Project Miatabusa Part 2 the engine is in!

Project Miatabusa - Part 2: The Engine Is IN!

by Dave Coleman

A few short months ago, when we introduced project Miatabusa, (part 1 is here) it was little more than a reasonably well thought out concept. We had measured some things, made a rough SolidWorks model of what we thought a Hayabusa engine mated to a Miata transmission might look like, and confidently put our Miata's original engine on Craigslist. We had a plan, but in all honesty, it still didn't seem that real.

Well kids, we've cut metal and bolted an actual Hayabusa engine to our transmission using an actual billet adaptor plate. This shit is officially real. Before the back-slapping begins, lets step back and look at the concept again.

  MIatabusa STEERING rack interference  

The idea of using the Hayabusa's built-in 6-speed sequential dogbox was rejected early on. Experience has shown that bike transmissions wear out too quickly when subjected to car-sized loads. Experience has also shown that not having reverse is less convenient in a car than it is on a bike.

Bolting a Miata flywheel to the Hayabusa's crank was also rejected. Not only is the 11,000-rpm powerband a poor match for the Miata's gearbox, but the crank doesn't have any provisions for anything as big as a flywheel on the end. Both ends of the crank are small, like the front of a car crankshaft.

Like nearly all motorcycles, power transfer from the crank to the gearbox is through a big gear, and in the Hayabusa's case, the gear reduces speed (and multiplies torque) by a factor of 1.596:1. This is where the Hayabusa's clutch resides, and this is where we decided to put our flywheel--on what was once the bike transmission's input shaft.

This solution keeps the maximum revs coming into the Miata transmission down to a very manageable 6900 rpm, virtually identical to the engine it was designed to support. This should keep flywheels from exploding, synchros from protesting, and powerbands from being horribly out of step with the needs of a car.

Starting with this assumption, we made a rough SolidWorks model of the Hayabusa engine, with a Miata bellhousing pattern centered on the Hayabusa's clutch shaft. After a few measurements, it became clear that this layout posed a problem. The Miata's steering rack went right through the Hayabusa's sump. Not cool.

Rev B. solved these problems by rotating the engine so the offending portion of the sump sits above the rack, and ditching the compact Hayabusa starter, which sadly has a not-so-compact gear drive that pushed the engine an inch and a half farther forward than otherwise necessary. The plan, at this point, was to use the Miata starter to spin the miata flywheel (a task for which it is uniquely suited).

   MIatabusa layout drawing
Our original concept looked roughly like this, with the engine leaned toward the passenger's side at the same angle it normally leans (to the front) in the bike. Rotating the engine until it was vertical helped clear the steering rack.   The perspective in this view is different, but the flat section on top of the green bellhousing plate will be horizontal in the car. The big pink gear is the power takeoff gear. The yellow structure behind that is an adaptor that bolts to the clutch cover mount, and the green plate mates to the bellhousing. 

Removing the Hayabusa starter's gear reduction box exposed the back of the crank. We had to seal it back up to keep oil from gushing out the hole, so we took the opportunity to solve two problems at once. Our new design is in two pieces. The first piece, which replaces the Hayabusa's clutch cover, will hold a giant double-row ball bearing that supports a flywheel shaft and the big power takeoff gear. Behind that, we'll bolt up a bellhousing adaptor plate.

The clutch cover wasn't load bearing, though, so it was held on with tiny, 6mm bolts, and the bosses those bolts thread into are thin and delicate. In its new role as a car engine, this flange has to withstand not only the torque reaction forces from the engine's output, but also some substantial bending loads from the weight of the transmission. To help address this, we decided to use the bellhousing plate to cover that gaping hole at the nose of the crank. This second ring of bolts (and a few alignment dowels) well offset from the flywheel centerline will help take those torque reaction forces.

Theories and solid models are fun and all, but the real sexy stuff comes when you start smelling cutting oil. Turn the page, hit the jump, click on the tiny little "next page" down there, and take a look at how it all works out.

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Saturday, July 03, 2010 4:01 AM
So in a drag race, which will win? The Metro-Gone, the Angry Hamster, or the Miatabusa? Or how about in an autocross? Or the 24 Hours of LeMons for that matter? Super cool stuff, nobody in Super Street has the balls to try stuff like this.
Saturday, July 03, 2010 5:02 AM
The only way this would be cooler is to put the Suzuki in a Suzuki! It must be awesome having access to supercomputers and CNC machines...
Saturday, July 03, 2010 5:11 AM
It looks like it's shaping up real well! I love the methodical approach and can't wait to see the end result!
Saturday, July 03, 2010 5:57 AM
I'm pretty sure the only supercomputers in use are in Tim and Dave's heads. In any event, this is an awesome project! Looking forward to part three.
Monday, July 05, 2010 12:44 AM
Very very awesome!
Dusty Duster
Dusty Dusterlink
Monday, July 05, 2010 2:42 AM
You know, I was wondering where Dave Coleman, automotive Geek of Geeks, had gotten to after leaving Sport Compact Car. I'm glad to see he's still dreaming up completely ludicrous projects.

This car is going to be sick.
Monday, July 05, 2010 5:11 AM
why not ditch the starter all together and rely on push-starts? That seems to work fine for 410 modifieds. jk
Monday, July 05, 2010 5:54 AM
Wicked gangster. I wanted to do this, as well, but keep the bike trans, with one of the super indestructible drag race gearsets, and take enough weight out of the car to keep it alive. Who needs reverse anyway?
Monday, July 05, 2010 6:40 AM
Dave, you are missing the obvious. Remote mount the starter and make the output shaft of the starter longer. Done it many times. You could mount it way back next to the tailshaft (good for weight distribution) or shove it way forward. Depending on the length of the shaft, you may have to support it in the middle.
Monday, July 05, 2010 6:52 AM
How about a fourth pedal for a kick starter?
OMG Its Weasel
OMG Its Weasellink
Monday, July 05, 2010 7:48 AM
a kick starter would be hilarious. especially for a LeMons car, if thats what this is going to become.
Mike Kojima
Mike Kojimalink
Monday, July 05, 2010 8:12 AM
I think the Tilton starter is an old Nissan or Hitachi part. Nissan probably discontinued it so Tilton can't get it.
Monday, July 05, 2010 8:15 AM
Make it a hybrid with a stop/start alternator/starter. BAS(belted alternator/starter and BAS plus. Then all you need is like - a couple hundred pounds of batteries.

Love it, cool project. Still needs a turbo.
Monday, July 05, 2010 9:39 AM
Per Mike's comment on the starter being an old Nissan or Hitachi part... if that's the case some cross-referencing might be in order to find out what car model(s) it came on and then it could be sourced from an autorecycler/junkyard.

However if the idea is for the complete kit to be comercially available one day then that idea wouldn't really fly :(
Monday, July 05, 2010 5:47 PM
Holy crap, I need to become an apprentice for you guys.
Monday, July 05, 2010 6:09 PM
Go fast or suck!!!!

This is so absurd and ridiculous there's nothing bad to say about it.
Monday, July 05, 2010 6:43 PM
Long-time lurker here (former NPM reader and NFer... yo, Mike!)... gotta say... when you guys build something, you BUILD something... I've seen some wicked custom-fabs on this site, but that clutch cover has got to take the cake!

So... when are you selling the transplant kit?
Dave Coleman
Dave Colemanlink
Monday, July 05, 2010 7:29 PM
Wow, Steve (M-Workz), I've never heard of anyone doing an extended-shaft remote mounted starter. Where have I been?

I'm still holding out hope that there is a small enough starter out there for us. I've been looking at japanese mini trucks lately. Getting warmer...
Monday, July 05, 2010 11:08 PM
Awesome little project Dave. How about torque though?.....a fully gutted Miata can get as low as 1900 lbs....it needs torque......turbo maybe?
As far as small Japanese trucks, check this site:
Good luck with your project.
Tuesday, July 06, 2010 4:31 AM
It's mentioned right in the article that they're eventually planning a turbo. The first step though really needs to be to get it running.
Tuesday, July 06, 2010 6:38 AM
Why don't you guys just make a pull starter :-P
Eric Hsu
Eric Hsulink
Tuesday, July 06, 2010 9:24 PM
Didin't the Mazda 10A have a tiny ass starter? I remembered saying, "whoa dude, now that is small." Dave just go into the Mazda museum and jack one.
Wednesday, July 07, 2010 5:46 AM
@ Dave the mini trucks idea is a good one, but something I thought of when this project started was why not use parts from the cappuccino? I plan one day to either import one completly or just drop the motor from one in the Miata (the turbo set-up sounds to good to pass on). Love the project and can't waiti see the end results. And on a side note I was an avid reader of SCC and was reading the build up of your AE and the last issue I ever got was kinda a cliff hanger about your suspension tweaking, is there and more reports on how it ended up?
OMG Its Weasel
OMG Its Weasellink
Wednesday, July 07, 2010 4:26 PM
i would like to say something kind of unrelated-related to the main article.
i am really happy that mazda still holds automotive enthusiasm in high regards.
i am glad that there is still an auto manufacturer that holds a meet and greet for their quirky little "girls car" that has a cult following, and embracing the engineering that goes into a properly modified vehicle.
its not everyday, especially with the economy the way its been, that large corporations transcend their banker imposed limitations to hold events for people who are loyal to their brand.
you dont see GM hosted Camaro Days, or Ford financed Mustang Corrals.
i commend you Mazda. thanks for being all that is right in corporate-customer relations.

dave, i too would like an update on that AE project from way back.
Jeff Naeyaert
Jeff Naeyaertlink
Wednesday, July 07, 2010 5:03 PM
Really? Looks like GM is putting some pretty good $$$ into their annual LSX Shootout:

2010 GMPP LSX Shootout

In fact, this year they're "celebrating the 5th gen Camaro"

over $50k in prizes. I'm not hatin' but looks a lot bigger than a parking lot party at Mazda HQ ;) Hopefully it will be better than their lame sevenstock events where you can't bring your RX7 in if it has a V8, yet you can bring your vehicle of any other make provided it has a rotary... stupid rotards. ;)
Dave Coleman
Dave Colemanlink
Wednesday, July 07, 2010 5:46 PM
AE project? What's an AE?
Thursday, July 08, 2010 8:22 AM
The Corolla projecy lol sorry about that. You where working on the valving of the suspension the last I read.
speed freak
speed freaklink
Thursday, July 08, 2010 1:17 PM
I have a zx14 powered Miata that I have 3/4 of the way built. Since the 14 motor is much stronger and the transmission is tons stronger. I didn't need to do all the drive line silliness. Plus there is not the huge power loss and weight gain with the giant Miata transmission. My other zx14 powered cars have put down right at 190 to 198 RWH. This one is going to get a turbo to help break the silly mark of 300 hp. I have to admit that I made almost all the parts but Muzzy and Schnitz have helped me source all the common performance pieces, as well as some cool one off stuff to. It will be run in NASA in SU or STR1 depending on the configuration and hp of the final setup.
Dave Coleman
Dave Colemanlink
Saturday, July 10, 2010 7:39 PM
RS Motors, the AE project was Jay Chen, not me.

Speed Freak, how about a link? Pictures, or it didn't happen...
Sunday, July 11, 2010 10:27 AM
An amazing project!
My kudos to the team with the smarts to even think about something like this. I can't wait for a finished product. Lotus Super 7 clone here I come - what an awesome powerplant and transmission - both bulletproof and proven.

Dan Barnes
Dan Barneslink
Sunday, July 11, 2010 10:51 AM
Summit is your friend for mini starters.
Sunday, July 11, 2010 11:31 AM
When it comes to time to put wheels on it..
speed freak
speed freaklink
Monday, July 12, 2010 9:17 AM
I've tried to post here but they must be to large so I will put them on my facebook and have an update today.

Tuesday, July 13, 2010 3:56 PM
There is a waaay easier way to do this. I Put a GSXR in a 81 corolla a few years back. get a driveline adapter and go straight to the rearend. you lose reverse gear, but its an easy way without machining and getting crazy with the tranny/bellhousing. I race cars called dwarf cars, and they have this set-up. for more info call me, I sell the adapters. 7756907223 billy
Tuesday, July 13, 2010 3:57 PM
oh, and with that set-up, you use the bike starter.
Tuesday, July 13, 2010 6:49 PM
driving the rerarend off the right side(clutch cover side) wont that make the car go backwards? with all the rearend ive done this to, the rearends are clockwise. this ones gonna be counter-clockwise. The adapter I mentioned replaces the counter sprocket. I'm excited to see how this turns out. You guys are actually making parts with CNC. I didnt have that much money to do mine.
Tuesday, July 20, 2010 8:18 AM
"Speaking of exhaust, that's problem #3. There were daydreams of the factory Hayabusa header somehow fitting in the car, but there simply wasn't room. A custom header is being designed as we speak to wrap around the front of the engine."

Damn. This means there won't be a way to do this and make it street legal in CA. :(
Jeff Naeyaert
Jeff Naeyaertlink
Tuesday, July 20, 2010 9:06 AM
the exhaust is pretty much the least of their concerns if they wanted to make it legal... CARB won't allow you to put an engine from a different vehicle "type" into another (e.g. truck engine into a car). Even if they were able to get around that, you are also required to use the same transmission as the donor vehicle which ain't happening here either.
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