Big Issues with Cylinder Pressure (DCR)

[Ken_Parkman]

The cte for aluminum is approx double that for cast iron depending on precise alloy. For a sbc 9.05" deck block operating at 210 F the change in volume due to thermal expansion between an iron and aluminum block is around 2.8 cc. This is a delta due to the block material, so with all other things equal the change in compression works out to .32 ratio for a typical 10 to 1 type application.

At great risk I will make the following statement. Yes engines make horsepower. Power in basic terms is the time rate of doing work, or a force over a distance at a speed. Engines produce force (torque) over a distance (revolutions) at speed (per minute), otherwise known as horsepower, which is what you measure on a dyno. You only need a torque wrench to measure torque, and that's not much good to figure out the useful output of an engine.

[PSA]

The cte for aluminum is approx double that for cast iron depending on precise alloy. For a sbc 9.05" deck block operating at 210 F the change in volume due to thermal expansion between an iron and aluminum block is around 2.8 cc. This is a delta due to the block material, so with all other things equal the change in compression works out to .32 ratio for a typical 10 to 1 type application.

At great risk I will make the following statement. Yes engines make horsepower. Power in basic terms is the time rate of doing work, or a force over a distance at a speed. Engines produce force (torque) over a distance (revolutions) at speed (per minute), otherwise known as horsepower, which is what you measure on a dyno. You only need a torque wrench to measure torque, and that's not much good to figure out the useful output of an engine.

I would tend to agree to this, air trapped in the engine, measured at the wheels, from point A to B (time) is the energy that moves the body.
Torque is good for development though, as it's trapping efficiency.
But you can burn less air/fuel more times and release the same amount of energy. The width of the power band just have to match the drivetrain (gear ratio, time to change gear etc), to get the highest average hp (energy released from point A to B).

[David Redszus]

At great risk I will make the following statement.

No risk at all. Just semantic discussion.

Yes engines make horsepower.

No, engines make torque which is the product of force and distance,
which is work.

Power in basic terms is the time rate of doing work

Yes, power is, force * distance / time. It is the rate at which work is done.

Engines produce force (torque) over a distance (revolutions) at speed (per minute), otherwise known as horsepower,

Not true. Torque (by definition) is force * distance. When we divide torque by time required, we obtain power.
The equation is: P = lbf * ft / sec. Engine revolutions are merely a surrogate for time

which is what you measure on a dyno.

No it is not. The only thing a dyno can measure is force, which is then multiplied by distance (torque lever arm). When we divide by time units we obtain power.

Dynos do not have horsepower sensors. Power is a calculated number. Power numbers are useless without knowing the time, or engine rpm.

Power can be calculated using many different units: HP, Watts, kW, PS, Ft lbf/s, KgF m/s, BTU/min, Joules/s.

For engine tuning purposes, the torque curve is much more useful than the power curve.
But horsepower assures bragging rights.

[PSA]

I would say that from the engines point of view torque is what you need to look at, but from the vehicles point of view it's hp, kW (or your preferred unit).
That lump of metal under the hood is just converting energy stored in liquid form in to mechanical work (loosely) based on the 1:st law of thermodynamics, burning (let's say) 1lb of fuel in one combustion or ten will have released the same amount of energy (joule, kW etc). As we observe we can see how that energy have been applied to our vehicle (accounting for its limitations) based on time.

I like to loosely compare it with an electric circuit;
12Vx2A=24W
24Vx1A=24W
You can change the Volt (rpm) or Ampere (torque) and get the same Watt (kW, hp, work done).

Well, that's my take on it at least. Maybe we even mean the same thing.

[Tom Walker]

Maybe if David Redszus would let go of one of his math books we could figure this out, but I am still stuck on one of my 5th grade math problems. Goes like this, "If Bobby rode his bike 10 M.P.H. for two hours on Monday, then 3 more hours on Tuesday at 15 M.P.H. and it happened to coincide with daylight savings time, then what can we conclude from the math as to what Bobbys favorite color is?
I am still stuck, but I took a wild quess and said Chrome:)

[Ken_Parkman]

The risk is hijacking the original thread and getting into an endless debate which solves nothing. You are confusing the definitions of torque and work, which are not the same thing. If you want propel a vehicle power is what is required and therefore not just bragging rights. This particular topic has been discussed endlessly in the past and good information, science, and practical examples have been posted in those threads, you just have to discard the comments with incomplete understanding. I am not interested in another repeat; those threads can be searched, so we need to stop here. If you want some help understanding the engineering you can PM me.

[pastry_chef]

You are confusing the definitions of torque and work, which are not the same thing.

He always has and will never get it! Shameful.
Work and engine POWER here.
https://www.grc.nasa.gov/WWW/K-12/airplane/ottoa.html
Not one mention of "torque" on the page.

If your theory contradicts motorsport champions and record holders.. time to quit and find a new field.

Still confused.
viewtopic.php?p=352371#p352371

QUOTE from digger » Sun Feb 05, 2012 3:40 am --- "Torque is not the rotational form of work which you seem to be implying."

[Nut124]

Yes engines make horsepower.

No, engines make torque which is the product of force and distance,
which is work.

David, since you are a respected authority, and folks listen to you, might I respectfully request that you to check the statement above against physics text books?

The way I learned this in school is that torque is just static rotational force. It is not a product of force and distance. And no, torque is not work.

[digger]

At great risk I will make the following statement.

No risk at all. Just semantic discussion.

Yes engines make horsepower.

No, engines make torque which is the product of force and distance,
which is work.

Power in basic terms is the time rate of doing work

Yes, power is, force * distance / time. It is the rate at which work is done.

Engines produce force (torque) over a distance (revolutions) at speed (per minute), otherwise known as horsepower,

Not true. Torque (by definition) is force * distance. When we divide torque by time required, we obtain power.
The equation is: P = lbf * ft / sec. Engine revolutions are merely a surrogate for time

which is what you measure on a dyno.

No it is not. The only thing a dyno can measure is force, which is then multiplied by distance (torque lever arm). When we divide by time units we obtain power.

Dynos do not have horsepower sensors. Power is a calculated number. Power numbers are useless without knowing the time, or engine rpm.

Power can be calculated using many different units: HP, Watts, kW, PS, Ft lbf/s, KgF m/s, BTU/min, Joules/s.

For engine tuning purposes, the torque curve is much more useful than the power curve.
But horsepower assures bragging rights.

most sensors work by measurment of voltage or such electrical trickery so by your logic you cant even measure forces. so it proves very little

[digger]

No, engines make torque which is the product of force and distance,
which is work.

Not true. Torque (by definition) is force * distance. When we divide torque by time required, we obtain power.
The equation is: P = lbf * ft / sec. Engine revolutions are merely a surrogate for time

force x moment arm is a torque units of Nm
force x distance is work unit is of Nm

these are NOT the same despite the units being the same

work is a dot product in maths/physics (force must be in same direction as displacment)
torque is a cross product in maths/physics (force is perpendicular to moment arm distance)

if a torque is applied but there is no rotation velocity there is no power even if i apply the torque for a period of time

[af2]

Boy did this thread take a turn for the worst....... DCR is and has always been a joke because of the different head designs and the metal they are made of.

[David Redszus]

The risk is hijacking the original thread and getting into an endless debate which solves nothing. You are confusing the definitions of torque and work, which are not the same thing. If you want propel a vehicle power is what is required and therefore not just bragging rights. This particular topic has been discussed endlessly in the past and good information, science, and practical examples have been posted in those threads, you just have to discard the comments with incomplete understanding. I am not interested in another repeat; those threads can be searched, so we need to stop here. If you want some help understanding the engineering you can PM me.

At the risk of offending you, of which have no intent whatsoever, you post useless comments without any added value to the discussion. What I have posted is technically correct, regardless of your opinion, and I certainly do not need engineering lessons from you.

[Ken_Parkman]

Yes you do

[David Redszus]

https://www.grc.nasa.gov/WWW/K-12/airplane/ottoa.html
Not one mention of "torque" on the page.

Your post from NASA is quite insightful. Perhaps you should read it.
If you drill down into the hyperlink "work" you will find the definition of work to be force * distance, or
W = F * D, where force is commonly in pounds and distance is in feet; ergo lbs ft.
Given the same force (F) a change in distance (D) will change the work done.
For work to be done, there must be a distance involved.

Suppose we produce 200 lbf on a lever arm of 2 ft; we would therefore have 400 lb ft of work.
But if the lever arm were only six inches long we would have only 100 lb ft of work even with the
same force in pounds. Now what happens when the lever arm is zero, as in the center of a rotating
shaft? No work is done.

Torque is a force applied to a lever. It has the same units as work because they are the same, as every
physics book clearly indicates. Torque is a measure of work, T = F * D, source Heywood, Fundamentals of Engine
Design (MIT Press).

Power is the RATE at which work is done; it is torque (or work) over time.
P = F * D / t

Since F * D = torque, then P = T / t = F * D /t.

Look at any one of several equations for power, the only inputs are torque and time.

[David Redszus]

most sensors work by measurement of voltage or such electrical trickery so by your logic you cant even measure forces. so it proves very little

That is not correct. Sensors measure forces, such as pressure or strain, and then convert the readings to voltage
outputs which are displayed or recorded in a logger.

Dynos only measure torque and rpm from which we calculate power.
There is no horsepower sensor on a dyno.

If you would like a booklet on how these system actually work, please let me know.