CHTs

[RVG8tor]

I am looking for some advice. I only have 7 hours on my new engine and plane but I am starting to see what might be issues. From the start my CHTs have never gone above 380 and that is only on #4, it helps that the OAT is 38-43. The odd thing is #1 and #3 run 335 while #2 runs 350 and #4 360ish. I would have thought #2 would run cooler than #3 and #4.

As for #3, I have a washer that holds the rear baffle out a bit and I put foil tape over the lower half of the heat muff port. I covered the heat muff port some since I read that choking the flow will help gain some heat, for now i fell like I have inadequate heat but that is another matter.

So since the left side of my engine runs warmer CHTs would I be correct in assuming I must have some sort of baffle leak on that side. I do have the larger 8432R Oil Cooler so perhaps that is robbing too much air? I did RTV the upper and lower slots of the cooler to make sure the air goes through the cooler. The Oil Temp stays rock solid at 180 unless I climb and then it will go up to 220ish. I am grounded due to the weather so I thought I would look for potential fixes.

Too early to tell on the beak-in but in 7 hours I have used less than a quart, just over half to my uncalibrated eye on the dip stick.

So should I keep flying and try to balance the temps after say 25-50 hours? I basically climb shallow (110-120 kts) then cruise 75-80 % for as long as I can which due to weather has only been an hour each flight I would like to get these flights up to say 2 hours or more. Of course at 14 GPH that is about the limit.

I have not been leaning at all, not really sure when one should start that on a new engine, everyone just says run it hard. I have one guy that thinks I should do nothing but cruise hard for 50 hours, no stalls, slow flight or touch and goes, the only reduction is for a very shallow decent for one pattern and landing.

Thanks for the advice. Oh, EGT runs 1300 or less on takeoff and in cruise. my #1 is off a bit from the others but I think I might have messed up its location compared to the others since it sits in the curve of the #1 exhaust. I was putting them 2" below the exhaust pipe flange. The other EGTs are within a few degrees of one another.

[alpinelakespilot2000]

Mike,

I'm no expert here at all but I don't see where you have any issues. First, all of your temperatures are well below any danger zones. Second, you're still very early in your break in where you have to expect temperatures are going to be higher than normal. Third, having all of your CHT's within a 25-degree spread seems quite good to me, especially at this stage. My vote would be to not worry at this stage, b/c it really looks like you're doing pretty good. If temperatures start going up significantly when the OATs start going up then you may find you need to do something about it. Again, however, by the time OATs start going up significantly your engine will probably be better broken in and, consequently, you may not see significant rise in engine temps.

FWIW on the leaning thing, I checked with Aerosport Power after I had about 16 hours and they said go ahead and start leaning. However, this may have been specific to my type of engine, type of cylinders etc. What you seem to be learning, is that everyone has their own theory about the best way to break in an engine. I chose just to follow my engine manufacturers advice (65-75% power) and have tried not to lose any sleep over it after that.

Glad to see you're getting some hours on it. Ironically, here on the east side we've had lots of fog and low clouds for the past week. I need to move to Olympia I guess!

[Toobuilder]

Originally Posted by RVG8tor

I am looking for some advice...

Funny you should ask... There are some engine and baffle combinations that have fundamental flaws, and plenty more that are only "adequate"...

Here's what I did (with a bonus from Dan H):

http://www.vansairforce.com/communit...ad.php?t=93949

[jrs14855]

Some experts contend that the left side cylinders will run hotter because of the spiral flow behind the prop being less efficient on the left side.
Mike Busch has addressed CHT in great detail in some of his articles. I don't remember his exact numbers, but temperatures around 300 are undesirably low. I think around 360 is optimum.
You may be able to improve the cabin heat by wrapping some screen door springs arount the exhaust inside the heat muff. Another way is to weld some studs to the exhaust inside the muff. Some factory airplanes do this. You might also try restricting the heat muff incoming air just a bit to give it more time to warm up.

[Toobuilder]

I'll admit that 360 CHT is not a bad thing, but we must also realize that correctly baffling an air cooled engine is pretty important. Unlike with liquid cooling, the CHT probe is only measuring one specific area of the head. If you have a situation like I did, there is a whole section of the head that is not getting any airflow at all, so there is a pretty good chance that area is significantly different that what the probe sees.

So what you really want is uniform flow through the fins of all cylinders, THEN control temp by either throttling the cowl inlet or outlet.

[Wayne Gillispie]

Mike,

Everything sounds good. You may want to start noting your #1 EGT temp on initial climbout, then as you ascend, lean occasionally to maintain that approximate temp. Also it won't hurt to lean agressively on the ground and will keep your plugs cleaner. Have fun!

[RetiredRacer]

Congratulations on getting it into the air Mike.......Well done!

[Greg Arehart]

Burning 14 gph sounds like a lot of fuel flow out the exhaust to me. I would at least lean the engine to be burning more like 10-12. You should still be well on the rich side of peak and saving a few $$.

My opinion only.

Greg

[N427EF]

Mike,
Congratulations on getting your 8 in the air.
By all accounts you don't seem to have any big problems with your installation.
As far as breaking in the engine, follow the engine builders advice or else you'll eventually suffer "analysis paralysis".
There is more than one way to do it but the basic concept stays the same.

There is some really bad advice out there:

I have one guy that thinks I should do nothing but cruise hard for 50 hours, no stalls, slow flight or touch and goes, the only reduction is for a very shallow decent for one pattern and landing.

The best advice comes from people that have done it a few times.

[jthocker]

Mike,
Your numbers sound great! You have NO problems, fly, fly fly!
Time to enjoy the plane, you've done everything right and you have a good installation.
Congrats once again!