I just found what is possible the BEST layman's terms explanation of hp and torque

[Guest bastaad525]

Just thought I'd share this with you guys... I know the subject comes up a lot and people always kinda... struggle to explain the relation to torque vs. hp and how they work. This guy did a write up here that really put's it very plain and simply... good reading for anyone interested:

 

http://www.seatcupra.net/guide_powertorque.htm

[grumpyvette]

we have all heard it, " you need massive low rpm tq" "you need a screaming high rpm hp peak" well heres some info,

More in-depth description:

http://www.revsearch.com/dynamometer/torque_vs_horsepower.html

http://www.dynacam.com/Product/Torque_vs__Horsepower/torque_vs__horsepower.html

http://vettenet.org/torquehp.html

http://auto.howstuffworks.com/horsepower4.htm

http://homepage.mac.com/dgiessel/engine/hpvstq.html

 

first thing to keep in mind is that theres no such "thing" as horsepower, horsepower is a mathmatical formula explaining the RATE at which TORQUE (rational force ) can be applied increasing the torque at a given RPM or increasing the RPMS with a given torque increases THE RATE(HORSEPOWER AVAILABLE TO DO WORK)GEARING ALLOWS YOU TO APPLIE THAT FORCE at a given force level but not at a RATE APPLICATION LEVEL that exceeds the engines peak power.

put a differant way, if we ignore drive line friction loss,if an engine puts out 400 ft lbs at 6000rpm (400 x 6000/5252equals (457 hp)we can gear it to apply 1600 ft lbs at the wheels by running the gearing at 4:1 but that also cuts the application rate by 4:1 so the HP applied stays constant at the 1500rpm at the rear wheels 1600 x 1500/5252 equals (457 hp)

 

the formula for hp is (tq x rpm/5252=hp

example

450 ft lbs of torque at 3000rpm=257hp

450 ft lbs of torque at 6000rpm=514hp

because the torque is available at that higher RPM RATE and at the higher rpm useing gearing the rotational force the engine supplied can be applied faster or slower to the rear tires

 

here read these ALL CAREFULLY http://www.69mustang.com/hp_torque.htm

 

http://www.ubermensch.org/Cars/Technical/hp-tq/

 

http://vette.ohioracing.com/hp.html

 

http://auto.howstuffworks.com/engine1.htm

 

http://auto.howstuffworks.com/horsepower.htm

 

http://auto.howstuffworks.com/question622.htm

where most guys go wrong is in not correctly matching the cars stall speed and gearing to the cars tq curve, if you mod the engine for increased high rpm performance but fail to also match the stall speed and gearing to that higher rpm tq curve much of the potential improvement is wasted.

example

in the close to stock engine above, the engine should be geared to stay in the 3500rpm-5000rpm range for max acceleration (lower in the rpm range if mileage is a big factor)

in the moded engine above the rpm range moved to 4000rpm-6500rpm requireing differant rear gears and slightly higher stall speeds to gain max acceleration in the same car,

you should readily see that a trans that shifts at 5000rpm will work in the first example but would waste most of the power curve in the second example,where shifting at 6500rpm under full power acelleration would make more sence.

a 3.08 rear gear and 700r4 trans matches the first example well but it would take a swap to a 3.73-4.11 gear to allow the engine in the second example to keep its most effective power band matching that second power curve well.

 

links youll need to figure out correct rear gear ratios

 

http://www.miata.net/garage/tirecalc.html

 

http://www.wallaceracing.com/reargear.htm

 

http://users.erols.com/srweiss/calcmph.htm

 

http://users.erols.com/srweiss/calcrpm.htm

 

http://users.erols.com/srweiss/calcrgr.htm

 

http://www.prestage.com/Car+Math/Ge...io/default.aspx

 

http://www.geocities.com/z28esser/speed.html

 

http://server3003.freeyellow.com/gparts/speedo.htm

 

http://www.pontiacracing.net/trannyratios.htm

 

http://www.tciauto.com/tech_info/gear_ratios.htm

[Pop N Wood]

first thing to keep in mind is that theres no such "thing" as horsepower' date=' horsepower is a mathmatical formula explaining [b'] the RATE at which TORQUE (rational force ) can be applied increasing the torque at a given RPM or increasing the RPMS with a given torque increases

 

Poo. Not this one again.

[Guest bastaad525]

LOL Grumpyvette!

 

 

well I've been thru most of those links you gave before, but as I said, this link I found was the... I dunno... the easiest to understand explanation I've read so far.

 

 

The whole metaphor about the two guys riding bicycles and stuff..., and the comparisons between a high torque, low revving motor, and a low torque high revving motor, just made it that much easier to really understand how it all works. It also gives a really good explanation as to how gearing plays into the whole thing.

 

Well I hope guys will still even bother with that link now that you've put like 20 more for them to look at

[wpnmkr]

Bastaad525,that is very easy to digest. What a way cool explanation!