Quite interesting, also noting Subaru changing the shape of the TMIC scoop over the various models.
AFAIK the hawk sti one is not as tall or 'aggressive' as the blob. I wonder if that has much of an effect on airflow.
Wind tunnel would be interesting! Although I guess the impreza isn't about top end as it is acceleration.

 

Just a question I have never seen the answer to..

What is the actual failure rate of the 2.5 engine,

how many have Subaru built and put into cars, how many STANDARD unmodified ones have then failed.

5% 10% 15% ??????

reading forums a newbie would presume 100%

someone must have looked at figures like this..

 

id be curious to see figures also.. particularly only hawk eye 2.5 failures as it seems more common in hatch and newer models.

not sure what the deal with scoop changes is/was. probably also to do with the front end shape of the car. the hawk looks visually more sleek at the front than blob or bug so maybe the taller scoop wasnt necessary as airflow remained attached moreso than on previous models?

 

Ah yes, the whole front end probably affects the flow to the scoop.

Re % of failures, I'm certain I've read a small figure of below 4 or 5 %. But that was on the 2.5 lump across the entire subaru family that used the engine, which is not abnormally high??. I think if you could get a number on just the WRX/STi failures it may well become more worrying.

I'll see if I can dig the tread up, it was somewhere after subaru released that bull**** technical bulletin saying all 2.5 drivers rag the crap out of their cars & dont maintain them.

 

DmcL, I'm intrigued with what you're testing, am always open to new ideas.
I'm currently running 396/420 through the standard internals on my hawk using the original, but ported VF43. It's running at 1.4bar so not overly stretching it but still making decent figures. Using a front mount also tho to keep the temps down.

The car has been like it since new about 700 miles on the clock, now has 23k and not missed a beat.

If I was to get another hawk tho I'd buy the older 2ltr or JDM 2ltr, just forget all about the whole 2.5 failures altogether!

 

even if only figures across all 2.5 variants were available it still sheds some insight into the problem.

i think i remember hearing one of the 2.5 non turbo models was quite bad for failing for some reason or another. also on models later than the hawk there was a run of cars that got a specific engine block casting which is/was prone to failure due to something in the manufacturing process, i remember reading one person had like 3 blocks with the same casting numbers let go on him one after another. some tuner or subaru shop started keeping tabs on all the block failures coming in and they all turned out to be this particular casting number also.. it was the 704 casting if memory serves ( http://forums.nasioc.com/forums/show....php?t=2424282 ) which were 08 or newer so our hawks are free of that issue at least.

also on the excess combustion chamber temps, i forgot something. apparently an AOS (air oil seperator, aka catch can) is a good idea as it removes the potential for any oil/residue making it into the inlet tract and coating the intercooler which can reduce cooling efficiency and lead to higher combustion chamber temps. that was from an article i read and recommended by crawford performance FWIW.

can the VF43's be had for reasonable money these days? also how would a43 compare to the likes of a TD05-16/18/20G if anyone knows? i have been looking at TD05's but if a VF43 is better for something in the 350-400hp region then i may start looking at them instead. also what about a TD06? lastly is the VF43 a straight bolt on for a TD04 WRX? actually just thinking.. i may start a new thread regarding turbo type/size as i have a new internally gated GT3582 sitting around that is/was for my bmw 325i which is currently in bits.. if its not too big or too much hassle to fit on an EJ then i could maybe use that?

 

As ive wrote on a million threads before, Im running 380bhp/412lb ft on standard internals, car has done close to 60k miles and has had most mods fitted since car was 2 years old.

Interesting to read about the TMIC and smaller scoop on the hawkeye, anyone know the reason why they changed the larger STi scoop on the blob to the smaller one on the hawkeye???

 

John ive told you before only muggles drive 2.5 sti

 

Thought you was popping round at 6pm??? Just put the kettle on for you, and instead your mugging me off online!!!

 

im a lot older than you, need afternoon sleep these days

 

Must be boring driving round in that JDM hawk, its sending you to sleep!! You need a 2.5 in ya life to keep you on your toes. Every creek/sound is potential headgasket failure, and will most days keep you up all night worrying!!

 

million and one now

id suspect its to do with the frontal aerodynamics of the car tbh. given that the hawk is the next gen id say there are aero improvements to the front end and for whatever reason the larger scoop was not required. or perhaps the larger variant of the blob scoop was more a cosmetic thing? saying that though id maybe think it was not required to be so large for aero reasons as the roof vane was also introduced on the hawk for improved aerodynamics at the rear of the car so subaru were definately playing with the aerodynamics to a certain extent when designing the hawk eye.

 

Have to agree with you john can't bet a good torquey 2.5 for a road car by the time a 2.0 has spooled up your already gone

 

John is more afraid of my 20v golf, passenger sickness issues

 

Are the blob and hawk intercoolers at different angles or sizes? That would make a difference in the shape.

as the front has got more pointy the intakes have gotten smaller. Look at current sti. As the above post says improvements in aero negate the need for more cooling

 

Would love to run the same sort of power you maz. Whats your engine spec and who did it, and if you dont mind me asking how much to do a engine build to run some decent power(pm me if prefer)??? and if I can remember is it a md321T your running???

But first I need a set of AP brakes before I start looking at 450-500bhp builds, got the car looking good at the moment, and the suspension is pretty much well set-up for road use, just need the brakes to complement the rest of the car!!

 

Damn right that 20v golf tried to kill us, nearly torque steered itself onto the otherside of the road!!!

 

STI = No.
WRX = Yes.

But both hawk WRX and STI use the same scoop.

 

Alan Jeffrey said the 2.5 is a good road engine on a thread that I started.He is a Subaru tuner and one of the best so this site would have me believe.This may not be as black and white as that but this is what he said.

 

Its the internet where all these story's come from not the people who actually work on them even if they are true.
And before you tell me that your mate bob works on Subaru engines and he said it is so he is just one guy and for the most part its internet.

 

There has been some standard 2.0 that have gone pop so the thread told me.The thread that I was told to go to so I got my facts right about the 2.5.

 

Yawn....if you drive a 2.5 and its dead on then be happy!! If you drive a 2.0 be happy. If either blows up be unhappy. Until such happens dont worry. Service history and background checks is king

 

The actual TMIC on the STi's is the same size, just different scoop shape/size, no? Not sure re WRX

 

Can we all just be in agreement that if you drive like a tool, something is gonna go pop?

You can still drive sensibly hard, can't you?

I mean I don't fly off from a standing start I love the 30mph + range and love the pull all the way to 70ish. That's where I find my car the most funin it's present state.

 

i have, well had a hawk up untill last week, guess what had happened to it before i bought it,,,,,,,,,,


ring land failure bog standard wrx.

if you bother to go ask some of the tuners you might find out the info. they dont all fo bang, but there are proportionaly a high number compared to other cars/engines.

Does make me larf how people new to scoob's start arguing the toss of people who have been around them for years lol

 

I may be way off the mark (due to my limited knowledge) but can fuel additives and better oils give these rings longevity? I am assuming the rings are the head gaskets bits?

 

Nope, the piston rings. Ring land failure tends to relate to the gap between piston rings, which has been known to crack from time to time. The best explanation I've seen for why this happens is probably the one DmcL posted earlier and assuming it's accurate then yes fuel additives/oils will help improve longevity.

 

Wouldn't worry about your brakes john to be honest ! I ran big ap,s on my classic and to be honest my hawkeye setup feels far superior ! I have just changed pads to (c/l ) Carbon Lorraine , bloody awesome , no brake fade at all. I sold my standard short block for 1k and purchased a used rebuilt block that had been sleeved and forged and stud conversion ! £1900 . I purchased that off a chap called Paul who is over your neck off the woods, he breaks classic , I only popped over there at the time to purchase my current turbo off him ( mdx321v) and mentioned wanting to forge my block but he had this one in from a customer who was breaking it ! Mark at tdr fitted my hawkeye block along with my standard heads ,cams etc ! The mapping was just open source !


Ian at Godspeed does the cl pads and I believe his kid Ben uses these on his track car ! Only thing about the pads is they squeal when slowing down at low speed .

Only running 1.7 bar to get the figures on this turbo which is probably about right I suppose and knowing marks Dyno ( really stingy) it probably really 800 bhp

 

If he's got the WRX subaru 4 pots then yes, will certainly need a brake upgrade. If it's an STI with brembos then should be ok.

 

I am new to this site but have had Subaru cars for 11 years.I was just making the point that MOST story's about engine failures come from the internet as you have just confirmed. I am sure a lot of tuners will say the hawk is s**t but its not where all the bad press comes from.