There is no replacement for displacement
Discussion
300bhp/ton said:
Captain Muppet said:
quiraing said:
Across the same rev-range you could never achieve the same torque from a small hi-spec stressed 1.6 or 3-litre, (or whatever), against maybe a lazy 7.2 V8.
But could you make a 7.1 V8 better than a lazy 7.2 V8? Yes. Thus cliche is wrong.
You can't prove it's true using one bit of data.
Captain Muppet said:
300bhp/ton said:
doogz said:
300bhp/ton said:
But surely a variable inlet manifold isn't allowing more low rpm/revs torque, it just means you don't strangle it once you have it spinning quicker.
No, the clue is in the name.http://en.wikipedia.org/wiki/Variable_length_intak...
ikarl said:
like for like engine, there is no replacement for displacement
Easy enough saying that if you turbo this or supercharge that the engineering can replace the displacement, but if you increase the displacement and then turbo it or supercharge it, you get more
But then if you add a bigger turbo you get more too.Easy enough saying that if you turbo this or supercharge that the engineering can replace the displacement, but if you increase the displacement and then turbo it or supercharge it, you get more
Captain Muppet said:
You only need one bit of data to prove that a statement isn't true.
You can't prove it's true using one bit of data.
I'm not sure saying do something to one engine and not another is really proving a statement isn't true though.You can't prove it's true using one bit of data.
Take the same engine in two different displacements, Rover K Series maybe, 1.6 and 1.8
You can easily get the 1.6 to out perform the 1.8 by doing many of the things cited in this thread. But do those same things to the 1.8 and it will always make more power and torque than the 1.6
There may be alternative tuning methods to attain greater performance, but all other things equal there is no replacement for displacement.
Captain Muppet said:
You only need one bit of data to prove that a statement isn't true.
You can't prove it's true using one bit of data.
The statement, "There is no replacement for displacement" is in the form of an universal negative...And you can't prove an universal negative. You can't prove it's true using one bit of data.
The end.
300bhp/ton said:
Captain Muppet said:
300bhp/ton said:
kambites said:
As I said, the shape of the torque curve, and the responsiveness of the throttle matters; the capacity only matters in how it effects these things and how it effects the weight of the engine.
But how do you significantly affect the torque curve, especially at low rpms without doing something to displacement?It is possible to build an engine with a given limit of capacity that is better than an engine of equal or greater capacity that has a lower level of technology. This disproves that there is no replacement for displacement.
You can also get more out of an engine for a given level of technology by increasing the capacity. Obviously. No one has pretended otherwise.
300bhp/ton said:
Captain Muppet said:
You only need one bit of data to prove that a statement isn't true.
You can't prove it's true using one bit of data.
I'm not sure saying do something to one engine and not another is really proving a statement isn't true though.You can't prove it's true using one bit of data.
Take the same engine in two different displacements, Rover K Series maybe, 1.6 and 1.8
You can easily get the 1.6 to out perform the 1.8 by doing many of the things cited in this thread. But do those same things to the 1.8 and it will always make more power and torque than the 1.6
There may be alternative tuning methods to attain greater performance, but all other things equal there is no replacement for displacement.
Ok think of it this way:
Just pretend you have a 2.5L force fed engine with a bunch of goodies.
Now with all things the same by theory, do you think this 2.5L engine will make the same power as a 5.0L? If all power adders were relatively the same? Why do you think some cars are stroked out? There is no replacement for displacement when it's all said and done. That highly engineered engine can also be advaced by adding cubes. It's all relevant but just my .02
'All other things being equal, a bigger engine makes more power.'
Just pretend you have a 2.5L force fed engine with a bunch of goodies.
Now with all things the same by theory, do you think this 2.5L engine will make the same power as a 5.0L? If all power adders were relatively the same? Why do you think some cars are stroked out? There is no replacement for displacement when it's all said and done. That highly engineered engine can also be advaced by adding cubes. It's all relevant but just my .02
'All other things being equal, a bigger engine makes more power.'
Edited by minime68 on Thursday 21st February 17:02
rb5er said:
But by that rationale:
"All other things being equal, a bigger turbo makes more power."
Really? And whats to say you can't add that same "bigger" turbo to the bigger engine? Who's gonna make more power now? Maybe I don't understand your comment because it's pretty obvious that if you have an engine with a bigger turbo, said engine will make more power up top than the same engine on a smaller turbo. But I said ALL OTHER THINGS EQUAL. "All other things being equal, a bigger turbo makes more power."
minime68 said:
rb5er said:
But by that rationale:
"All other things being equal, a bigger turbo makes more power."
Really? And whats to say you can't add that same "bigger" turbo to the bigger engine? Who's gonna make more power now? Maybe I don't understand your comment because it's pretty obvious that if you have an engine with a bigger turbo, said engine will make more power up top than the same engine on a smaller turbo. But I said ALL OTHER THINGS EQUAL. "All other things being equal, a bigger turbo makes more power."
I was pointing out that there are lots of other ways to increase power and not all include requiring a larger engine.
My post was also saying ALL OTHER THINGS BEING EQUAL.
Yes its quite obvious that if you can ONLY change 1 thing to get more power then that is the ONLY thing that will get you more power.
Yes...if you are only allowed to change the displacement then that is the ONLY way you are going to get more power.
Likewise.... if you are ONLY allowed to change the turbo then that is the ONLY way you are going to get more power.
Or... if you are ONLY allowed to change the supercharger then that is the ONLY way you are going to get more power.
All other things being equal etc.
But the topic is about displacement not bigger turbos. You can say " well a turbo can replace displacement". No it cant. Lets say with a smaller FI engine, you make the same power as bigger N/A engine. The NA engine will have a much better power curve. I'm too lazy to write a whole write-up on it so ill copy and paste this which explains what I'm trying to say.
"There is no replacement for displacement. Let me correct myself: there is one: Cubic dollars. But for everything else, add the cubes.
Displacement rules because in an internal combustion engine produces power by burning fuel and air. The key to gaining more power is simply to add more air and fuel. Because gasoline produces power most efficiently when it is mixed with air at a stochiometric ratio of 16.5 parts of air to one part of fuel, the limiting factor is air. In a normally aspirated engine air is drawn in the engine by the vacuum created during the intake stroke. The larger the engine displacement, the more vacuum produced. It's that simple. More air allows more fuel and more power follows.
One might argue 'what about all that high tech stuff'. Fair enough. When Henry Ford built the famed race car, the 999 he built about a 20 liter engine. It didn't produce half the power of the 2.0liter Zetec in my Ford SVT Focus. Technology does matter, through engine control, fuel metering and breathing. But it isn't fair to compare 1908 with 2002.
Once you have met the minimum standards of engine management met by all modern cars the key issue again returns to breathing, the ability to flow air in and out of the engine. You can improve breathing by smoothing air flow in and out of the engine, and by increasing valve area. The second way is to simulate a larger displacement through pushing more smaller cycles through the engine, in essence by out-revving the other engine.
Smoothing air flow in and out of the engine can be done to both 'low tech' overhead valve and the higher tech.overhead cam motors. The key is good exhaust, intake and port design. The supposedly 'low tech' motor in a 2004 Z06 Corvette produces a very reliable 71hp per liter, and impressive total for any streetable engine, and does so with thumping torque at any engine speed. If you spend more money engineering a lower tech, lower production cost solution to perform very well indeed. Yes, a twin cam motor could do better. But it would cost a lot more, and the DOHC cylinder head is very wide. The small block OHV -V-8 is a very compact piece for the power produced.
Let's now look at out-revving the low tech engine. A standard detroit V-8 is good to 6,000 RPM, right now, and many are good to 7,000. Racing variants can be reliable up to about 8,500 RPM. An racing overhead cam engine can go to 14,500 which is significantly more. But there are some caveats. The biggest of which concerns the cost of parts.
As an engine revs higher a factor known as piston speed comes into play. Internal combustion engines have a lot of reciprocating mass. Piston speed is a good measure for how fast the internal, reciprocating bits are moving. The main revving limitation of a 'low tech' overhead valve engine is the lifter/pushrod system which has a lot of reciprocating mass the overhead cam motor avoids. Fair enough. But as you rev higher piston speed becomes a very large factor. In any motor, once you pass 7,000 RPM you start to need special internal parts. The crankshaft on the Honda S2000 is a really slick piece, whose bearing surfaces cannot be touched by human hands, lest they be damaged. These pieces aren't cheap, and once you start putting them in then the old fashioned V-8 starts revving pretty high as well. The overhead cam engine still enjoys an advantage, but you have to rev it stupid high to obtain said benefits. That may not be enough to overcome any displacement disadvantages.
What about supercharging? Vacuum is more about air being pushed in to the cylinders and at one atmosphere only so much air goes in. Superchargers mechanically force more air in, in effect creating a bigger engine. The supercharger is limited by design. Turbochargers use a waste gate to limit how much boost they can attain. Cars like the Mitsubishi Eclipse can gain big power cheaply simply by reprogramming the waste gate to a higher pressure.
The big, low tech, motor enjoys one big advantage; torque. Big motors produce lots of it, and produce torque practically everywhere. Small motors can produce torque, but in a much narrower rev band. Small motors make their power higher up in the rev band, which makes the torque harder to use. Big motors are easier to drive. They are more flexible.
But to produce really significant gains over the normally aspirated, overhead valve motor, you have to spend a lot of money. Money for more expensive parts. Money for more advanced assembly techniques. Any modification you can do to a small motor, say Nitrous oxide injection or supercharging, can also be done to a big, low tech motor with equal results. Ask John Hennessey. I've seen on a race track what a couple turbos and some smart modifications can do to Dodge Viper. The fastest, most highly modified, high-tech Civics are nothing more then roadkill. In fact, we try not to let them on track together because the mismatch is so ugly.
All things being equal, the high tech motor does beat the lower tech motor. But all things are never equal. I like small nimble cars, that's what i drive, and what I raced. But the sledgehammer works. Anyone who races uses the largest engine they can."
"There is no replacement for displacement. Let me correct myself: there is one: Cubic dollars. But for everything else, add the cubes.
Displacement rules because in an internal combustion engine produces power by burning fuel and air. The key to gaining more power is simply to add more air and fuel. Because gasoline produces power most efficiently when it is mixed with air at a stochiometric ratio of 16.5 parts of air to one part of fuel, the limiting factor is air. In a normally aspirated engine air is drawn in the engine by the vacuum created during the intake stroke. The larger the engine displacement, the more vacuum produced. It's that simple. More air allows more fuel and more power follows.
One might argue 'what about all that high tech stuff'. Fair enough. When Henry Ford built the famed race car, the 999 he built about a 20 liter engine. It didn't produce half the power of the 2.0liter Zetec in my Ford SVT Focus. Technology does matter, through engine control, fuel metering and breathing. But it isn't fair to compare 1908 with 2002.
Once you have met the minimum standards of engine management met by all modern cars the key issue again returns to breathing, the ability to flow air in and out of the engine. You can improve breathing by smoothing air flow in and out of the engine, and by increasing valve area. The second way is to simulate a larger displacement through pushing more smaller cycles through the engine, in essence by out-revving the other engine.
Smoothing air flow in and out of the engine can be done to both 'low tech' overhead valve and the higher tech.overhead cam motors. The key is good exhaust, intake and port design. The supposedly 'low tech' motor in a 2004 Z06 Corvette produces a very reliable 71hp per liter, and impressive total for any streetable engine, and does so with thumping torque at any engine speed. If you spend more money engineering a lower tech, lower production cost solution to perform very well indeed. Yes, a twin cam motor could do better. But it would cost a lot more, and the DOHC cylinder head is very wide. The small block OHV -V-8 is a very compact piece for the power produced.
Let's now look at out-revving the low tech engine. A standard detroit V-8 is good to 6,000 RPM, right now, and many are good to 7,000. Racing variants can be reliable up to about 8,500 RPM. An racing overhead cam engine can go to 14,500 which is significantly more. But there are some caveats. The biggest of which concerns the cost of parts.
As an engine revs higher a factor known as piston speed comes into play. Internal combustion engines have a lot of reciprocating mass. Piston speed is a good measure for how fast the internal, reciprocating bits are moving. The main revving limitation of a 'low tech' overhead valve engine is the lifter/pushrod system which has a lot of reciprocating mass the overhead cam motor avoids. Fair enough. But as you rev higher piston speed becomes a very large factor. In any motor, once you pass 7,000 RPM you start to need special internal parts. The crankshaft on the Honda S2000 is a really slick piece, whose bearing surfaces cannot be touched by human hands, lest they be damaged. These pieces aren't cheap, and once you start putting them in then the old fashioned V-8 starts revving pretty high as well. The overhead cam engine still enjoys an advantage, but you have to rev it stupid high to obtain said benefits. That may not be enough to overcome any displacement disadvantages.
What about supercharging? Vacuum is more about air being pushed in to the cylinders and at one atmosphere only so much air goes in. Superchargers mechanically force more air in, in effect creating a bigger engine. The supercharger is limited by design. Turbochargers use a waste gate to limit how much boost they can attain. Cars like the Mitsubishi Eclipse can gain big power cheaply simply by reprogramming the waste gate to a higher pressure.
The big, low tech, motor enjoys one big advantage; torque. Big motors produce lots of it, and produce torque practically everywhere. Small motors can produce torque, but in a much narrower rev band. Small motors make their power higher up in the rev band, which makes the torque harder to use. Big motors are easier to drive. They are more flexible.
But to produce really significant gains over the normally aspirated, overhead valve motor, you have to spend a lot of money. Money for more expensive parts. Money for more advanced assembly techniques. Any modification you can do to a small motor, say Nitrous oxide injection or supercharging, can also be done to a big, low tech motor with equal results. Ask John Hennessey. I've seen on a race track what a couple turbos and some smart modifications can do to Dodge Viper. The fastest, most highly modified, high-tech Civics are nothing more then roadkill. In fact, we try not to let them on track together because the mismatch is so ugly.
All things being equal, the high tech motor does beat the lower tech motor. But all things are never equal. I like small nimble cars, that's what i drive, and what I raced. But the sledgehammer works. Anyone who races uses the largest engine they can."
currybum said:
TameRacingDriver said:
cspan said:
Question: if I gave you a 1.0 turbocharged 3 cylinder and an NA V6, with similar outputs and dyno curves, do you think you'd have a preference for one over the other?
I would. And it would be the V6 every time for driving pleasure. However, as an every day car, I'm not so sure it would be.Captain Muppet said:
Cheburator mk2 said:
Hmm, let's see... the ORECA Le Mans cars as well as the Zakspeed N-ring 24hrs were around 620bhp... nigh on 40% more... consider they had to have restrictors too...
To get 40% more power the displacement did not increase by 40%.An engine is an air pump - more air = more power. Large displacement is an easy and cheap way of getting more air in - but not the most fuel efficient way.
Captain Muppet said:
It is possible to build an engine with a given limit of capacity that is better than an engine of equal or greater capacity that has a lower level of technology. This disproves that there is no replacement for displacement.
Curious, but how does it disprove it?I just don't understand how this isn't simply an alternative, rather an replacement?
300bhp/ton said:
I just don't understand how this isn't simply an alternative, rather an replacement?
I don't think I understand the difference in definition between the word "alternative" and "replacement" in this context? I'd say they are synonyms. Increasing displacement is just one way (among many) of increasing the amount of air that enters your combustion chambers per unit time. Saying "there is no replacement for displacement" is no more or less true than saying "there is no replacement for turbo-charging" or "there is no replacement for adding hybrid drive components".
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