Yep , sorta proves what a purpose build makes.
How does cid make power?
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Ironracer
Gearhead
Exactly the point of my Asking, Sir!
Cheapsunglasses
In rust we trust!
Well smog 440s are what, 200hp and 480ftlbs. Vs their muscle car 6 pack (barrel if Plymouth lol) brother that made 390hp and same torque.
67autocross
A new iron curtain drawn across the 49th parallel
****….now I have to spend the whole evening trying figuring out why my Yamaha YZ 250 2 stroke is faster than the YZ 125 sitting beside it…
Kind of my point a different displacements somewhat guaranties a certain amount of torque but hp could be very low to high, building a 440 doesn't guarantee more power than smaller engines like it somewhat does with torque.
If hp was tied yo cid the hp per cid range would be smaller.
Cheapsunglasses
In rust we trust!
Is that so, well la dee da. lol
I saw through all the bullshit before it began and simplified. lol
Rat Bastid
Dunamis Metron
Rat Bastid
Dunamis Metron
What you should be thinking about is why a 250 2T makes more power than a 250 4T. Which is exactly why AMA and the morons running dirt bike racing make a 250 2T run with 450 4T’s.
That’s what you should be considering.
Yea it's pretty simple start with 500 cubes and go from there.
I have just the induction system for it. lol
67autocross
A new iron curtain drawn across the 49th parallel
Well in Canada we could at least until recently run a 250 smoker in the 250cc class…but it had to be stock internally and in pro class…wait for it…you had to be a Canadian citizen…no BS
B3422w5
Well-Known Member
yep..
Good example would be mountain motor pro stock engines compared to pro stock engines
500 cubes vs 900 cubes, but only about 3 tenths or thereabouts difference in the 1/4…..
There's a lot of reason to start with larger cid especially since most of us don't want to spin our engines to the moon but doesn't automatically give an hp advantage say to 500 over a 400 cid engines with especially with same bore.
Most the V8 builds you look at use similar parts to archive a certain hp eg.. 500 hp
Don't matter if your talking a 289 Ford, 350 Chev or a 440 Mopar etc... Not like the 289 gonna need a 100 cfm more head flow and 80 degrees more cam etc.. Than a 440 for same power. But yes the powerbands are gonna be very different.
Don't matter if your talking a 289 Ford, 350 Chev or a 440 Mopar etc... Not like the 289 gonna need a 100 cfm more head flow and 80 degrees more cam etc.. Than a 440 for same power. But yes the powerbands are gonna be very different.
dusterbing the peace
FABO pyrite member
Fuel, gasoline for these motors, has a BTU/lb rating of 11,500-13,000 typically. BTU/hr is a unit of power, readily converted to horsepower: 1 hp = 2,544.4 BTU/hr.
The more fuel you can get in the motor, the more power you can get out (to the limit of efficiency for the particular motor). You need air to burn the fuel, which is where air to fuel ratio comes in. You’ve probably heard numbers like 12.8, which simply means 12.8 parts air to one part fuel.
The more cubic inches displacement, the more fuel and air can be burned. Some of the examples being thrown around comparing 440 ratings are simply a difference in volumetric efficiency of the motor. A well built small block will out power a crappy big block all day, because the small block is extracting the energy from the fuel better than the big block. If the same design parameters were applied to the build of the big block it would win, simply because it has more fuel going through it.
In this regard, it is easier to burn more fuel with less build effort from a big block.
Let’s do 500hp
That takes 1,272,217 BTU/hr of fuel. If we use good gas with 13,000 BTU/lb energy, we need 97.9 lb/hr…but that’s at 100% thermal efficiency. A gasoline engine is closer to the low 30s percentage wise for thermal efficiency. So at 35% thermal efficiency we need 279.6 lb/hr fuel flow. At 12.8:1 AFR we then need 3,579 lb of air which ends up at 739 CFM. That is a 340 at 7,512 rpm, or a 440 at 5,805 rpm…or for the earlier example, 100 cid at 25,541 rpm. And those are at 100% volumetric efficiency…I’m done doing math and don’t feel the need to give examples of higher or lower values there.
Which one sounds easier to build?
The more fuel you can get in the motor, the more power you can get out (to the limit of efficiency for the particular motor). You need air to burn the fuel, which is where air to fuel ratio comes in. You’ve probably heard numbers like 12.8, which simply means 12.8 parts air to one part fuel.
The more cubic inches displacement, the more fuel and air can be burned. Some of the examples being thrown around comparing 440 ratings are simply a difference in volumetric efficiency of the motor. A well built small block will out power a crappy big block all day, because the small block is extracting the energy from the fuel better than the big block. If the same design parameters were applied to the build of the big block it would win, simply because it has more fuel going through it.
In this regard, it is easier to burn more fuel with less build effort from a big block.
Let’s do 500hp
That takes 1,272,217 BTU/hr of fuel. If we use good gas with 13,000 BTU/lb energy, we need 97.9 lb/hr…but that’s at 100% thermal efficiency. A gasoline engine is closer to the low 30s percentage wise for thermal efficiency. So at 35% thermal efficiency we need 279.6 lb/hr fuel flow. At 12.8:1 AFR we then need 3,579 lb of air which ends up at 739 CFM. That is a 340 at 7,512 rpm, or a 440 at 5,805 rpm…or for the earlier example, 100 cid at 25,541 rpm. And those are at 100% volumetric efficiency…I’m done doing math and don’t feel the need to give examples of higher or lower values there.
Which one sounds easier to build?
33IMP
Well-Known Member
This is amazing. You were arguing with me on this and now your asking questions on it.
This is part of the problem right here.
“theoretically” is what your going on.
When you actually do stuff, like build your own engines and sit down and think about camshaft selection, without a doubt, when you actually do this, you will learn something.
Putting an289 top end on a 400?
Ain’t much crazier than that.
Then again, there was that dynamic duo that figured they could port there heads while the engine was running by dumping sand into the intake and rev’ed it up.
So you think based on the “theoretically.”
“Theoretically.” Right?
In some case your limiting the two engines by the same top end. If you increase the displacement then be an equal percentage you should increase everything else to match.
On a twin bore size engine, the stroke makes different displacements. What are we talking about here?
A .040 inch over 360 vs a 040 hour ver 360 w/ 4 inch stroke?
Engine masters did this test. The stroker made huge torque over the 360 and at the max power output, only a few hundred rpm’s down, just a couple of hp.
I think the episode was “Stock vs stroked.”
On a twin bore size engine, the stroke makes different displacements. What are we talking about here?
A .040 inch over 360 vs a 040 hour ver 360 w/ 4 inch stroke?
Engine masters did this test. The stroker made huge torque over the 360 and at the max power output, only a few hundred rpm’s down, just a couple of hp.
I think the episode was “Stock vs stroked.”
Ironracer
Gearhead
I've got some family up there somewere, but I'd have to borrow the bike and hitch a ride up there...
Another Excellent example!
I'm waiting for someone to prove you right, still waiting
Does theory get you 100% of the way no but it's always s good starting point.
Rat Bastid
Dunamis Metron
That’s a bad example. How do you compare two engines which have a huge difference in bore spacing? You can’t.
As I posted earlier, you have to compare engines with similar architecture. Otherwise you’ve wasted your time and didn’t learn a thing.
Ironracer
Gearhead
[QUOTE="rumblefish360, post: 1974035417, member: 1189" [Then again, there was that dynamic duo that figured they could port there heads while the engine was running by dumping sand into the intake and rev’ed it up.QUOTE] there IS an old Dutch or Swede Motorcycle Racing trick to seat rings, sometimes called "Huff and Puff" basically you take spoonfuls of Dutch Master, or other powdered cleaners and blow em in the carb while Turning the throttle. Works Killer! I've even heard of people whose Rings failed to seat use it to get them to seat. Now about that Sand to port Heads,cut new valve seats, and regrind cranks, setting new cam bearing clearances? Does it clean the oiling system too? (EVIL GRIN INCLUDED)
But that not the question we all know the benefits of displacement especially in a street car.
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