Scenario:

You have Car A with 200awhp/200awtq and Car B with 200rwhp/200rwtq. They both have the same drivers (to avoid any realworld flukes) and they both weigh the exact same. They both take off down the track in a 1/4-mile.

1) Who will reach the end of the quarter mile "sooner"?

2) Who will have the higher trap speed?

Please explain your answers. Ignore all differences in friction (tires, etc..) with the exception of drivetrain. Both have identical transmissions and gear ratios, etc..only one is all-wheel drive and the other rear-wheel drive.

-M

 

Well, in real life, the RWD car will trap higher unless on slicks and the AWD car will get there sooner, but ince you said to ignore friction differences, then I don't know. Parasitic loss has already been accounted for with the WHP figures, so it comes down to weight and gearing, which are also the same.

 

So they'll both trap the same speed but will they still reach the line @ the same time to?

 

No, the AWD car should get there earlier, but that's again because of traction. I don't know how we can ignore traction, because that will affect trap speed.

 

who ever has the better grip. if the RWD car cant hook the power to the wheels, then it just wont git....more than likely the AWD car will have better grip in the begining, and may lose some time at the end due to drivetrain loss, gearing, etc....too many variables i think.

 

As I said, parasitic loss is already accounted for in the WHP figures (that's after the drivetrain loss), and he said gearing is the same. The AWD's trap speed would be lower due to getting to the finish line sooner and not yet having time to speed up as much, whereas the opposite would be true on the RWD (slower ET, higher MPH).

 

If you ignore all differences including friction in the tires, then they'd get there at the same time wouldn't they?

 

What about drag coeficients? I say you 2 just throw down, and report back. I dont feel like pulling out my slide rule and abbacus right now. I think what Warrtalon is good enough!

 

If you ignore friction differences as stated, then differences between AWD and RWD would be eliminated due to the fact that if we are ignoring friction differences we are ignoring traction differences.

 

yup, end of story...
friction is a cruicial factor when comparing awd and rwd

 

Good analysis guys, but I only said ignore friction difference with relation to tires on the pavement (ie. the ground is perfect, the tires are the same, etc..).


I think that I will agree with the AWD getting there sooner and the RWD trapping higher assuming everything else is the same because of the fact that AWD will not build up speed like the RWD car would.

But let's get a little deeper. The trap speed indicates the current velocity at that particular point. Suppose we wanted to find the average velocity throughout the entire trip down the quarter-mile. We would have to break up our times into intervals to approximate the overall velocity down the track. Which would have a higher overall average velocity? If Car A gets their sooner, wouldn't it have the higher average?

-M

 

Who cares? What's the point? We answered the real question already.

 

Take the integral of the velocity vs. time graph and you get distance traveled. Both graphs will have the same amount of area under their curves since they both travelled 1/4 mi. Since the AWD does the 1/4 mi quicker, it must have a higher average velocity in order to achieve the same "area under the curve" in the velocity vs. time graph in less time than the RWD.

 

I would think that each car would have a higher velocity at a different time depending on what kind of intervals you used. The AWD having a higher velocity off the line and the RWD having it on top end.

Then again I was never good in physics.

 

Very nice! You get a cookie!

-M