Hey, after a bit of help please.
A few months ago I bought a 2004 JDM STi, I've done the usual bolt on mods - fuel pump, 3 port solenoid, 3" Turbo back, Higher rated Actuator, K&N intake.

When getting it remapped, ran into issues where it just wouldn't make much power at all - around 320bhp. While trying to solve this and having a look around the engine bay he found I had a Spec C 1 piece intake manifold and smaller air con compressor. & now we're wondering if it's had a engine change at some point.

Is there any way of finding out if it's a Spec C engine or not? Without stripping it? It still only has the VF37 twinscroll and everything else seems standard - ECU, intercooler spray etc. So it looks like it's just the engine they've dumped in if it is.

Is there any common reasons it wouldn't make much power too? He eventually got it up to just under 340bhp, the main problem he had seemed to be fuelling. It was trying to use the off boost and low boost fuelling parameters while on full boost.
But my old UK spec Blob made 350 quite easily and I've read a few on here getting 360+ on JDM's without changing turbo. Wondering if I'm missing something simple? Could it be the ECU not working correctly with the engine if it is a Spec C? Any ideas what I should look into first or just accept I've git one that doesn't really want to make power?

Thanks in advance.

 

My jdm blobeye sti had the one piece manifold aswell

 

I thought that SpecC have VF36 as standard? well at least mine have.

 

Yes but his is a sti not spec c

 

Who was mapping it???

The spec C engine itself is no different to any other JDM STI. The C got slightly better heads but that was it.

 

right, my mistake

 

Ah, is that just standard on the JDM's then? My mapper said he'd only seen one on the Spec C. Then again he may just not have been looking on the others, only noticed mine when having trouble with the remap.
Did you get yours mapped? Any issues?

 

Is that all? Seem to read different info on each search I do lol.

And it was Gaz at GR Performance. He did a great job on my last one and does loads (although not that many JDM's). Plus he's sorted loads of little niggles out on it for me so trust him with it.

 

Yes had mine mapped no issues but i had a md321h on mine before i got it mapped so cant tell you anything about vf37 power

 

Ok, thanks a lot for your help Peter

 

VF 37 is a twin scroll vf35, vf36 is similar to a vf34 but twin scroll with a titainium shaft. all the vf series (30/34/36/37/43/48) have the same compressor size, so will give similar bhp, although torque should be better on a twin scroll.

 

He may have a thick lined block

But as above, don't matter what block you got as said above jdm and uk not much different in 'most'.

 

Yea I got better torque than on my last UK car so that was a bonus. Plus it's only 10bhp less than I was expecting and does feel faster (due to delivery of twinscroll and torque) on the road than my last so maybe I shouldnt dwell on it.

 

I would try a different mapper

 

My MY05 JDM STi had a one-piece as well so, to echo what others have said, and it's a normal JDM STi thing AFAIK.

Cams on an MY05 STi are the same as on the MY05 Spec C but not sure about an MY04. Heads are "large port" on the MY03 JDM onwards, I think.

Around 350 is the usual limit for a VF37, sometimes more, rarely less: that's what mine got with a panel filter and a 3" decat. If your exhaust has a sports cat then around 340bhp is the upper limit.

20-30bhp lower could be the mapping, or the fuel (was it VPower?) or some other fault - but the mapper should have been able to point you in the right direction I would have hoped.

What was stopping the power? Was it knock? Or just not responding to more boost, or timing? That would give a clue as to what was amiss.