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Old 02-17-2007, 04:38 PM   #1
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Old 02-17-2007, 04:41 PM   #2
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Second Part


Now before anything else is said, it is essential for you to understand what horsepower really is and where it comes from.
Horsepower is nothing but the measurement of torque and RPM. Here's the formula for horsepower

HP = (torque) * (RPM) / (5252)

With that said, lets think about a domestic v8. Yeah, they have lots of torque, but most of them can't rev over 6000. For demonstration purposes lets see how much 200ft/lbs at 4000rpm really is.

HP = (200) * (4000) / (5252)

HP = 152.32

Now 100 ft lbs at 8000 rpm.

HP = (100) * (8000) / (5252)

HP = 152.32

Notice that these HP numbers are the exact same. Naturally, the motor that only makes 100tq is going to significantly smaller in displacement. (probably about 1/2 the size) But All one would have to do is double the gear ratio and you would never know the difference! Honda makes it's power by using smaller high-revving motors. Because the redline is so high, the gearing is also numerically high and the gears are short. The b16 gears may end at the same mph as a 6000rpm redline VW for example, but if you were to give the 8000rpm honda those same ratios and wheel dimater those gears would be "tall" So many people look at the specs of hondas b16 and they see 113ft/lbs and 1.6 liters, and they complain it doesn't have any torque! This isn't really a valid argument, mainly because these people have no concept of how gearing and torque multiplication works. Yes the b16 may have a low number of torque, but where it doesn't have torque, it has gears that are designed to keep the RPMs higher. This gives the impression of "this motor sucks so much that I have to rev the piss out of it to move" But in reality it has completely different characteristics of your typical domestic v8. I guarantee you that if you put a b16 in your civic along with a b16 transmission, and that if you were to change the 8 on your tach to a 6 and the 4 to a 3, as to trick you of how fast the motor was revolving, every oblivious person would ride in your car and think that you had an h23 "torque monster" in your car.

With that said, I want to show you this image that I have created with MathGV for windows.

In this graph, I have two lines plotted.
The red line is Y = 130. This is the theoretical torque line on a dyno plot. Again, for demonstration purposes.
The blue line is Y = (130) * (X) / (5252) This is the horsepower formula with 130ft lbs of torque.
As you can see, there is more torque than horsepower up until after 5000. Because of the formula for horsepower, no matter what you're going to have the exact same amount of torque as horsepower at 5252rpm. Because of this, if your motor's redline is 5000rpms. There is no way that you will ever have more hp than torque unless you make power beyond 5252rpms. This also means that if you continue to make power (torque) beyond 5252RPM, that no matter what, you will have more horsepower than torque. This is concrete physical mathematical proof of this. No matter what this will never change. Bottom line, if you want horsepower, you need torque and high RPMS to get it. If you want to have more torque than horsepower, you can either stop making power beyond 5252 rpms, or you can let off the gas, or get a motor that doesn't rev beyond 5252rpm. If you want a lot more horsepower than torque, you better start reving beyond 5252 rpms.

Hopefully after analyzing this graph and reading what I've said, you now understand the value of keeping those RPMs up with your honda motor. The closer you can stay to redline, the faster your car will be. This is the value of close ratio gears. What I am about to share with you is something that dawned onto my crazy ADHD self when I was watching "The Bourne Identity" one night. I have never seen this on any of the transmission pages. It seems so simple, but it is something that I have never seen anywhere. I can only hope that it's something that will be covered in one of my future mechanical engineering classes. I don't know. For the longest time I was calculating the RPM drops of various transmissions. b16, gsr, ls, bmw e36, GM's t-56 (ls1 6speed), etc. But to do that I had to manually do the formulas. Find the mph of X gear ratio with Y axle ratio and Z wheel diameter at 6000rpm and compare it to all the other gears and blah blah blah. It is very time consuming and it sucks. I wished that there was a way to find out the RPM drops without having to do all that. But then I got it and man was I very very very excited. Check this out.

B16 transmission for example
1st - 3.250
2nd - 2.105
3rd - 1.458
4th - 1.107
5th - 0.848
final - 4.400

to simply calculate RPM drops:
gear ratio of the next gear / current gear ratio = rpm drop

2nd gear / 1st gear = 1st -> 2nd RPM DROP %
3rd gear / 2nd gear = 2nd -> 3rd RPM DROP %

2.105 / 3.250 = 0.64769 or 64.769%
1.458 / 2.105 = 0.69264 or 69.264%
1.107 / 1.458 = 0.75926 or 75.926%
0.848 / 1.107 = 0.76603 or 76.603%

So I take my b16 up to 8000rpms and then shift into 2nd. 8000 * 0.64769 = 5181.52

after shifting from ___ RPMs drop to ____
1st -> 2nd = 5181.52 rpm
2nd -> 3rd = 5541.12 rpm
3rd -> 4th = 6074.08 rpm
4th -> 5th = 6128.24 rpm

Because of these ratios and the relation they have to each other (RPM Drops) Unless you're making LOTS of power (over 250whp) you want to use these ratios you're trying to optimize your quarter mile times. The reason is that they are the closest together RPM wise. Yeah, you may be making 500whp on your turbo civic, but you may not hit 500whp until you're at the very end of RPM range. This comes out to "........500WHPyeahhhhhh....shift............. .... ..500WHPwoohoo!!!" Like I said earlier, you have 3 OEM final drives to choose from, 4.266, 4.400, and 4.785.

If you have a high hp turbo honda, you (like most people) have traction issues. This is because you don't have enough traction. In the quest of acquiring more you have ONLY two options.
1. put less torque to your tires
2. get better tires.
There are different ways to put less power to the wheels. You can either lower your boost level, or use gearing to reduce your torque. If you use the ls transmission your gears are going to be further apart and your RPM drops are going to be greater. This is going to hurt your acceleration Inheritently this is an issue that many people are trying to overcome, because of this, I have hypothesized and come up with a great hybrid theory (loads linkin park playlist in winamp).

1st = 3.23
2nd = 1.9
3rd = 1.458
4th = 1.107
5th = whatever you want (:

utilizing the gsr/ls 1st and 2nd gear along with b16 3rd and 4th gears. The reason being, 1st gear is the same no matter what, so there's no choice, the taller 2nd gear because traction is usually such an issue in 2nd gear that you might as well have it carry you further into 3rd anyways. b16 3rd and 4th gear ratios, and whatever 5th. This results in the closest OEM 2nd/3rd/4th gear ratios. (lowest rpm drops) Most people try to avoid shifting into 5th anyways, so if you'd like, you can use a taller LS or GSR 5th gear. it's up to you.

In typing this page, I am covering mostly the theory to show YOU what I have learned and attempt to explain what's really going on. At this point I just don't feel like pluggin all the numbers in for you. If you want to run 25" slicks with a 4.4 final drive and you want to know what mph you'll be at when you redline at 8000 rpms, well put it in the formula.


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Old 02-26-2013, 11:30 PM   #3
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