exvaux

iTrader: (1)

what kind of power/driveability difference will i find if i change from the 2.0 litre in my car to a 2.5 motor?A few folk said i will actually lose performance as the 2.5 is less revvy

911

Having spent the best part of 6 months quizzing that kind of question there are a zillion 'ifs-buts-maybe's' it the answer.

Pop over to 22B.com and go to Engine Mechanical section and read all the threads. You too can be as unsettled as me then!

Hot 2 liters are 'spikey' in their delivery
Stock 2.5 are lazy but will run 7K rpm max and full of smooth torque
Hot 2.5's are slick, will run 8K and deliver 500 x 500 of both, but the big current question is for how long.

dynamix

iTrader: (3)

with the 2.5 you dont 'need' to rev it so much - power/torque is available wherever and whenever you need it.

As an example, on a recent run on mine, there was roughly a 1 second difference between a 30 - 90 mph run through the gears and one held in 4th all the way.

Aztec Performance Ltd

iTrader: (234)

It might be best to take a ride in a 2.5 to help you decide.

After looking into it for some time I decided to stay with 2ltrs.

dazdavies

iTrader: (22)

I've just gone from 2.0L to 2.5

Now there are some major differences between the two specs in that the 2.0L was fully forged and fed by a maxed out VF28 mapped to 1.5 bar peak tailing to 1.3

The 2.5 is a stock bottom end but fed by a rotated GT30R
both specs had standard STI 5 valve train but slightly different exhaust systems.

For the time being I'm still on the 2.0L map but I'v upped the fuel pressure on the 740cc injectors that were present on both and boost is being kept to 1.2 bar.

Now even at 1.2 bar its way quicker than the 2.0L ever was. The low down response is incredible. Overtaking is effortless.

I know some people will say be careful because of the mapping situation but all temps are fine and the knock reading has never peaked as much as it did with the 2.0L

And all this nonsense about 2.5's not wanting to rev is utter gash.

I have a UK spec 2003 6 Speed box on my car which is a 99 uk classic so the ratios are quite short and as such seem to be in the top end of the revs when on a "sprited" drive.

The car revs as free as the 2.0L ever did but I have a wider more useable powerband. I cant wait until its mapped at 1.5bar flat!!

My advice is go for it. As mine is primarily a road car which will do the odd quarter mile and track day next year I'd say its almost the perfect package.

Daz

ex-webby

Best of luck running a GT30R at 1.5bar on a totally stock 2.5l bottom end.

dynamix

iTrader: (3)

was thinking the same.

What power/torque is it putting out?

dazdavies

iTrader: (22)

LOL at you sceptics.

Its more of an experiment this as I have a 2.0L CDB and some spare heads ready and waiting. My thinking behind this is if i have to shell out for new rods and pistons etc I may as well go for the proven 2.33 build and get the 2.0L sleeved etc.

Besides didnt John banks do exactly just that, run a stock 2.5 at 1.5 bar for over 12 months?

I know he had head gasket issues after the 12 months but that i can live with. Besides it does have 1.6mm head gaskets and ARP studs clamping it down.

I have no doubt that the stock bottom end is approaching its limits but.

I do all the work myself on my car so if it does go **** up i can fix it.

Only time will tell

dynamix

iTrader: (3)

I would love to do the same to be honest - it the other sceptics that get me

Presumeably this is well in excess of 400 of each ?

dazdavies

iTrader: (22)

To give it some kind of perspective with the VF28 on the standard sti Engine and top mount with 2.5 inch exhaust and standard rails and injectors(440cc) and standard reg with remapped ecutek it made 330bhp at scoobyclininc.


After my first 2.0L rebuild with 93mm (1mm oversize pistons), 740 cc injectors with parallel rails sx reg, powerFC, 3 inch exhaust and front mount IC still using the vf28 it made 360 bhp at 1.5 bar peak again this was done at Scooby clinic.


Now i'm still running the 2.0L map but have upped the fuel pressure slightly and boost is kept to 1.2 bar with the newly added AVCR it feels alot quicker than the 2.0L ever did.

Off the mark there's not much in it but unlike the VF28 the power doesn't tail off up the rev range.

I had a bit of a benchmark test along side a mates M3 the other day and I murdered it. Before anyone says he wasnt trying blah blah, he said hewas giving it all he had so I'm quite pleased with the pre map comparison because the difference between the two was significant to say the least.

I've no doubt alot of this is to do with the Rotated GT30R setup but in general before the turbo does come into play the off boost performance is good and initial response suprised me when i first drove it.


I have no doubt once its mapped it will definatly exceed 400 of each just by how much will only be found out once it gets mapped properly.

Daz

Jay m A

iTrader: (2)

John Banks was running a 20g at 1.5 bar wasn't he? Not a GT30R.

Not sure if you can flatline a 20g at 1.5bar on a 2.5....?

a 16g can't hold 1.2 past 6k

dazdavies

iTrader: (22)

Just found an old post by the man himself. Seems like I was wrong about the boost level and the mileage. It wasn't 12000 miles at 1.5 bar on the GT30R.

It was 15,000 miles at 1.6 bar

So I'm going to give it ago at 1.5 bar flat and see what happens.

Jay m A

iTrader: (2)

I stand corrected!

stevebt

iTrader: (8)

Mine is running a 2.5ltr closed deck block engine at the moment and a hybrid GT30r at 1.5bar and I have to admit its not what I would personally be aiming for. Mine is temporary due to problems so I can suffer it for now, But to live with permanetly! Its a little too slow for what a GT30r can do!!

dazdavies

iTrader: (22)

Which is why this is only a temporary measure until the spring where it gets bearings, rods, pistons and 1.8 bar flat

stevebt

iTrader: (8)

1.5bar is not far short of 500bhp with similar torque, so I don't think a standard block will last long

SSCJAY

Mine has just been mapped by JGM to 1.4bar, (to save the gearbox) but is more like 400 bhp no where near 500 bhp, I thought you pretty much have to be pushing 2.0 bar on the GT30R to get that sort of figure. I suppose it would also depend how much head work has been done, cams, lift etc etc

The difference from the 2.0 - 2.5 is just Fantastic though.

bighead

iTrader: (1)

I seconded that

dazdavies

iTrader: (22)

I'll 3rd it lol.

1.5 bar is no where near 500bhp. My GT30R has the .82 exhaust housing and I'll be around the 500bhp mark once it gets the forged internals and has 1.8 bar through it but certainly not at 1.5bar

If the block does let go in standard form as i said before i'll go the 2.33 route but for now i'm more than happy.

As the earlier post clearly shows John Banks ran his standard EJ257 i.e no forged bits at 1.6 bar for 15,000 miles. Then when he had problems it was head gasket issues nothing more serious.

I'm pretty sure at 1.5 bar carefully mapped it should be fine.

The proof is in the pudding as they say.

Daz

exvaux

iTrader: (1)

christ i only asked as it was the same basic price for a built 2.5 as a built 2.0 installed car will be running 440's and vf28 ie standard V5 stuff for a while at least.Will it be worth it with the standard bits or are 2.5 blocks more for bigger power rebuilds?

stevebt

iTrader: (8)

Mine is mapped to 1.5bar with a drop in engine on sti5 heads, and on Scooby clinics rollers it made 473bhp, its down in power as compared to my 2ltr AVCS engine but the lbs are way up 465lbs. Scoobyclinic have said my figures could be another 10% higher than what they have tested it too as they had to flatten the tyres that much to get the car to stay on the rollers !!!

SSCJAY

Are you running meth/water injection or something?,

I just pulled a built 2.5 (cracked liner) out of an STI8 with JDM big port AVCS heads running rotated GT30R @ 1.9Bar, and was told by tuner to be running circa 500 bhp.

dazdavies

iTrader: (22)

No wonder mine feels alot quicker than the 360bhp spec did then. lol

Roll on my 1.5bar flat remap
Same heads (STI5) more or less the same turbo plus its a stripped out 99 UK classic.

Happy days !!!! LOL

stevebt

iTrader: (8)

My map is on normal pump fuel !!