Assuming the monitoring equipment is accurate. The spread between EGTs should no more than 100f. The spread between CHT's should be no more than 25f.
Assuming the monitoring equipment is accurate. The spread between EGTs should no more than 100f. The spread between CHT's should be no more than 25f.
depends on the type of baffling installed in the baron. Aztec baffling is pretty universally mediocre. Barons can range from stellar to horrible.Sounds like the Baron has much better cooling than the Aztec.
They are Gamis. My A&P IA who did the prebuy asked me if I wanted to have the injectors cleaned, although when he said that while some folks swear by it, others say there is no need to clean them I opted to save the money for some other items I wanted to get ahead on. Sounds like I may want to try having them cleaned now.If it gets rough leaning, you might want to clean the injectors. They're Gamis, right? If not you might want to swap out for some. Also check the baffling. I don't know how Barons do - Lance is the expert in your case.
They are Gamis. My A&P IA who did the prebuy asked me if I wanted to have the injectors cleaned, although when he said that while some folks swear by it, others say there is no need to clean them I opted to save the money for some other items I wanted to get ahead on. Sounds like I may want to try having them cleaned now.
Here's my perspective, and I probably have a bit more knowledge on it than the average A&P.
Mechanical injectors do get clogged over time. A certain amount of this is due to the poor filtration by the gascolator (I think on the order of 100-250 microns), and some of it is also due to the fuel itself. Typically, the clogging happens slowly such that you won't notice the difference until you have some weird little problem. GAMIjectors that won't lean out very well, weird noises (especially at high power) and the other big clue is when you have a fuel flow gauge (mechanical pressure-driven) that reads way, way high.
When I bought my Aztec, my injectors were so clogged that I got people making comments about the noise the engine was making. It still was smooth overall, but sounded bad on takeoff. My A&P insisted that there was no reason to clean the injectors - after all, he'd maintained that airplane for 8 years and it never did it, and the fact that the fuel flow gauge was reading way off the chart was obviously a faulty gauge. Remember, these gauges read on pressure, and a clogged injector will raise pressure (more pressure = more indicated flow).
Finally I said "Screw this" and cleaned the injectors myself one day (under supervision, of course). The Hoppes #9 turned BLACK within a matter of minutes, and I must have gained 50 HP out of that engine. Sounded better, better power, leaned better. Oh, and the fuel flow gauge now read a bit lower than the left engine. When I cleaned the injectors on the left engine (which were much better off) then they both came right in line with eachother.
When you're running ROP, you probably won't notice these issues. Of course, you also are more likely to end up with a cylinder clogged (leaned out) into a bad zone. It will still probably be smooth. When you're running LOP, you notice it more since now that lean cylinder will cut out and become rough.
While I think that most planes probably don't need the injectors clogged every 100 hours as is recommended, I think that it's a cheap and easy thing to do while you're doing your annual. It ends up being preventative maintenance that helps keep your engines running right. I just have 6 little glass bottles (in my case I use Starbucks Frappuccino bottles - perfect size) and I dump each injector in one. This way I make sure I put the injectors back in the same engine.
The counter point to this is that if you over-torque the injectors you do risk having cracks in the head or cracked/kinked fuel lines. I personally view this as a very small risk.
Use the last cylinder to peak as you are leaning as the one you set up with because it will be the one that gets hurt if you have it to close to peak or slightly rich with higher power settings as the cylinders that peaked first are on the LOP side.
Herein lies the problem if your FF's for each cylinder aren't really close. You set the last to peak for 25 degrees or so LOP and the first to peak are now so lean that the cylinders are starving. They will not be damaged, but the engine may be rough running.
In a perfect world all cylinders will peak at the same time and then you can just pull the mixture until you feel the plane slow down and you are LOP. Then a little fiddling with the mixture to get them where you want and you are good to go.
This is exactly why I can't run LOP at higher power settings -- to get my richest cylinder (#2) safely LOP, I've got to lean so far that my leanest (#3) isn't making much power at all, and I get noticeable roughness. At low power settings or high altitudes, I just lean to rough and then enrich to smooth, at which setting #2 is about 50 ROP and #3 is about 25 LOP. In spite of what some folks have tried to tell me, I'd be afraid to do that at higher power settings since I'm not convinced that my 200 hp IO360 doesn't have a "red box" danger zone, and at that setting, if it does my #2 is right smack dab in the middle of it. (And if it is, I normally won't learn that by watching CHTs, since I almost never see CHTs above 350F no matter what I do.)Use the last cylinder to peak as you are leaning as the one you set up with because it will be the one that gets hurt if you have it to close to peak or slightly rich with higher power settings as the cylinders that peaked first are on the LOP side.
Herein lies the problem if your FF's for each cylinder aren't really close. You set the last to peak for 25 degrees or so LOP and the first to peak are now so lean that the cylinders are starving. They will not be damaged, but the engine may be rough running.
This is exactly why I can't run LOP at higher power settings -- to get my richest cylinder (#2) safely LOP, I've got to lean so far that my leanest (#3) isn't making much power at all, and I get noticeable roughness. At low power settings or high altitudes, I just lean to rough and then enrich to smooth, at which setting #2 is about 50 ROP and #3 is about 25 LOP. In spite of what some folks have tried to tell me, I'd be afraid to do that at higher power settings since I'm not convinced that my 200 hp IO360 doesn't have a "red box" danger zone, and at that setting, if it does my #2 is right smack dab in the middle of it. (And if it is, I normally won't learn that by watching CHTs, since I almost never see CHTs above 350F no matter what I do.)
I'm a little confused by this statement. I thought that the whole context of the Red Box was that was the zone with potentially damaging temperatures and pressures.I'd be afraid to do that at higher power settings since I'm not convinced that my 200 hp IO360 doesn't have a "red box" danger zone, and at that setting, if it does my #2 is right smack dab in the middle of it. (And if it is, I normally won't learn that by watching CHTs, since I almost never see CHTs above 350F no matter what I do.)
I'm a little confused by this statement. I thought that the whole context of the Red Box was that was the zone with potentially damaging temperatures and pressures.
How can an engine be in the Red Box with CHTs at 350F?
CHTs are only part of it. It is possible for an engine with good cooling to be operating with high internal cylinder pressures which are causing extra wear while having low CHTs observed. This isn't saying that the engine is experiencing detonation, but that is possible also.
I've had engines detonate with CHTs of 350 or less. But those were detonation prone engines and I was doing other things to poke them.
What don't I believe? I don't remember you saying anything specifically about my engine. You did offer to teach me how to operate it safely. But that was before you moved.Seeing as I've done fully instrumented detonation tests on your motor and you don't believe me...
CHTs are only part of it. It is possible for an engine with good cooling to be operating with high internal cylinder pressures which are causing extra wear while having low CHTs observed. This isn't saying that the engine is experiencing detonation, but that is possible also.
I've had engines detonate with CHTs of 350 or less. But those were detonation prone engines and I was doing other things to poke them.
While I have complete faith in your knowledge that an IO-360 won't suffer from detonation or more importantly pre-ignition in cruise with any mixture, that might not account for glowing deposits, hanging helicoil tangs, or overheated spark plug electrodes which can and do occur in the "real world" with no outward indications outside the "red box".Seeing as I've done fully instrumented detonation tests on your motor and you don't believe me...
Lance,While I have complete faith in your knowledge that an IO-360 won't suffer from detonation or more importantly pre-ignition in cruise with any mixture, that might not account for glowing deposits, hanging helicoil tangs, or overheated spark plug electrodes which can and do occur in the "real world" with no outward indications outside the "red box".
I believe that is a bit overconservative, at least for a NA engine. For instance I think the APS recommendation these days calls for staying out of the 25-50 ROP range at 65% as long as CHTs are under control.I use this as my reference for LOP ops (Hopefully no issues with posting this):
They are Gamis. My A&P IA who did the prebuy asked me if I wanted to have the injectors cleaned, although when he said that while some folks swear by it, others say there is no need to clean them I opted to save the money for some other items I wanted to get ahead on. Sounds like I may want to try having them cleaned now.
Does anyone know if cylinder 6 is where the factory CHT probe was originally installed?
Read the JPI manual. The read it again. And again. Then let's discuss.
Okay, so the Red Box is more of a detonation prone zone than straight temp or pressure?
What don't I believe? I don't remember you saying anything specifically about my engine. You did offer to teach me how to operate it safely. But that was before you moved.
Lots of people have said lots of things about my engine. Lots of things, both ways. You're about the only person whose opinion I would trust, if I heard it first hand from you.
So are you saying that it can't be made to detonate during normal operation? What about accelerated wear due to high ICPs? Or am I misunderstanding you (again?) ?
Question: Given an engine with 7.5:1 compression ratio and 100LL operating at 30 inches or less manifold pressure, what are the chances of detonation at any mixture setting?
Where I'm going with this is that I have seen high CHTs when running the TSIO-360 above 30 inches with various mixture settings but I have not seen high CHTs when running at any speed in the range of 2,300 to 2,500 and any mixture when 30 or below.
Basically, I'm curious about what you've seen in terms of detonation with low compression engines at various manifold pressures.
While I have complete faith in your knowledge that an IO-360 won't suffer from detonation or more importantly pre-ignition in cruise with any mixture, that might not account for glowing deposits, hanging helicoil tangs, or overheated spark plug electrodes which can and do occur in the "real world" with no outward indications outside the "red box".
Explain this if ya don't mind...
Keep in mind that your engine is a TSIO-360, which I have never run a detonation test on. I have no idea as to its specific characteristics and how it behaves compared to others. Now with that said, I would think at under 30" with 7.5:1 compression on 100LL you would be pretty unlikely to have any detonation occur.
A casual observation WRT CHTs on turbocharged engines is that I've seen them rise noticeably at power settings above 30". I'm not entirely what sure what makes that the magic number for most engines, but I suspect it probably just has to do with the pressure ratio increasing by that extra few percent once you get above 30" resulting in the turbocharger having more exhaust (heat) going through it, heating the intake air charge more (both from a hotter turbo and higher pressure ratio), and the engine working a bit harder.
Ted, thanks for saying it clearly. If you said it before, I must have missed it. I do recall you saying that below 75@ (damm iPad doesn't sem to have a percent symbol), the risk drops off rapidly, or something to that effect, but it sounded fuzzy enough that I didn't feel safe at much above 65. Even so, since the optimum LOP setting puts one of my cylinders right at peak power/ICP, I'm not too comfortable about running it that way. My A&P is still not completely sure that there isn't something screwy with my induction system and wants to try checking for leaks with a shop vac before telling me to go for GAMIs.
Yes you should!Maybe I should write a thread that goes into the anatomy of what exactly a detonation test entails.
Adiabatic and frictional heating of the intake air, higher ICP, higher exhaust back pressure, and more power. Sounds like worse than a triple whammy.A casual observation WRT CHTs on turbocharged engines is that I've seen them rise noticeably at power settings above 30". I'm not entirely what sure what makes that the magic number for most engines, but I suspect it probably just has to do with the pressure ratio increasing by that extra few percent once you get above 30" resulting in the turbocharger having more exhaust (heat) going through it, heating the intake air charge more (both from a hotter turbo and higher pressure ratio), and the engine working a bit harder.
The reason he is suspicious is that I have (twice now) seen the #3 EGT (not CHT) shoot up >25F for a half minute or so. The first time it was close to 100 degrees higher, the second time (today) it was about 40 degrees.Well, if there is something funny going on with your induction system, then that needs to be checked out and see what's going on. Either way, at 75% power on your engine with the low CHTs that you've reported, detonation just isn't something that will happen on your engine unless you've got something really weird going on (like being in 120F ambient temps). And if there is, you'll notice abnormal temperatures (CHTs will go up up up on that cylinder).
I wasn't planning on it because of my annual. The annual is done, but there are some issues to iron out, the most pressing being that my fuel selector valve failed to turn off my fuel flow today when turned to the "off" position. It only happened once, and wiggling it fixed it, but if it gets stuck in one position I wouldn't trust it not to get stuck in a different one...I don't think you're planning on making it to Wings, but if you do make it that way, we can go up for a quick demo flight.
Thanks Lance!I'm pretty sure the OEM CHT was on #3 but it might be #4. In any case it's easy to spot a spark plug gasket probe, just look for a metal shielded wire about 1/8" diameter coming from the base of one of the plugs. I had one on my Bonanza and never liked it much. JPI offers a much better solution that goes in between the OEM probe and the cylinder with both in the same boss under the cylinders as the rest of the JPI probes. I strongly recommend getting one of those so you don't have ambiguous CHT readings. It is true that the plug gasket probe will read higher but the amount higher varies significantly with airspeed and power along with which plug location (top or bottom) is used.
As to LOP ops, the first thing to do is get a handle on your mixture distribution. IO470s are notoriously difficult to balance well but with some effort it can be done. If your JPI has FF taking a measure of the "GAMI spread" is easy but without that it can require an hour in the air and is best accomplished with an assistant.
I recommend doing the check at 7000 MSL with full throttle and 2300 RPM first. If the engine is set up properly (good ignition system and well balanced mixtures) you should be able to get the richest cylinder at least 30-40 LOP while running smoothly and this should result in a fuel flow between 11 and 11.5 GPH per engine. You might improve things by closing the throttles just enough to drop the MP by a few tenths of an inch of Hg.
CHTs should be in the low to mid 300s with ISA standard OAT. Anything above 350 suggests that you're either running ROP or need to attend to baffling or ignition timing.
If the engine runs OK LOP there try 10,000 MSL (DA actually). At that density they probably won't run smoothly more than 5-10° LOP and even peak EGT is close enough for efficient and cool operation. CHTs here should be in the 300-325 range.
Another good check involves comparing the relative order of the EGT peaks at or above 8000 MSL with what you get at least 4000 ft lower using the same MP and RPM (obviously the throttle must be partially closed then). If the order changes AND there's at least a .1gph Peak EGT FF difference between cylinders the change order you probably have an induction leak.
11.5 GPH is 65% max rated power and you really can't hurt the engine with the red knob at that FF, especially if you keep the CHTs at 380°F or less. When I had IO470s I'd almost always run that power (11.5 Gph) at or below 11,000 MSL (that's about peak EGT at 11) and would see around 175 KTAS at 7 and 180 at 11 with CHTs around 300°F.
I don't generally check how far from peak EGT I'm running unless I'm down low and running hard (rare for me). But at first it's a good idea to check this on almost every flight until you find the "sweet spot" for your engines. I prefer to check by leaning until the engine is either noticeably rough or the power drops enough to feel the plane decelerate (the "Big Pull") then slowly enrichening the mixture looking for the first cylinder to peak. The EDM 760 usually does a decent job of identifying the first cylinder to peak but is pretty lousy at capturing the exact temp at which that peak occurred so you'll want to tweak the FF slowly (.1 gph between EGT checks) while monitoring the first to peak (richest) cylinder.
I especially don't like JPI's "LOP Lean Find mode" as it requires you to start on the ROP side and move the mixtures smoothly but more slowly than I found practical with the levers in a Baron. The results from that for me were inconsistent in terms of the displayed peak and LOP values by 25-30°F and it often identified the wrong cylinder as the richest. I recommend either just using the Normalize mode and watching the bars (10°F resolution) to find the richest cylinder and then selecting that cylinder to show the digital EGT for it but the original "Lean Find" mode does pretty well at finding the richest cylinder if you approach from the LOP side.
One caution when searching for the richest cylinder from the LOP side is that there are often two peaks and you want to use the one with the highest FF so after you think you have the first to peak from the lean side you should continue going richer until that EGT gets at least 25° cooler. If you find a second peak at a higher FF make sure you're working with the richest cylinder as you might have gone past peak EGT on another cylinder on your way to the second peak on the first cylinder to peak (falsely).
If you can't get the engine to run smoothly up high but LOP seems to work OK down low you probably have some ignition system issues. A WOT LOP mag check at or above 8000 MSL might identify a specific cylinder and that could be a spark plug or wire issue. If all are misfiring or (more likely) the leanest 2-4 cylinders are misfiring (EGTs become erratic) it's probably a magneto problem. I use fine wire plugs (Tempest) and I think they help, especially up high but I also have the more powerful and arc-over resistant Bendix 1200 series magnetos.
BTW, Champion has been having issues with their internal resistors breaking down and if your plugs are affected by that this could make it difficult to run LOP especially above 5000 MSL.
One last tidbit: Cylinder 5 is almost always the hottest if the mixtures are well balanced and a 20-30°F cylinder to cylinder CHT difference isn't unusual. Just make sure they are all at or below 380 and they should be less than that in LOP cruise.
Yes you should!
Adiabatic and frictional heating of the intake air, higher ICP, higher exhaust back pressure, and more power. Sounds like worse than a triple whammy.
The reason he is suspicious is that I have (twice now) seen the #3 EGT (not CHT) shoot up >25F for a half minute or so. The first time it was close to 100 degrees higher, the second time (today) it was about 40 degrees.
I wasn't planning on it because of my annual. The annual is done, but there are some issues to iron out, the most pressing being that my fuel selector valve failed to turn off my fuel flow today when turned to the "off" position. It only happened once, and wiggling it fixed it, but if it gets stuck in one position I wouldn't trust it not to get stuck in a different one...
If by some miracle my A&P solves this by late in the week, I might make a surprise trip over on Saturday and take you up on that demo flight. I have a hike to lead in the morning, though, and an AME appointment on Monday, so my schedule is a little tight this weekend.