ok...

 

Well, it is just a number. Torque is real.

 

Horsepower is as real as torque.

If that's the case then how can a 5.4L making less than 350 ft-lbs@5,000 RPMs accelerate faster than a 7.3L making over 400 ft-lbs @ 3,000 RPMs?

Less torque, higher RPMs but more POWER.

 

How do they measure horsepower on a dyno bill? they measure torque then multiply it times rpm then divide it by 5252 to get hp. So torque is the base of the engines power

 

NO. NO. NO.
I've said this before,and I'll say it again.
A Dyno measures the HP, and the torque is calculated based on engine RPM. Remove the RPM input from the engine to the dyno,and it CANNOT give you a torque value-you must hand calculate it based on the HP values MEASURED.
JL

 

Dynos are backwards, they accurately do measure HP then calculate Torque. Most of them are that way.

 

Just like I said. The 7.3 tows easier at lower rpms but if I let the engines run where they perform the best the 5.4 wins.

 

Take the same engines and load them to their max gcwr and see which one will accelerate faster. A 235 hp tractor will not win a race but can pull a 30ft disc. Now i know weight is a difference and so is gearing but all gearing does is multiply torque and weight controls slippage. you cannot multipy horsepower

 

Wrong, Wrong, Wrong! Having worked on dynos, and done hundreds of dyno tests, dynos measure Torque and caculate HP.

HowStuffWorks "Measuring Horsepower"

 

From Wikipedia, the free encyclopedia
<!-- /tagline --><!-- subtitle -->
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<!-- /jumpto --><!-- bodytext -->Not to be confused with dynameter.
<DL><DD>For the dynamometer used in railroading, see dynamometer car.</DD></DL>A dynamometer or "dyno" for short, is a device for measuring force, moment of force (torque), or power. For example, the power produced by an engine, motor or other rotating prime mover can be calculated by simultaneously measuring torque and rotational speed (RPM).
Hmmm i guess i was wrong!

 

I invite anybody here to contact Dynojet or Mustang Dyno(the 2 major players in dyno systems) and discuss this with them.
Their dynos measure horsepower.
I'm not gonna argue it anymore unless you can provide more data than "I've done hundreds of dyno tests" blah,blah,blah.
Since you've "worked on dynos", try this next time you're on the dyno. REMOVE ALL rpm inputs from the engine into the dyno. See what shows up on the graph when you finish the pull. I've been there. I've done it. I KNOW what the result is.
JL

 

For a given weight whichever engine is producing more power is the one that will accelerate faster.

For example, there's a large trucking company that spec's it's trucks with 370 HP engines. The Freightliner tractors weigh around 17,000 lbs empty.

My '11 6.7L truck makes 400 HP. I could tow 9,000 lbs to 60 MPH faster than that Freightliner could do it bobtail.

So could a 6.2L 385 HP gas truck!

 

The Scottish Engineer and inventor, James Watt (1736-1819), introduced the term "horsepower". The term was and is used to indicate the rate at which an engine can deliver work. As such, it is a measure of power, that is, energy produced or work done by an engine per unit of time. Mr. Watt wanted to tell how powerful his engines were. So, after some tests (not with engines but with horses) he established that on the average, a horse could haul coal at the rate of 22,000 lb-ft per min. In order to conservatively rate his engines, he decided the raise this number by 50% to arrive at 33,000 lb-ft per minute.

So, if an engine can push 33,000 Lb of something one foot in one minute, we say that is a one-horsepower engine.

So horsepower is not an "imaginary" number. It is in fact, a conservative number grounded in sound scientific fact. It is therefore a measurement of work performed over time. This is opposed to torque, which is the amount of work which can be done per revolution at a given engine RPM. So If two engines are geared for their optimum horsepower, the one which has the highest numbers will in fact pull a heavier load at the same speed as the lower horsepower engine, or will pull the same load as the lower horsepower engine at a faster rate of speed. That is why to you PSD guys, a V-10 sounds like it's going to "blow up" when hauling a heavy load. It is geared for it's optimum RPM range and therefore is revving up to a higher RPM than the diesel is to get into it's powerband. Now, if we dropped a V-10 into a truck that has PSD gearing, it will not pull, because it can't get into it's powerband. However, both engines are geared appropriately, the one with the higher horsepower will pull the heavier load or the same load faster. You can argue the point all you want, but this is basic physics. Power is real, whether it is low RPM grunting power, or high RPM screaming power, it is the same thing. If it weren't, Navy destroyers wouldn't be powered by gas turbine engines (little torque, tons of RPM). FYI, diesels would have never supplanted steam locomotives in railroading either, since steamers produce max torque at 0 RPM. However, diesels rev higher and produce more horsepower than steamers do, and therefore, diesels replaced the steamers, because diesels aren't driving the drive wheels directly, but they are driving the wheels through either a mechanical transmission (smaller switchers) or through a generator/electric motor arrangement that allows the diesel engine to run at it's optimal RPM to produce horsepower which is used to do work. Period.

 

Wrong wrong wrong wrong wrong wrong wrong wrong wrong,

the Engine Dyno in this article does. I dont know anyone who is gonna pull their engine to put it on an engine Dyno.

On a Chassis Dyno you accually can leave your engine in your car, you put the powered wheels on a Roller and go from there. Hold on here comes the good part. It is Measuring how fast the roller is being moved.....

HP is a Unit of measure how fast work is being done.

Torque is a Measure of How much work can be done.

back to the Chassis dyno, now if you pay attention at a Dyno when they are hooking it up. Pay attention because someone is gonna hook a Sensor up under the front of the Car that is measuring your Vehicle RPM's Between the Roller spinning and that sensor they will calculate your Torque.

Most Dynos people run on will Measure HP first, then calculate Torque.

If you don't believe me to get a Dyno run and tell the Guy to not hook up the sensor you will get only HP.


Chassis Dyno Guide - Frequently Asked Questions About Dyno Tests - Hot Rod Magazine

"How does an inertia dyno work?


Inertia dynos extrapolate horsepower output by analyzing the dyno drum's acceleration rate using a sophisticated accelerometer and computer software. An inertia dyno works only when the car is accelerating. It uses heavy roller drums of known mass mounted on bearings that allow them to freely rotate. A vehicle is placed in position on the dyno with the drive wheels sitting on the rollers. The car is placed in gear and accelerated at wide-open throttle. It takes a certain amount of time and force for the tires to accelerate the heavy rollers. The laws of physics state that acceleration rate is directly proportional to how much power the tires place on the heavy roller to get it to rotate. The dyno software monitors roller velocity and the time it takes to arrive at a rate of acceleration and estimates power at the rear wheels. Using data from an engine-mounted inductive probe, the software then graphs the power and gear-compensated engine torque against engine rpm. Some inertia dynos also attempt to estimate flywheel power and torque numbers based on mathematical models and data from additional sensors."

 

Tell me how it measures hp. the dynos i have ever fooled with take a fluid and the spinning of the wheels force the fluid through an orffice.You then can tell by the pressure how much torque is required to do it.