was thinking today while doing some research on modding my gf's jeep.

what is it about the runner length that increases the power...namely torque...on a fuel injected engine??

for example what makes the TPI setup such a torque monster compared to the shorter runnered HSR or miniram?

i got thinking about it because i was looking at those throttle body plates that are available for her engine. basically raising the TB 1".

i know similar things exist for carbs and TBI.

i assume by raising the TB you effectively lenghten the runner on the intake...correct? (i know some benefit is from heat isolation and heatsink)

anyone shed some light on this for me?

 

The reason the stock TPI runners have such great torque is because they're so long. The air builds more speed before it hits the cyclinders, but at a higher RPM they can't supply enough air to the engine fast enough, as well as they're not a big diameter. so power is lost. Short runners provide less low end torque, but provide more at a higher rpm.

the 3.5 nissan motor has an intake manifold that swaps between short and long runners depending on RPM. Now they just need to develop that for TPI's

The throttle body spacer is a tad different. Because the fuel isn't injected directly into the cyclinder, the spacer just allows the fuel and air to mix better, thus more powerful explosion.