reido

iTrader: (1)

I'm thinking of changing out the gearset in my 04 STI for one with wider ratios.
I don't think I could afford a PPG dog set (it looks like that has my ideal ratios), and so the STI high speed ratio gearset, which is basically the 07 ratios with a slightly higher 5th and 6th and is quite affordable.

I did the math and came up with these differences between gears and the differences between the stocker and the percent increase in spacing.





The gearset is only 1.1k. I'm trying to get better ratios for street driving with the intended torque curve and rev range I plan to run.

The stock 04 gears are too short for me with any engine behind it. I did some math from an acceleration perspective and it's more effective to space the gears out than it is to increase the horsepower rating by XX amount.

I'd just like a ride or a test drive in a parking lot or on the road to feel the ratios.

STiAlain

iTrader: (8)

I would love a 07 limited...sigh...

houdni

iTrader: (1)

there is 07 limited sti on island ...

zer0shift

Yeah the tech at Subaru owns it.

R_T_I

Are you trying to space out the gears to reduce the number of upshifts necessary to accelerate to a certain speed (e.g. 0-60mph) or reach a certain distance (e.g. 1/4 mile)? If this is not the case, what math did you do that told you taller ratios would make your car accelerate faster?

reido

iTrader: (1)

1/4 mile script. I didn't do the math to calculate the acceleration changes. I did however calculate the MPH for different gear ratios and redline (with different tires) and the drop in rpm for each shift. I was looking to pair the gearing with my intended build to get the highest are under curve.

MPH redline with high speed gearset
17" tires
750038.0 61.7 90.6 121.3 154.7 195.0
with 18s
7500
redline39.5 64.2 94.3 126.1 160.9 202.8 9k RPM with 17s
9000
redline45.6 74.0 108.8 145.5 185.7 234.0
9k with 18s
9000
redline47.4 77.0 113.1 151.3 193.1 243.4


MPH redline with stock gears
7500
redline38.0 58.1 78.3 102.4 142.0 182.4

With 18s
7500
redline39.5 60.4 81.4 106.5 147.7 189.7

17s 9k redline
9000
redline45.6 69.7 93.9 122.9 170.4 218.8





I was looking at different torque curves and rev ranges with tire size and ratios.

I also don't like the spacing on the 04 on the street in general for normal driving, but the spacing on the 07 ratios doesn't look to make a "huge difference" on the simulator with the stock redline.
That changes with slight ratio changes and an increase in rev range (with taller tires). With the stock ratios, I have to increase torque by a considerable amount at the stock redline. I didn't save the all of the data, but for some reason I saved the results of the stock calcs.

T MPH Feet RPM Gear G Rear% Note(s)
0.01 0.31 0.0 6000 1 1.400 112.0
0.01 5.80 0.9 6000 1 1.391 111.6 *rollout*
0.25 13.13 4.2 6000 1 1.391 111.6
0.50 20.75 10.5 6000 1 1.389 111.5
0.75 28.36 19.6 6000 1 1.387 111.4
0.85 31.40 24.0 6042 1 1.386 111.4
0.86 31.56 24.4 6072 1 0.725 84.5
1.00 33.68 31.1 6481 1 0.664 82.0
1.21 36.40 42.0 7005 shift -0.018 54.3 *shift point*
1.25 36.39 44.1 7005 shift -0.018 54.3
1.50 36.29 57.4 7005 shift -0.018 54.3
1.55 36.27 60.1 7005 shift -0.018 54.3 *60 ft*
1.72 36.33 69.1 4571 2 0.577 78.5
1.75 36.71 70.8 4618 2 0.575 78.4
2.00 39.83 84.8 5011 2 0.564 77.9
2.25 42.86 100.0 5392 2 0.543 77.1
2.50 45.78 116.3 5760 2 0.523 76.3
2.75 48.56 133.6 6109 2 0.488 74.9
3.00 51.14 151.9 6433 2 0.453 73.4
3.25 53.53 171.1 6734 2 0.421 72.1
3.41 54.97 183.8 6916 2 0.402 71.3 *optimum shift pt*
3.50 55.66 191.2 7003 shift -0.026 54.0 *shift point*
3.75 55.52 211.5 7003 shift -0.026 54.0
4.18 55.38 231.9 7003 shift -0.025 54.0
4.25 57.60 252.6 5359 3 0.400 71.3
4.50 59.77 274.1 5560 3 0.391 70.9
4.53 60.03 276.8 5584 3 0.390 70.9 *60 MPH*
4.75 61.89 296.5 5758 3 0.383 70.6
5.00 63.95 319.5 5950 3 0.368 70.0
5.12 64.91 330.9 6039 3 0.361 69.7 *330 ft*
5.25 65.93 343.4 6133 3 0.353 69.4
5.50 67.82 367.9 6310 3 0.338 68.7
5.75 69.63 393.1 6478 3 0.324 68.2
6.00 71.37 419.0 6640 3 0.310 67.6
6.25 73.03 445.5 6794 3 0.297 67.1 *optimum shift pt*
6.50 74.62 472.6 6943 3 0.284 66.6
6.61 75.23 484.7 7000 shift -0.036 53.5 *shift point*
6.75 75.12 500.1 7000 shift -0.036 53.5
7.00 74.92 527.6 7000 shift -0.036 53.5
7.12 74.90 540.8 5345 4 0.295 67.0
7.25 75.74 555.2 5405 4 0.293 66.9
7.50 77.33 583.2 5519 4 0.289 66.7
7.60 77.96 594.6 5564 4 0.287 66.7 *1/8 mi (1)*
7.75 78.90 611.9 5631 4 0.284 66.6
8.00 80.45 641.1 5741 4 0.280 66.4
8.16 81.43 660.1 5811 4 0.277 66.3 *1/8 mi (2)*
8.25 81.97 670.9 5849 4 0.274 66.1
8.50 83.45 701.2 5955 4 0.267 65.8
8.75 84.89 732.1 6058 4 0.259 65.5
9.00 86.29 763.5 6158 4 0.252 65.3
9.25 87.66 795.4 6255 4 0.245 65.0
9.50 88.98 827.8 6350 4 0.239 64.7
9.75 90.27 860.7 6442 4 0.232 64.4
10.00 91.53 894.0 6532 4 0.226 64.2
10.25 92.75 927.8 6619 4 0.219 63.9
10.50 93.93 962.1 6703 4 0.213 63.7
10.75 95.09 996.7 6786 4 0.207 63.4
10.78 95.22 1000.9 6795 4 0.207 63.4 *1000 ft*
11.00 96.21 1031.8 6866 4 0.202 63.2
11.25 97.30 1067.3 6943 4 0.196 63.0
11.38 97.85 1085.9 6983 4 0.193 62.9 *optimum shift pt*
11.45 98.09 1096.0 7001 shift -0.053 52.8 *shift point*
11.50 98.04 1103.1 7001 shift -0.053 52.8
11.75 97.75 1139.0 7001 shift -0.053 52.9
11.96 97.56 1169.1 5007 5 0.195 62.9
12.00 97.73 1174.8 5016 5 0.195 62.9
12.25 98.79 1210.9 5071 5 0.193 62.8
12.50 99.85 1247.3 5125 5 0.191 62.8
12.54 100.01 1253.2 5133 5 0.191 62.7 *100 MPH*
12.55 100.06 1254.6 5136 5 0.190 62.7 *1/4 mi (1)*
12.75 100.89 1284.1 5178 5 0.189 62.7
13.00 101.92 1321.3 5231 5 0.187 62.6 *1/4 mi (2)*

Summary
0-60 mph: 4.71 Seconds
0-100 mph: 12.72 Seconds
60 ft: 1.55 @ 36.27
330 ft: 5.12 @ 64.91
1/8 mile: 8.16 @ 79.70 (81.43 actual)
1000 ft: 10.78 @ 95.22
1/4 mile: 13.00 @ 100.99 (101.92 actual)
Max Accel: 1.400 G
Air Density: 0.00231552 slug ft^3
Time Delta: 10.0 ms

reido

iTrader: (1)

I also have the rpm drops for each shift (roughly) assuming a 17" tire size for both gearsets based on mph with different redlines and shift points. I was just playing around at work.
I'm still not confident that I'll even keep my car.

I really only have 2 options: a factory replacement gearset and super expensive PPG dogset (oh and then there's the albins).
One is about a grand and the other 7 grand. The ratios on the dog set actually look great for street driving, but that's not really an option.


BTW, I'm using this to plan my build out. I don't plan to change it based on the stock motor. I'm just looking at changes in acceleration for various torque curves and rev ranges etc.. as well as some "spirited" blasts on the street.