Lowering CHT's, RV-6 IO360 180HP, AFP - Page 2

JonJay · #11 05-22-2007, 07:52 AM

Quote:

Originally Posted by AlexPeterson

I see no mention of mixture in this thread. I (and many others who have written extensively in this forum) have found that mixture has a huge effect on cht's. The effect is so large that I don't know how one can really tell the effect of other changes, unless the testing is done at the exact same mixture relative to peak egt's each time, and with the same power settings and OAT.

How balanced are the injectors? Do you have one/two EI systems? If you have balanced injectors and EI, you can really cool that thing down by running LOP.

Running 50 to 100 ROP vs 50 LOP will increase cht's by at around 50F degrees. Dan C. will probably "check" in here...

Absolutely - Each flight was conducted as close to the same parameters as I could set up, not being a test pilot or lab tech. Lots of variables. However, my EDM 930 and trending software allow me to compare after the flight. Climb out is especially hard to quantify as holding exactly the same airspeed each time and the same climb profile, etc... while not difficult is not exact either. I am getting pretty familiar with my airplane with 20 hours, forty plus flights, that my intuition in knowing where things where, and where they are now, is pretty good. However, the EDM 930 allowed me to compare hard data; OAT, power settings, etc. I did all of my test flights running 50deg LOP. My spread is between .3-.5 gph. I have not made the decision to balance my injectors just yet but have some suggestions from AFP. JPI's EZ Trends program captures data every 6 seconds. I am sure it is not perfect either but for what I was doing, measuring relative CHT's, I think it worked well. I also have 40 or so flights of data to compare. So, my fixes might have improved even greater than 40deg. as I was being conservative reporting back to this group. I am confident in the numbers as relative CHT's and have no doubt they improved greatly, so I hope people find this thread usefull, as those previoulsy posted did for me. I have two standard mags by the way.
Another factor on CHT's also reported on several previous threads is mixture when fully rich at full throttle. My fuel flow seems to be correct at 17 gal/hr.
I did run part of my flight ROP for comparison to LOP. I would say that 50deg is conservative and LOP may even be cooler than that.
Good stuff.
I can not imagine not having an engine monitor. However, my Bucker has one EGT and one CHT on one Cylinder, nothing else, and its 0320 is pushing 2300 hours with no cylinder or head work, ever.....pretty amazing.

billnaz · #12 05-25-2007, 12:35 PM

My local AP recommended adding a small ramp to the bottom of the cowl at the exit to create an area of neg pressure to encourage exit air flow. My 0360 heats up way too fast on TO, limiting my initial climb, though cruise temps are fine. I'm thinking that angle of attack is the culpret and hoping this will be a fix. If this doesn't do anything, I'll look into the Avery leuvers or maybe cowl flaps.
Another point my AP made is that a new engine will take up to 100 hrs to fully break in and stablize in regards to temps.(I'm at 33 hrs now) It's all so cornfusing!

49clipper · #13 06-08-2008, 10:16 AM

I have tried most everything mentioned here to no avail. I did the "Braly" mod to mine last week and it was worse. That is the mod where you put an 1/8" piece of baffle material between #4 & #3 and the rear baffle. Made it 30 degrees hotter on takeoff. Pulled that out and tried an aluminum angle on the bottom of the outlet tunnel and that seemed to help slightly. So, then I cut an 2" x 8" section of the bottom only at the rear of the tunnel. That also made it much worse. I had 450 degrees by pattern altitude. So, now what. My baffling is as good as I have ever seen short of having a plenum. I recently got underneath and put more rtv in the 1/16" inch gaps at the intercylinder baffles with no help. I am running out of ideas. In lever flight after they have cooled down they run at about 330-350 at 75% pwr (90oat)and about any altitude. Any ideas?

49clipper · #14 06-08-2008, 10:17 AM

I forgot to mention I have an O-320-D1A with the sensenich fixed pitch prop.
49clipper

frazitl · #15 06-08-2008, 10:34 AM

Just an idea. Have you checked your engine timing? A little advanced can increase temps...

49clipper · #16 06-08-2008, 10:44 AM

Terry, good idea, but I did check that at 5.0 hrs and I don't think it would have changed much since I now have 13.5 on it.

How much of the lower tunnel can be removed with going in the wrong direction? I also think I will at a another temporary cooling lip to see how cool I can get. I am not worried about a couple of miles per hour if it cools properly.
I do not want to cruise at 400f. All the folks I talk to, including lyc agree that you should not have continuous operations above 400f. Lycoming states 435 tops for cruise and 450f max, but I think that would get you new cylinders way before normal.

Jim CFI/AP/IA

Kyle Boatright · #17 06-08-2008, 10:55 AM

Quote:

Originally Posted by 49clipper

I have tried most everything mentioned here to no avail. I did the "Braly" mod to mine last week and it was worse. That is the mod where you put an 1/8" piece of baffle material between #4 & #3 and the rear baffle. Made it 30 degrees hotter on takeoff. Pulled that out and tried an aluminum angle on the bottom of the outlet tunnel and that seemed to help slightly. So, then I cut an 2" x 8" section of the bottom only at the rear of the tunnel. That also made it much worse. I had 450 degrees by pattern altitude. So, now what. My baffling is as good as I have ever seen short of having a plenum. I recently got underneath and put more rtv in the 1/16" inch gaps at the intercylinder baffles with no help. I am running out of ideas. In lever flight after they have cooled down they run at about 330-350 at 75% pwr (90oat)and about any altitude. Any ideas?

Maybe I don't understand the "braly" mod, but to my way of visualizing what you described, it sounds like it may have created a gasket which effectively sealed the gaps between the contact point on the cylinders and the baffles, more or less eliminating airflow there. That doesn't make sense to me.

Instead of doing that, on #3, back out the screw that holds the baffles to the aft side of the cylinder then replace the screw with an AN-3 washer between the cylinder and the baffles. You're trying to increase airflow across the back of that cylinder.

I don't know what to suggest on #4, it usually isn't a problem.

Have you installed a cylinder blocker in front of #1?

One more question: What speed are you using on climb-out? I normally use 110-120 knots.

49clipper · #18 06-08-2008, 08:06 PM

Kyle,,
The 'braly' mod is essentially the same as what has been described on this site as the washers between the fins and the baffle on the aft side of #4. It was initially the idea of George Braly of GAMI injector fame. It is a small 1/4" x 1/4' inch piece of the red silicone baffle material inserted between the fins and the baffle to increase airflow thru that area. It has worked on every engine I have used it on except this one. It was worse. The cylinders went to 450 by pattern altitude. So, I took that back out.
Jim

49clipper · #19 06-09-2008, 04:54 PM

Well, thanks to some of hints here on the list, my problem is solved. I installed the 1.25" dam in front of #1 and that did most of the trick. I actually started out with 1.5" and worked my way down. Then checked the mixture control again and found it had slipped on the cable and was 1/8" away from full rich. In addition, I put a blank off plate over my 3" hose to the oil cooler and drilled it for 1.5" which works very well and kept the oil at 185f in 85oat conditions at full power. So, now its very cool as it should be. On takeoff, I kept in full power to2700' and never got over 392 on #1 which is now the hottest slightly. Fantastic! I now can lean at altitude like normal. In cruise at 6500'/26C OAT/2500rpm/324 to 331 on cyl temps.
Jim