Forged Pistons vs OEM 2jz

Hello, I am trying to build a street 2jz around 500-600hp mark. Currently deciding on what pistons to use. I know that the cast pistons that come oem in the 2jz are pretty good. However, I had questions with the forged aftermarket units. There exists 2618 alloy and 4032 alloy forged pistons. I am looking for longevity and reliability out of this engine and am leaning toward the 4032 due to its tighter wall clearance.

So is there any benefit of running 4032 over oem pistons in terms of longevity? Will the 4032 wear out quicker or will it have similar wear characteristics as an oem piston? Is it even worth getting forged pistons? Any insight would be appreciated!

We managed to run 2jz with stock pistons as fast as 8.7 ET on 4wd setup with ethanol fuel. They should be absolutely fine for your power goal - I wouldn't even bother changing them for 600 hp providing that the ECU tuner knows exactly how to do his job properly. If the fuel in your area isn't high octane one then it would make sense to switch to forged pistons as they are a little bit more forgiving to tuning mistakes and can withstand a bit more abuse than stock ones as far as low level knock resistance...

Do you know if 4032 forged would last as long as oem in a daily driven car given the tunr and everything is spot on?

Also what would count as high octane? Would 91 be high enough?

It makes no difference in terms of pistons longevity what type you use as long as piston to wall clearance is correct and their type is correctly chosen for power level goal- if all done properly they all will last very long time.

For 600hp with stock pistons 93 octane fuel would be much better than 91 bearing in mind that octane rating decreases over time so initial higher octane rating is your safety margin.

I assume that's the USA PON 91? That would normally be regarded as a low-ish octane fuel - around 95 RON - if you can find 93/94 it would be better and an Exx "should" be a suitable option, but something you need to check on as different companies, and states, have different "fudge factors" on the actual ethanol content and octane numbers. My "shopping basket" specifies 98 RON but the local E10 meets that requirement, and is approved for the vehicle.

You can still make those numbers, but might be wise to drop the mechanical compression ratio if practical - not something I would worry too much about, unless changing pistons, anyway.

As Shota said, correctly clearanced the pistons should last at least as long as OEM - ring wear may be more of a concern, so the time spent on ring selection and getting a GOOD shop to do any boring/honing will help. I assume you will be running a good air filter, as possibly the biggest factor, other than bore wash, on ring wear and bore scouring is dust in the air!

FORGOT! As with any engine, getting a good, and experienced, tuner is often the difference between a sweet, long lasting ride, and scrap metal.

There are two words that are abreviated to "pro'", the first is "professional", which basically means being paid for their work, the second is "proficient", which basically means skilled or competent - there are WAY too many "pro's" who fall into the first category, but fall short in the second.

Interesting. From what ive seen I would have thought forged pistons like 2618 have to run larger wall clearance and therefore would cause piston slap on cold starts. Multiply that with how many times an engine is started in its design lifetime and I would therefore assume more wear on the bore and pistons as a result of this. However, Im not sure how wall clearance on 4032 pistons would compare to oem.

Is wall clearance a major factor in engine wear or is there another larger contributing factor?

Piston isn't just hanging in the bore but suspended by piston rings. Piston slap is caused by piston skirt which doesn't have much effect on top of cylinder bore that matters the most.

Engine oil quality, clearance and timely changing is crucial factor in piston rings and cylinder walls wear. Also powrr level and RPM play huge role in that too.

Piston to wall clearance is not realated to wearing things a lot but engine safety...

Cylinder wall clearance is to allow for piston expansion as they heat up, different alloys have different expansion rates, and that's why the, cold, clearances are different. The crown/top of the piston runs hotter than the skirts, so that's why the shape of the pistons isn't uniform.

When the pistons are cold, or below normal operating operating temperature, the clearances are still a bit on the wide side, and it's this clearance that allows them to "slap" the bores as they move from the minor to the major thrust faces at TDC.

I would disagree about the rings affecting this, as they are specifically required to move freely within their grooves, but that may be a language mis-translation?

Maybe it's my poor English but what i meant is described here by japanese piston rings production company (function 4).

https://www.tpr.co.jp/tp_e/products/powertrain/pistonring/about.html

By the way- at the moment I'm refreshing 25 years old 4g64 engine with 200 000 miles on it and the pistons skirts show exactly where the wear is taking place on them (picture attached) whilst the cylinder is still in the absolutely round shape with no wear at all.

Ah, I see, thank you.

Привет. Смотрю ты по фконам ребятам подсказывал. Сталкивался с настройкой фконов?

Да, сталкивался.

Можешь мне помочь с 3.4. Докатать и ввт настроить?

Извини, но не смогу- очень занят.

А я не тороплю еще вся зима в переди. Хотя бы глянь карту обогащения по дросселю не могу ей ума дать

Hi Rizwan,

Thankyou for asking this question. I was going to ask the same one myself.

One thing though, I was always told that 2JZ engines had forged pistons from the factory. I'd assume these would have to be 4032 as no mainstream OEM manufacturer is going to use 2618.

I was told this was why 2JZ's are able to handle such crazy amounts of power out of the box. Correct me if I'm wrong.