hotbox05

they are 12.5 compression. not sure if that's all in the piston or partly in the head design. not a motor swap just swap the pistons. undetectable by cali smog ( hopefully )

the motor runs on the atkinson cycle for efficiency and cleanliness but i would assume just the head and engine management are different.

anyone try this or have any more insight?

RTon20s

I think no response means you should be the guinea pig Darren.

Let us know how it turns out.

TuningIsLife

2006 Prius : 1.5L, 75.0mm X 84.7mm Bore X Stroke, 13.0:1 Compression ratio, power output: 76hp @ 5000 rpm.

xmetalx

This is a very interesting thread. I would like to know more information. My stepdad is the GM at marina del rey toyota so I am sure I can get hooked up on this. Is the head a direct bolt on?

hotbox05

the power output is because of it running on the atkinson cycle.


I may just go and be the guinea pig.

the head is not meant for performance at all. it's alll cleanliness. low emissions not performance.

armhergo

then.... even if it was bolt on mod .....u mean there wont be power gains ?

RTon20s

I am not really familiar with the Prius, but I think what Darren is saying is that the Prius head was never designed for performance. And that yes, even if it bolted up it would probably cost you power.

I think the big question, the one Darren is asking, is where does the increased compression ratio come from? Is it all in the pistons? Is it in the head design? Or is it both?

If it is in the pistons, and they will physically work with our block and heads, we could be on a very quick path to more n/a power via increased compression. (Assuming our super computer of an ecu won't do anything to negate the change.)

The guinea pig (Darren) is just going to have to be careful. Making sure that they piston physically fits, and doesn't create so high a compression ratio as to be non-streetable, or even catastrophic. The other concern is that swapping the pistons won't make any change to the compression ratio at all. (Likely result of different combustion chamber design of the heads.) Or that the change is so slight that it isn't worth the effort.

I commend Darren for even considering taking the initiative. And I hope good things come out of it.

hotbox05

one crazy thing i just learned is that tony killerxromances is now running just 11 to 1 pistons and with those , bolt on's , and emanage he has 128 hp and 138 torque on an auto!!!! so i'm imaging if i can get about 12 to 13 comp i'd be able to acheive very good numbers if the emanage will be able to compensate enough to run smoothly.

RTon20s

That is awesome to hear! And pistons are something we could easily get away with in the People's Republic or California. So is he running the ZPI pistons then? Did he make a post somewhere that I missed? I need all the details. If you had a competent shop, I wonder how long it would take them to install and tune.

And even though they are probably more work to tune I bet the Prius pistons could probably be had for less than the ZPI pistons.

hotbox05

he got pistons from some custom engine sop.

he spent 5k for pistons , install , emanage , tuning.

his posts are on clubxb.com

hotbox05

prius pistons can be ad cheaply if i can find a prius motor , problem is not many prius's get sent to graveyards.


and yeah i think igher comp pistons and competent tune is cali smart

to install pistons and tune would take a 3 - 5 days on their convenience , as far as service time and time spent maybe 2 days.

i need a new trans so i'd have the engine dropped while the new trans is being put in. save me some.

ProshopXB

Darren, he has a Yaris now correct? Talk about sneeking up on yeah and blowing you by...

hotbox05

nah he ditched the yaris idea still has his auto xb. i am VERY surprised that just bumping from 10.5 to 11 to one produced such a huge gain. i'm guessing piston design as well as the up in compression is helping him.



i on the other hand am looking at buying a yaris now.(in addition to , NOTreplacing my xB) lol

RTon20s

Nice. I just read the club xB thread. This is the most hopeful I have been for the xB in a long time. (Being in CA and all.) Well, all except for the $5k bill that is. There is no way I could sink that into my new box just for some pistons and e-manage. Then again, there was probably a whole lot of money spent on the custom pistons and all of that labor for install and tuning.

By the way... I checked car-part.com for you Darren. Looks like there is a complete 1NZFXE in Arizona for $468. You could probabaly get the whole motor for less than a set of custom pistons.

OK... Now get on this, and see how cheap you can get it done. I should be ordering my xB within the next couple of months.

ProshopXB

5k for 11to1 pistons and emanage?? ZPI all motor 11to1 pistons are only $595 and Emanage Ultimate is $595. Did he have rods made, a P&P done or a new head done. Wow thats alot of money for somthing he could have gotten way cheaper. But it is his money and he can spend it how ever he likes.

MattyRattyPoo

YEa I dont know where he went but it sounded way to much! Good info from him and he seems happy with the power gains.

jct

i take it you have too use a higher octane? like 89 or 93

ProshopXB

If he's happy then that is all that matters.

DOHCtorJT

The general rule of thumb is that 1 full compression point increase will equal a 4% gain.

So going from 10.5:1 to 11:1 should only net about 2hp.

RTon20s

Another question, since I am a total noobie to this extent of modification.

I found the following formula online...

(boost psi / 14.7) +1 x compression ratio = effective compression ratio

(I understand that the 14.7 represents 1 bar.)

Assuming this is correct, this is what I get given the ZPI turbo...

(7.7 / 14.7) + 1 x 10.5 = 15.86:1 effective compression ratio

And the Greddy Turbo...

(6? / 14.7) + 1 x 10.5 = 14.79:1 effective compression ratio

Now ZPI claimed that they ran their turbo on the car with NO E-Manage. Now I don't know that I completely believe all of ZPI's claims yet, but that was their statement. And the Greddy Turbo comes with e-manage, but is it actually tuned? Or is it just there for you to custom tune?

Anyway... this leads me to my question in a round about way. What are the chances of running pistons that bump the compression up to 11:1 or even 12.5:1 from the Prius and not absolutely having to run engine management?

Don't get me wrong, if I attempted to go N/A I would definitely get it tuned. But I wondering if I could do the piston swap, etc. myself and then just pay to have the car dynoed and tuned.

Just wanting to get your thoughts.