you can always come out for a spin in mine on sunday if your there smiles.....if you wanted to get an idea.

Cheers, will see if I can make it :thumb:

Great thread, just like the '2.33' thread a few weeks ago.
Most interesting as I really want to do the 2.5 bomb-proof job using a 2 litre CDB I have.
Excellent.
:D
Graham

Can someone explain the bit about 2.5's not wanting to rev? :confused:

Your power/torque aims (for the expense) are pretty low imo.

If your engine is knackered, then you choose to either rebuild your own engine or you can buy a brand new never used, fresh as a daisy 2.5 block. Rebuilt engines may not be the best way to go..

I know my choice if i were in your shoes.

Alan, unless they have sti valvetrain/heads or fancy cams like yourself, then the "feeling" as you drive them, is that revving them makes sod all difference.

I would rev mine to 7300ish i think with UK heads and cams, but it never felt like it was gaining anything. Changing to ported UK Heads and STi 5 valvetrain, it would happily reav to 7800, and actually felt like it was doing something at that RPM too.

I'm more trying to get the idea of slower revving, rather than a lower rev limit.

When i was out in your car Alan, with the 30r, it felt as if it had all the revs in the world, yet still had the 8k limit(1000 more than myself). I think it's a feeling you get, but looking at the rev counter, i'd say it'll rev slower than the exact same car/mods, but on a 2 litre.

Surely if you had the exact same internals, but one a 2.5 and one a 2 litre, the 2 litre could have a higher rev limit than the 2.5?

If it's down to "feeling", then maybe it's because the 2.5 can give more torque and over a wider rev range which makes it feel unresponsive? i.e. a feeling of being more "naturally aspirated"? whereas a 2.0 lacks low down but once on boost "comes alive" and
therefore "responsive"?

It appears that people are getting the misconception that you want to steer clear from a 2.5 because it doesn't want to rev, but they do.
A std 2.5, you wouldn't want to rev over 7000rpm (on std internals), but you don't want to do that either on a UK spec 2.0, or even an Sti as such (even though it has an 8000rpm limit) because there's no point since peak power will occur before 7000rpm.

There's many options and ways to tune these engines, but i'm looking at what the originator of this thread is looking for in a rebuild and the use it will be put to.


Would you say mine is slow revving?...


I await quantification of this... what feeling is that you've had comparing how a 2.0 revs to a 2.5? Which one is faster?

It is nice to hear the silver saloon is hitting the magic 1.7 bar on a 2.5 again Dave :D Hopefully your build will make it hold, because that combo sure does feel nice.

I have 1.8 bar on a 4G63 and have to pretend it has real torque from its 2.0 litres :D although it does rev nicely to 7800 RPM. However, it is almost stock with exhaust, Walbro and DIY reflash. It does a pretty good impression of the 2.5 Scooby before it had the GT30R.

For me these days it is all about the hassles and costs involved, you can feel a bit trapped in a heavily modded car where the mods are worth more than the car.

Good observation John. Doing all this "extensive" modding can feel like a noose round your neck when you want to move on and do something different...

I was gonna be dropping you a wee PM soon anyways John, so i could pop over for a gander at the Evo, while you take a look at the silver Scoob. :D


I see what your saying Alan and i will admit your car is not slow at revving, but you have spent a lot of money on the engine, though not maybe as much as some think. With Coultys 2 litre/20g combo, the car breaks traction quite easily as it's so fast revving, but my car is more powerful overall.

It's like sitting in an aeroplane. Just because it feels so damn fast when taking off, doesn't mean it is. Always amazed me that one. :D

Then you can take into account using an STi block(standard) to plenty power, something which you just can't do on a standard 2.5, thus NEEDING upgrading.

Would you have used Eagle rods and Wiseco pistons in your 2.5? If so, then it's defo worth all considering it, but i doub't those parts could do the same as your Omega and Arrow parts. :p

That's why i said about there being many ways to tune these engines Dave and why i said i'm referring to what *smiles* was looking for in his new engine, be it a rebuilt 2.0 unit, or a new 2.5 block.

Which car do you think is going to hit the rev limiter in each gear quicker?

Good point Alan. :cool:

Sort of forgot that was posted by Smiles. :D

lol. We can all get carried away... :D Pity it costs a heck of a lot when you do!! :D :rolleyes:

Indeed it will be mine.

Think Dave's expression sums it up well.

While my 2.5 with UK setup would rev to 7300, it felt slow to get there from 6000 onwards

Compared to the sti setup, which whipped round like a barsteward.

"Its the speed at which they increase RPM's"

Oh i'm not so sure there. :D

I dare say we can all do an AndyF on a 2.5 no problems at all. :D

Funny how it works innit? :D ;)

That sounds more like there is something having a restriction if it's struggling to rev above 6000rpm, though i don't see much point if you're not making power beyond 6000.
Having said that, it's easy to rev to the redline in lower gears, more so on a UK 6 speed box.

as the originator of this thread will post up later as just off out, but this is a cracking thread and what ScoobyNet is all about :notworthy :notworthy

Steve :thumb:

I do feel there is a restriction and have always felt it is this exhaust, but Andy doesn't think so. However, i'm currently trying to get another system sorted out with a further tweak to the map and some more setup on the AVCR, it should be a bit better. :D

Still not decided about a gearbox either. The STi5/6 is ok, but needing a "proper" refurb and i'm considering going the 6 speed route, as i use the car so much and have always fancied the 6th gear.

Just to add some good Scottish whiskey to the fire, i'm still waiting on someone coming up with some details on the new Impreza 2.5 heads. :cool:

But thats it Alan, STANDARD uk heads and cams cause the restriction IMO.

Porting the heads on mine, and replacing the valves and cams with STi5 stuff, removed the restriction IMO

In other words the car went from - Not wanting to rev - TO - Wanting to rev

Have you driven a 2.5 with STANDARD uk head setup?

With the kind of power you have now Dave, i wouldn't run it on the 6 speed the previous owner used, choose a different set-up/combination.

He looked like the Tazmanian devil flapping his arms about changing gears so quickly for the first few seconds before he could start to think and drive the car the way it should have been driven... :D

Lol, i know. IIRC that was a STi Type-UK 6 speeder?

I remember Paul saying the Hawkeye 6 speeders are much better ratio'd?

Same here. Makes sense if you think about using cams and cylinder head designed for a 2.0 to use in a 2.5, but we're talking about a car which the owner is more interested in midrange torque than a balls out 8000rpm racer...... you've already said it revs fine to 6000rpm, so what does it matter it doesn't "want" to rev beyond 6000rpm....

Haven't driven a UK 2.0 head/cam 2.5, only a Ver2 WRX head/cam 2.5

Think his was the UK 6 speeder?

True, if its midrange, then yes. Sorry, it took me a while to catch up with what you were getting at.

Hi

My 2.5 is using UK heads (ported). Comparing it to my car before the change (i.e. 2.0) the revs seem to pick up quite quickly but then I've never driven (sat in one - never driven) an STI so I can't compare the feel (find I need to drive a car before I can really comment). I have to say the torque is brilliant. 4th gear from 60 to 125 with no effort at all. I do find I change before 6000 rpm, but this may be more to do with the screamer pipe (due to be plumbed back into the exhaust shortly).

Basics of the car

2.5, Ported UK heads and Wieseco pistons
GT30R
APS exhaust
GruppeS style headers
Mapped for Shell ???? (dont know as it was during the change over from Optimax)

Based on my experience so far, I would definitely recommend the 2.5 route to anyone thinking of doing it. My view is that, with the current crop of Subies being 2.5, any perceived revving issues will be resolved as people push the envelope further. After all... with the shortage of 2.2 CDB's, Andy will have to change his engine at some point.:)

Cheers

As far as i know the UK 6 speeds have longer ratio's than their JDM brothers, but the newer versions are better suited?

Maybe Paul can confirm this?