The FB25

[GEE-OTTO]

So I guess it will be time to say bye bye to the beloved EJ251/3 for the Non turbo guys going forward with the 12' lineups .

 

From what I gather the FB20 and FB25 are quite the producers. The bore is down to 94mm now and the rods are similar to the EZ36R. The smaller bore is to help reduce cold start emissions.

 

I think in the non-turbo crowd was unhappy with tuning option post 2006 they can literally forget about it in the years to come.

 

While the FB25 won't make more power than the EJ253 it is tuned to pour it on far earlier in the RPM range which you would think is the opposite given the difference btwn a EJ25D and a EJ251.

 

It is crazy the EJ253 had a 6 year run already Man soon they will be laying around like EJ22's and EJ251's.

[legacy360]

Then we can do this with the old EJ's

 

http://mychinaviews.com/wp-content/plugins/wp-o-matic/cache/7328a_ej25-coffee-table.jpg

[FLZ_Boy]

Has Subaru even announced that the 2012 Subaru models (besides the Forester) will be getting the FB25??

[fahr_side]

From what I gather the FB20 and FB25 are quite the producers. The bore is down to 94mm now and the rods are similar to the EZ36R.

Smaller bore is great for reducing tendency to detonate. OTOH the split cap rods are never going to be as strong as the traditional design, and we know from Subaru's own press releases the internals are built lighter to reduce losses and improve economy. Not good from a tuner's perspective. I don't expect this engine to be as tough as the EJ, and I predict that things like rods are going to need to be upgraded at lower power levels than present.

 

I'm waiting to see the direct-injection turbo versions.

[ehsnils]

Has Subaru even announced that the 2012 Subaru models (besides the Forester) will be getting the FB25??

 

They don't need to announce that, it will happen.

 

They are just doing a market test run on the Forester right now. If they don't get unexpected problems there the rest of the cars will follow.

[BigT]

has anybody done a theoretical comparison for tuning between the FB and EJ series?

[BAC5.2]

and I predict that things like rods are going to need to be upgraded at lower power levels than present.

 

Like the Mazdaspeed3.

 

300whp, then connecting rods decide that being bent is cooler than being straight.

[ehsnils]

has anybody done a theoretical comparison for tuning between the FB and EJ series?

 

One main difference for tuning is that the bore is narrower and the stroke is longer.

 

Bore x Stroke

FB: 94x90

EJ: 99.5x79

 

That means that the top torque will be at a lower rpm, and that they probably will be a little harder to tune. But you can always use a bigger turbo!

 

But there may be more to it, and to save fuel they may have selected lighter rods and pistons so you may need to replace those parts at an earlier stage.

 

And for the first generation of a new engine it's always tricky because there may be weaknesses that you can't predict - and they will probably blow up a few in a lab before they market a turbo version.

 

You can find more here: http://www.fhi.co.jp/english/contents/pdf_en_60853.pdf

[GTTuner]

The FB in it's present form will never be good for making power. Smaller piston pins, lighter rods, etc. I'm sure the turbo versions are not far behind, which would obiviously be strengthened.

[fahr_side]

One main difference for tuning is that the bore is narrower and the stroke is longer.

 

Bore x Stroke

FB: 94x90

EJ: 99.5x79

 

That means that the top torque will be at a lower rpm, and that they probably will be a little harder to tune. But you can always use a bigger turbo!

 

But there may be more to it, and to save fuel they may have selected lighter rods and pistons so you may need to replace those parts at an earlier stage.

 

And for the first generation of a new engine it's always tricky because there may be weaknesses that you can't predict - and they will probably blow up a few in a lab before they market a turbo version.

 

You can find more here: http://www.fhi.co.jp/english/contents/pdf_en_60853.pdf

 

I'm thinking in a way it will be easier to tune because the smaller bores will make it less prone to det, as long as they don't screw up the design of the heads.

 

OTOH it's clear they are reducing losses (and thus improving economy) by lightening the rotating assembly and this will no doubt lower the power levels at which the stock parts start breaking.

[_karu_]

Bringing this thread back to life.

 

I was just researching about the Forester and found out that the 2011+ uses FB25 engine. I was pretty stoked about the new design until I find out about the burning oil issue. 1 qt every 1,200 miles?

 

I love how the oil filter is on top, accessible from under the hood. Pretty cool.

[rkhousman]

Yeah the oil filter location is kinda cool! My neighbor just bought a 2013 OB and that was the first thing I noticed under the hood.

[_karu_]

^It reminded me of the old E36. Filter on top. Very easy to change.