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Old 07-30-2021, 10:46 PM   #1
sebastian323
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Default Best piston and rods for 300whp on EJ205 w/ VF39

What piston would be recommended for a daily driver car (it may be driven rough pretty often, i'm a young guy) at about 300 whp on a vf39 and STi pink injectors. Is there some sort of aftermarket , non forged hyper-eutectic piston I can look into? Also, which connecting rods are recommended. I have all the stock engine parts in good condition and re-using these is an option.
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Old 07-30-2021, 11:26 PM   #2
K3rm1tth3fr0g
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You'll pay about 50% of the cost of a forged block if you go with an OEM EJ25 shortblock and build from there.

And you get the torque from the 2.5L...

The ej205 just sucks.

For 300whp you do NOT need forged internals.

Last edited by K3rm1tth3fr0g; 07-30-2021 at 11:52 PM.
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Old 09-06-2021, 10:44 AM   #3
dzltreg
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Quote:
Originally Posted by K3rm1tth3fr0g View Post
You'll pay about 50% of the cost of a forged block if you go with an OEM EJ25 shortblock and build from there.

And you get the torque from the 2.5L...

The ej205 just sucks.

For 300whp you do NOT need forged internals.
THIS!

Do not waste your time building the 205. Not worth your time or money.
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Old 09-06-2021, 11:11 AM   #4
snow_bound26
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EJ205 pistons are fine. They don't have the ringland issue the 255/257 does. The weak bits are the rods and oil pan, pick up and baffle. Rods tend to bend/break around the 350wtq range depending on how aggressive the tune is. All EJ engines have issues with spinning bearings when going for too much low end torque. The 205 is easier to oil starve because of the flat oil pan. The pick up and baffle are the same construction as the 255/257 variants.

So if you want your 205 to be reliable (which it generally has better reliability than the 255/257) then get an 06+ STi oil pan, Killer B pick up and baffle, a quality tune and call it a day. You can run 300hp on the 205 for many many miles as long as you do proper maintenance and use quality fluids.

And with the parts you mentioned, you probably won't see 300whp/wtq. More likely 265-285 depending on how the dyno is set up, your elevation, fuel quality, air temp, humidity, sheer luck, and a billion other factors that will influence your tune.
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Old 09-06-2021, 02:38 PM   #5
benflynn
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Pistons if you want to drive it hard with even a td04
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Old 09-06-2021, 02:46 PM   #6
benflynn
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I broke my piston with vf39, itís cheaper to fix it before it takes out another 1k$ worth of parts
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Old 09-10-2021, 04:08 PM   #7
sebastian323
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Quote:
Originally Posted by snow_bound26 View Post
EJ205 pistons are fine. They don't have the ringland issue the 255/257 does. The weak bits are the rods and oil pan, pick up and baffle. Rods tend to bend/break around the 350wtq range depending on how aggressive the tune is. All EJ engines have issues with spinning bearings when going for too much low end torque. The 205 is easier to oil starve because of the flat oil pan. The pick up and baffle are the same construction as the 255/257 variants.

So if you want your 205 to be reliable (which it generally has better reliability than the 255/257) then get an 06+ STi oil pan, Killer B pick up and baffle, a quality tune and call it a day. You can run 300hp on the 205 for many many miles as long as you do proper maintenance and use quality fluids.

And with the parts you mentioned, you probably won't see 300whp/wtq. More likely 265-285 depending on how the dyno is set up, your elevation, fuel quality, air temp, humidity, sheer luck, and a billion other factors that will influence your tune.



I could potentially do rods and keep the stock pistons for more reliability. i take it the bearings fail due to oil starvation and not excessive load ?
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Old 09-10-2021, 09:46 PM   #8
snow_bound26
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Quote:
Originally Posted by sebastian323 View Post
I could potentially do rods and keep the stock pistons for more reliability. i take it the bearings fail due to oil starvation and not excessive load ?


Either can cause bearing failure. One just takes longer than the other.

To change the rods you have to split the block. Not worth it unless you're doing a full rebuild anyway given the labor costs. Point was more you don't need to do anything for the power goals your aiming for.
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Old 09-14-2021, 09:45 AM   #9
Homemade WRX
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EJ205 has a long history of not having pistons problems. People that break 205 pistons usually have a tuning problem. For a DD car, I would rather have amply strong cast pistons versus loose aftermarket forge pistons.

With that being said, bone stock EJ205's have been making 300 whp with VF turbos since they came over here in 2001. Stock bottom end is completely fine for this power.

Refresh & Rebuild Scenario: If you are going low buck, I'd go ahead and pick up used EJ255/257 rods. The newer (circa 2004 or 2005) 75mm cranks do have improved oiling. The older EJ20 and all EJ25 cranks have the old oiling layout.

EJ25 Block Swap: As for the EJ255/257 block, it comes with a bump in compression ratio, so either forged pistons or cylinder head machining is required to properly fix the issue they have.

2.1 Stroker on a Budget: pick up a used EJ257 crank and rods, then your choice of stroker pistons. The shorter rod ratio and longer stroke does make it more punchy.

Last edited by Homemade WRX; 09-15-2021 at 10:33 AM.
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Old 10-13-2021, 09:48 PM   #10
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Quote:
Originally Posted by K3rm1tth3fr0g View Post
You'll pay about 50% of the cost of a forged block if you go with an OEM EJ25 shortblock and build from there.

And you get the torque from the 2.5L...

The ej205 just sucks.

For 300whp you do NOT need forged internals.
Alright, I will tip my buddy about OEM EJ25 shortblock for his incoming 300whp project. He plans to DD it for now but future plans may change. Need to finish installing the bumper, shocks, and winch on the Wrangler this week before we can clear the garage for the new project.
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