Military History | How To Make War | Wars Around the World Rules of Use How to Behave on an Internet Forum
Fighters, Bombers and Recon Discussion Board
   Return to Topic Page
Subject: One more question:
45-Shooter    5/13/2013 8:58:31 PM
Does anyone here know why smaller recip engines make more power per cubic inch displacement than larger recip engines? Or why larger engines get better fuel economy than smaller engines of the same power?
 
Quote    Reply

Show Only Poster Name and Title     Newest to Oldest
Pages: PREV  1 2 3 4 5 6 7 8   NEXT
45-Shooter       6/28/2013 3:54:55 PM

And that also is foolish.





Bet you did not know that Ford has won more Races than Porsche and Ferrari combined!
 
Quote    Reply

marat,jean       6/28/2013 4:01:48 PM
You incompetent! It has nothing to with work output when measured at the firing impulse!
 
The BMW 801 and the Pratt ad Whitney R-2000 for example.
 
And I NOTE that you know nothing of THIS.




The first part of what you write is OK, but the second part highlighted in yellow above is BS. All recip engines breath the same way! Any simple mechanic knows this. Simple mechs know that reliability is most closely related to Piston speed and is shortened drastically if over 2,800 FPS. The rings limit longevity back then more than now, but are still THE limiting factor. In aircraft and sports/racing engines, particularly in fighter planes of WW-II they some times ignore this in the pursuit of higher performance.
The simple fact is that it is impossible to find two engines of dissimilar size, but equivalent technology that make the same power per unit of displacement.
I note that you fail to answer this last part which was and is the crux of the thread.
 
Quote    Reply

marat,jean       6/28/2013 4:03:58 PM
Also foolish.In what context? Formula 1versus Indy  for example? Stupid. Apples and oranges.
And that also is foolish.




Bet you did not know that Ford has won more Races than Porsche and Ferrari combined!
 
Quote    Reply

45-Shooter       6/28/2013 4:24:37 PM


But not at tracks like Hockenheimring, Spa Francorchamps, Daytona, Indianapolis and the Bonneville Salt Flats where the cars can spend the entire race at or near top speed. I can not remember a single team winning the Manufacturer's Endurance Cup with the DFV?  Not that many tried?  jeepers you are twisted, the dfvs were not eliglible for manufacture cups however I was at Lemans when
Jacky Ickx
won in a dfv powered car (75 check it out)
 I believe you!   
Indy cars were famous for thier 500 miles races but when put against f type jags the engines were found to be lacking in endurance     
I can not remember the "F" Jag ever qualifying at Indy??? who said Indy I said INDY CARS it helps when you read it, it was a one off to compare the two types
That is sort of like, no actually comparing apples to oranges. Not nearly the same thing. 
 I can however, remember helping my Dad rebuild our various Jaguars over the years.  

Colin Chapman one of the worlds best racecar designers had this to say about it    
"The ideal car/engine package will fall apart just after its won the race" in other words if it lasts longer than the race its overengineered     
On the other hand in that exact same vein, nobody expects 73-69% to blow up before the end of the race! 
it was an era of no driver aids so a single missed gear and poof an engine gone, that and these engines were being used to within a inch of their lives every race and you get these things happening, run them slightly less tuned and they would last all day but you will lose to those running less margin - it was a balancing act
 
No recip engine can live that long at maximum load and RPMs, UNLESS it is so over built that there is much excessive reserve power and capacity unused. Sort of like a ZZ-572 with a street cam, EEM and low comp pistons that only makes ~650 HP in a street car with very tall gearing
the point preicely you build for the job its likely to do! and larger capacity gives you that edge but at a cost, over here we used to have production car racing where 1275cc mini coopers raced and often beat 427 cu. inch galaxies
If I get to pick the track, I can absolutely guarantee that my car will beat your whatever every time! Lets see what happens when we try that contest on a longer track with fewer corners? Will your 1275 Mini-Cooper go 170 MPH?
As a separate aside, look up Leonard Vahscholtz to find out what he did with a 427 Ford in the mid 70s.
 
Quote    Reply

marat,jean       6/28/2013 4:29:56 PM
And again he lies about what he has done.
 
Quote    Reply

45-Shooter       6/28/2013 4:30:31 PM

You incompetent! It has nothing to with work output when measured at the firing impulse!
 
The BMW 801 and the Pratt ad Whitney R-2000 for example.
 
And I NOTE that you know nothing of THIS.

How does the ideal gas law relate to Torque or Force with out movement?
But more importantly, how does any of what you have written apply to the topic at hand, namely why do smaller motors produce more power per unit of displacement?
 
Quote    Reply

45-Shooter       6/28/2013 4:31:55 PM

And again he lies about what he has done.
Name one thing!
 
Quote    Reply

45-Shooter       6/28/2013 4:49:39 PM

You incompetent! It has nothing to with work output when measured at the firing impulse!
 
The BMW 801 and the Pratt ad Whitney R-2000 for example.
 
And I NOTE that you know nothing of THIS.

How does the ideal gas law relate to Torque or Force with out movement?
But more importantly, how does any of what you have written apply to the topic at hand, namely why do smaller motors produce more power per unit of displacement?

Given that no one here has posted the simple answer, I will now do so.
Power is directly related to piston crown area and expansion ratio!
Since expansion ratio is fixed over a very narrow range in spark ignition engines, the smaller the engine is, the larger the ratio between piston area and displacement. ( It's a math thing and immutable!)
Displacement is only tangentially related to power. The smaller engine can be spun faster at any given piston speed to make up the difference.
Two engines of identical bore, stroke and nominal configuration have different expansion ratios and thus produce different levels of power and fuel efficiency.

 
 
Quote    Reply

marat,jean       6/28/2013 4:55:28 PM
How does gas expand in a thermal reaction? You know the way an ICE actually works?
 
If I get to pick the track, I can absolutely guarantee that my car will beat your whatever every time!
 
If I smarter than you are, and there is more than ample evidence to prove it just in this thread, then you would know why the IDEAL GAS LAW applies to VOLUME, you ignorant man.
 
I gave you all the clues you needed.
 
 
 
 
 
Quote    Reply

marat,jean       6/28/2013 4:57:28 PM
And that is wrong. Cube not square, you incompetent!
Displacement is only tangentially related to power. The smaller engine can be spun faster at any given piston speed to make up the difference.
Two engines of identical bore, stroke and nominal configuration have different expansion ratios and thus produce different levels of power and fuel efficiency.

 
 
Quote    Reply
PREV  1 2 3 4 5 6 7 8   NEXT



 Latest
 News 		  Most
 Read 		  Most
 Commented		  Hot
 Topics