HP Forumula
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You don't read well, huh.
"MPH" is constant; he defined it as your trap speed. Of course you trap differently every time but given all else being equal, trap speed is constant.
This formula is a nice tool for estimating things I guess. If you do a dyno run, you can estimate your trap speed or if you race and don't bother with a dyno you can estimate your HP numbers (I guess it's good for cars with a bunch of bolt ons.) In a sense, this is more accurate than some dynos since trap speed is a direct measurement of your car's power.
"MPH" is constant; he defined it as your trap speed. Of course you trap differently every time but given all else being equal, trap speed is constant.
This formula is a nice tool for estimating things I guess. If you do a dyno run, you can estimate your trap speed or if you race and don't bother with a dyno you can estimate your HP numbers (I guess it's good for cars with a bunch of bolt ons.) In a sense, this is more accurate than some dynos since trap speed is a direct measurement of your car's power.
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From: Team SOLO
still rediculous. driver ability also contributes. this whole thread is a waste, this is not a good estimating thing at all. get a dyno if you want accurate numbers not this equation that can't factor in anything.
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Well duh.
Before anything... this thread wouldn't be the first waste of space on SL but it's minutely more academic than most.
Driver ability, sure. You know what that means? If you're not trapping as high as you think, you're only using a certain amount of power. Or if you dyno a certain amount of power and you're trapping 15% slower than you expect, there's something wrong. If you don't know what trap speed to expect you might not ever know. Equations aren't meant to be an end. They're tools for interpretation. Gives you a baseline to begin an investigation. You're an idiot for blindly dismissing an equation.
Btw, dynos use equations as well as they can't even measure power directly but have to derive the number from torque; trap speed is a direct measurement of power.
And before anyone says anything about experience, obviously experience is a thousand equations. But experience is nothing without context.
I hate it when people think they know it all.
Before anything... this thread wouldn't be the first waste of space on SL but it's minutely more academic than most.
Driver ability, sure. You know what that means? If you're not trapping as high as you think, you're only using a certain amount of power. Or if you dyno a certain amount of power and you're trapping 15% slower than you expect, there's something wrong. If you don't know what trap speed to expect you might not ever know. Equations aren't meant to be an end. They're tools for interpretation. Gives you a baseline to begin an investigation. You're an idiot for blindly dismissing an equation.
Btw, dynos use equations as well as they can't even measure power directly but have to derive the number from torque; trap speed is a direct measurement of power.
And before anyone says anything about experience, obviously experience is a thousand equations. But experience is nothing without context.
I hate it when people think they know it all.
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From: Team SOLO
believe me, i'm a mechanical engineer i deal with power equations all day. using an equation with speed and weight does not mean power at all. yes the units may match up and it may make sense but its not a good equation. torque at the wheels translates into power which is much more accurate than speed.
what about wheels spinning, what about all that other stuff, theres PLENTY of other factors than just the speed and weight of the vehicle to contribute to power. this is not a good equation and will not get you anything close to what can be at the wheels / crank
what about wheels spinning, what about all that other stuff, theres PLENTY of other factors than just the speed and weight of the vehicle to contribute to power. this is not a good equation and will not get you anything close to what can be at the wheels / crank
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I could care less what you do or study. I know doctors who forget their biochemistry and English majors who do civil engineering.
It's definitely true that there are a multitude of factors unaccounted for. For instance, gearing! Some built small block Chevys do 10's but still trap under 100 mph. Obviously if it's "built" and it's probably making a hell of a lot more power than a tC which implies that equation isn't true.
But like I said, equations aren't ends. They're mediums for exploration.
So you pull out one of your other power equations. If it works, it works! Chances are, it's more complicated than the one the OP offered which, like you said, is pretty rudimentary. But if works, then what's the point of using a different one? And then what does it mean, when the equation works? No matter what happens, once you put in the numbers and crunch something out, it'll tell you something. What you make of it is what's important.
Finally, if someone was very serious, one would have taken the car to the dyno already. Like I said, it'd be a nice little tool for someone with bolt-ons, where a dyno run may seem gratuitous. I'll concede that dyno runs are more accurate (short of dynojets that measure acceleration, of course) but sometimes such accuracy isn't needed. Again, like I said, it's foolhardy to blindly dismiss equations. It's all time and place.
Anyway, earnest non-rhetorical question: how is wheel spin a factor in power?
It's definitely true that there are a multitude of factors unaccounted for. For instance, gearing! Some built small block Chevys do 10's but still trap under 100 mph. Obviously if it's "built" and it's probably making a hell of a lot more power than a tC which implies that equation isn't true.
But like I said, equations aren't ends. They're mediums for exploration.
So you pull out one of your other power equations. If it works, it works! Chances are, it's more complicated than the one the OP offered which, like you said, is pretty rudimentary. But if works, then what's the point of using a different one? And then what does it mean, when the equation works? No matter what happens, once you put in the numbers and crunch something out, it'll tell you something. What you make of it is what's important.
Finally, if someone was very serious, one would have taken the car to the dyno already. Like I said, it'd be a nice little tool for someone with bolt-ons, where a dyno run may seem gratuitous. I'll concede that dyno runs are more accurate (short of dynojets that measure acceleration, of course) but sometimes such accuracy isn't needed. Again, like I said, it's foolhardy to blindly dismiss equations. It's all time and place.
Anyway, earnest non-rhetorical question: how is wheel spin a factor in power?
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From: Team SOLO
you obviously don't go to the track often.
if you have a ton of power you can't get traction and thus your trap speed is lower. so you may have a lot more power than this formula suggests but its irrelevant anyway.
my point is this equation does nothing, maybe a guideline but the error on it is probably close to 25-35% (just by numbers i've put in). It was a rediculous thread, if you want to know your horsepower do it properly and go to a dyno. I could provide many more equations but like you said more complicated, and thus more accurate. i'm done here. this threads a waste
if you have a ton of power you can't get traction and thus your trap speed is lower. so you may have a lot more power than this formula suggests but its irrelevant anyway.
my point is this equation does nothing, maybe a guideline but the error on it is probably close to 25-35% (just by numbers i've put in). It was a rediculous thread, if you want to know your horsepower do it properly and go to a dyno. I could provide many more equations but like you said more complicated, and thus more accurate. i'm done here. this threads a waste
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Lol. Nebsters not being ignorant. He's got a point and I got mine. He's saying the formula isn't useful for accuracy and I'm saying it's useful for rough estimates.
Crayola, you'd be the ignoramus if you thought this equation would solve all our problems. I'm not on your side and nor am I "against" nebster. I'm BORED.
And that thing about wheel spin: just how much wheel spin are we talking about? Usually a car will do roughly the same trap speeds with varying 60 ft times. Obviously if your tires never hook up you'll never get the most out of your car (and then of course, using that equation you'd get a decent idea of how much power you're losing due to loss of traction.) But even on bad launches, you tend to trap roughly the same. There are plenty of examples when people get better trap speeds when their 60 ft times are worse. That says to me that wheel spin doesn't affect power.
Crayola, you'd be the ignoramus if you thought this equation would solve all our problems. I'm not on your side and nor am I "against" nebster. I'm BORED.
And that thing about wheel spin: just how much wheel spin are we talking about? Usually a car will do roughly the same trap speeds with varying 60 ft times. Obviously if your tires never hook up you'll never get the most out of your car (and then of course, using that equation you'd get a decent idea of how much power you're losing due to loss of traction.) But even on bad launches, you tend to trap roughly the same. There are plenty of examples when people get better trap speeds when their 60 ft times are worse. That says to me that wheel spin doesn't affect power.