RON

I currently have a my00 with ful decat, and fairly basic mods, I am desperately trying to find a reason NOT to go for a 2.5 block swap, can anyone please advise as to why it would seem that the uk my00 heads are no use on a 2.5 bottom end?? I'm not after mega power, otherwise i'd have done more mods to the 2.0. just after something a bit different really, what clutch do people tend to use with the 2.5's??
Also, obviously on the my00 i have a td04 turbo, I know thats a bit small for the 2.5, but is it useable at-all?? or is it gonna run out of puff too soon??
I'd rather not have a laggy engine, but at the same time i don't really want to end up trashing my 5spd gearbox after ten minutes, I'm fairly gentle on the drivetrain even as it is now, so unless i end up with mega torque, i don't see too much of an issue there, (hopefully!!)

All advice will be greatly appreciated, and i also realsie that all the info i've asked about is probably on Snet somewhere, but with all the threads flaoting around it'd take me a year to find all the right answers.

Cheers.

Ron.

Big Bear

You have answered your own question , you will end up trashing your gearbox . It is not the power that does it , it is the torque and the 2.5 will produce plenty of it . I managed to trash my gearbox with a TD05 running 0.75bar during the first 1200 miles (not taking it over 3500rpm) .
After replacing the gearbox and finishing the run in , the TD05 ran out of puff after 5800rpm at 1.1 bar mainly due to the restrictivness of the turbo exhaust housing.

megrac

Is my sti3 gearbox really that much stronger than a my99 wrx box? as i can get away with 1.3bar and quick changes easly with my 2.5 and have done so for nealy 5k.
The td05 would make a bit more torque down low than my td06 but by the sounds of this week gearbox broblem i should've broken it long ago.
I did have a td05 on it for a bit and the laglessness was sooo good.
I just NEVER drop that clutch and i don't give two hoots for a 1/4mile.

Nezz10

There are a few people that that have used a UK 5 speed with a 2.5 and are still running but there is also a few that have stripped gears with it. The Sti boxes are stonger I have been led to believe.

If 2.0 UK spec cars can run at 350+ bhp/torque then there is no reason why a 2.5 should strip gears instantly when running the same figures IMO

P20SPD

iTrader: (1)

IMO it all depends on how you drive.

My MY00 Uk box went on my 2.0l with just 30000 miles on, and just 320lbft ish, but then i do drive fairly hard by all accounts (make use of what the car has).

My 6 speed withstood several 7500rpm launches with my 2.5 with a GT30R on board. No way on earth would the MY00 box have stood up to that.

P20SPD

iTrader: (1)

IMO its also not just the max torque it suffers, its where that torque hits the drivetrain, and for how long.

A 2.0l will hit it later in the rev range, where as you would expect a 2.5 to hit lower and for a longer period, thus putting more strain on the drivetrain IMO.

RON

Oh well..... looks like it's started..... i've just bought j Bank's old 2.5..... with tdo 5/20g and sti box!!

stevebt

iTrader: (8)

sti box wont last long on 2.5ltr and 20g turbo, ill give it a week if that

john banks

AlanG, Bob, Harvey, AndyF, KevP1 and others have all put considerable torque through these boxes though. Andy did 0-100 in about 7.6 with his with a 2.33 on GT30R. Don't think I'd run it with a GT30R for a long time though.

stevebt

iTrader: (8)

my box lasted fine until i gave my mechanic a go of my car it was broke that day 6 speed fitted im trying to resist urge for larger engine and turbo

Houghton

iTrader: (1)

I've done 17K miles on STi3 box with 2.5L & 20g turbo, 350/350. Varied driving, some poodling, some track days.

saying that's asking for trouble

Hoppy

Ron, if you want big power, then it's better to stick with 2.0. More research needs to be done on the 2.5 which seems to eat pistons over 400bhp. And if you're going that high, you'll be putting 380lbs/ft or more through the gearbox. The 5-speeder won't take that for long. And having spoken to Prodrive about gearboxes, they are not aware of any 5-speed box being fundamentally stronger, eg it's a myth that P1 boxes are tougher.

But if you want smooth and readily accessible power at sensible revs, then the bigger engine makes sense. I chose 320lbsft/350bhp as the maximum for my 2.5 classic as that is where I believe the limit is for the box. If it blows, it blows - not massive expense for a used replacement from somewhere like API.

This is also close to the limit for the OEM 440 injectors, OEM induction with STi panel filter, and my big top-mount IC. So in the interests of economy (daft word to use in this context ) and simplicity, the power targets were set for me and I then chose a turbo to match, ie TD05-16g. I fitted Gruppe-S headers because the Group Buy was a snip, but I was going to give it a run using ported OEM headers, although that would probably have been a bottle neck at the top end.

And it turns out, according to Bob Rawle's butt-dyno and educated guesswork, which is probably more accurate than most rolling roads I've got around 310lbsft of gearbox-friendly torque and maybe 340bhp

It's a hoot to drive (come over and have a go ) and I think this is the sensible limit before the law of diminishing returns really starts to kick in, in terms of cost and also driveability. If you're a dyno queen or drag the car then my 2.5 is not for you, but if you want a reliable daily driver that's easy going and great fun, as opposed to a costly and demanding lag-monster, you're on the right road

Oh, and you'll have heard about 'project creep'. Well, in terms of budget mine came in under my original estimates, mainly because of the good dollar exchange rate, but in terms of time I'm miles out. This plan has taken 18 months and should have been finished last summer Nobody's fault, but it's quite an undertaking and there are always unexpected delays.

Good luck,

Richard.

PS Ditch that big turbine on your TD05, or it will end in tears...

PPS Edited to add, there's nothing wrong with the UK heads, although I think STi cams will flow better at the top end. And the TD04 will be fantastic... up to about 4,000rpm It needs to go, but the 2.5 flows so well that my TD05 spools as quickly as the TD04 did on the 2.0.

RON

Cheers Hoppy, I'll stick with the package that i'm getting, I have no desire for huge numbers, and if i can get the drivability at lower boost then that'll be a bonus, I too am quite keen to stay on the oem injectors, and if possible the airbox, might even try my home ported headers...I'd like the underbonnet to look as near to standard as possible really, I'm not bothered about the 'gloss appeal' I just want a fast reliable car thats fun to drive, and a bit lazy with the revs.....

Roughly where in the country are you?? i may take you up on the offer of a ride...!! pm me if you don't wanna tell the world!!

Cheers.

Ron.

Hoppy

Ron, if you're into a bit of DIY porting, check out Floyd's car in Projects - lots of pics.

Sorry, I'm a way from you - Midlands.

Just been checking some stats and in theory my car has about 267bhp per ton. That compares to 216 for an M3, and 246 for the new 911 Carrera S everyone raves about. Not far up the road is the 911 Turbo with 272 and 292 for a 360 Modena if you can wait for 8,500rpm to arrive. Bet it sounds fab, though

I'm not trying to diss any of those brilliant and ultra desirable cars (well, maybe not the M3 ) but how much power do you want? If I drive my car at WOT for more than 5 seconds, it's already going seriously fast and I'm probably heading for a hedge

Richard.

RON

I've already done the headers....not sure it made a huge differnce really...... but I have a H&S up-pipe aswell.. d'you think that'll work with the tdo5??

john banks

2.5 will spool up a much larger turbo very nicely, and the effect that has of uncorking the exhaust and making power from 3300 RPM when it hits full boost to 7500 RPM whilst it still holds it and breathes well smashing into the rev limiter if you are not quick is astonishing, even at modest boost. Now I've learned to tune it with an appropriately sized turbo, high 400s BHP doesn't seem to be stressing it. Octane seems to be the limit rather than the structure of the engine.

I cannot believe how tractable a rotated GT30R is on a 2.5 and what an evil noise it makes whilst it pushes very hard and effortlessly. It does *DEMAND* work on the brakes and suspension well beyond a UK turbo though, a 20G/2.5 running on Eibachs and OEM MY00 UK dampers felt like a speedboat.

RON

I'm sure you're stalking me john......

john banks

No I just live in the Drivetrain forum

Houghton

iTrader: (1)

John, Is 7,500 a safe limit for a 2.5 with std internals? I have had my limit set to 7,000 since day 1 but its well run in by now. Having said that, there's no need to go into the upper rev range and it only happens on the odd occassion as my reactions are slowing

john banks

Quirt Crawford says 8000 RPM is safe on std internals, but I don't feel brave to try it... I have revved it to 7800 RPM before and it seemed OK if a little pointless with a smaller turbo. It doesn't rev as smoothly as a nice EJ207 though. The pistons are not very heavy, the rods are quite strong, gudgeon pins are quite heavy though.

Dyney

Ron,
You should have said at the weekend!!! I'd have taken you for a quick spin

I'm still on the std UK 5 speed after 10k miles. The box has done a total of 120k
It's very notchy on gear change but has been like that since before the 2.5 went in

I have the rev limit set to 7k and pushing 1.2-1.3 BAR on a TD05-20g based turbo and it's stupidly quick!! 376bhp / 372lbft

As said above the 2.5 alows a bigger turbo to spool up like a small turbo does on a 2.0 due to the extra exhaust flow.

If you want a quick road car that is easy to drive you can't go wrong with a 2.5
If your on a budget but want to upgrade parts at a later date it's perfect.


Here ends the advert for the 2.5 block

RON

NO problem Ian, i fear that tasting the fruit might make me want it in the car sooner...... although i'm getting impatient already, and i haven't even got the block yet!!!!!

Cheers.

911

I'm going to STOP reading all this 2.5 stuff.
That account by John just above on the engine is the perfect hill climb engine.
Just cannot stand the thought of another £x K on this car.

Graham

RON

But Graham..... if you're anything like me.... you KNOW that the temptation will become too much to bear...... and you WIL end up doing it!!! probably before i get mine done too!!

911

The wife will give me clear guidance when the time comes...