Gears
#151
Registered User
Originally Posted by mikegarrison,Aug 24 2005, 12:55 PM
horsepower = units of power, just like pounds = units of force or ft-lb = units of torque
power = F * V, yes. You may recall that work or energy (same stuff) = F*X (where X is the distance over which the F is applied). Power is work/time. F*X/t = F*V.
In the equation HP = (Torque * rpm / constant) you see the same thing. F*X (foot pounds) * (1/t) (rev/min).
When a car first accelerates, and both velocity and force are increasing, there IS a dramtic increase in actual horsepower output from the engine. This is the HP curve you see on a dyno run. It goes up dramatically.
If you were to take the plot and multiply the force line by the mph value, you would see the result (power) start from zero and shoot up to a high value by the time the car had to shift to second. From then on it would stay pretty close to that initial peak value, dropping a bit when shifting and then ramping back up. Just like a dyno plot trac from about 6000 rpm to 9000.
However, the "invisible line" I was referring to is not the actual HP from the engine, it is the maximum HP that the engine can provide (about 240 in the case of the S2000). That is what limits the potential benefit of an gearing. The closer you can keep the engine to constantly putting out that peak HP, the more force you will have at any given velocity, and the faster you will accelerate.
Looking at the plot, the really big advantage of the shorter gearset is that it gives you better initial acceleration in first gear, and pushes you up close to the peak HP potential faster. So most of your gain is right off the line. But you get to keep that gain all the way until you rev out at 150.
So like I said, I hav a new understanding of why this is an attractive mod for drag racing. When I originally said it had very little effect, I was thinking only about the part of that plot where you are already up near your max HP, and the two lines sort of braid over each other. I had discounted the initial first gear accel because it's not important to me, without recognizing that it is very important in drag racing.
power = F * V, yes. You may recall that work or energy (same stuff) = F*X (where X is the distance over which the F is applied). Power is work/time. F*X/t = F*V.
In the equation HP = (Torque * rpm / constant) you see the same thing. F*X (foot pounds) * (1/t) (rev/min).
When a car first accelerates, and both velocity and force are increasing, there IS a dramtic increase in actual horsepower output from the engine. This is the HP curve you see on a dyno run. It goes up dramatically.
If you were to take the plot and multiply the force line by the mph value, you would see the result (power) start from zero and shoot up to a high value by the time the car had to shift to second. From then on it would stay pretty close to that initial peak value, dropping a bit when shifting and then ramping back up. Just like a dyno plot trac from about 6000 rpm to 9000.
However, the "invisible line" I was referring to is not the actual HP from the engine, it is the maximum HP that the engine can provide (about 240 in the case of the S2000). That is what limits the potential benefit of an gearing. The closer you can keep the engine to constantly putting out that peak HP, the more force you will have at any given velocity, and the faster you will accelerate.
Looking at the plot, the really big advantage of the shorter gearset is that it gives you better initial acceleration in first gear, and pushes you up close to the peak HP potential faster. So most of your gain is right off the line. But you get to keep that gain all the way until you rev out at 150.
So like I said, I hav a new understanding of why this is an attractive mod for drag racing. When I originally said it had very little effect, I was thinking only about the part of that plot where you are already up near your max HP, and the two lines sort of braid over each other. I had discounted the initial first gear accel because it's not important to me, without recognizing that it is very important in drag racing.
#152
Registered User
Originally Posted by jasonw,Aug 24 2005, 12:57 PM
I mainly had to point out the problem with statements like this:
Which goes beyound 1/4 mi & 0-60 races.
I can beat any stock S2000 from a stop or from any speed roll starting under 100mph.
and it actually changed due to people like mike and chris. you stopped participating in the thread a long time ago, and provided no information, nor anything that wasn't simply the equivalent of crossing your arms and going "nuh uh".
#153
Registered User
Another reason why people perceive the gears to be such a performance boost is in "real world" driving. Let's say the two cars are driving along at 40 mph in 3rd gear. The 4.10 car will be at 4000 rpm, the 4.57 car will be at what, 4300? Something like that.
They decide to make a pass.
The 4.57 is already higher in the power band AND has a bigger torque multiplier. So he's gonna pull away from the 4.10 car -- hard.
But if the 4.10 downshifts to second, the advantage disappears or maybe even goes the other way. However, most people (even S2000 owners) just aren't in the habit of downshifting to second at 40 mph. So the car with gears will definitely feel like it has more "real world" acceleration, even though the other car (if driven like it's on a racetrack) can actually pretty much match it.
They decide to make a pass.
The 4.57 is already higher in the power band AND has a bigger torque multiplier. So he's gonna pull away from the 4.10 car -- hard.
But if the 4.10 downshifts to second, the advantage disappears or maybe even goes the other way. However, most people (even S2000 owners) just aren't in the habit of downshifting to second at 40 mph. So the car with gears will definitely feel like it has more "real world" acceleration, even though the other car (if driven like it's on a racetrack) can actually pretty much match it.
#154
Registered User
Originally Posted by mikegarrison,Aug 24 2005, 01:25 PM
Another reason why people perceive the gears to be such a performance boost is in "real world" driving. Let's say the two cars are driving along at 40 mph in 3rd gear. The 4.10 car will be at 4000 rpm, the 4.57 car will be at what, 4300? Something like that.
They decide to make a pass.
The 4.57 is already higher in the power band AND has a bigger torque multiplier. So he's gonna pull away from the 4.10 car -- hard.
But if the 4.10 downshifts to second, the advantage disappears or maybe even goes the other way. However, most people (even S2000 owners) just aren't in the habit of downshifting to second at 40 mph. So the car with gears will definitely feel like it has more "real world" acceleration, even though the other car (if driven like it's on a racetrack) can actually pretty much match it.
They decide to make a pass.
The 4.57 is already higher in the power band AND has a bigger torque multiplier. So he's gonna pull away from the 4.10 car -- hard.
But if the 4.10 downshifts to second, the advantage disappears or maybe even goes the other way. However, most people (even S2000 owners) just aren't in the habit of downshifting to second at 40 mph. So the car with gears will definitely feel like it has more "real world" acceleration, even though the other car (if driven like it's on a racetrack) can actually pretty much match it.
so if both cars downshift to 2nd, the difference is actually even greater.
2nd gear at 40 puts the stock car at 5500rpm.
the geared car would be at 6200rpm.
let's look at it from say an 80mph roll.
the stock car would be in 3rd at 8000rpm.
the geared car would be in 4th at 7000rpm. here the stock car has an advatage, but it is very short lived. as soon as you hit 90, the stock car shifts (which will also cause it to lose a few tenths, considering the geared car does not have to shift at all) and falls back down to 6800rpm in 4th. while at 90, the geared car is at 7700rpm, at a very strong point in the power band.
so between the extra shift the stock car has, and the fact that it then falls prey to the geared car being in the "meat" of the power band, not to mention it once again faces a good amount of time with the disadvantage of the taller gearing.
#155
Registered User
Originally Posted by Wisconsin S2k,Aug 24 2005, 12:40 PM
except for the fact that at 40mph, the geared car can ALSO downshift to 2nd.
#156
Registered User
Originally Posted by mikegarrison,Aug 24 2005, 02:53 PM
But the 4.57 will have to shift back up before the pass is complete, while that may not be true of the 4.10 car. These things are all pretty even trades. The thing that is not even is the low RPM extra pulling power of the lower-geared car. Not usually a big deal on the track because you avoid low rpms, but a bigger deal in normal driving.
even if the race were to go to only 65, the geared car would still win.
#157
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Antoher quesiton for those that have the gears how many believe or have the yellow box in order for the speedometer and odometer to be correct or corrected...Also, where else can 4.77 gears be purchased other than ricks2k.com...No offense to ricks2k I was just curious because I saw a forum about people getting ripped off, but I wasn't sure...Thanks in advance!
#158
Registered User
i have the yellow box and DEFINITELY recommend getting it.
as for the 4.77 gears. ricks2k.com sells them for about $300. they are a Kia gear, and you can get them from a Kia dealership for $300-$350. IMO, go with ricks2k.
as for the 4.77 gears. ricks2k.com sells them for about $300. they are a Kia gear, and you can get them from a Kia dealership for $300-$350. IMO, go with ricks2k.
#160
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After the third page, I was just ...
I really do enjoy reading the calculations and Wisconsin S2K's "real world" experience concerning gears. I have been contemplating this mod for some time. Unfortunately, threads like this one keep putting that little doubt in my head. Should I or shouldn't I