So my new 2.5 WRX is going in for a major srtip down in a couple of weeks, new heads new stage 1 clutch, oil filter, coolant flush, NKG plugs, timing belt, waterpump, walbro fuel pump, full decat. and so on.

After this it will need a remap, but im unsure to hold off on turbo upgrade and just remap for now until I know the car is all running well.

I'm looking with this little project to run 350bhp which is the safe limit for these 5spd gearboxes apparently.

what turbos can I just slap on and remap that will give me a wide power band through the revs. suggested VF43 are there any others to look out for?

Am I tempting fate to consider a bigger turbo than a vf43 and push for the 380/400bhp and if so what turbo to achieve this?

 

VF34 roller bearing mapped well will get u approx. 350 ,350 swapped mine for this mapped by bob rawle good reliable unit with excellent low down throttle response, with some other parts as well . 3 port , rcm fuel pump, fmic, fpr , and of course alcatek ecu, incase I think of possible stroker engine , and indeed ppg gear set. but im more than happy with things as they sit. currently concentrating on other mods.

 

Most turbos are straight bolt on in standard position. You just need the accompanying mods. For 380-400. Consider something from the MD range - MD321H?
Or a SC38 or SC42? Or a slightly more old school TD05 variant - 18G or 20G.

 

The injectors on the Hawkeye are the same as the STI

 

you're right - apologies. I didn't realise that Hawk WRX and STI's shared the same injectors.

 

Don't get a bigger turbo than your power needs, it will just give you more lag and worse driveability. Stick with a turbo rated for 350bhp like the VF34, VF35, VF43, VF48 or TD05-18G ported.


All of these will work well on the 2.5 engine and bolt straight on. The VF43 and VF48 are designed to work with the 2.5 engine so are a better choice IMO.

 

but if the end game is 400bhp which then, and its 400 a no go without changing the gearbox. thanks for advice

 

You'll need to upgrade most of the parts to STI parts, like gearbox, diff, shafts, brakes etc etc.


Why not either start with an STI if your new goal is 400bhp or stick to a power level (350bhp) which is realistically as much as you can do to the WRX without blowing everything up.


Chances are that you'll get ringland failure or head gasket failure on the 2.5 anyhow as upgrading and pushing the engine will only promote these known failure issues.


Budget £3.5k for a forged rebuilt.


I had a 2.5 hawk WRX at 334/381 and it was an absolute pleasure to drive daily on the road.

 

Yeah its sat outside waiting for a new head now haha, plus everything else in post 1. suppose Ill have to live with 350 so many turbos to choose from its a minefield yet only the vf35s seem to be for sale.

 

Did you forge the engine to achieve those figures mate ? Or did you just upgrade it without forging it ?.

 

me?

 

Hawk wrx box will be fine at 400, they are alot more robust than early ones. But that said i wouldn't want to push the wrx engine anywhere near that without sorting the rods and pistons

 

^^^ completely agree. Good advice.


+ Head gaskets.

 

Really?

 

yep

 

Yes mate

 

Yep. The hawk 5 speed boxes have slightly larger gear teeth and can take more power and torque than the earlier newage 5 speed boxes. Someone on here a long time back took one apart and compared it to an older box.


Plus there are a lot of people running hawk WRX's with higher power levels with no issues at all on boxes.

 

Have to say I agree with that but a lot depends on driving style etc etc. I've ran 400 bhp from my first hawk wrx and had no issues. I think Martin Jeffrey ( engine tuner ) ran 500 bhp from an earlier post a while ago .
I'm at 390/390 on rb5 5 speed although that's running a 5 speed VBAAA so maybe it's a bit tougher . (P1 box )

Maz

 

That's interesting to hear

 

Can anyone tell me what turbo could be replaced with my current td04 on my hatch 2008 wrx ?. I've heard that I don't have alot of options turbo wise.

 

All the turbo's quoted in this thread bolt straight on to your 08 WRX.


Have a look at the turbo's in my post number 6.

 

That's interesting.

ive just spoke to Richard at fb tuning and he said that other turbos wouldn't mate.

 

Ah yes, you could be right actually. Doesn't the turbo bolt to the intercooler in a different way? VF52?

 

Yeah, he said that the turbo flange is different to other wrx's. I was thinking vf52. He said that I could replace the billet wheel but I'm not sure at what cost. Obvs a new bigger turbo maybe a better option and I think that the vf52 fits because the us version wrx are fitted with these apparently. basically I told him that I want around 300hp from the car but he said that I couldn't achieve that with the td04 without the billet wheel being changed.

 

having said that the box "could" take 400bhp is there a slightly more powerful turbo than the vf43, 34, and 35 that I could get closer to 400 with the mods in post 1.

 

Vf 43 , vf48 . Td05 18g . Td05 20g btween 340 to 390 maybe with this lot .

Maz

 

If the headgaskets have gone then you will need to do the bearings too. They are liable to fail in short order after HG failure and you will end up rebuilding again

 

By the sound of your rebuild, you are not fitting uprated pistons, head gaskets or head studs at the very least as part of a forged build? If not, 350bhp should still be your limit. You WILL blow the engine up again otherwise.


Just to give you an idea, a good forged engine build for a 2.5 engine that will handle 400bhp all day long will cost between £3.5-5k to do right at a reputable builder.

 

Running a vf34 with supporting mods on my 06 Hawk wrx, dyno print out was 331/330 but find it a bit laggy and don't spool up all that quick, hoping a harvey trick pipe and a tweak will help matters

 

I spoke to a guy from fb tuning mate and he said that the turbo flange on an 08 is different to previous wrx'. A vf52 maybe my only option. Only wanna push 300.