I have approx 50 hours on new TMXIO540 from Mattituck with the Vans Baffle Kit. At 21 squared and 15.5 gph all temps are good. At 21 squared and 12.5 gph cylinders 1 and 2 are just over 400. 3 - 6 are around 370's. The differential temp from full rich to peak EGT for all cylinders are within the same range. Therefore I think I have a cooling problem and not a fuel injection problem. I do not have an engine plenum nor a louver installed. Is there any thing I can do without installing the plenum or louver? If not, then which one will give the maximum amount of cooling and which one is the easiest to do.
Van's Air Force
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F1 Evo High CHT's
- Thread starter spmerrell
- Start date
vlittle
Well Known Member
There are several threads on this (example: http://www.vansairforce.com/community/showthread.php?t=15586&highlight=high+cht)
Search for "High CHT" using the Search button.
Vern
Tom Martin
Well Known Member
I have worked on a number to these and I have done some extensive testing and modifying the cooling system. The first thing to check are your inlets. When the cowling comes there are nice flat flanges on the inlets that extend back about three inches. This is good but the problem is that the gradually close the opening which is a worst case scenario. Measure the opening at the front of the inlet and then at the back of the inlet. Aft of these flanges you need to have a gradual curving transition to the top of your plenum whether your plenum is a separte plenum or just the top of the cowling.
Next make sure that your opening is large enough and not too cluttered with hardware.
Also make sure that your baffling material is closing all the gaps possible around your cowling, partularily at the inlets.
My bet would be on the incorrect aft inlet size.
Next make sure that your opening is large enough and not too cluttered with hardware.
Also make sure that your baffling material is closing all the gaps possible around your cowling, partularily at the inlets.
My bet would be on the incorrect aft inlet size.
f1rocket
Well Known Member
What Tom Said!
Yep, me too. I cut my fiberglass inlet openings back and inserted a ramp to the floor of the Van's baffle kit to ramp the air up from the opening to the cylinder. On top, I made sure I had a smooth transition from the top of the opening to the top of the plenum. My cylinders are almost never as high as 380, and that's on a hot day. Oil temps are well below 200 all the time.
You can really increase the airflow on the inlet side by cutting those inlets back to about 1" of the leading edge.
If that doesn't work, I'd work on increasing the outlet size, but I have my doubts that it does much.
Have you removed the burrs from around the fins near the spark plug hole? Some castings have flash in this area and removing the flash has improved cooling dramatically.
Yep, me too. I cut my fiberglass inlet openings back and inserted a ramp to the floor of the Van's baffle kit to ramp the air up from the opening to the cylinder. On top, I made sure I had a smooth transition from the top of the opening to the top of the plenum. My cylinders are almost never as high as 380, and that's on a hot day. Oil temps are well below 200 all the time.
You can really increase the airflow on the inlet side by cutting those inlets back to about 1" of the leading edge.
If that doesn't work, I'd work on increasing the outlet size, but I have my doubts that it does much.
Have you removed the burrs from around the fins near the spark plug hole? Some castings have flash in this area and removing the flash has improved cooling dramatically.
gmcjetpilot
Well Known Member
Baffle gap?
The front right Cyl #1 exhaust valve is fwd or near baffle lower wrap around part of the baffle. You would think being in the front it would get more air and be cooler, but prop wash and baffle being is too high and/or tight (touching fins), can cut air off to the lower (hot) part of the cylinder.
Cyl #2 - front left the cylinder fins are shallow on the intake side of the valve, which is fwd and what the baffle wraps around. Because the fins are so shallow you can really choked air off with too tight baffle to fin gaps. Adding more gap allows more air to the lower cylinder and aft towards the hotter exhaust side of the cylinder. The fins on the bottom are deep. They don't do any good if air can't get to them.
See the following pic I made. Simple fix is add a little gap between the baffle and the fins to allow more air to flow around the cylinder.
Last its a new engine. Is it broke-in? It might take a little more time to build-up the carbon deposits on the combustion chamber, piston top & valves. The deposits act as a thermal barrier like a ceramic coating. A new engine is absorbing more heat when its new. Temps should come down over the next 20 hours, but really consider increasing the lower baffle to fin gap on the front two jugs. If the baffles are too tight it can be a bad thing.
PS: Don't baby the engine, you want to be at +75% power to get those rings to seat.
Baffles (lower) could be choking air flow off.
The front right Cyl #1 exhaust valve is fwd or near baffle lower wrap around part of the baffle. You would think being in the front it would get more air and be cooler, but prop wash and baffle being is too high and/or tight (touching fins), can cut air off to the lower (hot) part of the cylinder.
Cyl #2 - front left the cylinder fins are shallow on the intake side of the valve, which is fwd and what the baffle wraps around. Because the fins are so shallow you can really choked air off with too tight baffle to fin gaps. Adding more gap allows more air to the lower cylinder and aft towards the hotter exhaust side of the cylinder. The fins on the bottom are deep. They don't do any good if air can't get to them.
See the following pic I made. Simple fix is add a little gap between the baffle and the fins to allow more air to flow around the cylinder.
Last its a new engine. Is it broke-in? It might take a little more time to build-up the carbon deposits on the combustion chamber, piston top & valves. The deposits act as a thermal barrier like a ceramic coating. A new engine is absorbing more heat when its new. Temps should come down over the next 20 hours, but really consider increasing the lower baffle to fin gap on the front two jugs. If the baffles are too tight it can be a bad thing.
PS: Don't baby the engine, you want to be at +75% power to get those rings to seat.
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