FINALLY! My Overheating Cylinder Head Temperature Problem is FIXED!!! What Was the Cause? 

The pic of your airborne troubleshooting session is priceless. I do that with a car frequently because if things go wrong, I can always pull over to the side of the road.

That must be such a relief to have this finally solved. 👏

Wow - The fact that no catastrophic damage was caused by this much advance over quite a bit of time is testament to your discipline in monitoring CHT and backing off power and maintaining full rich when required. It is probably an industry standard that manifold pressure sensors send a higher voltage at higher pressure, but this would have been such a more benign failure mode if it would have failed the other way resulting in no additional advance at low power. I wouldn't want to long term fly a constant speed prop without the manifold pressure sensor as it would negate a lot of the advantage of electronic ignition. But with a fixed pitch prop most of the time engine RPM is a good indicator of engine load. And, maybe not critical when it is off a bit descending at low power with the prop windmilling.

My employer owns a Velocity with Franklin engine that had CHT issues as well. It had dual Light Speed ignition boxes one had bad internal manifold sensor the other had similar issues. Finally got tired of always chasing ignition problems and found 2 magnetos, no issues since.

I had high CHT issues, (slick mags), when I finished building my Vans RV7A. Cyl 2 and 3 temps ran about 430 in climb. My issues ended up being the baffles. The cylinder fins on the Lycoming and the cylinder wall merged on the same plane, if that makes sense, which stopped any airflow at that point. After seeing post on VAF about this, I put in a couple channels to allow air to get by and bingo... took off on a hot summer day here in South Alabama and did a full power climb all the way to 10K. CHT max was now about 375 and with increasing altitude ---> cooler air ---> engine making less power as we climbed the temps were coming down. Yes timing advanced as you were experiencing... like you said could have caused damage! Great video Scott.

Awesome! I’m sure it feels great to have that issue behind you! Great persistence on getting it fully resolved! Fly safe!

Hey Scott, how fortunate you re to be able to diagnose the problems and do a fix. Kudos!

Thank you for this video and explanation. Very well produced and presented. I'm also chasing a persistent CHT issue that has gradually worsened. It's in a canard with a Lightspeed III and an E-Mag. May I ask which EIS you are using?

Great news ! So glad you finally isolated the problem ! Keep flying and keep the videos coming 👍😊

My friend you are amazing. I know that us regular humans would have ever got it fixed and I doubt most shops would have either. Congratulations most informative and entertaining

Good to hear. Now consider this. Your Mag timing was 32° BTD which is much closer to what you stated as the desirable 35° BTD for the elec timing. It seems to me that both ignitions should be timed the same for cruise flight. So maybe that was the reason the mag was at 32°.

Fortunately the AvGas prevented detonation. 50 degrees before TDC? Combustion was half over by time any leverage could be thrown on the crank. Congrats for the hard earned success.

Thanks for the detailed explanation and the perseverance to figure the problem out.

Scott, I hate to be that guy, but get rid of that thing. I have watched you patiently try to solve the issues of the original builder and the design flaws of this aircraft and I can’t be silent any longer. The CG is screwy, the engine cooling is screwy, the flat climb outs and flat finals scare the crap out of me and even attempting to put four people in there is not worth even considering. From your own videos, you cannot make a touch-and-go without first smacking the nosewheel on the ground. My Velocity XL could make consecutive t-and-g’s without ever touching the nosewheel on the runway. That plane is an accident looking for a place to happen. Please, my friend, if you just love canards, find a nice really clean Velocity XL (no affiliation) or XL-5 and find out what a true joy a well-designed canard can be.

Congratulations, Scott! Your tenacity paid off. 😉 So glad you figured it out.

I'm frankly amazed that the engine was so tolerant of crazy timing like that. My old muscle car would never put up with that!

Glad you found the trouble, as a over heating eng is never a good thing. That could led (as I've sure you know) to brunt value's, holes in pistons even bent rods.

I had left the master switch on several times until an older friend told me to leave the rotating beacon or strobes on, like you that has saved a me from a dead battery several times! Enjoy your method of problem solving the over temp on the CHTs. Cheers

What a journey ! thanks for taking us with you , you are a real problem solver❤

Not sure how I found your program, but literally laughed out loud and predicted the timing issues you found right from the start... I could do that because I've been going thru exactly this with my 1966 Corvette with Mechanical Distributor & Vacuum advance and a Carburetor.... ICE Engines all require the same (Correct) static timing (Magneto) and Dynamic timing (EIS) in order to run correctly and the result is incomplete combustion and over heating. It matters not that mine is water cooled Car Engine and yours is an Air Cooled plane engine. Happy Flying.

Finally a fix! I have the same ignition system and same problem. But I already disabled the vacuum advance and it made no difference, bummer. I still suspect the ignition system but it's so hard to check the base timing on a pusher!

Hi Scott, Excellent Work. Thank you so much for sharing your process and the results.

Glad that's fixed. Now for the propeller performance comparison. Thank you for documenting your work.

Just fantastic work Scott! Learned so much watching your videos.

For those of us old school sorts, the manifold pressure sensor/Electronic Ignition System timing has the equivalent functionality of a distributor ignition’s vacuum advance unit. It was acting as if full vacuum advance was applied on top of the base advance even with essentially full atmospheric manifold pressure, I.e. zero vacuum, at full throttle.

Outstanding work. Well done.

Great troubleshooting.👍👏👏

Wow! I sure hope you didn't damage anything.

Great find Scott!

🎉🎉🎉 congratulations!! I’ve been following this saga, and it is good to know what exactly was the cause of all that heat! Thanks for all this classes on airplane maintenance!

Thanks Scott. It just goes to show us all, how important it is to know the fine details of avionics engine technology. Also the ability to measure, monitor and control this.

Scott, assuming you have an Lyc. O-360 or IO-360 the engine data plate should list the magneto (spark) advance. There was an old SB that listed 20 deg as the proper advance, reducing it from 25 deg, in order to prevent detonation in cold weather ops. CHT should be 360 or less. Glad you figured it out. You might want to boroscope the pistons to see if there's any detonation damage.

Scott, thanks for the video, glad you got your CHT's fixed. My Cozy runs 300 330 CHTs but I have been fighting high oil temps. I have a friend with a new EZ still in flight testing and in the couple of years he has had it he has had it he has been unable to safely fly it without the CHTs going way high. I have suggested he check the timing and the carb jetting but it may be his P51 style scoop is way longer than Rutan's plan scoop. He does have a Surefly emag on it and I wonder if that has vacuum advance. I don't remember if it has a vacuum hose on it.

Nice! With the ending temps, you should have a happy engine for a long time. Good call with Savvy data analysis. Fly safe! RD A&P, IA

Nicely done!

Now you can work on cooling drag reduction by restricting cowling airflow, making the plan faster on the same fuel flow!

Those electronic ignition advanced timing feature can be a really sharp double edged sword if not working correctly and sometimes even when they work correctly

Great Scott! I’ve enjoyed learning from your Canard adventures.

What a relief that you know where to look now! This has been an annoying problem. Could you do a tour of your engine bay some time? Do you replace the oil yourself and send the oil in for inspection?

Good stuff 👌 glad you found the culprit heat will destroy most every thing if not cought in time

You definitely need to lower the base timing advance also. But well done.

Great find. I've had nothing but trouble with CDI ignition systems on airplanes. They fail way too often----especially without proper blast cooling on the module. Personally I would go with two mags and eliminate the CDI.

I had a similar cylinder over heat problem on a Cozy MK IV. No changes with timing changes and baffle rework. My problem was resolved with an 18 row oil cooler

I wonder if you should use an endoscope to take a look at the top of the pistons. Just to make sure there was no damage from the extreme timing and heat causing pre ignition? Even with 105 that I would think can happen, you probably would hear it with the load exhaust. I am no airplane mechanic, just an old gear head. Good job finding the problem.

I recommend scoping top ofpiston for loss of material. Too much advance leads to longer exposure to flame and melting or detonation of piston nearest plugs.

You might want to have a look at all kind of cast flanges left in the innards of the cylinder flanges. The air have to be out of there quick.... I had a big difference in cyl temp by cleaning out all those casting flanges left over from the casting process....a drill and insert a chainsaw file ....chain saw files comes in three sizes...one of them will fit perfectly. Heat removal is directly in propotion to heat shredding on aircooled engines....get that air going through all the nocks and crannies of the cylinder and you will shred tons of heat.

Another day, another cowl disassemble. 😊 Seriously the most effective mod , would be a quick lock/release for the engine cowl, to ease working on engine bay. I would have already lost screws, and ripped threads.

Hi Scott. I am a bit late to your troubleshooting issues with your CHT issue, but sounds like you've got the issue sorted now. I know you are a subscriber to Savvy Aviation but I wanted to make sure that you've seen this EAA presentation, it is definitely worth your time to watch the entire thing. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-df1DwFNYFLs.html Mike Busch at Savvy addresses recommended CHT limits, hot CHT's to avoid and includes significant data to describe what to look for and how to troubleshoot the three main issues of high CHT's. Of interest is something he mentioned is a Lycoming service bulletin instruction regarding timing recommendations where they recommend going down from 25 degrees down to 20degrees on certain IO360 models. Not sure which model you have but I thought I would mention Lycoming Service Instruction 1325A to you. 25degrees normally, but 20 degrees recommended for impacted models. Anyone chasing high CHTs should watch Mikes video presentation. BTW, I've watched all your videos on the Cozy...love your content. Fly safe!

Off topic but will you be at Oshkosh this year?

Hi Scott, I imagine that this issue has been quite stressful. Do you enjoy diagnosing and fixing an issue like this or is it just frustrating?

Do you have a spare analogue voltage input on your cockpit display, for that voltage from the EIS that indicates the ignition advance? Put an alarm on it if it exceeds 40° or something. It probably won't tell you much while you've got the manifold pressure sensor disabled but if you ever replace that sensor it would be nice to be able to see what the advance is if you ever suspect it's playing up again.

- Cool. To the max 😀

Haven’t seen a good electronic ignition system for aviation pistons yet. All have problems.

That amount of advance would detonate unless the compression ratio was quite low . My 1980 race engine on a dyno a dizzy swing was performed at full throttle a couple of degrees too much advance would instantly show as a power loss .thinking of my 1960 ford Anglia distributor vacuum advance .. the extra advance was introduced only at low / light throttle settings .. Like an economy spark advance to allow the lean mixture to achieve a complete burn . Great to resurrect memories on my Dyno work .1980 Donnington One litre GT championship champion .

I'm questioning your decision to re-enable the MP sensor advance on the Emag prior to starting the takeoff roll, given that you've just briefed that the advance should basically be zero when at max MP. Could you give us a breakdown of that decision process, please?

Would you ever go back to a 'standard' design aircraft after your Cozy?

I have had the same problem with my Cozy for years and finally gave up. What brand electronic ignition do you have? I have dual lightspeed ignitions, but I don't know how to disable the spark advance to see if it that makes an improvement. Any advice would be appreciated.

How could you run an engine at such crazy advance? You are lucky you did not lunch a piston.

The next time you come to Florida I want you to visit me

I'm no A&P, but is it possible the timing mark being used to set initial timing is incorrect ? If this were a car engine I'd assume the timing mark band on the harmonic balancer had slipped a bit. It seems the timing is off consistently across the entire RPM band right ?

Why don't they let you set a mapping from pressure to degree of advance

Airflow needs to allow the flow / Air to escape from the tunnel.

I believe I’d throw that ignition box away.

What? It's unbelievable that an aircraft engine could be set 5 degrees off proper ignition timing. AND be in service! Somebody got some 'spalain'n to do! Too many experiments, assumptions, and guesses. Glad it finally made sense but Yikes, somethings wrong here.

still using the no where to go runway .

👍👍

Your going to be bored now that you found the problem . What’s your next project 👍🇺🇸

Anyone here working on their own aircraft is also an A&P? Just curious.

This seems strangely backward. Anywhere that I have seen a supplemental timing adjustment added to cars and trucks the default tuning/setting is maximum advance for low load, so it can never advance beyond that baseline, then the timing modifier retards the timing when running at high manifold pressure, high ambient temperature, or a batch of low quality fuel. Even the manual timing adjustment knobs used on old non-electronic carburated trucks for occational heavy towing, still "0" is max advance and then you dial in degrees of spark retard.

I would be replacing sensors every 2 years or 400 hrs. Not worth risking your life upon.

WTF most people probably don't understand this. The fact this engine did not have a major malfunction with that much advance is magic or something, What do you mean, it almost caused damage, it should have caused damage. Okay, I can't hear the engine in IRL but from what I do hear the engine sounds weak to me. You might have to or should tear this engine down if you put hours on the engine with this much advancement. test flight one your time from brake release to rotation is also slow, and the engine is doggy the advance could be the problem for sure. if it were me , I would stop flying this machine until you are sure the engine is running at full power and with proper timing and ignition advancement. You are just asking for a power-off forced landing. There is no need for that.

Wow, you had the exact opposite issue a friend of mine had with his 1986 Dodge Ramcharger 4x4 speed manual when it comes to ignition timing.... You had so much timing, and the engine still ran. My friend's Chrysler 318 had its ignition timing so far retarded, it some how ran, though his engine also had a TON of vacuum leaks and a horribly out of tune Edelbrock carb. and it all magically equaled a running engine... Barely running, but it did run after a long start. Once the vacuum leaks were all gone, I got the carb. cleaned up and adjusted, I found how badly out of time the ignition was as the last thing in the running issues. Now, hot or cold, you can go out to his Ramcharger, pump the throttle twice and hit the key, it fires right up. Went from struggling to do 50 miles per hour to doing 70 even with 35 inch tires. It is strange how some engines, if the ignition timing is off for even a short time, they destroy themselves, and other engines can be WAY out of spec and still (mostly) run. Also of note, if your ignition timing is too far retarded, it too, can cause some overheating issues under certain conditions. I have seen that happen as well.