AeroVee EGT/CHT split Issue

[Corby202]

A compression check shows similar readings on all cylinders.

As a suggestion was that a leak down test? You could have leaking valves but still get reasonable compression. If you dont have a leak down tester try doing a compression test by hand propping, the slower speed would show up more.

[daleandee]

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[mike.smith]

Hi, Mike:

My suggestions are more broad than specific, and you've probably heard them all, but since I had high CHT/EGT problems (similar to yours, but the spread was not quite as much -- #1 was very, very hot; #3 was hot but not quite as bad. #2 & #4 were OK) early this year and solved them, I'll just throw out what I did. Until I got it sorted out I could only climb at 150-200 fpm to have any hope of keeping the rear cylinder temps in check.

First, my cylinders ALWAYS have different mixtures. I've taken the heads off several times and the front of the heads (2 & 4 cylinders) are much blacker (richer) than the tan colored (leaner) rear cylinder heads. But my engine purrs like a kitten right now, regardless. Instead of the scientific method of changing only one thing at a time, I changed lots of things at once and solved my issues. I can send you pictures of my heads if you'd like.

1. I have a bottom mounted oil cooler. I closed off most of the intake in the cowl by adding a blank off plate over most of the opening. Even in the dead of summer the oil temps this past summer didn't go over 190 or so, and so I could blank off even more. I think the excess air coming into the cowl from that inlet, was helping to positively pressurize the cowl and not let it dump heat overboard.

2. I increased the lower exit air opening in my cowl by 20%. I think that was the single biggest factor in dropping my temps.

3. I retarded the secondary ignition. The only way to check the RPM and temperature spread is in flight. It is totally unreliable to do it on the ground. In the air I first noticed an RPM difference between primary and secondary, of over 100 rpm. I would get on the ground, retard the ignition and go fly again. RPMs would be better, but still 50 RPM or more difference, and high temps. After doing this a few times I finally got the difference in RPMs in flight to be nothing or in the single digits.

4. I swore up and down that I had the mixture arm at the AeroInjector adjusted properly, and checked it many times. I got the proper RPM increase when pulling the mixture back. But I suspected I still was not getting the mixture to actual full rich. I readjusted the cable and the arm to give more throw (arm goes somewhat beyond the 45 deg called for in the manual). I saw measurable improvement in the evenness of the mixture and the engine operation during flight, and I START UP and TAKE OFF with the mixture pulled about 1/2" out. I have seemingly infinite mixture adjustments now, whether the OAT is cold or hot.

5. I've always had the big K&N (re-useable) air filter, and don't know how an AeroVee can breath with anything smaller. I had to build a blister into the bottom of my cowl to clear the filter.

6. Too much oil. I followed the AeroVee installation instructions for filling the oil and marking the dipstick. But when I'm running with my oil AT the "full" line I feel like the engine is bogging down slightly. RPMs can be 50 RPMs lower, and temps will sometimes run a bit warmer. So I routinely run with my oil level slightly below the "full" line.

A few other thoughts:
A. Is your needle installed with the flat side facing up, toward the engine?
B. Is the AeroInjector aligned perfectly parallel with the engine center line?
C. And of course your engine will certainly run hot while breaking in again.
D. Is the mixture arm set screw secure?
E. Are the throttle and mixture cables SECURED so that the cable housings do not move when the mixture or throttle are manipulated? I had a sudden loss of power at altitude one time because I had not secured the bracket I had made, after doing some engine servicing. Bracket seen in the center and lower photos:
http://www.mykitlog.com/users/display_l ... 53&row=120

None of this may be helpful, but it's all I've got.

[radfordc]

I see you have checked intake system multiple times, but that is where it sounds like problem resides.

Most concur with your assessment. Years ago many builders used "turbulators" (for want of a better word) in the intake system to help spin the incoming air.

Here is the Turbulator that Dale is talking about: https://www.amazon.com/V-Twin-Motorcycl ... B009C7UNVS

They also sell other types: http://www.ebay.com/bhp/tornado-intake

They all try to improve atomization of the fuel/air mix by swirling the intake charge. Years ago I built a knock off of these for my Aerovee. I didn't see a huge improvement, but I didn't have near the difference between cylinders to start with.

Cheap enough to try and see if it helps.

[Mrcaseymyers]

How did you fix your issue?

[estegen@outlook.com]

Hi Michael , I am having the same issues with number 1 and 3 CHT at 1400 F where 2 and 4 are about 70F cooler . The two front plugs are grey and the two back ones tan color. CHT on all cylinders are between 380 and 400 on the rear . How did you end up sorting the problem . Thanks Egmont

[Fastcapy]

Hi Michael , I am having the same issues with number 1 and 3 CHT at 1400 F where 2 and 4 are about 70F cooler . The two front plugs are grey and the two back ones tan color. CHT on all cylinders are between 380 and 400 on the rear . How did you end up sorting the problem . Thanks Egmont

I can tell you how I fixed this issue with mine.

I threw out the junk aerovee intake elbows and replaced them with a aftermarket elbow that has a smooth curved flow. Boom, like magic temps evened right out. It took some tinkering and I had to make my own gaskets, but it was worth it in the end. Between that and tossing the Aeroinjector in the trash bin my aerovee runs like a different engine now.

[Stevetin]

Hi Mike, regarding the intake manifold and Aerovee carb, what aftermarket intake manifold/elbow are you using and what carb are you using?
Thanks
Steve

[Fastcapy]

Hi Mike, regarding the intake manifold and Aerovee carb, what aftermarket intake manifold/elbow are you using and what carb are you using?
Thanks
Steve

I will have to try to find which intake I used as it was a few years back and I don't remember the source.

As for the carb I am running a Rotec TBI with much better results than the Aerocarb gave me.

[Stevetin]

Thanks Mike. I've been looking at the Great Plains manifolds, their part number 0251.
Steve