General Info wanted about temps

[Darick]

I have about 3.5 hours on my AeroVee and even flying in this cool weather (50degrees) I can't climb at WOT for more than a minute, if that. Right after takeoff (grass field) I need to throttle back to 2700-2800 to keep CHT below 400. Once in level flight I can cruise at 3000-3100 without overheating. EGT is 1100-1200.

I'm not happy with this considering the low ambient temperatures. I would be over temp all the time if this were summer.

I read somewhere that low EGT and high CHT may be from too advanced timing and plan to adjust this before the next flight. As per the manual, my mag check is 40-60 rpm difference, 50 being the max.

Any advice or encouragement would be very helpful as right now I'm wishing I would have chosen another VW conversion.

[gammaxy]

I don't think what you're experiencing is normal. The physics of internal combustion are the same across VW conversions, so I don't think switching engines will be necessary. The encouragement I have to give is that I think you're close and will be able to fix this problem.

I assume you're measuring CHT with the thermocouple screwed into a cooling fin (not at the sparkplug)? Are you sure your engine gauge has the correct thermocouple type selected? I checked my probes using boiling water.

I've never needed to throttle back to keep temperatures <400, but on a hot day I can only climb at 70mph for a couple thousand feet or so before I need to increase the airspeed. I can climb full throttle at around 90 mph indefinitely.

What speed are you climbing out at?

When you say you can cruise at 3100 without overheating, are you having to throttle back, or is that the maximum rpm you can get in level flight?

It does sound like it could be an advanced secondary timing. Your RPM drops don't seem bad--10rpm here or there is pretty hard to measure accurately anyway. If you had performed an in-flight ignition check, that would have been useful information. For now, though, it's probably better to do some sanity checks on the ground first. I'd suggest a full power run-up and see if there's a significant power difference when you switch between the ignitions. I ended up adjusting my secondary by about 2 degrees after some in flight checks.

I'd also check your baffles. A perfect seal is obviously best, but I have noticed mine has an inch or two leak at one of the back corners and probably leaks a bit by the cowl hinge, so from my experience it doesn't need to be absolutely perfect, but I do plan to improve mine.

[mike.smith]

I had the exact same problems in the beginning:

1. Even though your EGTs are not high, I would still try richening the mixture a bit. That was my biggest problem; I waited too long before changing needles (but try richening in 1/8 turn increments, first). I was burning 2.5 to 3 gph, which is WAY too little. You should be burning a good 4.5 gph at a minimum.
2. You can't test your mag difference on the ground; it doesn't work. The difference should be measured in flight. On the ground I have an 80-90 rpm drop. In flight I have essentially 0 (zero).
3. Absolutely adjust your secondary timing! That had a large effect for me.
3. Enlarging your cowl exit may help. It helped me. To avoid cutting up your cowl to test, use a 3" piano hing half on each side of the existing exit opening. 1 side of the hinge pin gets pinned to the cowl with a 3" hinge pin, the other side of the hinge half gets pinned to the fuselage hinge using the long hinge pins you already have. This gives you a triangular slot on each side of the existing cowl opening, adding about 20% to the exit opening.

You are experiencing normal VW/engine issues, not AeroVee issues. Some who don't like the AeroInjector would beg to differ, but once I got my AI set up it's been hands-off for three years. I don't even adjust the needle for winter versus summer. EVERY engine runs hot when it's new. EVERY engine. You're going to run at least 20 hours before you start to see things settle down. This is normal. You just want to get the temps under reasonable control so you can fly those 20 hours.

[wlarson861]

The only thing I would do at this point is adjust the electronic ignition based on an in flight check. You have a brand new engine. Your temps will be high for at least the next 25 hours. Mine didn't settle in till I was somewhere between the 25 hour oil change and the 50 hour oil change. Don't be tempted to modify anything in the installation unless you find a major deviation from the plans. Just fly and get the tests done and by the end of the 40 hour test phase the engine will be broken in, and the temps will have stabilized.

[sonex1374]

Darick,

Don't be discouraged. Your experience is not abnormal for a brand new airplane. My advice is to check your ignition timing in flight prior to making any adjustments. Randomly trying to adjust it can be frustrating. Try taking off next time with the electronic ignition turned off. Start up using both ignitions, like normal, then simply run on the magnatrons. This will eliminate secondary timing as an issue, and poses little risk for one or two takeoffs. The early engine ran like this all the time as that was the only ignition installed! After you determine what you need to do with in-flight testing, then make adjustments.

Other things that you might need to think about. Make sure your mixture is rich enough. Investigate your outlets to ensure they are large enough, and make sure your oil cooler inlet is not too large. Climb out as fast as you can to keep the airflow up thru the cowl. This is especially important during the first 20 hours for break-in. Your goal should be to get the airplane in the air and to cruise altitude safely, then run the engine hard to break it in. Don't worry too much as long as you can build some time with the engine running within limits (as Kerry says, "Green if Green"). Things will get better after a few hours, so get that time built as quickly as you can.

Much of this was discussed on SonexFlight Episode 4. Might be good for another listen to stimulate some ideas.

http://www.sonexflight.com/4

[Darick]

Thanks everyone for your advice and encouragement. Here are answers to your questions...
1. Yes the factory thermocouple is screwed into the fin, not under the spark plug. I did not test for accuracy in boiling water. When the engine is cool, before starting, both thermocouples read the same which indicates accuracy, at least at ambient air temperatures.

2. Climb out about 100 mph. VSI on the MGL F-2 jumps around so much it's impossible to get a reading on climb rate. I have an analog ASI also in addition to the MGL F-2.

3. The following question is paraphrased..."Do you have to throttle back in level flight to keep CHT down?" I haven't tried WOT in level flight yet, so the unqualified answer is no. I have chosen to fly at 3000-3100 rpm minimum in level flight because the manual says minimum is 3000 for break in for an hour and I don't like pushing the limits. CHT is below 400 in level flight and speed is 130 mph. Static RPM is 3200.

I've done some skydiving...is that pushing the limits? Maybe I need therapy?

It's just my nature to be conservative and not "max out" anything in life. I don't even run my lawnmower at full throttle. But I have read on this thread and elsewhere not to "baby" the engine. I'll try harder.

3. Baffles are making a black wear mark on the cowling so I'm assuming there is contact the whole way around. However, there is that one inch hole on the rear casing directly in line with the starter that I didn't plug up with something. That should be plugged.

4. I'm using the 2-1/2 needle and my Red Cube flow meter is reading 5.5 gph at 3000 rpm, full rich. I lean to about 4.5.

After reading everyone's response, my conclusion is to plug the one inch hole, take off on the next flight on primary ignition only, then do a mag check while in level flight at 3000-3100 rpm.

Thanks again. The support from this group is a huge benefit.

[sonex1374]

Darick,

Upload a couple pics of your inlets (inside edges to see how turbulent the air is flowing over them), the cowl outlets (looking up into them as installed on the plane, with a ruler along side showing dimensions), and oil cooler inlet with dimensions. Experiment with running on the primary ignition only (to check the timing of the secondary) and report back as well. It will take 2-3 minutes for the effect to become noticeable, and stable. What is your oil temps, both when the CHT's are at max, and in cruise? It's likely your oil temp is around 180, and your inlet is larger than needed. You can experiment with covering portions with tape. The goal is to have the inlet as small as you can while keeping the oil temp acceptable (e.g. 200-210) in a hard climb.

Jeff

[Fastcapy]

My CHTs were always really high no matter what I did to the timing, mixture, changes to baffling and cowl opening, etc. I finally got them under control after I switched to the Rotec TBI and dumped the Aeroconversions intake elbows and went with a smoother intake design.

[mike.smith]

My high temperatures journey:

http://www.mykitlog.com/users/display_l ... 932&row=11

[Darick]

Darick,

Upload a couple pics of your inlets (inside edges to see how turbulent the air is flowing over them), the cowl outlets (looking up into them as installed on the plane, with a ruler along side showing dimensions), and oil cooler inlet with dimensions.

Jeff

Jeff, I didn't get the cowl oil inlet dimensions yet, but from what I recall, I would have made them to the drawing specs. I didn't round off any of the cowl inlet cuts so they are all sharp, not rounded off on the inside with extra fiberglass work.

Here is the hole in the engine case I was referring to..I was mistaken about the location, it is about 4 inches higher than the hole opposite the starter and is 11/16 in diameter.



The outlet is 4 inches x 12 plus another 1 inch diameter access hole for the gas line drain (gascolator substitute).



Here is a pic of the max temperatures. C1 433 is #1 cylinder (left rear), C2 363 is #3 cylinder (right rear). Usually #3 is hottest, right? I question this but don't know how to verify the accuracy. Today I did heat up #1 thermocouple with a hairdryer to make sure they weren't reversed.
Oil temp is low at 145.