I always heard the cylinder head dictated the HP potential and the stroke dictated the torque curve. Like a 170/198/225. All had the ability to make a measly 145HP but who would get there first? "HP=HP no matter how you devide it up" is true..., you can make a high revver but have little to no useable torque. Look at a Hayabusa Motorcycle engine: 85 hp at 85 ft/lbs at 5250. HP keeps going up to 180 at 10K but the torque stays flat at 85. Whats the saying.."HP sells cars but Torque wins races"?
Engine A 1st gear 2.5:1 x 4:1 = 10:1
dyno.................................. track
rpm/ Tq/ hp..........mph/ tq ground/ Hp ground
2500 381 181 21 3810 lbs-ft 181
3000 403 230 24 4030 " 230
3500 415 277 28 4150 " 277
4000 438 333 32 4380 " 333
4500 437 375 36 4370 " 375
5000 416 396 40 4160 " 396
5500 389 407 44 3890 " 407
6000 344 395 48 3440 " 395
4029 lbs-ft average
Engine B 1st gear 2.5:1 x 5:1 = 12.5:1
dyno ..................................track
rpm/ Tq/ hp......mph/ tq ground/ hp ground
3500 272 181 23 3400 lbs-ft 181
4000 302 230 26 3775 " 230
4500 323 277 29 4038 " 277
5000 350 333 32 4375 " 333
5500 358 375 35 4475 " 375
6000 347 396 39 4338 " 396
6500 329 407 42 4113 " 407
7000 296 395 45 3700 " 395
4027 lbs-ft average
1st of all torque and hp aren't two separate abilities.
hp is torque combined with rpm.
You can't separate torque and rpm, a running is always doing both.
Yes torque moves your car but not without rpm. Which is hp.
Think of it this way torque is a snapshot of one powerstroke.
One powerstroke ain't gonna get you too far but them all added up over time (rpm)
Now you got hp, the combined ability of rpm and torque to move and accelerate your car.
Heres why your engine torque numbers isn't as important as your hp numbers.
For one the torque numbers are part of the hp numbers plus only tells you whats happening at the crank,
not whats getting to the ground through the tires and the rest of the driveline.
For the future eg. this driveline loses zero hp through friction etc...
1st of all gearing only multiply or divide torque and rpm not hp. hp will always be constant.
1st eg. 200 hp @ 4000 rpm has 263 lbs-ft @ 4000 rpm also.
If you put it through 4:1 gears torque will multiply by 4 to 1050 lbs-ft, which is 1050 lbs-ft divided between two tires
to the ground.But instead of spinning 4000 rpm the rpm is divided by 4 and now the tires rotate 1000 rpm. Which is
1000 x 1050 \ 5252 = 200 hp.
2nd eg. if you look at both engine dyno above you'll see Engine A powerband goes from 2500-6000 rpm and Engine B powerband
is a 1000 rpm higher, 3500-7000 rpm. Engine A and B make the same hp but B does 1000 rpm higher and A makes more torque.
Obviously A is bigger displacement, and yes more streetable needing less gear etc.. but thats not point, both have same
potential even though A has more torque which I'll show it don't matter as long as there geared right.
Both engine have same 1st gear of 2.5:1 both are in same cars with same weight traction etc... But different stalls and gears.
Engine A has 4:1 and B has 5:1. If you look at hp to the ground is the same as the engines. If you look at torque and mph it verys
a little. But if you look at average torque to the ground pretty much identical A 4029 lbs-ft vs B 4027 lbs-ft.
Both Engines are pretty similar performance wise. Torque doesn't matter as much as hp as long there properly geared.
Engine A has the obvious advantage for the street not so much cause of torque but cause it makes low rpm hp.
Engine A was a 360 and B would be mathematically a 305 mopar.
