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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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 Posted: Mon Apr 27, 2015 9:22 am Post subject: Firefly/447 RPM question |
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I don't seem to be able to copy the page out of the two stroke manual, but MAX EGT is 1200F. Normal EGT is 860F to 1000F. That is on page 10-1.
MAX CHT is 500F. Normal is 374-446F.
Seems to me if you operate the 447 at 1200F and have your warning light set at 1225F, you will be well over the red line before you know it. I cannot remember how far downstream the EGT probe is located, but it is a significant distance from the edge of the exhaust port. Seems to me, as an uneducated hobbyist, the exhaust will be cooler at the probe.
Again, ultralight instruments are far from precision instruments.
I did pretty good with my two stroke engines flying them as they were set up at the factory. The idea is to prop to the engine, not tune the engine to the prop. Most two stroke engine failures are the result of operators chasing their tail, trying to reinvent the wheel.
Here's the URL for the Rotax Two Stroke Manual. I assume it is the current version:
http://www.rotax-aircraft-engines.com/portaldata/5/dokus/d04495.pdf
The above is my opinion only.
john h
mkIII
Titus, Alabama
From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of Stuart Harner
Sent: Monday, April 27, 2015 11:24 AM
To: kolb-list(at)matronics.com
Subject: RE: Re: Firefly/447 RPM question
Absolutely. I am shooting for high 1100’s EGT and mid 300’s for CHT. I think the 2 stroke is a fine line dance between shock cooling and burning up. Carefully monitored and well maintained the little Rotax would seem to be capable of going beyond what the factory says it will, but make any mistakes and you are looking for a place to land!
The Rotax guy from LEAF told us at OSH that 1250° was the absolute top red line limit. Since my manual has no listing for max EGT, I will defer to the factory certified guy. Consequently, I have my EIS limit set to 1225°.
If I could find a viable 4 stroke to put on a Firefly and keep it Part 103, I would buy it in a heartbeat.
Of course, 2 HP from every cubic inch of displacement on .01 GPH is every pilots wet dream, right? Now where did I leave that box of di-lithium crystals and that bottle of anti-matter?
Anyway, I think there may be a future in electric motors for the Firefly. They are getting close to having reliable long lasing batteries. The motors and controllers already exist. If you can get a battery that will run a 30 HP motor for an hour with some left in reserve that does not cost $45K and weigh 100#, we will be in business.
Stuart
From: owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com) [mailto:owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com)] On Behalf Of John Hauck
Sent: Monday, April 27, 2015 10:06 AM
To: kolb-list(at)matronics.com (kolb-list(at)matronics.com)
Subject: RE: Re: Firefly/447 RPM question
Aluminum melts at 1221F. Rotax two stroke EGT redline is 1200. That's close to the melting point. Instruments are not precision. A tiny hot spot will melt a speck of the piston ring groove, enough to cause rings to stick and blow by, then seizure.
I am a fan of the four stroke. They aren't as critical to tune as the two stroke. They run well for me right out of the box. Prop loading is not critical.
john h
mkIII
Titus, Alabama
From: owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com) [mailto:owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com)] On Behalf Of Rick Neilsen
Sent: Monday, April 27, 2015 9:50 AM
To: kolb-list(at)matronics.com (kolb-list(at)matronics.com)
Subject: Re: Re: Firefly/447 RPM question
I read an article a few years back from the guy that developed the EGT system. He said that he was against the idea that there be any number markings on the gage. The only information that was important is that the pilot can see quickly that the engine has been leaned too much. The result is a much quicker swing of the EGT than the CHT when leaning in flight. That is also how it is explained during my private pilot training.
So all this talk about adjusting the prop to get a specific EGT number just sounds funny. I fail to understand how a engine is better when the heat of the exhaust is captured more by the engine.
By all means get the prop loading right. Make sure the CHT temps are in line and the spark plugs read correctly (these are the important things). Again the EGT will tell you quickly when you have leaned the mixture too much.
As always worth what you paid of it.
Rick Neilsen
Redrive VW Powered MKIIIC
On Mon, Apr 27, 2015 at 8:53 AM, west1m <west1m(at)hotmail.com (west1m(at)hotmail.com)> wrote:
--> Kolb-List message posted by: "west1m" <west1m(at)hotmail.com (west1m(at)hotmail.com)>
I just started flying my Firefly. It was running very hot 1200+ ish.
66' 30 pitch wooden prop. the prop is a bit under pitched as I can over rev it.
However, I saw a chart in Leading edge catalog that shows a 155 main jet for a 447 with a silencer or a 165 jet with out. I only have a K&N type filter.
I switched to a 162 jet and a moved the needle to the middle rich position and problem solved, low 1000 temps. I will likely put the needle back to the middle lean position.
--------
West1m
Hastings, MN
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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stuart(at)harnerfarm.net
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| Posted: Mon Apr 27, 2015 10:45 am Post subject: Firefly/447 RPM question |
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Ah-Ha! Good find John. Thanks for the link.
My manual is older, and has this info:
[img]cid:image001.png(at)01D080EC.FDCD1EE0[/img]
I will be downloading and using the new version from here on out. EIS limits will be adjusted down to 1200°. It is also interesting to see that it is acceptable to be in the high 800’s in normal operation. My understanding was that it should be at least 1000°.
Strange, I had asked this question at OSH specifically since it was not in my manual. Based on the higher CHT temps, the slightly higher 1250° EGT seemed to be in line that the 447 ran slightly hotter than the 503. HMM, makes me wonder about other things said there……
Most of the time I am seeing 1150 – 1190, but on a couple of occasions I have seen it spike into the 1200+ range, which I quickly got out of by changing throttle settings or adding “choke”.
While I don’t think any damage was done, there certainly is no reason to push destructive temperatures.
The probe bosses were welded in by Rotax. I don’t remember the dimensions off the top of my head, but I did measure to see that they matched the instructions of where to drill if there were no bosses.
If memory serves me the hot spot may well be farther downstream than the port opening itself. From welding class days the hot spot of the flame is not at the tip but at the point of the lighter blue flame in the middle. Since I can’t see inside the exhaust, I can only imagine that this MAY be the case.
I am going to read this updated version to see what other changes there were. That may shed more light on what steps to take next.
The learning curve never ends….
Thanks,
Stuart
From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of John Hauck
Sent: Monday, April 27, 2015 12:22 PM
To: kolb-list(at)matronics.com
Subject: RE: Re: Firefly/447 RPM question
I don't seem to be able to copy the page out of the two stroke manual, but MAX EGT is 1200F. Normal EGT is 860F to 1000F. That is on page 10-1.
MAX CHT is 500F. Normal is 374-446F.
Seems to me if you operate the 447 at 1200F and have your warning light set at 1225F, you will be well over the red line before you know it. I cannot remember how far downstream the EGT probe is located, but it is a significant distance from the edge of the exhaust port. Seems to me, as an uneducated hobbyist, the exhaust will be cooler at the probe.
Again, ultralight instruments are far from precision instruments.
I did pretty good with my two stroke engines flying them as they were set up at the factory. The idea is to prop to the engine, not tune the engine to the prop. Most two stroke engine failures are the result of operators chasing their tail, trying to reinvent the wheel.
Here's the URL for the Rotax Two Stroke Manual. I assume it is the current version:
http://www.rotax-aircraft-engines.com/portaldata/5/dokus/d04495.pdf
The above is my opinion only.
john h
mkIII
Titus, Alabama
From: owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com) [mailto:owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com)] On Behalf Of Stuart Harner
Sent: Monday, April 27, 2015 11:24 AM
To: kolb-list(at)matronics.com (kolb-list(at)matronics.com)
Subject: RE: Re: Firefly/447 RPM question
Absolutely. I am shooting for high 1100’s EGT and mid 300’s for CHT. I think the 2 stroke is a fine line dance between shock cooling and burning up. Carefully monitored and well maintained the little Rotax would seem to be capable of going beyond what the factory says it will, but make any mistakes and you are looking for a place to land!
The Rotax guy from LEAF told us at OSH that 1250° was the absolute top red line limit. Since my manual has no listing for max EGT, I will defer to the factory certified guy. Consequently, I have my EIS limit set to 1225°.
If I could find a viable 4 stroke to put on a Firefly and keep it Part 103, I would buy it in a heartbeat.
Of course, 2 HP from every cubic inch of displacement on .01 GPH is every pilots wet dream, right? Now where did I leave that box of di-lithium crystals and that bottle of anti-matter?
Anyway, I think there may be a future in electric motors for the Firefly. They are getting close to having reliable long lasing batteries. The motors and controllers already exist. If you can get a battery that will run a 30 HP motor for an hour with some left in reserve that does not cost $45K and weigh 100#, we will be in business.
Stuart
From: owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com) [mailto:owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com)] On Behalf Of John Hauck
Sent: Monday, April 27, 2015 10:06 AM
To: kolb-list(at)matronics.com (kolb-list(at)matronics.com)
Subject: RE: Re: Firefly/447 RPM question
Aluminum melts at 1221F. Rotax two stroke EGT redline is 1200. That's close to the melting point. Instruments are not precision. A tiny hot spot will melt a speck of the piston ring groove, enough to cause rings to stick and blow by, then seizure.
I am a fan of the four stroke. They aren't as critical to tune as the two stroke. They run well for me right out of the box. Prop loading is not critical.
john h
mkIII
Titus, Alabama
From: owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com) [mailto:owner-kolb-list-server(at)matronics.com (owner-kolb-list-server(at)matronics.com)] On Behalf Of Rick Neilsen
Sent: Monday, April 27, 2015 9:50 AM
To: kolb-list(at)matronics.com (kolb-list(at)matronics.com)
Subject: Re: Re: Firefly/447 RPM question
I read an article a few years back from the guy that developed the EGT system. He said that he was against the idea that there be any number markings on the gage. The only information that was important is that the pilot can see quickly that the engine has been leaned too much. The result is a much quicker swing of the EGT than the CHT when leaning in flight. That is also how it is explained during my private pilot training.
So all this talk about adjusting the prop to get a specific EGT number just sounds funny. I fail to understand how a engine is better when the heat of the exhaust is captured more by the engine.
By all means get the prop loading right. Make sure the CHT temps are in line and the spark plugs read correctly (these are the important things). Again the EGT will tell you quickly when you have leaned the mixture too much.
As always worth what you paid of it.
Rick Neilsen
Redrive VW Powered MKIIIC
On Mon, Apr 27, 2015 at 8:53 AM, west1m <west1m(at)hotmail.com (west1m(at)hotmail.com)> wrote:
--> Kolb-List message posted by: "west1m" <west1m(at)hotmail.com (west1m(at)hotmail.com)>
I just started flying my Firefly. It was running very hot 1200+ ish.
66' 30 pitch wooden prop. the prop is a bit under pitched as I can over rev it.
However, I saw a chart in Leading edge catalog that shows a 155 main jet for a 447 with a silencer or a 165 jet with out. I only have a K&N type filter.
I switched to a 162 jet and a moved the needle to the middle rich position and problem solved, low 1000 temps. I will likely put the needle back to the middle lean position.
--------
West1m
Hastings, MN
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=441368#441368
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zeprep251(at)aol.com
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| Posted: Mon Apr 27, 2015 11:42 am Post subject: Firefly/447 RPM question |
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Rick,
I agree with you on 4 stroke engines.But I always considered cht , on a 2 stroke to be a indication more of load than mixture.If i was under propped it was like running in second gear, lots of revs but not much load.no load makes the 2 stroke lean out which ups the egt but keeps the head cooler.In my opinion,you need to prop the engine for the operating rpm then adjust the mixture for the amount of load at that rpm.My 503 ,prop set for 6100, on takeoff gave about 1000 degrees at full throttle climb out and less than 1200 at 5500 cruise.But the firestar was so clean the throttle was around half open at that rpm.At 5700 the egts got close to 1200 and 75 mph cruise but the head temps were always well under the limits
G.Aman 750 hrs on the Firestar 503 dcdi oil injected
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Richard Pike
Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee
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| Posted: Mon Apr 27, 2015 6:53 pm Post subject: Re: Firefly/447 RPM question |
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[quote="John Hauck"]<snip>
The idea is to prop to the engine, not tune the engine to the prop. Most two stroke engine failures are the result of operators chasing their tail, trying to reinvent the wheel. <snip>
john h
mkIII
Titus, Alabama
[quote]
This. Jet it the way the book says, and then fiddle with the prop pitch until the numbers are happy. Did a 150 hour carbon cleanout of the 582 top end last week, flew Friday, climbout turning 6300, EGT 1,000. Cruising at 5,300 to 5,600 rpm gave consistent matching EGT's of 1050 to 1100. No problem with high EGT's on descent because you adjust the throttle a bit and they stay around 1000. Checked the plugs after landing, they are a medium brown.
Hope to fly again tomorrow with a passenger, will give an update and maybe a photo of the plugs. The plugs verify if the temperatures are acceptable, and if the EGT is close to accurate. From then on, the EGT gauge is mostly to warn you anomalies.
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Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. |
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Mon Apr 27, 2015 7:27 pm Post subject: Firefly/447 RPM question |
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Shouldn't the plug check be done at the power setting that you want to
check, e.g., cruise, WOT, etc?
If the plugs are checked after landing and taxi back to the hanger, does
that not give you an indication for low speed, low power settings?
john h
mkIII
Titus, Alabama
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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Richard Pike
Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee
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| Posted: Tue Apr 28, 2015 3:33 am Post subject: Re: Firefly/447 RPM question |
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| John Hauck wrote: | Shouldn't the plug check be done at the power setting that you want to
check, e.g., cruise, WOT, etc?
If the plugs are checked after landing and taxi back to the hanger, does
that not give you an indication for low speed, low power settings?
john h
mkIII
Titus, Alabama
-- |
I have always heard that, but years ago when I was building dirt bikes - 2 stroke - I would check the plugs after a plain "ride," and then do a run at a specific speed or load to check the jetting, and I couldn't see the difference. Perhaps an expert with a magnifying glass could, but in my laymans experience, the plugs sort of were what they were. For instance, putting in brand new plugs, going out and doing a test, and then pulling them and looking at them, there was not enough accumulation to tell much of anything.
Maybe I was just doing something wrong, or maybe I am missing something. I would be glad to hear from somebody who is actually real good at that particular skill.
Since I run at cruise power & 1,000' AGL 95% of the time, and then just pull it back on final, and then a fast idle downhill to taxi to the hangar, I am thinking that I am not going to alter the appearance of the plugs all that much from their normal state by that last 3 minutes of run time. But I could be wrong.
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Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. |
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Tue Apr 28, 2015 4:04 am Post subject: Firefly/447 RPM question |
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That's what I'm thinking. I can't see well enough to tell minute
differences.
john h
mkIII
Titus, Alabama
I have always heard that, but years ago when I was building dirt bikes - 2
stroke - I would check the plugs after a plain "ride," and then do a run at
a specific speed or load to check the jetting, and I couldn't see the
difference. Perhaps an expert with a magnifying glass could, but in my
laymans experience, the plugs sort of were what they were. For instance,
putting in brand new plugs, going out and doing a test, and then pulling
them and looking at them, there was not enough accumulation to tell much of
anything.
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
There are two kinds of people: those who say to God, 'Thy will be done,' and
those to whom God says, 'All right, then, have it your way.'
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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Jim Baker
Joined: 30 Mar 2006
Posts: 181
Location: Sayre, PA
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| Posted: Tue Apr 28, 2015 5:01 am Post subject: Firefly/447 RPM question |
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Reading plugs is highly subjective. Proper way is to pick your operating RPM to be evaluated, run at that speed for at least 5 min then cut the ignition. Problematic with acft since you'd be landing power off, not hard but not ideal, either. Then you have to evaluate the color of the ceramic deep in the insulator well.....good luck with that.
EGT is much safer and way more revealing. I haven't run into a perfectly jetted, carbureted two stroke....ever. There is always a lean spot in the fuel curve somewhere. I fly a two stroke by the EGT.....that is to say, the EGT will vary day-to-day so if I've chosen to fly at 1175 F then whatever RPM that happens to be, that's what I fly. You can get a fair amount of RPM spread sometimes.
The other benefit is knowing what each cylinder is doing...a slightly plugged jet on one carb in a dual carb setup shows up right now.
Jim Baker
405 426 5377
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Richard Pike
Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee
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| Posted: Tue Apr 28, 2015 4:55 pm Post subject: Re: Firefly/447 RPM question |
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OK, had a good flying day today. Temp when we started flying was low 60's. MKIII Classic, 582, 2 people, 1(at)200 lbs, 1(at)185. Full throttle climbout, 6300 rpm, 50 mph, EGT 1000. Water temp constant at 140 in all situations.
Cruise 1075-1100 EGT, stayed very constant, no appreciable variability. RPM varies 5500-5900. (Lots of lift & sink across the low hills) Airspeed averaged 65.
Temp later in the day 70, no change in any of the above numbers, airspeed on final approach at a couple different strips was 60, EGT 1000 (at) 3000-3800 rpm. I fly cruise airspeed until time to throttle back, dump the flaps, and reset the trim.
Final numbers, 1.5 hours total, 7 gallons used. Last landing of the day before I took the pictures had time on final of probably less than a minute at 3-4k rpm, burst of power on short final. Landing, turning around and taxiing to the hangar took probably around a minute and a half, was at a low rpm, EGT was at 900. Pulled the plugs and took several pictures, this one is the most accurate in terms of how they actually looked. Interestingly, the plugs at the PTO end were lighter and more reddish, the ones at the mag end were a bit darker and more grey.
Numbering from left to right, #1 is closest to the mag. #2 is also mag end cylinder, but closer to the PTO end, #3 is the PTO side cylinder, mag end, and #4 is PTO side cylinder, PTO end. Have no idea why the difference.
Not sure that this establishes any sort of jetting/load/EGT/spark plug doctrine or proves anything, I just found this whole topic interesting and wanted to pursue it. Maybe it will be food for thought, and as Beauford says: worth what ya paid for it.
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Kingsport, TN 3TN0
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stuart(at)harnerfarm.net
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| Posted: Tue Apr 28, 2015 6:28 pm Post subject: Firefly/447 RPM question |
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Well today the wind was light and variable and it was 60 by noon. Headed to
the airport.
By the time I got launched into the air, it was nearly 2PM. Rough and bumpy!
Just enough thermal action to make it not pleasant. Went up to 1500' AGL
and it only got worse. Dropped back to 800' and it was a little better.
Did some playing around at different RPM's and airspeeds. 5500 was yielding
about 60 to 65 indicated. Nosing over and unloading the engine would spike
the EGT. I have reset the alarm to 1190 Saw it jump to 1220 once. Quick
application of throttle or enricher takes care of it. Flew for about 30
minutes between 5 and 6K. Not much fun so headed back. EGT spike again,
added full enrich to keep it cool. Kept some power on all the way to the
ground and made a nice landing. Back to idle, tail down, engine quit!
WTH???
Turns out I just forgot to take off the enrich and I flooded it. Got it
going again and taxied back to the hangar. Decided to add 1/2 of pitch to
the prop. Messed around with that for a while, had a soft drink, visited
around some. Then could not stand it any longer, had to go back up.
Was able to get 6300+ on takeoff and it still climbs like a scalded cat. Air
was a little smoother, so decided to go for a ride. Flew up to my house ~20
miles away. At 5500 I was getting a consistent 65 MPH indicated, 600o would
get me to 70. In the thermals if I nosed over to keep from climbing, I could
easily see 70-75 MPH. Air was still rough enough it was hard to maintain
speed AND altitude. So I would work on one, then the other. Even at 5000 RPM
I was still seeing 60 MPH or more and the EGT was running in the mid to
upper 1100 range but no alarms going off.
Back to the airport, if I pulled power into the high 4000 range and nosed
over, I would get an alarm. Just as I was struggling to get down for a
landing, I noticed that the wind had shifted and was now on my tail. Go
around time! Circled and got lined up for the opposite end and still had
some trouble getting down, even with some fairly aggressive slips. Backed
down to the3500 range and nosed over, then the ground came up fast.
Airspeed was at 50 so all was well, added some power and rounded out for a
fairly decent landing.
So all in all, the mid-range lean problem is much smaller than it was and
even though I moved the prop a little towards a cruise setting it did not
affect the climb at all. I want to get up in some really smooth air to do
more testing before making any more changes. 1.8 hours on the tach and a
good day!
Thanks for all the advice and input. This is going to be FUN!
Stuart
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Jim Baker
Joined: 30 Mar 2006
Posts: 181
Location: Sayre, PA
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| Posted: Wed Apr 29, 2015 2:30 am Post subject: Firefly/447 RPM question |
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This a single point egt setup?
Jim Baker
405 426 5377
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stuart(at)harnerfarm.net
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| Posted: Wed Apr 29, 2015 4:47 am Post subject: Firefly/447 RPM question |
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There are probes for both cylinders (and heads). The page I was using on the EIS shows Altitude and Rate of Climb so it only shows the hottest cylinder.
Adding the small amount of pitch did increase the head temps by a few degrees, but they are staying below 400.
This is a single carb setup and the rear cylinder runs a few degrees warmer than the front.
Stuart
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Wed Apr 29, 2015 5:39 am Post subject: Firefly/447 RPM question |
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I believe it is normal for the PTO cylinder to run warmer than the Mag cylinder based on the cooling system configuration.
Over the years I discovered Rotax two stroke engines were tuned at the factory for 0 to 1500 feet ASL on a 70F day. To keep temps in the green, all that is necessary is prop the engine/aircraft correctly. I also discovered if I propped the engine/aircraft to just bump the red line, 6500 rpm, wide open throttle, straight and level flight, all parameters were happy and I got the best performance, climb and cruise, with a fixed pitch/ground adjustable prop.
john h
mkIII
Titus, Alabama
This is a single carb setup and the rear cylinder runs a few degrees warmer than the front.
Stuart
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John Hauck
MKIII/912ULS
hauck's holler
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stuart(at)harnerfarm.net
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| Posted: Wed Apr 29, 2015 8:18 am Post subject: Firefly/447 RPM question |
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Airport elevation is 1940' so that would make me think that the factory setup would run rich but that is not what I am seeing. I have checked the carb and all the parts are original sizes.
Total time on the engine is only 20 hours, so I am inclined to leave things about where they are until I get another 20 or so on it. If I do anything, it would be to add another little bit of pitch.
In ND we are the state of wild temperature changes so there is likely to be at least some variation from day to day.
Stuart
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Wed Apr 29, 2015 2:22 pm Post subject: Firefly/447 RPM question |
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Air cooled.
jrh
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MKIII/912ULS
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