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Delta Charlie
04-13-2010, 09:30 AM
The #3 runs about 100 deg. hotter than the next hottesest cylinder(#4) at cruze settings. I have a pa-18, narrow deck(o-320)with lycon cylinders, sutton exhaust and about 125 TSMO (Buldock). The engine runs good,cht's are below 360 deg. at cruze. I have a JPI 700 with the probes mounted aprox. 2.25"-2.75" from the exhaust flanges. Number 3 peaks out aprox. at 1625 deg. and in cruze I run at 1525 deg. Just seams high, anythoughts? Thanks again

DW
04-13-2010, 12:49 PM
Try swaping the prob to another cylinder to make sure its not a bad one.

FdxLou
04-13-2010, 01:24 PM
EGT #'s are way too high for a 4 cyl Lyc. High 1300's to mid 1400's are normal for lean operations. My hottest cyl peaks at around 1405F under most conditions.

Sounds like you may have a bad thermocouple. I can't even get to 1500F without running rough due to fuel starvation. My probes are all placed at 2 1/2" from the exhaust flange.

Anxious to hear what you find.

Lou

Darrel Starr
04-13-2010, 02:13 PM
I agree, your temps are too high -- 1300 to 1350F is where my #3 cylinder runs. Here is a typical reading @ 2350 to 2400 rpm, leaned to sputter minus 1/4 inch. This is an EI gauge and probes in a stock narrow deck 160 hp Lyc. The probes are 1.5 inches from the flange as recommended by EI.
Darrel
#1: 1211 #2: 1277 #3: 1296 #4: 1272

Delta Charlie
04-13-2010, 03:08 PM
my spred from hot to cold is 220 deg. at 2400 rpm? At full throtle they are all even however as soon as I reduce power the temps go iritic? I will try swaping #1 with #3. Number 4 typically peaks first around 1525 deg followed by #3. Thanks again

mvivion
04-13-2010, 03:13 PM
Exhaust gas temperatures are relative numbers. It really doesn't matter what temperature they read, what you're concerned about is where they peak, and what the relationship between cylinders is.

Some EGT's in Cessna airplanes didn't even offer a number, since the numbers are essentially irrelevant. See Lycoming's web site for more information on this topic.

Delta Charlie: Where is your oil cooler located? Do you have any big gaps or holes in your baffles or baffle seals?

Frankly, every small Lycoming I've ever met has AT LEAST a 100 degree difference between the hottest cylinder and the next hottest. If your EGT's are much closer, that engine may be fuel injected.

In other words, what you describe is perfectly normal in my experience.

MTV

Darrel Starr
04-13-2010, 03:40 PM
Is compression OK? Check for an intake air leak on #3, possibly around the short hose sections.
Darrel

Delta Charlie
04-13-2010, 05:27 PM
New baffels and seals,starter hole blocked off,oil cooler rear mounted,new intake hoses,good compresions,rebuilt mags,rebuilt carb. Does the jpi have to be calabateded or can it be? Should I see were each cycl peaks then record the difference? If the etg's on #3 were really as hot as the jpi says would'nt the cht's on #3 be hi? Thanks again

brown bear
04-13-2010, 06:48 PM
This is not a answer , but a little info. I just changed from 150 hp cylinders to 160 hp cylinders and my EGTs droped , same senders, same every thing ?
Before ,just befor the engine got ruff when leaning, I would see EGTs above 1500, now 1450 ? Anyone else seen this?
Doug

WSH
04-13-2010, 06:55 PM
Not sure where you located, at Sea level or out west at HIGH altitude?

Swapping probes is not a bad idea, simple and quick but, usually the probes seem to fail extremely one way or the other, usually high off the chart, and not marginally. Usually!

1625 sounds a little high, again depends somewhat on your altitude. I normally see 1550-1575 peaks routinely at high power and low level, below 3K MSL, depending on OAT.

Check your timing, slightly retarded timing will give you higher EGT's and lower CHT's. And 360 degrees CHT sounds "kinda" low for my 0320, especially for # 3 which tend to run hottest, for 2400 rpms and 100 ROP. Again, knowing where you are operating, at what altitude and OAT would influence the numbers.

Also try a high cruise power, VERY LEAN, in flight mag check, leave it on one mag for a at least one minute. Being very lean put's the most stress on the ignition and will reveal any weaknesses quicker than a low power and/or very rich mag check. A weak or intermittent spark plug will cause higher EGT's and lower CHT's .

While your swapping probes, swap the plugs too and eliminate them as the problem as well!

Report back what you find.

One other thing, try checking it at different power settings, say 2300 and then 2500 or so and see if the differential increases, decreases or stays about the same.

And, maybe post a data trace from the JPI ?


Almost forgot the obvious, an induction leak on # 3 would cause a higher EGT, although your normal to cool CHT would make it doubtful but, worth a check anyway. Look for a loose/torn induction hose and loose primer/injector plug.

WSH
04-13-2010, 07:13 PM
Lou,


EGT #'s are way too high for a 4 cyl Lyc. High 1300's to mid 1400's are normal for lean operations. My hottest cyl peaks at around 1405F under most conditions.

Sounds like you may have a bad thermocouple. I can't even get to 1500F without running rough due to fuel starvation. My probes are all placed at 2 1/2" from the exhaust flange.

Anxious to hear what you find.

Lou

Hey, where are you running your timing?

Light Speed ignition?

mvivion
04-13-2010, 07:33 PM
Here's a link to Lycoming's recommendations on leaning their engines:

http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key%20Operations.pdf

MTV

garyh
04-13-2010, 07:51 PM
My E.I. book says keep your cht+egt between 1750 and 1825 f. your engine will probably make 2000 TBO if kept at 1750 and 1250-1500 TBO if 1825 or more, above 1850 lucky to get 1000 TBO.
gary

Bugs66
04-13-2010, 08:01 PM
My E.I. book says keep your cht+egt between 1750 and 1825 f. your engine will probably make 2000 TBO if kept at 1750 and 1250-1500 TBO if 1825 or more, above 1850 lucky to get 1000 TBO.
gary

That includes CHT in those numbers, right? I believe I read in EI book that you add EGT+CHT and don't go over 1850 combined.

garyh
04-13-2010, 08:57 PM
you got it bugs66( i like that handle) and keep egt+cht=1750 to get your full TBO.
gary

gdafoe
04-13-2010, 09:03 PM
Interesting Number. What EI book are you all refering to. I don't recall seeing that in any of their stuff I have.

brjanz
04-13-2010, 10:33 PM
Does number three have the spark plug gasket probe? If so it can read higher than the screw in type. I had this happen on an O-360, and read in the user manual that it is common.
Bruce

FdxLou
04-13-2010, 11:12 PM
WSH...

I am not a good comparison for this thread. I run dual P model E-Mag's and have 9.5-1 comp. I also run iridium auto plugs gapped at.035. My timing is set at 35 deg BTDC( Slicks are 25 deg BTDC). All this on a 0-360.

I also have a somewhat "tuned exhaust" ( LEES) with equal length pipes. My intake tubes are also nearly equal length thereby allowing me to have no more than a 15F diff in EGT's. My CHT's are all within 10F at a typical cruise. I can run peak EGT all day long and LOP drops my speed by 3-4 mph. TAS at peak and 2480RPM is 102 MPH. All this on 7.5 to 6.2 GPH depending on GW and altitude. NOT injected! The E-Mags lowered my fuel burn by 1.3 GPH on average. CHT's are 10-15F hotter than with Slick Mags.

I have a Dynon D-10A with TAS( Air Data Computer) and a D-10 EMS with a killer "lean mode" function.

If I go high (9500'-11,500') I have nearly 10 hrs range with VFR reserves! :D

Lou

T.J.
04-14-2010, 01:51 AM
delete

Fortysix12
04-14-2010, 06:34 AM
1650 , I doubt it. Swap probs with anothe cylinder and see if the high temp follows. Sounds like a bad in the system,probe, computor or the already mentioned induction leak. I operate two JPI's on two different aircraft and have never broke 1600 at any altude. One injected , one carbed.

ag-pilot
04-14-2010, 09:09 AM
TJ, I agree, How the heck did several guys around here get over 4000 hrs on a 0320 without all these gadgets.

I think if your gonna run LOP these gadgets might be useful but feeling and hearing what the engine is doing had worked so far for me.

dave

mvivion
04-14-2010, 01:04 PM
TJ, I agree, How the heck did several guys around here get over 4000 hrs on a 0320 without all these gadgets.

I think if your gonna run LOP these gadgets might be useful but feeling and hearing what the engine is doing had worked so far for me.

dave

Times 3.

And, as I noted before, a 100 degree spread on EGT is no big deal on these engines. As to max EGT, that will vary, depending on where in the exhaust pipe the probe is located.

MTV

WSH
04-14-2010, 02:37 PM
Interesting.
I wonder how the old guys got 2000 hrs + before TBO without all the electronic stuff? :D

Probably the same way they all used to navigate before GPS!

I'm sure you don't have one of those either, do you? :lol:

Why is it always the ones who have never used something that are always the "experts" on why you don't need it! :o

mvivion
04-14-2010, 04:04 PM
WSH,

The problem is that pilots get these things, then fail to read the instructions and/or don't understand the normal parameters of the engine.

I have one of these things, but I DON'T use it for leaning this type engine. These devices have other uses, such as diagnosing problems.

But, TJ's point was well taken: If he didn't have a graphic analyzer, he wouldn't "know" he had a problem, because, more than likely he doesn't have a problem.

MTV

WSH
04-14-2010, 05:59 PM
Mike,


WSH,

The problem is that pilots get these things, then fail to read the instructions and/or don't understand the normal parameters of the engine.

I have one of these things, but I DON'T use it for leaning this type engine. These devices have other uses, such as diagnosing problems.

But, TJ's point was well taken: If he didn't have a graphic analyzer, he wouldn't "know" he had a problem, because, more than likely he doesn't have a problem.

MTV

I agree with you that 100 degree EGT differential with these engines is NORMAL. However, with a slightly elevated EGT at 1625 (regardless of what the differential is) could be something as benign as probe placement but, along with that and what I think is a slightly low CHT for 2400 RPMs at 100 ROP ( best power= highest Internal Cylinder Pressures), makes me think it could be more of a timing issue, slightly retarded a couple of degrees. You know, one goes hand in hand with the other.

It's no big deal, one way or the other but, trying to solve the problem, or find out if there even is a problem, over the internet can be useful for those who want to learn.

Again, IMO using an engine monitor to lean an engine, ANY ENGINE, is a third or fourth order reason to have one. Troubleshooting and early diagnoses, i.e. catching little problems before they turn into bigger ones, are the main reasons. And, after 2000+ hours of using them it's clear to me that they save money, actually pay for themselves, and usually all at once and their PROPER use enhances safety.

For those who are not interested in saving money and enhancing your safety, an engine monitor would probably be of little use to you. :lol:

WSH
04-14-2010, 06:37 PM
Stewart,


My -12 remains firmly seated in the Flintstone category of digital sophistication.


What, no GPS in the 12?

StewartB
04-14-2010, 06:49 PM
I do have a 196 in there to validate the panel-mounted whiskey compass that I never expected to work. Surprise. It does. So in all honesty? I don't use the 196.

I will keep an open mind towards the JPI in the Cessna. For a few hours, anyway.

Stewart

garyh
04-14-2010, 08:01 PM
this comes out of my E.I. book "pilots manual for learning and diagnosing engine problems", that "most carb. engines have an egt spread between hottest and coldest cylinders around 150* F except as follows: 0520 and 0470 have egt spreads around 200* F or more" and "most engines have a cht spread between hottest and coldest cylinders around 65* F".
gary

garyh
04-14-2010, 08:04 PM
the word learning in the first sentence should have been "leaning", sorry misspell.
gary