Would you guys prefer FB20 or FB25 for NA FT?

[Dimman]

Originally Posted by Exage

Ideally and put very simply a de-stroked (and 1.5-1.6 rod to stroke) FB25, with a beefier/smaller cylinder bore reduced to 2.0L with a higher compression ratio (11:1-12:1). AVCS, and D-4S. Revised heads, intake and exhaust manifold, camshaft. Optimized ignition and fuel mapping.

Interesting idea, EJ's can mix and match cranks to fiddle with odd combinations. However the FB's are both 90mm stroke, and probably share the same crank. Unless a smaller FB that can share its crank is on the way I don't see a de-stroked FB25 happening.

Oh wait... You could be on to something if they already have that in mind for the next gen WRX/STi!

[-TokenSX-]

Originally Posted by Fortunate Few

2.0T is what im hoping for. I don't think i'd go for 2.5.

Same here 100% on dat : D

[Exage]

Originally Posted by tranzformer

This might be a dumb question, but what is gained by destroking an engine (say from 2.5L to 2.0L) vs. boring a 1.8L to 2.0L? Do you gain something in the process (durability, revs, tq....etc.) or is a 2.0L a 2.0L?

I've been tooting the rod-stroke ratio horn for a couple days now. De-stroking would cause less mean (aka average) piston speed at the cost of less displacement however you can put in a longer connecting rod if it's up to strength and the engine would be able to withstand and produce peak horsepower at a higher rpm, I also stated a smaller bore then the FB25 94mm just to beef it up.

Any increase and decrease in stroke or bore will effect the ultimate torque and power of the engine.

Is a 2.0L a 2.0L. No! Look at my 2ZZ-GE Vs. a 1ZZ-FE. Both displace 1.8L, both are very different animals... I'd be happy to try and explain it in more detail on the engine tech thread if you'd like!

@Dimman I doubt it too, but you never know what will happen. I simply thought up this engine months ago trying to reverse engineer the FB20 to make it high rpm suitable! Seeing as the EJ were usually over square led to this idea.

[NESW20]

yeah, it's really incredible how important that ratio is. i remember when i learned about it my brain more or less exploded, haha.

[ryun84]

Shouldn't this be a poll? I'd pick whichever engine revs higher. If the 2.5L can be made to rev just as high as the 2.0L can (and I don't know if that is possible), then I'd go for the larger displacement because the American in me just likes it that way.

[Allch Chcar]

Originally Posted by Dimman

Interesting idea, EJ's can mix and match cranks to fiddle with odd combinations. However the FB's are both 90mm stroke, and probably share the same crank. Unless a smaller FB that can share its crank is on the way I don't see a de-stroked FB25 happening.

Oh wait... You could be on to something if they already have that in mind for the next gen WRX/STi!

Not if Subaru moves foward with downsizing everything. They are making a 1.6L Turbo for the next gen Impreza according to rumors.

I think the FB with 2 liters will be plenty, there's always the turbo option. I'll probably wait and see what becomes of the 1.6Liter turbo though.

[Dimman]

Originally Posted by Allch Chcar

Not if Subaru moves foward with downsizing everything. They are making a 1.6L Turbo for the next gen Impreza according to rumors.

I think the FB with 2 liters will be plenty, there's always the turbo option. I'll probably wait and see what becomes of the 1.6Liter turbo though.

I must've been sleeping to miss that 1.6T rumour. Maybe they are getting back into the WRC and are homologating a motor?

Could end up being that an FB25's bore with this 1.6's crank (assuming it's a high performance short stroke motor to meet WRC requirements) could end up being 2.0L.

But I'm not seeing that happening right away if the 1.6T is still in the rumour stage.

[Allch Chcar]

Originally Posted by Dimman

I must've been sleeping to miss that 1.6T rumour. Maybe they are getting back into the WRC and are homologating a motor?

Could end up being that an FB25's bore with this 1.6's crank (assuming it's a high performance short stroke motor to meet WRC requirements) could end up being 2.0L.

But I'm not seeing that happening right away if the 1.6T is still in the rumour stage.

Yes it's all about the WRC. And it is still very much just a rumor as far as I know. It was announced about when they announced the jointly built Impreza STi CS400 with Cosworth. I tried to trace the rumor but it leads into Italian websites and dead ends at http://www.auto.it/autosprint/ so far. They're actually suggesting sometime in 2012 :crazy: and one site went so far as to suggest it would replace the base 1.5L engine which is pretty far out there for a rumor .

[ljstella]

Originally Posted by Allch Chcar

Yes it's all about the WRC. And it is still very much just a rumor as far as I know. It was announced about when they announced the jointly built Impreza STi CS400 with Cosworth. I tried to trace the rumor but it leads into Italian websites and dead ends at http://www.auto.it/autosprint/ so far. They're actually suggesting sometime in 2012 :crazy: and one site went so far as to suggest it would replace the base 1.5L engine which is pretty far out there for a rumor .

I still don't know how credible that would be, considering the new WRC formula mandates an inline 4, which would rule out a boxer engine. While its possible, I wouldn't expect to see it here in the US.

[aliphian]

Originally Posted by ljstella

I still don't know how credible that would be, considering the new WRC formula mandates an inline 4, which would rule out a boxer engine. While its possible, I wouldn't expect to see it here in the US.

Wouldn't it be IRONIC if they used a Toyota inline 4 for the new STI.

[ryun84]

I'd jump right on it if Subaru used Toyota's inline 6 for their new STI! o_O

[SUB-FT86]

2.5l>2.0T>2.0. The reason I put turbo in the middle is because of possible extra reliability and maintenance issues. I have a 2.0 in a 2800 lb car so I don't think I would be more impressed.

[ichitaka05]

Originally Posted by Allch Chcar

Not if Subaru moves foward with downsizing everything. They are making a 1.6L Turbo for the next gen Impreza according to rumors.

I think the FB with 2 liters will be plenty, there's always the turbo option. I'll probably wait and see what becomes of the 1.6Liter turbo though.

Yeah but sadly you won't see that ver here in US. Japan have been selling 1.5L ver over in Japan for a while, but not in US.

[Allch Chcar]

Originally Posted by ichitaka05

Yeah but sadly you won't see that ver here in US. Japan have been selling 1.5L ver over in Japan for a while, but not in US.

Yeah but but this one haz a turbo .