[David-aviator]

Greetings Fellow Aviators,

My re-education with the Lycoming continues.

I took off and climbed at WOT to 8500' today, prop was turning about 2400 rpm at 110 KIAS, the rate of climb was better than 1500 fpm all the way to level off. At 8500' the throttle remained at the stop for about 30 minutes as the purpose of the flight was to seat the rings. Break in instructions say no leaning so fuel consumption was copious.

CHT did not go over 300 in the climb and in level flight dropped back to the 280 range, OAT was 37F. Oil temp topped out at 170F. I'm thinking a CHT of 280 in cruise is a too cool , what are some you seeing in cold weather?

The cowl is "as is" from the Subaru experiment with an exit area of about 125 inches vrs the standard Van's opening of about 56 inches minus the pipe area. There probably is too much air flow through this engine so the exit area will be cut down which also will reduce external drag. At this time I have air coming out of 5 different areas of the cowl.

As near as I can tell, the airplane is running about 10 knots faster than with the Subaru but still some 12 knots less than Van's 180 HP with a CS prop. I am running with the Catto and it maxes out at 2650 at 8500. I'm thinking that may pick up a bit as the engine breaks in. The NG strut was missing for this flight and its probably worth 3 knots. The lumps on the cowl account for the rest of it.

I am getting the feel for this machine as it is quite different than flying with a CS prop. The flaps work again after failing on the last flight and that helps a lot and I also slipped it one time. (The new Motion motor is different in that it has a sealed cover over it and the end of the drive mechanism also is sealed. Hope it lasts forever.) After 3 approaches and landings, I feel like a part of the airplane again.

 

[Ron Lee]

That is perhaps 60 degrees or so cooler than I normally see and I can get to 400 deg F CHT in climb out on a cool day. I don't know if there is a suggested minimum and in general cooler intuitively seems better but as you state it may mean too much cooling and associated drag.

You may be able to raise the oil temp by blocking the oil cooler. Some folks have a hinged plate that covers the aft part, controlled in the cockpit.

 

[pierre smith]

Two days ago......

.....I flew in high 20's F weather and my CHT's were about like yours and I couldn't get the oil over 140 F either. I have a 2" scat hose coming off the left rear baffle to a firewall mounted cooler so I suppose I need to fab a disc-shaped cover for the intake, cockpit controlled, no?

Regards,

 

[David-aviator]

.....I flew in high 20's F weather and my CHT's were about like yours and I couldn't get the oil over 140 F either. I have a 2" scat hose coming off the left rear baffle to a firewall mounted cooler so I suppose I need to fab a disc-shaped cover for the intake, cockpit controlled, no?

Regards,

I have a 4" scat duct to the firewall mounted oil cooler (like the RV10) and Van's sliding shutter device at the exit of the cooler, closing it raised the oil temp about 6F, and I think that number was 170 but I did not write it down. There is some air leaking around the shutter device and that needs to closed off with some high temp permatex.

I've been reading a lot of stuff about the Lycoming and somewhere, someone, said keep the CHT about 300, but I can't find where that came from. Maybe I imaged it. In any event, if the engine had been leaned just a bit yesterday at 8500', it would have increased the temperatures and certainly burned less fuel.

With regard to the air intake device from AFP that permits direct ram air into the FM200, I decided NOT to use internal cowl air through a filter for that part of it (Don at AFP agreed 200%). Instead I built an aluminum FAB device with a Bracket filter that attaches to the left intake baffle as per Van's plan and it is connected to the "Y" device with 3.5" scat duct. At present it has a 3" hole for intake air at the intake baffle into a cavity where the Bracket filter resides at an angle. Take off performance was much better than before when air was sucked out of the internal cowl, but when I opened the ram valve at about 2000', manifold pressure still increased by about 1.5" and rpm increased 100-150 rpm. The engine definitely likes ram air and unless the filter is very large, it does restrict air flow. I really would like to use a large K&N filter I bought but I have not figured out a way to install it. It is large and so is the 3.5" scat tube connecting it to the "Y" device.

 

[DanH]

David,
<<somewhere, someone, said keep the CHT about 300, but I can't find where that came from.>>

Recently had that conversation with a friendly Lyc rep...280F-350F for continuous flight, with temporary hot day climb excursions to 400F.

<<an exit area of about 125 inches vrs the standard Van's opening of about 56 inches >>

I've been playing with some cooling software recently. Assuming 350 CHT, 8500 ft, 180 mph, and a few other sensible assumptions, the code says the excess exit area is costing you 15 lbs of drag more or less.

Very interesting data about the ram air valve and modified alternate air system. Maybe the 3" hole at the baffle entry floor is costing a little MP when on alternate air?

 

[David-aviator]

David,
<<somewhere, someone, said keep the CHT about 300, but I can't find where that came from.>>

Recently had that conversation with a friendly Lyc rep...280F-350F for continuous flight, with temporary hot day climb excursions to 400F.

<<an exit area of about 125 inches vrs the standard Van's opening of about 56 inches >>

I've been playing with some cooling software recently. Assuming 350 CHT, 8500 ft, 180 mph, and a few other sensible assumptions, the code says the excess exit area is costing you 15 lbs of drag more or less.

Very interesting data about the ram air valve and modified alternate air system. Maybe the 3" hole at the baffle entry floor is costing a little MP when on alternate air?

Cooling software, now that's cool. So if I get rid of 40 inches of exit area maybe there will be 15 lbs less drag, I wonder what that equates to knots?

I considered a larger hole in the baffle entry floor but did not have a decent fixture to smoothly steer the air into the filter chamber except a 3" spun aluminum tube flange. I found a source for a 3.5" unit but you have to buy 50 of them. The Bracket filter is 5x6" and standard on the C-172, an inch thick and may well be the inhibiting factor anyhow. It's probably perfect for the 0320.

The filter in the Van's FAB is about 6x7". I tried to fit that unit but it is a major modification with the Superior horizontal intake with the FM200. The intake is forward of where the Precision intake is located, for which the FAB is designed, and there would not have been much FAB intake area where it turns 90 degrees aft. Fortunately I did not have to buy the FAB as a friend loaned me his for a trial fit.

No more flying for now, I don't venture out when its like 14F. I'll leave such sorties for the guys up in Minnesota.

 

[Ron Lee]

Dan, my OLD operator's manual specifies 500 deg F max for 2700 RPM and 450 degrees F for performance cruise (2450 RPM fixed pitch prop). I need to see if it states continuous or short duration but that is not on the chart.

During my engine break-in I kept the CHTs below 400 degrees. It was not until I inadvertently went to around 425 degrees at sea level (out of Key West) that I finally seated my rings well (my guess).

So my question is are the values you quoted cast in stone or good planning numbers after break-in. I used to keep my maximum at 425 degrees or so and have dropped that to closer to 400 just because it is probably better. But I did work to get the temps up closer to 450 for very short periods to aid in break-in after the Key West rise above 400 and ensuing oil consumption drop.

 

[David-aviator]

Dan, my OLD operator's manual specifies 500 deg F max for 2700 RPM and 450 degrees F for performance cruise (2450 RPM fixed pitch prop). I need to see if it states continuous or short duration but that is not on the chart.

During my engine break-in I kept the CHTs below 400 degrees. It was not until I inadvertently went to around 425 degrees at sea level (out of Key West) that I finally seated my rings well (my guess).

So my question is are the values you quoted cast in stone or good planning numbers after break-in. I used to keep my maximum at 425 degrees or so and have dropped that to closer to 400 just because it is probably better. But I did work to get the temps up closer to 450 for very short periods to aid in break-in after the Key West rise above 400 and ensuing oil consumption drop.

Break in instructions from Lycoming state oil consumption will stabilize after the rings are seated. I'm wondering what that means. So far, this engine has used almost zero oil. The dip stick shows just under the 8 quart mark after some 2 hours of hard run plus the run on the Barrett dyno.

The previous 0360 I had in the Cozy would not keep the top quart, it always got rid of it the first hour. This happened so regularly, I began to service it with 7 quarts instead of 8 when changing oil. This engine is different. So far it has used less than a 1/2 pint.

I'm not sure CHT has any bearing on seating the rings. It is my understanding what seats the rings is cylinder head pressure acting down on them causing them to expand against the cylinder. That's what keeps head pressure from blowing by the rings and glazing oil to the cylinder. Once the rings wear the manufacturing imperfections off the cylinder side wall, they are seated.

I had the previous 0360 overhauled at Blue Print near Chicago back in 1998. (I don't know if Blue Print is still in the aircraft engine business, they were big time into auto race engines then and also hold the patent on AvBlend) I witnessed much of the tear down and overhaul at Blue Print and the guys told me the engine will require no break in. They showed me the cylinder imperfections from manufacture and you could feel them with your finger nails. They got rid of this imperfection by honing each cylinder, something Lycoming leaves for the pilot to do with their break in procedure using the rings instead of honing.

At this point I don't know if the present engine rings have seated or not, but I will keep running it hard for another 20 hours or so and monitor oil consumption as per service instructions.

 

[AlexPeterson]

OAT will affect oil consumption

David, just an fyi. In my engine, oil consumption during operations in the summer is around one quart per 8 hours. This has been true and stable for over 1000 hours. However, I am currently at around 14 hours since an oil change, and haven't used maybe 1/2 quart. This has been the case in cold weather flying every winter. If the cht's are in the high 200's to around 330, the oil consumption is noticeably lower.

 

[Kevin Horton]

Cooling software, now that's cool. So if I get rid of 40 inches of exit area maybe there will be 15 lbs less drag, I wonder what that equates to knots?

You said you were about 12 kt slower than Van's figure - I assume you are referring to his 8000 ft 75% number of 200 mph, or 174 kt. 162 kt is 273 ft/s.

Power required is equal to drag times speed - 273 ft/s times 15 lb = about 4100 ft-lb/s. One hp is 550 ft-lb/s, so about 7.5 hp is consumed by 15 lb of drag.

At 75% power, you have about 135 hp produced by the engine. If your prop has a prop efficiency of 80%, the thrust horsepower is about 108 hp. If 7.5 of those hp are being used to push that 15 lb of extra drag, that leaves 100.5 hp to push the rest of the aircraft. If we got rid of 15 lb of drag, the speed would change by a factor of approximately the cube root of (108/100.5) = 1.024. Thus the speed would increase by about 2.4%, or about 4 kt.

 

[David-aviator]

You said you were about 12 kt slower than Van's figure - I assume you are referring to his 8000 ft 75% number of 200 mph, or 174 kt. 162 kt is 273 ft/s.

Power required is equal to drag times speed - 273 ft/s times 15 lb = about 4100 ft-lb/s. One hp is 550 ft-lb/s, so about 7.5 hp is consumed by 15 lb of drag.

At 75% power, you have about 135 hp produced by the engine. If your prop has a prop efficiency of 80%, the thrust horsepower is about 108 hp. If 7.5 of those hp are being used to push that 15 lb of extra drag, that leaves 100.5 hp to push the rest of the aircraft. If we got rid of 15 lb of drag, the speed would change by a factor of approximately the cube root of (108/100.5) = 1.024. Thus the speed would increase by about 2.4%, or about 4 kt.

Thanks, that's a lot of math for 4 knots but I will take it.