madou

Following the 2.5L project you can embark on the active differential project

Andy.F

Conrad, the point you are missing is that a 400/400 2.5 car is actually more enjoyable to drive than a 550+ car (IMO) There is also no way a 550bhp turbocharged 2.3/2.5 is going to be a low maintanance car if used as everyday transport.

Andy

Andy.F

My only reservation with the 2.5CDB is the linering. It may be absolutely fine but IMO it still needs to be proven over a decent mileage/number of heat cycles. These blocks are pretty frail for this output and anything that may (or may not) upset the crank alignment or block rigidity is still a bit of an unknown.
If your 2.5 proves reliable then the extra CC's are worth having.

I think with your cams etc the GT30R will make an excellent car, throttle response should be fantastic.

Regards the 0.7 v 0.6 A/R compressor housing, I understand what the figures mean regarding size but confess to not knowing how this will effect spool up (if indeed it does) I can see how the maximum flow limit may be greater with the larger A/R and would prefer the larger option on a 2.5 as it requires a higher volume flow rate (read discharge velocity) for the same PR as a 2.0 for example.

Andy

The Fixer

Andy I dont disagree with you, it just seems a step backwards for all the effort that went in, not in terms of drivabillity for road use but for the whole point of the project. With a little more thought early on with regard to goals and what was required as an end product then considerable amounts of money could have been saved along the way. We both know a 400 / 400 car is alot easier (read that as cheaper) to create than a fire breathing 550 HP one. Each to there own I guess

Wonder Wagon

But if Adam was to turn the power down, won't it make it more reliable???

Adam M

yes it would, but if I turn the power down, the bigger turbo is only being tickled.

I came to the conclusion that if I turn the power down I might as well switch to a turbo that has a lower threshold.

the gt30r should still push 500bhp if I want it. 500bhp is never going to feel slow.

I agree with conrad on the money thing, and yes it would have been a lot cheaper to aim lower in the first place, that said the 2.33 route is hardly any cheaper, and the ej257 has not proven reliable yet for the boost output needed to get 450bhp, and more importantly 450 lbft.

I havent actually sold the second gt35r turbo yet (money not changed hands that is) and the car will have been mapped and easily swappable between turbos.

worst case scenario I could switch between them for fun when I feel like it.

Although my car doesnt have to be an everyday and is rarely used as such, reducing the loads on the bearings means it stands a chance of lasting a little longer for not a lot of sacrifice. Hindsight is a wonderful, but now that I have driven 550lbft and bhp on the road, I know for sure I don't need it, I also know for sure that 450 of each with 2 bar of boost available around 3k rpm will make for an untouchable road car.

Anyone hazard a guess as to the 0-100 time will being quicker or slower?

carlos_hiraoka

Why do the US guys, which are also using a lot of boost and big Garrett turbos, are not getting headgasket failure, but piston failure (which is understandable).

http://forums.nasioc.com/forums/showthread.php?t=696933

The only difference is that this guys seem to use the > MY02 engine heads.

Carlos H.

john banks

Carlos, perhaps they are not pushing their turbos too hard for their spec, whereas mine probably end up with quite a lot of exhaust back pressure as I want both spool up and power. Although that doesn't explain Steven's failure running 1.6 bar on a GT30R. Also US vs UK horses? They often quote WHP figures for a given setup that I would think of for BHP over here!

The Fixer

And dont forget there heads are the 2.5 litre version newage heads which could also be a factor.

Adam M

not sure about the heads being a factor.
If that were the case then why wouldnt the same base heads be causing a problem on my 2.5 or the 2.33s?

I know the shape of combustion change will change the pressure distribution inside it at different points during the stroke, but in the absence of det (which doesnt seem to have been a factor with the failures) then the pressures shouldn't be any concern to the gaskets being used.

Aside rom that the mating surfaces clamping the gaskets down are the same size, I just don't get what is so different about the faces of that block and head that would cause these problems.

Could it just be that these are particularly unlucky yet high profile cars?

P20SPD

iTrader: (1)

Adam, are your heads matched to the bore though? ie received a lot of custom headwork?

tweenierob

Should have my heads off soon, after this months Santa Pod.. I matched my combustion chambers as close to the bore as i could and will take some pics.

BIt of a primitive way of doing them but it appears to have worked, i have only clocked over 4kmiles now but the car only gets driven hard. I suppose it isnt enough milage compared to P20SPD 'drive it like you stole it' .

Anyone else pushing phase one heads on the 257?

Rob

The Fixer

Exactly Steven! I'm sure DWW will have matched the heads to the bores on Adams engine, I know we did on mine (but where yet to see how that works)

P20SPD

iTrader: (1)

Rob , you're only halfway to the danger zone (was that a lyric from a song??)

Conrad, i wonder if Adam has forgotten this. Certainly when i compared my MY00 standard heads to Wallis' fancy heads, the difference was incredible.

Jolly Green Monster

iTrader: (4)

are they coming off due to head gasket problems too??

tweenierob

No mate, piston/compression change and then i will be cooking with gas

Rob

Jolly Green Monster

iTrader: (4)

from Top Gun iirc..

no idea who sang it though.. lol

Adam M

think it was highway to the danger zone.

steven,

smg did my heads and they are definitely matched to the cylinder bores.

P20SPD

iTrader: (1)

LOL

Adam, so does that perhaps answer your question re your 2.5 and the 2.3's ?

Adam M

Its a theory, not sure its an answer.

the problem with combustion space shaping is that exposed ridges from non matching head and bore profiles leads to hot spots which create det. that is great if head gaskets are showing signs of failure due to det and ecus and knocklinks are showing det to be a factor. That is not the same as head gaskets failing simply ue to excessive pressure as I dont see how mismatched head design will mean increased overall pressure.

carlos_hiraoka

Adam, how many miles has your engine done ?

It is true that US dynos read different that UK dynos, but some of the guys over there are using over 2 bar of boost with GT30 and GT35 units on their 2.5L STi's ..... and go out for drag racing frequently, the main differences I have spoted is that they use:

1) race gas
2) US STi, new age JDM or new age engine heads
3) they seem to suffer from piston failure

BUT it is very unlikely to read about headgasket problems with US STi's ..... and now they have been out for a while, with some of the already running into the low 11s with stock EJ257 shortblocks.

Carlos H.

The Fixer

If you think about the bore size on a 2 litre block, then the position of the fire ring on the headgasket and where it mates to the outside of the combustion chamber on the correctly matched heads. When you then fit a wider bore 2.5 litre with wider headgasket, this then mates correctly to the block in terms of position but when heads are then put on that were from 2 litre bore where does the fire ring of the headgasket sit in relation to the combustion chamber on the head???? Certainly not where it should be.

Nology

A little side track.... if you have a choice, would you go for a 8:1 CR or 8.8:1 CR with the 2.5?
Available Petrol RON is 98. Intend to run a 20G on this.

carlos_hiraoka

8:1 CR

Andy.F

8.8:1 CR

ASTiMAN

My engine spec in my Type R V5 is as follows:

2.33 litre built from EJ20 closed deck block - re-linered and bored to 97mm, stroked to 79mm using 2.5 litre crank.

JE pistons

Custom Arrow rods

2.5 cross drilled crank

Lead bearings

Uprated oil pump

Fully ported STi V5 heads, STi V4 valves, top hat shims and uprated valve springs

WRC spec cams/cam timing

Vernier cam pulleys

Steel head gaskets

4.6kg aluminium flywheel

WRC Paddle Clutch

Ported Gruppe-S headers, Helix flexi up-pipe

Full de-cat Hayward & Scott custom built 3 inch straight through exhaust system from turbo back

TD05/06 20G Turbo (currently max boost 1.5 bar - 22 psi)

HKS FMIC with re-routed intercooler water spray

Forge Motorsport VTA Dumpvalve

Custom air intake

Nismo 740cc injectors

Uprated Walboro 255lt/hr fuel pump

Uprated fuel pressure regulator

Modified supply to fuel rails

Link ECU - mapped by Pat

Guages - SPA digital boost pressure/temp & fuel pressure/oil pressure. Avionics individual EGT header mounted probes x4 with digital display. AFR guage. Waiting for release of new Knocklink guage.



Oh and air con stripped out to save some weight!


The car was running a Lateral Performance uprated organic clutch, but this couldn't hold the torque. It has been mapped on normal super unleaded and we estimate around 400bhp, but torque of around 450 lb/ft.

Spool up is instant - it feels as though it is a normally aspirated 5 litre!

I always intended to overkill the engine spec and produce something extremely driveable. I can't tell you how pleased I am with this set up and it is probably untouchable on these roads in the Isle of Man!

Just don't ask what it all cost from start to finish!

Kind regards
Andrew

911

Gulp.
What gearbox will take that?
911.

Andy.F

Well I'm hoping my sti5 box is going to thats with similar boost and a few more bhp from the Garrett turbo.......... time will tell !

Tone Loc

iTrader: (1)

Andy... what happend to your dog box?

Tony.

megrac

thers's a guy here in New Zealand with a ver5 sti that has a 2.5 in it and a trust t67 with just over 500hp at the engine. its been in this tune for about 3 years and it still has the factory 5speed intack.
the 2.5 is an n/a block closed decked.