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Originally posted by colonelcrisp irrelevant comparison of the drag coefficients since the 911 requires a hell of a lot more down force thus increasing drag. drag isnt a huge factor in efficiency until you reach highway speeds.

That is all factored in though to the number that is assigned. So how is that even relevant? Or am I mistaken in this?

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Originally posted by colonelcrisp since trains require alot more power, it makes sense to use diesel electric (or in some cases, turbine electric) drive systems. the larger scale diesel generators are much more efficient than the smaller scale ones used in the prius for example. not to mention, you will notice that trains dont vary the rpm speed on their generators very much so they operate almost always at constant rpm for greatest efficiency.

This was something I did ask about earlier in the thread, as this is not something I have any practical understanding of.

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Originally posted by gehzumteufel That is all factored in though to the number that is assigned. So how is that even relevant? Or am I mistaken in this?

ok first to answer.... Basically the reason the comparisson of a supercar to a hybrid is not apples to apples is that a prius does not operate at speeds high enough to require the added down force to A: keep it from going airborne or B: maintain traction for high speed cornering. Generation of downforce requires the deflection of airflow, thus creating drag. also drag coefficient is dependent on velocity, so at which reference point were the drag coefficients calculated?

for example, a chevy tahoe has a lower drag coefficient than an lamborghini countach. while the chevy has lower drag coefficient, it also weighs a metric ton more than the lambo....

not to mention that drag coefficient is such a piss ant factor in the overall drag force.

Fd=1/2*rho(fluid density)*v^2*Cd*A

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This was something I did ask about earlier in the thread, as this is not something I have any practical understanding of.

the other factor to look at is trains operate at extreemly low grade (<1%) where roads range in grade up to 12% and beyond. which increases the load demand on your power system. (imagine pushing a large tire on a flat surface vs a 10% incline.

quote:

Originally posted by colonelcrisp ok first to answer.... Basically the reason the comparisson of a supercar to a hybrid is not apples to apples is that a prius does not operate at speeds high enough to require the added down force to A: keep it from going airborne or B: maintain traction for high speed cornering. Generation of downforce requires the deflection of airflow, thus creating drag. also drag coefficient is dependent on velocity, so at which reference point were the drag coefficients calculated? for example, a chevy tahoe has a lower drag coefficient than an lamborghini countach. while the chevy has lower drag coefficient, it also weighs a metric ton more than the lambo.... not to mention that drag coefficient is such a piss ant factor in the overall drag force. Fd=1/2*rho(fluid density)*v^2*Cd*A

Ahh well I wasn't aware. Thanks for the clarification!

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the other factor to look at is trains operate at extreemly low grade (<1%) where roads range in grade up to 12% and beyond. which increases the load demand on your power system. (imagine pushing a large tire on a flat surface vs a 10% incline.)

Yeah I get the grade thing. Although in a place like here, I would think that since we are on a mostly flat surface, this wouldn't be much of an issue.

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Originally posted by SteelWolf NYPD goes Hybrid Nissan Altima Hybrid LOLOLOLOLOLOLOL People act like thats a big deal. My 2002 Mercedes get 34. My Wife's 1997 Honda Accord V6 gets 32 MPG. I just don't see why Hybrids are so much better. My Benz gets great gas mileage, and its hella fun to drive... and doesn't look like a lunchbox on wheels. Hybrid = G H E Y

Yep, my '03 c230 Kompressor Hatch got 33-34 back in the day. Now it's around 29-30. Still not too shabby!

Now MB is talkin about bringing out revolutionary new 4 cyl with supercharger or turbos. Everything old is new again.

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Originally posted by gehzumteufel Yeah I get the grade thing. Although in a place like here, I would think that since we are on a mostly flat surface, this wouldn't be much of an issue.

you would be surprised even a 2% grade is hard to eyeball. roadways are never flat mainly due to drainage issues (water doesnt move so well on grades less than 1%) no to mention the traffic calming effect of rolling vertical curves. the unnofficial rule of thumb for transportation engineering is that if the road looks like a drag strip, it will operate as such. when we do roadway design we incorporate unnecessary horizontal and vertical curves to discourage excessive speeding.

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Originally posted by colonelcrisp you would be surprised even a 2% grade is hard to eyeball. roadways are never flat mainly due to drainage issues (water doesnt move so well on grades less than 1%) no to mention the traffic calming effect of rolling vertical curves. the unnofficial rule of thumb for transportation engineering is that if the road looks like a drag strip, it will operate as such. when we do roadway design we incorporate unnecessary horizontal and vertical curves to discourage excessive speeding.

I am sure that I wouldn't be able to eye a 2% grade unless I looked at it vertically across and it was level with my eyes. And since that will never happen, I am sure I will never see it. I was aware of the drainage things though how the roadways, at least here in the US, are usually in a very slight grade from center being highest to the edge being lowest to aid in this.

quote:

Originally posted by gehzumteufel I am sure that I wouldn't be able to eye a 2% grade unless I looked at it vertically across and it was level with my eyes. And since that will never happen, I am sure I will never see it. I was aware of the drainage things though how the roadways, at least here in the US, are usually in a very slight grade from center being highest to the edge being lowest to aid in this.

thats called the crown or crossfall of the road which, on tangent (per AAHSTO standard), is set at +/- 2% from CL (it changes on curves, aka superelevation, up to +8%) i was referring to the longitudinal road grades specifically in urbanized environments (curbs on both sides of the road)

once the water gets to the gutter line, there must be sufficient grade to move that water towards catch basins to get it off the roadway, otherwise a condition known as "bird bathing" occurs when the water cannot get off the road way fast enough. The water backs up at teh curb and forms huge puddles which cause major hydroplaning on vehicles which can be devestating especially when only one side of the car is planing and the other side retains traction. This can cause torque steer conditions (car violently pulls to the right) and bad things happen...

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Originally posted by colonelcrisp thats called the crown or crossfall of the road which, on tangent (per AAHSTO standard), is set at +/- 2% from CL (it changes on curves, aka superelevation, up to +8%) i was referring to the longitudinal road grades specifically in urbanized environments (curbs on both sides of the road) once the water gets to the gutter line, there must be sufficient grade to move that water towards catch basins to get it off the roadway, otherwise a condition known as "bird bathing" occurs when the water cannot get off the road way fast enough. The water backs up at teh curb and forms huge puddles which cause major hydroplaning on vehicles which can be devestating especially when only one side of the car is planing and the other side retains traction. This can cause torque steer conditions (car violently pulls to the right) and bad things happen...

Fuck dude, this shit pisses me off so much. It happens so often here when it rains...which incidentally isn't THAT often in Southern California. Just when it does, it is bad. And that shit scares me since I know first hand how fucked you are when you hit them.

So has anyone heard anything about the Chevy Volt or the Nissan LEAF? Apparently these are supposed to break the mold in Hybrid/Electric cars.

http://features.csmonitor.com/innov...rom-chevy-volt/

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Originally posted by ziptnf So has anyone heard anything about the Chevy Volt or the Nissan LEAF? Apparently these are supposed to break the mold in Hybrid/Electric cars. http://features.csmonitor.com/innov...rom-chevy-volt/

The Volt was mentioned earlier in this thread. The LEAF is new. I have been reading on it, but not sure what to say about it at this point.

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Originally posted by gehzumteufel The Volt was mentioned earlier in this thread. The LEAF is new. I have been reading on it, but not sure what to say about it at this point.

367mpg is pretty fucking righteous.

quote:

Originally posted by ziptnf 367mpg is pretty fucking righteous.

But the devil is in the details. I can say anything, it is about how they calculate that number. What factors change that number? We don't even know yet.

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