Torque

[DJPGT4st205]

Im planing a few mods soon to my GT4 ST205

Main modes are gona be:

New ECU

Intercooler air/air (Cant find an upgrade for air/watter for GT4)

Biger trurbo (not magger biger one that will deliver maybe 20-60bhp more) bu with less spool time than stock.

Custom De Cat, exhaust Manifold and (exhaust to back but has HKS on atm so wont be for a wile).

Got HKS intake

maybe few uther odd bits here and their.

Now this is my consern, I dont have time atm to take the block out and change pistons, cam's and rods, when i do ill port and polish too, but what sorta Torque/(boost) can the GTE on ST205 stock internals handle without a re build? Eny/all info you have would be grate ^^

[dawesy]

OK. here's what you need

depending on year decat with Aussie/xspower downpipe.

replacement panel filter (blitz etc) or an induction kit well shielded from engine bay.

electronic boost controller set to 1.1bar.

that will net you a safe 300 ish BHP

that to be fair is about as far as is really safe on the stock pistons.

as for turbos you can fit a hybrid CT20/26 which will give better power at the same boost

if you get the time and swap the pistons for JE forged items then 450 BHP is OK on the stock rods and crank but be sure to use a full ARP fastener kit for the bottom end

[Sketchy]

Also you'll be lucky to fine a turbo that can produce more power and spool up quicker than the stock item, generally speaking if you get a hybrid capable of more power you will lose out slightly on the spool up. It's down to physics, only way round it is with a variable vane turbo like renault use, and also the new porker turbo. Esentually they act like small turbos at low revs so spool up quickly then large turbos at high revs producing more boost. However vv turbos are still a bit on the new side for the performance upgrade market so cost is still high...

A decent mappable ecu alone (in the hands of a decent mapper) will see a decent power hike of around 20-30BHP even without increasing the boost. So you should be able to see a decent 300-330 with everything you've mentioned without a new turbo.

Just watch out for boost creep on the stock turbo if you go to large on the exhaust.

[DJPGT4st205]

Yeah i know a little about the boost creap on GT4's i read up a bit on it, so i was planing to get 2.5" instead of the 3" right though.

As far as turbos, i was under the imption that the ST205 turbo was a lttle dated now, and newer turbos (as long as not a mager upgrade) would give u less lag than the older stock turbo.

I wanted to upgrade the pistons and rods +cams at some point but i was hoping to up the pones in the meen time... i guess i could just get the JE pistons as 450bhp is pritty nice, iv sceen the Pistons for £450 so that might be well worth it.

[DJPGT4st205]

Had a little think about this, and i have anuther question

Why are te pistons only good for 330bhp and rods 450bhp i always thought that the rods were the 1st thing to go.

[Sketchy]

Because the stock rods and crank are actually very good and outlast the pistons.

The stock pistons are actually very strong, but their also quite brittle so it only takes a very small amount of det to destroy them. Assuming you get the car mapped well and keep intake temps down then you should be able to keep det at bay, however the increase in Combustion temps with the higher boost is the next thing to worry about as this causes extra piston expansion which increase the ringland wear which also sees the end of the pistons.

Regarding newer turbos, the CT was quite advanced for the time it has ceramic internals and twin scroll turbine both helping to improve spool-up time. Most hybrids are made to work above 1.2 bar and don't really get into their stride until then. As I said I think you'd be lucky to fine a alternative that allows more power and quicker spool-up with a decent intake and exhaust system you should be seeing 1bar by 3000rpm with the CT20b and the effeicency limit is about 1.2bar.

Also above 340 you need to think about uprating the fuel injector/fuel pump etc

[DJPGT4st205]

Yeah i knew the Turbo was ahead of its time, but i was hoping advancements in Tec would have made a better one by now :( never mind ill just have to wait for the new porche 0 lag one lol

So pistons are a must then, >< to be honest im not realy after pones just shere power, i wana do some times at santa pod ^^ i was planing on going to 400 maybe 450bhp just gearing up for high levels of torque, hence i want the fast spool up on the turbo, but i guess after a point the biger turbo will be better.