Drag race T135 version
- Thread starter traxxas-modifier
- Start date
Kim G Linagatik
New Member
Good morning doc do you know any conversion for a short connecting rod
For out t135? I tried out smash and shogun all of suzuki
The pin width fit but the height of the bearing would not fit
On my stroker pin. Can you help me out i need atleast 3 mm shorter
Than the stock connecting rod but would fit the stroker pin andbearing
For out t135? I tried out smash and shogun all of suzuki
The pin width fit but the height of the bearing would not fit
On my stroker pin. Can you help me out i need atleast 3 mm shorter
Than the stock connecting rod but would fit the stroker pin andbearing
sacker42
Super Veteran
use mio conrod w/ 1.5mm+ pin15 (that is 3mm shorter than our stock conrod)
...but you need to change your piston to pin 15 (may masamang balak
)
docgabby
Super Veteran
why would you like a shorter conrod?? unless you have intentions of concealing the stroke up?? the stock length of the sniper conrod is plus 7mm of the stock mio conrod. therefore if you want to conceal a 3mm stroke up therefore you need a plus 4mm mio conrod. you could place a bushing on the mio small end of the conrod to accommodate the sniper piston pin 14mm.
sniping_area
Super Veteran
you can use also jiso 4valve psiton for mio if u prefer using it.. but its 69mm.. short stroke hi rpm
rowan
Super Veteran
shorter conrod can lessen the life of your cylinder liner. unless u really want concealing. suggestions from doc,mac and other guys can be your options too.
alx.cruz
Super Veteran
Lets go back to the gearing/transmission topic...
for example, we have 2 different 200cc Sniper.
1st is the "oversquare" 65mm bore x 58.7mm stroke (194.79cc).
2nd is the slightly "undersquare" 62mm bore x 65.7mm stroke (198.35).
as we all know, the 2 engine set-up has different power delivery.
oversquare on higher rpms (lets say the peak tourqe is in between 8,500-10,000 rpm)
undersquare on lower rpms (lets say the peak tourqe is at 7,000-9,000 rpm)
Can the two set-up have the same close ratio gearings though the peak tourqe operating speed range is different?
for example, we have 2 different 200cc Sniper.
1st is the "oversquare" 65mm bore x 58.7mm stroke (194.79cc).
2nd is the slightly "undersquare" 62mm bore x 65.7mm stroke (198.35).
as we all know, the 2 engine set-up has different power delivery.
oversquare on higher rpms (lets say the peak tourqe is in between 8,500-10,000 rpm)
undersquare on lower rpms (lets say the peak tourqe is at 7,000-9,000 rpm)
Can the two set-up have the same close ratio gearings though the peak tourqe operating speed range is different?
Kim G Linagatik
New Member
i had the intention of concealing my stroke up. i had many comments from my friends at school that i had too much set up for just a daily usage of my bike i want to conceal it. second thing, i had a friend also a motorcycle enthusiast who had a satria 150 with stock bore but stroked up 4mm the power was very monstrous.
bout i am just using stock CDI so i cant over rev my bike ( just a safety precaution for my self)
ROAN; nope it didnt shorten the lifespan of the liner we had multiple bikes in our team that uses stroked up yet they last till now...
the longest that is now still on the road is a satria 150 which was used daily by the owner for 4years strong till now
bout i am just using stock CDI so i cant over rev my bike ( just a safety precaution for my self)
ROAN; nope it didnt shorten the lifespan of the liner we had multiple bikes in our team that uses stroked up yet they last till now...
the longest that is now still on the road is a satria 150 which was used daily by the owner for 4years strong till now
Kim G Linagatik
New Member
( I Forgot to add this up ) by also concealing the stroke and using a short connecting rod the responsiveness of the RPM by 25% and i mean its really a lot
i had tried other bike's with this kinda set up and god its very responsive i would say its just gonna compete with dragbikes's
i had tried other bike's with this kinda set up and god its very responsive i would say its just gonna compete with dragbikes's
docgabby
Super Veteran
Effects of Long Rods
Pro:
Con:
To take advantage of the energy that occurs within the movement of a column of air, it is important to select manifold and port dimensions that will promote high velocity within both the intake and exhaust passages. Long runners and reduced inside diameter air passages work well with long rods.
Camshaft selection must be carefully considered. Long duration cams will reduce the cylinder pressure dramatically during the closing period of the intake cycle.
Effects of Short Rods
Pro:
Pro:
- Provides longer piston dwell time at & near TDC, which maintains a longer state of compression by keeping the chamber volume small. This has obvious benefits: better combustion, higher cylinder pressure after the first few degrees of rotation past TDC, and higher temperatures within the combustion chamber. This type of rod will produce very good mid to upper RPM torque.
- The longer rod will reduce friction within the engine, due to the reduced angle which will place less stress at the thrust surface of the piston during combustion. These rods work well with numerically high gear ratios and lighter vehicles.
- For the same total deck height, a longer rod will use a shorter (and therefore lighter) piston, and generally have a safer maximum RPM.
Con:
- They do not promote good cylinder filling (volumetric efficiency) at low to moderate engine speeds due to reduced air flow velocity. After the first few degrees beyond TDC piston speed will increase in proportion to crank rotation, but will be biased by the connecting rod length. The piston will descend at a reduced rate and gain its maximum speed at a later point in the crankshaft’s rotation.
- Longer rods have greater interference with the cylinder bottom & water jacket area, pan rails, pan, and camshaft - some combinations of stroke length & rod choice are not practical.
To take advantage of the energy that occurs within the movement of a column of air, it is important to select manifold and port dimensions that will promote high velocity within both the intake and exhaust passages. Long runners and reduced inside diameter air passages work well with long rods.
Camshaft selection must be carefully considered. Long duration cams will reduce the cylinder pressure dramatically during the closing period of the intake cycle.
Effects of Short Rods
Pro:
- Provides very good intake and exhaust velocities at low to moderate engine speeds causing the engine to produce good low end torque, mostly due to the higher vacuum at the beginning of the intake cycle. The faster piston movement away from TDC of the intake stroke provides more displacement under the valve at every point of crank rotation, increasing vacuum. High intake velocities also create a more homogenous (uniform) air/fuel mixture within the combustion chamber. This will produce greater power output due to this effect.
- The increase in piston speed away from TDC on the power stroke causes the chamber volume to increase more rapidly than in a long-rod motor - this delays the point of maximum cylinder pressure for best effect with supercharger or turbo boost and/or nitrous oxide.
- Cam timing (especially intake valve closing) can be more radical than in a long-rod motor.
- Causes an increase in piston speed away from TDC which, at very high RPM, will out-run the flame front, causing a decrease in total cylinder pressure (Brake Mean Effective Pressure) at the end of the combustion cycle.
- Due to the reduced dwell time of the piston at TDC the piston will descend at a faster rate with a reduction in cylinder pressure and temperature as compared to a long-rod motor. This will reduce total combustion.
alx.cruz
Super Veteran
have you had a dyno test regarding the 25% increase in responsiveness? or all by just gut feeling and looking at your tachometer?
either way, it is really expected to gain more power on your low-mid rpm as posted by Doc
docgabby
Super Veteran
or it could be due to the increase in displacement due to the hidden stroke up
docgabby
Super Veteran
An engine is described as oversquare or short-stroke if its cylinders have a greater bore diameter than its stroke length - giving a ratio value of greater than 1:1.
For example an engine which has 100 millimetres (3.94 in) bore and 80 millimetres (3.15 in) stroke has a bore/stroke value of:
100 mm / 80 mm = 1.25:1
An oversquare engine allows for more and larger valves in the head of the cylinder, lower friction losses (due to the reduced distance travelled during each engine rotation) and lower crank stress (due to the lower peak piston speed relative to engine speed). Due to the increased piston- and head surface area, the heat loss increases as the bore/stroke-ratio is increased excessively. Because these characteristics favor higher engine speeds, oversquare engines are often tuned to develop peak torque at a relatively high speed.
The reduced stroke length allows for a shorter cylinder and sometimes a shorter connecting rod, generally making oversquare engines less tall than undersquare engines of similar engine displacement but wider and longer (for engines with vertical cylinder axes).
By changing the crankshaft and modifying the connecting rod(s), piston(s) and/or engine block an engine can be "de-stroked". This reduces the displacement and consequently the torque of the engine, but can allow it to run at higher speeds and in fact develop greater peak power.
An engine is described as undersquare or long-stroke if its cylinders have a smaller bore (width, diameter) than its stroke (length of piston travel) - giving a ratio value of less than 1:1.
For example an engine which has 90 millimetres (3.54 in) bore and 120 millimetres (4.72 in) stroke has a bore/stroke value of:
90 mm / 120 mm = 0.75:1
At a given engine speed, a longer stroke increases engine friction (since the piston travels a greater distance per stroke) and increases stress on the crankshaft (due to the higher peak piston speed). The smaller bore also reduces the area available for valves in the cylinder head, requiring them to be smaller or fewer in number. Because these factors favor lower engine speeds, undersquare engines are most often tuned to develop peak torque at relatively low speeds.
An undersquare engine will typically be more compact in the directions perpendicular to piston travel but larger in the direction parallel to piston travel.
An engine can be "stroked" by replacing the crankshaft with a so-called "stroker" crankshaft and modifying the connecting rod(s), piston(s) or engine block to accommodate the increased piston travel. This increases the displacement and therefore the torque of the engine, but may reduce the peak speed at which it is safe to run.
For example an engine which has 100 millimetres (3.94 in) bore and 80 millimetres (3.15 in) stroke has a bore/stroke value of:
100 mm / 80 mm = 1.25:1
An oversquare engine allows for more and larger valves in the head of the cylinder, lower friction losses (due to the reduced distance travelled during each engine rotation) and lower crank stress (due to the lower peak piston speed relative to engine speed). Due to the increased piston- and head surface area, the heat loss increases as the bore/stroke-ratio is increased excessively. Because these characteristics favor higher engine speeds, oversquare engines are often tuned to develop peak torque at a relatively high speed.
The reduced stroke length allows for a shorter cylinder and sometimes a shorter connecting rod, generally making oversquare engines less tall than undersquare engines of similar engine displacement but wider and longer (for engines with vertical cylinder axes).
By changing the crankshaft and modifying the connecting rod(s), piston(s) and/or engine block an engine can be "de-stroked". This reduces the displacement and consequently the torque of the engine, but can allow it to run at higher speeds and in fact develop greater peak power.
An engine is described as undersquare or long-stroke if its cylinders have a smaller bore (width, diameter) than its stroke (length of piston travel) - giving a ratio value of less than 1:1.
For example an engine which has 90 millimetres (3.54 in) bore and 120 millimetres (4.72 in) stroke has a bore/stroke value of:
90 mm / 120 mm = 0.75:1
At a given engine speed, a longer stroke increases engine friction (since the piston travels a greater distance per stroke) and increases stress on the crankshaft (due to the higher peak piston speed). The smaller bore also reduces the area available for valves in the cylinder head, requiring them to be smaller or fewer in number. Because these factors favor lower engine speeds, undersquare engines are most often tuned to develop peak torque at relatively low speeds.
An undersquare engine will typically be more compact in the directions perpendicular to piston travel but larger in the direction parallel to piston travel.
An engine can be "stroked" by replacing the crankshaft with a so-called "stroker" crankshaft and modifying the connecting rod(s), piston(s) or engine block to accommodate the increased piston travel. This increases the displacement and therefore the torque of the engine, but may reduce the peak speed at which it is safe to run.
docgabby
Super Veteran
Should your motor be Square? Under Square? Or Over Square?
In general, horsepower is built with bore diameter and torque is developed with stroke length. An engine with a bore larger than the stroke is referred to as an “over-square” engine. Over-square engines tend to be higher rpm engines than other designs and the more over-square, the greater the rpm spread between peak torque and peak horsepower. With few exceptions, most production, high performance and race engines are over-square.
A “square engine” is one with equal or nearly equal bore and stroke dimensions. A square engine will generally produce more torque than the same cubic inch over-square design; however the rpm will be lower so the maximum horsepower produced will also generally be lower. Also we find that in a square design the spread between peak torque and peak horsepower will be closer together than in the over-square design. If you are running a heavy car or truck, say over 4000 lbs, I recommend leaning towards a square design or at least a long stroke big cubic inch motor.
“Under-square” engines were very common in the early days of automobiles. On a recent walk through the Indy Hall of Fame I noticed an old car with an engine having a 5” bore and a 7” stroke, it made 100 horsepower at 1000 rpm, things sure have changed! For many years now under-square engines have been a rare exception in passenger cars. They are more commonly used in commercial trucks and in industrial equipment and never in race cars.
To clearly understand the relationships, let’s look at three engine bore/stroke combinations all having the same bore:
302 cid with a 4” bore and a 3” stroke
This engine design has been quite popular and known for its high rpm capabilities. The shorter stroke has a slower piston speed per stroke allowing higher revs. Remember the 302 Z-28 Camaro or the Boss 302 Mustang? Screamers!
350 cid with a 4” bore and a 3.48” stroke
Less rpm capability but more torque than the 302 cid above. This combination and those very close to it have been popular for many years.
402 cid with a 4” bore and a 4” stroke
Even less rpm capability than the 350 cid but the potential for quite a bit more torque than either combination above. If you are running a heavy car or truck, you will want to move in this direction.
Refer to my formulas on horsepower and torque as you consider the above and plan your next engine build. If in doubt – stroke it!
In general, horsepower is built with bore diameter and torque is developed with stroke length. An engine with a bore larger than the stroke is referred to as an “over-square” engine. Over-square engines tend to be higher rpm engines than other designs and the more over-square, the greater the rpm spread between peak torque and peak horsepower. With few exceptions, most production, high performance and race engines are over-square.
A “square engine” is one with equal or nearly equal bore and stroke dimensions. A square engine will generally produce more torque than the same cubic inch over-square design; however the rpm will be lower so the maximum horsepower produced will also generally be lower. Also we find that in a square design the spread between peak torque and peak horsepower will be closer together than in the over-square design. If you are running a heavy car or truck, say over 4000 lbs, I recommend leaning towards a square design or at least a long stroke big cubic inch motor.
“Under-square” engines were very common in the early days of automobiles. On a recent walk through the Indy Hall of Fame I noticed an old car with an engine having a 5” bore and a 7” stroke, it made 100 horsepower at 1000 rpm, things sure have changed! For many years now under-square engines have been a rare exception in passenger cars. They are more commonly used in commercial trucks and in industrial equipment and never in race cars.
To clearly understand the relationships, let’s look at three engine bore/stroke combinations all having the same bore:
302 cid with a 4” bore and a 3” stroke
This engine design has been quite popular and known for its high rpm capabilities. The shorter stroke has a slower piston speed per stroke allowing higher revs. Remember the 302 Z-28 Camaro or the Boss 302 Mustang? Screamers!
350 cid with a 4” bore and a 3.48” stroke
Less rpm capability but more torque than the 302 cid above. This combination and those very close to it have been popular for many years.
402 cid with a 4” bore and a 4” stroke
Even less rpm capability than the 350 cid but the potential for quite a bit more torque than either combination above. If you are running a heavy car or truck, you will want to move in this direction.
Refer to my formulas on horsepower and torque as you consider the above and plan your next engine build. If in doubt – stroke it!
docgabby
Super Veteran
A piston engine is undersquare or longstroke if its cylinders have a smaller bore (width, diameter) than stroke (length of piston travel). Oversquare is the opposite.
Undersquare engines
These produce strong torque at low to mid range rpm's because of the "leverage" advantage of a longer stroke. But, undersquare can be a negative trait, since a longer stroke usually means greater friction, a weaker crankshaft and a smaller bore means smaller valves which restricts gaseous exchange; however, modern technology has lessened these problems (explanation?). An undersquare engine usually has a lower redline, but should generate more low-end torque. In addition, a longer stroke engine can have a higher compression ratio with the same octane fuel compared to a similar displacement engine with a much shorter stroke ratio. This also equals better fuel economy and somewhat better emissions. Going undersquare can cause pistons to wear more quickly (greater side-loads on the cylinder walls) and can cause ring seal problems and lubrication problems; with increased loads on the crankshaft, pistons, the piston pins, connecting rods, and rod bearings (due to piston speed). In general, a longer stroke leads to higher thermal efficiency through faster burning and lower overall chamber heat loss. A longer stroke will have greater port velocity at a given RPM, more torque due to more leverage on the crank, will achieve it's greatest efficiency at a lower RPM. Smaller combustion chambers are also more efficient, with the flame front having a shorter distance to travel- this leads to being more detonation resistant, and having an advantage for emissions.
Oversquare engines
These are generally more reliable, wears less, and can be run at a higher speed. In oversquare engines power does not suffer, but low-end torque does - it being relative to crank throw (distance from the crank center to the crankpin). An oversquare engine cannot have as high a compression ratio as a similar engine with a much higher stroke ratio, and using the same octane fuel. This causes the oversquare engine to have poorer fuel economy, and somewhat poorer exhaust emissions. Breathing is an important advantage for oversquare engines, as the edges of the valves are less obstructed by the cylinder wall (called "unshrouded"). The big bore can fit larger (or more) valves into the head and give them more breathing room.
With shorter crankshaft stroke (and therefore piston travel) parasitic losses are reduced. Ring drag is the major source of internal frictionand the crankshaft assembly also rotates in a smaller arc, so the windage is reduced. Oil-pressure problems caused by windage and oil aeration are lessened.
----------------
It also states that 'engines used at sustained high rpm are usually better suited to running with less stroke and more bore (oversquare).'
Undersquare engines
These produce strong torque at low to mid range rpm's because of the "leverage" advantage of a longer stroke. But, undersquare can be a negative trait, since a longer stroke usually means greater friction, a weaker crankshaft and a smaller bore means smaller valves which restricts gaseous exchange; however, modern technology has lessened these problems (explanation?). An undersquare engine usually has a lower redline, but should generate more low-end torque. In addition, a longer stroke engine can have a higher compression ratio with the same octane fuel compared to a similar displacement engine with a much shorter stroke ratio. This also equals better fuel economy and somewhat better emissions. Going undersquare can cause pistons to wear more quickly (greater side-loads on the cylinder walls) and can cause ring seal problems and lubrication problems; with increased loads on the crankshaft, pistons, the piston pins, connecting rods, and rod bearings (due to piston speed). In general, a longer stroke leads to higher thermal efficiency through faster burning and lower overall chamber heat loss. A longer stroke will have greater port velocity at a given RPM, more torque due to more leverage on the crank, will achieve it's greatest efficiency at a lower RPM. Smaller combustion chambers are also more efficient, with the flame front having a shorter distance to travel- this leads to being more detonation resistant, and having an advantage for emissions.
Oversquare engines
These are generally more reliable, wears less, and can be run at a higher speed. In oversquare engines power does not suffer, but low-end torque does - it being relative to crank throw (distance from the crank center to the crankpin). An oversquare engine cannot have as high a compression ratio as a similar engine with a much higher stroke ratio, and using the same octane fuel. This causes the oversquare engine to have poorer fuel economy, and somewhat poorer exhaust emissions. Breathing is an important advantage for oversquare engines, as the edges of the valves are less obstructed by the cylinder wall (called "unshrouded"). The big bore can fit larger (or more) valves into the head and give them more breathing room.
With shorter crankshaft stroke (and therefore piston travel) parasitic losses are reduced. Ring drag is the major source of internal frictionand the crankshaft assembly also rotates in a smaller arc, so the windage is reduced. Oil-pressure problems caused by windage and oil aeration are lessened.
----------------
It also states that 'engines used at sustained high rpm are usually better suited to running with less stroke and more bore (oversquare).'
docgabby
Super Veteran
Re: More HP and TQ: Bore vs Stroke?
I have to agree with 69 Chevy. Heavy duty engines that require low end torque to get a heavy load moving use a bigger stroke than bore(undersquare). Engines that are meant to make power up high are the opposite(oversquare).
So I would say a undersquare would be best suited for a heavier car, towing, or drag racing. An oversquare would be better for a road racing application.
I am of the impression that undersquare engine will get better economy because you don't have to give it as much throttle to get going. And as for number of cylinders I would say more make the engine smoother and able to rev quicker. For some reason a 5.9L CTD(cummins turbo diesel) makes more low end torque than Chevy and ford's diesels because it is a straight six instead of a V8, I don't know why.
Hope this makes sense.LOL
So I would say a undersquare would be best suited for a heavier car, towing, or drag racing. An oversquare would be better for a road racing application.
I am of the impression that undersquare engine will get better economy because you don't have to give it as much throttle to get going. And as for number of cylinders I would say more make the engine smoother and able to rev quicker. For some reason a 5.9L CTD(cummins turbo diesel) makes more low end torque than Chevy and ford's diesels because it is a straight six instead of a V8, I don't know why.
Hope this makes sense.LOL
docgabby
Super Veteran
HORSEPOWER:
Horsepower = torque x rpm ÷ 5252
The constant 5252 comes from our old buddy James Watt’s 17th Century definition of horsepower. He must have been one of the original gear-heads. He just had to have a way to measure his toys enhancements. So, if 33,000 pound-feet per minute is divided by 2 times pi (6.2832), the result is 5252.1008 rounded down to 5252.
For example : An all stock Gen 2 Max makes a maximum torque of 112 ft/lbs at 6500 rpm when measured at the rear wheel by a dynamometer.
What is it’s hp at this rpm? 112×6500 ÷ 5252 = 138.61 hp.
Horsepower is a measurement of how much work (force over distance) an engine can do in a given amount of time. It is a function of a given amount of torque (force) at a given rpm (distance). At a given rpm, horsepower is directly proportional to torque. The only practical method for measuring horsepower is by measuring engine torque and rpm with a dynamometer.
By increasing torque at a specific rpm, horsepower increases at a corresponding amount. Also, if the torque remains constant but the rpm increases, then horsepower increases in direct proportion to rpm. Even when torque starts to drop off (beyond the engine’s torque peak) , as long as rpm increases faster than torque drops, horsepower will still increase. Horsepower can also be described as how much and how often a cylinder fills, and how often if fires in a specified time period.
TORQUE = HORSEPOWER X 5252 ÷ RPM
Example: Gen 2 Max makes 172 hp x 5252 ÷ 8000 rpm
This = 112.91 ft/lbs torque. I have backed up these numbers spot on with the chassis dyno.
Torque is a twisting or turning force that engineers measure in “pound-foot” (equal to a 1 lb. force applied at the end of a 1 foot lever). An engine’s power is actually established by first measuring torque at a given rpm and then calculating horsepower.
******NOTE Since horsepower is equal to torque multiplied by rpm, any torque increase results in a power increase at a given rpm level. This is why you are better off concentrating on improving your torque instead of horsepower for the best performing engine. You make the torque……..you will have the horsepower! Most of the established racers and qualified engine builders concentrate on improving torque within the rpm range their engine needs to operate.
An engine’s torque is determined by the percentage a cylinder is filled at a given rpm. The greater the cylinder fill is, the greater the torque. If power is going to be increased, than you are going to find that it is crucial to improve an engine’s ability to breathe.
Peak torque is reached when an engine runs out of air OR loses its ability to breathe better. This is the point of maximum cylinder fill. As mentioned earlier, an engine can continue to make more horsepower even when torque is falling as long as rpm is increasing faster than torque is falling. So, if maximum torque is the point of maximum cylinder fill, then maximum horsepower is the point where torque is falling off faster than rpm is increasing.
For a given engine, the intake and exhaust tracts, cylinder head(s), cam(s), displacement, stroke and rod length are among the factors that control the amount of torque and the torque peak. Also, the mean airflow velocity can be quite a factor on peak torque rpm. Mean flow velocity is dependant on runner or pipe cross-sectional area, not volume. Rest assured that the peak torque rpm can be controlled by selecting parts with specific cross-sectional areas.
The most successful race engines are normally designed to turn a higher rpm and have greater cylinder fill and torque at the higher rpm levels. This type of engine design however will narrow the use of that power plants application, for instance a drag race oriented engine where concerns of torque and horsepower below shift power values are not a part of the program. Typical high performance engine modifications generally shift an engine’s maximum torque to a higher rpm range, and this can result in the loss of low end power. The key to building a “happy” engine is to maximize torque in the rpm range most important for meeting your objectives, goals and riding styles.
Although all engines produce torque, an engine that produces peak torque at low rpm if often referred to as a torque engine, while one that produces torque at high rpm is typically referred to as a horsepower engine. Since torque and horsepower curves always cross at 5252 rpm, and engine will always produce more pound-foot of torque than horsepower below 5252 rpm, and more horsepower than pound-foot of torque above 5252 rpm. This explains how a four cylinder in-line four Japanese engine that revs to 13,000 rpm can produce higher horsepower than a V-twin, but make less torque. Long stroke, small bore (under square) engines like the V-twin boys typically are lower revving with high torque below 5252 rpm (like our friends with the Yamaha Warriors). On the other side of the street, big bore, short stroke (over square) engines normally are higher revving and produce high horsepower at high rpm from a relatively low torque reading.
The relationship between torque and horsepower is crucial to understanding the different characteristics of under and over square engine designs and being able to maximize each design’s power output. So, to sum up in general, increasing the engine’s stroke shifts the torque peak to a lower rpm. Decreasing the stroke (formula one car stuff, very cool) will bring the torque into the higher rpm range.
I hope this week’s Tech Tip gives you a better understanding of the definition of horsepower, torque and how engine configuration comes into play on the particular engine design’s ability to produce them.
Horsepower = torque x rpm ÷ 5252
The constant 5252 comes from our old buddy James Watt’s 17th Century definition of horsepower. He must have been one of the original gear-heads. He just had to have a way to measure his toys enhancements. So, if 33,000 pound-feet per minute is divided by 2 times pi (6.2832), the result is 5252.1008 rounded down to 5252.
For example : An all stock Gen 2 Max makes a maximum torque of 112 ft/lbs at 6500 rpm when measured at the rear wheel by a dynamometer.
What is it’s hp at this rpm? 112×6500 ÷ 5252 = 138.61 hp.
Horsepower is a measurement of how much work (force over distance) an engine can do in a given amount of time. It is a function of a given amount of torque (force) at a given rpm (distance). At a given rpm, horsepower is directly proportional to torque. The only practical method for measuring horsepower is by measuring engine torque and rpm with a dynamometer.
By increasing torque at a specific rpm, horsepower increases at a corresponding amount. Also, if the torque remains constant but the rpm increases, then horsepower increases in direct proportion to rpm. Even when torque starts to drop off (beyond the engine’s torque peak) , as long as rpm increases faster than torque drops, horsepower will still increase. Horsepower can also be described as how much and how often a cylinder fills, and how often if fires in a specified time period.
TORQUE = HORSEPOWER X 5252 ÷ RPM
Example: Gen 2 Max makes 172 hp x 5252 ÷ 8000 rpm
This = 112.91 ft/lbs torque. I have backed up these numbers spot on with the chassis dyno.
Torque is a twisting or turning force that engineers measure in “pound-foot” (equal to a 1 lb. force applied at the end of a 1 foot lever). An engine’s power is actually established by first measuring torque at a given rpm and then calculating horsepower.
******NOTE Since horsepower is equal to torque multiplied by rpm, any torque increase results in a power increase at a given rpm level. This is why you are better off concentrating on improving your torque instead of horsepower for the best performing engine. You make the torque……..you will have the horsepower! Most of the established racers and qualified engine builders concentrate on improving torque within the rpm range their engine needs to operate.
An engine’s torque is determined by the percentage a cylinder is filled at a given rpm. The greater the cylinder fill is, the greater the torque. If power is going to be increased, than you are going to find that it is crucial to improve an engine’s ability to breathe.
Peak torque is reached when an engine runs out of air OR loses its ability to breathe better. This is the point of maximum cylinder fill. As mentioned earlier, an engine can continue to make more horsepower even when torque is falling as long as rpm is increasing faster than torque is falling. So, if maximum torque is the point of maximum cylinder fill, then maximum horsepower is the point where torque is falling off faster than rpm is increasing.
For a given engine, the intake and exhaust tracts, cylinder head(s), cam(s), displacement, stroke and rod length are among the factors that control the amount of torque and the torque peak. Also, the mean airflow velocity can be quite a factor on peak torque rpm. Mean flow velocity is dependant on runner or pipe cross-sectional area, not volume. Rest assured that the peak torque rpm can be controlled by selecting parts with specific cross-sectional areas.
The most successful race engines are normally designed to turn a higher rpm and have greater cylinder fill and torque at the higher rpm levels. This type of engine design however will narrow the use of that power plants application, for instance a drag race oriented engine where concerns of torque and horsepower below shift power values are not a part of the program. Typical high performance engine modifications generally shift an engine’s maximum torque to a higher rpm range, and this can result in the loss of low end power. The key to building a “happy” engine is to maximize torque in the rpm range most important for meeting your objectives, goals and riding styles.
Although all engines produce torque, an engine that produces peak torque at low rpm if often referred to as a torque engine, while one that produces torque at high rpm is typically referred to as a horsepower engine. Since torque and horsepower curves always cross at 5252 rpm, and engine will always produce more pound-foot of torque than horsepower below 5252 rpm, and more horsepower than pound-foot of torque above 5252 rpm. This explains how a four cylinder in-line four Japanese engine that revs to 13,000 rpm can produce higher horsepower than a V-twin, but make less torque. Long stroke, small bore (under square) engines like the V-twin boys typically are lower revving with high torque below 5252 rpm (like our friends with the Yamaha Warriors). On the other side of the street, big bore, short stroke (over square) engines normally are higher revving and produce high horsepower at high rpm from a relatively low torque reading.
The relationship between torque and horsepower is crucial to understanding the different characteristics of under and over square engine designs and being able to maximize each design’s power output. So, to sum up in general, increasing the engine’s stroke shifts the torque peak to a lower rpm. Decreasing the stroke (formula one car stuff, very cool) will bring the torque into the higher rpm range.
I hope this week’s Tech Tip gives you a better understanding of the definition of horsepower, torque and how engine configuration comes into play on the particular engine design’s ability to produce them.
