World Racer
Posted 26 November 2017 - 08:46 AM
Terry,
I'll be sending a print of the latest tuned pipe to Lohring Miller for analysis with his two stroke engine program. He has done this before on the pipe that is presently used on the oval rigger with surprising valid results.
Jim
Lohring's a sharp guy, I'm "harvesting" some of his dyno knowledge, lol. 
Beginner Boater
Posted 26 November 2017 - 09:26 AM
Thanks. You and others are doing a lot to keep the tradition of actually building things alive. Computers have helped a lot, but there's no substitute for putting tools to metal and seeing what you made perform.
Lohring Miller
National Racer
Posted 03 February 2018 - 02:14 PM
The two tuned pipes shown in the photo are similar, but they are used on different hull types. The chamber painted black is used on a rigger & the un-painted chamber is used on a cat. Both are used for oval racing. Their major diameters are the same, but the tuned length of the unpainted chamber is longer. This longer tuned length is because of the smaller included angle of the baffle cone used on the un-painted chamber. Also the unpainted chamber has no straight flex section & a much shorter flanged header section. Both chambers have a total internal volume that is approximately 24 times the displacement of the engine. A very important fact that allows the use of a long, small ID stinger for the maximum boost amount possible!
Jim Allen
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Edited by Jim Allen, 04 February 2018 - 08:28 AM.
World Racer
Posted 10 February 2018 - 08:38 AM
The two tuned pipes shown in the photo are similar, but they are used on different hull types. The chamber painted black is used on a rigger & the un-painted chamber is used on a cat. Both are used for oval racing. Their major diameters are the same, but the tuned length of the unpainted chamber is longer. This longer tuned length is because of the smaller included angle of the baffle cone used on the un-painted chamber. Also the unpainted chamber has no straight flex section & a much shorter flanged header section. Both chambers have a total internal volume that is approximately 24 times the displacement of the engine. A very important fact that allows the use of a long, small ID stinger for the maximum boost amount possible!
Jim Allen
Some good info there, thanks!
National Racer
Posted 12 April 2018 - 12:16 PM
All properly working tuned pipes will benefit greatly from having their fuel systems pressurized from the the normal pressure ( approximately 4 psi or 120 inches of water at WOT) contained in the tuned pipe chamber. This is the reason that a longer, smaller ID, stinger is desirable, but only possible if the chamber in question is of sufficient volume (approximately 24 to 28 times the engine's displacement). This applies to any type of carburetor, with or without a fuel pumping diaphragm. With this feature the fuel tank must be rigid & there is no chance of setting the boat on fire with a pressure line coming from the pipe directly to the rigid fuel tank. The rise & fall of the measured pressure varies directly with the engine's RPM's. Since the tuned pipes operating temperature is approximately 450* F at the pipe's mid section, a neoprene rubber line is used at the pressure nipple.
Jim Allen
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.625 bore barrel carburetor on QD 029.jpg 66.16KB
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.625 bore barrel carburetor on QD 027.jpg 79.18KB
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.625 bore barrel carburetor on QD 025.jpg 77.34KB
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Edited by Jim Allen, 12 April 2018 - 12:28 PM.
National Racer
Posted 20 April 2018 - 07:51 PM
The machined adaptor in the photo allows a standard CC racing pipe to be directly connected to a QD header. Both the QD header (1* 44') & the adaptor (2* 16') are tapered inside. This gives four tapered sections in the diffuser section of this pipe with no flat section anywhere.
Jim Allen
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