Hi Guys

I've got a 2003 impreza sti that i'm gonna put an EJ257 bottom end into, however i want to fit forged pistons, anyone got any tips on which ones to go for and where to get them from, planning on strapping a MD321T turbo to it.

Thanks from ross

 

view my scooby

basically , if your ordering the turbo from Lateral Performance then ask Mark about the pistons , also consider better rods as well . . . oh, and bearings, head bolts etc etc

 

I'm currently running my standard EJ257 bottom end at 452bhp at 1.4 bar from a rotated GT30R setup. I'm pretty much on the limit I would imagine for the stock bottom end.

It depends how far you want to take the car and how much work you want to do.

If you don't want to split the block then I'd suggest some drop in Wiseco's.

If you are prepared to split the block get some ACL race bearings (main and big ends) crower or Pauter rods and again some wisceo pistons.
If you're going for say 500bhp plus then you'll also need to look at strengthening the block with some sleeves. Either way get the blocked honed to suit the pistons and i'd suggest a clearance of three thou.

Mark at lateral will be able to supply all you need. I would also recommend some ARP head studs and 1.6mm head gaskets.

Daz

 

Cheers guys,

I'm aiming for about 420bhp, I dont want to split the block but I definitely want stronger pistons but didn't know which ones would just drop in. I am also gonna fit arp head bolts and some kind of stronger head gasket.
Any more suggestions guys.

Cheers from ross

 

The Wiseco drop ins are just the ticket then.

If your using heads that havent been machined to suit the 2.5 then use a 1.6mm triple steel subaru item. Those and the 11mm arp studs and you'll not go far wrong.

I'd also consider getting the RCMS modified oil pump too.

Daz

 

can't go far wrong wityh the Mahle drop-in pistons, decent value for money too..............

alyn

 

has there been a design change in the Mahle since 2006 for the 2.5 then?

Simon

 

Depending what dish size the pistons you use will determine the thickness of head gasket to get the correct compression.

I have Wiseco pistons and am using cometic 1.3mm head gasket to give approx 8.2 compression.

 

I'll be more specific. These Wiseco Pistons part number K598M995 will give you a compression ratio of 8.5:1 with a 1.6mm head gasket on 2.0L heads.

 

Can't be, they are the same pistons I have and they have -19cc dish.

 

Also just to note, the bores on an EJ257 are Graded A & B, I was advised the when using the Wiseco 'drop ins' you should use block with B graded bores (I may have this the wrong way round so someone please tell me if I'm wrong)

thanks

 

I got my gaskets from RCMS. I showed them those piston specs from the link I copied the part number from. They tapped the dish size, deck height etc into their spreadsheet and worked out gasket size and comp ratio.

If it was me working this out i'd be doubting myself right now but as they did the maths for me I stand by what I say.

Daz

 

Are you sure that not just for the standard EJ257 pistons?, am pretty sure with Wiseco -19cc dish, 2.0l heads 49 cc (IIRC) and 1.6 mm gaskets, compression would be less than 8.0.

Someone please correct me if I'm going wrong.

Obviously not wanting to question information you have had from RCMS, but if it is correct, then this means my CR stands at 8.72,(1.3mm gasket) and my brothers 8.88 (1.1mm gasket), and really do not think the company that supplied the gaskets would recommend them for high boost engines.

 

go on jay

 

I would eat my hat if your engine has a compression of 8.72 Jay..

It did not react like that when mapping it..

Simon

 

Weird one this then. Although I am using the standard bottom end, at the time of me buying the gaskets I was going to use the wisecos discussed here.

I was discussing my options with both Matt and Oli and the Wiseco pistons are a very similar spec to their Omega offering.

I showed them the link to the supplier I use who list all the specs of the pistons. With this information Matt entered the variables into his spread sheet and came up with a comp ratio and 1.6mm gaskets.

So I bought the twisted turbo kit, head gaskets, seals o rings etc.

However I ended up deciding not to split the block I then used the 1.6mm gaskets on the standard block.

1 thing I am 100 percent on is that the gasket sizes were worked out with the Wisecos in mind and NOT the OEM subaru items.

I'll recheck when and if I go forged on the 2.5 but i am favouring the closed 2.33 at the mo.

However that said the stock bottom end with 1.6mm gaskets dyno'd at
452 bhp at 6480rpm last week with 1.4bar using a GT30R (0.82 ex housing). Its also done over 5000 miles like this and is used on a daily basis.