In your opinion: do 2.5T's just "let go"?

[bigBADbenny]

As planned and promised: In your opinion: do 2.5T's just "let go", or are the various mitigation strategies effective?
Thread title subject to change, but please add your experience and opinion.

Personally, I'm on the fence, I think they may just crap out, but I also believe various strategies can help prolong the longevity of the 2.5T.

My favorites are upgrading the engine and tune with a focus on increased operational headroom (e.g. cooling, fuel delivery etc) , and plenty of scope to keep tabs on the state of tune (yes logging, afr gauge, boost gauge etc.).

In the end, if I'm making slightly less power, it doesn't really matter, especially if I can use more of what power is there, more of the time.
If it goes pop for whatever reason, at least I'll be able to take the responsibility, and I'll probably know what went wrong.

What do you think?

[dr20t]

EJ255 (2.5 in the liberty/ forester / wrx) = shithouse

Ej257 slightly better (lower comp, slightly better squish, better turbo etc) but still not 100%

EJ205 with intake avcs from audm 01-04 wrx are better than the above in my opinion

EJ207 jdm 2.0 litre is king (but I'm biased)

[Robbks]

EJ207 jdm 2.0 litre is king (but I'm biased)

except the pre-01 JDM EJ207 which is open-deck

[dr20t]

EJ207 jdm 2.0 litre is king (but I'm biased)

except the pre-01 JDM EJ207 which is open-deck

Agreed - although the heads are still better than any other non jdm market crap

[<GB>]

Ive seen engines blow not Subaru's but other types reasons, bad servicing mainly. one died when I reved it on the spot at work the guy had a front end damage and the sump had been removed...

[bigBADbenny]

So should this be a universal Subaru engine thread or specific to the 2.5T?

[Robbks]

Ive seen engines blow not Subaru's but other types reasons, bad servicing mainly. one died when I reved it on the spot at work the guy had a front end damage and the sump had been removed...

what..?

I also think due to a bad batch of blocks full of metal shavings and the broken oil pickup issues hasn't helped their reputation.
Then you add in every EJ25x since the dawn of time seems to be a lucky dip with head-gaskets.
whether that's due to the bad gaskets on the early NA motors, the open decked later model blocks or just an inherent design flaw somewhere.

You see a lot of early (pre 01) subies suffering blown HG's now, but usually caused by overheating from blocked heater cores/ radiators or split hoses. They hate to be overheated and can just about guarantee that a cooked one will need HG's.

[<GB>]

So should this be a universal Subaru engine thread or specific to the 2.5T?

I really don't get these threads ben, anything's possible, failure happens for many reasons. most engines don't just pop! example a tuner may tune 50 cars all the same to similar power levels, boost and ignition yet one fails so he's now to blame for a bad tune yet the engine bearings may have been put in rough on a Monday after a hard weekend on the piss and it failed before the normal designed failure point. ive seen many bad batches of fuel come through work and engines pinging off there head, once fixed you don't know what its like when you go buy it at a dealership with full service and 60ooo km! you might not have also known about that random hose that blew and they cooked it good and had it fixed and then sold it! after bad events like this you don't know how much the life span has reduced! why are some engines freaks and last ages

[dr20t]

So should this be a universal Subaru engine thread or specific to the 2.5T?

I really don't get these threads ben, anything's possible, failure happens for many reasons. most engines don't just pop! example a tuner may tune 50 cars all the same to similar power levels, boost and ignition yet one fails so he's now to blame for a bad tune yet the engine bearings may have been put in rough on a Monday after a hard weekend on the piss and it failed before the normal designed failure point. ive seen many bad batches of fuel come through work and engines pinging off there head, once fixed you don't know what its like when you go buy it at a dealership with full service and 60ooo km! you might not have also known about that random hose that blew and they cooked it good and had it fixed and then sold it! after bad events like this you don't know how much the life span has reduced! why are some engines freaks and last ages

Couldn't agree more

I remember discussing with Bruce when I was in Melbourne - it boils down to pot luck not just servicing and caring

Ten engines could all be serviced at the same interval and driven in exactly the same manner and have all different life expectancies and outcomes.

[bigBADbenny]

Brandon, you do get it, that's why you posted.
You're over qualified to post here.
I'm genuinely interested, being on the fence, and all that.

Anyway I'm hoping I got a freak... Oh and the Lib too

[Adrian2627]

The 2.5 was never really designed with performance in mind. Over here there have been very few performance 2.5s, only the 08 STi Imp and the 08 S402 and they were really road models. The real performance EJs have always been 2.0. The bore to stroke ratio just seems to work better, thicker cyl walls, etc all come togeather to create a better package. The 2.5 was just an answer to marketing calls from Aus and the US for more capacity = more torque = better engine Now with the FA the Japanese have gone back to 2.0 and added direct injection to increase the torque.

When you think about the numbers of EJ2.5s out there and how many Ks have been put on them there's really no issue. Under normal conditions, with regular maintenance, they are a good, everyday engine. Sure there's been some issues but in mass production there always will be due to the inherent nature in which they are built. I'm sure Subaru would love to build every engine like Nissan do with the GTR but it's just not feasible. We, as enthusiasts of Subaru's products pay attention to what goes on be it good and bad and like to think we can improve on that product. Unfortunately, we sometimes attempt to do things that are just not really in the scope of that products design brief but still expect factory longevity.

[bass_straitener]

The 2.5 was never really designed with performance in mind. Over here there have been very few performance 2.5s, only the 08 STi Imp and the 08 S402 and they were really road models. The real performance EJs have always been 2.0. The bore to stroke ratio just seems to work better, thicker cyl walls, etc all come togeather to create a better package. The 2.5 was just an answer to marketing calls from Aus and the US for more capacity = more torque = better engine Now with the FA the Japanese have gone back to 2.0 and added direct injection to increase the torque.

When you think about the numbers of EJ2.5s out there and how many Ks have been put on them there's really no issue. Under normal conditions, with regular maintenance, they are a good, everyday engine. Sure there's been some issues but in mass production there always will be due to the inherent nature in which they are built. I'm sure Subaru would love to build every engine like Nissan do with the GTR but it's just not feasible. We, as enthusiasts of Subaru's products pay attention to what goes on be it good and bad and like to think we can improve on that product. Unfortunately, we sometimes attempt to do things that are just not really in the scope of that products design brief but still expect factory longevity.

Very well said. I agree 100%.

[kiahatsiu]

One thing to consider is that a lot of modification, from basic tunes through to big heads and cam work aims to increase the top end power of a ej25x. Basic tunes often raise the rev limit (I am talking out my arse here Coyote and Kido, but I have a point I'll get to), and obviously big head and cam builds encourage revving. The thing is that the 257 isn't a 'rever' as alluded to by Adrian when mentioned the jap 2.0's. Big revs will kill stock, and underbuilt 25x's. Take Dr20t's current set up, he talks about it happily spinning to 10k, I don't doubt him. My built 257 will be limited to 7k, 7.5k tops, not because it won't be making power there, but because I underspeced the rods when the motor was built. Even then with bigger rods on board, it would still only spin to 8 8.5, which is still plenty I guess.
In short, I think a lot of the bearing problems in these things comes down to the marketing friendly 'torquey' rotating assembly. People what to rev them, they don't want to be revved.

[bigBADbenny]

Good point! Bring the knowledge, people! That's the point of "these threads". Consolidated information... Thanks!

[Adrian2627]

^^
That's exactly why turboing works well...to a point. For an NA engine to make power it requires revs to create the flow required. Forced induction is just that forcing the flow without the revs. An EJ25 will happily rev to 7000 but try to push it further and your are asking for problems. Why do we need revs in a turbo'd street car? We don't. With today's induction technology, turbos and injection, there really isn't a need for a big reving engine. In Mick's drag racing world revs and power are key, which is why he runs the EJ207 in the street world rather than trying to polish the turd to make it rev we need to be looking more at making it flow at lower revs. We are constantly chasing xxxkwatw figures rather than focusing on where we are producing torque. You can actually build a very good engine out of an EJ25 as long as you remain inside it's basic capabilities. Heat retention in manifolds and turbines, port matching exhausts, charge cooling, increasing the efficiency of our induction systems at lower revs will see the best gains in drivability on the street without pushing the engine out of it's comfort zone.