Originally Posted by 02QR25
Do you know why this is?
Perpare to get schooled.
The qr25 motor is a very oversquare motor. Meaning it has long stroke and short rods. The piston speeds get insanely high at around 6500rpm on the stock rod length. This means volumetric efficiency falls way off, and the piston can't effectively draw enough air and fuel into the cylinder on the intake stroke. That is why the power drops off. Why waste your time turboing a 4 cyl if you can't rev it past 6500? You won't make any power.
Now if you could shorten the stroke of the motor and put in longer rods you could have yourself a decent motor. This has been attempted by putting an sr20de crank into the motor. It lowers the displacement however but it does allow it to rev higher and smoother. Making it a better overall motor.
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