High EGT on one cyl when leaning on ground. OK in the air. Any ideas?

I need some advice from you engine experts out there:

I'm doing breakin on my brand new Lyc IO-360 with dual P-mags (114 series) and the tach is now 8 hrs 20 mins.
The EGT on cyl # 1 has been 100-200*F higher than the other cylinders from day 1, when leaning on the ground, so I'm wondering why?
(I always lean on the ground, to the point where the engine stumbles and then increase mix until smooth.)

At first I though it was due to the injector not set correct, but that isn't the case I think. I've adjusted it a couple times. At 1000 RPM, the RPM now increases about 30 RPM before dropping.
That schould indicate that the injector is set about right.

On the mag check, all temps are equal (mix is full rich ofcourse) and normal RPM drop.
All EGT's increase the same amount when running on each P-mag separately.

Here's a pic taken on ground:



If I enrichen the mix some, the #1 EGT decreases until it's equal to the other three cylinders.
If I don't enrichen the mix, the #1 CHT gradually increases about 20-50*F.
(Engine runs smooth all the time.)
Therefore SOMETHING causing the #1 cylinder to run hotter than the other three when leaning on ground, but WHAT??




What puzzles me, is that when I'm in the air, the #1 EGT is always equal the the other cylinders.

Here's a pic in the air:




During the first 2-3 hours, #1 CHT was 20-30*F hotter than the other three. The airdam in front of #1 was pretty big, so I made two slots in the airdam. Now #1 CHT is at the same value as the other three cylinders.

For now, I'm flying 75-150*F ROP and I've watched #1 EGT closely when I've leaned to peak and then enrichen to 75-150 ROP. The EGT has always peaked at the same time at at the same level as the other three cyl's. Therefore, I assume this is a ground issue only.

So the big question is: what can cause the EGT on #1 to be so much hotter than the other three when leaning on the ground??

My guess is you have an intake leak that you are only seeing in low MP.
On the ground at idle, spray all intake tubes, gaskets and things with any ether based spray fluid and it should expose the culprit.

Please explain further

Kahuna said:

My guess is you have an intake leak that you are only seeing in low MP.
On the ground at idle, spray all intake tubes, gaskets and things with any ether based spray fluid and it should expose the culprit.

Click to expand...

I don't have this issue but would like to file this trouble shooting method for my bag of tricks.

What would I look for as I spray the ether, flames, surge, rpm increase?

Thanks in advance for the online training.

Cheers

In no specific order, give these ideas a try:

1) Grab the intake tube and shake it. If it is loose, re-swedge it.

2) Use tape, modeling clay (or RTV, for that matter) to seal where the tube joins the sump. If that fixes the problem, at least you have found the source of the problem. At that point, you could externally seal it (which is a bandaid fix) or could re-swedge it or replace the intake tube.

3) Check your hose clamps and the connection where the intake joins that cylinder. If you see blue stains at a joint, that's probably the source of your problem.

RVG8tor said:

I don't have this issue but would like to file this trouble shooting method for my bag of tricks.

What would I look for as I spray the ether, flames, surge, rpm increase?

Thanks in advance for the online training.

Cheers

Click to expand...

Any change in the engine. If you have a leak, you'll know it right away.

Might be the flow divider. At idle the flow divider divides the fuel to each nozzle. At fuel flows above 8 GPH the flow divider is wide open and the nozzles divide the flow.

Check for the intake leak first. It would show up in flight too when you throttle back, (15? to 16? MAP).

If you're flying, here is Mike Busch's Induction leak test, copied from my test card.

Induction leak test
This in-flight test is an effective method for detecting leaks in the engine's induction system. It is best accomplished in level cruise flight at about 5,000 feet MSL.
1. Mark #5 High MP Test: Start WOT and full-rich mixture. Write down the EGT for each cylinder.
2. Low MP Test: Reduce MP by about 10 inches and again write down the EGT for each cylinder.
3. Mark #6 (Stop Logging)
Cylinder EGT #1 #2 #3 #4
High MP
Low MP
Diff.
Disregard the absolute EGT values. Instead, calculate the change in EGT ("delta") for each cylinder between the high-MP and low-MP tests. Ideally, the amount of EGT change should be roughly the same for all cylinders. If one cylinder (or two adjacent cylinders) exhibit(s) significantly less change than the others, suspect an induction system leak affecting that cylinder (or those adjacent cylinders).During the high-MP test, the induction manifold pressure is very close to outside ambient pressure, so any induction leak will have little or no effect on engine operation. During the low-MP test, the manifold pressure is significantly lower than outside ambient (by about 10 inches), so any induction leak will cause the affected cylinder (or cylinders) to run substantially leaner than the others, resulting in a smaller drop in EGT than the others.

-John

Kahuna said:

My guess is you have an intake leak that you are only seeing in low MP.
On the ground at idle, spray all intake tubes, gaskets and things with any ether based spray fluid and it should expose the culprit.

Click to expand...

Thanks for the input guys!

I'll check the #1 induction tube tomorrow. If everything looks normal, I'll do the flying EGT test with high and low MAP.
If that test is normal, I'll check the FF divider.

Stand by for updates.

Again: your input is highly appreciated guys! What a great forum! (my thoughts for the zillion time.... )

An update

Yesterday, before flight; I checked the #1 induction tube: it felt tight and steady, no blue stains and both bolts torqued to spec.

I also checked the other three intake-tubes; all ok there too.

I then sealed the bottom intake with high temp RTV, just to be sure it wasn't any leak.

In flight I did the flight-test mentioned by Boomer:

Here's at full throttle:





Here's MAP reduced with 10:




As you can see, there's no EGT spread.

The # 1 EGT on ground is still 100-200*F higher that the other three EGT's when leaning.

Any ideas what to do next? change the spider maybe?

Remember, when at low power settings( run up, final approach etc) the egt readings can be very erratic. My understanding is that this is caused by the turbulence in the exhaust pipe at lower power settings. Check your engine data when taxing in after a flight or on short final, you will probably see the same indication. Downloading the data to savvy analysis and looking at the graph during this phase may show it quite clearly.

2nd vote for flow divider

Some flow dividers have a V-notch that comes into play at low flow rates. A little bit of dirt will alter the flow quite a bit!

Flow Divider Test

How would one test for a 'spec' in the flow divider 'V'?

Flow test (boost pump) with closed throttle?

My flow test with WOT showed consistent (same) level for all six injectors.

Cyl 2's EGT runs 100 - 150*F hotter than other cylinders in 900 to 1200 rpm on ground. Cyl goes very high when eng throttling back for landing.

Have cleaned injectors, new injectors, cleaned divider, installed new plugs, replaced gasket on #2 intake pipe. No chg; same issue.

Fresh ideas welcomed.

EGT

Can't say I ever look at the numbers when on the ground. Just check to see that they all go up when you shut off a mag.

Presuming your ignition systems are operating properly, if you lean to roughness and that cyl does not misfire first, it is not an over-lean issue.

You have not mentioned roughness. At idle that is telling you something.

After you have satisfied yourself that it is not a lean cyl, i'd ignore it on the ground.

Break in

And with only 8hrs, I woulds not idle a minute longer than needed.

Thanks for the inputs guys.

Here's a few answers to your comments:

The engine runs smooth on ground from about 900 RPM.
Below 900, and down to idle (750-800 RPM) it runs alittle rough, but no more than other engines at idle that I've heard, nor does it run more rough than my other -7.

All EGT's have not shown any erratic indications, just the normal up and down values together with throttle movements and/or mixture.

The engine has now 13 hrs on the tach and it has been running VERY nice from the very first start.
Very little vibrations, stable engine indications and it feels smooth and nice.

I'm still running it hard according to the Lyc breakin SB.
No sign of CHT drop yet, but the oil consumption is down to 0,1 litres/hr. During the first hour, it was 0,5 litres/hr so it looks to me that the engine is well on it's way to breakin.

I'm limiting two things to the absolutely minimum: ground time and idle in the air.
The only time I'm idling in the air is actually the flare... and even then I don't go all the way to idle, I'm carrying alittle power and goes to idle a few sesc after touchdown.

To avoid low powersettings in the air when slowing down for landing, I'm flying longer finals with full flap, thus the powersetting can be as high as possible.

Anyway: here's a pic taken on long final the other day, tach at 10:98, MAP at 19%. As you can see, there's no EGT spread here either.




So I guess the next step is to check the spider. Does anyone have a pic how it looks inside?