club.liberty.asn.au

I bought a 2005 Lib GT but as the older models are still only 2 litre i was wanting to no if its possible to have it bored out to 2.5litre?

has anyone done this?

Easiest way to go would be to obtain a 257 short block direct from Subaru. Basically STi 2.5 forged bottom end and everything from your 2.0GT heads should bolt up. That way you get dual avcs, drive by wire etc retained, your 2.5 capacity and a good solid bottom end You would however also need a remap at the same time - hope you have $5-6k+ if you are planning to do it.....

get a JDM sti 207 bottom end and smash more boost in to it I suggest.

Isn't the only advantage of the 207 over the 20Y GT bottom end a lower compression ratio? Im fairly certain MY03-06 GT's had the forged bottom end just with slightly higher compression ratio for better off boost performance.

Or is that simply what you are suggesting the lower compression of the 207 to allow more boost?

If going to the effort of changing bottom ends for greater response, surely then the 257 would have to be a better option with a remap?

Hotwire wrote:Easiest way to go would be to obtain a 257 short block direct from Subaru. Basically STi 2.5 forged bottom end and everything from your 2.0GT heads should bolt up. That way you get dual avcs, drive by wire etc retained, your 2.5 capacity and a good solid bottom end You would however also need a remap at the same time - hope you have $5-6k+ if you are planning to do it.....

The STi 2.5L bottom end doesn't come with forged pistons (at least Oz delivered engines don't) the pistons are are only heat treated or something, so you are limited to about 16 psi. Anything more fries piston rings. You would be better off forging the current 2.0L block and winding up the boost! Cost would still be high with either option!

adhar wrote:

Hotwire wrote:Easiest way to go would be to obtain a 257 short block direct from Subaru. Basically STi 2.5 forged bottom end and everything from your 2.0GT heads should bolt up. That way you get dual avcs, drive by wire etc retained, your 2.5 capacity and a good solid bottom end You would however also need a remap at the same time - hope you have $5-6k+ if you are planning to do it.....

The STi 2.5L bottom end doesn't come with forged pistons (at least Oz delivered engines don't) the pistons are are only heat treated or something, so you are limited to about 16 psi. Anything more fries piston rings. You would be better off forging the current 2.0L block and winding up the boost! Cost would still be high with either option!

Ok well there you go - I thought the 257 was forged like the 207 block - learn something every day! In that case, a nice new 257 semi closed deck block and fit forged pistons and go for your life!

Hotwire wrote:

adhar wrote:

Hotwire wrote:Easiest way to go would be to obtain a 257 short block direct from Subaru. Basically STi 2.5 forged bottom end and everything from your 2.0GT heads should bolt up. That way you get dual avcs, drive by wire etc retained, your 2.5 capacity and a good solid bottom end You would however also need a remap at the same time - hope you have $5-6k+ if you are planning to do it.....

The STi 2.5L bottom end doesn't come with forged pistons (at least Oz delivered engines don't) the pistons are are only heat treated or something, so you are limited to about 16 psi. Anything more fries piston rings. You would be better off forging the current 2.0L block and winding up the boost! Cost would still be high with either option!

Ok well there you go - I thought the 257 was forged like the 207 block - learn something every day! In that case, a nice new 257 semi closed deck block and fit forged pistons and go for your life!

Yes that is even better! 257 with forgies, big turbo and pump up the boost to 27psi! mmmmm... nothing, nothing, nothing, EVERTHING!

Or another option is to find a well priced second hand 2.0L bottom end from the v5 or v6 STi and fit that up. It came with forged pistons but not rods as standard. Still good for about 21 psi.

adhar wrote:Yes that is even better! 257 with forgies, big turbo and pump up the boost to 27psi! mmmmm... nothing, nothing, nothing, EVERTHING!

Or another option is to find a well priced second hand 2.0L bottom end from the v5 or v6 STi and fit that up. It came with forged pistons but not rods as standard. Still good for about 21 psi.

So what do the EJ20X and EJ20Y have in the way of pistons rods do you know? I always though they had the same forged bottom end as the EJ207 (V5/V6 STi) but with a slightly higher compression ratio? I read this some time ago from someone who seemed to know what they were talking about...

LGT engine has 9.5:1 compression ratio (peak torque @ 2400 RPM) and 12mm oil pump for 4x AVCS cams.

cadud2000 wrote:I bought a 2005 Lib GT but as the older models are still only 2 litre i was wanting to no if its possible to have it bored out to 2.5litre?

has anyone done this?

Basically no you can't bore the engine out to 2.5l as it just doesn't have the physical dimensions. First you would have to bore it out almost 7mm which would pretty much wreck the liners. Even if you could bore it out that much you'd still be short as the stroke on the 2.5 is 4mm longer so you'd have to fit a 2.5l crank. At the end of the day, depending on budget and what you want from the engine getting a 2.5l bottom end, block, crank, rods, and pistons is going to be the easiest answer if you really want the 2.5l capacity. The other thing is to have your 2.0l tuned, ie more boost, timing, fuel etc. The 2.0l is arguably the better engine as it revs better than the 2.5. JDM cars, both Legacy and Impreza still run the 2.0 even the STi models it's only here and I think some USDM models that get the 2.5

well that sucks. I thought the piston stroke was the same. that sucks there is a 4mm difference. Why did subaru change the GT model from 2litre motor to a 2.5 in the newer models?

Was there a reason they changed? or just because they can?

Wanna swap for my 2.5 N/A and then throw a couple of turbos on it? I'd be happy to have your motor, lol

well i do have an avo t3/t4 turbo sitting there waiting to go on. But i want to get a little more power. thats why i thought work the motor more. That way can run the boost at a lower PSI and get the same kind of power. But for when i wanna have some fun crank up the PSI and fry some tyres

cadud2000 wrote:well that sucks. I thought the piston stroke was the same. that sucks there is a 4mm difference. Why did subaru change the GT model from 2litre motor to a 2.5 in the newer models?

Was there a reason they changed? or just because they can?

So they can achieve the same power with crappy petrol (or gasoline as they call it) in the States....
Japan has 100 Octane fuel so the 2.0L engine works nicely for them

The 2.0L engines here have different maps to the JDM cars to cope with our petrol (lucky to be 98 octane IMO).

does that mean you could get the same octane results if you use premium 98 Octane and then add an octane booster into the fuel. would that increase the power much?

does octane booster fuel additive actually make a noticeable difference?

cadud2000 wrote:does that mean you could get the same octane results if you use premium 98 Octane and then add an octane booster into the fuel. would that increase the power much?

does octane booster fuel additive actually make a noticeable difference?

It would need an ECU remap to get the real benefit of running higher octane fuel

When the v5 STi WRX was released in Oz in 1999 it had JDM tuned ECU's and at that time the 'premium' here was only 95 octane, so many engines blew up and were rebuilt by Subaru. A remap of all the ecu's brought the japanese power of 206kw (some cars were more) down to 195kw.

Octane booster is more for protection to ensure that 'pinging' doesn't occur. If you put octane booster in a standard car it won't really be a noticeable difference but if you are ever suspect of fuel quality or can only get 95 (and need 98) it can be a good option.

My car has had an ECU tune, and whenever i track it i put octane booster in it just for protection when driving hard, but i wouldn't expect more power.