I just wanted to make sure I have this right in my brain.

Both will be N/A and maybe a 75 shot.
First engine:

• Low revving engine
• Long piston stroke
• Mid to low size piston bore
• Midsized TB and exhaust, & mild porting
• High compression

Higher torque motor?

Secound engine:

• High revvingng engine
• Short piston stroke
• Large toMidsizede piston bore
• Large TB and exhaust, & fully built head
• High compression

Higher horsepower motor?
Which would be faster in quarter-mile. All the rest of the engine and trans components the same, or which would be better suited for the drag strip. I personally like motor one better, because I love the torque my LD9 has compaired to some of my friends cars.



PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO

well it really depends how the cars get off the line , and how effecently they build the power

i can only use this for a reference , a 383(4.030 bore x 3.75 stroke) small block is a low rpm high tq motor , the 377(4 1/8 bore x 3.48 stroke) is a high rever

in the same car the 377 was quicker , it got off the line better and pulled through the rpm faster , the 383 beat it 1/8 mile , but 1/4 the 337 was ahead by a few tenths and several mph

each car is different as is each motor combo

i love the 2.4 and its grunt , but the smoothness of the eco power band is very nice too

Eric thanks for the info man. I just wanted to get it clear in my head.



PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO

If you want torque, go big bore on the pistons. It's not all about stroke.


Gilles
2.3 Ho

Mfk-223 wrote:If you want torque, go big bore on the pistons. It's not all about stroke.

Can you explain a little more...



PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO

Displacement = 3.1416 / 4 * (bore * bore) * number of cylinder

A good example would be the 2.3 VS the 2.4 ( Ld2 Vs Ld9).

2.3 = 160hp, 150lbs = 3.62 bore and 3.35 stroke

2.4 = 150hp, 150lbs = 3.54 bore and 3.7 stroke

More bore = more displacement, more stroke = more displacement, there's no replacement for displacement.

The limiting factor in revolution is the stroke. So a long stroke and a big bore will give you alot of displacement and alot of torque down low.



Gilles
2.3 Ho

A longer stroke gives a longer lever arm which is what gives a motor more torque. A larger bore on a shorter crank will do the same.

Torque = Force*Distance (In this case, distance from the center of rotation)

The reason you have less horsepower with a longer stroke towards the top end is because you have a dipole with greater rotational inertia.

So like Gilles said, don't shy away from a large bore on a stroker. The physical power in the combustion chamber of two motors of the same same bore and dynamic compression ratio but different stroke will be the same. It just takes more power to rotate the crankshaft of a longer stroke as the rpm's go up. If you increase the bore, you are increasing the power made within that cylinder.

As far as who would come across the finish line first, it really depends on how it was built. 60' times, gear ratios and area under the power curve between shift intervals are all deciding factors.


-

"Youth in Asia"...I don't see anything wrong with that.

Thanks everyone for the replys. That is what I though, but I missed the part about larger bore on a stroker motor. Thanks again guys.
On a side note what is the maxuim bore that someone has run on a LD9. I was thinking 40 thou....



PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO

.040 is the maximum to run safely when you look at replacement pistons but I'm sure if you are risky enough you can get a bigger. I would do it for a race only car but not on a street driven car. I have a spare 2.3 block that I should bore and see how much I can bore it to get as much as possible. I always wanted to go .060 over on a 2.3 block with a modified (for longer stroke) 2.4 crank to see how it goes.



Gilles
2.3 Ho

Brian Whalen wrote:A longer stroke gives a longer lever arm which is what gives a motor more torque. A larger bore on a shorter crank will do the same.

that isnt true

ive never seen a 2.0 V8 make a whole lotta tq , a whole lotta hp yes , and rev to the sky yes


larger bore will to a point increase the tq up to a point , once you cross a certian bore to stroke ratio , you start droping tq in the lower range

[quote=97trd(???™)]

Brian Whalen wrote:A longer stroke gives a longer lever arm which is what gives a motor more torque. A larger bore on a shorter crank will do the same.

that isnt true

ive never seen a 2.0 V8 make a whole lotta tq , a whole lotta hp yes , and rev to the sky yes


larger bore will to a point increase the tq up to a point , once you cross a certian bore to stroke ratio , you start droping tq in the lower range

Sorry. I didn't mean the exact same. I meant that you will gain torque over a smaller bore with the same stroke under the same dynamic compression. There is no way around it, if you have a certain amount of oxygen in a cylinder, you have a specific power potential, and therefore a specific horsepower and torque.

On a side note: A 2.0 V8 is a drop in displacement and stroke. I believe we are talking about motors of the same displacement but of different stroke or comparing the difference between motors of different displacement with the same stroke (at least I am). When you change the stroke and displacement to make a comparison, there is no variable held constant to make that comparison


-

"Youth in Asia"...I don't see anything wrong with that.

2 engines of similar displacement, with equal cylinder filling, make similar horsepower and torque.

The legends have developed that long stroke engines are better for torque and short stroke engines are better for high rpm. There's some fact behind the legend, but the conclusion isn't necessarily right.

It's usually easier to make large increases in displacement by changing the stroke than by boring the engine. When this is done without checking that the intake/ exhaust path flows enough air for the new displacement you'll starve the engine at upper engine rpm. The engine will feel stronger at low rpm but may not feel as strong at higher rpm. And if the restriction in flow is significant enough, power will begin to drop at a lower engine rpm. The engine seems to make good torque and doesn't seem to make more top end hp.

Changing stroke without changing rod length affects rod:stroke ratio. Longer stroke produces lower r:s ratio. Lower r:s tends to breathe well at lower engine rpm. This is also where the old legends come from. Larger r:s ratios tend to do a poorer job of drawing air at lower rpm.

There's a nice writeup of rod ratio pros and cons here:
http://victorylibrary.com/mopar/rod-tech-c.htm

-->Slow

i used the 2.0 just for a example , at the extreme

slowolej wrote:2 engines of similar displacement, with equal cylinder filling, make similar horsepower and torque.

The legends have developed that long stroke engines are better for torque and short stroke engines are better for high rpm. There's some fact behind the legend, but the conclusion isn't necessarily right.

It's usually easier to make large increases in displacement by changing the stroke than by boring the engine. When this is done without checking that the intake/ exhaust path flows enough air for the new displacement you'll starve the engine at upper engine rpm. The engine will feel stronger at low rpm but may not feel as strong at higher rpm. And if the restriction in flow is significant enough, power will begin to drop at a lower engine rpm. The engine seems to make good torque and doesn't seem to make more top end hp.

Changing stroke without changing rod length affects rod:stroke ratio. Longer stroke produces lower r:s ratio. Lower r:s tends to breathe well at lower engine rpm. This is also where the old legends come from. Larger r:s ratios tend to do a poorer job of drawing air at lower rpm.

There's a nice writeup of rod ratio pros and cons here:
http://victorylibrary.com/mopar/rod-tech-c.htm

-->Slow

^Ehhh.....(apples and oranges) your including the head flow factors and different rpm ranges, both of which were not talked about in the above posts, your not wrong but what your trying to say doesn't really apply.

Torque = Force x Distance....Given the same bore a longer crank offset (longer storke) will make more torque since the acting distance from the centerline of the crankshaft is longer(This is not a legend). Theres alot of other factors that come to play when speculating hp & Tq. Yes, you can starve a motor or apply a different type of adverse condition from ideal to bring out a certain quality your looking for. However given the same suction and positive pressure numbers during intake and exhaust on two motors of equal bore and differeing stroke the stroker WILL make more torque. If both motors were given the same fueling, the stroker will make less hp because it can't rotate as fast as the motor with the smaller stroke which can physically move more air and fuel throught it since it can rev faster. Remeber, this is given the same intake and positive pressure on the intake and exhaust strokes...thats the only way this comparison is valid.

The problem with this post is that the original question was worded wrong. Neither engine is a bad torque engine. Neither is a better hp engine. But one is better suited to produce power at a lower rpm.

An internal combustion engine is not a simple machine. Isolating the crank arm length to indicate more ore less torque ignores the dynamic nature of the engine. With peak combustion pressures occurring at 12-15 deg ATDC, there's little advantage to be gained in leverage from a longer throw. At the point where the throw has the ability to do the most work on the crank, 90 deg ATDC, cylinder volume is increasing at it's maximum rate and cylinder pressures are decreasing very rapidly. The effect of the longer crank arm has little time to make a difference. For the next 90 deg of crank rotation the amount of work you can extract drops to zero very quickly.

Quote:

two motors of equal bore and differeing stroke the stroker WILL make more torque.

Absolutely. But it's because the engine with the longer stroke is a larger displacement engine. It will also make more hp at the same rpm it makes more torque. You could do the same thing by increasing the bore instead of the stroke. Equal displacement engines generate equal amounts of power.

Quote:

If both motors were given the same fueling, the stroker will make less hp because it can't rotate as fast as the motor with the smaller stroke which can physically move more air and fuel throught it since it can rev faster.

It is the ability of the engine to move air which allows it to make power. If two engines burn equal amounts of fuel and air, they will make equal power. 200 hp at 6000 rpm is the same amount of power as 200hp at 8000 rpm.
If one engine displaces more volume than the other, the larger engine will likely run into airflow restrictions sooner than the smaller engine. When looking at the rpm where power peaks for the smaller engine, the larger engine may not be able to produce more power due to insufficient airflow. But it will at least be able to produce the same power since the amount of airflow hasn't changed, only the displacement.

Quote:

your including the head flow factors and different rpm ranges, both of which were not talked about in the above posts

But they were talked about in the original post.

Quote:

First engine:

* Low revving engine
* Long piston stroke
* Mid to low size piston bore
* Midsized TB and exhaust, & mild porting
* High compression

Higher torque motor?

Secound engine:

* High revvingng engine
* Short piston stroke
* Large toMidsizede piston bore
* Large TB and exhaust, & fully built head
* High compression

Higher horsepower motor?

These combinations are what cause the myths that long stroke engines produce better torque. The first engine is not a better torque producing engine. It's a hp starved engine. The better answer is that the first engine is better suited to producing power at a lower engine rpm due to the following reasons:
1) Midsize TB and exhaust implies high gas velocity at low flow rates and restricted flow at higher rpm
2) Longer stroke engines tend to be more susceptible to imbalances at higher rpm.

The second engine is better suited to high rpm power production. Large TB and exhaust imply lower velocity at low flow and less restriction to high flow, and shorter stroke engines tend to be less responsive to imbalance at high rpm.

-->Slow

slowolej wrote:.........cut cut......................
These combinations are what cause the myths that long stroke engines produce better torque. The first engine is not a better torque producing engine. It's a hp starved engine. The better answer is that the first engine is better suited to producing power at a lower engine rpm due to the following reasons:
1) Midsize TB and exhaust implies high gas velocity at low flow rates and restricted flow at higher rpm
2) Longer stroke engines tend to be more susceptible to imbalances at higher rpm.

The second engine is better suited to high rpm power production. Large TB and exhaust imply lower velocity at low flow and less restriction to high flow, and shorter stroke engines tend to be less responsive to imbalance at high rpm.

-->Slow

I think you explained it best. That was what I was trying to wrap my head around. I just needed to see it from different angles to truly get it in my head.
Thank you all for the intelligent response's.



PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO

The longer the stroke the more torque the bigger bore allows the head to breath better because it unshrouds the valves at higher lifts and allows for bigger valves to fit in the cylinder. That's why in the earlier example of the 377 sbc vs 383 sbc the 377 makes more hp 4.125" bore vs 4.030 bore, and the 383 makes more torque 3.75" stroke vs 377 = 3.48" stroke. The bigger bore of the 377 will allow a 2.08" or 2.1" intake valve to fit where a 383 will allow a 2.08" intake but the valve is shrouded at higher lifts and it cuts off the airflow into the engine at higher rpms and the 377 doesn't so it makes more upper rpm hp.
Now if you're a sharpe engine designer or builder build a 406, 420 or 434 which has a 4.155" x 3,75", 4.155" x 3.875" or 4.155" x 4" bore x stroke respectively and put a big port head on it and it will smash a 377 in both hp & tq.


2000 Z24 5spd header & catback for now.

hmmm hp



I went .040" over on my build, lightened up the rotating mass, went with larger t/b, larger cams........ my sig has the results.




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