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On Monday, January 17, 2005, at 06:15 PM, Leon wrote:
Hi Jerry,
Looks like you have copped the same treatment that I copped, and still continue to cop. HIM (His Imperious Majesty) never misses an opportunity to put someone down if they are right and he is wrong. He's been bad-mouthing me for the past three years.
Unfortunately, the majority on the ACRE mailing list believe whatever HIM says is true, including all the the libel and slander. And there is no right of reply or redress of grievances.
As John Slade rightly says, those of us who know what it's all about might start taking notice of him when he actually gets a plane in the air, or even an engine running. But, what about all the poor people who are being willingly misled??? In the meantime I suppose, it's a case of "Them's wot can ... DO, them's wot carn't ... prognosticate!"
As for the size of any PP runner, the ONLY way ANYONE will know is to DO it, build the engine, and dyno the sucker. From my perspective of a car racer, it's not only size, but actual port timing and shape that makes a difference. This is all RPM dependent. The higher the RPM, the more overlap and the bigger the ports and runners that can be accomodated.
As a racer (as opposed to an aviator), we are always trying to get MAXIMUM power, which means BIG runners, and LOTS of ARE PEE EMMS. Current PP thoughts are 52mm ports being fed by 60 mm throttle bodies with a tapered runner. Great for 10,000 -11,000 RPM, But this just wouldn't work in an aircraft. The engine wouldn't even get on the pipe until around 5,500. A two piece, centre bearing crank is mandatory.
Obviously, the corollary is true. While not being a fan of PPs for aircraft use, I can only agree with you. At the RPM we are using in aircraft, the overlap needs to be reduced (port size, shape, and placement on the trochoid), and the runner sizes and lengths need to be commensurate with the gas speed required, as well as any back pressure caused by mufflers. In the end, this can only be a matter of applying a bit of intelligent theory and doing some educated surmising, guided by whatever people have done in the past, and then followed by trial and error and dyno time.
For instance. I'm developing a four runner manifold for the race car. The current one in the pix is steel (for ease of fabrication), and will be replaced by an all alloy manifold once the development is finished. So far, we have picked up an extra 25 BHP throughout the RPM range, and something like 35-40 BHP at the top end.
I eventually want to have computer controlled adjustable length runners. Easily done with a stepper motor and a worm shaft. Now I already have a ROUGH idea about lengths, based on past expereince, but until I actually put the car on the dyno, I really didn't know EXACTLY what length would work at what RPM with the current style of bridgeporting I'm using, and the actual mufflers and exhaust system on the vehicle.
So, I've made the trumpets manually adjustable (crude by effective), and have done some dyno tuning and track time to see what lengths work at what RPM. I am now at that point in time where I can get my machinist to make an adjustable trumpet mechanism of the correct stroke. I know HIM has been talking about it, but I'm actually doing something practical about it!! Just do likewise Jerry. Don't let the nay sayers get you down. In the end, you will know who's right, because the dyno is the final arbiter.
Cheers,
Leon
Nice looking Bells, Leon. Point the injectors into the bell mouth and you have what I am working on. We should have a prototype plenum with fuel rails, filters, maybe even Ram within a month or so. I am not now nor have I ever been worried about our p port performance. We have Everett Hatch and Alan Tolle before us and Power Sport flying now, so we know roughly what performance to expect. Plus I have the excellent engineering of Rolf P. predicting what our performance will be. I have never been tempted by larger p ports, as they are clearly not appropriate for lower rpm engines( below 8000 rpm.) Our ports will function to that level quite nicely. They are sized and positioned to eliminate overlap as much as possible. They open late and close late. I am willing to predict that we will make at least 210 hp at 6000 rpm and maybe as much as 220. At 7500 rpm the hp will be around 250. But this is just talk, enjoyable blather actually. The dyno will tell all. If the engine can turn my 3 bladed Catto that was too much prop for a 200 hp Lycoming, I will be happy. Jerry
<BTSRX3AirBox1.jpg><BTSRX3Trumpets3.jpg> Homepage: http://www.flyrotary.com/
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