HP vs TQ question

[Bob In Ct]

Torque has no time function, HP does! It's all about HP. Transmissions and differentials can always increase torque but they don't increase HP. 800 Ft-LBS is not very useful at 100 RPM (waterwheel effect). 400 FT-LBS at 6,000 RPM is far more valuable.

Bob

[xlr8or]

Originally Posted by Bob In Ct

Torque has no time function, HP does! It's all about HP. Transmissions and differentials can always increase torque but they don't increase HP. 800 Ft-LBS is not very useful at 100 RPM (waterwheel effect). 400 FT-LBS at 6,000 RPM is far more valuable.

Bob

Tell that to a guy with a diesel hauling 40,000 lbs in the trailer.

Both are very useful when used in the appropriate application. If the car is primarily street driven I prefer a wide torque band over a peaky horsepower curve. The track is a different animal and you want the HP up high in the RPM range where you will be running the engine.

[Jac Mac]

You cannot measure HP without knowing what Torque you have first.

Lets say for some crazy reason you decide you need 800 HP @ 7000rpm.
To obtain that you simply just keep developing the combination until you have
600 ft/lb of torque @ 7000rpm, you only get torque readings from the dyno, the HP is simply a calculation from that reading in conjunction with RPM with allowances for Temp-Humidity etc.

BHP = [(RPM x Torque) divided by 5250]

Torque= [(BHP x 5250) divided by RPM]

Jac Mac

[RedBarchetta]

I recall someone once telling me that "Torque gets you up to a certain speed and Horsepower keeps you there." Works in NASCAR.

[lovehamr]

In this same vein someone once told me this;

“You feel torque from the seat of your pants much more than you feel horsepower.”

The human butt can no more distinguish torque from HP than it can blue light from red light. In simplest terms we are dealing with power or energy, a force that moves you. These forces are expressed in mathematical terms thusly;

1 HP = 33,000 foot-pounds per minute (there’s that over time thing that Bob mentioned)
Or it could be P/hp=[T/(ft lb)][w/(r/min)]
5252
By the way, that 5252 is why nearly all dyno charts show the HP and torque curves crossing at that RPM.
Or it could be 746 watts
Or maybe 2,545 BTUs (British thermal units)
One BTU being equal to 1,055 joules, or 252 gram-calories or 0.252 food calories.
This means that 1 HP is also equal to 2684975 joules, or 63504 gram-calories, or 641.34 food calories
Presumably, a horse producing 1 horsepower would burn about 641 Calories in one hour if it were 100% efficient.

The point is that its energy, a force, what moves you, not some nebulous calculation as others have postulated.

Torque is the force applied to a lever, multiplied by its distance from the lever's fulcrum in our case a theoretical lever and a rotating fulcrum, or more simply:
T = r x F (whadaya know another calculated theoretical number)
Which is linier force multiplied by a radius. Of course this formula always assumes a perpendicular force axis to the fulcrum, something that just doesn’t happen in a reciprocating engine for more than a millisecond at a time.

From the Ole mechanic “You know when your on the entrance ramp to an interstate doing about 20 mph???? then you accelerate to say 70 mph and blend in???? Torque gets you to 70 mph, horse power keeps you there once you hit your speed and level off...............”

To put this into perspective the next time you want to accelerate really fast try shifting at your engine’s torque peak rather than the HP peak. It doesn’t take a rocket scientist figure out using which shift point will accelerate the car faster. This is because we’re talking about energy expended over time not a static applied force. To say that another way; I could put 84 pounds (that’s a Buell motorcycle’s peak output) of torque on the bike’s crank shaft with a ratchet handle, but I don’t think it’s going to accelerate too quickly and I doubt that the rider’d feel it to much in the seat of his pants either.

I find the whole argument over HP vs. Torque to be silly in the extreme because they are really one and the same, just expressed differently to show how the power is produced in any given engine for any given application. For instance a tow vehicle was mentioned; do we want high RPM power for our tow rig? I think not, we want it down low so that it’s managable and produces minimum wear on moving parts. How about the drag car? We want as much power as possible and since an internal combustion engine is in effect an air pump then we want as much air as possible to pass through the engine. All things being equal, the faster the engine is turned, the more air goes through it, the more power is made over any given period of time.

In summary, to disassociate HP and bow to torque is like saying that you really like chocolate cake but that chocolate is over rated. It just doesn’t make sense.

Steve

[Dwight]

OK Steve

Why is my Tq more than my hp? Would you look at my dyno chart and tell me what is happening and why?

Dwight
I hope you can see the picture of the chart

[dynoroom]

Originally Posted by Dwight

OK Steve

Why is my Tq more than my hp? Would you look at my dyno chart and tell me what is happening and why?

Dwight
I hope you can see the picture of the chart

The simple answer is your engine doesn't have the torque where you need it to make the HP you want. This can be due to many things (exhaust, cam, heads, intake, etc.) That's why we test on the dyno and make changes to see if we can make more power (or move the torque we have).
If you could take the peak torque you have of about 350 lb/ft and move it up the rpm scale (eaiser said than done) from 4500 rpm to say 7500 rpm you'd have 500 HP (350 X 7500 / 5252 = 500 HP).
This is why some of us build strokers to make more torque at a lower engine speed to make the power we want.

[Dwight]

What would it take to move it to 6000 rpm?
Here is what I have

weight 2315 no gas 17 gal fuel cell 185 lb driver
8.8 '89 Mustang rear end with 3:55 gears and BFG G-Force tires ( 25.25" tall)
4 link with adjustable coil overs
54.5% rear weight and 46.3% front
TKO 600 with 2.87 1.89 1.28 1.0 .64 gears
10 1/2" McLeod clutch, 50 oz billel steel flywheel
96 5.0 truck block
Eagle forged 3.47" crank, SIR 540CB forged rods, SRP forged pistons #144995
354 cid 10.67 CR
Romac aluminum 50 oz damper

all rotating assembly balanced by local shop

Comp cam XE274HR-12
Brand: COMP Cams
Product Line: COMP Cams Xtreme Energy Camshafts
Part Type: Camshafts
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 2,200-6,200
Intake Duration at 050 inch Lift: 224
Exhaust Duration at 050 inch Lift: 232
Duration at 050 inch Lift: 224 int./232 exh.
Advertised Intake Duration: 274
Advertised Exhaust Duration: 282
Advertised Duration: 274 int./282 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.555 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.565 in.
Valve Lift with Factory Rocker Arm Ratio: 0.555 int./0.565 exh. lift
Lobe Separation (degrees): 112
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: Yes
Grind Number: FW XE274HR-12
1.7 roller rockers
Pro Com aluminum heads: 190cc runners - 60cc combustion camber - raised exh port .25"
int. 2.02" & 1.6" exh valves -- heads will flow approx. 270cfm intake and 200 cfm exh @600 lift

36 lb injectors and a Granatelli 90 mm mass air meter

Mallery multi spark ignition box and a 89 Mustang computer A9L with a
Custom SCT chip to make it all work together. Car dyno'ed with chip.

Melling HV oil pump 65 cold idle & 30 hot psi
Holley SysMax II upper and lower intake
73 mm BBK throttle body
stock 89 Mustang distributor
8.5 mm MSD wires
7 qt Cannon oil pan
3/8" fuel line, stock 89 Mustang fuel rail, holley fuel pump 255 lph #HLL-512-105, adjustable pressure regulator set at 38.5 lb.

March aluminum pulleys, under drive on crank and water pump only

1 5/8" equal length header 40" long dumping into 3 1/2" side pipes

I would like to move the tq & HP up to the 2500-6200 rpm range. I also would like the tq & hp to be close to the same. 375 / 375 rear wheel would be nice. What do you guys think I need to change?
If there is any more info you need just ask. Thanks for the help.

Dwight