experiences with final drive ratio - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 10-15-2007, 07:02 PM   #21
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i liked the 4.3 better when i was at 150rwhp. i should easily be over 200 now. right now when it's cold second can get a tiny bit squirrely. so i'd say where i'm at 200-250 i have no idea that the 4.1 is about perfect.
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Old 10-15-2007, 07:04 PM   #22
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I'm enjoying the 4.10 currently...probably ~180rwhp.
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Old 10-15-2007, 07:10 PM   #23
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I like the 4.1 but i sometimes miss the torque feeling the 4.3 gave me sub 2K rpm. I think i am still about the same speed from point to point so there is a minimal acceleration loss just a little bit of loss in crispness. Fwiw spinning it around in 3rd on a 4.1 and not worrying about it breacking is priceless. Gotta love those low speed corners with plenty of straight away run out.
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Old 10-15-2007, 07:28 PM   #24
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newb questions, please no ban...a 94 r-pkg miata has a 3.9 Torsen, right or wrong? whats the typical behavior difference between the 3.9 and the 4.1? someone please explain this to me once and for all, im getting a wee bit confeused...thanks all
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Old 10-15-2007, 07:33 PM   #25
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Quote:
Originally Posted by whaaamx5 View Post
newb questions, please no ban...a 94 r-pkg miata has a 3.9 Torsen, right or wrong? whats the typical behavior difference between the 3.9 and the 4.1? someone please explain this to me once and for all, im getting a wee bit confeused...thanks all
3.9 is a taller gear.
For example: A 4.1 rear would cruise at 80 mph at 3700 rpm(guessing), a 3.9 rearend would cruise at 80 mph at 3300 rpm.
You get more use out of your gears due to this. 1st gear becomes much more usuable.
I'm going from 4.3 to 4.1 with my torsen swap and i'm really excited about it.
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Old 10-15-2007, 07:58 PM   #26
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so my 94 1.8 car with stock torsen is a 3.9 then, right? then thats a good thing, right? especially once i turbo, right? sorry for sounding so newb, but i always thought the opposite, i guess the lack of proper guidance...so glad i found this place
btw-80mph cruise is more like 4K rpm
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Old 10-15-2007, 08:04 PM   #27
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Quote:
Originally Posted by whaaamx5 View Post
newb questions, please no ban...a 94 r-pkg miata has a 3.9 Torsen, right or wrong? whats the typical behavior difference between the 3.9 and the 4.1?
A '94 R-package did come with a Torsen diff, though I'd always thought that the '94-'97 Torsens were all equipped with a 4.1 R&P. The six-speed cars, as far as I know, came with the 3.909 R&P.

The number is the first half of a ratio representing the number of turns of the propshaft relative to the number of turns of the wheel. The second half of the ratio, unless specified, is assumed to be 1. So on a '92 Miata with a 4.3:1 R&P ratio, for every 4.3 turns of the propshaft the wheels will turn once. The larger this ratio, the greater the mechanical advantage through the diff. For those people familiar with NASCAR, at Bristol they run a very high R&P ratio because they need maximum acceleration out of the turns whereas top speed is relatively low. At Daytona they use a lower R&P ratio as they need a much higher top speed, and spend much less time braking and then accelerating.

So all else being equal, a larger number on the R&P will give the car better acceleration, at the expense of higher RPMs and a lower top speed in any gear. A lower R&P number will give you lower RPMs and a higher top speed in gear, but reduce the effective amount of torque available at the wheels.

One way to visualize it is to think of yourself removing a lug nut with a breaker bar. If you have a very long bar then the nut is easier to twist, however you must move the wrench further through space to turn the nut.
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Old 10-15-2007, 08:06 PM   #28
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no, all 94-97 have a 4.10:1 r&p
99+ 5 spd is 4.30:1
00+ auto is 4.10:1
6 speed is 3.90:1, but certain euro 6 spds are 3.636:1

The lower the ratio, the higher top speed the car will have, but will sacrifice acceleration. The higher the ratio, is the opposite: lower top speed but quicker acceleration.
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Old 10-15-2007, 08:22 PM   #29
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Quote:
Originally Posted by whaaamx5 View Post
btw-80mph cruise is more like 4K rpm
I have a 4.3 and cruise at 80 mph at 4k rpm, the numbers i used were all made up.
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Old 10-15-2007, 11:41 PM   #30
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Quote:
Originally Posted by cjernigan View Post
I have a 4.3 and cruise at 80 mph at 4k rpm, the numbers i used were all made up.
Its going to be crazy to put this car in overdrive on the track.
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Old 10-17-2007, 08:59 AM   #31
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I've got the 4.3 in my 5 spd NB. If I do a swap it would be to a 3.9. I'd like a longer 1st gear and not buzzing around at 4K in 5th on the hwy.

Do you guys really car if your speedo is off?

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Old 10-17-2007, 09:24 AM   #32
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I run a 3.90 with the 1.6 5 speed. It is much better than the original 4.30, first gear is useable. I do a lot of highway driving though, I wanted to keep the revs as low as possible w/o opening up the case, so I got a 6 speed torsen.
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Old 10-17-2007, 10:52 AM   #33
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im going to germany in the spring, ill try to find some junk yards while im there and buy the 3.6 if i can find one, that with a six speed should be sex
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Old 10-17-2007, 10:54 AM   #34
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Quote:
Originally Posted by Joe Perez View Post
I went with a 4.10 for the Torsen in my '92. I can still spin the tires (T1S) in first gear, they break loose at around 4,000RPM. This isn't a big change- only 4.6%. I did not change the speedo gear, and according to my GPS receiver my speedo is now less inaccurate than it was before.
I put a 4.10 Torsen in my 90, I'm still NA but the gear does help extend the gears a bit, but its not a noticeable loss in acceleration.

My speedo seems off though...the 4.30 would tap the revlimiter in second at 62...now it only reads 60 when it should register around idk? 64-65?
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Old 10-17-2007, 11:37 AM   #35
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Quote:
Originally Posted by whaaamx5 View Post
im going to germany in the spring, ill try to find some junk yards while im there and buy the 3.6 if i can find one, that with a six speed should be sex
Planetmiata or mazmart said they were getting a 3.6 set in a few weeks ago.
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Old 10-18-2007, 03:47 PM   #36
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I think Mazmart has one in stock right now, for around $315 I think.
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Old 10-18-2007, 03:55 PM   #37
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It actually corrected my speedometer vs. GPS, but my odometer is off now.
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Old 10-18-2007, 04:22 PM   #38
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is the 3.6 a torsen?
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Old 10-18-2007, 04:24 PM   #39
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Quote:
Originally Posted by whaaamx5 View Post
is the 3.6 a torsen?
It's just a ring & pinion gear set. You can install it into whatever differential you want.
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Old 10-18-2007, 04:29 PM   #40
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Man that is alot of coin to drop on a R&P set, i don't roll that high.
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