hi guys i have recently bought a 330s bout 8 months ago, despite all the bad press on here and people on here saying im a fool and to save my money as you always get on here.. but i love the hatch shape and would even consider driving anotheer shape scoob, so that said.. im fortunate enough atm to be in the process of looking for a decent engine builder forge my engine,, the current bottom end is on 47k atm and never missed a beet pulls realy strong no smoke or anything like that,, i just want about 400-450 reliable hp obv with the chosen tuners suported upgrades and everyting too matchnot necesaraly going that much power strait away prob run standard turbo for a bit after the build,, just wondering how many miles will i get out of the forged engine?? the car will only realy be used on the road maybe with takday once a year, its just that if im going to spend the money on the engine build ii want it to last a decent amount of time as i still do a fare amount of miles in the car and i dont realy want to be taking the engine out every 2 years?? could i get 100k miles out of a forged engine same as a o.e spec should or is that just out the question ? ?
also seen quite a few american builds where they take the 2ltr crank put in the 2.5 use a longer rod and shalower piston and it creates a 2.35 in theory many people doing this over here if so howeffiective is it ??

thanks Alex

 

Some good questions there

So, I am no expert, but in my opinion you'll have hard time getting any assurance about longevity especially expressed in numbers, like 100k miles guaranteed...

That being said, my personal expectation is at least 60k miles, but this largely will depend on driving style/abuse, and not little buy how much heat will go on the engine(while pushed). A forged engine also runs bigger clearances - so warm-up is critical(cool down is also important ofc).

These are just the most important things i gathered, but there are more i am forgetting for sure now.

A bit of background: I have a 05 sti, which ran about 100k miles at about 330 bhp - never missed a beat. Wanting more, i am having it re-built at the moment for something exactly what you mentioned a de-stroked 2.5 to make a 2.35. How this will turn out to be, only future can tell, but i hope well. I do have to warn you, that doing it right, it is quite expensive.

 

The wear parts in a forged engine are the same as a stock engine, eg rings, bearings and oil pump in the bottom end and valves, followers, springs and cams in the heads. there is no reason why it should'nt last as long as a stock engine, in fact if you use acl race bearings +bigger oil pump it should last longer. As for bore clearance, for that power lever you can use pistons with a tight clearance i.e 1.5 thou as opposed to 3 tho. This is of course in relation to how hard it's used.
I don't really see why you would de-stroke a 2.5 as you will loose torque and gain nothing??????? they will rev better if you want to spend alot of time on the track I guess?
Let me know if you need anything building.
Andy

 

Hi Alex

I don't see any reason why a "forged" engine shouldn't last as long as any other. The only possible issue would be the frictional qualities of the piston to bore, and being carefully built with respectable oil changes would deal with that. If there is any kind of evidence to the contrary, it's only because people tend to want to run high power from these set ups, and unfortunately some of those people will be barking mad!
Under most circumstances a road car won't be pushed that hard, so the occasional use of maximum power won't wear it out as quickly as all that.
For those seeking very high power (over 500 bhp) we have been using the solid EJ22 block and going for a 2.35 stroker. At 450 bhp we'd say the EJ257 is just fine.
Personally, I like the latest Imprezas, being all grown up now, and very useable for everyday living. in fact I'd go so far as to thank Subaru for coming up with a range of cars to suit everybody. Classics, New Age, Hawks and Hatches. should be able to find what you like amongst that lot!
We'll happily quote you for a build, including whatever your heart desires..

 

Neil@Slowboy would be able to do it, he's down near Brands and he's built a few engines for people on here, including Jura. Once I've saved up, I'll be taking mine to him.

 

thank for the swift replys guys been realyy helpfull not doubt you will all be getting a call or an e.mail from me in the neear future

 

imho in my neck of the woods, more than 50% of built engines do not last more than 2yrs

Reasons

1. The owners push them harder than std engines.
2. Many owners do not have any mechanical sympathy, or limited knowledge
3. Owners fiddle.
4. You also get bad builds, by tuners/workshops. It is more important that you find a workshop that will stand by their work. But generally reputable builders charge more.

 

Also not uncommon for other bits to let go. People often forget that while part of the engine is forged and brand new many parts are still 60k miles old or not designed to run with the inevitable higher power.

 

Do uprated piston rings wear the bore out quicker?

 

alex ,on a 450 build the engine will only be the start of it mate,
the standard exhaust,headers,uppipe,turbo,injectors,clutch,brak es (pads ),ecu map,will all need sorting,i,d say you,d want to halve the oil change and brake fluid intervals (at least).
if used moderately hard wear and tear on tyres and brakes gets expensive on a daily driven car.
obviously not as bad if you can manage an oil change yourself mate

on the plus side well mapped cars with a modern billet turbo will give huge grunt with excellent driveabillity ,off boost they often get better mpg than standard cars.

personally i,d have no license left if i drove my scoob every day,if i drive it for few days(instead of sunday hoons)i end up pushing harder,reguarly have to ease off from xxx speeds,instant ban in the post sir.

you may as well be like the rest of us on here, no sense,no money left

 

alex ,some of the bigger tuners/engine builders will be able to give you drive in drive out prices to supply all of the above,probably quickest way if time is tight

 

I sent my 04 wrx to a guy in Yorkshire who forged it and rebuilt the entire engine for under 2k. I can't praise him enough. Inbox me if you'd like his number.

 

Iv done about 25-30k at 450bhp with my engine tuner 2.1 and still sounds like it did they day I built it so fingers crossed for another 30k

 

yes i am aware that i will need other supporting upgrades but most you have listed here you would upgrade anyway even just for maxing out thestandard engine,, but like i said surley if i was to do all of this and it was built by a repretable builder and a good safe map surly in theory it should be much tougher and last longer than the standard engine at 300bhp ??because if i was to spend 4k+ on a build for it to only last two years 20k miles i would be realy pissd surly an engine with stronger internals and better breathing apparatus should function just as reliably as a o.e style standard engine i do drive the car hard ocasionaly but isnt that what its made for and ive not had any probs with the std 2.5 as of yet so surly a goodd build would be tougher but also i want good responce and good everyday drivability ... Also what is the standard clutch on the hatch good for ??? thanks again alex

 

It's about getting it right. The factory product is theoretically built to last a certain distance. As the factory product is suspect in this case, (pistons and gaskets) fixing it can only be an improvement! I would not expect to be confronted with a major problem directly attributable to the engine itself within 100,000 miles.

 

The one thing you can not get away from is the fundamental design of the boxer engine. The one single weak point is the big end bearing width, this is 16mm, most petrol engines run much wider bearings (20mm+). No matter what you spend on rods, pistons etc, the bearings will only ever last for a certain amount of time/miles. The more power you run, the more pressure you put on them. You can help this by using harder bearings, bigger oil pumps (not too big though!) and good oil, changed more often.

 

On an average daily drive I could count on one hand the times that I could push the car,normally too much traffic about,some standard clutches seem to take the extra power and torque ,lot of it depends on your driving style really.personally never bothered with standard kit,the 2.5 will have a lot more low down grunt than the 2 litre engines though,
considering the engine will have to come out anyway may as well uprate whilst its apart,you need to remember your adding another 120 bhp and maybe 100 pounds of torque to the drive line Alex.
You,ll only kick yourself for not changing if it starts slipping a thousand miles later.
Will save a lot in labour costs as well mate considering engine will be on an engine stand in the workshop ,flywheel may need skimming or replacing at 47k as well.

 

To pick up on your original point mate ,a car that's driven sensibly will easily last as long as a standard engine,
Tbh you easily pop your original engine with lots of abuse either in lack of servicing or poor driving,forging just makes those individual components much stronger,remember your rebuilding the whole bottom end effectively starting from zero miles again with parts that can withstand the higher power from the start.

My point in my last post was that on the road you,all almost never be able to push the car to its limit .there's always another truck,another car,another van in the way lolol.
Just like the origional engine thats in it now its entirely how you drive day to day as to how long it,all last.


If you,ve got the money ,get it built and enjoy😁

 

Is it acceptable for a forged 2.5 to consume oil between services? I'm interested to know how forged engines compare to OE in terms of oil consumption.

My standard sti doesn't use any oil, I know Subaru will say that a certain amount of consumption is ok, can anyone confirm if this is also the case with forged engines?

I'm hoping the answer is that a properly built forged engine from a reputable builder will not consume oil.

 

i think the wider clearances during cold running do tend to increase oil consumption,just going from experiences from posters on snet.

my own 2 litre forged car definately needs topping up every few hundred miles,although i do use a 5w40 oil which probably does,nt help.
the oil temps i get circa 75-80 degrees dont warrant anything else imo

 

how much oil are you putting in at each top up?

 

You can't have the penny and the bun, more power/boost = stronger pistons required, the characeristics are they need to expand more and hence larger bore clearance. The extra boost will produce more crank case pressure, hence needing a better breather system.
The Mahle 4032 can be run with a tight clearance, but once you start going over 400bhp you need to have more clearance. You just can't have the best of both worlds with high power engines.

 

Fair enough that's really helped my understanding, as has this thread.

Thanks.

 

Remember it is the quality of the machine work as well as the build that counts.
People often focus on the build.

Anyway..

Oil useage is down to piston clearance and that depends on expansion rates of various pistons and how much or little they expand to the fill the bore.

I have had engines that have been rattly and drunk oil...but have made really good power and run as sweet as once warmed up.

I also vouch for Mahles. A forged engine I had fiited with them didnt use much at all.

Longevity for me is all about managing oil pressure and temperature in those first few minutes/and det once warm....not that it makes any difference in the long run for me as I am one of those barking mad people Alan J mentioned.

 

Mine runs standard breather system at The moment,only use the car at weekends now so check each time that I drive it ,probably use a litre between oil services (approx 3k miles).I would say hard cornering throws more oil about in the standard breather set up IMHO,
need to keep your eyes open for small issues that can turn into big expensive ones lol ie small oil leaks etc

 

thanks guys realy put my mind at rest about this, so like Allan j and steve have said theoretically with the right maintainance and a sensible approach to the whole thing i could happily run a forged 2.5 at 400+ bhp and it last potentialy 100k miles or more

 

Fair comments, although I'd never directly accuse you of madness!
Re machining/building, it's just one reason why I decided to do it all in house.
When we set up Syvecs and Alcatek ECUs, Martyn always puts in a warm up strategy that locks out abuse until the right temperature is achieved. It's compulsory!

 

I wish I wasnīt ..as things would be a whole lot cheaper.
(Behind the wheel I am a very careful, defensive, considered middle aged nutter)

The way I see it is the - bottleneck is not good builders, but good machine guys
There is a shortage of people able to do very good machine work. It is a problem as the few good guys are backed up. The main thing is that the cost of the machine tools needed for someone, with the right skill set, to set up a fresh outfit is prohibitive.

Having a warm up strategy on Syvecs and Alcatek is a real good way to approach it.

 

In theory yes
I would get oil pressure and temp guages in.
I pull the fuel pump fuse and crank to get oil pressure on cold start up.
(A bit extreme if it is a daily driver)
Run an ECU with knock detction/correction
Run a 2.5 Semi Closed Deck block with about 1.5bar boost pressure. Max
With reliabilty in mind look as a target figure of a comfortable 420hp Max
Warm it up and cool it down religiously
Have it build by a good builder, who has access to good machine work
Change the oil far more regularly than you should
Other safety stuff like baffled sumps, decent fuel pumps ect will also help.

But remember it is a tuned subaru engine. You canīt totaly have your cake and eat it

 

i've got a forged 2.5 hawk as my daily driver, 12k miles and going strong touch wood (pats head), using about 1/4L per 5k oil change, im running 390bhp/410ftlb. standard ecu struggles with the turbo momentum so idle is a bit of an issue, other than that its fine tootling or giving it the beans