Prius Pistons

[4/20 NEVER FORGET]

Seriously. I was just thinking about this thread. Babies ruin everything!

[JustDidIt]

2004 Toyota Echo with the 1.5L 1NZ-FE and have just under 90,000 miles on them for $87 - is the mileage too high or should that matter for my CAM swap?

[Jason@SportsCar]

Originally Posted by JustDidIt

2004 Toyota Echo with the 1.5L 1NZ-FE and have just under 90,000 miles on them for $87 - is the mileage too high or should that matter for my CAM swap?

I have a brand new set in the box, as well as a used set. Also have a couple of spare heads. PM me if you are interested.

[JustDidIt]

Originally Posted by Jason@SportsCar

I have a brand new set in the box, as well as a used set. Also have a couple of spare heads. PM me if you are interested.

PM'd

[Autocross72]

I have hard of people doing the Prius piston swap before, but they always seem to disappear. I think the reason is that they are cast pistons with too much compression. At 13:1 compression, you would have to run full race gas, which at $9.00 a gallon would be extremely expensive. Also, cast pistons can't withstand that kind of compression for very long. You would need to go with forged pistons. You should also swap out the crapy stock Yaris rods while you are at it. They are known to be weak and the turbo guys have shown over and over again that they can't with stand much of a power increase.

[cali yaris]

Also, cast pistons can't withstand that kind of compression for very long. You would need to go with forged pistons.

That doesn't make sense if the Prius runs them as stock pistons?

[etherdude]

Originally Posted by cali yaris

That doesn't make sense if the Prius runs them as stock pistons?

The Prius Atkinson Cycle cams have the effect of lowering cylinder pressure due to holding the intake open longer and blowing intake charge back into the intake manifold. Thus the higher compression 13:1 pistons do not result in necessarily higher cylinder pressures that the lower compression ration Yaris pistons.

[Viperoni]

Originally Posted by etherdude

The Prius Atkinson Cycle cams have the effect of lowering cylinder pressure due to holding the intake open longer and blowing intake charge back into the intake manifold. Thus the higher compression 13:1 pistons do not result in necessarily higher cylinder pressures that the lower compression ration Yaris pistons.

QFT

Basically the dynamic CR of the 1nz-fxe probably isn't that much different than the DCR of the 1nz-fe... 13:1 is a very high static CR to start off on a regular fuel injected motor, ESPECIALLY with the stock cams.


It's just too bad nobody's come back and said what's happened.

[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.

[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..

[JustDidIt]

I'm still on the hunt for a set of 1NZ-FE cams and cam gear. I'd rather not go and pick up a full long block for $400-$600 - but i may have to. I'd rather just snatch a full 1NZ-FE head or even just the cams and gear.

I really want to try this out.

[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?

[why?]

crank is the same. They'd use a different part number if it was different. It is really all about pistons and the timing. the atkinson cycle doesn't give a damn about low end tourque, unlike the normal otto cycle.

[JustDidIt]

Originally Posted by JustDidIt

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

Originally Posted by why?

crank is the same. They'd use a different part number if it was different. It is really all about pistons and the timing. the atkinson cycle doesn't give a damn about low end tourque, unlike the normal otto cycle.

Read much of the other posts??

[Golddeenoh]

^ burn

[Yoda]

^LMAO

[tooter]

Originally Posted by Viperoni

QFT

It's just too bad nobody's come back and said what's happened.

That would seem to indicate that trying to run Atkinson pistons in an Otto engine did not go well.

Here's a fascinating animation of how Atkinson cycle engines work:

http://www.youtube.com/watch?v=hEfOxKmCstg

Skip to 2:20 second mark to get past the bullshit.