posted on March 12, 2012 21:00
Hope you enjoyed yesterday's tasty donuts. Now here are a bunch of details that have delayed the making of stinky donuts:
At the end of the aluminum exhaust fab project, we wanted to hear our new creation, but the starter wouldn't cooperate. Though we thought we had finally solved the Miatabusa's complex starter problem, the starter we installed was built from used parts salvaged from a few broken starters. Any guesses what happens when you build with broken parts? You get another broken starter.
Though it worked on the bench, once we installed it in the car, the engine could only turn over until the first or second compression stroke before the one-way sprag clutch (the one that lets the engine outrun the starter when it finally catches) started to slip and the engine stopped while the starter motor freewheeled.
Undaunted, we decided to push start the car. Only we couldn't. Even with a foot firmly on the clutch, and the clutch hydraulics thoroughly diagnosed, the car acted like it was in gear. The clutch simply wouldn't disengage.
So we push started it with Alex's M-Coupe (backwards, since the Z3 body has too pointy a front bumper, and the Miata's front bumper cover was off anyway.) It fired immediately, and sounded like this:
The stuck-in-gear thing seemed to sort itself out immediately, but a few other problems arose. First, there was this horrendous oil leak, made much more obvious by the fluorescent goo we used to trace it.
Then there was the nasty rattling noise of the engine hitting the subframe. And, of course, the sad fact that we had built the starter in a way that made it impossible to change without removing the bellhousing. Time for the engine to come back out and remedy those problems, but not before several unrelated delays caused by the day job and the Frankenmiata.
The massive oil leak, it turns out, was caused by our attempts to prevent a massive oil leak. Let me explain...
The bellhousing adaptor we fabricated bolts to two different parts of the Hayabusa engine case. The wedge piece, shown here, bolts to the angled clutch cover face, and then the bellhousing adaptor bolts to both the wedge and the crank nose cover at the same time. To make this work, both these surfaces seed to be at the same height and perfectly parallel. That's not actually all that hard to do, with the right laser scanners, CAD tools and machining skillz, if (and believe me, it's a big IF) the Hayabusa engine cases can be trusted to be consistent.
We don't trust them though. Odds are pretty good the two faces are machined separately, on different machines in different setups. Both faces need to be flat, but neither needs to be a precise height relative to the other, since both covers are independent and don't attach to anything else. If Suzuki didn't need to keep them consistent to a thousandth of an inch, it would be foolish to assume they did.
So we didn't. Tim machined the wedge a few thousandths short, and we used a shim to bring it up to the same height as the crank cover. This strategy let us track which shims each Hayabusa engine required. Over time, if every engine requires the same shim, we'll know Suzuki kept these faces consistent, and we can start making wedges to the right height. If not, we just use a different shim for each engine.
Problem is, we somehow started with the wrong shim. The fluorescent goo clearly showed the oil leak was gushing from the crank nose flange, and when I measured the height of the bellhousing flange's two mating surfaces (the black bit is a precision straightedge), there was a 0.009 gap at the crank flange. Final assembly had happened in a furiously busy weekend, and the old measure twice, shim once strategy had been mixed up.
Monday, March 12, 2012 11:41 PM
Awww, you weren't messing with us TOO badly after all. Jubilation!
Can't wait to see some deets on tuning this thing.
Tuesday, March 13, 2012 4:16 AM
Can't wait to see the dyno pulls...or better yet the track laps. Now that the car is nearly done...when will the kits be available for sale? A Miatabusa of my very own would be a really good reason to ditch my problematic S13 (though the Miata would be far less practical than the hatchback).
Tuesday, March 13, 2012 4:17 AM
Wait, better yet, how about a Silviabusa? My SR20 doesn't pass inspection, so I'm open to ideas...
Tuesday, March 13, 2012 7:31 AM
This is such an amazing project.
Tuesday, March 13, 2012 7:41 AM
Don't know much about the Bazaaz, but you can get a Powercommander for a 'Busa motor. The beauty of the PC is there are tons of off-the-shelf maps floating around the interwebs that others have spend countless hours perfecting.
Tuesday, March 13, 2012 8:13 AM
Nice. Hoping to see MiataBOOSTa soon.
Tuesday, March 13, 2012 8:46 AM
Priapism, Yes, lots of power commander maps are out there, but how many of those tunes were perfected in a Miata with a custom header and air box? When you're doing something unique, you need unique tuning. Apex Speed Tech does a ton of tuning and Neel's really good at this stuff. Odds are, we can use the Miatabusa's tune on the Starletabusa (and 8695Beatersabusa), but we've got to start somewhere!
Tuesday, March 13, 2012 9:05 AM
Another tuning option using the stock ecu.
Keep up the great work guys!!
Tuesday, March 13, 2012 9:16 AM
"Nothing is ever simple." <- trudat, lol! nice work!
Tuesday, March 13, 2012 9:44 AM
don't remember if it was talked about in a previous entry, but are you doing anything with gearing? the miata's geared kind of low anyway and you're dropping a bit off the output rpm (after the 1.5ish reduction) so i wasn't sure if a new rear end was coming. or is the hayabusa motor meant to spin high all the time so it doesn't matter?
Tuesday, March 13, 2012 10:12 AM
Why do motorbike engines not operate in closed loop?
Tuesday, March 13, 2012 10:32 AM
The engine is designed to handle the revs, but we're still unsure whether we're equipped to put up with them. With stock gearing, the engine will cruise at 6000 rpm at 70 mph. With a 1000cc engine, that would be no problem. Still unlclear how fun that will be with 1300. A final drive change is not difficult to do, though, and there's a 3.6:1 available through Mazdaspeed Motorsports (factory gear from Australia)
Tuesday, March 13, 2012 11:10 AM
Motorbike engines do have closed loop. Their control loops are much simpler though, and it's easy to get around. On a Hayabusa I'm not exactly sure how it's done, but on a lot of bikes if you just unhook the stock wideband it will just operate in open loop mode. This is especially true if you don't care about getting a check engine light. Most bikes have a way to get around it without the light though. And since the Hayabusa is probly the most modded bike engine in the world, I have to think the method is well documented.
Tuesday, March 13, 2012 12:55 PM
*their control loops
I need an edit button.
Tuesday, March 13, 2012 1:11 PM
You and me both, buddy...
We'll know a lot more about loops and tuning and junk in a few days when Neel drops his knowledge on us.
Tuesday, March 13, 2012 1:14 PM
@ Burninator - Edited ;)
Tuesday, March 13, 2012 3:43 PM
My Ducati is alpha n with no closed loop at all.
Tuesday, March 13, 2012 8:32 PM
yeah, the 3.6 is the one i was thinking of, but i wasn't sure if that'd be enough. i don't know the ratios available for the s2000 diff and i know some people use the cts-v diff for higher power irs projects (but i don't know its ratios either)
i know the powerplant frame is still in place so i would expect you'd stay with the miata housing, but this project is so awesome/preposterous that i wouldn't be surprised if you told me you welded a ppf mount onto some junkyard diff.
also, if/when this project goes turbo, are you considering a swap to a 6 speed? i know the miata's rear is pretty decent (well, not the 90-93) but the tranny is probably the first thing to go at >250ft/lbs of torque from what i hear. i think it's case flex? i know mazda's your day job so i'm sure you've thought about all this already. i think the 6 speed with a taller rear is a nice option since the gears are so close together. with the reduction and the 6 speed being lower than the 5, it'd be nice if there was something like a 3:1 rear available
Wednesday, March 14, 2012 5:15 AM
FYI, I think I've talked myself out of a Silviabusa...for now...
Weight savings is about the same, but the car is 500 pounds heavier, plus the power is actually less. I think I'll just fix the SR instead. Now after college, when I've got a real job and some money, I think it would be fun. Either that or a Haya-Roki (AE86 with a Hayabusa motor).
Wednesday, March 14, 2012 9:53 AM
Mike - right not all motorcycles have closed loop, but most newer ones do.
And, so after doing some actual research it looks like the 1st gen Hayabusa probly doesn't have a closed loop mode, but the 2nd gen does. My bad, in my work I normally only hear about the new stuff.
Wednesday, March 14, 2012 10:37 AM
The lack of an O2 sensor was a dead giveaway...
Wednesday, March 14, 2012 11:15 AM
Yep, I'll just go back to my corner then.
Wednesday, March 14, 2012 11:41 AM
I love the detail, Dave! I'm really looking forward to how this finishes up and how Miata and Starletabusa differ.
Am I the only one hungry for a donut after reading this!? Dang you Dave and your Pavlovian hypnotism!
Wednesday, March 14, 2012 5:45 PM
Great article, I'm really enjoying this series!
Friday, March 16, 2012 5:53 PM
Ohtsukare sama deshita - literally, thank you for your efforts!
Friday, March 16, 2012 8:03 PM
I still want just the adapting stuff. Im thinking a 'Busa in a little 620 Datsun p/u is just what I need to commute the 15 miles of backroads I take to work. Or.....I could get a Kennedy Mazda to VW adapter and build a killer Bug...or.....
Saturday, March 17, 2012 11:41 PM
I am so excited about this Project!! Partly because I have a Datsun 1200 ute (very similar to the US. Datsun 620, I think) that I will be turning into a project. I have been looking at different engines (4AGZE, CA18, SR20 etc) But really really want to put a Busa in it... I mean really want to! I get told I'm mad very regularly, but when I get an idea in my head... So this is such a great project to follow. Does anyone know if its been done before? or any definate reasons it cant be done? I would appreciate any help or advice i can get. Love your work and keep the post comming.
Monday, March 19, 2012 7:53 AM
I think the 1200 ute is just like the Datsun 1200 we had in the U.S. in the early '70s, but with a truck bed. Your 1200 is unibody right? The 620 was body on frame.
This should work pretty easily in a 1200, as far as I can tell. Just use a Miata transmission of course...
Wednesday, March 28, 2012 11:09 AM
I'm sure you are already aware of this Dave but...
if not then, at least I tried to pass on the info.
Wednesday, March 28, 2012 1:36 PM
If only we all were made of money...
Friday, April 13, 2012 7:04 AM
What happened to the website yesterday? I was excited when I saw that a new post: "Project Miatabusa part 15: AEM Data Logging (and some RC plane parts)" went up, but the website was down and now that it's up, the post is gone :( I'm looking forward to part 15. Keep up the good work.
Friday, April 13, 2012 8:11 AM
It was Bill Gates. Seriously. Some Microsoft piece of crap in the long chain of digital magic that brings this silliness to your computer got upgraded and suddenly all of MotoIQ had the blue screen of death for a day. Part 15 will return on monday, hopefully with less devastating results!