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jrstone(at)insightbb.com
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 Posted: Fri Nov 06, 2009 6:01 am Post subject: rocket cooling |
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Great post Lee,
I had similar experience with my early flights and even had to land 5 minutes after takeoff as my CHTs soared into the high 400s.
I have 10:1 forged racing pistons with ceramic heads and moly b coated sides. My engine took 140 hours to finally break the last cylinder in. Until it is broke in, temps are a big problem. You found many ways to mitigate the problem but I'll bet your engine is still just running hot due to a slow and long breakin period. Consider this, the Rocket is so light that the engine does not have enough load on it to do its breakin in the normal amount of time. I started running mine 24" at 2200 rpm in an attempt to load it up and that is when the final cylinder broke in. I also reduced my timing to 22 deg BTDC to help with the increased compression.
Additionally, some local success has be realized by adding a small downward lip on the aft edge of the lower cowl to create a low pressure area where the cooling air is exiting the cowl. This seems to accellerate that cooling air which then allows more air to flow through your cowl. Jim Winnings did this with success. I was about to try it when my engine normalize.
My normal numbers are 325 or so on CHTs and I lean to 50 deg LOP after level off and a few potatoes for CHT cooling and stabilizing.
Hang in there, you will enjoy it much more when you don't have to worry so much about engine temps.
Jim Stone
Louisville KY
Friend of Ben Cunningham
[quote] ---
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Lee Logan
Joined: 10 Jan 2006
Posts: 86
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| Posted: Fri Nov 06, 2009 5:26 pm Post subject: rocket cooling |
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Jim: Good to hear from you and thanks for checking in. Be sure to say hello and Happy Birthday to Bosco for me. Great guy!! Remind him he promised to show up here in his -7 one of these days.
BTW, I agree with your analysis...in fact, though I didn't mention it, I installed a small external lip on my lower cowl exit also. It worked just as you advertise in your email. I didn't want it to be permanent (aesthetics), so cut another 1/2" to 1" off the cowl trailing edge (eliminating the lip) and that produced the same reduction in temperatures. Stuck with that.
The other issue you raised was break-in. I was never convinced that my engine had gone "over the top" all the way to break-in as I was being told by others. Not only is my engine is an interesting hybrid (IO-540K1G5 case and crank, with ECi parallel valve cylinders and 9,5:1 forged pistons) that was put together for my by my friend Bart Dalton in Oklahoma. He suggested this engine "mixture" as being super strong, powerful, and reliable. I'm pretty sure he is exactly right. I started it from day one on Phillips X/C 20W50 and just couldn't see how it could be broken in in only 15-18 hours. I will close up the NACA scoop tomorrow and see if there is any difference in oil temps. My cylinders are now running in the low 300's at cruise.
I don't have the injectors sorted out on mine yet, so I'm not where you are on LOP, but I can pull it back pretty seriously and it still runs well. I'm a gallon or better apart cylinder to cylinder going over peak, so I've got some work to do there.
Regards and thanks for the info,
Lee...
On Fri, Nov 6, 2009 at 8:47 AM, Jim Stone <jrstone(at)insightbb.com (jrstone(at)insightbb.com)> wrote:
[quote] Great post Lee,
I had similar experience with my early flights and even had to land 5 minutes after takeoff as my CHTs soared into the high 400s.
I have 10:1 forged racing pistons with ceramic heads and moly b coated sides. My engine took 140 hours to finally break the last cylinder in. Until it is broke in, temps are a big problem. You found many ways to mitigate the problem but I'll bet your engine is still just running hot due to a slow and long breakin period. Consider this, the Rocket is so light that the engine does not have enough load on it to do its breakin in the normal amount of time. I started running mine 24" at 2200 rpm in an attempt to load it up and that is when the final cylinder broke in. I also reduced my timing to 22 deg BTDC to help with the increased compression.
Additionally, some local success has be realized by adding a small downward lip on the aft edge of the lower cowl to create a low pressure area where the cooling air is exiting the cowl. This seems to accellerate that cooling air which then allows more air to flow through your cowl. Jim Winnings did this with success. I was about to try it when my engine normalize.
My normal numbers are 325 or so on CHTs and I lean to 50 deg LOP after level off and a few potatoes for CHT cooling and stabilizing.
Hang in there, you will enjoy it much more when you don't have to worry so much about engine temps.
Jim Stone
Louisville KY
Friend of Ben Cunningham
[b]
| | - The Matronics Rocket-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Rocket-List |
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