Personally, I’d be unhappy flying my Lancair 320 Mk I (Lycoming IO) without knowing all four CHTs. Reading the thread, you have only one EGT reading and one CHT (cylinder 4)? As huv pointed out, that’s very little information to go on…
Jenny
For the lowly stressed IO320 we may be overthinking this
Agree an engine analyser might give some early warning, but your mag check and regular maintenance will cover 99% of eventualities.
The best recipe for engine life is regular usage:)
I’m deffo not a fan of overthinking either, Robert! 
However, the Lancair 320s/360s do have known issues with high CHTs due (amongst other things) to the small air inlets. For that reason, I like to be able to monitor all four CHTs.
Regarding engine management in general, and no doubt someone will correct if I’m wrong, one EGT + CHT reading is not much to go on?
@DBO may have long disappeared
Not monitoring EGT/CHT on all cylinders is fine all the time everything works, and then it isn’t… like here where having the EGT almost certainly saved a disaster. This is another example where an engine monitor in your primary field of view will give you the earliest possible warning, whereas an EGT gauge somewhere in the corner won’t get noticed.
Am basing my comment on organisations that run NA and turbo charged engines thousand of hours, some with multi probe monitors, some with single probe. The SOPs tend to be MP/RPM/FF driven, with the only EGT type limitation being the TIT for the turbocharged engines. The SOP power settings are probably ROP. Interestingly, Richard Collins (around 30,000 hours in piston GA) was not a convert to LOP.
Engines run to TBO plus allowed extension with some minor cylinder work on the way. If it weren’t for the maintenance programme rules the engines would run well beyond TBO.
Whether this is a result of the SOP, or the fact these engines are used regularly and consistently, am not sure, but my vote is for the latter. I do think there is a tendency amongst private owners to worship at the altar of multi probe engine monitors and LOP power settings, which doesn’t seem to be the case in commercial operations.
These are not turbo compound Super Constellations requiring an engineer with multi probe oscilloscopes :)
When I fed a twin I did have engine monitors and flew LOP etc, I think I and the engines would have been happier at 75% ROP and 180KTAS, instead of fiddling around at 155 KTAS to save a few dozen litres per hour.
@JoJo the SOP for your type presumably calls for relatively high speed cruise climb (130 KIAS), which should keep CHTs in check. It also is more efficient. Quite a few close cowled high performance SEPs require a climb speed well above Vy to keep engines happy.
One more comment about EGT absolute number. There is no limitation on that one. As Peter previously wrote this is just an approximation of very short and high pulses. We should not pay too much attention on that reading.
In fact – what researches show – temperature of our exhaust valve does not follow EGT number. It follows CHT.
So it is in fact much better for cylinder/valve to have for example EGT 1500-1550F – 10Deg lean of peak with CHT 350 than 1400-1450 and CHT 380F which is slightly rich of peak.
50F rich of peak is the worst place to be due to highest ICP (inter cylinder pressure) so unless you really need it (high altitude climbs in normally aspirated engines) we should avoid it by being leaner or richer from that.
Of course single probe gauge tells us nothing except just one cylinder where the others may be all over the whole spectrum without any control.
TIT is a different thing with a limiting number but I have some doubt about it as well.
Happy to hear your opinion:
My case – TSIO 360.
I usually climb at 75% about 150-200F rich of peak on the leanest cylinder. TIT about 1400F on JPI, 1200-1250F on my primary TIT.
At that setting, at night you can clearly see an exhaust and turbo assembly glowing red under left and right cowling – visible via the top ventilation bracket on the engine nacells.
That’s normal. I saw it in couple other Senecas. I’m pretty sure it happens in all aircrafts but we just can’t see it as in Seneca you have that vent just above your turbo.
Next – when I level off – I set 55% – I never cruise higher than that. Red levers are pulled further – lean of peak on 4 cylinders out of 6 (my gami spread is horrible) the TIT rises to 1550F (JPI) on both engines more or less the same, but the glow disappears.
So – which conditions are now harder on my turbos? 1400F 75% power – glowing red, or 1550F 55% power – dark.
I am pretty sure that higher TIT and lower power are much easier for turbo as there is much less “total” heat produced by the engine, so in fact the whole assembly is much cooler and only small TIT probe which is almost nil mass is able to keep the higher reading.
Yes the lower power is easier on the turbo because turbo RPM is lower. Also exhaust pressure upstream is lower.
There is however a limiting temp on most turbos, is that the case in yours? Regardless of power, that should not be exceeded except for short periods.
It is not just a matter of total heat. Temperature also matters and probe indication is a good proxy of what turbo and exhaust parts see.
Hello,
First of all I would like to thank you for your comments. In the meantime I did some further experimenting and even discussed the issue with Mike Bush during an AOPA Blog. Although I did not install a full engine monitor I found a good working K-type sensor and built that in de Cyl. 3 exhaust pipe. So now I’m able to monitor both cylinder 3 and 4 and guess what, exactly the same behaviour. I also checked the sensors themselves by connecting them to a millivolt meter and comparing the outcome with a conversion table millivolt to Fahrenheit. Only minor differences were found.
Now to the problem itself. Mike Bush clearly explains the relationship between EGT and CHT. Advancing the ignition timing lowers the EGT and raises the CHT. This can also be simulated by people having a time controllable electronic ignition. The explanation is as follows: Advancing the ignition gives the fuel – air mixture more time to burn and transfer the heat into propulsion energy to the piston. This also raises CHT. Retarding ignition timing gives an higher EGT as the transfer of heat to energy is not complete and hence lowers the CHT. One might say: too much energy is leaving the exhaust pipe.
All be it a nice theory it does not solve my issue. The IO 360 was new when I installed it on my Lancair and it seems safe to assume, that the ignition timing was set at 25 degrees. As a matter of fact the Lycoming test report confirms this. Unfortunately it does not show an EGT value; obviously Lycoming does not find this interesting. During my nearly twenty years of flying the timing was checked on a regular basis and nothing was wrong. The engine always produced EGT of 1.400 F and CHT of 350 F at 65% of power and 9,3 GPH.
Only now after overhaul of the right Slick Magnet and adjusting both magneto’s at 25 degrees the word looks different: EGT is 1.400 F, CHT is 330 at 65 % of power BUT AT 10 GPH! In other words: Energy is blowing out of the exhaust pipe and the quest for a solution continues. I’m even considering to install an electronic ignition and see what comes out. An engine monitor could be an useful addition as well, but now being able to monitor both cylinder 3 and 4 it can hardly be expected that this would shed new light on the issue.
Finally a word to the CHT, which never has been an issue on my Lancair. Mike Bush advises to keep this between 350 and 400 degrees F in order to avoid lead deposits on the valve stems and consequently sticking valves. In addition is would be helpful to me if Lycoming IO 360 owners could give me some more information regarding power settings, fuel-flow and EGT / CHT temperatures. Also the values they see at full power take-off. Considering the facts that most of you have these nice engine monitors it should be easy to produce these figures.
Regards,
Dave
Antonio wrote:
is that the case in yours?
Yes. It is 1650F
Dbo wrote:
EGT is 1.400 F, CHT is 330 at 65 % of power BUT AT 10 GPH!
Do no worry about your EGT. If it’s 1400 or 1500 makes no difference for your engine. You will NOT burn any valves. It’s a myth.
Valves/valve stems follow CHT, not EGT.
Just lean to your usual fuel flow value and then check CHT. If it’s the same as before mag overhaul then forget about this “problem”.
I get the intellectual challenge of wanting to understand what’s happening here, but other than that, aren’t you worrying rather a lot about not much? You may be burning a bit more fuel, but so what if you’re having a good time doing it? On the plus side you have a very good CHT temperature – at least on the two cylinders you can monitor. I sometimes get up to 400 F during takeoff, especially on hot days, but that’s not a value I’d be happy with in cruise, whatever Mr Mike Bush advises 
I’m typically around 330 on all 4 cylinders at 2300 / 23 and EGT around 1250, FF 32 l/h. I have electronic ignition (LASAR). Mine is 320 IO so not comparable with yours. Also, these being experimental aircraft, there may be all sorts of mods on one model (I have enlarged my air inlets) which may invalidate a direct comparison with another model, even with the same engine up front.
