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CHT

One more idea to throw into the pot. There are timing marks on both the fwd and aft sides of the ring gear/flywheel. The marks on the fwd side index to a mark on the starter motor, IIRC. The marks on the aft side index to the case seam.

Is it possible that you are misinterpreting what TDC is by using the wrong index point for a particular set of timing marks? E.G. using the forward timing marks but aligning to the case seam.

This would shift your timing a bunch. I haven't thought about how much, maybe too much and the engine wouldn't even run? I haven't thought through whether it would be too advanced or too retarded.

Anyway, given everything about your set up seems pretty good, there must be something significant that is not right that we haven't thought of yet.
 
I find TDC with the piston first and then check that the timing mark was at the TDC line, so that position gets cross-checked. I then set the timing using both the timing mark and digital level for confirmation. I am pretty confident in the static timing at least.
 
This might seem pretty unlikely, but at this point with lots of details confirmed OK, lets look for zebras in the horse coral.

Is it possible the cht probes are the wrong kind (type J vs type K) or that there is a polarity swap somewhere in the harness?

Here is a test -- pull a cht probe out and put it in a small pot of water on a hot plate. When the water boils, you know the temp (depends a bit on your altitude) but it is a good end-to-end check that the cht probes are reading right.

They are the dynon-supplied probes, connected to the factory-terminated harness. They read pretty accurate to OAT before start. That said, it is quite possible the calibration is not great, but that may account for some small difference.
 
Any concern about tape looking ok during the ground run then coming loose during flight and creating serious air flow issues (blocking a cylinder) before the plane can be landed?

Think I would come up with something other than tape for testing.....

Not too much, that same tape is holding my rudder trim tab on with no issues. Ill wrap it around the leading edge of the inlet some, so the edge can't peel up.
 
Keep in mind...the tape should form a seal, but flow separation is another issue. Removing the aluminum backing strips will help, as they would just form a big bump under the tape...no actual shape change.

This is theory. No one, to the best of my knowledge, has quantified the effect of inlet sealing and inlet shape. It may be tiny or it may be significant. I'd love to see before and after pressures in the plenum and lower cowl volumes.

Speaking of which, if the connection to the airbox is poorly sealed, the cowl air inlet pressurizes the lower cowl volume. Mass flow through the fins is dependent on pressure difference between upper and lower.
 
Dan,

I agree, the step on the inlet is probably the worst offender. So it will come out for testing. The airbox is well sealed.

It will be a bit before I hsve anything new. Today was my only chance to fly until next week. The rain snd 45kt gusts kept me on the ground.
 
Great thread; reading with much interest. I'll be doing this (and asking you all for help) in a few months!
 
Ok, I flew again this morning. I had removed the upper plenum-to-cowl seals and backing strips. I then sealed the junction with tape. Overall, I would say there was no significant improvement. Dang, I was really hoping to find a smoking gun.

20190908-062031.jpg


20190908-070849.jpg


This one looks better, but just a much lower OAT

20190908-114831.jpg
 
Ok, I flew again this morning. I had removed the upper plenum-to-cowl seals and backing strips. I then sealed the junction with tape. Overall, I would say there was no significant improvement. Dang, I was really hoping to find a smoking gun.
This one looks better, but just a much lower OAT

Colin, average your CHT's and compare. You got a 30F CHT drop, while the OAT drop was only 17F.
 
Colin, average your CHT's and compare. You got a 30F CHT drop, while the OAT drop was only 17F.

Yes, but the power was pulled back farther as well. I was running around pretty slow today. Both of those pictures above are from today, same flight.

Here is "Before" vs "After"

Two weeks ago, similar OAT, but higher power setting

20190825-080840.jpg


From today, with the inlet change
20190908-102220.jpg
 
Unfortunately I did not get a good comparison at the same power level and OAT. I will need to do another test, matched as closely as possible to get a direct compariso.
 
The last leg of my flight, it was really hot out. I wasn't ready to try it without the tape. CHTs got to 450 on climeout still. Even climbing at 120kts. OAT was 99F. My tablet even quit on me (overheat)..time to call it a day.
 
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I would check the mags with the power up and see if there is a roughness
Swap your EGT probes. See if it moves
Check your lower No 4 spark plug see if it is firing or fouled with lead if Fuel injected check no 4 injector. I am not an engine expert like Dan and others are this is just where I would start.

On one other note I saw in the first post a comment about running LOP with 10 hours on the engine. I was told not LOP till after the CHT?s dropped and had at least 25 hours in the engine by Carlus Gann who built my engine.

Dan you probably have a lot of thoughts in this. But someone hit it on the head about the timing that helped alot
 
Got any cowl exit pictures? A profile (side) picture would be nice, as would a picture from under the airplane, looking up through the cooling air exit to see if there are any excessive flow disruptions.
 
The ignition is working well, mag drop is very good on both sides, and almost the exact same. Timing had been checked many times now. The LOP note was from someone else, my carbed engine wont go LOP without excessive roughness.

I don't have a picture of the cowl exit, but Ill take one next time I am at the airport. In that area, everything is per-plans. I did open up the exit about 1/2", there was no noticeable improvement.

Oil consumption is great, I havent had to add any between oil changes. I would say less than 1/2 qt per 10 hrs.
 
My problem was timing as discussed. As a comparison data point, by coincidence on a recent flight with 66% and same conditions as you now with 15 hours on my new engine it is 370-380 CHT and about 1350 EGT ROP with oil at 176 and fuel flow at 8.5 at 160 knots TAS. It is an IO so the fuel distribution may be better. Even at peak the highest EGT only goes to about 1450 but probe locations could cause the EGT difference between engines.
 
My problem was timing as discussed. As a comparison data point, by coincidence on a recent flight with 66% and same conditions as you now with 15 hours on my new engine it is 370-380 CHT and about 1350 EGT ROP with oil at 176 and fuel flow at 8.5 at 160 knots TAS. It is an IO so the fuel distribution may be better. Even at peak the highest EGT only goes to about 1450 but probe locations could cause the EGT difference between engines.

That #4 EGT probe is just having issues, the readings are not correct as noted a much earlier post. Just a bad sensor I need to swap. It goes between fail and high constantly, sometimes settles down for a minute, then off it goes again.
 
Impulse coupling

Just wanted to point out something I haven't seen posted here in this discussion. When you are setting your timing, you find TDC on Cylinder #1, make sure the timing mark for TDC on the back of the ring gear is aligned with the split in the case half. Then proceed to rotate the prop counter clockwise in its normal rotation until you hear the impulse coupling "snap". THEN back the prop back up to the 25 degree mark on the back of the ring gear aligned with the case half and the mag growler light should come on for both mags. Just hadn't seen anyone mention unloading the impulse coupling before setting timing.
 
Just wanted to point out something I haven't seen posted here in this discussion. When you are setting your timing, you find TDC on Cylinder #1, make sure the timing mark for TDC on the back of the ring gear is aligned with the split in the case half. Then proceed to rotate the prop counter clockwise in its normal rotation until you hear the impulse coupling "snap". THEN back the prop back up to the 25 degree mark on the back of the ring gear aligned with the case half and the mag growler light should come on for both mags. Just hadn't seen anyone mention unloading the impulse coupling before setting timing.

Rusty, thanks for the advice. Yes, I always make sure the impulse coupling is released when setting the timing. I've checked the timing almost 5 times at this point.
 
Instant CHT cure

Hello

20hrs into flight testing IO-360 A1B 200Hp.

Amongst other niggles had high oil temp and high CHT. Discovered EFIS setup issue when I dipped CHT thermocouple into a kettle *while* it was boiling. Compared EFIS temperature to a multimeter with a thermocouple. Discovered EFIS overreading by 40 to 60 F. Discovered I had the wrong type of thermocouple selected for what was installed (I had J type and EFIS assumed K type). Selected J and now CHTs very much believable.

Regards
P.
 
Timing

Reference post #71, the prop should be turned backwards slightly past the 25 degree mark and the moved slowly forward to the 25 degree mark.
 
Just some follow-up. Passed 40hrs recently. Same cooling setup. I tested with and without my inlet seals, then with and without duct tape in there place. I don't have a manometer setup, so I cant accurately quantify the results. Based on general observations, I would say the duct tape provided the best cooling flow, but only very slightly if any over my original setup. Without any gap seal was noticable, probably worth almost 10 degrees on climbout.

At this point I am back to my intial setup, It appears the engine just needed some more break in time. Temps have dropped quite a bit. In climb, 1&3 are still my hotter cylinders. I will still work to improve cooling, but it is acceptable now. EGT sensors are still entirely unreliable. Even with new proper thermocouple connectors. I am going to pull them all at the next oil change and play with the wiring.

Note, on this flight I did not have my nose wheel pant or leg fairing installed (finishing paint).

Power pulled back, temps even
20191007-162227.jpg


Wide open, you can see 2&4 are good, 1&3 are a little hot. But much better thsn before.
20191007-162751.jpg
 
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