Hello. I just purchased a 2016 Glasair Sportsman. The engine and airframe have 130 hrs. Engine is running great and just finish flying it from WY to CA.
Engine is a Mattituk tmxo-360 with Vetterman exhaust and has the EFII fuel injection and electronic ignitions.
The number 1 and 3 CHT’s are running warm compared to the 2 and 4. I’m having to run the engine rich to keep the temps at 400 deg in cruise. And I really need to keep and eye on the temps on any type of climb.

The 1 and 3 cylinders are running about 30-35 degrees hotter than the 2 and 4. But even in a climb the 2 and 4 temps stay pretty steady where the 1 and 3 climb.

The engine is baffled nice and tight and I can’t see where any intake air is escaping outside of the box except 1 area.
Right behind the #4 cylinder there is a 3” duct that has 3” scat tube coming off and going down to a plenum that’s is flowing air through the oil cooler.
My oil temp is right around 206 deg.

Do you think if I add a NACA duct to my cowl and run the 3” tube to the NACA and close off the 3” duct behind the #4 cylinder that this will sort out my temps?

Looks like the blue baffle seal is tilted outwards along the side. Are all the blue baffles tilted inward and sealed tight to the top cowl when the cowl is installed?

There should be no need to install a NACA duct. Pulling oil cooler off a rear baffle is common.

Check that all baffles are sealed tight and no air is leaking through from top to bottom other than through the cooling fins. Shine a light up from the bottom and seal any gaps with RTV. Look closely behind the spinner and around the engine mounts. Could also do a gami spread check and verify all fuel injectors are balanced.

Could also try adding an an960 washer or two behind the #3 cylinder. Remove the bolt holding the rear baffle on, right below the oil cooler duct, slide a washer or two in there to create more air flow down behind #3. Trial n error, YMMV,

Id say first and foremost make darn sure all of the top rubber baffles are sealed tight to the top cowl, facing inward with no puckers or gaps. If you need to redo them use McFarlane cowl saver material.


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The blue silicone seal is pulled back in the pic so I could get a straight down picture of the figment of the baffles.
The baffle box is engineered for a very tight fit. It’s definitely one of the better ones that I have seen.
I’ll look into the gami spread check you mentioned.

You mentioned you recently purchased the aircraft; are you familiar with the electronic ignition system and where the timing is set and whether or not the timing is variable?

I’ve found with variable timing electronic ignitions, in cruise, as the timing advances, CHTs increase and EGT’s decrease (better combustion and power). The downside is higher CHTs, so if there is any issue with cooling in the first place, whether it be air flow or fuel flow, it doesn’t get better in cruise as might be expected with a standard 25 BTDC setting and lower power/higher speed.


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I have chatted a little bit with Robert from EFii but on Monday I am going to call him. Hopefully we can walk through all the settings on the injection system as well as the ignition system.
I read an article where someone with electronic ignitions was having high CHT and it ended up being they were set to far advanced.
Here is a picture of the temps. Both CHT and egt in cruise. I leaned out the engine until I was just above the 400 deg.

I feel like I should be able to lean much more as my fuel burn right now is much higher than It should be for a 360.

The climb out is what is hurting me the most. I’m not able to get near what I should be as I have to richen up the engine a bunch and climb at a min of 105knts or the temps on those two cylinders jump up very quick.

Looking at those CHTs vs EGTs id say your timing is advancing too far. That is really hot for 10,500. Or you’re running real rich and max power.

For what its worth, Vans RVs with similar setups and cowl inlet size probably typically climb out at 120 KIAS or more to keep temps down.

The phenomenon of 1 and 3 higher than 2 and 4 has also been well documented, this can be the disruption of airflow due to the position of the butterfly on the air intake. I’d ask EFII if the diameter of their throttle body is the same diameter as the hole in the bottom of the O-360 sump. A step in the difference of diameter can disrupt the air flow and fuel oil mixture to each cylinder. Luckily with fuel injection can be adjusted with the individual injectors vs. a carb you’re basically hosed; i know a fix for that bit thats another story.


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Wait a sec; Is that 86% power in the upper left? Jeez you got a turbo on that thing too! If you’re running 86% power at 10,500 no wonder your CHTs are high! You need to pull that power or prop back some. We need more pics of your cruise settings.


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I was trying all types of power settings and prop settings. Also rich and lean. Had 8.5 hrs of flying to mess around.
The pic I posted above was full power at 10,500 feet. Manifold pressure at 21” and prop pulled in to 2,350rpm.
Things didn’t change much more than a few degrees. The only thing that gets those two cylinders to drop in temps is to richen up the engine quite a bit. To get to around 390 in cruise I had to richen up to a burn rate of 11.9 to 12.6 gph.

I’m hoping it’s something as simple as ignition timing.

Just seems weird the 2/4 cylinders never climb and are very easy to control.

Definitely odd that you’ve got a hot 1/3. I’ve got a Pacer with an RV cowlings and I’ve been chasing high oil temps and a hot 1/2 in climb for almost as long as I’ve owned the plane.

The fact that 2/4 are where they are plus high oil temps makes me thing you might have a couple of problems going on. Step one, I’d reduce your part throttle ignition advance. I’m running P-Mags, but mine are set to 25° BTDC (same as a magneto on these engines) at high power settings, with a max advance of ~34° BTDC (this is the advance limit for part throttle/lower MAP operations like your cruise scenario).

I’d also be willing to bet you’re either not fully evacuating your lower cowl (easier to fix) or not achieving a good pressure recovery in your upper cowl (once you’ve got the seals all right, this one is harder to fix).

Can you post some pictures of your cowl exit? That’s a good place to start.

It also doesn’t look like you’ve got a stand-off for the limited cylinder fin depth on the backside of the number 3. Google “baffle mod danh site:vansairforce.com” to see the easy and hard fixes for that problem. I have the easy version installed right now and that dropped my #3 CHT by between 15-25° in cruise. In the future I intend to pull that baffle section and install a “bypass duct” like in here: https://vansairforce.com/community/show ... stcount=24

Hot #1 can be worked by lowering the ramp in front of that cylinder, but that’s major baffle rework. I’d hold off until you drop the max advance some and see how it looks.

I put a couple pieces of tape over the 3” hole. Left a 1” space so I could still flow some air to the oil cooler.
Took the plane around the pattern and did not see any drop in cylinder temps on 1/3.

I will get out to the plane and take some better pictures of the exit in the cowl. It has a round exit that is dropped down out of the cowl. The exhaust pipes also come out of this area. I’ll post a pic that shows this until I can get a better one to post.

I’m thinking the timing may also be to far advanced. I have read the manual on the EFII system but not exactly sure how to program so will call them up and have them walk me through it.

I read up on the duct mod described above. Lots of info on the RV forums on how to do it.
I installed the washer to see if it would help but did not notice anything. Tomorrow I’ll pull the back baffle and make an actual duct and hopefully that does the trick.

I took out the little 90 deg deflector on the front of the intake ramp this afternoon and ended up with a 22 deg drop in temps on cylinder 1. So 1,2,4 are all within a deg or two now. Cruising right around 378 deg.

If I can get #3 to drop down to those temps I would be happy. It’s running at 400-407 compared to the other three at 378.

Here is a before and after pic of the piece I took out.

Does it have fuel injection or carb? You mention tmxo-360, which is a carb, but then you mentioned EFII fuel injection and electronic ignition. Does it indeed have EFII fuel injection too? (You can haveEFII FI, EI, or both)


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Yes it’s a TMXO360 with the Full EFII fuel injection and electronic ignitions.

Built the #3 cylinder duct like the RV forums talk about. I’ll install it on Friday when I get off shift and give it a try. Hope this does the trick.