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nonhuman
 
Quote:
Originally Posted by LagPenguin
I'll go with the bandwagon on this one, #teen magazines, race engineers, and dyno techs can't be wrong. But hell, for the sake of argument I've got a dyno instructor at my school who has done nothing but dyno cars for the past 40 years, perhaps I'll bring this up to him.

These engineers/techs aren't wrong; however, they're never claiming that the dyno measures the torque at the wheel. Otherwise there would be no point in calculating the gearing/etc to determine the rwtq. Think about it.
Old 08-30-2004, 06:18 PM nonhuman is offline  
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Quote:
Originally Posted by nonhuman
Yes.
Your argument is retarded. Of course it's always the engine's torque being measured. The wheels don't produce any fucking power.

An engine dyno measures engine output at the flywheel. A chassic dyno measures engine output at the wheels after the driveline loss is taken in account. How many fucking times do I have to explain this to you? You can throw out physics and math formulas all you want but your arguing will not change the bottom line. A chassis dyno is made to measure an engine's output at the wheels after driveline loss.

You can't seem to accept that because you think that only those numbers on paper have any meaning. In the real world it doesn't always work as theory states.

edit: lol i thought you were demosh
Old 08-30-2004, 06:21 PM SemperFly is offline  
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LagPenguin
 
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Quote:
Originally Posted by nonhuman
These engineers/techs aren't wrong; however, they're never claiming that the dyno measures the torque at the wheel. Otherwise there would be no point in calculating the gearing/etc to determine the rwtq. Think about it.

You've made this whole silly argument easier to understand, but why even bother with this in the first place? Why would anyone care about the actual wheel torque?
Old 08-30-2004, 06:21 PM LagPenguin is offline  
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#183  

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if i take the torque of my car 425nm, and convert to horsepower, using torque=power^(revs/5250)
this gives my 120hp, but i know my car makes 270hp so this must mean that the weight of my wheels =100lbs for all 4, including the spare wheel, which is actually 5, so 5+4/rpm/5250=9/900x2.7, which gives me 270hp. now if the earths weight is 12000000000000000000000000000000 pounds, and it if it is 248160000 feet around the earth (47kmilesx5280ft)=then it means that the earth spins in a contra rotation around the sun at 10feet/sec^2 which means i get 425ft/lbs at the engine.

the problem is that my car actually makes about 250 rwtq, so to calculate that i have to do it completely differently
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Old 08-30-2004, 06:23 PM crshbndct is offline  
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SemperFly
 
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Originally Posted by LagPenguin
You've made this whole silly argument easier to understand, but why even bother with this in the first place? Why would anyone care about the actual wheel torque?
No one gives two shits because the reason people use chassis dynos is to know how much driveline loss they're incurring. It's not to measure the exact amount of torque that the tires are putting to the ground because that's pretty close to impossible to measure with current technology because of the innaccuracy of how a dyno works.
Old 08-30-2004, 06:23 PM SemperFly is offline  
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#185  

Why_Ask_Why
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Quote:
Originally Posted by nonhuman
Yes.

Gearing changes the amount of torque applied to the wheels. Think about it. If torque was always the same, then why wouldn't you always start from 5th gear?

rwtq isn't a measure of torque applied to the wheels; as demosh demonstrated, simple math shows that gearing changes torque. Instead, rwtq is a measure of torque the engine produces after drivetrain loss is factored in. If a dyno shows that an engine produces 200 ft/lb at 3000 rpm, where would you find that torque? Definitely not the wheels, since those are most likely not spinning at 3000rpm. The only thing spinning at 3000rpm is the crank and associated bits. Thus, it's engine torque that's being calculated.

Of course, demosh is a for nitpicking about this in the first place. But his argument still stands.

false logic...it's still wheel tq that is determined...you are assuming crank due to rpm #'s being involved...you are writing off the factoring of drivetrain loss in the end result which undeniably occurs
Old 08-30-2004, 06:25 PM Why_Ask_Why is offline  
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nonhuman
 
Quote:
Originally Posted by LagPenguin
You've made this whole silly argument easier to understand, but why even bother with this in the first place? Why would anyone care about the actual wheel torque?
Beats me.
Old 08-30-2004, 06:25 PM nonhuman is offline  
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nonhuman
 
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Originally Posted by why_ask_why
false logic...it's still wheel tq that is determined...you are assuming crank due to rpm #'s being involved...you are writing off the factoring of drivetrain loss in the end result which undeniably occurs
No I'm not... where did I say I was? Since engine torque is calculated from wheel torque, which incurs drivetrain loss, then obviously the calculated value for engine torque doesn't write off drivetrain loss.
Old 08-30-2004, 06:27 PM nonhuman is offline  
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LagPenguin
 
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Originally Posted by FlyNavy
No one gives two shits because the reason people use chassis dynos is to know how much driveline loss they're incurring. It's not to measure the exact amount of torque that the tires are putting to the ground because that's pretty close to impossible to measure with current technology because of the innaccuracy of how a dyno works.

I get this. Just seems silly to get this technical over a figure that no one cares about. When you ask a dude how much rwtq he has, you're expecting the normal figure. If he told me that 2500 I'd either slap him or walk away. So, what does everyone think of hub dynos?
Old 08-30-2004, 06:29 PM LagPenguin is offline  
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nonhuman
 
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Originally Posted by FlyNavy
Your argument is retarded. Of course it's always the engine's torque being measured. The wheels don't produce any fucking power.

An engine dyno measures engine output at the flywheel. A chassic dyno measures engine output at the wheels after the driveline loss is taken in account. How many fucking times do I have to explain this to you? You can throw out physics and math formulas all you want but your arguing will not change the bottom line. A chassis dyno is made to measure an engine's output at the wheels after driveline loss.

You can't seem to accept that because you think that only those numbers on paper have any meaning. In the real world it doesn't always work as theory states.

edit: lol i thought you were demosh
That's exactly what I'm saying; my point is just that the number the dyno spits out is engine torque, not wheel torque. That's all.

OK, let me make up an analogy here. Let's say you have a fan blade attached to a tachometer pointed at a headwind. You can obviously calculate the wind speed based on the rotational speed of the fan blades. So when someone uses this contraption and says there's a 30mph wind, that's called wind speed and not fan speed. Sure, it's based on fan speed, but the fact is that it's calculated to reflect the speed of the wind.
OK, I know this is a real example, but hopefully you get the idea. If engine torque is calculated from wheel torque, it's engine torque.
Old 08-30-2004, 06:35 PM nonhuman is offline  
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Originally Posted by nonhuman
That's exactly what I'm saying; my point is just that the number the dyno spits out is engine torque, not wheel torque. That's all.

OK, let me make up an analogy here. Let's say you have a fan blade attached to a tachometer pointed at a headwind. You can obviously calculate the wind speed based on the rotational speed of the fan blades. So when someone uses this contraption and says there's a 30mph wind, that's called wind speed and not fan speed. Sure, it's based on fan speed, but the fact is that it's calculated to reflect the speed of the wind.
OK, I know this is a real example, but hopefully you get the idea. If engine torque is calculated from wheel torque, it's engine torque.
Of course it's engine torque and not wheel torque. The wheels don't produce any torque, they merely transfer it.

The dyno spits out the torque at the wheel after driveline loss and adjusted for gearing. If you had a 1:1 transmission ratio and 1:1 read end and didn't enter in those calculations you'd come out with the same number. It wouldn't be identical because chassis dynos aren't perfectly accurate, but it'd be close. This is as close as anyone's gonna get.


The point is that demosh is a fucking tard for complaining about the term "wheel torque" when it's the phrase that's been used by the automotive industry for who knows how fucking long. He may want to throw out numbers and formulas that don't mean jack shit in real world because life never mimics theory perfectly, but the point is that him nitpicking about it is fucking stupid.

Old 08-30-2004, 06:41 PM SemperFly is offline  
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#191  

Why_Ask_Why
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Quote:
Originally Posted by nonhuman
That's exactly what I'm saying; my point is just that the number the dyno spits out is engine torque, not wheel torque. That's all.

OK, let me make up an analogy here. Let's say you have a fan blade attached to a tachometer pointed at a headwind. You can obviously calculate the wind speed based on the rotational speed of the fan blades. So when someone uses this contraption and says there's a 30mph wind, that's called wind speed and not fan speed. Sure, it's based on fan speed, but the fact is that it's calculated to reflect the speed of the wind.
OK, I know this is a real example, but hopefully you get the idea. If engine torque is calculated from wheel torque, it's engine torque.

if that fan blade was eating blacktop while propelling you forward it becomes a much more compelling number...and of COURSE crank is involved in wtq...power doesn't hit the wheels from thin air...that's a given

in the case of cars the reality is measuring from the wheels because it's the cheapest, most widely used method of measure...the crank does produce different numbers and that's where the differentiation lies
Old 08-30-2004, 06:41 PM Why_Ask_Why is offline  
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nonhuman
 
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Originally Posted by why_ask_why
if that fan blade was eating blacktop while propelling you forward it becomes a much more compelling number...and of COURSE crank is involved in wtq...power doesn't hit the wheels from thin air...that's a given

in the case of cars the reality is measuring from the wheels because it's the cheapest, most widely used method of measure...the crank does produce different numbers and that's where the differentiation lies
Exactly... are you trying to argue against me?

I guess it all boils down to semantics. We're all talking about the same fucking thing, just calling it different names.
Old 08-30-2004, 06:43 PM nonhuman is offline  
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Old 08-30-2004, 06:49 PM dooodoo brown is offline  
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#194  

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ok, so how about this

you put your car on the dyno, and usin its wheels on the dyno, whatever, it measures the real wheel torque (the number everyone was sayin was ungodly high). then, it uses the gear ratios to divid that number and get the actual engine torque, not the advertised (manufacturer advertised torque). but we just call that wheel torque, because its being measured from the wheels?
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Old 08-30-2004, 07:10 PM Colicious is offline  
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