Cotton AeroVee 0795

[Bryan Cotton]

One other thing I've done is to wrap the barrels of my under-plug CHT sensors with some silicon self-fusing tape. My thought is there is lots of cool air up there and I don't want it blowing on the barrels of the lug, because that is where the type K thermocouple termination has to be. This does nothing to improve temps, but may possibly give more accurate readings.

To complete the post above, the baffling work I did starts near the bottom of this page:
viewtopic.php?f=7&t=7279&start=50

Performance gains, that I believe came from the intake mods, are documented here:
viewtopic.php?f=39&t=578&start=1570

A quick recap:

Some post-flight observations:
1) We were turning 3400 at 80kts in the climb.
2) I saw 1000 FPM solo and 800 two-up. Steady, not a stick thermal.
3) CHTs were all under 300.
4) Oil pressure at 3400 was 72-75.
5) Oil temp got to 212 during my climb. About 3000 AGL solo and 2000 AGL dual.
6) EGTs much more balanced. With #1 at 1350, #2 & #4 were about 1270. #3 was a little over 1300.
7) Radio didn't transmit
8) Panel lights inop.

Modifications:
GPAS manifolds
Cotton Cooler (tm) cylinder baffles
Bonded in RH gear leg
Cleaned up cooling fins (EMPI heads from Sonex)

It really ran and flew great!

[Bryan Cotton]

Two flights yesterday, and today the secondary failed the mag check. By watching EGTs we could see it was the #1 cylinder. Went to check the #1 plug and the wire failed at both ends. I had a spare. No difference though, so we swapped the #1 and #2 plugs. #1 still bad. Then we swapped the wires at the coil, and the problem went to the #3 cylinder. So I think we have a bad coil. I have two on order from Sonex and also looking at Dyna 3ohm coils on ebay as a backup.

[DCASonex]

Insulating your thermocouple leads will definitely improve accuracy. The leads draw heat away from the point where the thermocouple is so that it can more accurately can be seen measuring as the temperature at some point along a metal line between the actual head and the cooler wire. Did that on my Jabiru and CAMit 3300s found it raised the observed CHTs by 15-20°F After discussing this with Ian Bent at CAMit he did same and found about same results. He made insulated CHT leads standard on his engines.

David A.

[bvolcko38]

Your more balanced EGTs... do you attribute that to the notches cut into the intake manifolds? Or something else?

[Bryan Cotton]

Your more balanced EGTs... do you attribute that to the notches cut into the intake manifolds? Or something else?

I'm thinking the goodness of more performance and better balanced EGTs may be from the manifolds. How much from the notch and how much from the swoopiness of the GPAS manifolds, I'm not sure. I've changed a lot of things at once.

I bought those manifolds from Graeme a couple of years ago. He complained about how unfinished they were when he bought them new, and then did an awesome job cleaning them up.

[petep]

I have tried the AeroVee intake elbows with and without the spacers and the Great Plains elbows with the gasket and found no noticable difference in the EGTs with either,

[Bryan Cotton]

I'd be curious how the EGTs would be if I removed the center divider in the Aeroconversions manifold. Turn it into one big plenum. Also begs the question - is my better performance due to swoopy manifolds or even EGTs? The forward cylinders are not running overly rich anymore.

[Bryan Cotton]

I flew a half hour of aerobatics early this morning. On the way home, while crossing over the field in level flight, 3000', I decided to try a WOT run. Pulled over 3700 RPM but didn't see much over 120 kts. It may have accelerated further but the high RPM was scaring me. Sounded great though! It's like a different animal.

Climb to 6000 MSL from 850 took about 7 minutes.