Dudas STI

[elultimo]

Hombre yo creo que 350CV bien metidos no tiene que dar problemas.

Y esto es lo que peta forzando ( Rush Works habla de fatiga de material; pero vamos, antes de que pase, metes unos wiseco y a rodar tranquilo.

[castigador]

esto pasa tambien en los ej20 ? por que segun he leido en algunos sitios dicen que en el sti los pistones son forjados .

[Evolaco]

madre de dios como esta el piston :shock:  si te pasa eso habria que rectificar cilindros y todo no? pero eso con 1,5b puede pasar? yo en el evo iba a 1,8 y sin problemas

[WAGON555]

esto pasa tambien en los ej20 ? por que segun he leido en algunos sitios dicen que en el sti los pistones son forjados .

Yo creo recordar que no son forjados al menos los europeos....los jdm ya es posible que si vayan forjados....

[milikisti]

esto pasa tambien en los ej20 ? por que segun he leido en algunos sitios dicen que en el sti los pistones son forjados .

En los nuestros sí son forjados.

[milikisti]

http://www.goauto.com.au/mellor/mellor. ... C100002E36

[elultimo]

La foto es de un pistón de un STI huevo; y los pistones del STi, yo tengo entendido que no son forjados, forjados, comparados con unos CP, wiseco, o mahle, ni por aleación, ni método de fabricación. Si te ponen uno OEM y uno de los otros en la mano lo notas, y ya funcionando en frio y caliente también se nota.

[castigador]

Echale un vistacillo a este articulo que habla sobre "los mitos" acerca de estos motores

http://www.importtuner.com/tech/impp_11 ... ewall.html

aki viene todo especificado al detalle por potencias .
segun dicen el gran problema de que pases esas cosas es por culpa de las repros mal hechas por ingenieros de bar    

respecto a si los pistones del ej20 son forjados como todos sabemos hay muchas clases de forgados , esta claro que no seran tan fuertes como los que venden para potencias de 400 y 500 o mas hp  pero segun en muchos articulos la diferencia del ej20 del wrx y el sti entre otras cosas son sus pistones que son forgados por fabrica para el mayor par y potencia.

[elultimo]

hay una realidad los segmentos de los pistones son muy finos.

*Rush Work ( la foto del pistón es suya) dice:

"El problema que se vio al desmontar era que los pistones se habian roto, otra vez, por fatiga de material, no por un exceso de temperatura, basicamente estos pistones OEM estan pensados para presiones de serie, y aveces asi, incluso fallan".

*Clark Tuner,  preparador bastante conocido en foros USA, dice lo siguiente:
http:://www.facebook.com/clarkturnertuning

Dais al traductor que se entiende ( termina diciendo que la solución es forjar):

"Clark Turner  
I think most people on this forum have cracked ring lands and dont even know it. I think alot of people would be suprised if they did a leak down test. Many times the car runs fine and does not burn oil and does not smoke.

 The pistons are weak and something needs to be done about it. Subaru is in a rock and a hard place when it comes to this issue.

 The old version 7 JDM motor had Forged pistons. The pistons where very strong. The trouble with this is that the forged pistons expand alot at high temps. They need to be run loose when cold so they can have room in the bore to expand. Subaru ran these pistons super tight. As a result, Alot of high hp cars and or road/rally V7 engines scuffed the bores. Cant run them with more clearance because the cold start emissions would be to high.

 They then went to the Hyper cast piston. This piston can run tight and has very little blow by. So little that it was common for me to find V8 STI motors with 0! leak down.. NONE. Since they where small 2.0 pistons they where stronge enough.

 The US 2.0 WRX was much lower power and the pistons being small where plenty strong. The rods are weaker then the pistons in the 205 engine.


 When the US sti came to the us, Subaru realized the gas is crap. The 2.0 would have never made enough power to keep up with the EVO. ( evo having long stroke and small bore)The solution was the EJ257. THis engine used the 2.5 sized piston. They kept the Same Hyper cast style piston. Since this motor is stretched beyond its design limits (in my opinion) they ended up with a weak piston. The engine has a large bore and a short stroke. The real solution is to use a smaller piston with more stroke. This is not an option as the motor would be so wide that it would not fit in the Frame rails.

 I can tell you that the early 04 pistons where total crap. They changed the pistons and the mid to late 04s where better.

 05 and 06 seem to be "ok" in most cases but still not strong. THey had several diff pistons used in these motors also.

 All hell broke loose with the 07. This was about the worst engine. Many I attempted to tune where already blown. Stock cars had blown pistons. Tuned cars had blown pistons. I got to the point where I did not even want to tune them anymore because I knew it was a roll of the dice... and the blame would always be me. Not the piston.

 The 08 came out and I was excited.. Surely Subaru put in a stronger piston right? Wrong.. 08 stis are as bad as the 07 engines. They flat out scare me to tune. Lots of 08 STIs are running around right now 'running great" with blown pistons.

 I have one customer that had a totaly stock car with blown pistons. Subaru replaced the pistons.. not the motor. This motor ran for about 4 months and one piston blew. He then went to aftermarket pistons and I tuned the car with no issues.

 Lots of 08 STIs where blown because of the Factory FPR sticking. One second your at 11 to 1. Next second you are at 14 to 1! On boost! Oh no! Clark blew my motor.. Lots of stock cars had this issue. Something should really be done about this.

 Like I say.. Its a roll of the dice. I tuned RJs (MGI imports) 08 STI and he ran the one lap of america race without incident. That motor seems to be alive after 6000 miles of racing and hours at high speeds.

 The solution is to install Forged pistons and be done with it. Lots of people blame tunes and thats a fair blame. Lots of people blame the stock tune. Thats also fair.. But in the end.. Any real detonation will likely cause the piston to crack. If thats the fault of the stock tune, my tune or mechanical issues.. You still have a cracked piston.

 Clark "

[Blanco]

Putos segmentos!!!!!

La solución, pistones nuevos con segmentos y te olvidas!!!!! Y ya que abres.... Le metes tb las bielas!!!

Un saludo y esa es la única "pega" de los nuevos... Transmisiones, caja, bloque motor y demás SIN PROBLEMA !!!