Once the engine was in place I needed to make my custom set of D&D pipes in a couple of days, or die trying. The buzz was high for the Bub’s Bonneville Motorcycle Speed Trials. Dave Rash, the D&D boss, called me with the exhaust formula. He’s a speed and performance nut. D&D dyno tunes every exhaust system they make. “Don’t run 1 ¾ exhaust at all,” Dave started. “Start with 1 7/8-inch pipe for 14 inches and step up to 2-inch until each pipe is exactly 35 inches long.” Then I’m supposed to slip on and weld on a carefully designed and ground collector. Finally an empty, slip-on megaphone needed adapting

This system has been tested to give me maximum hp at 6,500 to 6,800 rpms. “We’ve discovered that the two-into-one systems generate 20 more horses than single exhausts,” said Dave.

Here’s more on performance exhaust systems from Paul Davis:

The Nascar exhaust are stepped, 3 steps for each runner. They are different animal though. For bikes 3 steps, 2 into 1 "Y" merge collector are a real good combination for the street.

You see alot of drag racers use 2 into 1 w/ a "Y' merge colllector. Top Fuel, Pro Stock, Pro Mod, etc. What you'll notice is usually they have 3 steps. 3 different dia. smallest dia. starting from the head. It's really nothing new.

Three steppin' moves the power band up and prevents reversion. Ceramic coating and or header wrap keeps the exh. gases moving good.

Individual pipes are good at WOT. Look at NHRS record setting Buell. They don't use a typical 2 into 1 Buell race pipe. Indivdual runners like what you were talking about using. Your thinking of Aero is right on.

--Paul

I was wrapped as tight as a .45 magnum shell the first day of pipe making. Bonneville was looming like a 10 pound ballpeen hammer over my thumbnail. We were scrambling, making calls, counting our pennies, praying for surf, and yet it was all going reasonably well in our over-heated shop—unless any obstacle jumped in the way or caused unforeseen delays and slowed progress. It was smoking that day as temperatures on the coast glided toward the 90s.

Enough sniveling, I had pipes to build, wiring to figure out and hydraulic lines to make. We were bugged by our first two- into-one attempt and I didn’t like how far they stuck out in the wind. I was burnin’ daylight and grappling with decisions. I like to make a solid plan, after thorough research and go for it. I questioned my plan, called Berry Wardlaw and Dave Rash for info, bobbed and weaved into action again with the best data at my back. We needed the pipes on and the bike plumbed and primed by Thursday when Berry Wardlaw, from Accurate Engineering flew in for tuning and dyno work. Man-oh-man, we were cookin' with hot grease and lots of garlic.

I needed to jump back into the shop. My nerves were shot, my head over-loaded with info and not enough time was pressuring me to the deck.

This is what we came up with, the first round. “I’m damn proud of you guys,” Dave rash said when I e-mailed him this image.”

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