That's like your opinion man
Maybe were looking from the same from you.
It's not instance hp cause your not factoring in stroke or displacement depending on the eg..
This formula has nothing really to do with what were talking about lol.
Here you go, Piston area and force.
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Well, I don't have any skin in this, but I deal with high pressure pumps daily, and I can assure you the greater area increases the force on the bearing. That is why we have to decrease piston size for higher output pressures. To save the bearings. The best way I describe this to people is PSI. Pounds Per Square Inch. More inches = more pressure / force against the bearing.
71340
Well-Known Member
Just for clarification, going from a 4" piston to 5" piston is a 36% change not more than 50% as stated.
4" piston equals 12.56" in area 5" piston equals 19.63" in area, 12.56 divided by 19.63 equals .64 (minus the .64 from .100 to get the .36 (36%)
4" piston equals 12.56" in area 5" piston equals 19.63" in area, 12.56 divided by 19.63 equals .64 (minus the .64 from .100 to get the .36 (36%)
Newbomb Turk
Well-Known Member
I'll say it again, it's PLAN, where;
P= Pressure (average) in the cylinder
L= Length of stroke
A= Area of the piston is square inches
N= Number of cylinders
How simple is this^^^^^^???
You have FOUR and only FOUR ways to make more power. Obviously you can put it on the hose or add a hair dryer or three, but this specifically addresses what you can do with your basic components.
If you want to make more power, you can change or modify any or all of the above four parameters.
If you can do simple algebra, you can easily SEE that increasing the area of the piston will make more power.
To sum it up, if you want to make more power you can increase the pressure (by any means such as higher compression ratio, power adders...whatever), or you can increase the length of the stroke, or you can increase the SIZE OF THE BORE or you can increase the number of cylinders.
That's IT. You can make everything the same and make the bore bigger and it will make more power.
Make the bore smaller, lose power.
Claiming a smaller bore will make more power is 100% buuuuuuuuuull squirt.
P= Pressure (average) in the cylinder
L= Length of stroke
A= Area of the piston is square inches
N= Number of cylinders
How simple is this^^^^^^???
You have FOUR and only FOUR ways to make more power. Obviously you can put it on the hose or add a hair dryer or three, but this specifically addresses what you can do with your basic components.
If you want to make more power, you can change or modify any or all of the above four parameters.
If you can do simple algebra, you can easily SEE that increasing the area of the piston will make more power.
To sum it up, if you want to make more power you can increase the pressure (by any means such as higher compression ratio, power adders...whatever), or you can increase the length of the stroke, or you can increase the SIZE OF THE BORE or you can increase the number of cylinders.
That's IT. You can make everything the same and make the bore bigger and it will make more power.
Make the bore smaller, lose power.
Claiming a smaller bore will make more power is 100% buuuuuuuuuull squirt.
Amount of cylinder pressure psi is how efficient your engine is, they say it's around 1000 psi for a normal average efficient engine to 1500 psi for a efficient race engine to 1600/1700 psi for a highly developed engine like pro stock.
Lbs-ft per cid ranges say from one, I imagine you can go lower but most engines seem to make at least 1 lbs-ft per cid to as high as 1.65-7 lbs-ft is around what the highest NA gasoline engines can do so basically a 1000 - 1700 ish psi, Bmep basically telling the same thing.
So take a Mopar 383 B vs 383 RB same displacements, should be able to build each to similar hp at a similar efficiency level say 1.25 lbs-ft per cid (479) tq, let's say that's around 1250 psi. The B will have more force from the larger piston area but have less stroke to multiply that force to make 479 tq the RB will have less force from it's piston area but will have more of a multiplying effect for 479 tq.
So ideally both of these engines should be able to make basically the same torque obviously there's scenarios where they won't.
Also take a basic 500hp/500tq 408 1.23 lbs-ft per cid now it's possible to get those numbers out of 360 just got to step up your efficiency game to 1.37 lbs-ft per cid and should make the power and torque around the same rpms. Since the 360 has the same bore but less stroke obviously there's a lot more cylinder pressure happening to do so.
For torque amount in the end of the day lbs-ft per cid is more important than how you made that cid.
Lbs-ft per cid ranges say from one, I imagine you can go lower but most engines seem to make at least 1 lbs-ft per cid to as high as 1.65-7 lbs-ft is around what the highest NA gasoline engines can do so basically a 1000 - 1700 ish psi, Bmep basically telling the same thing.
So take a Mopar 383 B vs 383 RB same displacements, should be able to build each to similar hp at a similar efficiency level say 1.25 lbs-ft per cid (479) tq, let's say that's around 1250 psi. The B will have more force from the larger piston area but have less stroke to multiply that force to make 479 tq the RB will have less force from it's piston area but will have more of a multiplying effect for 479 tq.
So ideally both of these engines should be able to make basically the same torque obviously there's scenarios where they won't.
Also take a basic 500hp/500tq 408 1.23 lbs-ft per cid now it's possible to get those numbers out of 360 just got to step up your efficiency game to 1.37 lbs-ft per cid and should make the power and torque around the same rpms. Since the 360 has the same bore but less stroke obviously there's a lot more cylinder pressure happening to do so.
For torque amount in the end of the day lbs-ft per cid is more important than how you made that cid.
remytherat
Well-Known Member
Not how math works. 4 to 5 is a 56% change in area (1.25 squared)
Ant
Well-Known Member
I have to refer this question to my wife, I already know the effect of a stroker. lol
OK, the bigger the piston the more power, add some stroke a make some real horsepower.
That kinda doesn't sound right. I always thought stroker = torque.
There are three kinds of people in this world.
Those who are good at math.
And those who aren't.
Yea you're right, the longer stroke does increase torque. let me check to be sure.
Basically
Displacement, how well you can fill it and how effectively can you change the fuels potential into rotational force per power stroke which is torque, hp is how many power strokes (torque) a minute (time) you can squeeze in (rpm).
Displacement, how well you can fill it and how effectively can you change the fuels potential into rotational force per power stroke which is torque, hp is how many power strokes (torque) a minute (time) you can squeeze in (rpm).
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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19.63/12.56= 1.563, equals an increase in area of 56.3%
IDK what your numbers are doing.......
except that 12.56/19.63 which is going the wrong way. We are looking at an increase, not the inverse.
Ant
Well-Known Member
Bigger bore = more power. I agree, that's why we have big bore kits for motor bikes and atvs. Bigger bore and piston squeezes a larger mixture of air and fuel which then makes a bigger bang and pushes the piston and con rod down harder with more energy.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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That only works if the induction system is able to simultaneously pass more air. And a big part of the increase is the larger Swept volume which increases the SCR.
What I mean is this, you can put a 5" piston on your pushmower, but good luck even starting it with that lil rope starter.. lol
dusterbing the peace
FABO pyrite member
The 36% increase from @71340 is correct:
(19.63-12.56)/19.63 = 0.36
12.56/(1-.36) = 19.63
Let’s say that the tunes were matched somehow in the two different bores and everything else remained unchanged:
1,000 lbs/si * 19.63 si = 19,630 lbs force
1,000 lbs/si * 12.56 si = 12,560 lbs force
This is still a 36% increase in force on the piston:
(19,630-12,560)/19,630 = 0.36
The trick is to get the same, if not greater, explosion force out of the larger bore. This is somewhat easier to do when boring an engine for a rebuild, however the net change is far less…4.00 to 4.03 is only 1% increase (when rounding up).
Ant
Well-Known Member
Maybe I should four barrel swap the lawnmower lol.
This discussion is not including all that, but yet, taking for granted that the induction system can indeed handle any extra bore. In other words, we're basically talking about the short block.
jos51700
Green Bearing thread connoisseur
Um yeah, it kinda is.
jos51700
Green Bearing thread connoisseur
Pressure is in pounds per square inch, psi.
Literally, force per area
100 psi across ten square inches is 1000 pounds of force.
100 psi across twenty square inches is 2000 pounds of force.
The tricky part is increasing the area without decreasing the pressure.
Literally, force per area
100 psi across ten square inches is 1000 pounds of force.
100 psi across twenty square inches is 2000 pounds of force.
The tricky part is increasing the area without decreasing the pressure.
In my mind's eye, the bore changes we're discussing here, let's just give an example.....say going from a 4.250 bore of a 383 to a 4.342 of the 400 isn't enough of a difference to "undo" the added power of the larger bore, if that makes sense. While the pressure "may" decrease from the smaller bore to the larger, (and I'm not certain it does), it's not a large enough amount so as the larger bore of the 400 loses power. To me, that's a great example too, since the 383 and 400 share everything else in common BUT the bore size. Lets just say their compression is the same at 9.5 and the rest of their builds are also the same. The 400 wins every time and the only difference IS the bore size.
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