BigTex Posted May 13, 2013 Report Share Posted May 13, 2013 Climbing at 120 mph is a good call, but forget 25 squared. Yes, I know, the POH recommends it, but keep full power throughout the climb. Dan - Your F model has a different engine than what's in his C so we're really talking apple to oranges. Your advice going WOT and 2700 RPM will absolute cook the engine in C Models. I've seen performance charts comparing all of the vintage aircraft showing oil temp and CHT and the C consistantly runs as much as 30 degrees hotter than the E and F. You might be able to bring the RPM's back up once temps come down once in cruise climb but on takeoff you have to really watch CHT's and aggressively mange it. Quote Link to comment Share on other sites More sharing options...
jetdriven Posted May 13, 2013 Report Share Posted May 13, 2013 How does the extra fuel from the economizer circuit cook the engine? This engine is a parallel valve lycoming they put on Cherokee 180s, 172s, RVs, all kinds. Many have fixed pitch props but you don't see advice to climb at reduced power in those airplanes. I think the 25 square climb is causing a problem where there isn't one. Quote Link to comment Share on other sites More sharing options...
BigTex Posted May 13, 2013 Report Share Posted May 13, 2013 How does the extra fuel from the economizer circuit cook the engine? This engine is a parallel valve lycoming they put on Cherokee 180s, 172s, RVs, all kinds. Many have fixed pitch props but you don't see advice to climb at reduced power in those airplanes. I think the 25 square climb is causing a problem where there isn't one. Every aircraft is differenct and just because it's not an issue with the aircraft you listed doesn't mean the C shouldn't either. In fact, your J has a different engine, cowling and baffling system so cooling will be different. I know for a fact in my aircraft that if I don't pull RPM's back after takeoff my CHT's will rocket to 430+ degrees within the first couple of minutes. I'd love to push everything forward on takeoff and climb like a bat out of hell until I reach cruise altitude but for at least my C, that advice doesn't work. I'd like to challenge anyone on this forum that is flying a C-model with a stock cowling/baffling system to post their engine data that shows their CHT's staying under 400 degrees when climbing out WOT/2700 RPM. If there's one, it's one special C. Quote Link to comment Share on other sites More sharing options...
jetdriven Posted May 13, 2013 Report Share Posted May 13, 2013 Its a design feature in the Marvel MA-4 and MA-5 carburetors to get extra fuel at WOT. It opens the economizer circuit which gives you an extra 10% of fuel you can only get one way, with the throttle full open. Pulling it back defeats this feature. Check this out, next time you go fly, watch your takeoff EGT and note what the number is, then pull the throttle back to 25" and note the EGT. Report back. It also takes airspeed to cool in the climb, and in the M20J, M20G, and M20E I have flown, it better be at least 120 MPH. Reducing power for climb takes that option away. You can;t climb at Vy in any of those other airplanes either without getting the engine warm. Quote Link to comment Share on other sites More sharing options...
jimosborn Posted May 13, 2013 Report Share Posted May 13, 2013 Here's a Strength of Materials chart originally published by Pratt & Whitney in "The Aircraft Engine", included in (and lifted from) John Deakin's "Pelican's Perch #18" on AvWeb. http://www.avweb.com/news/pelican/182084-1.htm Puts into perspective why it is so important to maintain CHTs below 400dF for long cylinder life. CHEERS! Quote Link to comment Share on other sites More sharing options...
AmigOne Posted May 13, 2013 Report Share Posted May 13, 2013 It may be that I am defeating the design feature of the carburetor by pulling back and I do see EGT in Cyl #4 increasing but the fact remains that when I go 25 square the increase on CHT is arrested. I do not see how I can be "cooking the engine" when I'm able to reduce CHT. Once again quoting M. Busch, "worry more about CHT than EGT " Quote Link to comment Share on other sites More sharing options...
Bryanmooney Posted May 14, 2013 Author Report Share Posted May 14, 2013 Good news guys, It seems most of the issue was I was simply climbing out too agressively. Today I initially started at 80 but only momentarily, then to 100 till about 600 feet, then on to 110-120 for the rest of the climb. The engine stayed about max 400ish degrees. Only once while taking off with some terrian @TN44 did I get it to go to 500 degrees. it never went past 500 and I was able to cool it down. This I chalked up to my agressive climb. I simply cant climb nose high like I am used to in C 172s. During all climbs I kept it WOT for max fuel. Thanks for all the advice. I will let you know if they find anything in annual. Quote Link to comment Share on other sites More sharing options...
carusoam Posted May 14, 2013 Report Share Posted May 14, 2013 We're you able to see the relationship of FF, and CHTs at WOT vs @ 25”/2500rpm? My C's instrumentation was comfortably lacking real data... No FF or JPI. The single EGT had no numbers on the scale. Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Bryanmooney Posted May 14, 2013 Author Report Share Posted May 14, 2013 I am still doing transition training so my instructor has me thinking about a lot of different things. When I get some of my own time I will document exactly comparable times and post back. I am VERY thankful I got a JPI because I would have never known how much stress I was putting on the cylinders. Quote Link to comment Share on other sites More sharing options...
BigTex Posted May 14, 2013 Report Share Posted May 14, 2013 Bryan - When you get some time, can you dump the data from your last couple of flights and post the link? You can upload the files to Mike Busch's website for free. Here's the link: https://www.savvyanalysis.com/home Quote Link to comment Share on other sites More sharing options...
testwest Posted June 12, 2013 Report Share Posted June 12, 2013 Gary has some good advice Bryan, if you can dump the data and look at it you can learn a lot. I do have some data from back-to-back WOT climbs I did with KSMooniac about a year ago. Climb speed really makes a difference on the CHTs. For Gary, you may be better off climbing with more power at a faster speed. Your climb rate should not be that different from what you are doing now, hopefully. Quote Link to comment Share on other sites More sharing options...
BigTex Posted June 12, 2013 Report Share Posted June 12, 2013 I actually got my CHT's to drop as much as 25 degrees by adjusting the Cowl Flaps to open beyond the 1.5" spec to about 2" and still close. Quote Link to comment Share on other sites More sharing options...
Alan Fox Posted June 13, 2013 Report Share Posted June 13, 2013 There are two ways to cool an air cooled engine.....Cooling air , Fuel, (rich mixture)... You should be able to move 16 to 18 gph through the engine, 0-360, at takeoff power , If only 12 or 13 there is a fuel issue , also make sure the probes are not GEM probes.....there is a programming solution for the GEM probes , but it doesn't work....The difference between the probe types , wire colors on the sensors ....I think one is red and yellow , and the other is red and white.... As far as fuel , If you have a fuel flow , make sure you don't have a fuel line bent beyond a 4 " radius.....also check the mixture and throttle arms reach their stops.... Quote Link to comment Share on other sites More sharing options...
Lionudakis Posted September 29, 2013 Report Share Posted September 29, 2013 I still struggle to keep the temps out of the 415-425 range on takeoff and extended climbs. Nothing has changed except installing an Insight G3, I've played with cowl flaps, mixture, power settings, airspeeds and checked timing multiple times, new plugs and harness. Its flowing 18.1 at WOT full rich, once airspeed gets up to near cruise temps come down, but even at cruise altitude, if I start a slow climb, the temps follow soon behind, Im lead to believe the doghouse baffle design on the C's just doesn't allow proper airflow. Quote Link to comment Share on other sites More sharing options...
Jamie Posted September 29, 2013 Report Share Posted September 29, 2013 deleted. Quote Link to comment Share on other sites More sharing options...
Shadrach Posted September 29, 2013 Report Share Posted September 29, 2013 18.1GPH at WOT full rich SL should be close. What is the EGT of the offending cylinder? It makes no sense to me that your engine is combatting CHTs above what my F does. You have a lower compression engine which in theory should run cooler, not hotter... Quote Link to comment Share on other sites More sharing options...
jetdriven Posted September 29, 2013 Report Share Posted September 29, 2013 There is some speculation that parallel valve cylinders have less fin area and run hotter that angle-valve cylinders. Van's RV guys area always complaining of high CHT's on those engines. Quote Link to comment Share on other sites More sharing options...
orionflt Posted September 30, 2013 Report Share Posted September 30, 2013 Climbing at 120 mph is a good call, but forget 25 squared. Yes, I know, the POH recommends it, but keep full power throughout the climb. And lean as you climb to maintain best power/ temps Quote Link to comment Share on other sites More sharing options...
cathead Posted September 30, 2013 Report Share Posted September 30, 2013 How do you figure what the fuel flow should be? I have a cherokee with an 0-320, what should my fuel flow be? Quote Link to comment Share on other sites More sharing options...
Shadrach Posted September 30, 2013 Report Share Posted September 30, 2013 MM should tell you. I'd guess between 15 and 16gph. Let us know what you find out! Quote Link to comment Share on other sites More sharing options...
kellym Posted October 2, 2013 Report Share Posted October 2, 2013 When you pull the power back to 25-25 you are doing two things that don't help the high cht situation. Pulling the throttle off the stop leans the engine out. Pulling the prop back increases cylinder pressure. Both together take away a third of your climb rate and about ten knots worth of airspeed. Absolutely right. With the carbureted engine you NEED full throttle until you get airspeed above 120. There is a power enrichment circuit that richens the mixture only in the last 1/2" of throttle travel, and you need all of that enrichment. The only adjustment to make after obstacles are cleared is to reduce RP< 50-100 rpm for noise abatement, but leave throttle alone all the way to cruise altitude. Any temp above 425 the aluminum cylinder head has lost 50% of its tensile strength and you want to be doing something to cool things down. I recommend accelerating above 80 as soon as you have obstacles cleared, gear up and flaps up. 100 mph -105 will be your best rate of climb and much better visibility and cooling. I find I get same rate of climb at 115-120 as I do at 100-105 mph and the cooling is better. Kelly Quote Link to comment Share on other sites More sharing options...
kellym Posted October 2, 2013 Report Share Posted October 2, 2013 There is some speculation that parallel valve cylinders have less fin area and run hotter that angle-valve cylinders. Van's RV guys area always complaining of high CHT's on those engines. Having worked with a few guys on solving their temp problems, usually they have not optimized the engine baffles and cowling exit. The RV's do have fairly tight cowling. Vans does not provide optimized air dams or anything else to equalize airflow between cylinders, nor advise of the need to have at least 1/8" gap between front of #2 and rear of #3 to get air past the intake side of the cyl head that has no fins. In fact the Vans baffle kit only has cut each metal piece to fit against the engine, without any trimming on the top at all. Builder has to work carefully to get the right gap for the flexible seal and install the flexible seal correctly to prevent air leaks. IMHO, being an RV builder myself, Van's plans/instructions for firewall foward are wholly inadequate, as they assume by that stage builder is an expert with sheet metal. They may have the skills, but they don't have the knowledge to do a clean and tightly sealed installation. Kelly EAA Tech Counselor (hat of the moment) Quote Link to comment Share on other sites More sharing options...
Lionudakis Posted October 13, 2013 Report Share Posted October 13, 2013 18.1GPH at WOT full rich SL should be close. What is the EGT of the offending cylinder? It makes no sense to me that your engine is combatting CHTs above what my F does. You have a lower compression engine which in theory should run cooler, not hotter... It's all cylinders, on a recent flight highest temps were #1) 402/1349 #2 401/1250 #3 418/1401 #4 414/1290 with an oat of 95. I'm going to check calibration of G3 engine monitor to make sure I'm not chasing a problem that doesn't exist, I just changed oil/fuel pump and did some detailed sealant work of the baffling, it's not much but looking forward to seeing if any results. I also wonder how much negative effect the oil cooler has venting airflow into the lower half of the cowling and effecting the cooling air differential pressure. If it was a good design why did they change it? My buddies J doesn't have any cht issues.. Quote Link to comment Share on other sites More sharing options...
mcpilot Posted October 13, 2013 Report Share Posted October 13, 2013 Fuel flow is usually the offender in these cases.... Quote Link to comment Share on other sites More sharing options...
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