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Why all the negativity about the 2.5 engine


KV57
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Just a quick question, I have seen some info slating the EJ25 engines but after only having my forester for 4 days now I love its flexibility , do they really chew through ring lands as a standard car?

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From what I have heard from a few good sources :-) a lot of the info seems have come from the US more than in the UK, and they run on a lot lower quality fuel which with the standard tune from Subaru probably hasn't helped.... But hey what do I know :-)

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Unfortunatly the 2.5 stis do tend to go pop either head gasket or ringland failure like mine did :( .. I don't think the forester is as bad tho because they run lower power .. What model forester do you have ?

Look into getting an aos kit ( air oil separator) they're what a lot of people do to try and prolong the life of the standard engine

a well sorted 2.5 is a peach. the extra torque compared to the 2.0 is great :) although People over here tend to say even when built they're only really good for 500-600hp in the states there are two IAG built 2.5s running over 1000hp and loads of 700+ whp cars being daily driven so it can't be all that bad . Although in the us they've had the 2.5 since the blob eye shape so they do have slot more experience with tuning it compared to the uk we just tend to do a 2.35 conversion because it's try'd and tested ..

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17 hours ago, dgarside said:

From what I have heard from a few good sources :-) a lot of the info seems have come from the US more than in the UK, and they run on a lot lower quality fuel which with the standard tune from Subaru probably hasn't helped.... But hey what do I know :-)

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Happens just as frequently in the UK. Just tends to be a case of IM fob people off.

The 2.5 hasn't been changed much since it first came out, the engine is onto revision 4 or something like that now and the biggest change has been the ridges on the liners to hold them in place. Even the new one is suffering as well.

The standard 2.5 block is reliable up to a limit of about 450bhp due to the boost level required to achieve that, (the higher the boost the more power typicly, so limit the boost, limit the power). People do get away with going to 500 on the standard block, however its a chance and as many seem to fail as survive. The liners on the block arn't that thick, which is what's limiting the boost. Because of that they also have a nasty habit of lightly ovaling the bore when push up the power band, closed decking can help that and 550 is roughly a safe working guide.

Re-liner it and you can go alot higher, but there are costs involved in that and by the time you get to the stage a 2.35 is a strong and more cost effective option.

Also have to think about what the car is intended for, a race car engine for example is a very different kettle of fish to a road car engine. Race cars are hammered, running typically 75%+ of their time on full chat, generating massive heat and pressure. Hence why their cost is alot higher and they dont tend to last that many miles by comparison.

Depending on who you ask as to what's best will get you different answers, but alot of people in the know who have tried various different setups tend to agree the following as a rough guide for most drivable road used engine,

up to 450 then 2.5

up to 550 then closed decked 2.5

above 550 then 2.35

 

bearing in mind once you hit even 450 then you can rarley use it on the road to its full potential anuyway

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Thanks guys

I have a 2007 forester 2.5XT with a full subaru service history and I will be servicing it myself religiously with quality supplies , I have been looking at the grimspeed AOS.

In the future I will do a intake, downpipe and exhaust with a tune, maybe later going to bigger turbo, fuel pump and intercooler with mapping being done by alan jeffrey in Plymouth, so it looks like knock is the demon here, think I will ask alan to map it a bit safe , worth the loss in power for the added knock protection.

 

once again thanks for the info

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i just got rid of my 07 wrx hatch 2.5,head gasket failed.early engine are terrible 07 but i was told round 09 10 are much better,a 07 engine if you plan to boot it about then expect a bill at some point or get the engine built,or just drive it like a granny and it sould be ok,changing oil i would say dont really make a diffrence,i changed my oil every 5000 mile in the hatch used Shell full synthetic and genuine subaru filter and it did not stop it failing.at the end of the day any engine head gasket can fail,dont matter if its a 2.0 or a 2.5 if its going to go it will,you buy a second hand car,may have full service history but that dont tell you how its been driven,so you buy a car on your judgement and if it fails it fails its just 1 them things.even though the head gasket failed on my hatch i am still thinking of getting another 1 just a later model maybe a 09.

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Hate to say it but there doesn't seem to be any agreement as to what causes the failure, some standard well maintained cars go bang, some treated like crap don't.

Alot of whats said in the vid is just good practise for any turbo charged car and especially impreza so is solid advice, but wont change anything as far as ring land failure or HG failure goes. Only true fix is replace pistons, head studs and gaskets.

I suspect the only reason there seems to be less failure on later ones is cos there's less of them about, clinic's already had 3 2014/2015's in that have failed due to ring land so its still there as an issue and IM (subaru UK) still won admit there is any issue, despite loads of cars out there having a and in some cases several new engines within the warrenty period.

Oil change period gets talked about alot, how its driven makes a big difference to when, 5k for a normaly driven car or 3k for a weekend toy is prob about the right sort of level, weekend toys tend to be driven harder than daily drivers.

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1 minute ago, KV57 said:

so what we are saying is plan for a forged rebuild, was thinking of having a mahle forged later on anyway

If I was buying a 2.5 then i would pick it up and drop it straight off for a bottom end rebuild (rods, pistons, head studs and associated gaskets etc, heads shouldn't need dooing), but i can tell you three things,

1. its pot luck if yours goes or not

2. its cheaper to sort the engine before it goes than after its gone, when they go they can in the worst case write off the whole engine

3. a properly built forged 2.5 will run 450bhp reliably for many years

 

then if you rally wanna go the whole hog have it closed deck convert and go for 550, like i have haha

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i just got rid of my 07 wrx hatch 2.5,head gasket failed.early engine are terrible 07 but i was told round 09 10 are much better,a 07 engine if you plan to boot it about then expect a bill at some point or get the engine built,or just drive it like a granny and it sould be ok,changing oil i would say dont really make a diffrence,i changed my oil every 5000 mile in the hatch used shell full synthetic and genuine subaru filter and it did not stop it failing.at the end of the day any engine head gasket can fail,dont matter if its a 2.0 or a 2.5 if its going to go it will,you buy a second hand car,may have full service history but that dont tell you how its been driven,so you buy a car on your judgement and if it fails it fails its just 1 them things.even though the head gasket failed on my hatch i am still thinking of getting another 1 just a later model maybe a 09.
wrxs are a 2ltr [emoji85]

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1 hour ago, kershaw-330s said:

 

wrxs are a 2ltr emoji85.png

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you mean the hatchback wrx-s,i use to talk to a doctor near me when i had the wrx hatch,he has the wrx-s hatch 2.5,av not seen any 2.0 for sale only a r206 jdm import which is a 2.0,look on autotrader all wrx-s for sale are 2.5.

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I apologise I was always under the impression it was a 2ltr don't know why

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Wish it was [emoji22] but from looking at his wrx-s at side my wrx only difrences was the s gets sti rear spoiler 18 wheels and bit more power.part from that its just wrx with diffrent badge.

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