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Old 12-12-2008, 11:02 PM   #1
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Default Sequential gearbox?

Anybody ever heard of/seen any sort of a sequential gearbox in a Miata? I don't need/want one now, but once I get into time trials and hill climbs heavily I think it would make life simpler. Also what is up with maximum required torque?

On a second looksy, I think Rec'd refers to recommended, not required
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Old 12-13-2008, 01:23 AM   #2
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I don't believe I've ever seen a sequential gearbox installed in a Miata.

Modifying the stock gearbox would seem to be nearly out of the question- there's just not enough space to locate a drum anywhere near the selector rods. I was going to suggest that perhaps Mendelola could come up with something, but it seems that all of their products are intended for rear / mid applications.

There are a couple of companies that make "generic" sequential gearboxes, which could be adapted to fit a Miata with the correct bellhousing and tailshaft. Here are some examples:
Hewland SGT Gearbox Specification
Elite Racing Transmissions | beagleengineering.co.uk

Know that these boxes are insanely expensive; as in $10,000+.

Another option would be to remove the whole Miata engine and transmission and install a motorcycle powerplant, such as a Suzuki Hayabusa or a BMW K1200.
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Old 12-13-2008, 03:21 AM   #3
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I think in the end it would actually be less expensive to do a whole motorcycle powerplant transplant than those other sequentials
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Old 12-13-2008, 04:39 AM   #4
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turbo busa miata?
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Old 12-13-2008, 06:00 PM   #5
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Originally Posted by 18psi View Post
I think in the end it would actually be less expensive to do a whole motorcycle powerplant transplant than those other sequentials
Oh, cheaper by far. That $10k I posted is just for the center section. You still have to fabricate a bellhousing adapter and a tail section to actually mate it to a car.

And I'm only half kidding about the bike engine. You'd have to beef up the clutch, and probably the gears and shafts in the transmission, but there are plenty of folks who are making >300 HP on a regular basis with 'Busa engines. Remember that for a given torque, HP increases linearly with RPM; and those bikes are rev-limited to "only" 12,000 RPM in stock trim.

The most insane one I've ever heard of dynoed at just over 700 bhp. It was made clear that this was not a practical drag bike, it was purely a dyno queen.
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Old 12-13-2008, 08:59 PM   #6
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yeah I saw the Hewland website last night when I was putting up this thread, lots o' choices. However cool the V8 busa motor idea sounds, I'll stick with the 1.6. I did notice that most sequentials have the gearbox mounted in the rear and were synchro-less. True that to thousands upon thousands of dollars too btw. Could a motorcycle transmission somehow be used somewhat successfully mated to the 1.6?
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Old 12-13-2008, 09:43 PM   #7
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Quote:
Originally Posted by mazda/nissan View Post
yeah I saw the Hewland website last night when I was putting up this thread, lots o' choices. However cool the V8 busa motor idea sounds, I'll stick with the 1.6. I did notice that most sequentials have the gearbox mounted in the rear and were synchro-less. True that to thousands upon thousands of dollars too btw. Could a motorcycle transmission somehow be used somewhat successfully mated to the 1.6?
The busa is a inline 4, and was a very fast motor, but dated now. Now the new one that just came out would be wicked. But as far as the 99-06, any of the 05+ (or 06 for honda) 1000cc's are faster. But I guess if you were going to build it and turbo it. It would be wicked... But expensive
I would rather do a monster swap, or a LS1... Just my .02 cents.

I bet the Ls1 would light the tires up at 75 or 80. And I'm not talking turbo. That z28 my cousin had would stay sideways to 65 mph. and it was a automaticwith 327 gears. With the traction control on, it would still light up second. But when you turned it off. man sideways and fish tailing till 65, and had forever top end. Like 160mph.

Even with 14psi on my car, I think it would shut my miata down........

Good luck on the tranny.
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Old 12-13-2008, 09:47 PM   #8
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have you not seen the V8's people have made utilizing 2 busa motors and custom parts?

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Old 12-13-2008, 09:57 PM   #9
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Straight crazy..... But I like anything powerful. What people do for horsepower.LOL
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Old 12-13-2008, 10:39 PM   #10
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Quote:
Originally Posted by mazda/nissan View Post
Could a motorcycle transmission somehow be used somewhat successfully mated to the 1.6?
Hmmm.

I mean, anything is possible if you're willing to put the effort into it. On most Japanese bikes, the engine and gearbox share a common housing, but a Harley gearbox might work- they're typically separate and connected by an external belt drive. The input and output shafts are both on the same (left) side, so some kind of mechanism would be required "reach around" with the input shaft. In fact, if I'm not mistaken, I believe the input and outptut shafts on a hog box are coaxial.

I have no idea how one would respond to the torque of an automotive-size engine.

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Originally Posted by Toddcod View Post
The busa is a inline 4, and was a very fast motor, but dated now. Now the new one that just came out would be wicked. But as far as the 99-06, any of the 05+ (or 06 for honda) 1000cc's are faster.
True. I tend to fall back on the GSX-R because of name recognition and reputation. The 'Busa benefits from an enormous following in the aftermarket parts department like few other motorcycles. A Lotus Exige might be faster than a Honda Civic, but which one has more bolt-on goodies available?
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Old 12-13-2008, 10:49 PM   #11
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Sequential shift transmissions are fantastic. But I agree, the only 'cheap' way to get one in a car would be to graft in a bike engine. The crankcase/gearbox combo are so tightly integrated in most sport bikes it would be hard to separate them without some serious custom fabrication. They are not modular like Harley transmissions.

If I had the means I would without hesitation put a high-RPM V8 (like the Busa based V8 above) in a Miata. Just the sound alone would be worth it.

Standing in turn one, when the first lap of an endurance race is being completed at TWS, and 20 or 30 high-rpm bikes are flying down the front straight, near redline, bearing down on you doing 140MPH+ (after slowing down a bit)... the sound makes me misty nearly. I need to record it in stereo sometime. It is simply beautiful.
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Old 12-13-2008, 11:33 PM   #12
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that V8 busa motor made by the Radical guys comes out to a cool $32,000... for the small one Guess my best bet would be to get the NMT 6 speed offered by Hewland
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Old 12-14-2008, 04:50 PM   #13
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Quote:
Originally Posted by ZX-Tex View Post
Standing in turn one, when the first lap of an endurance race is being completed at TWS, and 20 or 30 high-rpm bikes are flying down the front straight, near redline, bearing down on you doing 140MPH+ (after slowing down a bit)... the sound makes me misty nearly.
A while back, I saw a clip of the Suzuki Stratosphere being revved up at the Tokyo show. For those unaware, this is an inline-6, ripping up to >10,000 RPM. The sound was... moving.

This has really got to to wondering about the feasibility of such a conversion. It wouldn't be impossible to split a Jap case in half and weld it up, and it'd be downright easy to use a Harley box. The big question in my mind is whether it'd survive.
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Old 12-14-2008, 09:24 PM   #14
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Quote:
Originally Posted by Joe Perez View Post
A while back, I saw a clip of the Suzuki Stratosphere being revved up at the Tokyo show. For those unaware, this is an inline-6, ripping up to >10,000 RPM. The sound was... moving.

This has really got to to wondering about the feasibility of such a conversion. It wouldn't be impossible to split a Jap case in half and weld it up, and it'd be downright easy to use a Harley box. The big question in my mind is whether it'd survive.
yeah I think its limits would be well pushed on a stock Miata, much less something pumping out near 300 ft/lb's. Do the BMW bikes have an integrated gearbox? I think some of them are driven by a drive shaft, that could make things easier?
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Old 12-14-2008, 09:33 PM   #15
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Quote:
Originally Posted by Joe Perez View Post
Oh, cheaper by far. That $10k I posted is just for the center section. You still have to fabricate a bellhousing adapter and a tail section to actually mate it to a car.

And I'm only half kidding about the bike engine. You'd have to beef up the clutch, and probably the gears and shafts in the transmission, but there are plenty of folks who are making >300 HP on a regular basis with 'Busa engines. Remember that for a given torque, HP increases linearly with RPM; and those bikes are rev-limited to "only" 12,000 RPM in stock trim.

The most insane one I've ever heard of dynoed at just over 700 bhp. It was made clear that this was not a practical drag bike, it was purely a dyno queen.
well they have a ton of busa powered smart cars, and while the miata is heavier its still not TOO much more. I would think a boosted busa engine/tranny would be ridiculous on a miata, though not very practical.

with v8 engine/tranny swaps available nowadays with kits to ease the process, I think that is the best way to go if you wanna go for big power and a reliable tranny. I mean a smashed z28 sells at auctions for cheap, a buddy of mine just bought one for 2200. keep engine/tranny/etc and part out the rest, and I'm sure you could get 1000 back. IMO its very possible to complete a v8 miata for under 10k, even 8 if you can fab up some of your own parts instead of paying ridiculous money for companies to make you a "kit". buy everything used, put some work into it, and you have a fast car with a ridiculous power/torque curve. if you get bored (which is crazy) you can always cam that v8 engine or stick a blower on it, in which case good luck staying alive
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Old 12-14-2008, 10:52 PM   #16
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Quote:
Originally Posted by mazda/nissan View Post
Do the BMW bikes have an integrated gearbox? I think some of them are driven by a drive shaft, that could make things easier?
On the old ones, the gearbox was a separate unit, but mated to the engine in a really odd way. But that's an intriguing idea- they are correctly set up with the input and output shafts on opposite sides.

On the newer transverse bikes it wouldn't work, as the input is turned 90 relative to the output shaft.

Quote:
Originally Posted by 18psi View Post
well they have a ton of busa powered smart cars, and while the miata is heavier its still not TOO much more.
The problem I see is that a Miata engine produces a hell of a lot more torque than any bike engine. That's what kills transmissions.
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Old 12-14-2008, 11:55 PM   #17
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I've torn down/reassembled a couple of Japanese bike engines. The transmission 'casing' is so integrated into the main case that there would not be much left by the time it was separated; plus a lot of the structural integrity of the case would be lost. There is not a lot of extra material on a bike engine/trans. They are very optimized designs with thin wall cases.

By the time all of the damage was properly corrected/adapted it would probably be easier to just machine a new transmission housing for the bike sequential gear set. The output shaft on the bike is already splined for the chain sprocket so that could probably be adapted to a driveshaft. The transmission input shaft is a different story. A lot of them are gear drive from the crank to the trans input (through the clutch) so that would need to be dealt with. Turning the input gear into a swash plate mount or something like that could work. Then there is the WET clutch to deal with... And the lack of a reverse gear... and the output shaft offset when the engine is centered in the chassis... you get the picture.

Not saying it cannot be done, and these things have been solved for kit cars, but damn, at that point I'd rather just have a Super 7. In fact you can go to the Super 7 site and see the assembly they fabricated for the Busa adaptation.

Even if I did my dream V8 Busa engine conversion, I'd just put a really nice regular shift 6-speed in it.

Last edited by ZX-Tex; 12-15-2008 at 12:08 AM.
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Old 12-15-2008, 12:44 AM   #18
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I suppose the older BMW shaft driven transmission could work, cryo the internals and use on a race only application, where reverse wouldn't be necessary (i don't think it would at least). Plausible?
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Old 12-15-2008, 01:31 AM   #19
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Old 12-15-2008, 01:36 AM   #20
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product inquired! that would be odd though, and I'm not sure that not operating the clutch would save time while still moving the H pattern. And 1st being in 5th's place kind of baffled me, until I though about how often you would use 1st gear, so you would just be working 4 gears in a tight H pattern..... hm... I wish they would have replaced gear 2 with 4th gear, that would make things easier, only requiring a horizontal change on the 3-4 shift
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