Cost to swap into Gami injectors?

[rwtucker]

I'm missing something. I searched 'kjmeyers1' and this is the only thread I can find that contains 'cylinder.' In any event, a cylinder not making compression doesn't get us to the root of the problem. Was it a burned exhaust valve . . . a cracked compression ring . . . deformed due to overheating because of a bad baffle . . . ? Big differences. I asked about break-in oil because it can be material to the current problem. Whether or not to use straight non-ashless dispersant mineral oil is debated a little, although our Diamonds came from the factory with it and it is recommended that we run it for 50 hours to ensure proper seating of the rings. There is more agreement that synthetic oil should not be used for breaking in a new barrel, especially those that contain anti-scuffing compounds as most do. You want scuffing for the first 20-50 hours. The commonly used Shell 15/50 is semi-synthetic. The first thing I would do is diagnose the problem before considering Gami injectors. A 50 degree spread is too high. What are the other temps? What are the EGTs? (Was the #1 injector replaced also?) Is the baffling intact and aligned correctly (you need to blueprint the fit to the cowling to see)? Gamis are a refinement sought mostly by LOP drivers. (Other pilots install larger injectors for more power.) I do not think they should be seen as a solution to a hot cylinder, especially one that was apparently malfunctioning before you replaced the barrel. You may be headed for the same failure because of an undiagnosed cause.

[kmeyers1]

There was s burned valve. The cylinder was replaced at the oil that was used was Philips x/c aviation 20/50w oil. I'm not sure about what the cht and egts were running. I had the plane ferried from Florida to California and almost immediately we had it in for its annual as the balance of the factory warranty was about to run out and we wanted to have it all checked out before the warranty was gone. My shop is a Diamond Service center in Northern California.

[rwtucker]

Phillips is not synthetic so it is quite likely that your rings seated fine some time ago and that you don't have any glazing. Fifty degrees is too high, too much difference, and more than you get with a new barrel. It is especially too high if you are running ROP and the others barrels are 350-380 and close to 400 on climb out, which is typical ROP CHT for this aircraft.

It is hard to say what the problem is but I would do two things ASAP: (a) note the CHTs and EGTs for all cylinders under (i) takeoff, (ii) climb and (iii) cruise; (b) check the baffles. First, look to see if they are intact, not frayed or bent, etc. Pay special attention to the area that is designed to channel air to the hot barrel. Then, with the top engine cowling off, place a colorant on the leading edges of the baffles that contact the top engine cowling. Carefully fit the cowling back on and seat it (no need to lock the screws but use two people so you can sit it down straight). Then remove the cowling (two people again, straight up so as not to smudge the marks) and examine the lines of color that the baffle edges left. There should not be any gaps. If there are gaps, the baffling needs to be repaired (realigned, replaced, etc.) in that area. I have done this myself and found a few small gaps. My CHTs improved when I fixed them. I have heard other DAN members comment on baffle problems with some of the lower serial number DA-40s. Do these things first and see what you find. In the meantime, make sure you keep the hot barrel under 400, if you can. (I'm fussy on this point, my turbocharged TSIO-360 consistently runs 425 but then it has an 1,800 hour TBO and rarely makes it to that.)

Bottom line, when you hear hoof-beats, think horses, not zebras. In this case, the horse is a burned valve and a high CHT that may have been high before the fix. It is possible that it could be an injector but if it were lean enough to cause a 50 degree high CHT, the EGT on that head would be very high; i.e., valve burning high on takeoff configuration.

[Chris B]

There should not be any gaps. If there are gaps, the baffling needs to be repaired (realigned, replaced, etc.) in that area. I have done this myself and found a few small gaps. My CHTs improved when I fixed them. I have heard other DAN members comment on baffle problems with some of the lower serial number DA-40s.

FWIW, I was quite surprised by the CHT improvement after fixing seemingly very small (2-3mm) gaps between the top cowl and the baffles. So this is definitely worth checking.

OTOH, according to my very experienced IA, burned valves in Lycoming IO-360s are exceedingly rare. Presumably, minor cooling issues would not cause such problems, otherwise lots of these engines would have burned valves. So unless your baffles are completely whacked, something else is probably the primary issue.

Chris

[rwtucker]

OTOH, according to my very experienced IA, burned valves in Lycoming IO-360s are exceedingly rare. Presumably, minor cooling issues would not cause such problems, otherwise lots of these engines would have burned valves. So unless your baffles are completely whacked, something else is probably the primary issue. Chris

I may not have made it clear but I was questioning the same thing. However, I think you might burn a valve in this situation. Imagine a summer climb initially at 100% where normal CHTs will hit 400 degrees and may go over, depending on how aggressively you manage speed, mixture, etc. (Not everyone climbs by managing EGTs to 1,350 like we do.) Now, add 50 degrees for one barrel to a 410 degree baseline and a high EGT and you might get enough of a rough edge on the seat to drop the compression. Possible . . . I'm not sure where my money is but, since there was a burned valve and that is purportedly linked to the high CHT, it can't hurt to check the baffles. For sure, future flights should be with the engine monitor on (I switch to mine by habit every few minutes). I don't think this problem (whether new or old, coincidence or not) is fixed.

[kmeyers1]

Thanks for all the input from everyone. I've got some good input to work on.

[Antoine]

Kenneth does your G100 have the software release that allows logging to be enabled?
If this is the case, we have all of the info at hand to take the guesswork out of this diagnosis.
If you are not familiar with the logging and how to upload the data, just ask.

[kmeyers1]

It does. I haven't recorded yet. I just got a spare sd card for the plane. Is there a post that you know of or page that goes over the process so I can upload my data?

[Antoine]

It does. I haven't recorded yet. I just got a spare sd card for the plane. Is there a post that you know of or page that goes over the process so I can upload my data?

The SD card goes in the upper slot of the MFD. There is a directory that holds the flight logs and each file has the date of flight as its filename.

After the flight simply plug the SD card into your computer, go to this site on the reports tab, click on the "select file" button, navigate to the file and upload.
That's it!
If you'd like to use the file for your own data analysis, you can just load it into an excel spreadsheet (it is a CSV file). I do that to extract speed data from my speed test runs.
This kind of info is like having a flight engineer on board. Every second, you get each and every EGT, CHT recored, plus fuel flow, OAT, MAP... Makes it very easy to understand what is wrong.