Stroker Motor Question!

[LazeR]

When you stroke a motor what exactly happens ? Does is gain displacement ? thanx ahead of time!

[K_Fulk]

Yeah it gains displacement , the piston moves further up and further back down.

[LazeR]

Where does it give you power at ? I heard Bottom end is that true ?

[K_Fulk]

Yeah.

[InsAyneROostin]

So a stroker wouldn't be ideal for sand? a bore-kit would give you more mid-top end? What's the whole deal behind strokers, bores and stuff?

[hondarider2006]

power

[LazeR]

Stroking gains more bottom end, then when you bore it, you gain more top end right ? What does a high comp piston give you ?

[K_Fulk]

Compression gives you bottom end.

[SnellCRP]

Stroker cranks have a longer throw for increased displacement. The gains from the displacement bump are typically across the board, with more power usually found on the bottom end of the powerband. A longer stroke is a longer lever acting on the crankshaft, thus providing more torque. Longer stroke creates faster piston speeds, which means that the piston can create a more accurate pressure drop to fill the cylinder more thoroughly at low rpm for torque. It is important to match the compression ratio with the duration of the cam. While additional cam duration can produce more useable power, to much duration can hurt the performance because too much duration results in lower cylinder compression pressures at low RPM which reduce the low RPM torque and power. Higher compression ratios produce more power, up to a point. The more you compress the air/fuel mixture, however, the more likely it is to create detonation or preignition. The high compression will make power all through the RPM's.

[wilkin250r]

^^Hey, somebody's moving in on my territory. I thought I had the monopoly on long technical posts.

Seriously, good explanation.

Picture the crank, connecting rod, and piston. By moving the connecting rod further out on the crank, you increase the distance that the piston travels up and down, thus increasing the stroke. This is how they make a stroker crank, they move the rod out on the crank.

This will increase torque, especially at low RPM's. However, as SnellCRP pointed out, you are increasing piston speeds. This extra speed will actually rob you of power in the upper RPM range, but it would take twice as long to explain why. With big bores, you don't increase piston speed, so you don't lose as much power in the upper RPMs. This is why they say stroker motors are "low-end" motors, because you get more power in the lower RPMs. For this reason, stroker motors may not work well with really aggressive "race-profile" cams that build power in the higher RPMs. You don't get the best of both worlds, you actually get the worst of both worlds, lousy low-end performance because of the camshaft, and lousy top-end performance because of the stroker.