Prius 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.

[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.

[JustDidIt]

Originally Posted by tooter

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

Ahhh.. Come'on Tooter...you of all people... lol - I'd like to see more optimism. The better answer would be, most people are too skurd to try it - Those who have...don't post here on YW...or just have better things to do than post cool EUREKA DIYs ... Like your manifold. :)

I've found a FULL 2012 Yaris 1NZ-FE cylinder head super cheap. Now just waiting to hear back if I can have it shipped or if I have to go pick it up.

[xnamerxx]

I wouldn't take the crank having a different part number as meaning anything more then it might not have a standard bolt pattern or it might require a longer snout.

Here is a cutout of a 1nz-fxe from an autoshow.

You can see the giant mechanical flywheel, which doesn't have provisions for a starter and you can see the giant start/stop starter on the front of the engine.

I seriously doubt that the FXE piston would have any issues in the FE engine aside from the massive increase in compression that would cause some tuning issues. The compression being close to 13:1 doesn't really scare me as long as you can control the tune, which is pretty much only possible with a aftermarket ECU. I've seen 4.6l engines running 12.6:1 on 91 octane its doable just takes more work.

The piston being HYPEREUTECTIC doesn't mean it can't handle power it just means the piston is less elastic than a forged piston, meaning when its given a shock like say detonation it doesn't deform as much so if the material sees a strong shock it will crack rather than deform. Hypereutectic pistons have some great properties about them that make them suitable choices for performance oriented situation like the fact they have little heat deformations which means they don't compress and swell as much with heat which means you can run a piston tighter in the bore and you can also run a lighter piston which makes the engine more efficient.

[JustDidIt]

Originally Posted by xnamerxx

Here is a cutout of a 1nz-fxe from an autoshow.

Sooo Pretty!

Originally Posted by xnamerxx

I seriously doubt that the FXE piston would have any issues in the FE engine aside from the massive increase in compression that would cause some tuning issues. The compression being close to 13:1 doesn't really scare me as long as you can control the tune, which is pretty much only possible with a aftermarket ECU. I've seen 4.6l engines running 12.6:1 on 91 octane its doable just takes more work.

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

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.

Originally Posted by Viperoni

Here's another thought; since 13:1 *may* be on the high side... are there thicker head gaskets we can use?

If your original post is correct, then most I may need to change when running 11:1 compression is 91 instead of 87 pump gas, besides some EM. But even then....I run on 87 now...at the supposed static CR of 13:1 or dynamic 11:1.

Originally Posted by tooter

Sorry, I really didn't mean to come off as being negative. I was only commenting on the lack of feedback as to what happened after 13:1 pistons were installed. There's no information. I'm all for trying new things. Wait till you see what I'm cooking up...

That manifold wasn't even my idea. I can't take credit for it. The guys in Puerto Rico did it first. I just thought it looked really cool and wanted one on my engine.

If if you weren't the original.. "Imitation Is The Best Form Of Flattery"... Your idea to hack up a manifold and try something new got me thinking. The way my MG1/MG2 sits, I could never use the 1NZ-FE intake or even your 'Tooter manifold' - the throttle body would conflict with my inverter. But I was thinking of doing something with the 2AZFE intake manifold because the throttle body would come out the passenger side...problem is - the manifold is plastic.



Not sure how I could 'weld' the 1NZ flange onto the 2AZFE plastic tubing :( I may just have to make/design my own. Luckily you already have the flange I need to weld onto!

[tooter]

Originally Posted by JustDidIt

If if you weren't the original.. "Imitation Is The Best Form Of Flattery"... Your idea to hack up a manifold and try something new got me thinking. The way my MG1/MG2 sits, I could never use the 1NZ-FE intake or even your 'Tooter manifold' - the throttle body would conflict with my inverter. But I was thinking of doing something with the 2AZFE intake manifold because the throttle body would come out the passenger side...problem is - the manifold is plastic.

Is this the layout of your engine? And if it is, is your intake at the front of the engine or behind it?

Not sure how I could 'weld' the 1NZ flange onto the 2AZFE plastic tubing :(

I'm not sure, but I think that the plastic might have been ultrasonically welded. And that "snail" style manifold might still have clearance issues, but that could be easily determined simply by taking some measurements.

I may just have to make/design my own. Luckily you already have the flange I need to weld onto!

No rpoblem.
I'll always be stocking them. Since the design is finalized they can be manufactured as needed.

[tooter]

Originally Posted by JustDidIt

Ahhh.. Come'on Tooter...you of all people... lol - I'd like to see more optimism.

Sorry, I really didn't mean to come off as being negative. I was only commenting on the lack of feedback as to what happened after 13:1 pistons were installed. There's no information. I'm all for trying new things. Wait till you see what I'm cooking up...

The better answer would be, most people are too skurd to try it - Those who have...don't post here on YW...or just have better things to do than post cool EUREKA DIYs ... Like your manifold. :)

That manifold wasn't even my idea. I can't take credit for it. The guys in Puerto Rico did it first. I just thought it looked really cool and wanted one on my engine.

I've found a FULL 2012 Yaris 1NZ-FE cylinder head super cheap. Now just waiting to hear back if I can have it shipped or if I have to go pick it up.

Sounds good!

The Atkinson engine is really strange. Did anyone notice that it fires on every revolution?