Prius Pistons

[JustDidIt]

Originally Posted by why?

I remember reading the highest the Prius ratio ever gets is 11.1. The atkinson cycle keeps both the intake and exhaust valves open for long periods of time.

Wonder what kind of performance increase could be expected as going from the 10.5:1 to the 11:1 or whatever the CR would be..

When I do the Cam and Cam gear swap I would basically have the 1NZ-FE head but still the Prius bottom end. Where someone else with the 1NZ-FE would have to tear into the block and switch the pistons but hopefully leaving the stock 1NZ-FE crank. The 1NZ-FXE Does have different pistons and crankshaft but same rods. Would be really interesting to see if there would be a difference it would make between the 1NZ-FXE and 1NZ-FE crank obviously other than part #s being different..

[Viperoni]

Originally Posted by JustDidIt

Wonder what kind of performance increase could be expected as going from the 10.5:1 to the 11:1 or whatever the CR would be..

When I do the Cam and Cam gear swap I would basically have the 1NZ-FE head but still the Prius bottom end. Where someone else with the 1NZ-FE would have to tear into the block and switch the pistons but hopefully leaving the stock 1NZ-FE crank. The 1NZ-FXE Does have different pistons and crankshaft but same rods. Would be really interesting to see if there would be a difference it would make between the 1NZ-FXE and 1NZ-FE crank obviously other than part #s being different..

The (static) CR would be 13:1 if you use Prius (FXE) pistons.
The dynamic CR is apparently 11:1 if you use FXE pistons.
I was under the impression that the FE & FXE cranks were the same... or at least the stroke is. Maybe the FXE crank is stronger somehow?


To answer your question, it depends. A quick googling seems to say that there's diminishing returns, especially since you're not improving the breathing of the motor and filling the combustion chamber with more air/fuel.
One calculator said 6.5% and that's more or less what I read on another site as well... which I think is a bit low, but could be bang on. In any case, a 6.5% increase is 7hp.


If possible, I'd go with an overbore Prius piston to help increase displacement at the same time as increasing the CR... that'll help engine breathing, and it'll increase the quench area inside the combustion chamber which should help stop some detonation too.

[JustDidIt]

Originally Posted by Viperoni

The (static) CR would be 13:1 if you use Prius (FXE) pistons.
The dynamic CR is apparently 11:1 if you use FXE pistons.
I was under the impression that the FE & FXE cranks were the same... or at least the stroke is. Maybe the FXE crank is stronger somehow?

Crankshaft:
1NZ-FE: 13401-21020
1NZ-FXE: 13401-21040

Difference No idea...

Originally Posted by Viperoni

To answer your question, it depends. A quick googling seems to say that there's diminishing returns, especially since you're not improving the breathing of the motor and filling the combustion chamber with more air/fuel.
One calculator said 6.5% and that's more or less what I read on another site as well... which I think is a bit low, but could be bang on. In any case, a 6.5% increase is 7hp.

If possible, I'd go with an overbore Prius piston to help increase displacement at the same time as increasing the CR... that'll help engine breathing, and it'll increase the quench area inside the combustion chamber which should help stop some detonation too.

So what if I was to modify the induction system..different routed intake and intake manifold (been looking over making my own intake manifold after watching 'tooters' adventures...and exhaust manifold and exhaust system? I would think this would help some...right?