Wanted to pose a hypothetical for your consideration. When we get back a UOA (many are shared on this forum) we can see a variety of Fuel Dilution percentages...TR, <.5%, .5%, 1.5%, etc

What is "high"? Not sure, yet. A "high" Fuel Dilution percentage in a UOA is TOTAL dilution and cannot tell us why: individual or multiple cylinders, weak spark (plug and/or coil pack), injector(s), timing, compression, vacuum leak, MAF, driving conditions, driving style, etc.

For the included spreadsheet, I held all variables constant and only changed the Fuel Dilution percentage. I also chose one injector as the potential offender and assumed all other combustion contributors where 100%. Based on a number of UOA that are on Rennlist, I am assuming that TR, <.5% and .5% are probably the preferred, so i am using .5% and for the other end 1.5%.

The analysis indicates that IF one injector is THE contributor, then at 1.5% Total Fuel Dilution, it is contributing 72.6% of the fuel if the other 5 injectors are contributing 5.6% each at .5%.





Jake has pointed out that fuel injector spray pattern is very important to healthy engine combustion and longevity, and the source for cylinder wall lubricant wash down. For the DFI engines, the injector may only pulse once or it may pulse multiple times just for one combustion cycle, depending on the demand signals the computer is sensing, calculating and calling for.

So what I am thinking is that while there might be a number of opinions out there about acceptable upper limits for fuel dilution, anything greater than TR, <.5%, .5% (pick one) is cause for a deeper dive to determine if there is a mechanical reason causing one or more than one cylinder to contribute excess fuel.

Thoughts are welcome.

This little exercise now causes me to want to learn how to collect fuel trims via my Durametric for that day in the future when I "Gots to know". Anyone?

 

In Durametric go to engine, live values, then check fuel trim bank one and fuel trim bank 2. Then you can monitor what they do as you drive. If they drop below 1.0000p then the DME is sensing a rich condition and pulling fuel to lean out the mixture. If the number get larger than 1.000 it's sensing a lean condition and adding fuel.