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Old 02-10-2012, 05:47 PM   #21
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Old 02-10-2012, 05:51 PM   #22
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Sav going to a 3.636 from a 4.3 will make them 15% longer, not 18% FYI. Not a huge difference but some.

(4.3-3.636)/4.3 = 15.44%

http://www.percent-change.com/index.php?y1=4.3&y2=3.636
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Old 02-10-2012, 05:59 PM   #23
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Quote:
Originally Posted by Savington View Post
Your power doesn't start at "mid 3000rpm". If each shift dumped 3000rpm off the tach, I promise that your car would be way, way slower than it is now. You want to keep the revs high so the engine is producing as much power as it can for as long as it can. If you are shifting too much, you don't need longer gears - you need a longer rear end.



Thankfully the laws of physics still apply to your transmission, despite what the rest of this thread says. Switching to a 3.636:1 rear end will stretch every single one of your gears by 18% without affecting the output produced by the motor (longer gears = more rev drop = less output after each shift). IIRC, a 6sp/3.636 combo has a very similar gearset to a 5sp/4.30 combo, only with a taller 6th for cruising.

What you really want is a lighter clutch, BTW - that's the secret to silly fast shifts. I can shift the 6-speed in Theseus fast enough that the MAP sensor never falls below 100kpa, and I don't use flatshift.

Great - The 18% was a measure that I was hunting for. This is great news.

As far as my power starting- I was not suggesting that I should shift into the mid-3000 zone I was just saying that I'm wasting a good part of my power ban. Looking at my torque curve 4400 would be a great starting point for my gears.

Gear calculator link - Not fully configurable but should work for us:

Flyin Miata - LINK

As far as ratios go- I could be wrong but I think you both might be looking at the overall final drive, not the length of each gear individually. Maybe it's the same thing but if i take the top speeds from each setup there is 18.2% difference and if I look at the difference between rear end ratios it's 15.4%.
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Old 02-10-2012, 06:03 PM   #24
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Gear calculator link - Not fully configurable but should work for us:

Flyin Miata - LINK
Yea....no one here has the pockets or ***** to do a custom set so that's more than sufficient.
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Old 02-10-2012, 06:20 PM   #25
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Quote:
Originally Posted by 18psi View Post
we need a gearing calculator link in here pronto lol
plug in the numbers, get the mph readouts = make a smart decision on which fd you need.
well I have an Excel spreadsheet for just that, but don't know how to upload an .xls file

in addition to listing all the available rear end ratios, and transmissions ratios, it also takes tire size and computes mph/rpm in all gears

PM me an addy and it is your
or if a moderator wants it to post as a sticky, that is OK also
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Old 02-10-2012, 06:26 PM   #26
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Quote:
Originally Posted by mx594m View Post
well I have an Excel spreadsheet for just that, but don't know how to upload an .xls file

in addition to listing all the available rear end ratios, and transmissions ratios, it also takes tire size and computes mph/rpm in all gears

PM me an addy and it is your
or if a moderator wants it to post as a sticky, that is OK also
Here's an easy one, but like I said, it's not going to tell you any more than the Flyin' Miata calculator

http://www.apexgarage.com/tech/gear_ratios.shtml
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Old 02-10-2012, 06:29 PM   #27
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I top out at 160 at 7500 rpms....can anyone figure out my setup!?!?!
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Old 02-10-2012, 06:32 PM   #28
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Quote:
Originally Posted by Boost Joose View Post
I top out at 160 at 7500 rpms....can anyone figure out my setup!?!?!
want a cookie?
queef.

Last edited by 18psi; 02-10-2012 at 07:58 PM.
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Old 02-10-2012, 07:52 PM   #29
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not that it matters, but R225/40-15s, a 6-speed, and 3.636 rear would compute to 160.58 at 7500 rpm, ignoring slippage, drag, and other loses
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Old 02-10-2012, 08:15 PM   #30
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Quote:
Originally Posted by hustler View Post
3.63 is the way. You're still going to shift frequently, but you'll have gearing out to 161mph.
Incorrect, you will shift less often because for a given speed you will be using lower gears with the taller diff. Lower gears are more widely spaced. Gears get more closely spaced as you upshift.

This is something that isn't well understood.
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Old 02-10-2012, 08:29 PM   #31
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Quote:
Originally Posted by Boost Joose View Post
Sav going to a 3.636 from a 4.3 will make them 15% longer, not 18% FYI. Not a huge difference but some.

(4.3-3.636)/4.3 = 15.44%

http://www.percent-change.com/index.php?y1=4.3&y2=3.636
The speed in-gear is increased by ~18% in each gear when you switch from 4.30s to 3.636s.
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Old 02-10-2012, 08:33 PM   #32
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Quote:
Originally Posted by Dem768 View Post
Great - The 18% was a measure that I was hunting for. This is great news.

As far as my power starting- I was not suggesting that I should shift into the mid-3000 zone I was just saying that I'm wasting a good part of my power ban. Looking at my torque curve 4400 would be a great starting point for my gears.
Post your dyno chart and I'll explain why that's almost certainly not ideal.
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Old 02-11-2012, 04:39 PM   #33
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Looking at options for my own case (5sp+4.875:1 now) i found that it was completely useless to look elsewhere than the stock 6speed combined with a "readily" available Mazda final gear (unless you want sequential).

For a higher strung N/A engine 6sp+4.3:1 and skip 1st, "creating" a 5speed with a long dogleg 1st.
For F/I it seems (MT "wisdom") like you do the same but use a 3.636 instead (until you break stuff too often).

I had 6sp+3.636 in my stock 03 and the 1st is decent starting gear for stock power, so I'd judge the 1st useless for any other case (more power or lower final gear).

I made a crude table to help me (converted to mph for your comfort)
Code:
mph   7500 rpm Shift point
       590 mm Wheel diameter
Gear  Ratio Next rpm 4.875   4.77   4.44   4.3    4.1    3.9   3.636
1st   3.163  4476.8   33.6   34.4   36.9   38.1   40.0   42.0   45.1
2nd   1.888  5295.3   56.3   57.5   61.8   63.8   67.0   70.4   75.5
3rd   1.333  5626.4   79.8   81.5   87.6   90.4   94.8   99.7  106.9
4th   1      6105.0  106.3  108.7  116.7  120.5  126.4  132.9  142.5
5th   0.814          130.6  133.5  143.4  148.1  155.3  163.3  175.1


1st   3.76   4525.9   28.3   28.9   31.0   32.1   33.6   35.3   37.9
2nd   2.269  5437.4   46.9   47.9   51.4   53.1   55.7   58.6   62.8
3rd   1.645  5731.0   64.6   66.1   71.0   73.3   76.8   80.8   86.7
4th   1.257  5966.6   84.6   86.4   92.9   95.9  100.6  105.7  113.4
5th   1      6322.5  106.3  108.7  116.7  120.5  126.4  132.9  142.5
6th   0.843          126.1  128.9  138.5  143.0  150.0  157.6  169.1

Quaife
1st   2.564  4884.9   41.5   42.4   45.5   47.0   49.3   51.8   55.6
2nd   1.67   5717.1   63.7   65.1   69.9   72.2   75.7   79.6   85.4
3rd   1.273  5891.6   83.5   85.4   91.7   94.7   99.3  104.4  112.0
4th   1      5955.0  106.3  108.7  116.7  120.5  126.4  132.9  142.5
5th   0.794          133.9  136.8  147.0  151.8  159.2  167.4  179.5
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Old 02-12-2012, 12:49 AM   #34
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FM is working on a conversion kit to mate the CTS diff with the 6speed. You could have a 3.42 ratio that way.
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Old 02-13-2012, 04:13 PM   #35
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Quote:
Originally Posted by Savington View Post
Post your dyno chart and I'll explain why that's almost certainly not ideal.
This is the best pic I have available until I get home but I think this is either my final or just before my final sheet. 4400RPM is just after my peak TQ so with flat foot shifting it seems like it'd be a good starting point?
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Old 02-13-2012, 04:47 PM   #36
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Alright so thank you for everybody's input. After reading through all of this information I've determined the actual data that I need to know.

I've created this chart to show the potential speed increase per gear with each differential setup that I'm considering. You'll see from the chart that the 6 Speed with the 3.636 rear end leaves me with the closest possible outcome to the much more desired 5 speed ratio setup but with increased top speed and a usable 6th gear with reasonable RPM while cruising on the freeway. Keep in mind this chart was made using my 7500RPM redline so it might not apply to your vehicle.

Also keep in mind. This is with 225/45/16 tires.

Last edited by miatauser123; 02-13-2012 at 05:51 PM.
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Old 02-13-2012, 04:53 PM   #37
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Not quite sure how you got those numbers.....
ratio mph @7500 rpm
1st 3.760 37.5
2nd 2.269 62.1
3rd 1.645 85.7
4th 1.257 112.1
5th 1.000 141.0
6th .843 167.2

(6 speed, 3.63 gears)
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Old 02-13-2012, 05:32 PM   #38
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Quote:
Originally Posted by Boost Joose View Post
Not quite sure how you got those numbers.....
ratio mph @7500 rpm
1st 3.760 37.5
2nd 2.269 62.1
3rd 1.645 85.7
4th 1.257 112.1
5th 1.000 141.0
6th .843 167.2

(6 speed, 3.63 gears)
You just listed the top speed in each gear. The chart shows the MPH gained in each gear. Essentially showing everyone how much longer the individual gears will be. This is the "Not well understood" part of the equation and more importantly the usable information in my case.
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Old 02-13-2012, 06:53 PM   #39
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Quote:
Originally Posted by Dem768 View Post
You just listed the top speed in each gear. The chart shows the MPH gained in each gear. Essentially showing everyone how much longer the individual gears will be. This is the "Not well understood" part of the equation and more importantly the usable information in my case.
I think he's referring to your top speed with the six speed and 3.636 gears vs his. Yours are off for every gear compared to the calculators he provided. If your top speed for each gear is off so will your speed between gears.
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Old 02-13-2012, 08:39 PM   #40
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Mine aren't off for my setup- I used the Flyin Miata calculator. He might have different tires though.
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