Lateral Performance

iTrader: (20)

If you're starting from scratch, a 2.2lt CDB to build a 2.35lt, really isn't much more expensive than a 2.5lt block.

Where it becomes more expensive, is most people building a 2.35lt are aiming for high power, and want to use better quality internals, which cost more than the normal "shelf" stock, and, or parts made in China.

For the road, and occasional drag/track day, a well built, & set up 2.5lt is hard to beat, and good value for money.

banny sti

iTrader: (68)

For a road car a 2.5 with an 321t+ with 480/480 is good vfm and pretty much unbeatable as a daily driver.

Banny

wrighty338

iTrader: (33)

i think its a toss up between 2.35 and 2.5 now then and start with a fresh block

will the 2.35 be more economical off boost? daft question i know but i wont be running a full on map for road use.

scoobyc

iTrader: (2)

great thread.

So does stock 2l STI heads / ancillaries fit the 2.5 block? Can you just buy a forged short motor 2.5l and use the rest of your original 2l engine with it? Or are other modifications required? Sorry if this is a dumb question..

Alan Jeffery

You can use any head combination as long as you ensure the comp ratio is correct by machining and/or use of correct thickness gaskets. Of course whatever head you choose has to match your inlet manifold.

DJ_Jon

iTrader: (7)

A 2.5 litre Impreza is never going to win the award for most economic car, however I still manage over 20 mpg on my 2.5 if I take it easy.

Scoobyc > depending on what version car you have, your heads will fit on a 2.5 litre block without the need to have any machining work done. Rest of your ancillories should also fit.

scoobyc

iTrader: (2)

Sweet. Thanks both

chrisdicko

iTrader: (21)

What happens to the standard 2.5 block? Does it melt round the forged pistons etc?

Sorry if that sounds stupid, but obviously people say they have limitations, but what happens when you go past the limit?
Has anyone destroyed their block on here? Not internals, but the actual block?

banny sti

iTrader: (68)

The liners are quite thin and have be known to split at high torque levels.

Banny

joz8968

iTrader: (13)

scoobyyc, Cometic and Cosworth do all-metal MLS HGs of varying thicknesses - so as to achieve the correct CR for your build, etc.

Therefore, hopefully, no machining would be required...

wrighty338

iTrader: (33)

so would a built 2.35 or 2.5 with some of them fancy AVCS heads and a really good turbo, light flywheel, light pulleys etc be good for scooby sprint type work?

i know neither are gonna be award winning economic cars but as said wont be running it at full whack all the time, il either keep my simtek with 4 maps or possibly solaris i arnt sure.

joz8968

iTrader: (13)

I would almost certainly reckon a 2.5 with AVCS - plus as low spooling turbo as possible for your power goals - would be spot on for sprinting. Mate that lump to the strong and low ratio'd 6-speed and you're laughing...

One awesome tractable machine.

Ian

iTrader: (10)

i wontfor a 2.1, as i felt it was the best spec i could get for the ££ (drive in drive out build)

my driving is day to day to the shops and back, and the odd 1/4 miles here and there for abit of fun at the pod. no track days

wrighty338

iTrader: (33)

plenty of 500+ turbos out there at the moment too. gonna keep the build simple as possible.

tempted to rotate the turbo + inlet also.

themoneypit

john i think its all down to how mo'honey you have. Start with how much money you want to spend. obviously you need to have the build match the performance level that you expect. However, you can easily spend into tens of thousands on the build. i know a lad that spent 20k+ on parts for his car. brilliant car which was featured in octobers jap mag but he was always moving the goal posts on his budget.

Tray

Shaun

If you want rev a 2.5 to 2ltr levels, I suspect you will need some proper heads and cams. I had mine bouncing off the rev limiter of 8200rpm the other weekend. Apparantly my valvetrain will cope with 9k+..... not that I would want to put that to the test!

Saying all this though, people have had very good results with the standard VVT heads. If I were to do it again, I doubt I would spend the cash I have on the Cossie heads I have, enough they are very very nice and would certainly come in to their own with a proper sized blower.

However... if I had a Newage JDM STi Engine, I would not bother with a 2.5. Just GT30, meth and NOS! Just under 500bhp and for not a lot of money.

Wrighty,
My 2.5, even in low boost and being the heaviest in the top 5, did the business at ScoobySprint. That was with a big AET GT30 on it, on two extremely tight tracks. You get it built right and these 2.5's have unmatched bollocks, driveability and power compared to most other builds of the same power rating imo.

Not all 2.5's and mapping are the same though..... especially ones that take the abuse, of which I only know of a couple that have not ended in tears, oil surge issues aside (as that is because of extremely hard use and not down to the engine build itself). For a starter these builds can blow headgaskets for a living, let alone cylinders letting go etc.

Find an engine builder with proven "track" or "hard" punishment results and do it properly. Way too many unproven "builds" out there if you ask me. Popping down the shops hardly constitutes a reliability test imo.

Not trying to **** you up, but this game is not cheap..... especially with an inherently flawed 2.5 design imo.

wrighty338

iTrader: (33)

Iv never set myself a budget, my build up to now, has cost however much its cost. and i originally only wanted a sti 6 kit with a fmic - now look where iv ended up.

i am only on a ****e wage so its just gonna take however long it takes but i do wana do it right, just a bit aprehensive about using a semi or ODB 2.5 - if im gonna do it i want it bombproof..so then i get thinking if id be better off with a 2.35 and a CDB. and it will be built by someone who knows what they are doin.

Thats why im trying to think it through proper before i go get a block + start!

Shaun

No such thing as bombproof imo! You need to be realistic.

wrighty338

iTrader: (33)

surly aslong as its not having its head kicked in 24/7 it will be alright, id never run a 500bhp map on the road anyhow..only off it.

dynamix

iTrader: (3)

Blimey... this is twice in a week that I am agreeing with you Shaun

There is always a weakpoint.

500 bhp for the track or competition means the car is going to get some significant stretching of component suitability if it is driven and set up right. The very nature of competition means that the envelope is always getting pushed. Mine suffered a fate in May at Knockhill, but that death started way before that with oil surge before a properly baffled sump was fitted and possibly other factors/issues before that. Even with a proper baffled sump (and the cosworth baffle plate !! ) but increased speed and cornering G.. oil surge started to show it's head again at Brands Hatch. Hence the move to dry sump now.

Maybe the same engine driven slower on track or driven purely on the road would have lasted but there is no point in that power on the road (IMO)

I am not one for revving the engine and most often set myself a 6500 rpm limit to try and preserve things but a high revving engine of any shape or form that is regularly visiting the rev limiter and using the available power is going to need more attention.

Having seen close up the attention to detail that Paul at Zen put in when rebuilding mine in a very limited time slot and despite working through the night on it twice - there were no shortcuts even at 4am! This painstaking (at times) detail pays dividends in helping to avoid as many issues as possible but competition is competition and engines, and all other components, get pushed.

Fit and Forget 500bhp - 500lb/ft engine's do not exist IMO. I am told it is like having a supermodel girlfriend...just a bit needy.

Shaun

Who knows..... you just need to be going in to this with your eyes wide open. It makes me cringe at times when it seems to be getting sold on the forums, that 500bhp is easy and 100% reliable now. It is neither. Things have come along way over the past 2-3yrs, with new parts available and differing methods, but 500bhp at out of a poxy 2-2.5ltr engine is a lot.

Long term reliability of nearly all builds is questionable at this level.... you run this kind of power for over 100k miles, with no issues and you are on the right track. A lot of us who have pushed certain envelopes are doing the testing..... that's the way it is. Count how many 500+ builds there are in the community and then find out which ones are actually being used with aggression. Numbers are way too small to convincingly come up with any answers.

Too many sales pitches and not enough experienced professional engineer advice imo. Building a 500bhp engine to produce those figures is the easy bit..... getting it to remain in one piece is something else!

Along with a small number of others, some of us have shown that the standard 2.5ltr case can take a fair amount of abuse. It was not that long ago that most stated the standard casing was gash!

My engine has been given much more abuse than most and apart from a headgasket issue after 9k miles (which we suspect was probably down to endless dyno time - many many 100's of runs - and a spate of constant 2.2bar and blasts at 2.5bar). Engine was stripped at my request and re-freshed for safety. Nothing was wrong with the engine apart from head gaskets and very slight wear on the mains (the block should of be line bored orginally). New rings, main and rod bearings, gaskets, line boring and bolts were done for safety. Car has now done just over 3k miles since the refresh and that has not been all shopping miles. This car get's used, proper! So... this casing, pistons, rods etc have lasted over 12k miles so far........ but 12k miles is NOTHING! It's lasted a hell of a lot longer than quite a few others have and maybe would under this type of treatment.

Another person who is proving good levels of reability is Duncan with his 2.5. Again.... this is from using the car for other things than going down the shops!

Regardless of how well my engine goes, I will totally strip and refresh when this latest build has done an additional 20k (if it gets that far lol). It is common sense imo.

I wouldn't ask us how much we have spent to get to even this "drop in the ocean" reliability. Remember the engine is ONLY PART of the complete build! You could spend nearly as much on ancillaries and labour to fit, on top.

I have the principal, that if it blows..... it blows. I hope it doesn't (and it shouldnt), but if it did, it would be another cheque book exercise and would not be a shocker to me.

You pays your cash and takes your chances!

m@t STImulation

iTrader: (3)

SC450 Tuning Package

The SC450 complete tuning package comes with 450BHP / 480 TORQUE!!! After 4years of us tuning the STi 2.5 semi closed deck block we can now offer this exclusive tuning package.

As featured on 'The Gaffers' 22B and our SC450 race car currently competing in the Time Attack Pro class series, hot on the heals of well funded big budget race cars with pro drivers.

Specification includes:
EJ257 STi 2.5 Litre bottom end
Custom Scoobyclinic Forged Pistons (with our own design piston crown)
Custom Scoobyclinic Conrods
Uprated ACL big end and main bearings
Modified Oil Pump
SC450 Turbo
Scoobyclinic Oil Cooler
Uprated Fuel Pump / Adjustable Regulator
Autronic ECU and Mapping / Adjustable Boost Controller

Includes Labour, All gaskets, fluids and oils + ECU and Mapping
Price: £9000

Recommended upgrades when fitting the SC450 Tuning Package:
PPG Straight Cut Gear Kit
Package Price: £2,995 fitted

Scoobyclinic 500 semi paddle fast road / track clutch
Package Price: £599 + fitting @ £150
S.C package sounds good to me, any thorts

SPECIAL OFFER DEAL PRICE: £12,000
Price Break Down:
SC450 Package - £9,000
Scoobyclinic 500 semi paddle fast road / track clutch - £649 fitted
PPG Straight Cut Gear Kit - £2,995 fitted
Total: £12,349.

wrighty338

iTrader: (33)

indeed shaun, i do agree, thoroughbred race machines need looking after

edit - i think it can be done for less then £12k

Shaun

Race or Road..... it's the same deal mate, just a different approach!

Like a Cossie Tuner once told me, before he emptied my wallet for a 500bhp RS500 engine.... "May the boost be with you!"

Warrantys normally finish after the first turn of the ignition system!

m@t STImulation

iTrader: (3)

whats the most power you can get for your money anser me that :-) dont say a standard car lol

dynamix

iTrader: (3)

certainly above 400bhp they are decreasing returns on the money spent.

Up to 400 (on an sti) - decat exhaust and remap gives the biggest bhp per £ beyond that you are chasing smaller and smaller amounts with bigger and bigger sums of money.

Shaun

Stage 1 is great value. If done properly, it will be as reliable as OE. As I said though, for cost vs performance on something like a 500bhp target. Assuming you have something like a Newage STi engine as a base:

Untouched Newage STi 2ltr with VVT Heads
FMIC
Inner wing kit
Good GT30 Hybrid, standard position
Injectors
Exhaust
Re-map on ECUTEK
FPR
Walbro pump
450+bhp on decent fuel

30 shot of NOS for circa 490bhp

It won't be as driveable as a 2.5, but you are not spending no where near as much. Just use the gearbox more! The OE Newage 2ltr STi engines seem fairly reliable SO FAR at this level. I know Rob North has ran this for 2yrs and never needs to open the bonnet between normal 5k oil change intervals...... but, a risk is always there!

Obviously if you are coming from a Classic engine, you may need to consider a built block and of course heads are not as good as the VVT ones.

IMO... never start a build without realising your budget... unless you have not got one! lol It's easier to say I have x to spend so what can I get, then saying I want y bhp for z use and then realise when something goes wrong, you are in the **** as you have no funds left!