How long do you have?
OK, short version:
Torque is rotational force, for cars in the US, shown as lb/ft, i.e., amount of turning force applied to move
one pound a distance of
one foot around an axis at a radius of one foot.
Horsepower is work over time, so when we calculate it, we factor in RPM, i.e., revolutions per minute == work / time, and in specifically it's this equation:
H = T x RPM / 5252
So on a dyno graph, where you see a plot of both HP and Torque, they'll always cross at 5252 RPM ...
Anyway, so what you're seeing is HP is produced as the engine spins, so those low HP, high TQ vehicles typically have lots of TQ low in the RPM range (usually due to some combination of displacement/design/FI), but don't have a ton of rev capability, so their HP is lower-ish (relative to the TQ).
So you have engines, like big diesels that make 550lb/ft of torque but only 240HP, and F1 engines that make 200lb/ft of torque but ~800HP (because the latter rev to 15,000+ RPMs).
And of course, don't forget gearing, that's a HUGE contributor to the final, effective performance, in fact, as a smart engineer once said, I'd rather have torque higher than lower in the RPM range to take advantage of gearing. Keeping the RPMs high between shifts, near the peak means faster acceleration over time.
This is a dyno chart, from, umm, some random, tuned MY18+ GT A10
View attachment 961437
The lighter red line is torque, note how it's 350-400 across the RPM range (the scale at the bottom), and as the RPMs increase, the darker red (HP / Power) value increases to the point where the engine start losing efficiency, torque starts to drop off.
This one was actually cut a little short, it made power right up to about 7200 putting the A10 at a perfect shift point. Engines can only spin so fast, and can only ingest so much air, there's all sorts of design considerations to the implementation - and of course, that also has to be factored in with cost, durability, etc., when talking about street vehicles.
FYI, these are measured rear wheel numbers, manufacturers rate the engines at the flywheel, which doesn't take into account the power losses through the transmissions/drivetrain, gears, etc. So using the typical calculation for those losses on a super efficient tranny like the Ford A10, that's ~520HP at the motor
