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Help me solve my CHT limited climb performance

Brantel

Brantel

Well Known Member
This thread will serve as a place to help a guy put an end to his CHT limited climb performance.

My RV7 has a Hartzell BA CS prop, Lycoming Narrow Deck O-360 with a carb that was drilled out to a #?? (will have to look at logs) and I see 16.5-17 gph FF on a max power takeoff from 1350ft airport elevation.

I have one mag and one P-Mag and I am running the P-Mag on the base curve with "0" advance shift.

Oil temps run around 175 in the winter and 190-200 in the summer.

My airplane has always been CHT limited in climb performance. On anything but a cool day, my CHT's on #1 & #3 (#3 being the worst) will quickly hit 400° and will go to 425° or more if I let them. (I limit CHT by putting the nose down and building speed. Of course this limits climb performance).

On a hot day here in the Southeast, this issue is exacerbated leaving me with poor climb performance.

During cruise, all CHT's run below 360 on hot days and around 340 on cool days. Oil temps will drop 5-10° from climb temps.

I have looked at my baffles and seals and would say that they are average. I have plugged all the holes that I know of but I know that there obviously is something wrong or I would not be having these issues.

I am going to shift my attention from avionics to getting my engine cooling more efficient.

Next time I have the cowl off I will take some pics and start looking for opportunities.
 
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Lars said:
Mine used to be. Devil is in the details. Start a new thread so as not to derail David's; I can share what I did. RV-7, 180HP parallel valve Superior IO-360, vertical draft, 8.5:1 pistons, boringly stock except for dual LSE Plasma III ignitions. Am now only CHT limited on the hottest Sacramento Valley days, and even then never on first flight of the day.
Click to expand...

Please feel free to share...
 
What you're going to find solving this issue is that a lot of little changes will add up in helping the engine cool.

First off, going 25-square after obstacle clearance is very helpful, along with a 100kt initial cruise climb speed. Its not reasonable to expect an extended Vx climb with the little inlets we have and stay cool.

The next thing to look at is spacing the baffles away on the exhaust valve side.

While you are doing that, dab RTV in every gap or hole you find.
 
Thanks guys...

I know this is a huge subject and many have been there done that and some like Dan have went way beyond the average to document their knowledge and experience on the subject.

From looking in the archives I see it is possible to spend an eternity and lots of effort to squeeze every drop of cooling and speed out of one of these RVs.

I just want a reasonably cool running engine that is not so CHT limited in climb and that is average for top end speed.

Is it possible to earn this without having to buy manometers, make piccolo tubes, install plenums, install stainless exit ramps and cowl exit fairings, layup your own custom inter cylinder baffles, etc. ???
 
CHT limited

I too find my climbs limited by CHT. Have a RV-7A IO-360 CS Hartzell BA. FE is 2600'. Typically on a cool morning in AZ (not winter temps) if I put the spinner on the horizon and aggressively climb on takeoff I can only get to 6000' (425 F on the CHT) before having to push the nose over to a cruise climb at 115-120 kts. If it summer I can only climb to ~4000' before pushing over. The trikes have lots of disturbances in the exit flow path over the tail draggers so it is not surprising that trikes may be limited by CHT.

My oil temps are always on the cooler side so no issue there.

I haven't plugged every little hole or gap in my baffles so I don't know if that will make a significant difference or not.

Cowl flaps would be great if they dropped my CHT's on climb out by 25-50 degrees.
 
One thing that helped me early on is leaving the throttle all in (enrichment circuit) and spooling the prop back to 2450.
 
Details

Brantel said:
Please feel free to share...
Click to expand...

Some more specifics would be very useful in helping diagnose your cooling issues:

1. Describe your typical climb profile. I.E., initial airspeed, extended climb airspeed, throttle settings, RPM, etc.

2. Pictures of your baffles are definitely a must. A couple of overall pics, as well as detailed pics of the seals and the areas around the cylinder heads will be helpful. Finally, show us a couple of pictures of your upper cowl inlet ramp configuration.

Skylor
RV-8
 
The RV series is known for both its high and low speed performance. This wide operating envelope unfortunately does not extend to the cooling system. It is possible to run too cool in cruise and too hot in climb. It would appear that a "perfect" RV cooling system delivers a compromise between climb and cruise. I have this situation on the -8, and I am close to getting there on the Rocket.

With that said, your cruise temps are right where I want to be, but I need to get up to that number. The fact that they are your lower limit means you still have some baffle issues.

It's my opinion that the RV really needs a variable geometry exit to give the optimum performance. Might not be needed for the average sport pilot, but for a cross country pilot who makes hot fuel stops followed by long climbs to altitude and runs LOP - its a different story.

I doubt you want to fool with a cowl flap, but I'd suggest that you take a look at the "bypass ducts" for #1 and #3 that Dan, myself and others have documented on this site; look at the details in your baffles and seal all gaps (they add up), and finally, you might consider using a simple spray bar system for those days it's just too hot to get a decent climb.
 
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Brantel said:
my CHT's on #1 & #3 (#3 being the worst) will quickly hit 400? and will go to 425? or more if I let them.
Click to expand...

How balanced are the CHT's
I am replacing a flow divider today that was keeping one cylinder too lean compared to the others. Are #2 and #4 20 degrees or more better? Have you done the GAMI thing to make sure you have good fuel distribution at high flow levels?

I only found my problem after sorting through several nozzles then finally requesting the shop to test my flow divider at 45 lbs/hr instead of idle flow rates!
 
jdeas said:
How balanced are the CHT's
I am replacing a flow divider today that was keeping one cylinder too lean compared to the others. Are #2 and #4 20 degrees or more better? Have you done the GAMI thing to make sure you have good fuel distribution at high flow levels?

I only found my problem after sorting through several nozzles then finally requesting the shop to test my flow divider at 45 lbs/hr instead of idle flow rates!
Click to expand...

It's a carb so I am pretty much stuck with what I get...
 
krw5927 said:
I haven't heard this term before. What is a spray bar system?
Click to expand...

Ross (or someone else with direct experience may jump in), but in the meantime...

Spray a fog of water in front of a heat exchanger to immediately suck out much of the heat in the air, providing relief to the heat exchanger. Reno racers use it quite a bit to augment cooling demands. Works as long as there is water in the tank.
 
Toobuilder said:
Ross (or someone else with direct experience may jump in), but in the meantime...

Spray a fog of water in front of a heat exchanger to immediately suck out much of the heat in the air, providing relief to the heat exchanger. Reno racers use it quite a bit to augment cooling demands. Works as long as there is water in the tank.
Click to expand...

Makes sense, neat idea. Thanks for helping me learn a new term. Seems a bit complicated, heavy, and corrosion-inducing for the average RV cross-country or weekend fun flyer though.
 
Depends... The Reno Unlimiteds go through a ton of water in a race, but our requirements are a lot more modest.

My lack of direct experience hurts me here, but I'd think an automotive windshield washer tank and pump, some tubing, and a few outdoor mister nozzles from Home Depot would make a dent in the CHT issue.
 
A few little changes often add up. Like checking the cylinder fins and filing off any excess casting between the fins.
Allowing for a gap behind the cylinder head on #3 and possibly in front of #2.
Ensuring a good seal around the bottom of the inlets and the front of the crankcase.
Sealing up all the gaps.
Check the front top ramps on the top cowl and make sure air can't escape out from behind the ramp. Ie is the ramp full contained within the baffles or does it pass through the baffle sides.
Also I've found that putting a light behind the engine and then looking through the front inlets will often show where the baffle doesn't seal. I needed to make the rear baffle rubber in a few sections to make it seal well. Also looking at the inside of the top cowl you can often see where it's rubbing and where it's not touching.

Cheers

Peter
 
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Toobuilder said:
I doubt you want to fool with a cowl flap, but I'd suggest that you take a look at the "bypass ducts" for #1 and #3 that Dan, myself and others have documented on this site; look at the details in your baffles and seal all gaps (they add up), and finally, you might consider using a simple spray bar system for those days it's just too hot to get a decent climb.
Click to expand...

Just out of curiosity, what the heck is a spray bar and how does it work?

Like so many others, I would really like to improve my CHT in climbs. I have never had an oil temp issue, I even have oil cooler shutter that I use to bring the temp to the desire 180-185 but my CHTs will hit the 400 after 3000-4000 steady climb (depending on the OAT) , no problem at all in cruise.

I have checked and double checked my baffles and I believe they are very tight, just not sure how to improve it without opening up the exit hole.
 
Allowing for a gap behind #3 and possibly in front of #2...
Click to expand...

This comes up a lot so I'm not calling you out, but this is a bad way to go if you simply use the "washer under the baffle trick". By opening the gap you are feeding the several rows of fins that need it (good), but are also allowing a huge escape path to an area that has no fins at all (bad).

A dedicated duct to those several fins and total blockage to the adjacent "no fin" area of the head duplicates the flow path of paired cylinders and is a much better way to go.

Dan has a great graphic in this post.
 
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Micheal

I agree the washer method is not the best, Dan's solution is much better, that's why I didn't mention a washer.

Cheers

Peter
 
Toobuilder said:
... snipped... but I'd suggest that you take a look at the "bypass ducts" for #1 and #3 that Dan, myself and others have documented on this site; look at the details in your baffles and seal all gaps...
Click to expand...

You mean #2 & #3, right?

I incorporated Dan's approach (peened a blister using a form into the baffle on the aft side of #3) when I first built the baffles. Failed to recognize that #2 needed that as well. Later pulled that baffle and created an opening there as well. That knocked a good 10 degrees F out of that cylinder during climb...
 
Brantel said:
Please feel free to share...
Click to expand...

The devil is truly in the details here.

As mentioned in my last post, I incorporated Dan Horton's "blister" into the #3 baffle, from the git-go. Later added it to #2. Different approach there; due to the piece of angle running across the front of the cylinder, a blister didn't seem practical so I cut a section out of the angle and reinforced it on the front side to create an opening. Actually I don't remember exactly how I did it and I don't have a pic handy, but if that's interesting I can snap a couple next time I'm communing with my machine :D

I thought I had done a pretty good job sealing my baffles to the engine, and used to congratulate myself for same. But still ran hot. Then one evening when I was at the hangar and happened to have the cowl off, I grabbed a flashlight on a whim and turned off the lights. Shined the light from underneath/back/etc, looking for leakage. Ugh. Instant ego deflation. Little stuff, like sealing the edges of the baffles where they wrap around the bottom of the cylinders so air can't depart sideways. A hard-to-reach spot at the aft base of #4 (which has always been my hot cylinder). All around the oil cooler.

Shine a light up through the fins near the plugs. Some cylinders have a lot of casting flash in what should be open finning, blocking flow. It will be readily apparent. None of mine were particularly bad but #4 was the worst. I used jeweler's files to clean some of it out. That was good for a 5 degree reduction in cruise flight.

Have a look at the underside of the upper cowl. You've flown long enough now that the baffle seals should have left witness marks. It will be obvious if you have gap-osis. Modify/realign/replace seals to kill the leaks. A hangar neighbor of mine (who built a beautiful one-off glass cowl for his BD-4) went so far as to mix up epoxy and micro, then applied it to spots on the bottom side where he simply couldn't force the seals to bear against. Laid some thin polyethylene sheet over the micro and reinstalled the cowl. When it was cured he popped off the cowl, pulled away the poly sheet and cleaned things up a bit. Applied a coat of neat epoxy to protect the micro. A few hours of flying later it was obvious that he had a near-perfect seal, from the resulting witness marks.

I would say don't chase more exotic solutions until you have absolutely positively dealt with the easy-to-fix basics.
 
I'm excited to follow this thread too. (Aerosport IO-360B1B with Sensenich fixed pitch)

I'd say I'm in the exact same boat as you Brian. I can easily exceed 400 deg cht's on climb out on just about any day. What I typically do is climb at Vy until they hit 400, reduce power, lower the nose, and all is good. On a hot day I need to be a little more cautious as 400 comes a little quicker. Climbing at Vx to 10,000 ft on a warm day with temps below 400 just isn't going to happen.

I feel I've done about all I can within reason. During the first 100 hours or so I can't tell you how many times I had the cowl off trying all the things I'd read about on VAF hoping something would make a big difference. I even shipped my fuel servo back to Precision so they could verify the fuel flow as I thought it may be lean. I guess I pretty much gave up once I had done everything I'd learned from others. (Except cowl louvers and what Dan H. has done. Most of us are not even in Dan's league and I still wish he was my neighbor!) I did talk to Bart and he said CHT's of 430 or so on climb out can be pretty typical and to remember that most airplanes don't even have CHT sensors.

My thoughts,

Everything is important and a bunch of little improvements can add up to a large one. Do everything you can!
I think the design of the angle valve cylinders offer a lot better cooling than the parallel 180hp so things aren't always apples to apples.
Climbing WOT at Vy with a fixed pitch doesn't yield full fuel flow so I don't know if I even make it to the "fuel enrichment circuit". May not make a difference as it sounds like Brian's still in the same boat even with the constant speed making full power on takeoff.
Even though I've done it, it's hard to get excited about a dab of RTV closing a single 1/8" opening when you got 2" of open heater scat and 4" X 6" oil cooler opening.
I like hearing reports from people like Rosie easily exceeding recommended TBO even with higher CHT's on occasion.

I'm definitely all ears though. It still amazes me that some people can do a less than stellar job on their baffling and not have any cooling issues. Maybe this thread will re-motivate me to get to the next level. :)
 
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Lars said:
The devil is truly in the details here...

...Have a look at the underside of the upper cowl. You've flown long enough now that the baffle seals should have left witness marks. It will be obvious if you have gap-osis. Modify/realign/replace seals to kill the leaks. A hangar neighbor of mine (who built a beautiful one-off glass cowl for his BD-4) went so far as to mix up epoxy and micro, then applied it to spots on the bottom side where he simply couldn't force the seals to bear against...
Click to expand...

Good stuf in this whole post, but the upper baffle seal is area I just went through on the Rocket as it was truly lacking.

I rebuilt the rear baffle structure to be completely straight across so I can use a single piece of baffle rubber from one side to the other. It used to look like the Great Wall of China, with many individual pieces of rubber doing a poor job of sealing. Now it seals with perfection to the upper cowl. One piece, no wrinkles, no gaps.

The sides were also replaced with a single piece of rubber from front to back. With a combination of pushing and pulling on the rubber, I was able to get it to conform to the curve of the cowl and lay down perfectly along most of it's length. I only had to cut to shape at the very front. Though the front does not touch the upper cowl when static, once the upper plenum is pressurized, the seal rolls right into place. This is another advantage of keeping the rubber all in one piece.

The details are important - indeed.
 
One other thing that I tried, with no positive result and lots of disappointment, was that I blocked the 2? inlet air to my heater box. I thought that not robbing this amount of air from the upper cowl and also sending it directly to the lower cowl which one would think it would increase the air pressure in the lower cowl would help. It did not and my temp was pretty much the same.
 
boom3 said:
Even though I've done it, it's hard to get excited about a dab of RTV closing a single 1/8" opening when you got 2" of open heater scat and 4" X 6" oil cooler opening.
I like hearing reports from people like Rosie easily exceeding recommended TBO even with higher CHT's on :)
Click to expand...
I'm right in the same boat with you Jeff. Am still working on getting mine down. Can easily get into the 410s on a warm day with a quick turnaround if I get distracted.

But, in the meantime am comforted by Mahlon Russell (formerly of Mattituck) whose opinion is that TBO and CHT's are not all that closely related. See post #44 in this thread:
http://www.vansairforce.com/community/showthread.php?t=101501&page=5&highlight=CHT

And, from just a few minutes ago, a Titan expert (where, if I heard correctly, Bart Lalonde now works (?)), Post #25:
http://www.vansairforce.com/community/showthread.php?t=114532&page=3
 
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alpinelakespilot2000 said:
But, in the meantime am comforted by mattituck's Mahlon Russell's opinion that TBO and CHT's are not, in his opinion, all that closely related. See post #44 in this thread:
Click to expand...

"Allow me to retort." CHTs are very important for the life of the engine, and I've found this out first hand. Any time you have high cylinder temps (415+) oil will oxidize and start to glaze the cylinder walls. The crosshatch in the hone valleys get filled with this glaze and you no longer can get oil retention, so the rings begin to abrade and wear the cylinders. Oil consumption increases, and oil starts burning on hot surfaces like exhaust valves and seats, which leads to pitting and eventual failure of the exhaust valve. Because the rings are pushing oil into the combustion chamber, rings get carboned up also.

One trip over 450 and the life of the cylinder is greatly reduced.

I have pics of the insides of a cylinder that went over 500 degrees I repaired and can easily show the carnage this one trip over the limit caused.
 
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Brian,
I am very happy with my setup. Since you are just over the mountain from me, I think we should get together, pop the top cowls off and compare.

What's up tomorrow? I think there may be a good weather slot in the predicted wet weekend. (Assuming I can get approval from the social director) :D
 
rocketbob said:
"Allow me to retort." CHTs are very important for the life of the engine, and I've found this out first hand.
Click to expand...
Perhaps I should have paraphrased a bit better, since Mahlon may or may not be here to defend himself. All I meant to imply is that not every expert agrees that above 400F is automatically bad. I don't think anyone is arguing for 450F+, let alone 500F.
 
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May I suggest...

-fuel 1st.
-then timing
-and then baffles

I spent many hours tweaking my baffle w/ little result. I then found that I had an induction leak because my bottom carb half/bowl was loose (slight blue stain around the gasket led me to look closer and I could actually wiggle the bottom of the carb). There's a post you should search about checking how lean your plane is running at altitude. I found this AFTER I tightened the bowl... I'm actually running too rich, which is a lot better than too lean ;-)
 
Brantel said:
Is it possible to earn this without having to buy manometers.....
Click to expand...

Well, a little bit of measurement saves a lot of guessing. It's faster.

Here's what Lycoming has to say about cooling. I've added a few examples:

2ns5eop.jpg


Bobby (ECI) told us it takes about 5 inches of water to cool a Lycoming, and of course he is correct. However, that's pretty much a minimum. The red line offers an example; 75% power, 5" H2O delta across the fins, and 60F OAT at 5000 feet on a warm summer day is going to get you a 435F CHT.

I've added an arbitrary 370F at 75% CHT curve in green, which is probably close to factual. To get 370F (or perhaps 350F at 65%) will take about 8.5" H20 delta on a really warm day, 70F at 5000 feet.

There are some assumptions behind that chart. Think of it as performance with average, old fashioned GA baffle fit. You can do better.

So, in climb, what pressure delta do you have?
 
Toobuilder said:
Ross (or someone else with direct experience may jump in), but in the meantime...

Spray a fog of water in front of a heat exchanger to immediately suck out much of the heat in the air, providing relief to the heat exchanger. Reno racers use it quite a bit to augment cooling demands. Works as long as there is water in the tank.
Click to expand...

NOW I know where to route that pilot relief tube!
 
rocketbob said:
"Allow me to retort." CHTs are very important for the life of the engine, and I've found this out first hand. Any time you have high cylinder temps (415+) oil will oxidize and start to glaze the cylinder walls. The crosshatch in the hone valleys get filled with this glaze and you no longer can get oil retention, so the rings begin to abrade and wear the cylinders. Oil consumption increases, and oil starts burning on hot surfaces like exhaust valves and seats, which leads to pitting and eventual failure of the exhaust valve. Because the rings are pushing oil into the combustion chamber, rings get carboned up also.

One trip over 450 and the life of the cylinder is greatly reduced.

I have pics of the insides of a cylinder that went over 500 degrees I repaired and can easily show the carnage this one trip over the limit caused.
Click to expand...

Since all certified aircraft engines on a 150 endurance test are operated at red line temperatures (500 degrees F for a Lycoming). For a minimum of 35 hours at full power, to prove they can handle the temp stress. None of them should have survived the endurance testing. Because they exceeded your 450 F number. I have personally operated Lycoming type engines at 500 degrees ++ for hundreds of hours in test cell environments for engine certification .I am always amazed at how good they look inside after this kind of sustained high temperatures. I have on one occasion operated a cylinder at 600 degrees. These engines are much more tolerant of temperature than most believe.
 
rzbill said:
Brian,
I am very happy with my setup. Since you are just over the mountain from me, I think we should get together, pop the top cowls off and compare.

What's up tomorrow? I think there may be a good weather slot in the predicted wet weekend. (Assuming I can get approval from the social director) :D
Click to expand...

Sounds good Bill. Come on over!
 
Questioning the concern

I've mentioned this before and have done lots of investigation. I also read Titan Experts post in another thread. I too have always wondered why most everyone on this forum has came up with 400 degrees as the pinnacle as to which we should not exceed. Well, in the Phoenix area, we'd have to be parked for about 6 months of the year.

My plane (now sold) had an ECI IO360 with BPE work over. Nothing special for compression. I conversed with Steve and Richard from ECI. They said that higher temperatures during climb are both normal and expected. In our heat, I tried to limit the climb temps to 425. If they rose higher than that, I backed off the climb. The temps were transient and were never held for very long, 5 minutes or so. In cruise at 10K CHT's were in the 360-370 range.

I agree that we should not have prolonged runs over 425 but transient runs are not going to cause any problems. Temporary higher temps are just a fact of life in the heat of the Summer.

If you aren't going above that, you might be chasing a problem that doesn't exist. Relax and fly:)
 
RV7Guy said:
I've mentioned this before and have done lots of investigation. I also read Titan Experts post in another thread. I too have always wondered why most everyone on this forum has came up with 400 degrees as the pinnacle as to which we should not exceed.
Click to expand...

Mike Busch really stresses the 400 mark in his "all about cylinders" and "leaning" webinars and I'm pretty sure that's where I picked up on it. Being brand new to engine ownership and operation when I completed my airplane, I really only know what I've learned through reading forums and watching webinars. I have a lot of respect for and trust the guys that have been building and working on engines for years. The only problem with that when talking about CHT's is their opinions seem to vary greatly.
 
DanH said:
Well, a little bit of measurement saves a lot of guessing. It's faster.

So, in climb, what pressure delta do you have?
Click to expand...

Dan,

Love the chart and all the info you have provided around this subject. I have parts on the way and will let you know!
 
Titan-Xpert said:
I have personally operated Lycoming type engines at 500 degrees ++ for hundreds of hours in test cell environments for engine certification.
Click to expand...

....and they don't fail, if the operator is smart with the manifold pressure and mixture knobs.

However, you would agree that a major benefit of lower CHT is a significant increase in detonation margin?

Along the same lines, you would agree that lower CHT reduces octane requirement?
 
Yes, wide swings in temperature are "normal" for ram air cooled aircraft engines - but that does not mean that it is the desired state. If there was a way to regulate air cooled aircraft engines to within a few degrees in all operating conditions, you can bet it would be done. After all, this is why many aircraft have cowl flaps and oil shutters and cars have thermostats. Stability is good.

I'm working on my cooling and I believe the ultimate state would be 375 degrees CHT on the ground, climb, cruise and descent. I know that's impossible, but the tighter I can make the temperature swing, the happier I'll be.

The best thing about Experimentals is that we don't have to accept "good enough". Otherwise, we'd all be flying Cherokees.
 
RV7Guy said:
I too have always wondered why most everyone on this forum has came up with 400 degrees as the pinnacle as to which we should not exceed.
Click to expand...

I agree with the other poster that Mike Busch is probably the main source of the 400 degree limit.

In defense of the 400 degree limit, it is a fact that aluminum tensile strength falls off a cliff starting around 350 F. It goes off the bottom of the chart around 600. For the non-technical readers, this weakening occurs with a one time exposure, the strength does not recover upon cooling.

I have extensive industrial experience running aluminum equipment at high temperatures and have seen plenty of aluminum failures due to the thermal induced strength loss. Aluminum remained the best material for the job so the failures were a fact of life and part of the known maintenance and repair programs. The most common failure points were threaded connections (because they were loaded). The threads would just turn to mush and the connection would fail by pulling out of the aluminum. Kinda' like the aluminum head separating from the steel cylinder on our engines.

To RV7Guys point, our engines have been well developed and obviously have iterated to designs that accommodate aluminum at less than peak strength since many engines have operated above 400 F for their whole life. The temperature limits noted by Lycoming would prevent strength loss below a certain value (whether by design or experience) that they feel is acceptable.

I choose to do everything I can to keep them as cool as possible.
 
dpkbys.jpg


This simple cowl mod increased exit area by about 75% resulting in darn good cooling.
I know Dan would not approve, but it works. :)
 
CHT

I reread some of the Mike Busch info last night. One article was mostly quotes from someone else regarding temperatures.
The Lycoming fuel injected, normally aspirated engines typically flow a lot of excess fuel at full throttle full rich.
This is not necessarily true of the Continental Fuel Injection. The Continental injection can be field adjusted. Lets say that the full power fuel flow limits are 29 to 32 gallons per hour. For nearly five years I did battle with my boss and his shop manager about this. At one point my boss told me that "I have been flying these airplanes for 27 years and I know more about them than the Continental Factory or ECI." When he sold the company the shop finally reset the fuel injection to the upper limit and the CHT's dropped about 25 degrees. Prior to this the turbo 520 engines would run CHT red line to the top of climb, every takeoff in the hot weather. The engines with a couple exceptions not related to cylinders, always went to TBO.
The other factor is that these aircraft had CHT on one cylinder only. Also the baffling was not maintained in optimum condition.
I think most engine experts would agree that the Continentals are considerably more fragile than the Lycomings.
On my Pitts, 0 360A4A, I did not have a CHT. I ran it as hard as it would go for 1000 hours, zero problems. Lots of time at 33-3500 r/m.
For the 320 and 360 parallel valve Lycoming says 500 red line, 435 for high performance cruise and 400 for economy cruise.
 
Talked to Alan at Antisplat yesterday. Apparently he is finishing up his latest product: pilot controlled cowl flaps to provide extra cooling air during climb. Likely to be a big seller if install is straightforward as he suggested. Stay tuned.
 
David-aviator said:
This simple cowl mod increased exit area by about 75% resulting in darn good cooling. I know Dan would not approve, but it works. :)
Click to expand...

Looks to me like you needed to make the cut...a huge part of the stock exit area was full of muffler.
 
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