600hp mkiii vs 07 zo6

[SySt]

The HP/L comparison seems to be one of the most common misconceptions in the automotive enthusiast groups. I have been trying to hit this topic all day with you. The fact that one engine makes more HP/L carries no weight. It does not mean your engine is working better or more efficiently. Lets put it this way, if I have an engine that makes more power with the same fuel as another engine. It does not matter how much displacement the engine has, my engine still runs more efficiently and is therefore a better combination.

Displacement has nothing to do with engine efficiency or performance.

 

[mdr40z]

since the internal combustion engine is an inherently wasteful beast (iirc in the range of 15-30%) the hp/l analysis is everything, it's all about using as much of the available energy from the fuel as possible, the original energy source in the engine is the chemical potential energy of the fuel.
more horsepower/liter = more efficient use of available fuel.
btw, the technology already exists to at least double to hp/l kind of originating at the lowly VTEC to now quite complex HCCI, I'd love to see OPEC have to do some scrambling. Of course it's expensive but when you consider the cost of an Iraq war....

 

[supra1]

The HP/L comparison seems to be one of the most common misconceptions in the automotive enthusiast groups. I have been trying to hit this topic all day with you. The fact that one engine makes more HP/L carries no weight. It does not mean your engine is working better or more efficiently. Lets put it this way, if I have an engine that makes more power with the same fuel as another engine. It does not matter how much displacement the engine has, my engine still runs more efficiently and is therefore a better combination.

Displacement has nothing to do with engine efficiency or performance.

???

mdr40z has it spot on. hp/litre is a VERY meaningful way of finding out the efficiency of an engine. When two engines are compared together using this method it is assumed they are both using pump fuel and are both naturally aspirated

Lets put it this way, if I have an engine that makes more power with the same fuel as another engine. It does not matter how much displacement the engine has, my engine still runs more efficiently and is therefore a better combination.

Displacement has nothing to do with engine efficiency or performance.

Its hard to even correct such rubbish, but,
lets put it this way. There are two engines.

one is a 2 litre , it makes 200hp at the crank on pump gas

my other engine is a 7litre ~ big block.

It makes 500hp at the crank using pump gas.

My first engine makes 100hp per litre (a very respectable amount indeed)

My second engine makes 71 hp/ litre

Therefore meaning my first engine, the 2 litre one is much more efficient.

 

[SySt]

You guys just do not get it do you? Displacement has very little to do with how air, and therefore fuel is being pumped through the engine. You can rate efficiency by HP/CFM, but HP/L is absolutely useless.

Lets take two 2L engines.
The S2000 engine makes what, 240HP? It also making that peak number over 8k RPMs right? Now another 2L engine may be making 180HP but it's peak may be at around 5.5k RPMs. The S2000 engine will have a higher HP/L number. The only reason it has a higher HP/L number is because it is flowing more air because it is at higher RPMs, that also means it is using more fuel. However, the HP/CFM of both engines may be the same.

 

[mdr40z]

what I'm sure you understand is that hp/l is the measuring stick, we may be actually saying the same thing tho it's just that hp/l is easily definable and a practical, useful means of quantifying output. Sure you could perform bench testing with a stack of instruments and determine hp/cfm on each engine but real world? Impossible to achieve.
I guess a better stick might be hp/l/liter of fuel. I guarantee that in the example of 2l engines listed above the higher hp/l engine is also the highest hp/l/liter fuel, better (read, more efficient) design.
Design is totally another animal all together, diesels run what about 40hp/l but with generally more torque/l, gas engines typically 60-120hp/l with all of the upper end being a variable valve time type design and typically closer to square hp/tq. This is why the number is important, given the terribly inefficient design of 90% of the ice the better design typically produces better hp/l ratio, sure it flows more but it also uses more of the energy available from the unit of fuel. You seem to imply that an engine of 60hp/l doesn't use any more fuel/hp than a better design of 120hp/l, that is simply not true, at whatever cfm. Higher hp/l is just generally better design/engineering.
The other 'standard', and perhaps better, indicator of performance is, of course, hp/lb because it more accurately relays the real world, seat of the pants feel. But alas, it is also flawed in your 'scientific' method because there are too many variables to consider which, coincidently, gets us full circle to the purpose of the thread doesn't it?

 

[SySt]

If HP/L is what measures engine efficiency, then you are claiming a LOT of two stroke engines are WAY more efficient than pretty much any car engine. Yet, those two stroke engines consume more oil and get worse fuel economy. Ok, you may say that a 2-stroke has twice the power strokes at the same given RPM as a 4-stroke. How does that change it's HP/L? It doesn't. What it does change is the amount of air/fuel flowing into the engine. 2-stroke engines are not fuel efficient. They will tend to have high HP/L numbers but lower HP/CFM numbers, thus they are less efficient.

At any rate, if that does not convince you of how pointless a figure HP/L is. You can visit this thread: http://www.ls1tech.com/forums/showthread.php?t=724636 That thread has a lot of good information in it once you sift through the opinions of some of the users.

 

[Doward]

Oh wow. There are very few on LS1Tech that know their dick from a wrench.

I'm not even joking. :3d_frown:

You guys are arguing about two different things. Volumetric efficiency vs thermal efficiency.

EITHER is a very valid method of comparing two engines.

/thread.

 

[mdr40z]

At any rate, if that does not convince you of how pointless a figure HP/L is.

I'll say it once more then I'm out........

'that hp/l is the measuring stick, hp/l is easily definable and a practical, useful means of quantifying output. Sure you could perform bench testing with a stack of instruments and determine hp/cfm on each engine but real world? Impossible to achieve.
I guess a better stick might be hp/l/liter of fuel'

VE on mass-produced passenger cars is "Impossible to achieve" practically

 

[TurboStreetCar]

Its useless, ive tried and given up, he cant seem to understand that making more horsepower per liter directly equals a more efficient use of displacement.

When you measure horsepower, your at full throttle, who is concerned with fuel economy at full throttle? No one cares about fuel economy, the entire point of making horsepower is to cram as much air and fuel in the right mixture into the cylinder. If i get more air and fuel in the right ratio into my liter of displacement then you do, and i make more horsepower, im using my displacement MORE EFFICIENTLY TO MAKE POWER then you are.

lets see, to make power, you need Air and fuel inside a cylinder that undergoes compression and ignition. To make more power (in the same displacement engine) i need to use more fuel and air. Now obviously if my engine is more efficiently using its displacement its consuming more fuel and air per liter then yours.

Two strokes have higher HP/liter becasue hmm lets see......THEY MORE EFFICIENTLY USE THERE DISPLACEMENT TO MAKE HORSEPOWER. They make more horsepower per liter BECAUSE they consume more fuel. Where do you think that extra fuels is going? evaporating? draining out the "extra fuel port" onto the ground? Its bieng burned.

Diesels have lower hp/liter because they Dont efficiently use displacement to make horsepower, they use there displacement and by design are Low rpm Torque bearings engines. They consume less fuel, because they make less power. They can do alot of work, but not very fast. if they did the same work fast, horsepower (per liter or as a whole) would rise and so would fuel consumption.

And thats all for me.

 

[Wiisass]

There are so many different factors of an engine that none will really tell you the whole story. Especially when you're comparing an NA engine and a turbo engine. HP/L just doesn't tell you the whole story. It only tells about peak power and nothing else about the engine performance.

When it comes down to it, it seems that although Hp/L can be used as some sort of comparison, it's usually what people say when they have a smaller motor making less power. The only time I've seen it used in industry is to compare a previous generation engine to the next one. It could be used lots of other places but I haven't seen it or it hasn't stood out. And I'm not talking in stuff like Sport Compact car or Super Street, I'm talking real automotive engineering magazines. And it has always seemed like a benchmark number rather than a value with real meaning. Engineers have a lot of other efficiencies and design parameters to consider and the Hp/L seems to be what powertrain engineers will use to describe the performance to non-engineers. Because it's a simple concept.

If you really want a real world comparison of how an engine uses it's power, then compare horsepower to weight. Define weight as either the longblock or the full engine or whatever you want, just make it the same across the board. That will give you a better idea of how the engine will perform. Or even just comparing area under the curves, that will tell you more about it's potential than just peak numbers.

Just remember that the engine does more than make peak power and that's where everything else comes into play. That would be like comparing cars just by top speed and then claiming one was better. It could take one car 5 minutes to get up to 200mph and another car 30 seconds to get to 180mph and people would claim that the car that can hit 200mph is faster because it's moving at a higher rate of speed.

Tim

 

[TurboStreetCar]

Just remember that the engine does more than make peak power and that's where everything else comes into play. That would be like comparing cars just by top speed and then claiming one was better. It could take one car 5 minutes to get up to 200mph and another car 30 seconds to get to 180mph and people would claim that the car that can hit 200mph is faster because it's moving at a higher rate of speed.

Tim

The 200mph car is faster, the 180mph car is quicker. :biglaugh:

 

[SySt]

Ok, so what you are saying is "your" engine makes a better use of it's volume than "mine"? What point does that have? It doesn't matter for ANY purpose. That says nothing about how much power an engine produces or how efficiently it runs. I mean, you can compare HP per seat in a car as well. That doesn't give you anything useful either.

Lets take two engines, one makes power peak at 4k RPMs the other at 8K RPMS. The lower RPM engine is 4L, the higher is 2L. Guess what, they both have the same DYNAMIC displacement. Even comparing dynamic displacements of two motors is pointless.

When will the whole automotive world get that displacement has little to do with power production and fuel efficiency.

I guess my question here is this: Why do you even care how much HP/L an engine makes?

 

[Ma70.Ent]

I'm going to have to let this one die too.

Closed.