Strocking an engine?

[TurboShane]

Stroking an engine?

What is the reason for added torque and horsepower. Is it just the added cubes or is the anything to do with added leverage form a longer stroke? Thanks for any replies.

 

[sixgun86gn]

A larger motor ingests more air.Add fuel to that air and you have more power.The more air and fuel a motor can use the better the power.The stroke adds to the toque like a long arm,its all leverage and makes it easier for the motor to turn the wheels.the more CI the more AF mixture it can burn.

 

[TurboShane]

Lets say we have the same size motor and every thing else is the same except. One has a longer stroke one has a larger bore. What one would make more torque and what one would make more horse power and why?

 

[sixgun86gn]

Larger bore usually makes more HP,longer stroke more torque.Longer stroke is like putting a cheater bar on a wrench.The longer it is the easier to turn.Torque is a rotational force and HP is just a calculation based on an engines torque.A larger bore ingests more air and has more surface area for the flame front to push against.Without increasing the stroke it still has to push just as hard to turn the wheels,less hard with the stroke.That is why most prefer to bore and stroke as opposed to one or the other.

 

[Redrum]

I prefer bore to stoke when you consider the mass of the revolving parts. Adding stroke significantly increases piston speed and the progression is geometric in nature. Adding bore allows for larger valves to move the needed air more efficiently and gains on volumetic efficiency.

The flip side of this is that if you increase stroke you can decrease the RPM's and that results in less chance of valve float and broken springs. So, if you increase the stroke to lower the power band to a more acceptable valvetrain speed then stroking makes sense.

The added stroke creates another nuance that must be considered, especially in N/A motors and that is torque off the line. Long stroke motors tend to apply too much torque to the tires and sends them up in smoke. This is more of a street problem than a track issue.

You get into a balance point that becomes open for much discussion with about every motor combination.

 

[sixgun86gn]

Very well said.