Gears
08-24-2005, 10:38 AM
#141
Registered User
Originally Posted by jasonw,Aug 24 2005, 12:27 PM
Clue about what?
How you can calculate area under the curve with Physics but not Calculus?
How you can calculate area under the curve with Physics but not Calculus?
Well, using a simple equation like F=ma you can make into a=F/m. The unit of acceleration are m/s2, so you can multipy by time^2 and get the distance travled during that time of acceleration. But this assumes you can keep a constant force on the car, in other words the RPMS are costant and the weight of the car is constant and and force agianst the car are constant, other wise you are looking at an ugly differential equation I don't think anyone on that board (including myself) could even begin to solve.
You can determine acceleration using hp, but agian this will never work on a real car. A real car has changing amount of hp as RPMS change. You also need to have the mass of the car, it's not just a simple equation like that.
He really needs to take a class like applied physics. Calculus has nothing to do with his equations and crap, he needs and an advanced differential equation book to actually do it right.
You can determine acceleration using hp, but agian this will never work on a real car. A real car has changing amount of hp as RPMS change. You also need to have the mass of the car, it's not just a simple equation like that.
He really needs to take a class like applied physics. Calculus has nothing to do with his equations and crap, he needs and an advanced differential equation book to actually do it right.
08-24-2005, 10:40 AM
#142
Registered User
Originally Posted by jasonw,Aug 24 2005, 12:27 PM
Clue about what?
How you can calculate area under the curve with Physics but not Calculus?
How you can calculate area under the curve with Physics but not Calculus?
and as pointed out, we were both right. i, at least, had some proof on my side of it. rather than provide proof, you dodged the issue time and time again, until someone, in one post, explained it. which, IMO, makes it look like you had no idea what you were talking about in the first place.
08-24-2005, 10:44 AM
#143
I wish the original poster could have specified WHY he wanted "gears". This could have eliminated most, if not all of the "head banging" back and forth.
I have refrained from getting into this mainly because there is a diversity of what people do with this car and how "gears" relate to this. One camp is clearly thinking about "drag racing" (0 to 60 and 1/8 mile and 1/4 mile stuff) and the other camp is talking "road course" and the like. (And 'cause I like both "combatants".)
Wisconsin presents a valid argument because he mainly is talking about drag racing from a dead stop (or close to it). Mike presents a valid argument because he mainly is talking about using the car for road course duty. BOTH are justified in what they've presented here. The "Jason" element? Well, not sure what to think about that one.
Look here at Mike's quote:
If the original poster had stipulated that he's going drag racing, there would have never been an "argument" because the quote above would clearly indicate that Mike is also in agreement.
In a perfect world if you could "gear" any car so that it reaches its top speed at the precise moment it crosses the finish line in a drag race, you will also have the perfect setup because you can't make the car any quicker by gearing alone. Please understand the difference between "quicker" and "faster". In a road course situation, things get a little more complicated and Mike has also presented good information as to why.
I have refrained from getting into this mainly because there is a diversity of what people do with this car and how "gears" relate to this. One camp is clearly thinking about "drag racing" (0 to 60 and 1/8 mile and 1/4 mile stuff) and the other camp is talking "road course" and the like. (And 'cause I like both "combatants".)
Wisconsin presents a valid argument because he mainly is talking about drag racing from a dead stop (or close to it). Mike presents a valid argument because he mainly is talking about using the car for road course duty. BOTH are justified in what they've presented here. The "Jason" element? Well, not sure what to think about that one.
Look here at Mike's quote:
Almost all of the advantage is in first gear. That's gonna make a difference for drag racing, because once you get that advantage you keep it.
In a perfect world if you could "gear" any car so that it reaches its top speed at the precise moment it crosses the finish line in a drag race, you will also have the perfect setup because you can't make the car any quicker by gearing alone. Please understand the difference between "quicker" and "faster". In a road course situation, things get a little more complicated and Mike has also presented good information as to why.
08-24-2005, 10:55 AM
#145
Registered User
Originally Posted by Wisconsin S2k,Aug 24 2005, 11:20 AM
ok so power = horsepower?
so
power = Force * Velocity. is this correct?
so is the force continued to only be determined at a given rpm? in other words, i'm confused. if force goes up, and power goes up (as when a car first accelerates), what happens to velocity?
if velocity and force are both increasing, wouldn't that cause a dramatic upward curve in horsepower?
so
power = Force * Velocity. is this correct?
so is the force continued to only be determined at a given rpm? in other words, i'm confused. if force goes up, and power goes up (as when a car first accelerates), what happens to velocity?
if velocity and force are both increasing, wouldn't that cause a dramatic upward curve in horsepower?
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.
08-24-2005, 11:09 AM
#149
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Originally Posted by mikegarrison,Aug 24 2005, 10:55 AM
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.
Good pointBut the advantage is even better in that you don't drop as far with the 4.57 gear as the OEM, so you're even closer to the peak point every time you shift, hence normally faster (neglecting shifting). There are two bad things to the 4.57 gear set, you will reach your top speed quicker, but your top speed is lowwer than with the OEM gear set, however I'm not sure if this is a factor with the S2000 or not. The other problem is that the range of "optimal RPMS" is smaller, which is good for drag racing, but bad for road courses as now you have to shift more often.
So yes, it's up to what the orginall poster wanted.
08-24-2005, 11:13 AM
#150
Registered User
Originally Posted by jasonw,Aug 24 2005, 12:53 PM
I just had no desire to go into another side debate when you aren't even able to see that area under curve is not always greater for the 4.57s even below 100!
i'll post video for you of the area which YOU indicate the stock S2000 should win. 40-94. you claim there is more area under the curve for the stock S2000.
and we'll switch drivers too.