If I build a wet pipe what would be the pipe to use?

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The WHH wet pipe system is intended to keep the pipe cool when it is inside the hull and when it passes through the transom. It will have a slight silencing effect as well. It is "full volume" water flow and has nothing to do with performance in those boats.

For true tuned pipe benefit, a properly adjusted dry pipe system will make the most torque and power ( the more heat in the pipe, the better ). If you are looking for very high RPM power, the tuned pipe is shortened to get the highest RPM. But taken too short, and the lower RPM ( turns, launching ) torque will be lacking. By injecting a small amount of water spray at lower RPM into the header ( or close to the front of the pipe ), it cools the pipe. This slows the hot exh. gases to the point where the pipe acts as though it is longer ( increasing the torque ). After the eng. gets "on the pipe", the water is stopped, and the short pipe can build very high RPM.

So a high temp. pipe passes exh. gases much faster than a cool pipe.

One of the best pipes out there is the QD Hot Pipe. It makes great performance in all ranges and uses replaceable flex sections for tuning length. A lot of guys replace the flex with stainless tubing in varying lengths. Those tubes are a great place to weld a water fitting into, because they can easily be replaced without harm to the header or pipe.

Thanks for all the great information. For future reference. With my current setup I will be getting the dry pipe set up with props etc.

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Water injection into the stinger muffler quiets the exhaust without changing the power. Water injection into the header cools the exhaust, "lengthening" the pipe. That helps the low end power but limits the peak rpm. We ran water injection on our CMB 35 SAW engine for more acceleration into the traps. The article on the CMB 35 test program (www.modelgasboats.com/magazine...5-record-engine) has dyno data on the effect.

Lohring Miller

Lohring did you turn off the water injection when entering the traps or at a set rpm?

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We turned the water off well before the traps. See the second to the last graph in the article. There is an rpm plateau at around 20,000 rpm with the water on. Turning it off allowed the rpm to rise to 23,000 rpm

Lohring Miller

Thank you for the information
Gordon

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When we are talking about water inj. to enhance lower RPM torque, It's not a full flow water stream, it's a small spray that cools down the pipe and gets steamed off very quickly. You don't want any accumulation of water, because it will go back into the combustion chamber with the supercharge. That's why the water inj. is turned off well before the speed traps, so that the pipe can get back up to temps. and produce the RPM that a short, hot pipe does.

Yes that goes with what I have been reading. Use a fine spray jet that can be controlled with 3rd channel. I guess it would help if you used a radio that had telemetry, ie temp of pipe, rpm, GPS

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A lot of guys ( it started with nitro ) would use a third channel with a servo to activate the spray. We have a system that uses no electronics, and no moving parts. No special jets are needed, just common water fittings. Telemetry could be used if you wanted to go hi tech, but most SAW set-ups are bare-bones, and simple as possible.