Cylinder Fuel Wash Down Wear
01-20-2009, 06:56 PM
#11
Gold Member
Gold MemberThread Starter
Join Date: Sep 2005
Location: Missouri
Posts: 1,987
Likes: 0
Received 0 Likes
on
0 Posts
Bill, some things to keep in mind when analyzing your A/F data log. These were separate runs that were superimposed onto the graph, right? Any throttle position change or MAP sensor change will result in a spike. So, each time you advance the throttle you get a squirt of fuel. As the attitude of the boat changes or even hitting a wave hard during the run can cause the MAP signal to change slightly. I'm guessing that is what is causing some of the spikes and valleys in your log. Overall the A/F values look to be about right, except at idle. I'm guessing the richness right off idle to 1400 rpm is due to throttle movement and load as the vacuum drop during acceleration. It's leanest at cruise, then drops to mid 12's at WOT, all OK. Seems like a leaking injector would show up most at idle. I would like to see your idle A/F closer to 13:1. That rich of an idle could be causing your excess fuel dilution, but I don't think would wash the rings and still only show 3% oil dilution.
Absolutely correct, each cylinder was recorded one at a time on eight individual runs and then the composite graph compiled. The test format was to record the A/F from idle to WOT by gradually/continously increasing the throttle position/rpm first with the drive trimed in until WOT max rpm reached and then trim out the drive for max speed / RPM. Obvioulsy the repeats can not be perfect. The most erratic cylinder to cylinder data was around 2100 to 2600 RPM which is plaining speed for my boat and more difficult to control. There were a couple runs ( at higher RPM's) where the throttle had to be backed off do to conditions and as you say the A/F then spikes. I deleted that data where the throttle had been backed off and it is not in the graph provided. I pretty much had the lake to myself January 9 so lake water conditions were mostly calm/smooth.
I appreciate your recomendation on A/F targets. I am now putting the data together for the next recal. Is 13.0 - 13.5 @3800 rpm too lean? FYI my personal cruise rpm is typically around 2500 rpm.
I especially appreciate your diagnosis that 3.8% fuel dilution is likely not enough to cause cylinder wash down. I did cook the oil pretty good with a lot of WOT runs just before I changed it and sampled for analysis. Do not know if %fuel might have been higher before that and I boiled some of it away.
Thanks again,
Bill
01-24-2009, 04:09 PM
#12
Registered
Is there any chance that your top and bottom ring just happened to be lined up at the time you took the compression test?? Have you done another test after running the motor again? What about doing a leak down to see if you can hear the air coming from somewhere specific.
Frank
Frank
01-24-2009, 08:04 PM
#13
Gold Member
Gold MemberThread Starter
Join Date: Sep 2005
Location: Missouri
Posts: 1,987
Likes: 0
Received 0 Likes
on
0 Posts
Is there any chance that your top and bottom ring just happened to be lined up at the time you took the compression test?? Have you done another test after running the motor again? What about doing a leak down to see if you can hear the air coming from somewhere specific.
Frank
Frank
