2.5ltr Engine Failures

[lunchie]

Just thought this could be a sticky or at least something easy to access as many people ask about how the 2.5 ltr compares to the 2ltr and there is much less knowledge in NZ about this where as the UK has a much larger information pool to draw on while having access to the same cars as us, thus making the comparisons relevant!

Below is the link to the main UK subaru forum and the on going 2.5ltr engine failures thread.

Makes for some very interesting reading.

http://bbs.scoobynet.com/scoobynet-general-1/828990-2008-2010-2-5ltr-engine-failures.html

The guts of it seems to be that should you intend to do significant power related mods then the 2.0 might be the safer bet unless you are willing to crack the 2.5ltr engine open and install stronger parts.

[lachlan]

Unfortunately, Subaru chose an unfortunate ECU tuning strategy in more recent years (mostly \'07 and newer) for Federal emissions compliance. Basically there is a long delay in the switchover from closed to open loop operation that forces the car to run very lean fueling even as load/boost rises. At that point, knocking/pinging/detonation is almost unavoidable and the resulting concussive pressure wave will crack the piston ring lands. In large part, this is what has caused some people to believe that the EJ motors are weak, but the underlying cause is actually in the ECU tuning.

Read more: http://www.importtuner.com/tech/impp_1103_subaru_ej_series_engine_tech/viewall.html#ixzz2Tp5C2Cj1

[Kiwi_Fozze]

Set c/l - o/l change over to 0, win.

The jdm 2.5\'s had a slightly faster change over, as they didn\'t have to comply with the same emissions tests iirc, and it can be easily tuned out

[lunchie]

can\'t just be as simply as a tuning issue at several tuning companies call a 2.0ltr engine reliable at 280kw atw but not so for the 2.5ltr. there must be some inherent weakness therefore that can\'t simply be tuned out.

[fbssub1]

 lunchie said:

can\'t just be as simply as a tuning issue at several tuning companies call a 2.0ltr engine reliable at 280kw atw but not so for the 2.5ltr. there must be some inherent weakness therefore that can\'t simply be tuned out.

ej20 and 25 are pretty much the same block, just sleeved differently for bore size, the 92mm sleeve has a greater cooling area around the bore so distortion between block and head under load is next to none, then you go to the 100mm bore, you are losing 4mm of cooling around the circumference of the sleeve compared to the 92mm sleeve so the temperatures will be a lot different as the water flow has been effected, so you will have higher temp at stage of contact with head and block and get more movement, hence why the 2.5 is prone to HG failure, the movement can be corrected by dowelling around the sleeve to minimise movement or too fully close deck the 2.5 and you will have the effect of zero movement in the sleeve. Not sure if this was what you where wanting, the failure of 2.5 under a high work load is not tuning it is poor design of the cooling system

[Joker]

all I know is there is a lot of 250T\'s with blown head gaskets (We are talking NA Legacy\'s here) not even making 200,000k\'s on the clock