Aerovee one EGT high

ArchiveBot · March 23, 2024, 5:00am

Aerovee one EGT high

Posted: Sat Mar 23, 2024 4:54 pm

by Bryan Cotton

Hey all,
Looking for some thoughts from the Aerovee brain trust. I have one cylinder (#1, back left) going insanely high, like over 1500F. This is during a full power climb. If I enrichen it to get it below 1400, the engine runs poorly as the other cylinders are too rich. The others average about 1200 in climb. In cruise it will run below 1400, but the others are 1000-1200. I have swapped the EGT probe from the #1 and #2 cylinders and the high temperature stays with the #1 cylinder. I’ve also swapped inputs on the MFD and again the high temperature stays with #1. So I believe it’s too hot and I’m not seeing an instrumentation error.

This happens on just the mags, or on both ignitions. I did not try on the secondary ignition only.

I did reseal the left intake manifold, but no change. It seems an induction leak would be a potential cause of a high EGT.

In reading other forums a bad exhaust valve is listed as a possibility, or head gasket, or cylinder issue.

My recent compression test was 116/119/126/125. Last year was 119/121/125/119.

I’m thinking of pressuring the intake with a shop vac to look for a leak with soapy water. Otherwise I’m thinking of pulling the head to have a look.

Any thoughts welcome.

Edit: I also checked the #1 valve last on the exhaust.

Re: Aerovee one EGT high

Posted: Sat Mar 23, 2024 6:39 pm

by gammaxy

Don’t know if this would cause it, but is the exhaust gasket on that cylinder good? I’ve had to replace them more often than I expected.

Re: Aerovee one EGT high

Posted: Sat Mar 23, 2024 7:03 pm

by Area 51%

Screw the electronics…What story do the spark plugs tell?

Re: Aerovee one EGT high

Posted: Sat Mar 23, 2024 7:43 pm

by Bryan Cotton

I’ll check the exhaust gasket. They are the originals.

Plugs are coming out, stand by…

Re: Aerovee one EGT high

Posted: Sat Mar 23, 2024 11:50 pm

by n502pd

Another thing to look at is the intake manifold gasket security. if one bolt isnt as tight as the other, there may well be just one cylinder sucking air. I have saftied those bolts and have not had any of then come loose any bit. The other thing to consider is the probe may be at fault, if nothing else is found. The plug will also tell you , comparing to one of the other cylinders plug, if cylinder is actually very lean. Pleas e let us know what you find!

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 8:44 am

by Bryan Cotton

n502pd wrote:Another thing to look at is the intake manifold gasket security. if one bolt isnt as tight as the other, there may well be just one cylinder sucking air. I have saftied those bolts and have not had any of then come loose any bit. The other thing to consider is the probe may be at fault, if nothing else is found. The plug will also tell you , comparing to one of the other cylinders plug, if cylinder is actually very lean. Pleas e let us know what you find!

Joe,
I redid the intake sealing on that side, so it was secure. Maybe there is a warp or crack, I’m not sure.
I did swap probes, and the high EGT stayed with cylinder #1.

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 10:11 am

by Bryan Cotton

secondary plugs.png (260.03 KiB) Viewed 3342 times

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 11:22 am

by pappas

What are the corresponding CHT’s while #1 is displaying the unusual high temp?

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 11:49 am

by Bryan Cotton

Lou,
My #1 CHT failed. It reads around 100F after the engine warms up. Pretty much everything else was under 200F. It was cool out. Oil temp was 161.

Edit: I assume it has failed. I’m going to do a differential compression test today.

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 12:37 pm

by BRS

Bryan, you didn’t mention so I won’t assume. You did verify both the top and bottom plugs are firing ok - right? Only one plug firing will give a hot egt as fuel burns slower and gets out the exhaust before it’s ready.

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 12:48 pm

by Bryan Cotton

BRS wrote:Bryan, you didn’t mention so I won’t assume. You did verify both the top and bottom plugs are firing ok - right? Only one plug firing will give a hot egt as fuel burns slower and gets out the exhaust before it’s ready.

Brock,
Mag check has been good. Generally I switch to the primary ignition only by 1000’ AGL or so.

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 2:37 pm

by kmacht

How are the CHTs. Is the side with the higher EGT also showing increased CHTs? If not then It could be as simple as the placement of the EGY probe in the exhaust. Just a slightly different angle or distance than the others could certainly cause a 100f difference. CHTs are what you really need to monitor and worry about. When they get too high you start damaging the head and can loosen up the valve seats. EGTs are less about the absolute number displayed and more about the relative changes when leaning. If your CHTs are good I would keep on flying and just periodically pull a plug to make sure it looks good and maybe borescope the valves at each oil change.

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 3:29 pm

by Bryan Cotton

The #1 CHT has been reading 100F. It seems faulty, 200-300 is more normal for me.

The troubling thing is the big change from normal after 200+ hours.

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 3:50 pm

by BobDz

Bryan

If I remember correctly, didn’t you change the needle in the AeroInjector? Richer? Or leaner? Did the high EGT start after that?

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 4:35 pm

by Bryan Cotton

Bob,
Here is the sequence. First I did the annual and all that entails:

torque heads
adjust valves
change plugs
compression test

Then, some extra credit:
5) re-shim engine
6) redo main seal/polish flywheel surface
7) Fresh air induction

So I noticed the EGT being higher after fresh air induction. Makes sense, more air and the same fuel means leaner. So I adjusted my #2 needle a few times, then swapped to #2.5

It’s entirely possible the high EGT on #1 was caused by something else and I attributed it to the fresh air induction. Maybe I have a bad or leaking spark plug on the #1 cylinder.

I’m halfway through my differential compression test. So far I have:
#1 80/72
#2 80/67

These are cold and I hear air in the crankcase, so it’s getting past the rings. The numbers don’t seem that bad.

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 5:08 pm

by Mike53

Mike Busch has some thoughts on this.https://www.savvyaviation.com/unbelievable-compression/

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 6:10 pm

by Bryan Cotton

Thanks Mike!

Final results:
#1 80/72
#2 80/67
#3 80/64
#4 80/74

The adapter was not threading happily into #3 and I suspect that lowered the reading a little.

Boroscope next.

Re: Aerovee one EGT high

Posted: Sun Mar 24, 2024 6:52 pm

by Bryan Cotton

The valves look good. I’m going to swap the spark plugs on the #1 cylinder. They are new at annual and maybe one is faulty, or leaking even.

Re: Aerovee one EGT high

Posted: Mon Mar 25, 2024 6:29 am

by RodgerC

It may be worth checking that you don’t have interference between valve adjusters and the rocker cover, due to an excessively compressed cork gasket.

Re: Aerovee one EGT high

Posted: Mon Mar 25, 2024 9:18 am

by Bryan Cotton

RodgerC wrote:It may be worth checking that you don’t have interference between valve adjusters and the rocker cover, due to an excessively compressed cork gasket.

Thanks Rodger. I’ve got rubber gaskets and there are definitely no witness marks on the inside of my valve covers.

Re: Aerovee one EGT high

Posted: Mon Mar 25, 2024 9:42 am

by Onex107

The 80 psi leak down test will pinpoint a leaking valve.

Re: Aerovee one EGT high

Posted: Mon Mar 25, 2024 9:44 am

by Bryan Cotton

Onex107 wrote:The 80 psi leak down test will pinpoint a leaking valve.

When I did the 80 psi leakdown test yesterday I had no air leaking through the valves, just the rings.

Re: Aerovee one EGT high

Posted: Mon Mar 25, 2024 11:30 am

by BobDz

So…
High EGT can be caused by an excessively rich mixture. Fuel is still being burned when the exhaust valve is open. This scenario might also show lower CHT. But I am at a loss to explain why it would only be happening in one cylinder, and why it would just start randomly. Is the exhaust valve staying open longer than it should be? Maybe stuck slightly open?

Re: Aerovee one EGT high

Posted: Mon Mar 25, 2024 12:15 pm

by Bryan Cotton

BobDz wrote:So…
High EGT can be caused by an excessively rich mixture. Fuel is still being burned when the exhaust valve is open. This scenario might also show lower CHT. But I am at a loss to explain why it would only be happening in one cylinder, and why it would just start randomly. Is the exhaust valve staying open longer than it should be? Maybe stuck slightly open?

Bob,
When I enrichen the mixture the high EGT comes down, but the engine starts running poorly. So it seems the one cylinder is lean.

Re: Aerovee one EGT high

Posted: Mon Mar 25, 2024 12:29 pm

by BobDz

Bryan Cotton wrote:

BobDz wrote:So…
High EGT can be caused by an excessively rich mixture. Fuel is still being burned when the exhaust valve is open. This scenario might also show lower CHT. But I am at a loss to explain why it would only be happening in one cylinder, and why it would just start randomly. Is the exhaust valve staying open longer than it should be? Maybe stuck slightly open?

Bob,
When I enrichen the mixture the high EGT comes down, but the engine starts running poorly. So it seems the one cylinder is lean.

And your compression tests don’t show a stuck / open valve.

Re: Aerovee one EGT high

Posted: Mon Mar 25, 2024 12:48 pm

by Bryan Cotton

BobDz wrote:And your compression tests don’t show a stuck / open valve.

Correct

Re: Aerovee one EGT high

Posted: Thu Mar 28, 2024 11:14 am

by Bryan Cotton

Just to link this to another relevant thread, check this out:
viewtopic.php?f=7&t=3725&p=58226#p58226

I may have caused the imbalance with my asymmetric introduction of fresh air.

Re: Aerovee one EGT high

Posted: Thu Mar 28, 2024 11:55 am

by BRS

When I did the cold air intake on the R2300 using a Rotec MKII carb, Rotec cautioned about elbos near the carb. There were none but but I did go ahead and make a flow straightener to dampen any intake air swirl. Perhaps something like this might be helpful.

Re: Aerovee one EGT high

Posted: Thu Mar 28, 2024 1:03 pm

by Bryan Cotton

I had considered that Brock but not sure how I would implement it given I don’t have a flange mount. For now I’m going to remove my fresh air induction and verify the issue goes away. Then I’m going to add a second input to make it symmetrical. I’ll fabricate a T or Y pipe to split the flow.

Re: Aerovee one EGT high

Posted: Fri Mar 29, 2024 10:41 am

by Bryan Cotton

So I flew this morning with my cold air induction removed and I am able to climb to 4500’ and keep it below 1400F. The other cylinders are around 1200F. I’ve lost some RPM in the climb with the loss of fresh air.

So this brings up an interesting thought - it seems I can steer the mixture left/right by messing with how the air goes into the filter, much like Michael (rizzz) observed in the other thread. What I need to do is to steer it the other way, and I can get my left and right aft cylinders in balance. That should allow a little more leaning overall and better performance. I am going to put another input into the air filter shroud, symmetrically, on the other side. I’ll do some flight tests to figure out how to balance airflow between the two sides and achieve nirvana.

I also have a set of Great Plains intake manifolds that I bought from Graeme Smith, and I may try those to see if it balances fore/aft better than the stock manifolds. I did a quick check last week and it appears I will be able to bolt them on and get them to line up with the intake tube. These are the manifolds I have: https://www.greatplainsas.com/0251-/-bu … ystem.aspx

For now I’m leaving it as is until after the eclipse.

ArchiveBot · March 23, 2024, 5:00am

Re: Aerovee one EGT high

Posted: Tue Apr 30, 2024 11:55 pm

by Bryan Cotton

BRS wrote:When I did the cold air intake on the R2300 using a Rotec MKII carb, Rotec cautioned about elbos near the carb. There were none but but I did go ahead and make a flow straightener to dampen any intake air swirl. Perhaps something like this might be helpful.

So here is my shot at it. I figure my fresh air is blasting the side of the air filter and making the flow inside hokey.

Screenshot_20240430-223706~2.png (537.73 KiB) Viewed 2651 times

It just slides in, a tight fit.

Screenshot_20240430-223744~2.png (551.57 KiB) Viewed 2651 times

Unfortunately when I took the first picture I hid the bottom of it. I’ve got a half circle cut in the bottom of the vanes, so the air at the back of the filter can mix. I’ll get another picture later.

Re: Aerovee one EGT high

Posted: Wed May 01, 2024 7:01 pm

by Bryan Cotton

Here is the bottom of my flow straightener.

Re: Aerovee one EGT high

Posted: Wed May 01, 2024 8:39 pm

by mike.smith

You need to get a good reading on the CHT. That’s all the matters, really. If the CHT is in line with the others, and within the proper range, then there is likely nothing wrong with the cylinder, so it would be a sensor or display issue with the EGT.

Re: Aerovee one EGT high

Posted: Wed May 01, 2024 9:18 pm

by Bryan Cotton

mike.smith wrote:You need to get a good reading on the CHT. That’s all the matters, really. If the CHT is in line with the others, and within the proper range, then there is likely nothing wrong with the cylinder, so it would be a sensor or display issue with the EGT.

My CHTs have never been matched, or particularly hot. But in troubleshooting the sensor this is what I’ve done:

swapped the left front and left rear EGT probes. High EGT stayed with the cylinder.
swapped the two inputs into the MFD. High EGT stayed with the cylinder.

If I remove my fresh air induction, the problem goes away. When I put the fresh air induction back, the problem comes back. I’d like to find a way to keep it as I am gaining about 150 RPM in climb.

From my borescope inspection, the hot (#1) cylinder definitely looks different on the exhaust valve than the others.

Re: Aerovee one EGT high

Posted: Thu May 02, 2024 11:56 am

by WaiexB22

I read through this and I have a few thoughts/considerations:

I believe your previous intake was a filter mounted directly on the aerocarb. This would have pulled from the hot “low pressure” area in the belly of the cowl. Your intake would only reduce air pressure and promote the flow of cooling air through the cylinders. With the cold air setup you are no longer pulling intake air from this area, increasing static pressure here, and reducing cooling flow. If you can open the outlet on bottom easily you could test this theory to see if there is improvement. If you have to cut the cowl there’s really no easy way to test that I am aware of.
I understand the idea of the elbow at the intake causing uneven distribution of flow through the aerocarb; however, i do not believe it would not have went away during subsequent tests with the elbow and no cold air supply. Let us know if the flow vanes help any, I’m very curious about this one.
You said you reshimmed your engine. Is it possible you inadvertently created a gap in the cooling baffle seals that is allowing a bypass of cooling air between the seal and the cowl.

Good luck!

Re: Aerovee one EGT high

Posted: Thu May 02, 2024 1:38 pm

by Bryan Cotton

WaiexB22 wrote:I read through this and I have a few thoughts/considerations:

Good luck!

Robert,

I’ve had two air filter configurations. One directly attached and one with the elbow. The only reason I swapped was because I didn’t have the K&N RC-1980 safetied. It fell off and melted on the exhaust. It is no longer available. No real difference between the two with respect to temperatures, etc. Yes it was pulling hot air from the low pressure side of the cowl for either filter. So far I have not seen any CHT or oil temperature issues with the addition of fresh air induction. Summer is coming though.
I don’t think the elbow is the cause. I think it is the blast from the fresh air right on the surface of the filter causing turbulence inside the filter. This is my current theory.
The baffles still fit nicely. I was a nutjob about sealing for cooling reasons.

I believe the high EGT, and the unbalanced EGTs are purely related to uneven air-fuel mixture. Pretty common in AeroVees not counting the turbo models. So it’s not a cooling issue, but a fuel distribution issue.

Still I agree this will reduce cooling air flow which will make our marginal hot weather cooling worse. I have a set of B model side inlets that I’m going to add. But that is another experiment.

Re: Aerovee one EGT high

Posted: Thu May 02, 2024 2:28 pm

by WaiexB22

It sounds like you’re on the right path. I didn’t think the elbow would matter much.

I wish I could have made the side outlets work on my setup, but it would have taken A LOT more work and different radiator(s) that were hard to source, so I do not indent to use them at this time. I think they look really nice.

Re: Aerovee one EGT high

Posted: Thu May 02, 2024 9:43 pm

by Bryan Cotton

My super simple deflectors. Not much surface area is blocked due to filter radius, pleats, and a slight bend front & rear. The rivet tails in the pleats help keep alignment.

Re: Aerovee one EGT high

Posted: Fri May 03, 2024 10:43 am

by Bryan Cotton

A view of my flow straightener via inspection mirror. Test flight after work today.

I originally used pops for the flow straightener. Got to thinking it would be bad if a mandrel went through the engine. I drilled out the pops and installed solid rivets.

Re: Aerovee one EGT high

Posted: Fri May 03, 2024 3:50 pm

by WaiexB22

I have seen what a bolt will do to the inside of a cylinder and you definitely don’t want a rivet in there.

Let us know if it works.

Re: Aerovee one EGT high

Posted: Fri May 03, 2024 8:05 pm

by Bryan Cotton

Test flight - 1415 in climb until I got to 3000’ MSL or so. Awesome RPM, over 3200. At 90kts was almost 3300, but the EGT went to 1430. Way better than before. I’m not done but on the right track I think.

Re: Aerovee one EGT high

Posted: Sat May 04, 2024 5:07 pm

by Bryan Cotton

So I’m making another flow straightener. Here are the parts. I prototyped in flashing.

This is made from 0.016 2024-T3 and AN470AD3-3 rivets.

It slips in like this:

Here it is all the way in. The ends are bent to put some swirl in the flow, hopefully sending more fuel to the left side.

Next up is test, re-bend, and repeat until I’m happy.

Re: Aerovee one EGT high

Posted: Sun May 05, 2024 11:13 am

by Bryan Cotton

So, some results to report. I ran out of time to test it last night due to thunderstorms. Got up early for a test flight, in the configuration pictured above. In that picture the flow is going clockwise a little from the perspective of looking into the elbow. The top tab in the picture is bent to the right, the bottom to the left, and so on. On the first flight the EGT was higher than the last iteration, about 1460 in takeoff climb. I had chosen the clockwise rotation based on my guess of what the airflow needed to do. Since that seemed to make it worse, I bent the tabs the other way, and put a little more bend on them. I was able to keep the high EGT under 1400 in climb. Not quite in balance yet, but about the same as before I added the fresh air inlet. And I’m climbing out at 3250 RPM, rather than around 3050 or so. Definite gains. More tweaking to come but this seems really encouraging. I safetied up the hose clamp and left it in that configuration so Adam could take his buddy for a ride as posted in my photos thread.

Re: Aerovee one EGT high

Posted: Sun May 05, 2024 12:04 pm

by WaiexB22

That sounds promising and seems like you have figured out what is going on.

FWIW I designed industrial piping for a few years right out of college. Sometimes we would use to use something called a “flow straightener” upstream of a measuring device or process in order to redistribute the flow evenly across the cross section. There were fin type, which looked very much like yours. There were also tube type, which was a series of small tubes within the larger pipe. They both did the same thing. Generally, there was lower pressure drop across vanes, but the tubes seemed to straighten the flow more reliably. It would be more difficult to fabricate a tube style without risking ingesting one in the engine. It looks like you have the vanes working well, but could be a consideration for someone in the future.

Re: Aerovee one EGT high

Posted: Sun May 05, 2024 12:29 pm

by Jester504

Do all the cylinders hit peak EGT around the same time when you pull it back from full rich?

Re: Aerovee one EGT high

Posted: Sun May 05, 2024 12:59 pm

by Bryan Cotton

Robert,
I had considered getting some hex shaped flow straightener material and CNCing a circle out of it. I’m not sure if straight is the answer, or just crooked enough to steer the fuel.

Jester504 wrote:Do all the cylinders hit peak EGT around the same time when you pull it back from full rich?

Definitely not. The hot one peaks first.

Re: Aerovee one EGT high

Posted: Wed May 08, 2024 11:04 pm

by Bryan Cotton

In the picture above, the tabs were bent the wrong way - temps got worse. Here is the iteration where they were about as good as before I added fresh air induction.

Screenshot_20240508-215708.png (2.01 MiB) Viewed 2105 times

Here is my next iteration - more swirl in the same direction, to see if there is an improvement.