RobEvo5

iTrader: (9)

Should be getting my car classic mapped soon. I should have plenty of scope with my turbo and fueling, but wondered what would be considered a sensible boost limit on a 2.5 ltr STI bottom end, and what sort of power people have seen at around 1.3bar pressure.

Basic spec is 20g turbo
740cc injectors,
2.5ltr STI bottom end,
Group N headers,
Full decat.

Neilo

1.3 is doable, i was advised to not go beyond 1.4 in the midrange and then taper off to 1.2 at the top. Im having stronger pistons and rods put in though so with some better head studs i shold have a little more flexibility on that.

But 1.3 would certainly see you fine

megrac

I've been runing 1.3bar for the last 13k km with no problems and have now started runing 1.4bar with the odd bit at 1.5 in the midrange since i've been using 10% methanol so i'll see how it goes. I can't do any more as my injectors only have a few % left like 2 or 3%.
My ej257 is totaly stock with ver3 sti heads.

andy97

iTrader: (1)

What level of torque from 1.3 bar are you achieving?


Andy

911

Thought about 1.5 max in the mid range with forged pistons iirc from what John Banks has 'researched' (the hard way).
What is the best injector size for a 400x400 2.5?

Graham

Jolly Green Monster

iTrader: (4)

Rob,

Do you not have uprated internals or am I remembering the wrong advert for the car etc?

Simon

RobEvo5

iTrader: (9)

Yes mate - Forged Pistons, Steel Crank, Forged Con Rods, and Strenghted Crank and Head Bolts. All done by scoobyclinic. But was playing on the safe side.

But if anyone has this spec I would be interested to know how far you have pushed things with boost.

megrac

Don't know but the factory ver3 sti gearbox is felling it but i know it likes it

Dataloglab says about 320-330ftlbs at the wheels and 340hp atw. And the g-tech pro says 343hp atw but thats at 1.35bar.

Mo

From the details you've given I wouldn't want to push it any further. If you are looking for more power than you have at present then you need to look at the whole package.

megrac

At lest if it breaks it might all break at once and for any more power i would need bigger injectors.

I've been the most imprest with the my99 sti clutch thats still hanging on, i'm using it as my fuse for the box.

Its not a 1/4mile car so it never sees a hard start just hard driving

andy97

iTrader: (1)

Ive been told that 550s will cope with 400*400

My car will have 550s

Andy

Neilo

i will be using 650s in my build, the 550s (assuming your talking about the sti pinks or denso, probably wont be enough in real terms.....

RobEvo5

iTrader: (9)

I will be using 740's as I have heard of 550's running 95% duty on 2ltr's running 1.5 on smaller turbo's.

2.5ltr with 20g has to be 740 IMHO the leave enough margin.

Neilo

i agree 740s would be a very good choice, i have got a set of 800s but they ere deemed too big anyway, ive kept the turbo relatively small so that i cant go over 400bhp anyway so 650s shoudl suffice!

RobEvo5

iTrader: (9)

Heres something really scary for you !!!. I will be running my spec and circa 400x400 but probably 370/350 as I think 400x400 is in perfect conditions with many an hour spent on a rolling road. On a standard UK 5 speed box with uprated clutch Thats is until it goes pop.!

But I too don't to quarter miles and always drive a car with mechanical sytmpathy. I still have fun but don't drop the clutch bang through gears or launch it from lights etc. So hopeing it will last a while but only time will tell. I would hope the clutch will fry before the gearbox.

I like the gear ratio from the UK 5 speed and not a fan of 6 speed boxes, as you are forever changing gears, which makes a car feel fast but on the road a long 2nd and 3rd is great for overtaking.etc

Neilo

me too rob, althoguh the only difference is i willprobably give it some on the track too see how far the box will go

RobEvo5

iTrader: (9)

map now done at 1.3bar. Thanks to Simon. - Cheers M8

! Wow what a difference. Its now fyling, and would like to dyno it, but afraid of what the results might show on paper V's what it feels like. It feels quick and pulls strong, but wouldn't like to say what a dyno run would show. I think I will sit happy at 1.3bar.

Jolly Green Monster

iTrader: (4)

No problem

alanbell

iTrader: (6)

Had sti pinks on my V7 but were maxed out now have p/e 650 ,

RobEvo5

iTrader: (9)

I can't recall how much i had left, but my 740's did have room left for more if one day I decide to push the recommended limits. .I think 540's would have run out. This is my daily driver and I am running on a UK box, and it was spinning all 4 wheels in 2nd last night, and starting to scrabble/spin all four in 3rd on the damp roads. And that was just due to torque/power. Not snatching a gear. (toyo T1X's). So probably wise to very happy with current results.

A 2.5 with 20g, headers etc, mapped to around 1.5bar must be a complete animal and a handfull to drive.

Jolly Green Monster

iTrader: (4)

Rob,

your 740s were in the 80% area iirc..

Simon

KEVWRX95

Rob
Like you, its difficult to estimate the power outputs for the 2.5 conversions, not many people have posted up RR results, and what mods they have done to support their engines.
Hopefully myself and others are going to the RR at Power engineering on the 25th of Feb, and I can find out finally what my car is kicking out.
Although there seems to be a lot of these conversions now, there are still many different versions of mods to support the 2.5, so unless someone posts up their spec and their results we can only guess.
I'm around the 1.4 bar area on the 2.5 with the standard internals from the scoobynet group buy a year and a half ago.After mapping and watching my knocklink (no activity at all) I can only assume my engines happy at 1.4 bar.
So I've done about 12.000 miles.
I will post my engine spec if you want it, to compare it to yours, then lets await the results in a couple of weeks.

Cheers fella
Kevin.

R19KET

But you've got a much bigger turbo Alan


The 2.5's prefer a bigger turbo, and depending on turbo choice, there's little difference in spool up.

When Alan's car was mapped, the mapper was lead to believe the turbo was a 20G, and because spool up was very similar, had no reason to question it, although he was surprised at how much more ignition the car took, compared to similar cars.

The turbo was actually a TD06-49, which spools up like a 20G, but the bigger TD06 exhaust wheel seems to improve the engines VE, allowing more ignition advance, and more power for the same boost.


Mark.

AlanG

That's interesting about the bigger exhaust wheel allowing greater efficiency and hence allowing more timing to be used Mark.

After the last mapping i had done last year, the thought occurred to me that maybe exhaust back pressure was becoming an issue, but finding out would have meant a fair bit of cost just to check, and i couldn't really justify it.

Do you have any experience Mark on using a GT35 exhaust wheel with a GT30R front end to see if there was any improvement?

AlanG

Going back to the original topic, i run a built block with uprated internals and have been running approximately 1.9/1.7 bar boost with a GT30R.


I ran a std Sti Ver4 gearbox with only a Quaife front diff in it. This lasted around 5000miles before shredding 3rd gear. Torque was circa 500Ib ft.
When the box went, it wasn't under any real torque or hard acceleration, it just happened, so be wary even if you don't abuse the box. I didn't abuse mine either cause i knew it wouldn't last. No untoward noises before it went, though obviously, repeated subjecture to the torque had obviously taken its toll IMO

dazdavies

iTrader: (22)

What rods and what pistons did you have in your 2.5? I'm assuming it is a 2.5. I am just trying to make my mind up whether to go for a 2.5 or rebuild my 2.0L.
I will be using one of RCMS GT35 Hybrids with P20 Running as much safe boost as i can and the odd 2.0 Bar run for quarters. I already have the six speed geabox on so thats not really an issue.

My choices are: use my existing uprated 2.0L (eagle rods, STI 9 Crank RCMS lead Copper barings)) with new forged pistons.

Or get a 2.5 short motor and use my eagle rods and get new some forged pistons for that.

Daz

TyPe~~R

I've just ordered an axis 2.5 with CP pistons, balanced and lighntend crank, better rod clearence, red lines at 8K, i'll be running 550's, 20G ported headers etc... Ill get it on the rollers asap then we should all have a rough idea whats what. the engine will boost to 24psi which i think is 1.65bar. seems quite high to me

Oldfella

iTrader: (3)

I can let you have three 2.5 CP pistons and one more that is 3 thou less after it "shrunk"

AlanG

Yes i run a 2.5 I use Omega pistons and Arrow rods.

R25 sti

i have a std 2.5ltr running 1.3 bar.md321 20g and 550,s.3" decat and equal length headers....398.4bhp/387ftlb...