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Lycoming EGT, IO 540

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jrccea(at)bellsouth.net
Guest

Posted: Fri Nov 09, 2007 6:39 pm Post subject: Lycoming EGT, IO 540

Have you moved the thermocouples around too, to  assure that your 100 degree difference isn't due to a thermocouple  difference?

 JimC

 [quote]   ---

mlas(at)cox.net
Guest

Posted: Sat Nov 10, 2007 10:04 pm Post subject: Lycoming EGT, IO 540

Bob,  

   

100 deg?  EGT or CHT?  What you are trying to do is to get each cylinder to peak at the same time.  What you’re looking for is the delta between when each cylinder peaks.  In a perfect world all the cylinders should peak at the same time at the same temperature.  That never happens because of many factors; cooling effect, induction difference, valve opening, ect.  It is very common to see on a well setup engine peak deltas around 30~60 deg. between each other.  The CHT by itself is for limit purposes and the EGT is to help find when each cylinder peaks.  I hope this helps.  

   

Mike Larkin  

   

--

glcasey

Joined: 01 Jul 2007
Posts: 23

Posted: Sat Nov 10, 2007 10:07 pm Post subject: Lycoming EGT, IO 540

Bob,

First, it would be good to know which version of the IO-540 you have  

since the angle-valve and parallel-valve engines have quite different  

intake systems.  The angle-valve engines have an intake system that  

is quite good in that the tubes are well matched, have a reasonable  

tuning benefit and don't absorb too much heat from the oil.  The  

parallel-valve engine, on the other hand, were designed for  

carburetion and have much of the intake system buried in the oil  

sump, transferring more heat and limiting the freedom of design.   

Generally, though, the air distribution of these engines is pretty  

good.  The first thing to do when sorting out air/fuel distribution  

questions is to measure it using the "lean sweep" method.  Starting  

well rich, record all exhaust temperatures and fuel flow (it's handy  

to record CHT's and flight data as well, but it is not necessary for  

good results).  Lean the engine a step at a time - the finer the  

steps the better, although it will start to take too long if done to  

the extreme.  After all cylinders have peaked continue to go lean  

until you get at least 2 or 3 data points on the lean side of the  

leanest cylinder.  The biggest problem I've had is not waiting long  

enough for all the variables to stabilize before recording the data.   

It is good to do the exercise a few times to make detection of bogus  

data points easier.  Plot the temperature of each cylinder against  

fuel flow all on the same chart.  Pick what appears to be the "best  

fit" straight line on the rich side and another on the lean side,  

extending them until they cross.  That is the fuel flow at which that  

cylinder peaks. Do not just pick the highest temperature and call  

that the peak as the temperatures have a tendency to round off near  

the peak, making the true peak hard to find.  Do that for all  

cylinders and measure the spread of fuel flow between the leanest and  

richest cylinders.  Ideally, it should be less than 2%, but 3 or 4%  

is probably okay.  If the spread is more you should do something  

about it.  An easier way is to ship all the data off to GAMI and they  

will give you an expert opinion.



Back to your questions:

1 - 100 degrees is significant, but there may not be much you can do  

about it.  The thermocouple readings can be affected by cooling air  

flow on the outside of the pipe as well as orientation of the probe  

itself.  Exhaust flow inside the tube is not uniform around the  

diameter - all probes should be the same distance down from the  

cylinder and inserted from the same angle.  The temperature of the  

cylinder itself will affect the measurement.  My hottest cylinder  

also has the highest EGT reading - does one cause the other, or is it  

coincidence?  Hard to say.  Why, then would one be different that the  

other?  There are three fundamental factors on EGT - mixture (you're  

going to take that out of the equation), Compression ratio (all  

cylinders are the same, right?), and spark timing (hard to imagine  

the timing for one cylinder being different than the others).  That  

pretty much brings it back to measurement errors unless the exhaust  

valve is leaking a lot.

2 - The temperature of the inlet air won't have much effect on air/ 

fuel distribution.  It's possible that ram air will have a  

deleterious effect on smoothness, however.  If the manifold pressure  

at the intake port becomes higher than the upper plenum pressure it's  

possible that some fuel could come out the air bleed vents, although  

this usually leaves a tell-tale stain around the injector.  I could  

also make the atomization of the injector suffer and that in turn  

could create a cycle-to-cycle variation in fuel flow, making the  

engine feel rough.  A good injected engine should be able to be  

leaned so much that the power is way down and still be running  

smoothly.  Not all are that way.

3. - Intake turbulence itself is probably beneficial to mixing the  

air and fuel unless one intake runner is different than another.   

Lycoming engines are typically pretty good in this regard, but again,  

I have no idea which type you have.



Just as an aside, I've messed around trying to figure out the best  

air/fuel ratio to run.  It all depends on the ratio of your desire  

for speed to the size of your wallet.  Speed is good, but fuel flow  

is bad.  As a first shot I used the same equation some people (CAFE,  

I think) use - multiply mph by mpg.  The peak is the optimum place to  

run if speed is just as important as fuel economy (how do you  

decide?  It's your own choice).  This turns out to be TAS^2/GPH.  I  

found the optimum was just lean of peak.  Going as far lean as  

possible didn't help, although usually it didn't make it much worse  

either.  Going rich was like falling off a cliff.  Fuel flow goes way  

up, but air speed doesn't.  What you really want to put into the  

equation is ground speed, so that will change the shape of the curve  

for every flight.  The optimum with a headwind is on the rich side  

and with a tailwind it is more on the lean side.



FWIW,

Gary Casey

 	  Quote: 	
		  

 Time: 03:20:57 PM PST US

 From: "Bob & Toodie Marshall" <rtmarshall(at)osbtown.com>

 Subject: Lycoming EGT, IO 540



 Hi all, At overhaul I had the cylinders flow balanced, the engine runs

 very well, very smooth. Considering the rising fuel costs, I have been

 considering attempting to run the engine LOP, I have been unsuccessful

 as the richest cylinder peaks last and by then the other cylinders are

 running rough. I use the AFP fuel injection system which performs

 flawlessly and have moved nozzles around to effect egt changes which

 have been effective to a point, where cyl #6 runs 100 degrees cooler

 than the others. My question? Is 100 degrees a significant number when

 compared to the other five cylinders?The engine builders out there who

 are making real HP see the different relationships on cooling effects

 and cylinder balancing and the induction system.   Question #2 does  

 cold

 air induction help to make the lycoming run more evenly balanced in

 respect to temps. #3 Is it possible that the stock lycoming intake

 system generates to much internal  turbulence which effects the

 individual cylinder performance? Thanks for any info and taking the  

 time

 to answer.  Bob

_________________
Gary Casey

Bob Buckthal

Joined: 10 Jan 2006
Posts: 2

Posted: Sat Nov 10, 2007 10:47 pm Post subject: Lycoming EGT, IO 540

First read John Deakins series of articles on  engine operation on the Avweb.com site.  Differences in EGT are likely more  to do with temp probe instalation.  Your goal is to get all the EGT's to  peak(regardless of the temp) at the same throttle position.  It one cyl has  not peaked and the others are in lean missfire, Your FI may not be  flawless.  The induction system is well designed.  Unless your engine  builder left a tool or a rag in there, that is not your problem.  Go back  and redo the nozzles.  DO NOT try to achieve an even temp.  Once they  all achieve their peak temp at the same throttle position you should be able to  get as much as 150 degrees lean of peak before missfire.  

  

 Bob

 [quote]   ---

w_sweet(at)comcast.net
Guest

Posted: Sun Nov 11, 2007 5:59 am Post subject: Lycoming EGT, IO 540

---

glcasey

Joined: 01 Jul 2007
Posts: 23

Posted: Sun Nov 11, 2007 6:03 am Post subject: Lycoming EGT, IO 540

Bob's comment brings up a question I have.  I've got a parallel-valve  

IO-540 with 10:1 compression and electronic ignition on the top  

plugs, mag on the bottom, timing set at 22.  The cylinders are very  

closely matched for air/fuel, within about 1.5%.  When I lean the  

engine LOP the temperatures drop just a little before it goes rough  

and sometimes go flat or back up, so I typically operate just barely  

LOP.   I don't have a good explanation for this behavior unless my  

ram air induction is working so well that the injectors have no air  

flow in them to atomize the fuel.  However, I don't see any fuel  

stains around the injectors, so there apparently isn't any fuel  

coming out the vents.  There is no way the engine would run 150 LOP  

as Bob suggests below.  Any ideas on why this engine seems to operate  

different than the norm?



Gary Casey



 	  Quote: 	
		     ....Once they all achieve

 their peak temp at the same throttle position you should be able to  

 get

 as much as 150 degrees lean of peak before missfire.



 Bob

_________________
Gary Casey

apilot2(at)gmail.com
Guest

Posted: Sun Nov 11, 2007 6:44 am Post subject: Lycoming EGT, IO 540

I run an IO-360 angle valve engine. It will run nicely lean of peak to about 60-70 lean of peak. At that point EGT can start back up or the engine start to quit. You are right...you only need 10-20 LOP if you are running 70% or less power. As your power goes up, you need to be leaner, maybe 30-40 LOP at 75% or higher. Unless you have a turbo, you are unlikely to run much over 85% LOP, so forget about much leaner. The turbo guys will cruise up to 90 LOP on a big Continental. The Lyc turbo 540, at least as used in the Mooney TLS Bravo generally won't run LOP without turbine inlet temps going above redline. It is one of the few engines that simply doesn't like LOP. 



On Nov 11, 2007 7:02 AM, Gary Casey <glcasey(at)adelphia.net (glcasey(at)adelphia.net)> wrote:

[quote] --> Engines-List message posted by: Gary Casey <glcasey(at)adelphia.net (glcasey(at)adelphia.net)>



Bob's comment brings up a question I have.  I've got a parallel-valve

IO-540 with 10:1 compression and electronic ignition on the top 

plugs, mag on the bottom, timing set at 22.  The cylinders are very

closely matched for air/fuel, within about 1.5%.  When I lean the

engine LOP the temperatures drop just a little before it goes rough

and sometimes go flat or back up, so I typically operate just barely 

LOP.   I don't have a good explanation for this behavior unless my

ram air induction is working so well that the injectors have no air

flow in them to atomize the fuel.  However, I don't see any fuel

 stains around the injectors, so there apparently isn't any fuel

coming out the vents.  There is no way the engine would run 150 LOP

as Bob suggests below.  Any ideas on why this engine seems to operate

different than the norm? 



Gary Casey



 	  Quote: 	
		     ....Once they all achieve

 their peak temp at the same throttle position you should be able to

 get

 as much as 150 degrees lean of peak before missfire.



 Bob 


	


[b]

mlas(at)cox.net
Guest

Posted: Sun Nov 11, 2007 8:41 am Post subject: Lycoming EGT, IO 540

Gary,



One problem I see with your setup is the electronic ignition with a

fixed timing mag.  I see why you went this way but you should be aware

that when both systems fire, the first one is more or less the only one

that counts.  So in order to get optimum performance you must know

exactly when you electronic ignition fires and it must be the same as

the mag at cruse and higher power or your working against yourself.  In

other words for performance a single ignition system.



Just a thought,



Mike Larkin 



--

s_korney(at)hotmail.com
Guest

Posted: Sun Nov 11, 2007 3:49 pm Post subject: Lycoming EGT, IO 540

Gary...



What brand of electronic ignition do you have....?  I would think the EI would have a lot more advance then the mag at almost any manifold pressure other then maybe sea level...



Best... Steve



 	  Quote: 	
		   From: glcasey(at)adelphia.net

 Subject: Re: Lycoming EGT, IO 540

 Date: Sun, 11 Nov 2007 06:02:45 -0800

 To: engines-list(at)matronics.com

 

 --> Engines-List message posted by: Gary Casey <glcasey(at)adelphia.net>

 

 Bob's comment brings up a question I have.  I've got a parallel-valve  

 IO-540 with 10:1 compression and electronic ignition on the top  

 plugs, mag on the bottom, timing set at 22.  The cylinders are very  

 closely matched for air/fuel, within about 1.5%.  When I lean the  

 engine LOP the temperatures drop just a little before it goes rough  

 and sometimes go flat or back up, so I typically operate just barely  

 LOP.   I don't have a good explanation for this behavior unless my  

 ram air induction is working so well that the injectors have no air  

 flow in them to atomize the fuel.  However, I don't see any fuel  

 stains around the injectors, so there apparently isn't any fuel  

 coming out the vents.  There is no way the engine would run 150 LOP  

 as Bob suggests below.  Any ideas on why this engine seems to operate  

 different than the norm?

 

 Gary Casey

 

 >   ....Once they all achieve

 > their peak temp at the same throttle position you should be able to  

 > get

 > as much as 150 degrees lean of peak before missfire.

 >

&========================Climb to the top of the charts!  Play Star Shuffle:  the word scramble challenge with star power. Play Now!

frank.hinde(at)hp.com
Guest

Posted: Mon Nov 12, 2007 7:44 am Post subject: Lycoming EGT, IO 540

Not at all, The EI's will have both less and more advance  depending on manifold pressure. Mags are set at 25deg which is a compromise  between poor starting, high power operation and economy  cruise.

  

 Pretty much all EI's run at about 25 DEG at full power but can  advance to 40deg plus at low manifold pressure.

  

 I wonder if this engine is truly running balanced...what does  "withing 1.5%" mean?....If it means the cylinders flow the same amount of air on  the bench then this is meaningless as far as blancing the injectors.  

  

 Each cylinder needs to get to peak EGT at the same fuel flow (mine  is about 0.5GPH between richest and leanest)....Nothing else matters...If the  cylinder don't all peak at the same fuel flow (or close to it) the engine will  not run LOP very well.

  

 I think what we have here is some cylinders running ROP while the  others are runnin so LOP that the flame is going out...I.e well  LOP.

  

  

 Frank RV7a IO360



   From: owner-engines-list-server(at)matronics.com  [mailto:owner-engines-list-server(at)matronics.com] On Behalf Of steve  korney

Sent: Sunday, November 11, 2007 3:49 PM

To:  engines-list(at)matronics.com

Subject: RE: Re: Lycoming  EGT, IO 540

 

Gary...



What brand of electronic ignition do you  have....?  I would think the EI would have a lot more advance then the mag  at almost any manifold pressure other then maybe sea level...



Best...  Steve



 	  Quote: 	
		   From: glcasey(at)adelphia.net

 Subject: Re:  Lycoming EGT, IO 540

 Date: Sun, 11 Nov 2007 06:02:45 -0800

 To:  engines-list(at)matronics.com

 

 --> Engines-List message posted  by: Gary Casey <glcasey(at)adelphia.net>

 

 Bob's comment  brings up a question I have. I've got a parallel-valve 

 IO-540 with 10:1  compression and electronic ignition on the top 

 plugs, mag on the  bottom, timing set at 22. The cylinders are very 

 closely matched for  air/fuel, within about 1.5%. When I lean the 

 engine LOP the  temperatures drop just a little before it goes rough 

 and sometimes go  flat or back up, so I typically operate just barely 

 LOP. I don't have a  good explanation for this behavior unless my 

 ram air induction is  working so well that the injectors have no air 

 flow in them to atomize  the fuel. However, I don't see any fuel 

 stains around the injectors, so  there apparently isn't any fuel 

 coming out the vents. There is no way  the engine would run 150 LOP 

 as Bob suggests below. Any ideas on why  this engine seems to operate 

 different than the norm?

 

  Gary Casey

 

 > ....Once they all achieve

 > their  peak temp at the same throttle position you should be able to 

 >  get

 > as much as 150 degrees lean of peak before missfire.

  >

&========================> 
	


 	  Quote: 	
		   

  


	


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[b]

glcasey

Joined: 01 Jul 2007
Posts: 23

Posted: Tue Nov 13, 2007 6:42 am Post subject: Lycoming EGT, IO 540

Thanks for the replies.  The ignition is the Lightspeed Plasma III,  

which I'm sure you all know is a capacitive discharge wasted-spark  

system.  The "III" as far as I know is sort of a double polarity  

system that presumably strikes the arc twice, once in each  

direction.  I'm not a fan of CD systems, but I think they work ok -  

they're just much more electrically complex than an inductive  

system.  I haven't had any luck extracting the advance curve from  

Claus and I'm not sure why it seems to be a secret.  He sells a  

monitor system that provides a panel readout of advance, but I don't  

have that.



My timing settings were static.  I set the mag (no impulse coupling)  

at 22 degrees and attempted to set the Lightspeed at about the same  

value.  During runup the rpm drops are about equal, confirming that  

the Lightspeed timing is about the same as the mag.  I had no luck  

trying to rig a timing light to check the advance.  I understand that  

at rpms below something like 2000 there is no "vacuum" advance in the  

Lightspeed, so it should be producing a spark at the base timing.  I  

should have done mag checks at altitude, but I haven't.  My  

assumption is that at higher rpm and the low manifold pressures at  

altitude the Lightspeed provides a more advanced timing.  Does anyone  

have information about the advance characteristics of the Lightspeed  

unit?



The "1.5%" I was talking about is the difference in fuel flow between  

when the leanest and richest cylinders peak.  Frank says that his  is  

within 0.5GPH - assuming the fuel flow of the IO360 is about 10GPH  

that works out to 5% difference, significantly worse that what my  

engine data indicates.  The 1.5% number I stated actually ranged from  

0.8% to 3% depending on which of the 10 or so tests I look at.  The  

standard deviation hangs around 0.7% indicating the data is  

reasonably well behaved.  And, while the cylinders were presumably  

"ported and flow balanced" I have no idea as to whether the air  

distribution is precise.  However, it is unlikely that the air  

distribution would be poor AND the injectors mismatched to exactly  

compensate.  Therefore, I am reasonably confident that both air and  

fuel distribution are very close.



My next test will  be one to determine if the injector atomization  

plays a part.  I plan to do a lean sweep at full throttle followed by  

another with the throttle closed enough to reduce the manifold  

pressure by 1 inch.  That should be enough to induce at least some  

air flow through the injectors.

Gary



On Nov 12, 2007, at 11:56 PM, Engines-List Digest Server wrote:



 	  Quote: 	
		  

 Time: 07:44:22 AM PST US

 Subject: RE: Re: Lycoming EGT, IO 540

 From: "Hinde, Frank George (Corvallis)" <frank.hinde(at)hp.com>



 Not at all, The EI's will have both less and more advance depending on

 manifold pressure. Mags are set at 25deg which is a compromise between

 poor starting, high power operation and economy cruise.



 Pretty much all EI's run at about 25 DEG at full power but can advance

 to 40deg plus at low manifold pressure.



 I wonder if this engine is truly running balanced...what does "withing

 1.5%" mean?....If it means the cylinders flow the same amount of  

 air on

 the bench then this is meaningless as far as blancing the injectors.



 Each cylinder needs to get to peak EGT at the same fuel flow (mine is

 about 0.5GPH between richest and leanest)....Nothing else matters...If

 the cylinder don't all peak at the same fuel flow (or close to it) the

 engine will not run LOP very well.



 I think what we have here is some cylinders running ROP while the  

 others

 are runnin so LOP that the flame is going out...I.e well LOP.

 Frank RV7a IO360

_________________
Gary Casey

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