Very useful information on building a 5sfe, mr2.com link Options

[ILoveMySilly97]

I myself have a 5sfe and this is good heads up info if I ever decide and working on building power for my car. Sadly I'm restricted since I live in Cali.

http://www.mr2.com/forums/non-turbo-engine...-induction.html

[Special_Edy]

A couple things that may help you understand the bore/stroke relationship-

The stroke is determined by the throws on the crankshaft. The farther the rod-journals are from the center of the crankshaft(the main journals), the more mechanical advantage the piston rod has on the crankshaft. The 3sgte has an 86mm stroke, this equals 43mm for each crank throw or half the stroke. The 5sfe is ~91mm stroke which means each crank throw is 45.5mm off centerline of the crank. So even if both engines produced exactly the same amount of force with each combustion stroke, the 5sfe would generate more torque because the crankshaft has a greater mechanical advantage.

The 3s is square and the 5s is undersquare. Increasing the bore unshrouds the valves(moves them farther from the cylinderwall=more power) and provides more room for larger valves. The undersquare engine has the advantage of having a larger stroke which pulls more air/fuel into the cylinder each stroke at lower engine speeds.