Oil cooler opening width dimentions

[n502pd]

OK, another question for this group! As I approach first flight, I have cut the oil cooler opening per plans. I feel that the width is undersized. What are the dimentions being used by those already flying in hot weather? It gets pretty warm on good (otherwise) flying days here in N Texas, and I would rather be over cooled than under cooled. I want to open the width up all the way to the edges of the baffleing for the cooler entrance.What do you fellows say?

Thanks!

Joe

[mike.smith]

Joe:

I have found the opening too BIG. Even flying in 100 deg weather I don't have issues with oil cooling. In cool weather and cold weather I have to cover up a large percentage of the opening or my oil never gets over 150 deg. It will not hurt to have the standard opening during engine break in when things tend to be hotter, but after that I have not needed it.

This spring I plan to move my oil cooler to the top of the engine, and just about close up the cowl hole. Why? In various experiments I have found that the cooling drag through the oil cooler opening, and the resulting positive pressure in the engine cowl, is substantial.

If anything you should make the cowl EXIT LARGER. Read here:
http://www.mykitlog.com/users/display_l ... 4932&row=2

Others who live year round in your region can tell you if they've had any different results than me (I live in New England).

[n502pd]

That is interesting! I will let it be for the time being and see what happens. I have already made the outlet area increased by 25%. Should I have gone larger? I think I have seen the mentioning of doing this on here a while back. thanks for the input!

[wlarson861]

My inlet was plenty big when I had the bottom mount cooler. In cold weather (below 40 F) I made a grill to fit over the inlet that cut the opening down 25 to 30% in order to see warmer oil temps. I think the area called out for the cooling exit at the bottom of the cowl is right in square inches bot the motor mount has a cross tube that reduces that opening's effective square inches. I increased my exit to disregard the tube, that seemed to help the cooling with lowered temps. Also I was caught in the trap that many builders experience in that I expected the engine to run temps like those reported by other builders. I chased heat for at least the first 20 hours making many modifications like the one above. Nothing seemed to change much. After about 30 to 40 hours the engine started to cool the way it should. The engine manual says the engine isn't really broken in until 25 hours. I think it improves after that for at least the net 10 to 20 hours. The biggest effect on cylinder head temps was getting the secondary ignition timed closer to optimum. Good luck on your upcoming test flights.

[mike.smith]

The biggest effect on cylinder head temps was getting the secondary ignition timed closer to optimum.

Agreed.

[mike.smith]

That is interesting! I will let it be for the time being and see what happens. I have already made the outlet area increased by 25%. Should I have gone larger? I think I have seen the mentioning of doing this on here a while back. thanks for the input!

I think 25% extra should be pretty good. As mentioned, you really can't tell the final results until after 25-30 hours on the engine. It's easier to remove material than to put it back! And don't worry about EGTs; just watch those CHTs.

[phenry]

I had been trying to get my CHT's consistently down to a manageable level ever since my first flight (40 hours ago) at the same time trying to get my oil temperature up.
The oil cooler hole I cut in my cowl was as per the plans.
Eventually in desperation I made a small grill that approximately halved the inlet area and everything is now perfect.

[n502pd]

I had been trying to get my CHT's consistently down to a manageable level ever since my first flight (40 hours ago) at the same time trying to get my oil temperature up.
The oil cooler hole I cut in my cowl was as per the plans.
Eventually in desperation I made a small grill that approximately halved the inlet area and everything is now perfect.

THATS very interesting! I have the plans dimentioned size, and from all the replys, I will leave it alone until I sense it is broken in. I do agree that the CHTs are primairly the most important. I also will add a couple of cooling tubes for the top and bottom magnatrons as suggested too. The cowl is still in place in an attempt to allow it to find its home a bit better as the WX warms. I am now upon the task of making some interior pieces to keep the postieror up enough to actually be comfortable! And as soon as my friend becomes available I will get the canopy finished.

Thanks to all responders! Its appreciated!

Joe