Phase 1 update...N427DK

[rightrudder]

I'm past Phase 1, but I'm still in "test-n-tune" mode. Happy to say that I finally removed the air dam in front of cyl. No. 1 entirely, and it made a considerable difference, even though it was only extending up the fins about 3/8". No. 1 & 3 temps went from 15 degrees F hotter than 2 & 4 to about 10 degrees cooler, a 25-degree delta!! No I have to cut down the other dam to even things out...it's currently about 5/8", so I'll try cutting it down to 3/8".

The relative temps look good, but the real test will be a climb-out on a super-hot day. On Monday (before this modification), I flew in 94-degree ambient heat, and shortly after takeoff, No. 1 hit 445 F and 3 hit 435!! I quickly reduced climb to about 6 fpm and made sure I was indeed full rich (I was) and the temps came down, though not as quickly as I would've liked. For extra insurance, I've trimmed the cowl exit back by about an inch, so in profile the bottom lip of the "pod" is forward of the firewall. Originally, it was overhanging the firewall to the rear a little.

Credit to BruceH, who said I should probably leave the air dams off from the start in this hot climate...or make them easily removable so you could stick 'em back on for cold days. I think if I ever pull the baffles off, I'll countersink the angle that the air dams rivet to, and JB Weld some #6 screws in there facing forward. Then, you could simply install the dams and secure with nylock nuts.

So glad to be making progress here.

[bruceh]

Originally Posted by rightrudder

I think if I ever pull the baffles off, I'll countersink the angle that the air dams rivet to, and JB Weld some #6 screws in there facing forward. Then, you could simply install the dams and secure with nylock nuts.

Or just slap some aluminum tape on when you need to warm them up more.

[alpinelakespilot2000]

Originally Posted by bruceh

Or just slap some aluminum tape on when you need to warm them up more.

Agreed. What I will also share from my experience is that my CHT's don't remain consistent (relative to each other) across wide OAT spreads. For example, flying a particular power settings on 60 degree days will leave my CHT spread pretty close, but on 80 degree days, the same power setting will result in my #3 heating up quite a bit more than the others. I'm not sure why that is, but for me it means that making air dams (tape or otherwise) is either a waste of time or highly dependent on whatever the OAT is.

[rightrudder]

Good insight, guys. It's rare here to have a day that gets down into the 40s, so tape it is!

I'm sure I'll learn more nuances about the CHTs as I build up the Hobbs time.

[whd721]

Guys,

This is N721WD.

I am at about 43 hours. So far, in the first 43 hours, I have had one engine failure, one Red Cube failure and last week my GDL 39 quit receiving.

[whd721]

It finally worked, I posted an image.

Doug,
When you removed the from air dams did the climb CHT temps drop? In your post before you reached 445 on #1. any improvements?

[bret]

Engine Failure?

[whd721]

Engine Failure? Oh Yes!

Search for posts by whd721 titled "Do not stray far in Phase I". I posted a several page write up in ~ July 2015.

I started Phase I in Dec 2014 and finished Phase I this month. Two first flights and eight months AOG for engine replacement......

This is a learning experience.

[rightrudder]

Whd721, I love your paint (decal?) scheme! You are certainly very unlucky to have that much misfortune in 43 hours. My only scare was some rough running at altitude, because I was so intent on running the engine hard for break-in that I forgot to lean!!

To answer your question, yes, climb temps were down after removing the air dam, but I've only done one flight since and it wasn't a definitive test. It was a far cooler day, and I departed the airport to the south, which requires staying below 2700 ft for quite a while (Ontario airspace). I'll update here on a hot day going to the east or west, where I can do a hard climb to 7500 ft or whatever. In cruise, relative to cyl. No. 2, No. 1 is now about 10-15 degrees cooler where it used to be 10-15 degrees hotter. It's amazing how much of a difference removing a 3/8" lip of metal can make.