than the much more precision made two piece version and it doesn't flow as well. Fixing one problem can cause other problems- sometimes more serious! Hence the revised AD (below) and TCM 'fix' of the pepperpot nozzle to compensate.
http://rgl.faa.gov/Regulatory_and_Guida ... enDocument
The ideal is probably to revert back to the two piece venturi while still using the better atomising pepperpot nozzle but this requires re-activating the recurring annual/100hr inspection to ensure the two piece venturi is not loose.
I guess I am saying that provided you have taken the good advice & eliminated the aforementioned issues like air leaks etc. you may have to live with the EGT spread (which in my view is not atypical or too bad). People spend a lot of money on fuel injection and even individually tailored GAMI nozzles to get a more even spread of EGTs.
Having good instrumentation is a real benefit for sudden unexplained changes and fault finding and also precise leaning but increased information can sometimes worry one unduly. Just like dust under the carpet!
My research over the past weeks or so echo pretty much what you have written above. I don't really want to have to start riping a brand new carab to pieces. Perhaps I should look for an altnative such as a throttle body injector?
Phil