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Surefly electronic ignition

The point I was trying to make, is that a partial power climb can benefit from a more conservative advance. I know that SDS has an LOP switch for cruise, which means that you have a more conservative advance curve until the pilot determines cruise configuration and switches to cruise mode. I was thinking that this can be automated, but I like the idea of pilot control.

Perhaps this idea is more about the limitations of competing systems than the SDS system.

V

Yes, the other EIs have no way to determine when you are LOP where more advance is required to achieve PCP at the optimal crank angle so as you say, they often have too much advance ROP to have optimized timing LOP.

We just had a customer switch from one other EI brand to the CPI-2 because he was fighting high CHTs ever since he installed it. His CHTs dropped substantially and he picked up 6 knots I believe showing that the canned curves were too far advanced, costing power and giving him high CHTs. This is a common complaint we hear.
 
Partial Power Climb

The point I was trying to make, is that a partial power climb can benefit from a more conservative advance. I know that SDS has an LOP switch for cruise, which means that you have a more conservative advance curve until the pilot determines cruise configuration and switches to cruise mode. I was thinking that this can be automated, but I like the idea of pilot control.

Perhaps this idea is more about the limitations of competing systems than the SDS system.

V

I'm not sure why you would want to do a partial power climb, but one way to achieve what you're looking for is to do a full throttle LOP climb. This will reduce power and have a similar effect to retarding the timing since the LOP mixture burns slower - a very effective way to reduce CHT's...

Skylor
 
I agree with Skylor. If you have a CS prop, leave it WOT, pull back the RPM a bunch and go LOP. Big reduction in CHTs. Radical as it sounds, we've have a few customers doing it for years now. No issues.
 
Interesting technique, I'll give it a try. I have checked with the IO-540 operations manual, and I can go as low as 2200 RPM at sea level and LOP for a modest climb.

V
 
Little help, here

Very interesting guys regarding LOP climb . This is so contrary to the classic enrichment cooling "wisdom", could you expound upon this subtopic? Not doubting you but I need a full understanding to suppress my OCD and feed my geek side. Thanks.
 
Very interesting guys regarding LOP climb . This is so contrary to the classic enrichment cooling "wisdom", could you expound upon this subtopic? Not doubting you but I need a full understanding to suppress my OCD and feed my geek side. Thanks.

You can cool with excess air or excess fuel. The air is cheaper.

Pull rpm back to 2400 and once you're below 25 inches MAP, you should be below 75% power.
 
I agree with Skylor. If you have a CS prop, leave it WOT, pull back the RPM a bunch and go LOP. Big reduction in CHTs. Radical as it sounds, we've have a few customers doing it for years now. No issues.

Sounds like a reduction in power equals lower CHT... no rocket science there.

Personally I don't feel like 'lugging' the engine at lower RPM's and high MP's, kinda like climbing a hill in fifth gear.
 
Of course, but

You can cool with excess air or excess fuel. The air is cheaper.

Pull rpm back to 2400 and once you're below 25 inches MAP, you should be below 75% power.

Come on, I'm that smart. Sorry. I should have asked a better question.

Playing on the left side of Phi (Stoich), isn't without consequences. There is excess oxidizer at temps that are trying hard to promote a reaction. Most anything can then become (part of) the fuel reactant. Is the associated metallurgical wear below the life cycle of the cylinder, i.e. by the time it's an issue, it's time for new jugs anyway? Nothing is completely free. Physics demands its part of the dues.
 
Come on, I'm that smart. Sorry. I should have asked a better question.

Playing on the left side of Phi (Stoich), isn't without consequences. There is excess oxidizer at temps that are trying hard to promote a reaction. Most anything can then become (part of) the fuel reactant. Is the associated metallurgical wear below the life cycle of the cylinder, i.e. by the time it's an issue, it's time for new jugs anyway? Nothing is completely free. Physics demands its part of the dues.

Concerned about excess oxidizer? Consider the diesel.

Caution: Thread drift in progress ;)
 
Aye, thread drift, so I won't contribute any more here. Someone can start a thread on the consequences of LOP operation on engine life.
 
Aye, thread drift, so I won't contribute any more here. Someone can start a thread on the consequences of LOP operation on engine life.

Right - there's plenty of data on that already, going back about 70 years I believe. Wasn't it Doolittle that started that?
 
Actually I had a nice conversation with Scott, who works in the industrial gas turbine world where long term exposure to excess oxidizer at high temperatures is a concern.

As usual, it's about perspective.
 
Lots of entertaining replies. I won't necessarily use the word interesting. I did have a very interesting/informative PM conversation regarding such.

Sounds like a reduction in power equals lower CHT... no rocket science there.
If you only had to design for one set of parameters/optimize operations for one set of conditions, anyone could be an engineer. If someone would like to discuss actual rocket engine design, let me know. It's been a long time but I can still go there.

Right - there's plenty of data on that already, going back about 70 years I believe. Wasn't it Doolittle that started that?
Would love to see all of the the data. Lots of anecdotal stuff through the decades. More later.

Back to the point. Someone was asking about a partial power climb, associated advance, etc.. LOP ops are nothing new, obviously. There is a lot of operational experience there. A LOP climb seems to add component life risks; high load and low(er) cooling air flow. Yes, I’m aware that moving away from stoichiometry will cool the flame. I’ll state my concerns/interests again.

On the right side/rich side of stoichiometry (phi), there will be enrichment cooling. Yes, fuel is infinitely more expensive than air. Temps come down. NOx formation comes down, CO and CO2 remain fairly flat until you move further away from phi. Hydrocarbon based emissions start to increase. All considered, you have a relatively happy engine from a metallurgical standpoint.

Look at the other side of phi. As mentioned, the presence of excess oxidizer at those conditions isn’t without consequences. Even though NOx is mostly thermally driven and temps are coming down, NOx emissions go up initially due to the lack of HCs to react with. The excess oxidizer is at high temp conditions which helps promote continued, accelerated reactions. Other available materials become fuel sources. There’s no way that metal oxidation and associated wear isn’t occurring. Best guess would be vulnerable exhaust valves/seats. My question/guess is that other “lifing” factors overshadow these effects. Would like to hear from someone who actually knows/has data.

Yes, Doolittle is credited long ago with extending range with LOP ops. Does anyone know if he climbed LOP when conditions make the engine metallugy more vulnerable? Optimizing operations to complete a mission isn't the same as optimizing engine life and I assume most of us don't have the maintenance budget the Army Air Corp had.

One thing I learned from my PM conversation, Continental embraces LOP ops while Lycoming does not. I have no idea if this point is related but Continental jugs have a reputation, right or wrong, of not making quoted design life; especially their larger displacement engines. If anyone knows the actual causality or other related facts, please say something.

My build will have EFI and EI. I hope to be cruising again LOP someday if I can ever finish this %$%#@*! frustrating project. Will i climb LOP? Not without a lot more data or shared expense. One thing remains consistent. Despite a lot of complaining, fuel is still the cheapest thing we put into our aircraft. Here in the states, at least.

There. Flame away, boys.
 
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Old post, new question (I think). I have a SureFly ignition on my left mag position, and a Slick on the right side on my O-360-A1A powered RV4 (25* timing). I have currently set my SureFly dip switch for 30*, but timed my start timing to 5* ATDC, with variable timing (I have a light weight carbon fiber prop), so I believe that my non-advanced post-start timing will be 25* I’m concerned with overly advanced timing for my normal flying - local flying, acro, formation. What advance limit am I getting in this configuration - 33*? And at what MP? If I eliminate the MP line and configure the SureFly to fixed timing with my advance set to 30*, and start timing set to 5* ATDC, will I still get 25* full time after the engine is running? From what I read here, this seems like a conservative answer for engine stress. I’m not that concerned about cross country cruise efficiency, since I don’t do a lot of that.

I am carbureted - makes a difference for LOP ops I think.

Thanks
 
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Old post, new question (I think). I have a SureFly ignition on my left mag position, and a Slick on the right side on my O-360-A1A powered RV4 (25* timing). I have currently set my SureFly dip switch for 30*, but timed my start timing to 5* ATDC, with variable timing (I have a light weight carbon fiber prop), so I believe that my non-advanced post-start timing will be 25* I’m concerned with overly advanced timing for my normal flying - local flying, acro, formation. What advance limit am I getting in this configuration - 33*? And at what MP? If I eliminate the MP line and configure the SureFly to fixed timing with my advance set to 30*, and start timing set to 5* ATDC, will I still get 25* full time after the engine is running? From what I read here, this seems like a conservative answer for engine stress. I’m not that concerned about cross country cruise efficiency, since I don’t do a lot of that.

I am carbureted - makes a difference for LOP ops I think.

Thanks

Is this what you would do with a magneto if you could?

Installed per the manual, the Surefly SIM fires very accurately at TDC, during the start. If you are able to find 5° ATDC, I'm sure you can find TDC. There is no slop like you would have in a magneto impulse coupler. If timed correctly, you will not have any problem starting with the Surefly.

I doubt Surefly would recommend your installation, but give Surefly a call. Don't be swayed by opinions from people using a different system who did not design the Surefly. I see your logic, but you are stepping way out on your own with no data supporting your installation.

Do you have an engine monitor? If you pay close attention to your CHT's, you will see any "stress." If you are set up for variable timing, I doubt you will have much advance past base timing, during the flying you described. The SIM will not start advancing until you get the manifold pressure below 25". If you are low altitude, with the throttle pulled back, you might get some advance. But, you are at a low power setting and well outside the detonation region. If it is a concern, run it in fixed timing as you will get very little advantage in variable timing mode. It'll run just like a magneto in fixed timing.

I have an RV6 with dual SIM's, in variable timing mode, on a high compression IO-360. I flight a lot of formation below 4000' without any problems.
 
Old post, new question (I think). I have a SureFly ignition on my left mag position, and a Slick on the right side on my O-360-A1A powered RV4 (25* timing). I have currently set my SureFly dip switch for 30*, but timed my start timing to 5* ATDC, with variable timing (I have a light weight carbon fiber prop), so I believe that my non-advanced post-start timing will be 25*

Correct.

What advance limit am I getting in this configuration - 33*? And at what MP?

Surefly does not appear to currently publish a complete advance schedule. However, the available literature says "up to 38", so your clocked installation should max at 33.

If I eliminate the MP line and configure the SureFly to fixed timing with my advance set to 30*, and start timing set to 5* ATDC, will I still get 25* full time after the engine is running?

Yes.

From what I read here, this seems like a conservative answer for engine stress. I’m not that concerned about cross country cruise efficiency, since I don’t do a lot of that.

It is.

I am carbureted - makes a difference for LOP ops I think.

Only in the context of mixture distribution.
 
I set my start timing to 5* ATDC to prevent a kick back during start. I’m using a light weight carbon fiber Sensenich prop, and did experience kick backs twice with my previous RV8 with a light weight prop and two Pmags. The second one broke my starter ring gear. Pmag had a software change that automatically set the start timing to 4*ATDC, which seemed to fix the problem. With my present RV4 setup, the engine starts like a car hot or cold at 5*ATDC, so no problem there. I would just like to know what the advance curve looks like. It sounds like advance begins when below 25”, but how is that influenced by RPM?

You’re right - I need to ask a SureFly tech these questions.
 
Pmag had a software change that automatically set the start timing to 4*ATDC, which seemed to fix the problem....
You’re right - I need to ask a SureFly tech these questions.

Scott, we can safely assume the SureFly incorporates a start retard, as it darn sure doesn't use 25 BTDC at cranking speed. The question here is "How much retard?", i.e the actual ignition timing at 200 RPM or less. If, like the EMag product, the SureFly is programmed to fire after TDC at a typical cranking RPM, your clocking approach may not be necessary.
 
A couple of things to consider. Some have described the advance curve as aggressive but given that it’s certified in a wide variety of aircraft it’s not that aggressive. The 38 degrees often quoted is not correct unless you run your engine past 2700 RPM and below 21” manifold pressure. In the flying you describe I suspect you are at 2400 to 2500 RPM which limits it more. It will not advance at all above 25” manifold pressure. I will attach the closest thing I can find to a accurate advance table. As far as how you have set it up do you know where the PMag was firing at start before the software change? In a previous aircraft I had dual ignitions firing at TDC with no issues and a lightweight prop.
 

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A couple of things to consider. Some have described the advance curve as aggressive but given that it’s certified in a wide variety of aircraft it’s not that aggressive.

True only if (1) that wide variety of aircraft are all powered with an IO-390D, and (2) you happen to know the proprietary advance schedule Lycoming says they developed for their Lycoming-branded versions of the ignition. All other approvals are fixed timing.

See SI 1443R.

IF the advance schedule remains as previously published, a max of 38 BTDC is not super aggressive for a parallel valve, and of course it does not run there all the time. However, one size does not fit all. My own data says going much more than 30 BTDC has little benefit with an angle valve...and the old chart suggested the same max of 38, even with base timing set at 20.

I like the SureFly. It absolutely nails its intended market, a bolt-on replacement for a Slick in the certified fleet, and it offers options for the rest of the market. I would like to know more about the current variable timing schedule.
 
A couple of things to consider. Some have described the advance curve as aggressive but given that it’s certified in a wide variety of aircraft it’s not that aggressive. The 38 degrees often quoted is not correct unless you run your engine past 2700 RPM and below 21” manifold pressure. In the flying you describe I suspect you are at 2400 to 2500 RPM which limits it more. It will not advance at all above 25” manifold pressure. I will attach the closest thing I can find to a accurate advance table. As far as how you have set it up do you know where the PMag was firing at start before the software change? In a previous aircraft I had dual ignitions firing at TDC with no issues and a lightweight prop.

That advance table was produced the year the company was formed as a marketing illustration of what a variable timed ignition will look like. I doubt that the curve remained the same while the unit was developed.

If you are getting kickback during start with an EIS, you need to check your battery and connections. Specifically, the voltage drop at the starter when it is engaged. If the start is dragging the voltage down outside the limits of the EIS then it may fire early as the unit shuts down.
 
Scott, we can safely assume the SureFly incorporates a start retard, as it darn sure doesn't use 25 BTDC at cranking speed. The question here is "How much retard?", i.e the actual ignition timing at 200 RPM or less. If, like the EMag product, the SureFly is programmed to fire after TDC at a typical cranking RPM, your clocking approach may not be necessary.

Dan - the Surefly isn’t programmed to retard the spark to some pre-programmed setting during engine start like the Pmag. It will fire at whatever timing you have set when timing the mag. It times just like a Slick, turning it on the pad until you get the light with the crank set where you want it. After the engine starts it changes to the run setting that you have set using the dip switches, such as 25*. I think this timing transition happens around 400 RPM. The install manual says to set the timing to fire at TDC. I was concern because of a lack of flywheel affect with my light prop and my experience with kick back on my last Pmagged airplane. It might not be necessary, but if I am truly getting a 25* run setting after start with my mag timed to fire 5* ATDC during the start cycle and dip switch set to 30*, then it should be working the way I envisioned it would. I spoke with a SureFly tech rep before installing it, but didn’t ask him those questions. I am merely fooling the SureFly to operate the way it is supposed to, but at a setting that is 5* later - across the board - than my settings would normally operate had I timed it at TDC as specified in the install manual.

EmagAir had several kickback events with customers prior to the software change that retarded the start timing by 4*. I had kickback with my dual Pmag setup on my RV8, and I’m pretty sure it wasn’t due to a weak battery, or connections. I had an EarthX battery and a brand new Skytech starter. It would spin that engine very fast during engine start. In fact I was concerned that it was spinning the engine so fast that maybe it was going past the start circuit kick out timing (400 RPM) and getting into the run timing during engine start. The Hartzell rep assured me that the starter wasn’t capable of more than about 200-220 RPM no matter what the input voltage was. The 4* retard fixed it for Emag/Pmag. What I have done with my SureFly is essentially the same thing, manually. Maybe this isn’t right. I intend to find out tomorrow with a phone call. I have been flying it this way for one year/100 hours. I just want to make sure I’m not stressing my engine. All temps run cool, too cool actually this time of year, and it seems pretty smooth. All this concern is probably a byproduct of COVID boredom, but I still want to understand the way it works.
 
Surely

I replaced my left mag with a Surefly unit and I was well pleased with the simplicity of installation and how promptly it starts now.
 
I put a SureFly on an angle-valve IO-360 and set it up for fixed-timing at the listed 25*. No manifold pressure line attached. The reason for this was after communicating with experienced people in the field it was found angle-valve engines don't respond as favorably or innocuously to advance timing curves like the more typical parallel valve Lycoming. I think Dan was more or less alluding to the same idea above (but I haven't ever been or propose to be as technically deep as Dan). Whether at altitude or coyote-chasing levels my angle-valve stays well behaved. When I swapped a mag out for a SureFly I was looking for reliability and easy hot starting more than anything. That's what I got.

I also have an RV with dual P-Mags and with the mild-curve jumper in place and I have been very satisfied with that. The SureFly is bulkier and more mag-esque and doesn't have a built-in dynamo to keep the sparks going without battery power like the P-Mag. They each have their place. As do a good quality set of CMI/Bendix mags (sacrilege!). I have been happy with all of them. You may note I leave out mention of Slicks, which in my personal opinion are **** throw-away at 500 hours no matter the model.
 
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Two examples, return flights from OSH, 2018 and 2019. It's about a four hour run for me, so I usually schedule some kind of experiment so I won't get too bored. The ignition I'm using stores two complete, independent ignition maps. For this sort of test I load one at fixed 23 BTDC, and another with the experimental schedule. Back and forth is just the flip of a switch.

A little lean of peak at 9500, a common RV cruise configuration. 28 BTDC vs 23 BTDC, same flight, back to back. Note times, CHTs, oil temps, and speeds. BTW, these temperatures were all taken with the cowl flap closed, so cooling exit area was down around 30 sq in, about half a standard RV-8.

28%20vs%2023.jpg


Again a bit LOP, this time at 16,500 feet and 23 vs 35 BTDC, the kind of advanced timing typical at this altitude (i.e. manifold pressure) for several of the EIs with mystery maps. Again note CHTs and oil temps vs speeds.

23%20vs%2035%20OSH%202018.jpg


The higher CHTs correspond to high peak in-cylinder pressure. It's significant additional engine stress for no gain, and quite contrary to GAMI-APS philosophy, for those who respect George Braly, John Deacon, et al.
 
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I am curious why the fuel pressure is so different between the two pics. The actual fuel flow is virtually the same.
G
 
Wow! That was the kind of actual data I was hoping for. I will be removing my manifold pressure line from my SIM and reconfiguring for fixed timing. The only question remaining for me is will I get a fixed 25* timing the way I have it set - 30* fixed dip switching, timed to 5*ATDC. I like the way this setup starts the engine. Bette to me anyway, than when I had my timing set at TDC (with a 25* dip switch setting). SureFly tech to answer this question, I hope.
 
Thanks Dan -- What do the numbers look like if the RPM is the same (2nd set of pictures -- 2430 vs 2530).
 
I spoke with a SureFly tech rep today about my setup with my SIM/Slick mag on my O-360 RV4, namely start timing set 5*ATDC, and dip switch set to 30* (25* engine). His response - some of that is OK, and will work like I think it will - but only partially. With a wasted spark EI system, when I set my timing to 5* ATDC, that also influences the wasted spark on the opposite cylinder. That wasted spark is supposed to occur at TDC on the exhaust stroke of the opposite cylinder when the exhaust valve is fully open. When I fool it to fire 5* later, that wasted spark is occurring after the exhaust valve is starting to close. How much is it closed? Who knows, but it is not the way they recommend operating it, and granted, that modification of the recommended setup is only occurring during the start cycle because the run cycle is still 25* actually. But, he told me they have experienced zero reported incidence of engine start kickback when installed as designed, and they have plenty of light weight props in the field.
Today I reconfigured my SIM to 25*, fixed timing (manifold pressure port disconnected and capped). One other thing he asked me that I hadn’t considered was how I am timing my ignition. I timed it just like I would time a Slick. He said there is quite a bit of slop in the gearing in the engine and in a traditional mag that doesn’t exist in the SureFly SIM - it is very precise. He recommended finding TDC on cylinder #1 compression stroke using a dial indicator riding on the piston to find the exact TDC. Using the marks on the flywheel will get me in the ball park and is OK for an equally inaccurate Slick, but that should be fine tuned to the actual accurate piston TDC. Maybe others do it this way normally, I just never have. That’s part of my task tomorrow before test flying to see if I can notice any difference with these changes.
Bottom line - I wouldn’t recommend setting up your SIM the way I did it with retarded start timing. Install it the way the factory recommends.
 
Scott,
DO NOT CAP THE MP PORT! It will seal the manifold pressure sensor which may throw a fault to the unit. A cap could pressurize or depressurize the manifold pressure sensor, thereby making the unit think the MP is faulty. It will result in a rapid flashing LED. Let it breathe.
 
OK, I won’t cap it. My install manual says to do that, but it’s a year old. Checking the online install manual - no mention of capping it...... THANKS for the heads up, Jimmy and George.
 
With a wasted spark EI system, when I set my timing to 5* ATDC, that also influences the wasted spark on the opposite cylinder. That wasted spark is supposed to occur at TDC on the exhaust stroke of the opposite cylinder when the exhaust valve is fully open.

It was fully open back around 100 degrees before TDC.

When I fool it to fire 5* later, that wasted spark is occurring after the exhaust valve is starting to close. How much is it closed? Who knows...

BY TDC, it's been closing for quite a while, but won't fully close until well after TDC. The TDC overlap period, during which the intake valve and the exhaust valve are partially open at the same time, is (ballpark) 30 to 50 degrees of crank rotation for a low speed engine like our trusty Lycoming. The actual number quoted depends on the arbitrary valve lift point picked to designate open and closed. In the context of spark timing at cranking speeds, the exact number doesn't matter much, because it's a lot more than the 5 degrees you proposed. Next time you have the valve covers off, rock the crank around #1 TDC and watch the valve action on #2.

FWIW, you know EMag incorporated a cranking retard. As an experiment I clocked the EDIS on my 390 by 10 degrees for a few years. The typical EDIS module fires a few degrees before TDC, so 10 degree clocking put spark delivery (ballpark) about 6 ATDC. Made for very smooth starts. I've since returned it to a TDC set, as I have a metal Hartzell with lots of inertia.

One other thing he asked me that I hadn’t considered was how I am timing my ignition. I timed it just like I would time a Slick. He said there is quite a bit of slop in the gearing in the engine and in a traditional mag that doesn’t exist in the SureFly SIM - it is very precise. He recommended finding TDC on cylinder #1 compression stroke using a dial indicator riding on the piston to find the exact TDC.

A dial indicator is a fine idea to check the location of the flywheel's TDC mark....once.

Slick points are on the main shaft. As such, internal Slick gearing has no effect when setting timing. The gearing drives the distributor rotor.

The engine's gear freeplay is the same for any ignition driven from the accessory case. Using a dial indicator to find TDC when setting the timing will not in itself eliminate the slack. Doing so simply requires good procedure, i.e. rotating the crank in the normal direction of rotation to arrive at TDC, or to trigger a buzz box.
 
Thanks Dan -- What do the numbers look like if the RPM is the same (2nd set of pictures -- 2430 vs 2530).

Can't find the 23/2430 photo, sorry. The speed difference would be less of course, but still faster at 23 degrees. In fairness, at this altitude and mixture, an advance of perhaps 28 would have been fastest by a wee bit. See Marvin McGraw's past posts with detailed variable timing inflight data for the 390.

I was playing around with a few things here.

Over in the Bonanza/GAMI/APS world, the LOP procedure has the pilot setting mixture, then adding MP to regain the lost speed. Can't do that with a 390 above 8000 or so (no turbo), but we can add RPM.

Cooling demand is proportional to mass flow, i.e. RPM. Note that using the mild timing, I can turn up the RPM, yet maintain CHT and oil temps well below the advanced timing example.

The result here is a fuel burn about 4% higher in return for speed 3% higher, not a bad trade in the world of internal combustion. Note groundspeed is over 200 knots at 7.8 gph; the tailwind and settings would get me home non-stop quickly, with range to spare. The subsequent switch to 35 degree timing pushed CHT up so far I never went to 2530.

Reminder...this is angle valve stuff.
 
Ignition and plugs should not matter. Dan’s engine is I believe a angle valve that responds quite differently to advancing the timing.
 
Crickets eh?

Ok, good for the goose, good for the gander.

Do you have an engine monitor? If you pay close attention to your CHT's, you will see any "stress."

Higher CHT, sure. But that's not the only stress of interest.

I have an RV6 with dual SIM's, in variable timing mode, on a high compression IO-360. I flight a lot of formation below 4000' without any problems.

May I ask which 360 and propeller you're using? I ask because high compression 360's and 370's without crank pendulums and with ignition advance are generally subject to propeller restrictions...for good reason.
 
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