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Ok, Dave. I didn't read your message close enough. I agree, I don't think "Plugs Down" would change anything regarding lead fouling.
Well, to answer your question, there were two factors that induced me to go plugs up (three actually). The first was that high profile items like water pump, alternator, distributor (was originally going with a breaker/electronic type ignition), would all require "bumps" in the cowl (fiberglass work). Second, I did like the idea of the exhaust turning down and back. Also the fuel line/injectors were now not hanging above the hot exhaust waiting for any fuel leak to drop down on that red hot metal. Any leak was more likely to simply drop straight down to the bottom of the cowl. It also turns out that any flooding is a none issue with plugs up for the reasons already mentioned. The third reason was - nobody was making rotary engine mounts for any orientation . Had one been available for normal orientation, I am certain I would have given it strong consideration - but, when you are rolling your own.......
There are two reasons why I don't necessarily recommend plugs up - neither having to do with any problem associated. The first is you do have to build an oil sump to replace the oil pan. While I flew with an oil pan for a short while, I could only put about 3 1/2 quarts of oil in the system before it would start to cover the oil flow-back channel from the center housing leading to oil being blown out the breather tube. The second reason is that all of the vendor offered products (there were no vendors back then {:>)) are designed for the "normal" orientation, such as motor mounts, Tracy's gear box, intakes, exhausts which makes sense as most folks go with that orientation. So why there are no technical reasons (unlike what some have claimed) not to go "Plugs Up" there are some practical and economic reasons {:>)
Probably should I ever convert over to a Renesis I would go normal orientation - one reason is the oil flow-back path in the new engine has been changed. I have not studied it carefully but it looks like you would have to drill a new hole in the center housing to provide an alternative path for the cooling rotor oil to drain back to the sump.
I am certainly not wedded to "Plugs Up", it provided a solution to a number of my design objectives and there was no vendor products to induce me to do it differently. On the other hand, there is no problem with Plugs up as my almost 8 years and 350+ hours of flight time have shown.
Ed
Ed
----- Original Message ----- From: "david mccandless" <daval@iprimus.com.au>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, January 14, 2007 8:19 AM
Subject: [FlyRotary] Re: Plugs down
Hi Ed,
thank you for your response; I had not thought of the pooling of fuel in the plugs; they are little cups, after all.
However, my main question was not in regard to flooding but to fouling, ie SAG in the cruise: why should 'plugs down' be more susceptible to fouling in cruise?
I still favor plugs up: I like the hot exhaust going straight down, but this is fine for land planes like ours, but I can see the same wish to have inlet below and the exhaust going up in a pylon mounted engine plane ala Coot .
I think I may have asked you this before but, 'what the hell', If you were doing it all over again, knowing what you know now, would you still go "plugs up"?
Always enjoy your posts,
BR, Dave McC Europa XS RX8 all alloy engine.
On 14, Jan , at 8:36 AM, Ed Anderson wrote:
Actually, Dave, it almost ensures you will be dealing with a flooded engine frequently. Any small amount excess fuel in the liquid state (not uncommon on those cold days) would pool in the spark plug holes. With plugs up, you do not have to take the spark plugs out when the engine floods. Just crank it a bit with the throttle open and it fires up. With the normal side ways orientation - you frequently (but not always) must take them out to fix a flooded engine and with them on the bottom, I think you will almost certainly have to take them out.
But, I do agree- if you do take them out, then all the excess fuel should fall right out.
FWIW
Ed
All and Sundry,
Why would it lead to a plug fouling problem?
Sure makes it easy to clear a flooded engine.
FWIW, Dave McC
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