Understanding Power/Torque Characteristics...

[pixelparadigm]

I'm just wondering... same engine make, same displacement, normally aspirated, but different power/torque characteristics. How do they differ in acceleration performance? It's almost as same as the HP vs Torque question, but how come the end result is somewhat hard to predict(lets add gear ratios as a variable here)?

or

Lets say we compare an american muscle V8 engine vs. honda NA engines (S2000 or NSX engine), with the same HP. What do you think which will have a better result on straight line speed / cornering?

Usually Honda's engine are naturally high-revving while pushrod large-displacement musclecar engines do have lots of torque. Can the honda engine keep up with a musclecar engine because it can rev higher while engaged on a lower gear ratio before hitting the rev limit then shift, or the musclecar engine would just outrun the honda engine because of sheer torque numbers?

And sa NFS:U2 or kahit sa GT... dyno charts there tells that maximum torque usually peaks just right before maximum power is achieved. In the real world, how does that translate to acceleration? Why not shift up on the moment the torque peaks instead of waiting for the engine to hit the rev limit?

[Karding]

Why not shift up on the moment the torque peaks instead of waiting for the engine to hit the rev limit?

Because if you shift at redline, you are likely to "stay" within your optimum powerband when you shift.

i.e. stock B18C1 170hp * 7600rpm

I had to shift at 8k rpm because the peak hp comes at 7600rpm. When I shift at 8000rpm, the needle usually drops 500rpm. So, after shifting the gear, I only have 100rpm to reach (again) the rpm generating all the horses.

What do you think which will have a better result on straight line speed / cornering?

cornering = slalom??

Do we have 2 different categories here or combined straighline speed and cornering?

I believe that muscle cars were not made for cornering. Thus, combining the speed and cornering categories wouldn't make sense.

IMHO.

[gwapito69]

kung maganda ng weight ratio ng oto mo you can take it to the track which is may straight line and cornering. but make sure the car can handle that certain speed pagdating sa cornering kung hindi lagot ang oto mo. tama si kapatid Karding dapat ang pag up shift mo e sa 100rpm b4 you hit the redline...

[niky]

A lot is said about usable horsepower and torque, but what really matters is how well your engine's powerband matches the gears.

The main problem with Honda engines is that their powerband is very high up... say, on the B18, you have usable power between 6000rpm and 8000rpm. What this means is, from a standing start, you are spending the time from 1000-6000rpm in a low horsepower area of the hp curve, making it sluggish. Whereas, with a 2.0 like on my RS, torque peaks lower, giving you a bigger kick in the pants at about 2000rpm (with over 100ft-lbs of torque at near idle) up to about 4000rpm, and gets you to peak horsepower sooner.

My horsepower peak is low, but I get there faster, BUT the guy with the Honda engine will still be accelerating, and he has more horsepower over 6000rpm than I do... he'll kick my a$$, no doubt. Torque only matters for the first second or two out of a corner or from a standing start, then HP is all that matters.

In a race, as long as the gearing matches your engine and the demands of the track, you can keep the engine spinning in the proper rev range to produce maximum hp. With a torquey engine, this is easy, as if you dip below your optimum power band, it'll push you back into it quickly. With a revvy engine, you have to be careful not to shift too early or let the engine fall below its useable rpm peak. A torquey engine may seem better for slow tracks, then, but higher horsepower is always better, as speed on the straights makes up for difficulties in turns. And close-ratio transmissions on most Hondas can make up for the lack of torque, anyway.

Nissan once made a Sentra/Sunny/Pulsar with a 1.6 liter 190hp engine. It had more power than a Honda B16, but couldn't keep up with a Spoon Civic of the same power. Reason? Useable power. The Nissan had a useable powerband that was so high up in the rev range, it was almost impossible to access.

Same thing with Toyota's XRS Corolla variant. It's got 180+ hp, but it's slower than the Honda (and even my RS!) because the useable powerband is VERY far up and the gearing (for economy's sake) isn't made to exploit it fully.

[Karding]

My horsepower peak is low, but I get there faster, BUT the guy with the Honda engine will still be accelerating, and he has more horsepower over 6000rpm than I do... he'll kick my a$$, no doubt. Torque only matters for the first second or two out of a corner or from a standing start, then HP is all that matters.

reminds me of the guy who bought my Civic. He owns a SLK32 and beats the Integra R on standing still. Above 60mph, he slowed down so he wont get embarassed because the ITR is about to pass him...in flying colors :hihihi: