CHT spread & leaning a new engine?

[Steve Sampson]

The attached data is off a new 160hp O-320 from Aerosport Power. It is noticeable that CHT1 typically runs 15 or 20 F cooler than the average. Is this a big enough discrepancy to make it worth reducing the air hitting it to bring the temperature up a little? Is there any point? Would this have the effect of reducing the temperatures of the others?

After just 8 hrs of running is it too early to make any decisions like this?

I have been told that for break in I must keep the mixture rich. Is the reason for this just to guard the CHTs or are there additional reasons? With the CHT under control I would like to start pushing a little less fuel through the engine.

There is a super set of the data here on my blog.

[cujet]

I feel it is a bit early to start making mods to adjust the CHT on #1.

Be more specific about your leaning procedures. Are you wanting to lean to peak at low altitudes? If so, don't do it, yet. On our BPE 540, we had 4 cylinders with annealed piston rings. Mostly from improper break in. The engine made it 30 hours! New rings/hone job fixed the prob.

If you want to lean it out at higher alt, I believe that would be the right thing to do.

[Steve Sampson]

Originally Posted by cujet

I feel it is a bit early to start making mods to adjust the CHT on #1.

Be more specific about your leaning procedures. Are you wanting to lean to peak at low altitudes? If so, don't do it, yet. On our BPE 540, we had 4 cylinders with annealed piston rings. Mostly from improper break in. The engine made it 30 hours! New rings/hone job fixed the prob.

If you want to lean it out at higher alt, I believe that would be the right thing to do.

No, my question was:
Is the reason for this just to guard the CHTs or are there additional reasons?

I am trying to find out if the only reason they say keep it rich is to stop overheating, or, if there is aditionally, another reason. I think the answer is that it is only about temperature, in which case it makes sense to lean until the temp gets up to say 380F since this is well within limits.

I cant see any reason not to reduce the fuel flow a little provided it stays in the 350/380F range, but someone might know otherwise.

In all honesty I am beginning to look forward to slowing down a bit also. I did 2hrs at 80% power below 2000' It was quite rough at times, but that is a different matter.