Q: Why on earth do this? A bike engine? You must be joking.

A: Valid question. It even took a while to convince myself it was a good idea. But when you look at the numbers, it becomes pretty self explanatory. 

The main reason is weight savings. The Hayabusa engine, transmission, and all accessories weighs 194lbs. The Miata engine, transmission, and all accessories weighs over 500lbs, a weight savings of 300lbs!! What's more, the weight savings is almost all from the font of the car, improving weight distribution and reducing polar moment, making the handling more akin to a formula car as opposed to a Miata. Not to mention consumables such as tires, pads, and rotors will last much longer.

The list goes on and on, but I'll be brief:

- 200hp

- Revs to 11,000 rpms

- The Exocet version is 100lbs lighter than the Ariel Atom, and 100lbs heavier than the Radical SR3

- Sequential transmission (can be fitted with the optional paddle shifter and ignition kill module/auto blip for clutchless shifting)

- Ease of installation and maintenance. The mounting system is extremely simple with initial installation taking roughly half a day. After the initial install, the engine can be removed in about 20-30 minutes with one person

Q: But doesn't it have like zero torque?

A: Actually, considering it's displacement, the Hayabusa engine makes substantial torque with Gen 1 making 100ftlbs, and Gen 2 making 114ftlbs. Comparatively, a stock 1.6 Miata makes 95ftlbs and an NB2 (the one with the VVT engine) makes 125ftlbs. Assuming we're comparing apples to apples, that's already not terrible considering all the other benefits of the Hayabusa engine. But we're not comparing apples to apples, far from it in fact. The main reason being torque is for moving mass. Less mass, the less torque is required to accelerate quickly. It's possible to get a Hayabusa powered Miata down to about 1,600lbs, including 6 point roll bar with door bars. That's a lot of torque per pound. The other reason is torque multiplication. The Hayabusa motorcycle is geared to top out at 200+mph. Though we may want to, we have no business going that fast in a Miata. Using any of the commonly available factory Miata diff options will produce tons of torque multiplication and modest top speeds. The 4.3 diff will result in a top speed of 100mph, perfect for auto-x. The 3.6 diff, commonly paired with the FUji diff, will result in 127mph top speed. The 3.9 diff produces a top speed of 117mph. This is my personal favorite. Violent acceleration and enough speed for most tracks. These speeds are all with the stock 'Busa rev limit. An ECU flash will raise the rev limit, thus increasing the top speed a few mph for each rear end option.

 

Q: What about maintenance? Does the engine require lots of service?

A: We did 10 track days with the test vehicle. Watkins Glen, Lime Rock, Palmer, and several days at Pineview Run, and the only maintenance we performed is oil and filter changes.

 

Q: Is it fast? what's the top speed?

A: Acceleration in 1st-3rd gear is brutal. It'll hit 115mph with relative ease, and it mechanically tops out at about 120mph at most tracks with a 3.9 Miata diff. This 120mph limit is the kinetic energy threshold we designed around (more on that in the next FAQ), so we don't recommend trying to increase the top speed without first at least upgrading transmission components and increasing clutch spring pre-load. But with more power, the Miata 3.6 diff should get it to around 130mph top speed.

But due to the nature of this swap, we can't just consider straight line speeds. Where this swap excels is in the braking, corners, and corner exit. We managed to achieve a 59s lap at Lime Rock only reaching about 117mph on the straights. You don't necessarily need to go fast to be fast if you can stop and turn fast.

Q: Do you need to make any modifications to the tub or subframe?

A: Nope! No subframe modifications or expensive tubular subframe required. No tub modifications required, which means you won't have to invest in an expensive "precision poundometer."

 

Q: But won't it just break?

A: Believe it or not, this is a pretty widely used power plant for lightweight, motorsports oriented cars. From high end Westfield hill climb builds, to the Radical SR3, to the Thunder Roadster GTR race car, this engine has proven to be a reliable and desirable powerplant despite the advent of more powerful and modern motorcycles.

But this is something we really wanted to get right, so we used a little physics. Peak loading and shock are the main factors we considered during design. We discovered that the kinetic energy of a Hayabusa traveling 180mph (a very attainable speed for a stock Hayabusa) is the same as a Hayabusa powered Miata going 124mph. Taking into account the difference in drag between a Miata and a Hayabusa, we determined a mechanically limited top speed of 120mph in the Miata will reproduce loading similar to the factory Suzuki design threshold. However, de-restricted Hayabusa's have been known to reach speeds in excess of 200mph without additional supporting mods, so we feel that 120mph provides a safe peak load that will ensure reliability for many, many track days. For you street guys, it'll probably last forever.

Q: Does it use the Miata transmission?

A: Nope! Using the Hayabusa sequential transmission saves about 80lbs, and creates opportunities for all kinds of fun stuff like paddle shifters and no-lift, clutchless shifts.

 

Q: What about the transmission? Doesn't it have like tiny motorcycle gears?

 A: Yes, they may be slightly smaller, but I'm sure you've heard the trope "size doesn't matter." Well, that is particularly so in this case. Road going cars use conical shaped gears and a series of syncros. This improves driveability and reduces NVH (noise vibration and harshnes), but at the expense of weight, complexity, and performance. The Hyabusa transmission has straight cut gears. This means there's no need for syncros or other supporting mechanisms which reduces weight and complexity. Additionally, straight cut gears have much more tooth engagement than conical cut gears, which distributes the load more evenly, reducing stress on the gear.

Q: But can it reverse tho?

A: Yes. Reverse will be an option. For the short term, we will be offering a 1:1 reverse gearbox with 2 piece driveshaft as a reverse option. The neat (albeit useless) thing about this option is that you'll have 6 forward gears as well as 6 reverse gears. The company that produces them holds the world record for fastest speed in reverse. 

We're also working on our own lower cost option in house that will use an electric motor for reverse.

Q: What about power steering, air conditioning, heat, things of that nature?

A: Lol. This kit is pretty hardcore and pretty track focused. Admittedly, it probably wouldn't make a great daily. In my 20s, I definitely would have dailyed it, but as a 35 year old I need my air conditioning. Things you'll have to live without:

- Power steering

- Heat 

- Air conditioning

- Brake booster (trust me, you won't miss it)

Q: What does the kit consist of?

A: I'm assuming if you're into something like this, you've probably wrenched before. The base kit with just the essentials is a good option to keep costs down. However, some things you'd either need to source or fabricate yourself to complete the build. But if you don't want to do that, we'll be offering every component you'll need to complete your build, from wiring harness, to shifter. The base kit will consist of:

- Complete set of engine mounts

- Driveshaft

- Output shaft flange

- Headers

- Clutch solenoid mounting bracket

Some options will include:

- Lever actuated cable shifting system

- Lever actuated electronic shifting system

- Paddle actuated electronic shifting system

- Intake manifold to clear stock Miata/Exocet hood

- Reverse

- Modified wiring harness (vestigial components removed, fuel pump and gauge cluster harness lengthened, tip-over and kickstand switches deleted).