Gear ratios are worthless. Any good solutions?
02-10-2012, 04:51 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
(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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02-10-2012, 04:59 PM
#23
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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.
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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02-10-2012, 05:20 PM
#25
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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02-10-2012, 05:26 PM
#26
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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
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
http://www.apexgarage.com/tech/gear_ratios.shtml
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02-10-2012, 07:15 PM
#30
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This is something that isn't well understood.
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02-10-2012, 07:29 PM
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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
(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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02-10-2012, 07:33 PM
#32
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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.
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.
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02-11-2012, 03:39 PM
#33
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)
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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02-13-2012, 03:13 PM
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02-13-2012, 03:47 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.
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 04:51 PM.
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02-13-2012, 04:32 PM
#38
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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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02-13-2012, 05:53 PM
#39
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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