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shay2nak
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Discussion Starter #1
I'm sure all of you have checked out the info on the 111R. As such, i'm sure you will agree that the engine/transmission is the same as the federal elise. With that said, cross referencing the gear ratios with the top speed claim of 150 mph gives us:

1st: 48 mph (crazy!)
2nd: 73 mph
3rd: 101 mph
4th: 128 mph
5th: 163 mph (top speed reached)
6th: 183 mph OVERDRIVE (top speed reached, i think)
 

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Using the following figures:

1st: 3.116
2nd: 2.050
3rd: 1.481
4th: 1.166
5th: 0.916
6th: 0.815
Final: 4.529
Tires: 225/45-17
Revlimit: 8350rpm

I get:

1st: 44mph
2nd: 67mph
3rd: 92mph
4th: 117mph
5th: 150mph
6th: 168mph

With a 8500rpm limit:

1st: 45mph
2nd: 68mph
3rd: 94mph
4th: 120mph
5th: 152mph
6th: 171mph
 

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shay2nak
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Discussion Starter #6
well, to make sure my numbers were right, I used the same method on cars that I could check. I used the Road & Track graphic tables. Those blue pages that have all the data. For example, the BMW M3, I used its top speed of 170 mph and got virtually the same values as R&T did testing the car.

Also, I remember hearing that the elise will hit 100 mph in third gear. I was surprised when I first heard this, but now seeing the gear ratios I'm not so surprised. Only the fact that first gear goes to almost 50 mph whereas the M3 is at 40 mph.

All you have to do is divide the gear ratio and the top speed.

150/3.12 = 48 mph

1st 3.12:1
2nd 2.05:1
3rd 1.48:1
4th 1.17:1
5th 0.92:1
6th 0.82:1
 

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This site will do some calcs for you:

Race Technology

Its gives

1st = 5 mph/1000, 2nd = 7.7, 3rd = 10.6, 4th = 13.5, 5th = 17.2, 6th = 19.3

Max revs is 8350 I think -

1st - 41.75
2nd - 64.3
3rd - 88.51
4th - 112.73
5th - 143.62
6th - 161.16

Nice and tightly together!
 

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shay2nak said:
...

All you have to do is divide the gear ratio and the top speed.

150/3.12 = 48 mph...
That logic is only correct in very limited circumstances, namely when top speed is gear limited and top speed is reached in a 1.00:1 gear.
 

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shay2nak
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Discussion Starter #9
i tried the race tech site and only got a top speed of 136 mph. I don't think that is correct. I took into account the rear wheel size also. I don't think it has anything to do with the transmission and engine. Go to roadandtrack.com and check it out. it's as easy as dividing the top speed with the gear ratio.
 

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shay2nak said:
i tried the race tech site and only got a top speed of 136 mph. I don't think that is correct. I took into account the rear wheel size also. I don't think it has anything to do with the transmission and engine. Go to roadandtrack.com and check it out. it's as easy as dividing the top speed with the gear ratio.
In the case of Race Tech, the 'top speed' listed is the highest speed that the car reaches irregardless of the theoretical speed that can be obtained at redline in the highest gear. Many times, top speed is less than theoretical, due to aerodynamic limitations.
 

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No offense, shay2nak, but you're confused. Just think about what happens when a car drives. The crank rotates at a certain number of rpms, that's connected to the drivetrain, then to the the wheels. So max rpms, gear ratio, final drive, and wheel size must go into the calculation.

Looking at one of the input parameters as an example: If you increase the wheel size, and leave everything else unchanged, you're going faster at a given number of rpms.
 

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shay2nak said:
i tried the race tech site and only got a top speed of 136 mph. I don't think that is correct. I took into account the rear wheel size also. I don't think it has anything to do with the transmission and engine. Go to roadandtrack.com and check it out. it's as easy as dividing the top speed with the gear ratio.
Everything on the Race Tech calculator page is relevant. However, the purpose of that calculator is not to determine top speed, just to convert engine RPMs into car speed under the conditions specified by completing the form. To calculate top speed, you would also need the coefficient of drag (cd), frontal area, and horsepower curve. The Elise has a small frontal area, but also a fairly high cd. I suspect the actual top speed will turn out to be around 140...maybe a little more...and will reach it in 5th gear.
 

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^^^ I think he failed to adjust the rev values on the RaceTech calculator. Thus the top speeds in each gear were off.

Also, even with identical inputs, the Race Tech calculator gives slightly lower values than my calculations above, because the Race Tech calculator uses a fudge factor of 0.96 in the tire size calculator. I assume this is to account for variance of actual tire dimensions from the theoretical (I learned this by looking at their source code).
 

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shay2nak
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Discussion Starter #14
You're correct, you do have to take all of those into consideration. I just tried my way with the porsche gt3 and i was off a little. I guess i got lucky with the M3.

To me it sounds correct that the gearing would be high, especially in first & second being that the elise is a small, light car with very fast acceleration.
 

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^^^Your simple method can be close to correct, since many cars will reach their top speed in a gear close to 1.00:1 and close to the engine's revlimit.
 

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vvtlikick said:
Using the following figures:

1st: 3.116
2nd: 2.050
3rd: 1.481
4th: 1.166
5th: 0.916
6th: 0.815
Final: 4.529
Tires: 225/45-17
Revlimit: 8350rpm

I get:

1st: 44mph
2nd: 67mph
3rd: 92mph
4th: 117mph
5th: 150mph
6th: 168mph
Using the above gear ratios and tire sizes, I also get the same top speed in each gear as vvtlikick. When the CHP pull me over for speeding on the freeway I'll be able to say "But officer, I was only in 2rd gear!"
 

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Its all about power to the wheels, my own experience at 160MPH when I punch the gas my car pulls away once I start to approach 175 MPH it is a lot harder to accelerate. If I drive with the top off I notice an immediate difference in performance. However I noticed a greater difference in the 1995 S4s and theoretically the weight to power ratio on the S4s wasn’t that much different than the V8, however at 155MPH the S4s lost its oomph. Some work done on my car-upgraded chip and turbos, the biggest difference I noticed is from 60-165MPH.
 

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O.k. I'd like to see the same numbers at 6200 when the high cam kicks I'd like to know where I'll have to shift to stay on the high cam.
 

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Using the calculator RichB linked earlier, speeds at 6200 rpm:

1st: 31 mph
2nd: 48 mph (top 1st: 42 mph)
3rd: 64 mph (top 2nd: 64 mph)
4th: 84 mph (top 3rd: 89 mph)
5th: 106 mph (top 4th: 113 mph)
6th: 120 mph (top 5th: 143 mph)

I added the top speed in the next lower gear for comparison, so you can see if you end up over 6200 rpm when you upshift at 8350 rpm.
 

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Now we need the upshift at 8500rpm. If you shift then it looks like you may be able to stay on the higher cam in all the gears. 1st-2nd looks to be the trickiest.
 
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