How does cid make power?

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But also, torque is meaningless. It's a force. It's measured instantaneously. It doesn't have anything to do with how well the engine can accelerate - that's why the HP measure exists. Without it, we cannot relate to what happens 'per unit time', meaning we can't figure out how the engine will accelerate, how it will propel, or how much weight it can move in a given amount of time.

It's why tractors are rated by horsepower and not torque, despite needing torque to 'pull stumps' and such. Only having a 105 ft-lbs measure wouldn't tell me much about what I can do with an engine. But tell me 5, 10, 40 horse and I know how much it can 'do' in a unit of time.

100%

when people say torque engines they actually talking about low rpm hp.
 

Phreakish

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when people say torque engines they actually talking about low rpm hp.

I'll also say that it still 'depends'. I agree that 'low rpm hp' engine is exactly what you get with a 'torque' motor. The reason 'it depends' is because dynos can run at various rpm rates, and that rate can have a significant effect on the outcome. A slow ramp rate will let a lazy build look good on paper (bigger numbers), but will tend not to perform well in a light (fast accelerating) car.
A quick ramp rate can make a decent build look lazy by 'outrunning' the engine's ability to accelerate. A quick ramp rate could also hide harmonics in the valvetrain though by quickly accelerating past trouble spots in the rev range.

What makes sciencing it difficult is that the way 'torque' is captured is back-computed from the dyno resistence necessary to hold that ramp rate. How the dyno back-computes could be done in a few different ways, which is probably just one of the variables behind dyno differences.
 

Rat Bastid

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But also, torque is meaningless. It's a force. It's measured instantaneously. It doesn't have anything to do with how well the engine can accelerate - that's why the HP measure exists. Without it, we cannot relate to what happens 'per unit time', meaning we can't figure out how the engine will accelerate, how it will propel, or how much weight it can move in a given amount of time.

It's why tractors are rated by horsepower and not torque, despite needing torque to 'pull stumps' and such. Only having a 105 ft-lbs measure wouldn't tell me much about what I can do with an engine. But tell me 5, 10, 40 horse and I know how much it can 'do' in a unit of time.


There should be a 1,000 like button for posts like this!!!
 

Dale Davies

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Ok, post 258. Lots of torque curves drop quite rapidly and it does not matter. IMO, dragging the torque curve flatter, longer means you are out of induction. That’s not a good way to make power.

Part of my point was you can’t just manipulate torque (especially above peak) and not hurt horsepower.

Which, BTW may be calculated but again, you can have all the torque you want and have zero horsepower. That’s not good is it?

No matter what, you have to have RPM. Otherwise no work gets done.

Show me any performance calculator that uses torque and I will renounce every word I’ve ever said about horsepower.
You being a 1/4 mile guy, torque gets you a quick 60 foot time. HP gets you trap speed and ET.
 

Phreakish

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You being a 1/4 mile guy, torque gets you a quick 60 foot time. HP gets you trap speed and ET.

I'd argue suspension is what gets the 60. Traction and initial acceleration is what cuts it short. Just as an illustration, lots of fast cars leave on the converter well past peak torque. This is because they want to be deep in the revs to get max work as early as possible.
Clutch cars will control the clutch engagement to keep the revs up but without smoking the disc before it locks.
 

Dale Davies

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But also, torque is meaningless. It's a force. It's measured instantaneously. It doesn't have anything to do with how well the engine can accelerate - that's why the HP measure exists. Without it, we cannot relate to what happens 'per unit time', meaning we can't figure out how the engine will accelerate, how it will propel, or how much weight it can move in a given amount of time.

It's why tractors are rated by horsepower and not torque, despite needing torque to 'pull stumps' and such. Only having a 105 ft-lbs measure wouldn't tell me much about what I can do with an engine. But tell me 5, 10, 40 horse and I know how much it can 'do' in a unit of time.
This is why dyno runs are now done at a rate of acceleration. This is programed into the dyno controls. The engine is loaded to the start RPM and then the dyno controls the RPM increase per second as programmed. This is more like how an engine under acceleration runs, and the dyno software records the torque every say 100 RPM and calculates the HP from that. It is not possible to measure HP directly, only torque.
HP has been used as a value people could wrap their heads around due to indoctrination. An old steam Rumley tractor with 15HP will pull a 400HP modern 4WD tractor backwards due to torque and weight. If it was HP doing the job, the modern tractor should get it done.
Mazda is starting to push advertizing to promote torque for street. Torque gets you off a red light quickly and easily and provides the nice push in the seat of your pants coming out of a corner. Big HP lets you drive 200MPH at Daytona or Bonneville, but not really useable in street driving. It is the torque that gives the calculated HP numbers.
 

Dale Davies

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I'd argue suspension is what gets the 60. Traction and initial acceleration is what cuts it short. Just as an illustration, lots of fast cars leave on the converter well past peak torque. This is because they want to be deep in the revs to get max work as early as possible.
Clutch cars will control the clutch engagement to keep the revs up but without smoking the disc before it locks.
Suspension allows hookup to get the maximum traction your tires are capable of. Lots of gear is torque. A loose converter does let the engine rev more, but also generally produces more torque multiplication. There is a limit on that though.
 

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This is why dyno runs are now done at a rate of acceleration. This is programed into the dyno controls. The engine is loaded to the start RPM and then the dyno controls the RPM increase per second as programmed. This is more like how an engine under acceleration runs, and the dyno software records the torque every say 100 RPM and calculates the HP from that. It is not possible to measure HP directly, only torque.
HP has been used as a value people could wrap their heads around due to indoctrination. An old steam Rumley tractor with 15HP will pull a 400HP modern 4WD tractor backwards due to torque and weight. If it was HP doing the job, the modern tractor should get it done.
Mazda is starting to push advertizing to promote torque for street. Torque gets you off a red light quickly and easily and provides the nice push in the seat of your pants coming out of a corner. Big HP lets you drive 200MPH at Daytona or Bonneville, but not really useable in street driving. It is the torque that gives the calculated HP numbers.


Sorry, but you don’t have a clue.

For one, there are engine dyno’s that measure an engines ability to RPM. They are far more accurate than a water brake dyno.

You can argue torque is measured blah blah blah but Phreakish already explained that to you. Did you miss that?

Horsepower moves the car, or any other vehicle. Sorry, but that’s the fact.

Like I say, torque sells magazines and horsepower wins races. Mazda is just marketing what will sell cars, not what makes more power.
 

Phreakish

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This is why dyno runs are now done at a rate of acceleration. This is programed into the dyno controls. The engine is loaded to the start RPM and then the dyno controls the RPM increase per second as programmed. This is more like how an engine under acceleration runs, and the dyno software records the torque every say 100 RPM and calculates the HP from that. It is not possible to measure HP directly, only torque.
HP has been used as a value people could wrap their heads around due to indoctrination. An old steam Rumley tractor with 15HP will pull a 400HP modern 4WD tractor backwards due to torque and weight. If it was HP doing the job, the modern tractor should get it done.
Mazda is starting to push advertizing to promote torque for street. Torque gets you off a red light quickly and easily and provides the nice push in the seat of your pants coming out of a corner. Big HP lets you drive 200MPH at Daytona or Bonneville, but not really useable in street driving. It is the torque that gives the calculated HP numbers.

Torque is not accurately measure unless one stops the engines acceleration. The rate is used to simulate a car accelerating, and the torque is backed out of the force required to hold that rate. But the actual torque spit out and graphed is not what is measured.. It can't be, otherwise the engine wouldn't gain revs. Instead one can use the rate and some constants to figure out what the stopping torque would theoretically be and good software can be close, but I'm sure not all softwares are equal..
 

Phreakish

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Surely 2 horses will pull a carriage faster than 1.

LOL, to an extent. Two horses will get there quicker, and pull more, but typically not faster ;)

But this is what the "horsepower" figure is derived from: work. Speed is just the result of work being done to mass.
 

Rat Bastid

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Torque is not accurately measure unless one stops the engines acceleration. The rate is used to simulate a car accelerating, and the torque is backed out of the force required to hold that rate. But the actual torque spit out and graphed is not what is measured.. It can't be, otherwise the engine wouldn't gain revs. Instead one can use the rate and some constants to figure out what the stopping torque would theoretically be and good software can be close, but I'm sure not all softwares are equal..


EXACTLY. That’s why it’s called BRAKE HORSEPOWER.

You pick an RPM, load the **** out of the engine and hold it there all while the engine has its tongue out.

And what did we learn? Not much. That’s what torque you make at that RPM. It doesn’t tell you much but you’ve got a torque number.
 

Dale Davies

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EXACTLY. That’s why it’s called BRAKE HORSEPOWER.

You pick an RPM, load the **** out of the engine and hold it there all while the engine has its tongue out.

And what did we learn? Not much. That’s what torque you make at that RPM. It doesn’t tell you much but you’ve got a torque number.
I have run diesels on a manual dyno where it was loaded to an RPM and let stabilize. Then we changed load to change the RPM by 100, let it stabilize again. When stabile we tapped a record button. Then a graph was printed. This generally closely matched the factory graphs used in advertizing. Works for heavy duty where a truck engine is loaded and running down the highway.
For performance street and racing, you want to know transitional torque and HP.
 

Rat Bastid

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I have run diesels on a manual dyno where it was loaded to an RPM and let stabilize. Then we changed load to change the RPM by 100, let it stabilize again. When stabile we tapped a record button. Then a graph was printed. This generally closely matched the factory graphs used in advertizing. Works for heavy duty where a truck engine is loaded and running down the highway.
For performance street and racing, you want to know transitional torque and HP.


That test makes sense for what we ask Diesel engines to do. Making along uphill pull with minimal increase or decrease in RPM.

I suppose in a race setting that test would only be effective if you were building engines for Daytona or Talladega where you basically flat foot it all the way around the track.

Of course, if you are wanting to check emulsion or something at a particular throttle opening/load/RPM a brake load test would be what you’d do then too.
 

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I have run diesels on a manual dyno where it was loaded to an RPM and let stabilize. Then we changed load to change the RPM by 100, let it stabilize again.
Plotting.... it's been done on race engines as well.
 

Rat Bastid

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i used to think this. I changed my mind when my 340” has a better 60’ then a lot of 4” strokers I have seen.


Once you learn that it changes the way you build engines. For those that are willing to learn anyway.

I was lucky enough to grow up with a dad who raced an F Stock Barracuda and he took my brother and I to almost every type of Motorsports events you could think of. When we got our dirt bikes he had rules. Grades had to be up, no skipping school and the bikes had to be ready to go or we didn’t ride. When we started out that meant a clean bike (he meant clean too, not some hose job) and a lubed chain. Then as we learned we had more to do. He only did for us what were weren’t capable of, until we were capable.

The biggest thing for me was going to the drag races and seeing the Modified Eliminator cars. I was in the first grade and I was enthralled with the big RPM and the clutches. By the time I could read I was in the National Dragster reading everything but specifically looking a Modified National Records and such.

By the time I was 15 I was planning a Modified car. Of course NHRA killed Modified before I graduated HS, but all the learning I did when I was younger shaped my philosophy for how a race engine should be built.

And some of that translates to street/strip stuff too.
 
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