Below are 3 tables.

The first table represents a C5 Corvette with a MN6 transmission in 4th gear weighing 3400 Pounds (includes driver), using the factory 3.42 differential.

The second table represents a C5 Corvette with a MN6 transmission in 4th gear weighing 3400 Pounds (includes driver), using a 4.10 differential.

The third table represents a C5 Corvette with a MN6 transmission in 4th gear weighing 3400 Pounds (includes driver), using the factory 3.42 differential. Except that increase HP/TQ output has been increased 20%.

Note within a RPM range, that increasing from 3.42 to 4.10 ratio, is a 20% increase in thrust, and is a linear relationship in an equivalent amount of engine output, without changing from 3.42 to 4.10.

RWHP - Rear Wheel HP
RWTQ - Rear Wheel TQ
FWHP - Flywheel HP
FWTQ - Flywheel TQ
DWTQ - Drive Wheel TQ (Torque Multiplication)

Math used:
Drive wheel torque = flywheel torque x gear ratio x final drive ratio x 0.85

Wheel thrust = drive wheel torque / rolling radius (in feet)

And G Force is derived:
g = wheel thrust / weight

<BLOCKQUOTE>code:<HR><PRE>3.42
RPM RWHP RWTQ FWHP FWTQ DWTQ Thrust G-Force
3500 210.45 315.80 247.59 371.53 1080.04 974.76 0.29
3600 216.88 316.40 255.15 372.24 1082.09 976.61 0.29
3700 224.03 318.00 263.56 374.12 1087.56 981.55 0.29
3800 230.66 318.80 271.37 375.06 1090.30 984.02 0.29
3900 237.18 319.40 279.03 375.76 1092.35 985.87 0.29
4000 244.63 321.20 287.80 377.88 1098.50 991.43 0.29
4100 252.23 323.10 296.74 380.12 1105.00 997.29 0.29
4200 259.42 324.40 305.20 381.65 1109.45 1001.31 0.29
4300 264.62 323.20 311.31 380.24 1105.34 997.60 0.29
4400 268.09 320.00 315.40 376.47 1094.40 987.73 0.29
4500 273.50 319.20 321.76 375.53 1091.66 985.26 0.29
4600 279.14 318.70 328.39 374.94 1089.95 983.71 0.29
4700 285.02 318.50 335.32 374.71 1089.27 983.10 0.29
4800 290.18 317.50 341.38 373.53 1085.85 980.01 0.29
4900 297.81 319.20 350.36 375.53 1091.66 985.26 0.29
5000 302.17 317.40 355.49 373.41 1085.51 979.70 0.29
5100 307.34 316.50 361.58 372.35 1082.43 976.92 0.29
5200 311.09 314.20 365.99 369.65 1074.56 969.82 0.29
5300 314.95 312.10 370.53 367.18 1067.38 963.34 0.28
5400 315.14 306.50 370.75 360.59 1048.23 946.06 0.28
5500 316.05 301.80 371.82 355.06 1032.16 931.55 0.27
5600 311.99 292.60 367.04 344.24 1000.69 903.15 0.27
5700 312.68 288.10 367.85 338.94 985.30 889.26 0.26
5800 312.86 283.30 368.07 333.29 968.89 874.45 0.26
5900 314.10 279.60 369.53 328.94 956.23 863.03 0.25
6000 313.25 274.20 368.53 322.59 937.76 846.36 0.25
6100 313.36 269.80 368.66 317.41 922.72 832.78 0.24


4.10
RPM RWHP RWTQ FWHP FWTQ DWTQ Thrust G-Force
3500 210.45 315.80 247.59 371.53 1294.78 1168.57 0.34
3600 216.88 316.40 255.15 372.24 1297.24 1170.79 0.34
3700 224.03 318.00 263.56 374.12 1303.80 1176.71 0.35
3800 230.66 318.80 271.37 375.06 1307.08 1179.68 0.35
3900 237.18 319.40 279.03 375.76 1309.54 1181.90 0.35
4000 244.63 321.20 287.80 377.88 1316.92 1188.56 0.35
4100 252.23 323.10 296.74 380.12 1324.71 1195.59 0.35
4200 259.42 324.40 305.20 381.65 1330.04 1200.40 0.35
4300 264.62 323.20 311.31 380.24 1325.12 1195.96 0.35
4400 268.09 320.00 315.40 376.47 1312.00 1184.12 0.35
4500 273.50 319.20 321.76 375.53 1308.72 1181.16 0.35
4600 279.14 318.70 328.39 374.94 1306.67 1179.31 0.35
4700 285.02 318.50 335.32 374.71 1305.85 1178.56 0.35
4800 290.18 317.50 341.38 373.53 1301.75 1174.86 0.35
4900 297.81 319.20 350.36 375.53 1308.72 1181.16 0.35
5000 302.17 317.40 355.49 373.41 1301.34 1174.49 0.35
5100 307.34 316.50 361.58 372.35 1297.65 1171.16 0.34
5200 311.09 314.20 365.99 369.65 1288.22 1162.65 0.34
5300 314.95 312.10 370.53 367.18 1279.61 1154.88 0.34
5400 315.14 306.50 370.75 360.59 1256.65 1134.16 0.33
5500 316.05 301.80 371.82 355.06 1237.38 1116.77 0.33
5600 311.99 292.60 367.04 344.24 1199.66 1082.73 0.32
5700 312.68 288.10 367.85 338.94 1181.21 1066.07 0.31
5800 312.86 283.30 368.07 333.29 1161.53 1048.31 0.31
5900 314.10 279.60 369.53 328.94 1146.36 1034.62 0.30
6000 313.25 274.20 368.53 322.59 1124.22 1014.64 0.30
6100 313.36 269.80 368.66 317.41 1106.18 998.36 0.29


3.42 gear, and adding a 20% Increase in Engine TQ gets:
RPM RWHP RWTQ FWHP FWTQ DWTQ Thrust G-Force
3500 252.54 378.96 297.11 445.84 1296.04 1169.71 0.34
3600 260.25 379.68 306.18 446.68 1298.51 1171.94 0.34
3700 268.83 381.60 316.28 448.94 1305.07 1177.86 0.35
3800 276.80 382.56 325.64 450.07 1308.36 1180.83 0.35
3900 284.61 383.28 334.84 450.92 1310.82 1183.05 0.35
4000 293.56 385.44 345.36 453.46 1318.20 1189.72 0.35
4100 302.68 387.72 356.09 456.14 1326.00 1196.75 0.35
4200 311.31 389.28 366.24 457.98 1331.34 1201.57 0.35
4300 317.54 387.84 373.57 456.28 1326.41 1197.12 0.35
4400 321.71 384.00 378.48 451.76 1313.28 1185.27 0.35
4500 328.19 383.04 386.11 450.64 1310.00 1182.31 0.35
4600 334.96 382.44 394.07 449.93 1307.94 1180.46 0.35
4700 342.03 382.20 402.39 449.65 1307.12 1179.71 0.35
4800 348.21 381.00 409.66 448.24 1303.02 1176.01 0.35
4900 357.37 383.04 420.43 450.64 1310.00 1182.31 0.35
5000 362.60 380.88 426.59 448.09 1302.61 1175.64 0.35
5100 368.81 379.80 433.89 446.82 1298.92 1172.31 0.34
5200 373.31 377.04 439.18 443.58 1289.48 1163.79 0.34
5300 377.94 374.52 444.64 440.61 1280.86 1156.01 0.34
5400 378.16 367.80 444.90 432.71 1257.88 1135.27 0.33
5500 379.26 362.16 446.19 426.07 1238.59 1117.86 0.33
5600 374.39 351.12 440.45 413.08 1200.83 1083.78 0.32
5700 375.21 345.72 441.42 406.73 1182.36 1067.11 0.31
5800 374.11 338.76 440.13 398.54 1158.56 1045.63 0.31
5900 376.92 335.52 443.43 394.73 1147.48 1035.63 0.30
6000 375.90 329.04 442.24 387.11 1125.32 1015.63 0.30
6100 376.04 323.76 442.39 380.89 1107.26 999.33 0.29</PRE>[/QUOTE]





[Modified by kewlbrz, 5:04 PM 12/3/2002]

 

Does this mean when you change from 3.42 gears to 4.10 gears it is equivilant to almost 70 hp increase acceleration? :confused:

 

Thats what the math shows.

Except with changing gears, you give up top speed in each gear, and must shift more aggressivly.

 

What the math shows is there is a direct correlation of gear ratio to thrust G-force, ie, there is a 19.88% difference in gear ratio (3.42 to 4.1) and that correlates to the performance of 19.88% more horsepower. This sounds reasonable. Now add a different torque converter that keeps the car in the max power band longer, and you can increase performance even more. So for the price of a gear set and torque converter, you can have the performance of a supercharged car. Sounds like the most bang for the buck.

 

Are you guys really serious?

If you are, then I'm really concerned at the intelligence level of current C5 owner! :sad:

I don't know if I should :U or :lurk:

Stop the madness, you DON'T gain power!

You gear a car to maximize the time spent in each gear at peak power so that you cover the same distance in the least amount of time with the power you do have!

This is the single most important concept guys! You want to emphasize the power in the rpm band where the engine spends most of its time while covering a specific distance.

So, if you are going down the quarter mile and you spend 60% of your total time in the 4000 - 5000rpm band and you make most of your power between the 5000rpm - 6000rpm range, then you can see where you are leaving power on the table. You re gear the car so that more "time" is spent in the 5000rpm - 6000rpm range thus using the most of the power you are making and not wasting "time" in an RPM band where you are making less power to the wheels.


This is also the reason why there are so many "dyno queens" out there. They make HUGE numbers on the dyno, yet run very poorly at the track. Consider that most aftermarket cams bump power even further up the RPM band, 6000-6500rpm and take a little away at the lower end (rpm) and you can quickly see how if you don't adjust your shift points, gearing, etc you now have a car with gobs of power and hardly any faster.

 

Darn, I was trying to get me a custom set of 5.57 gears made so I could get in the 9's - you mean its not true :(

 

"So for the price of a gear set and torque converter, you can have the performance of a supercharged car."

Sure and you also quickly see the tailights of that supercharged car also. With the money you just lost on that race, you should of gotten the supercharger in the first place. ;)

 

KP - It's your fault in the first place... quit stirring the pot! :D

Although a nice set of 5.57's would make for a nice highway ride for the wife. ;) buzzzzzzzzzz........ buzzzzzzzzz...... buzzzzzzzz......

 

H82BFST, first of all you need to take it down a few notches.

I think most get it that you can have tooo much gear and be detrimental. In fact I pointed that fact out in the other post going regarding 4.10's here, and that gearing is highly dependend on combining it properly to your engines powerband. Feel free to click back and check it out.

Since everyone is having so much success and accelleration with thier 4.10's in the C5, and asking how much HP it would take to equal that kind of increase, I simply used some math to point out a comparison of 3.42 gears and 4.10.s Not the ludicrous suggestion of 5.57's that kp childishly eluded too.

The fact of the matter, is that you do in fact gain thrust with steeper gearing (obviosuly to a point), and obviously you do not gain power.





[Modified by kewlbrz, 5:32 PM 12/3/2002]

 

Not a math wiz here but I get the point...I have half a ounce of common sense...well, at least I think I do.:)

Thanks for the work Shawn!

RG

 

You can have the same 'thrust' by just leaving the car in 3rd :)
I hear they are coming out with the Z06.5 next year - its going to have 4.10 gears and 500hp with the same engine :)

Seriously though, Yes the car will accelerate faster but will cover less distance and in some cases will be better in the 1/4 and thats not what I am saying.

Lets see, has anyone run with a stock C5 + 4.10s anywhere near what stock '03 Z06 with 3.42s has?

My comment is no more ridiculus then gaining a 'virtual' 70rwhp from a gear swap :)

 

I think you may have made a mistake when calculating the Thrust column - it seems as though you've multiplied instead of dividing (by a pretty large tire radius, too!). I wish your math was right, though, because it clearly indicates that I'd be able to climb trees with my car if I only had a set of 4.10's :jester

Your point is not lost over this detail, however. Your tables very clearly illustrate the benefits of proper gearing and how lower gearing multiplies available torque.

 

If ya' haven't tried the 4.10s you wouldn't understand ;) :thumbs:

 

Oh crap, not another one of these threads

I'm just a sales & marketing guy. I'm pretty sure I can sell this concept, but I don't understand a word of it :crazy:

 

I doubled checked at it looks right. Lets run through a row:

<BLOCKQUOTE>code:<HR><PRE>RPM RWHP RWTQ FWHP FWTQ DWTQ Thrust G-Force
3500 210.45 315.80 247.59 371.53 1080.04 3050.95 0.90</PRE>[/QUOTE]

Drive wheel torque = flywheel torque x gear ratio x final drive ratio x 0.85

371.53 x 1.0(4th gear) x 3.42 x 0.85 = 1080.04

Wheel thrust = drive wheel torque / rolling radius (in feet)

275/35-18 tire = 26.7 circumfrence

26.7 = 4.248 in radius

4.248 converting to feet = .354 feet


1080.04 / .354 = 3050 Thrust

ooops now I see the error.

I accidently took 26.7 as the circumfrence instead of the diameter.

my bad.

radius should be 13.3 inches

= 1.108 feet instead of .354

I've recalculated and reposted the proper thrust calculation. The numbers change, but the 20% relationship is still equal.





[Modified by kewlbrz, 5:03 PM 12/3/2002]

 

It's more useful to see thrust vs. speed than thrust vs rpm, because of course with a lower gear you get more thrust, but you also have to upshift sooner. When the lower geared car has to upshift, the higher geared car will be in the previous tranny gear, and will have a gearing advantage.

The slightly taller lines are for a car with 3.73 gears, the shorter ones (but stretched out laterally) are for the same car with 3.42 gears. It's based off my own dyno data.

Here's a plot I did before to illustrate this:


screwy new forum software shrunk my picture! Here's a link: http://temp.corvetteforum.net/c5/miles//thrust.gif
:cheers:


[Modified by Miles in Michigan, 5:00 PM 12/3/2002]

 

Here's a plot of thrust vs speed for all 6 gears of a MN6 with 3.42, versus with a hypothetical 5.0 differential ratio. Notice that while the 5.0 has much more thrust in 1st gear, after that, nearly every gear has the same thrust as a 3.42 car does in one tranny gear lower. Switching to 5.0 from 3.42 is effectively the same as if you could keep the differential the same, remove 6th gear, and add a new gear before 1st with a ratio of about 3.89.

Crusing at highway speeds in 6th gear with a 5.0 differential is almost identical to cruising at the same speed with a 3.42, in 5th gear.
http://temp.corvetteforum.net/c5/miles//thrust2.gif

 

Great info, thanks Miles.

 

Kewlbrz-Great post,as always! Thanks !


Miles- excellent graphs! Thanks!

:yesnod: :yesnod: :yesnod: :yesnod: :yesnod: :thumbs: :cheers:

 

My car got a new best at the 1/4 mile track with my 4.10 gears and the car is much more fun to 'thrust' around town with now. :D :cheers: