i can't believe we're still debating this.

seriously, why don't you just go to the back of a road and track magazine and look at the acceleration, weight, torque and horsepower of various cars....that's real world data.

 

 

I don't understand. Did you not understand what I ment when I said that "by having a higher redline you can hold each gear longer. thus, you can run shorter gearing."? I not only explained this but I mathmatically proved my point. It doesn't matter how many gears you want to use. For every gear ratio in CarA you can have a shorter gear ratio in CarB to match CarA's acceleration. In the end both 200 hp cars will accelerate at the same rate.

 

HP vs. Torque

http://www.slowgt.com/Tut.htm

 

I can't believe this thread is still alive.

 

I know this is an old topic but I believe I have very good pictures that will make this VERY clear to everyone, so I'm going to reply and bump this one.

When I got my 2003 s2000 I also purchased a GtechProCompetition.
I always wanted something that could do what the gtech does because I knew with it I could easily clear up the HP vs. TQ questions I had as well as log very useful data for me.

Here is a Gtech Dyno run in second gear when the car only had a few thousand miles.



Now note that you are driving the car when you make a dyno with the gtech so it accounts for everything. This is true RWHP for my car in second gear. At 64 MPH we are using about 11HP just for drag. If you figure ~30HP is lost to the transmission than this would be about a 200HP run, a bit low for a 240HP car. I suspect I had the weight set low.

Note the shape of the torque curve.
The gtech records accelerations very accurately over time.
So I can also graph the acceleration curve.

Which curve do you think will look like the acceleration? HP or TQ?



Here it is! Note that it is normalized I've scaled the graphs to match their peaks to the top. We don't care about the amount of acceleration or the amount of any of these graphs. For our purposes all we want to look at is the shapes of the curves.

The torque curve is IDENTICAL to the acceleration curve. The HP curve is a completely different shape!!!

Just as chenpin said:
When you get pushed back in your seat it's from a force and torque is going to relate to that feeling of acceleration 1 to 1!

I think chenpin's post was the most useful. He articulated everything very clearly and covered pretty much all bases.

I wish I had read his post before writing the long post I did. But after reading enough of the posts I figure the only thing to add were the images really so this has been cut down to size.

Thanks,

-mikey

By the way I just put money down on a 2005 Z51 Corvette. So I will soon be selling my S2000. You guys have first crack at it. PM me if interested.

I'll post details in an appropriate place.

 

Here, read this:
http://www.stanford.edu/~voloshin/lhowwhy.html

 

That physics student is assuming that you started to accelerate at maximum powerband only.

That's why he's always assuming that you are at peak power at launch and dropping the clutch. It's kinda deceptive actually.

By doing that he basically eliminated some of the distance the engine has to travel from the start to reach it's maximum powerband, and also elminated the time necessary to accelerate through those RPM's.

If both cars from his example started to accelerate from a dead stop, at idle, and force to accelerate through the entire engine rpm range and not at peak powerband, the graph would be different.

PS.

His calculations are correct. I'm just saying it's deceptive because it doesn't applied to "normal" driving. It only applies to accelerating by dropping your clutch at maximum power band.

 

Actually, I was going to note to ignore the physics student's calculations at the end that involved a clutch drop. You can't simply use a = P / (v * m) because a slipping clutch does not transmit full power.

But if you're smart enough to follow the math, you'll be able to figure it out on your own, right?

I would like to see his calculations about the 5.0 vs. 2.0 race that included proper gearing.

 

Actually i skipped parts of it cuz he was using variables i'm not use to when dealing with this stuff and I didn't wanna rewrite everything. He also skipped steps in between which was confusing at first, since it didn't look like formula's i'm used to.

As a resultc I skipped through parts of it, but it look "ok" using the method he used.

Only problem I had with his argument was that he was using maximum peak power only. This means he ELIMINATED the extra DISTANCE and TIME that both engine normally has to accelerate through to reach peak power.

PS...

I haven't done physics in a while....but my best guess at what he's trying to say is this

HP (Work) = Work Function (W)
Torque (Force) = Force function (F)
RPM (distance) = distance function (D)

It does kinda makes sense since, but his comparison of his engines also ignores this....

He's assuming that for every 1 RPM in both cars, the engine is coverning equal distances. That isn't necessarily true........

Although, wouldn't it be easier to just do this?

Example:

2003 Honda S2000 vs. 2005 Honda S2000..........

Just time how long it takes for each of the cars to reach maximum RPM in 1st gear from a stand still without dropping the clutch. Same with 2nd gear.

Both S2000 should have the exact stats, except the newer ones have more torque.