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Aug 24th, 2023
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Joined: Feb 2016
Posts: 306
Learner Plates Off!
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Learner Plates Off!
Joined: Feb 2016
Posts: 306 |
Sounds like we need some real world application here and see what's up. Really if anyone can do some measurements it would be great to see if there's room to even cram one of these in without having to modify chassis.
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Joined: Feb 2016
Posts: 7,941 Likes: 218
Talk Morgan Guru
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Talk Morgan Guru
Joined: Feb 2016
Posts: 7,941 Likes: 218 |
I've found the opposite to be true, rarely have I see a 6 speed transmission where you have an "overdrive" 5th as well as an overdrive 6th. Unless it's something with an absurdly high top speed and a hell of a lot of horsepower. i.e. Lambos and the like.
Nearly all the BMW M series have 5th as the 1:1 with everything before it being closer together, rather than just adding potential higher top speed. Same with the higher powered subarus. Their 5th is close enough to 1:1 as makes no difference.
For a vehicle that tops out at around 115-120 or so, having a closer ratio transmission, while there's the possibility for a little more rowing, it gives you a lot more time in the sweet spot in your torque band and you don't have an absurd drop from 1st to 2nd.
Regarding autocross the less time you have to shift, the better off you are. I don't think that many of the M3W crew are doing autocross though.
I think for the Miata itself though skipping gears can also be attributed to what rear end you're running. What's the ratio yours is running?
I'm definitely with richard on this though. I love a close ratio 6 speed for overall driving, than a 5 speed with a lot wider spacing. Both the 5spd and 6spd NC miatas run 4.10 rear end/final in the US. I do not know if a different read end/final is offered in other parts of the world. For comparison sake NC ratios below; 5 Speed 1st-3.14 2nd-1.89 3rd-1.33 4th-1.00 5th-0.81 6 Speed 1st-3.82 2nd-2.26 3rd-1.64 4th-1.18 5th-1.00 6th-0.79 If you notice, the ratios are extremely close both in the low end and on the higher end which leads many to skip gears. While shifting in AutoX is due to the fact of not wanting to shift often, with such close gears it leads to almost no advantage to shifting and doesnt help much in keeping you in the ideal torque curve, but rather eeps you peddling through gears or skipping them on leisure drives. While this can be fun, I dont think it results in much of an advantage over the 5 speed. Available ratio's aside what I would ideally like to see is first and top gear with the same 5 speed ratio's, which seem spot on to me. Downshifting I often miss a gear, even two when approaching slow traffic or roundabouts. I would rarely miss one going up though no matter how close. Ironically having a greater choice of gears in town would likely reduce the number of changes I presently make, saving having to continually go up then down a gear.
Richard
2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone
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Joined: Jan 2014
Posts: 1,075
Has a lot to Say!
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Has a lot to Say!
Joined: Jan 2014
Posts: 1,075 |
If they are both in 3rd gears, its a 1.64 vs a 1.33. Of course these is going to be a difference between the two.
In practical application, the closeness between 3rd and 4th in the 6speed means that I often find myself skipping 3rd all-together as I dont need it for much. If I were racing, it might be beneficial to eek out each gear to keep it in the torque curve. However for everyday use its honestly just as well to have the 5speed.
My guess is that it would be cheaper and easier to simply swap out ratios and keep the 5 speed vs grafting in the 6 speed. In case you're interested, Quaife offers a Miata 5 speed close ratio gear set. Available in the following ratios. 2.564 - 1.670 - 1.273 - 1:1 2.345 - 1.544 - 1.222 - 1:1 They don't say anything about 5th, but we'll just assume it's still the OD as it was before.
Dan
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Joined: Feb 2016
Posts: 306
Learner Plates Off!
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Learner Plates Off!
Joined: Feb 2016
Posts: 306 |
I think 5th in those kits are 0.794 and 0.868 respectively.
That definitely seems like a racing gearset though. Taking off with a 2.564 ratio would I think definitely qualify as lugging the motor.
Dan, while it's still a couple years off, when I get my three wheeler I'm contemplating driving it back home. So Illinois to Texas, probably stop half way at some family down in the Ozarks, but I could very well be swinging near St. Louis. Perhaps we could grab a bite to eat.
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Joined: May 2012
Posts: 1,790 Likes: 3
Talk Morgan Enthusiast
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Talk Morgan Enthusiast
Joined: May 2012
Posts: 1,790 Likes: 3 |
For me 2nd and 3rd could do with a tweek, 2nd on some corners is too low and 3rd too high. Otherwise its pretty much ok.
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Joined: Jan 2014
Posts: 1,075
Has a lot to Say!
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Has a lot to Say!
Joined: Jan 2014
Posts: 1,075 |
I think 5th in those kits are 0.794 and 0.868 respectively.
That definitely seems like a racing gearset though. Taking off with a 2.564 ratio would I think definitely qualify as lugging the motor.
Dan, while it's still a couple years off, when I get my three wheeler I'm contemplating driving it back home. So Illinois to Texas, probably stop half way at some family down in the Ozarks, but I could very well be swinging near St. Louis. Perhaps we could grab a bite to eat. Yes, a stop by would be quite a treat. Always open to meeting people of common interests. As far as gear sets like I listed above, you would usually compliment it with a 4+ rear end ratio. In the old days of the Muncie 4spd trans here in the US, the M20 had a low at 2.54 and the M21 and M22 had a 2.2 low gear with both having 4th at 1:1. You put a M21 or M22 behind a 409 in a '62SS Impala and all you can do is hang on for your life. I had a '62SS with the M22 rock crusher trans, but the 409 had been swapped out for 283FI motor, but it still had the 4.11 rear gears. I swapped out the rear for a 3.36 rear and it kind of livable at that point. Oh, those were the crazy days of the US muscle car days.
Dan
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Joined: Oct 2015
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Has a lot to Say!
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For me 2nd and 3rd could do with a tweek, 2nd on some corners is too low and 3rd too high. Otherwise its pretty much ok. Hmmmmm... my experience would just change your numbers above out to a 1 and a 2.
The Original Ken
11,000 miles.
2014 BMW R9T
2005 Saabaru
2005 Saabaru
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Joined: Jul 2013
Posts: 3,660 Likes: 48
Talk Morgan Addict
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Talk Morgan Addict
Joined: Jul 2013
Posts: 3,660 Likes: 48 |
For me 2nd and 3rd could do with a tweek, 2nd on some corners is too low and 3rd too high. Otherwise its pretty much ok. Hmmmmm... my experience would just change your numbers above out to a 1 and a 2. But you've not seen how fast Dab of Oppo goes... 
Red Leader 
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Joined: Jul 2011
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Talk Morgan Regular
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Talk Morgan Regular
Joined: Jul 2011
Posts: 836 |
The Quaife kits are only for gen 1 and 2 transmissions.
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