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Reducing #1 in climb

ExtraKatana

Well Known Member
I've had my 8 now for about 5 months on my (edit) O-360 parallel valve and have always had a 4 cyl CHT/EGT on my RV6 and RV7. I've never experienced such a rapid heat-up on #1 in climb(420F after 1500 ft. Full power TO and 5-7 min. taxi). My oil is still at 70 degrees on TO! #1 Baffle has what looks to be a Std ramp(no Dam) I have checked for air leaks in the baffling. The temp on #1 DOES SETTLE back down with the rest of the cylinders in cruise. It's a Climb/#1 Cylinder "thing"
 
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Is your engine fuel injected? If so, it sounds like it could be a partially clogged injector.
 
Is your engine fuel injected? If so, it sounds like it could be a partially clogged injector.
No, it's carburated. One of the first things I looked for was an intake leak. EGT's are in-line with the rest of the cylinders however. So it doesn't appear to be fuel/intake related and the temp DOES settle back down in cruise.
 
I assume you are fuel injected.

Do a high power GAMI check to see if #1 is lean compared to the others. If so, then increase the nozzle size after you verify the injector clean. The other option if that cylinder is lean is an intake air leak, but as you have the problem at WOT I would assume this unlikely.



Carl
 
rapid heat-up on #1 in climb(420F after 1500 ft. Full power TO and 5-7 min. taxi).

That is significant and not normal. I would check for debris that may be stuck in the head cooling fins, as from birds or bees; Its that time of year. Minor Intake leaks are usually barely noticeable at WOT. A borescope is a good idea if you can't find any other source. Detonation could be the cause and you may find evidence of it or possible significant carbon deposits causing it.

It would be good to observe the CHT rise/ramp. If you are going from Take Off at 275* and see a rise of 150* in 5-10 seconds, moderate detonation is a very real possibility. Not a lot of things can raise CHTs that rapidly, though I suspect that heavy cooling air blockage can come close. Very rapid rise's in CHT are classic detonation. Detonation typically only occurs at high power levels, so the fact that you get this at 100% power and NOT at cruise power further points to detonation. Getting normal CHTs at cruise and very high CHTs at full power also points away from cooling air blockage, assuming the cruise CHTs are in range with what they used to be.

Larry
 
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casting flash?

Could also be casting flash. Look really carefully at the fins on #2 and compare to #1. You'll probably find some flash and/or bugs gunk, etc. in the head fins.
 
Do you have the fiberglass ramps installed behind the air inlets in the upper cowl? Turbulent air flow above #1 during climb?
 
So pulled the Cowl this afternoon and there was some flashing but only between two fins. Drilled it out with a long thin bit. There was also a dam made out of RTV and I cut it out. I know detonation has been mentioned but this cylinder is even higher when taxiing. I have switched probes so it is not instrumentation. Will fly it tomorrow and see if removing the dam helped any.
 
So pulled the Cowl this afternoon and there was some flashing but only between two fins. Drilled it out with a long thin bit. There was also a dam made out of RTV and I cut it out. I know detonation has been mentioned but this cylinder is even higher when taxiing. I have switched probes so it is not instrumentation. Will fly it tomorrow and see if removing the dam helped any.

You stated this in your first post

" The temp on #1 DOES SETTLE back down with the rest of the cylinders in cruise. It's a Climb/#1 Cylinder "thing""

It is hard to imagine cooling air blockage being the primary reason for the rapid spike at TO power if the engine cools normally at 75% power in cruise. Clearly, the higher the power, the greater the heat rise from blockage, but should still see an impact at 75% power.

Best to look at the EFIS logs if you have them to determine how fast the temp rise is after going full throttle on TO.

I had a bird nest in my 6's cowl this winter. Thought I got it all out, but a few pieces remained, stuck in some of the fins. I had moderately elevated temps on one cylinder and they appeared in both high power (i.e. T/O) AND at cruise.

Not making an argument that you have detonation, only that compromised cooling doesn't make complete sense. Are you pulling the bottom cowl? I helped a new owner of a 6A and he got the plane with one of the lower baffling bands cracked and loose. After repairing it, his CHT dropped a lot on that cylinder. His also was in both climb and cruise.

Larry
 
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Solved

So I spent time at the hangar this weekend and pretty sure I solved a problem staring me in the face. A little embarrassed I didn't figure it out earlier but still amazing how much difference it made.

I've had the plane for 3 months and just now getting into some significant ambient temps. I discovered a salf-made dam of RTV in front of cylinder #1. Took about 45 minutes to cut all of it out with an exacto....and also blocked up the heater inlet(behind #3) and removed the muff for the summer.
I flew Saturday and Today and #1 never got above 375. The RTV dam was apparently blocking all of the air to the lower front and bottom of #1. I can only guess why it was there in the first place. It could have been the manual Rocky Mountain antiquated system had the knob always turned to #3CHT and they were trying to lower that temp.....which blocked significant cooling air to #1 and they never figured it out. Stranger things have happened I guess.
 
small things make difference

Working with another guy --- a 1x2 inch bit of aluminum tape dam on the front of #1 (plane doesn't have the Van's deflectors) made about a +10 F difference on #1 (which was too cool) and about -5 F difference on every other cylinder. Small things make a difference.
 
Baffle

A lot of people put the dam that comes in the baffle kit in front of cyl1 and then they get issues with 1 being hot. Unless you live in Alaska or there about, that little critter is unnecessary. I don’t fly my RV when it’s below 35 deg so I don’t need it.
 
...My oil is still at 70 degrees on TO! #1 Baffle has what looks to be a Std ramp(no Dam)

I probably would let your oil warm up a little more before TO. That seems a little low. I generally dont take off until my oil is at 100.
 
I probably would let your oil warm up a little more before TO. That seems a little low. I generally dont take off until my oil is at 100.

I routinely take off with oil temps at 70. I only wait for CHTs to rise above 260 for take off (the best indication that I have that barrel temps have risen enough to match the faster expanding piston). I have done this for 750 hours on the 320 in the 6. Oil pressure is pretty much the same, even at idle, as it was fresh from overhaul (i.e. no meaningful bearing or pump wear) and compression's all above 72 and most 74. I remain convinced that 100* OT is not necessary and is a hold over from the radial days with 50 wt oil. Granted, this is with 20W50 oil and at TO, OP is well below the 95psi max for normal operations. I do believe that oil should be warm enough to keep pressures below the limit. Might act differently if using straight weight oil.

Just another opinion with anecdotal data. I have yet to find mention of the 100* minimum limit in the lycoming manuals. Here is a direct quote from the Lyc operators manual under "warm up:"

"Engine is warm enough for take-off when the throttle can be opened without the engine faltering."

I suspect Lyc would have mentioned a 100* minimum in that section if they thought it was necessary. They do, however, mention a max oil pressure, which has some correlation with OT. However, as long as the OP stays below the max during TO, Lyc infers "good to go."

Larry
 
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A lot of people put the dam that comes in the baffle kit in front of cyl1 and then they get issues with 1 being hot. Unless you live in Alaska or there about, that little critter is unnecessary. I don’t fly my RV when it’s below 35 deg so I don’t need it.

The front dams are not for winter operations....
I admit that there may not be a lot of detail in the baffle kit explaining so, but the dams that are provided are needed on most installations but not necessarily in the dimension the are supplied.

Every engine and actual installation is a bit different so there is no one size fits all, but most people that take the time to do some detailed testing and attempt to balance the CHT's find that they need some amount of dam on the front cyl.

Even then, they will not assure a perfect balance of CHT's in all conditions.

Another variable with this is that it is actually a moving target. Changes in power setting and airspeed will have an influence on the level of cooling attained on each cyl. Especially on carb equipped airplanes.
My RV-6A for example has a CHT spread of only 5-6 degrees between the 4 cyl., but that is only at a very specific speed / power setting that I typically cruise cross country at. Loafing around at a low power setting (5.5-6 gph) there is a 20 degree spread.
 
Air Dam

Thanks to all for the wonderful insights into dam building. :) My question, I have o320 carbureted. I temporarily tried aluminum tape on #1 cylinder,, 3 inches across and 2 inches high. All 4 cylinders a now nearly equal to each other. Do I need to spread the **** across the entire cylinder fin area or can I work with what I have on limited fins. Am I creating a hotspot or do I need to distribute **** evenly?
 
Just a thought... cold day? Engine producing more power? Possible flirting with detonation. I have seen this from foreign matter glowing under load in the cylinder; slightly longer spark plug threads, heli-coil protruding into the cylinder, and "****" (that's a technical term) on the valves. Often, this is caused by more than one circumstance, high power, cold day, and a history of operating in an overly rich environment. On the ground---- lean the P__S out of it!

DAR Gary
 
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