You are close. I don't smoke, so no cigar.

 

No, melting tires has little to do with torque OR horsepower.

Spinning tires generate heat due to friction between the surface of the tire and the road. This friction is proportional to the speed of the tire, and the friction coefficient between the surfaces. Have you ever wondered why slicky slicks and drag radials tend to smoke faster than Z-rated tires? There's 2 reasons. The first is that the Z-rated tires are designed to deform less and do not heat up as fast (hense they are acceptable for prolonged high-speed use). Second, the slicky tires rubbing on the road generate much more heat due to the higher coefficient of friction between the tire and the road.

If torque was responsible for melting tires, why do you get better burnouts in 2nd gear? The lower gear would result is LESS multiplication and hense LESS torque to the wheel. The wheel speed and friction between the tire/road is what generates the heat... which melts the tire.

Obviously more torque makes it easier to get the wheels spinning (i.e. to overcome the force of friction which gives you traction), but again... this is a force, not power. Power ratings tell you what amount of work you can do, the force available just tells you how hard you can push (not the results).

Quote:

Why do you think they call it a "torque-converter" instead of a Horsepower-Converter?

because you CAN NOT increase an engine's hp with gearing. A hp-converter just doesn't exist. The torque converter multiplies TORQUE by slipping and making the effective gear ratio between the crank and driveshaft larger. Less rpms, but more torque at the cost of some internal slippage. You DO get more hp typically when slipping occurs since this brings the engine rpms up to a more efficient area of the power-curve... but the torque multiplication at the wheels is due to rpm division.

This could be simulated with a manual tranny and more aggressive gearing (and elliminate most of the lost hp from slippage)... but then you'd have to have A LOT more gears to keep it in the power band with gearing, and would loose the benifit of pre-loading the drivetrain, never missing a shift, and a lighter transmission.

Quote:

I would rather have 450 RWTQ at 3000 RPM, than 450 RWHP at 7000 RPM.

Well, that's your choice I guess, but there's no reason this couldn't be the same engine.

257 hp @ 3000 = 450 ftbls
450 hp @ 7000 = 337 ftlbs


If you focus on force, you can determine how much impact a part or object can sustain without damage, but for acceleration of the object the usable power is want to want to focus on.

If this scientific fact doesn't convince you, I don't know what else possibly could:

1) get a dyno curve of your engine (hp and tq)

2) make a RPM vs. wheel speed graft and plot a line for each gear ratio (it will be a straight line intersecting the graph's origin at 0 rpms = 0 mph). If the RPM is on the y-axis, you can determine the rpm you'll start the next gear in by drawing an straight-line down until you hit the next gear's plot line.

3) Using the graphs, determine shift points for a drag race with the following conditions:

Shift Pattern A= make your first shift at any rpm. determine the rest of the shifts to maximize the area under the torque curve from starting rpm (use the rpm vs. wheel speed chart) to shift point.

Shift Pattern B= make your first shift at any rpm. determine the rest of the shifts to maximize the area under the horsepower curve from starting rpm (use the rpm vs. wheel speed chart) to shift point.

Depending on the engine they may be fairly close shift points, but typically the hp shifts will be higher. If it is, shifting for the most torque-production will be robbing you of hp you could have had instead of short-shifting.

HP makes you quick, torque is just one aspect of how it was done (engine rpms being the other ).

 

Sigh... no. IF after gear multiplication you have the same output torque, then there WAS no multiplication. This is the POINT of gears... to change high-force low-rpm inputs, into lower-force higher-rpm outputs (or visa versa if that's your intent). This will change the rotational speed of the gears, and the force imparted by the final output... but the POWER remains the same.

 

agreeded. It's been a few years since I aced University Physics 244, but I'm tryin'

Quote:

the first thing people need to understand is that its not "torque" or "horsepower." One doesn't make up for the other. Its not "well he has more tq and I have more hp so it will be close" This isn't cooking where you can substitute one ingredient for another.

amen! keep going... I'm with ya.

Quote:

...<clip>...

I still to this day do not understand all the "ohhs" and "ahhhs" behind horsepower. It is still about acceleration meaning its still about torque.

As shown above, torque to the wheels can be infinitely adjusted to whatever you want. engine torque does not determine the "F" in your equations... the "F" is Rear Wheel Torque... which is much different depending on gear. to maximze torque to the wheels you need to understand that you NEED a certain amount of RPMs at the engine to keep the wheel speed moving.

You can have all the torque in the world (lets say a few billion foot pounds to keep it reasonable ), but if the engine rpm and gearing locks up to a wheel speed slower than what you're traveling at you will DECELLERATE not ACCELLERATE when the clutch pops out. Force by itself is pointless... it's the power being produced that matters in a system like this... hense torque AND wheel speed (a product of gearing and RPM) matter. You need both. Obviously someone who can produce more REAR WHEEL torque over the same wheel SPEED will faster, however the idea that obscene engine torque levels is nesseasry for it is blatently false.

Power measures work being done in a unit of time, force does not. If you are looking to qantify the speed, acceleration, or kenetic energy of a system to NEED to include rpm into the analyiss... hense the purpose of HORSEPOWER ratings.

 

ok... for an actual example, pick the two engines earlier one with 450 ftlbs @3000, and one with 450 hp @ 7000:

257 hp @ 3000 = 450 ftbls
450 hp @ 7000 = 337 ftlbs

Now assume the first one has a 1:1 ratio with wheel speed, and the second one needs gearings to bring the wheel speed to the same location....

(257 hp, 450 ftlbs @ 3000) x 1:1 = 257hp, 450ftlbs @ 3000 driveshaft rpms
(450 hp, 337 ftlbs @ 7000) x 2.33 = 450hp, 786 ftlbs @ 3000 driveshaft rpms

Still wanta race tq against hp?

HP shows how much potential the vehicel will have based on gearing... torque doesn't.

 

horsepower. shift for max power.

 

Again HP is what matters not torque but some people just won't ever get it.

I have five cars that all make 500 foot pounds of TQ. Which one is fastest?

In fact one could be be an 18 second hoopty and one could be a 9 second ride even if all weight the same because TQ doesn't mean anything really as far as speed goes.

If you know and TQ at any rpm you're talking power. If you are accelerating at all you are moving through space which can only occur through time which is a power equation and not a static TQ equation.

If you know how much TQ you can apply at some RPM then you can see how fast you can go which again is POWER!

HP has both Force (TQ) and Time (RPM) in it so it is what you need to know. There's air cooled diesels that make 120 HP but still make 525 Ft Pounds of TQ and there Pro Stock Trucks that make 950 HP and 525 Ft Pounds of TQ. Then there's turbines that make 1900 HP and still only make 525 Ft Pounds of TQ.

 

Then...generally speaking, wouldn't a longer stroke, slower-turning, larger cube designed engine potentially produce more torque/less hp (all things being equal) then a shorter-stroke, higher-reving, smaller cube engine? If that is true (?), would it therefore (using physics... no matter what the gearing) be "slower" through the traps than the latter?...

I have another question but will wait for the reply to this one first...

 

Longer stroke, larger cube, lower redline = GSXR 1000
Shorter stroke, smaller cube, higher redline = GSXR 750
Guess which is faster?

 

I have always looked at the trq curve. While lowend trq is important to getting you off the line quickly, highend trq is also important in going fast. I am working on trying to put together an engine that makes good lowend with really good highend. If this can be done, then you have a engine that has great street maners, but will roar when you step on it. I only look at hp for reference since it is trq that "does that work" and it is work that moves you down the track.

 

I realize that this will never happen, but the closer I can get the better then engine will be.

 

Tell that to Mercedes Benz

 

Let me finish that 1st guys statement....

"...in a reasonably inexpensive platform."

Yeah w/ a LOT of money you can have different results.

 

[quote]BMW just needs peak tq, aren't they working on an infintely varriable rear diff?[/b]
And when they do, they'll run the engine at peak HP (not torque) for "spirted" driving. A CVT is a great way to explain this... with rpm's constantly being adjusted for road speed, the way to get most torque to the wheels, is to target the most HORSEPOWER at the engine.

Hmmm... everyone in agreement now? (after re-reading tha past few days of posts it seems were all talking about the same concept now, although a few keep reading engine torque as RW-torque... which it isn't). The best way to get tq to the wheels, is to gear it for the highest hp available, which takes rpm's out of the equation and gets you the most torque possible.

Shifting around an engine's torque curve is obviously not going to get this done.

clear as mud eh?

 

I was thinking about a toy inertia car...you know...the kind that you push forward on the floor repeatedly to get it's flywheel to spin faster and faster...then you place it on the floor and it takes off very aggressively. Seems rpms got the torque going, then the torque and gearing moved the toy car very rapidly.
Any comments how that relates to the original question?...
And could that principal be applied to a real car...minus someone picking it up repeatedly...
Could an inertia flywheel help a vehicle get down the track "faster"?... And what would be the downside to this?...