I would buy a remanufactured engine. If you can swing it, a reman JCW engine. Going over 18psi seems to be the pivotal point of having a reliable tuned N14 MINI engine and having a ticking time bomb where the pistons are just barely hanging on. Doing a custom build is going to cost more than you want to realize. It will be a fun project, but you'll be spending over $8K to do it right.

 

Well explain then.

 

Here.

 

Lmao.

 

My understanding is:

Forged pistons are generally stronger than cast. This can allow them to be made lighter, but they are not always.

Forged pistons hold up better to heat.

Forged pistons expand more than hypereutectic cast pistons when heated. So they tend to "slap" when cold much more. They can also suffer from extra blow-by (combustion chamber gases being pushed into the crankcase) when they are cold due to this.

Forged pistons tend to be rather more expensive than cast ones.

In N/A engines, at least, they are not usually considered worthwhile because of the cost and the extra noise and blow-by. Turbo motors may be an exception. Race motors can definitely be exceptions, because noise and blow-by are acceptable compromises for a race car if the parts are lighter and can be made to rev faster.

 

Sorry couldn't resist.

I guess I will share my knowledge with you guys. Yeah actually I don't feel like explaining. so you get basics.

1. The metal used in forged pistons is denser thus more heavy for equal amount.
2. Forged pistons are actually weaker then cast so they can deform instead of crack.
3. Forged pistons absorbe more heat so they will expand and contract more.

 

I must disagree with some of what you say.

 

You can't disagree with fact, well I guess you can but.... I guess you could argue the semantics of the word "strength" but either way it means the same thing. But to prevent that I will say cast pistons are more brittle because of the composition of the metal. Cast pistons are more malleable, so they can resist knock event better then the more brittle cast pistons. aka "Stronger" but not "stronger"

 

For your reading pleasure adn if you need more let me know.


"Forged" pistons are mechanically shaped into a piston shape. They are hammered, pressed (forged) into a mold forming the piston in turn removing any possible porosity and also pushes the alloy grains together tighter than can be achieved by simple casting alone. The result is a much stronger material.
A "Cast" shaped component means that the material has been melted and then poured into a mold that basically shapes the piston. The advantages are many, for example: a possibility to add other components like silicone, carbon, zinc and so on in order to gain certain properties. The aluminum itself doesn't build up inner tension as much. It is cheap. The density of the material doesn't increase which means it could be kept light. There are disadvantages also, of course. The piston will be weaker in structure. It is often heavier since the manufacturer has to increase wall thickness in order to achieve sufficient strength. The heat expansion cannot be controlled and is therefore often not completely round since the piston pin requires some material on the inside. They are also produced in bulk with most manufacturers only producing sizes that are close to factory specifications. This also makes them more affordable.


http://victorylibrary.com/mopar/billet-c.htm
http://www.shophemi.com/t-Advantages...d-Pistons.aspx

 

Here is a great video with in depth information


http://www.onallcylinders.com/2012/0...-cast-pistons/

 

So you tell me a bunch of stuff I already know. Like I said you can only argue the semantics of strength. Do you really want me to explain it to you? Im annoyed at this point so I will. Only one questions for you. What is your profession? It might help me word it in better terms.

 

Lmao

 

The stock mini pistons are cast hypertonic pistons, so they contain a percentage of silicon among other things. It will have a lower thermal expansion.

One type of forged piston is made from 2618 alloy this contains less then 2% silicon. It will have a greater thermal expansion when heated. (this is what I have in my car)

The stock mini pistons are harder then forged 2618 alloy pistons. So if you hit them both a hammer at equal force the stock piston would sustain more damage then the 2618 alloy piston. This is because the 2618 alloy piston is softer and can deform during the event. This is the "simulation" of knock.

I will take blame for the confusion and admit in the context used I was indeed wrong. When I was saying stronger I met harder, and by weaker I met softer. So that was my fault and I was wrong

To clear up the things I said if you have two identical pistons and one is forged the forged one will weigh more because it is more dense.
It should of read "forged pistons are actually softer then cast so they can deform instead of crack".
Forged pistons retain more heat because the content of metal is higher and metal has a greater specific heat then silicon.

 

We were not talking stock MINI pistons. We are talking forged pistons. But since you talk alloys now.

Agreed. This denting is better then shattering inside your engine. So they are stronger in the sense they won't explode internally.

4032 Alloy This alloy has a silicone content of around 11% which allows very tight clearances, while providing a significant improvement in strength over a cast piston. These pistons are suitable for moderate performance applications.
2618 Alloy This alloy contains less than 2% silicone, providing the ultimate in piston strength at very high power levels. The 2% silicone content is still sufficient to allow a tight piston-to-bore clearance. These pistons are suitable for extreme applications, and this is the same alloy that can be found inside 6000 kW Top Fuel drag engines

Also The high silicon content of cast pistons makes them brittle compared to forged pistons.

So again we can agree on some of this. So back to the OP's question. He should IMO get forged pistons and not go back to MINI pistons.

 

Agreed. We are on the same page. My fault with the wording. I will also side with you about forged pistons being better. That is the reason I got them. Choosing between 4032 and 2618 is a personal preference. It was a difficult choice for me. I originally went with 4032 but he milling was not perfect so I sent them back and ordered 2618.

 

I am glad you worded it for me to understand. LOL NO hard feelings it was fun.

 

Dumb mistake on my part. But you can see how I was associating strong with hard and week with soft. My poor english skill overpower my technical skills yet again.

 

No worries. Its all good. Now go motor on and find another MINI to wave to.

 

I did and they didn't wave back! Twas bull crap.

 

That just annoys me. I think when buying a MINI is should be a requirement and be put in writing that they agree to pay attention to other MINI owners and WAVE.

 

I know. They must not of been a enthusiast, most people around here recognize my car.

 

Wow, thanks for all your help Braminator and MNIPWR!

I still waiting news from my local dealer, but will probably don't have anything until the next week because of the current holidays here, the holy week. I'll keep you posted.

 

Well, got some new from the dealer, two pistons are cracked and need replace.

Here are the pictures they sent me:

http://s8.postimg.org/iiyky61sl/P1000988.jpg
http://s8.postimg.org/w15hagdxx/P1000989.jpg
http://s8.postimg.org/5u4aehvo5/P1000991.jpg
http://s8.postimg.org/4gcnj6wet/P1000992.jpg
http://s8.postimg.org/sldd0wgph/P1010011.jpg
http://s8.postimg.org/bm4eln5hx/P1010012.jpg
http://s8.postimg.org/qjcvmniqd/P1010013.jpg
http://s8.postimg.org/ce72ku9p1/P1010014_1.jpg
http://s8.postimg.org/goqbu645x/P1010014.jpg

 

Wow, that is bad.

 

WTF is all I can say. Keep us posted.