Vance & Hines’ Dominant Suzuki Hayabusa Pro Stock Motorcycle

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Vance & Hines’ Gen III Suzuki Hayabusa NHRA Pro Stocker has had great success in its first season. (Suzuki/)

V&H’s new rider Gaige Herrera, on the 2023 Suzuki-inspired billet-engined Pro Stock Motorcycle drag bike, has won the first three NHRA national meets this year.

I flew to Charlotte, North Carolina (site of event 2), to talk with Andrew Hines and Eddie  Krawiec, who are both former PSM champions and are now managing the team.

Krawiec began by saying that to him, there’s nothing too demanding or special about riding the bike. What fascinates him and draws him forward is the unrolling of the future in the form of innovations devised by the continuing conversation between the two of them.

He also made it clear that sheer performance cannot win national titles by itself. It is only one part of an overall racing process, which, run after run, returns a consistently competitive motorcycle to the starting line for the next pass.

An instructive element in this is the clutch, which must be inspected and possibly adjusted after every run. It contains no springs; the pressure that compresses the plate stack to send torque from the engine into the V&H six-speed transmission comes only from centrifugal weights that spin with the engine-driven part of the clutch.

Krawiec described the action of the clutch as feeling like a torque converter, as it is flyweighted to keep engine rpm in its range of maximum torque.

Clutch access requires the exhaust collector to be removed, followed by the eight fasteners retaining the clutch cover. The bike is angled several degrees to the left on its stand to prevent oil loss from the open clutch cavity on the right side. Next year’s design will eliminate having to pull the collector by providing a smaller “jockey cover” above the collector.

I saw that there are no gaskets to cause delays.

“We got tired of gaskets,” Andrew said. “There are no gaskets on this engine; we O-ring everything.”

Each bike carries a data collection system that presents the team with a continuous record of engine rpm and other variables during each run. Experienced analysis of the recorded data can lead to adding or subtracting weight from the clutch arms, or to other changes. Each of the four stepped header pipes in the exhaust system carries its own oxygen sensor, making it possible to treat the four-cylinder inline engine as four separate engines, each with its own particular needs.

Post-run analysis of data can lead to changes before the next. (Suzuki/)

The new engine is very tall and its weight is packaged forward—more forward than is possible for the billet twins. This is potentially important in a drag racing class limited to a 70-inch wheelbase.

The Suzuki Engine’s Roots in the Past

Although NHRA for product identification reasons must call this bike “Gen III Hayabusa,” and despite its carrying bodywork “inspired by” that of the new Hayabusa, the all-billet engine remains a conceptual descendent of the original GS750 and 1,000cc engines of 1976 and later. It retains that design family’s center cam drive and its pressed-together nine-piece roller crankshaft—even though the production Hayabusa’s cam drive is at one end of a one-piece plain-bearing crank. This has been done to preserve parts interchangeability with the many engines for which V&H presently supply racing parts and services (I learned they service 800 to 1,000 customer cylinder heads each year).

The original GS1000 engine’s bore and stroke were 70 x 64.8mm, but NHRA’s actions taken to adjust parity within PSM over the years now allow 89.5 x 73.4, giving 113ci. For that displacement with four valves per cylinder, NHRA imposed a 630-pound minimum weight. Lightest in the class is the limit for 2V or 4V Kawasaki fours, at 107 cubes and 575 pounds.

Performance

Power? I was told “more than 400 hp at 14,000.” For all you folk who grew up being told piston speed reaches a limit at 4,500 feet per minute, that is a piston speed of 6,740 feet per minute, or 50 percent more than that supposed “limit.”

More than 400 hp at 14,000 rpm! (Suzuki/)

The result is elapsed times in the high sixes. An “incremental time report” provides more data than the simple “time slip”—telling us that the first quarter of the strip (1,320 ÷ 4 = 330 feet) takes roughly 2.8 seconds for a PSM to cover, then 1.5 seconds for the second 330, 1.3 seconds for the third, and just over 1.1 second for the fourth.

The Six-Speed Gearbox

Although the original GS Suzukis were five-speeds, the narrower range of this engine—strong from 11,800 to 13,800—requires a six-speed. V&H machine gear blanks including the dogs. Then pieces requiring internal splines are sent for broaching and the gear teeth are cut by another specialist. The finished parts are then heat-treated. To make six gear pairs fit into a five-speed space, the height of the engaging dogs has been reduced.

In line with the concept of minimizing turnaround time at events, this six-speed seamless-shift gearbox is built as a “cassette” which can be extracted from the engine case with both shafts and their shift drum on a “door” in 10 minutes. As a next step they plan to make a new “door” that will accommodate six speeds with full-height engaging dogs.

Seamless Shifting

To avoid the “interruption of service” that occurs as a conventional gearbox first disengages the gear pair that are driving the bike, then engages the next-higher ratio, drag bike gearboxes are built in so-called “seamless” fashion. In a seamless box, the next gear is engaged without first disengaging the ratio that had just been driving. Normally, this would result in a double engagement and a transmission lockup, but modifications are made to prevent this.

The non-driving faces of the engaging dogs are cut as angled ramps, so that as the gear pair that had been driving rotates backward, the ramped dogs kick it out of engagement. An altered shift drum is required to permit this.

First and top gear lack the disengaging ramps. Small springs assure that the gearbox will “reset” for the next run.

V&H’s Pro Stock ’Busa uses a seamless six-speed gearbox. (Suzuki/)

Hines invited me into the truck, where he was making changes to a six-speed, and I was able to see the details of its construction. The V&H truck is like all such vehicles, being provided with lighted workbench space on both sides, below which are drawers containing parts and equipment. When I asked if I might see a piston or other internal parts, the answer was that because no one has time for engine service at events, only complete spare engines are carried.

Gear changing is pneumatic via a button on the left bar, sending air pressure to a cylinder under the left side of the engine, operating the shift lever.

The Cylinder Head

The cylinder head now has 16 valves, intake diameter being “in the high 30s” and the exhausts “in the low 30s.” All are operated by F1-style lightweight finger followers rather than by the cylindrical tappets used formerly.

Billet drag engines have no cooling system—no fins, no water jacket. Heat generated during each run is absorbed by engine mass, and is then cooled in the work area by blowers. During each run, cylinder head temperature rises, but enough material is provided to prevent its rising high enough to provoke detonation.

Vance & Hines’ 16-valve billet cylinder head atop billet cylinders and crankcase. (Vance & Hines/)

The present roller crankshaft is also made by V&H, assembled and trued on equipment designed and built in-house. Andrew Hines said the “flywheel wedging tool” in this setup, created in 2009, was his first CAD project, employing a brake caliper piston to exert the crank truing force.

Approved Gasoline

Hines referred to a series of NHRA-approved racing gasolines they have run in PSM engines. Gasolines are tailored to the application: Pump gas, for example, is given greater volatility in winter to provide quick starting, but less volatility in summer to avoid vapor lock.

In racing, use of high compression ratios increases torque, but also makes destructive detonation more likely. The defense against this is to raise the fuel’s octane number (ON, a measure of detonation resistance). But this in turn becomes a problem because the most detonation-resistant fuel components are larger molecules which lack volatility (the boiling point of toluene, which has a high ON, is up at 231 degrees Fahrenheit, and that of octane is 258 degrees). What this means is that if you single-mindedly design a fuel to have the highest possible ON, it may evaporate poorly, resulting in a slower-burning lean mixture.

So a compromise is made: boosting ON with fairly heavy fuel components, but taking care to maintain volatility by adding light fractions like butane (ON ~ 92).

So important to performance are these variables that V&H have studied combustion using combustion chamber pressure transducers from Austrian development, simulation, and testing firm AVL to record just how fast or slow combustion is with different fuels.

Let’s compare the volatilities of two types of gasolines—Sunoco’s SR18, used in the unsupercharged Pro Stock Motorcycle class, and VP’s C16, blended for use in turbocharged racing classes.

SR18 is very volatile, with an initial boiling point of 99 degrees Fahrenheit and a final boiling point of 223 degrees.

C16 is much less volatile, with an initial boiling point of 193 degrees Fahrenheit and a final BP of 351.5 degrees.

Why the big differences? The gasoline used in unsupercharged PSM engines has only the engine’s natural heat and intake turbulence to evaporate it. But in a turbo engine, with its compressor spinning at a zillion rpm, generating extra heat and turbulence, a heavier and less volatile fuel, its composition more tightly focused on highest possible ON, can be evaporated to form a fast-burning fuel-air mixture. With all that “help” a turbo fuel doesn’t need to boost its evaporation with components having high volatility but lacking 10–20 points in ON.

Tubular Steel Chassis

As per NHRA regulation the Gen III Hayabusa’s chassis is 0.058-inch wall chromoly welded steel tubing. It is a twin loop design with its two upper tubes arching up over the engine. A light telescopic fork with twin discs completes the front end, and the rear is rigid, supporting the 10-inch-wide slick without suspension. To bring the chain line far enough to the left to clear the tire, the transmission’s output shaft is made extra-long, well supported by an outrigger bearing in the frame itself.

Between the engine and rear wheel is an open bay in the chassis occupied by two batteries, a crankcase evacuation pump, and an oil separator. One battery serves the engine and its systems. The other drives the quite loud pump (Hines demonstrated it!). Crankcase evacuation reduces friction loss by making it possible to run lower-pressure oil scraper rings (as used on late Honda RC45 World Superbike, Yamaha’s M1 MotoGP engine, etc).

Take a look at the deformation of the Mickey Thompson slick. (Suzuki/)

The Mickey Thompson slick is mounted on a sheet metal disc wheel. Hines commented that there is quite a lot of air volume in the wheel itself, and that if the volume of inflation air were reduced it would change the tire’s spring constant.

What Does “Stock” Mean?

Eddie Krawiec described the process by which NHRA maintains the visual connection between the drag bike’s bodywork, which is necessarily longer and lower, and that of the stock bike. Two obvious features of the new production bike—the “side gills” and cobra’s head seat back—are preserved in the race bodywork, as is the ever-greater degree to which the fairing is coming forward to “eat” the front wheel. The windscreen on this bike is a stock Hayabusa part!

What’s so stock about this Pro Stock racer? The windshield is a stock Hayabusa part. (Suzuki/)

Making a Bike Go Straight at 200 MPH

He also noted, “It’s really easy to make a good shape bad in a hurry.” To prevent this, V&H digitized the bodywork’s shape in order to make its two sides identical. More and more often now, PSM bikes are reaching 200 mph, at which Hines notes the ram pressure of air is 7/10 of 1 psi. If that pressure acted over a 5 square foot (= 720 square inches) bike frontal area, the drag force would be 720 x 0.7 = 504 pounds. Streamlining reduces this force considerably, but you can see how a lack of “drag symmetry” could exert a force large enough to make a bike hard to steer at speed.

The Intake System

Digital fuel injection is legal in PSM, so actual carburetors have become rare (although on some engines, flat-slide Lectron carburetors are used as fuel injection throttle bodies). This bike has instant throttle response, producing a brain-drilling sound intensity. Although butterfly throttles are the present motorcycle industry norm, this bike has pivoted-gate throttles that pass air around only a single edge, not the two edges of a butterfly. In an engine combining large bore (over 3-1/2 inches) and high rpm it is essential to achieve the best possible mixing of fuel and air as far upstream as possible. Any fuel that fails to evaporate by the instant of ignition can have the effect of leaning out the mixture.

Experience and curiosity pay dividends at the dragstrip. (Suzuki/)

I asked Hines about intake port downdraft angle: Is it near zero like that of the original GS engines (to make their carbs fit under a traditional gas tank), or is it steeply downdraft as in recent Japanese sportbike design?

“It’s neither the one nor the other, but somewhere between,” was his response.

In an earlier conversation last year I had asked if he’s considering the adoption of a one-piece plain-bearing crankshaft.

“I think about it all the time,” was his response.

It may arrive as soon as next season.

Again and again in these conversations I could see that the major asset V&H brings to Pro Stock Motorcycle is not a big truck backed up by machining centers and advanced tooling. It is the accumulated experience of these people, their curiosity about every result, and continuing study of cause and effect that have made their work successful.

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