*smiles*

Wanted to hear both sides of the story of your experiences with a 2.5 short block.

What are your realities from people who have been there and got the t-shirt.

with power of hindsight anything you would do different

Cheers

Neilo

Overall i have been very happy with my experience of mine. It is a constantly evolving process though as althoguh it has been good, there is still so much that i would like to do with the car, but that is a problem with my mindset rather than the engine!

One thing that i did miss was the raw shove in the back that used to happen with the 2.0, this can obviously be overcome with a suitably large, laggier turbo though which i have to a certain degree now. It is very drivable though, plant your foot at 80 in 5th and off you go.

You are in a very good position of having a good set of heads to work with from your STi5, these are something that i am trying to source as apparently it makes what it already a very good engine in to an excellent engine.

Things that i would do differently? id probably go the relinered 2.2 cdb route if i could source one (although thats not easy and getting more difficult by the day i believe) to get a properly strong block to work with. The limitation of the regular 2.5s are the thin cylinder liners with can give out under higher sustained boost (over 1.6-1.7bar IIRC).

Mine has survived a few track sessions this year and coped very well in the company, performing better that some 2.0 cars due to better low down torque IMO, this was evident at SSO on the handling circuit i feel.

I think though that if you do go for a "built" 2.5 then you need to do it some form of justice by getting a suitably large turbo so that it doesnt run out of puff, i made the mistake of getting a turbo that i thought would be big enough...(a VF22 hybrid, supposedly good for 380~) and ended up wanting more very soon after as i knew the block was asking for it....a GT30 based or full rotated would make it an animal, but for drivability then a GT30 hybrid would be a good choice, its what i have now, and has a decent mix (not the best i might add) or response and top end....good enough for a daily driver at around the 400bhp/lbft mark at any rate...

hope that helps a bit

If you are down at triton for the karting then feel free to have a look round

PS. i should add, when i say "built" i mean forged pistons/rods/headstuds and maybe uprated crank bearings. If you get a bit lucky a built motor wont cost you that much more than a standard one which are, in general relatively weak and most dont advise running them above 350-360 for daily use.

*smiles*

Many thanks Neilo very good read

I am stuck in decision between the pro's and cons of both ways I plan to go, budget is the main limiting factor, but dont want to throw back as standard cheap as chips and end up doing it all again soon, false economy

My power aspirations do not exceed more than 350 more interested in torque and real world driveability, rather than chasing big figures high and bouncing of the redline. Its not a daily driver, have a 1.2 punto for that, more of a weekend toy

My decision I am stuck on the bootom end choice ... either a build on my 5 block and heads using STi 9 crank/ rods/ pistons (if I was looking for 400 figures would use eagle rods, mahle pistons etc) Or just drop a 2.5 out the wrapping in.

My thoughts are that for the cost of rebuilding with a STi 9 bottom end could have bought an allready built 2.5 short motor. I think my power aspirations would allow me to do this without needing to replace internals on the 2.5

2.5 or sti 9

Aztec Performance Ltd

iTrader: (234)

I assume your current engine has expired?

*smiles*

Well past expiry ... sounds like a diesel

Stripped it down and No3 Big End bearing has gone on holiday

Bores are worn too

Neilo

if it was me and it was a weekend toy (assuming a couple of track outings maybe) then i think i may be tempted to stay with the 2.0.....the cheap 2.5 (as far as i understand) wont take too much abuse whereas a nicely built 2.0 will....the only problem being that the built 2.0 will cost more....but roughly the same as a built 2.5....if you see where im coming from

dynamix

iTrader: (3)

2.5 is the way to go - the low down torque and drivability is perfect for daily driver and track use where you can safely be in a gear higher than you would in a 2.0 due to the fact you are using the power band. This is less stressful than trying to rev to 7500 to wring every last bit of power.

Neilo

unless you rev the 2.5 to 7500......

*smiles*

thanks for the responses so far, its good to hear a balanced view

I did find my 2.0 did use to scream in the higher gears and really was begging for mercy and for another gear on the motoway in 5th.

So If I am correct to summarise, the 2.0 will find more power higher up in the rev range and be safer if dribing style is going to drive it up there, but need to rev it to find its power. whereas the 2.5 will find its power/ torque lower down the rev range and not so revv happy, but more driveable power without having to wind it up like an elastic band .... correct

Much like comparing a two stroke twin 250 bike with a 4 stroke 600maybe

.... I used to have an RGV250, followed by a NSR 250rr sp, and it was gutless low down, but once you wound it up and it hit the high revs it used to be a nutter, was very highly strung, but get the gears wrong or drop out of the revs and you'd be whopped by a nova or moped

renno rannes

If you can stick to your target and not get carried away id go with the 2.5 for 350 350, Id add a set of decent pistons just incase but im sure it would handle that all day long. Would make for a very nice drive.

Renno

Neilo

That is it pretty much in a nutshell, however, the main difference that you will notice is that chances are your 2.0 was still having a fair bit of "go" come 7krpm with your current setup.

Unless you change the turbo for something larger then you will (as i found) change up by 5.5k as its game over power wise as a small turbo simply cant drive the extra capacity very well. I have some graphs at home that would show this.....basically it hits peak power/torque at around 5k and then dropped a good 125 of each by 7k, with a good set up the bhp line should still be climbing or at least only just levelled off at the redline IMO....and it is noticable as the car feels breathless at top. The turbo i had could barely hold 1 bar to 7k and as it was fairly small it wasnt generating much power anyway. My current turbo will hold 1.5bar to the redline (which is only set to 7100 anyway as it is a UK car and has crappy UK heads), which is much better

dynamix

iTrader: (3)

there is no need to - why drive where the power drops down? - stick it in another gear

I did a very respectable 1.45 min lap of cadwell in mine and never went above 6000 rpm.

Neilo

On your car maybe, i dont know what the spec is so cannot comment.

if you have a big enough turbo to feed the power then you can keep revving.....

If you have a smaller turbo with noticable drop off in power then i fully agree with you, as this was a situation i had as explained above.

dynamix

iTrader: (3)

simultaneous posts - spot on reasoning.

mine is a std VF43 turbo which actually peaks at 6000 but does drop noticeably beyond that hence wanting to change gear (plus also to protect the engine)

torque is the one big thing that you will get with the 2.5 - and that gives a much better drive

Neilo

ahh yes i remember now, you have an 06 STI right?

Has it been mapped or is it a stocker? i dont recall.

*smiles*

Cheers Everyone

Scoobynet Rocks with posts like this

...and not a troll in site ... did i speak too soon

dynamix

iTrader: (3)

06 STi yep - ran at 333bhp / 352 lb/ft

*smiles*

From another thread on the topic, is this a concern

Neilo

a good engine builder would have factored in the head reshaping i would have thought.

Gearbox, yeah....i suppose, your type R box will be slightly better than most 5 speeders, but it depends how its cared for and used. I abuse my UK box a fair bit and up until now its fine, with a wedge more than 350lbft, but i am saving for a PPG box for when this one does die....(if)

Agree with the last point. 300/300 isnt really stressing a good 2.0 at all so a 2.5 is overkill, after all, thats only PPP level for the last incarnation of the newer cars....

*smiles*

I guess if i do get a bit more power hungry then the 2.5 is a good platform for future proofing, just as long as dont get greedy. The torque and driveability in the 3-5k range are most important to me rather than driving it bouncing off 7k

Type-R

Running 350/ 350 in my Type R on 2.5 block (uprated internals)
Torque is very good and you can cruise around in 4th all day !

Running VF34 or 35 can't remember (8k with no trackday abuse)

I would agree with Neilo's comments on the fact that you will very soon be wanting more power as the block can handle it but can the gearbox !

As Long as it is correctly mapped - shouldn't have any probs...

P20SPD

iTrader: (1)

If thats what your after, then a 2.5 is what you need, just ask Alan Bell.

1.6bar midrange on a built 2.5.
300lbft at 3000rpm in 4th on rollers (6 speed box)
460lbft at 3500rpm
420lbft still available at 5250rpm

Now that really does hit you in the back!

*smiles*

p.s. whens that colour scanner going to be fixed

P20SPD

iTrader: (1)

**** knows

drb5

iTrader: (4)

I'm currently running up to and including 1.7bar, with Wiseco drop in pistons, Cometic head gaskets, ARP head studs, P1 ported cams, plenty other bits and a Superzilla 53, which is basically a TD06 with a 53lb wheel.

Not sure of power yet, but to keep it sensible, i'll say it's 420hp+ with similar torque.

I've not bothered uprating the rods(even though i had them in my posession), because i don't really rev my cars much.....my driving style. I like to put the foot down without changing gear and ride on the torque, something which the 2.5 is best for. At 70mph/3000 revs, you can put the foot down and the boost comes in instantly. On the day of mapping, we were getting full boost by 3100.

If your a racer/like to rev the engine and make it work, then stick with 2 litres or 2.2/2.33, but if your a ;azy driver like myself and use it PURELY as a nice road car, then a 2.5. Nothing to say you can't have both.....but it'll cost ya!

*smiles*

Great summary, that is a great help

*smiles*

my 04 WRX used to be a daily driver, but now we need two cars, we have a nice sensible 1.2 punto for that and fuel economy is great ... so we bought a classic STi wagon back as the weekend toy rather than a daily driver, so maybe for saturday/ sunday afternoon 'Spirited drive' through the B lanes is probably more suited to the 2.0 then, just make sure its built tough enough to cope with the revs - STi 9 bottom end and cranks, forged pistons maybe then.

Cheers again

drb5

iTrader: (4)

No worries. If you were closer, i'd have taken you out a spin, but i dare say your in England?

drb5

iTrader: (4)

In that case, i'd agree with the 2 litre part yes. I put the 2.5 into more a tourer area, unless you can build a bomb-proof block...

*smiles*

Yep, rainy England