Hi guys, I've been slowly trying to up my knowledge on Scoobies as im working on my own, and slowly upgrading/staging my 98 JDM STI as you may have already answered some questions for me already (thanks).


I just have a few questions grouped together so I don't have to make multiple posts. If you can answer any (or all!) its a massive help, and try to keep in Lehman's terms if possible, though I do do quite a bit of research so if it cant be simplified any more just put that down..


1.BoV - Does upgrading it to an actual decent one like Turbosmart improve (reduce) turbo lag? Or are they just sound/ventilation


2. FMIC - Do they increase BHP? Will I need to replace my panel filter with a cone filter as that's where the pipework goes? Will I need a remap after it to truly feel the benefits?


3. FPR - Is this a worthwhile upgrade? What do it do? Does it keep boost pressure more stable as a result of constant fuel pressure?


4. 3Port Boost solenoid - Does this improve/help boost? Would you recommend getting a controller with it so I can change the boost anytime?


5. Do I need uprated hoses (Samco etc) to handle increased pressure in the system? Or are they just for safety/aesthetics?


6. 740cc injectors - Is it worth investing in these for a car aiming at 400+ BHP?, or will 550cc suffice? Don't want to waste money installing 550cc when 740cc are needed later on but can be used earlier. Do they just allow a higher fuel rate or do they do something more specific?


7. Will all of this (if done and mapped correctly) increase my performance/power/response/boost, or is the main improvement a new turbo (321H/T)? How much boost can I set my TD05 (I think in a JDM 98 STI? correct me if wrong) to realistically without serious risk to turbo.


Massive cheers in advance,


I'm trying to learn!


Ash

 

1/ No - OEM is fine

2/ No not on their own but when mapped in may allow a few more ponies. You will need a cone filter

3/ Dunno, never had one but you logic sounds fine.

4/ Helps with boost control. I had one but wasn't really aware of what is was doing. Forget a boost controller unless it's in the the form of switchable maps in the ecu. Potential boom otherwise!

5/ You don't need them at this level but remember yours could be 18 years old!

6/ Not sure on this one but I'm sure 550's would be OK at 400bhp but would be close to maxing out.

7/ You don't mention a remap. That with all of the above would see you around 350bhp on your TD05 (if it is a TR05) with the weak spot being your gear box!
You don't say if it's a V4 or V5. The V5 has an ecu which can be mapped but the V4 doesn't unless somethings changed that I've missed. I've not had an Impreza since 2007 so may be slightly off the pulse

 

first off thanks for the reply!


Its a V4, Sorry! Its been mapped by Andy Carr, I'm 90% sure I paid for an ECU as well as map , but I'm unsure as to what ECU he uses. I'm seeing him on Saturday so hopefully he'll clear that up for me.


also forgot to mention I'm running ported heads, walbro 255 , 3" system, decat downpipe, if that makes any difference


Ash


edit: aren't STI JDM gearboxes meant to be good upto 450?

 

sorry i had to laugh, the ty754 is the stronger of the 2 gearboxes and its pushing its luck at much over 300lbs of torque, and its not the one fitted to your car! (You have a ty752)
Some have run them at 350lbs but have been sympathetic, and some standard ones have shredded themselves on uk turbo's.

6 speeds are much stronger but add about 30kg's to boot.

 

FMIC will help with heatsoak and help prevent the onset of det(if you're wanting 400+ then you will be wanting one)
Yes you will need to upgrade the standard airbox.

3 port not needed but will help boost control in higher load and rev ranges(i still have a 2 port@circa 400bhp)

FRP not needed(i'm also on oem one) if you intend to go parallel rail setup then get an aftermarket FRP.

I would go bigger than 550cc injectors if you plan on heading north of 400bhp

Your standard TD05 will run out of puff at around 350bhp

Your 5 speed jdm box will also more than likely not last long if pushing 400 with similar torque.(best looking at a 6 speed conversion if you want the magic 400)

 

Sorry, I'm just barely getting used to engines let alone the drivetrain! Also I have misquoted the information I've read! its 400+ not 450+ I meant..


"The V3-4 Sti Gearbox is stronger than the UK or previous versions however Level 4 + Power may shorten the life of the transmission this will depend on type of use and driving style"
taken from AFP (Level 4+ is 400+)


Is this right or wrong? Again, noob hereso go easy!

 

What makes you say Level 4+ is 400+?

It's not BHP that will kill your box it's torque,and in most cases 350ft/lb is at it's limit in the gearbox you have,all depending how you drive and use the power of corse.

 

Just going off the master (andy forrest)'s guide on his site.. However all 3 of you have said the gearbox needs a look at, so that is what I shall be researching the next few days!

 

Oh and i forgot to say,there is an upgrade for your box which involves fitting blast plates,they were developed in the US but there is a thread on here with someone who has fabricated and is selling them,not sure how effective this mod is? also you can get stronger gear sets,but with the costs then you might as well go for a 6 speed conversion.

 

I've opened up a whole new can of worms looking into this 6 Speed conversion >.<

 

and I was crying at the fact AFP321's are like £1500+... Looks like I'll be spending a lot more nights in the lockup (and more overtime at work!) than I originally thought!

 

yeh
my bloody messages keep disappearing and site crashing!!

but the 6 speed conversion is worth it imo

 

I was recommended to go 6-speed by David O'Brien at API when heading to 400/400.

 

To build a genuine and reliable 400+bhp classic impreza you will be 10 grand deep easily.

 

Pretty sure mine is at 400+,not been on the dyno yet(itching to find out tbh)
Cost me under 6k
Saying that most of the mods were done when I bought it so might have 10k+ put into it?

 

What cost you under 6k ???

 

The car

 

Like I said, to BUILD a reliable and useable 400+ classic you'll be 10 grand deep.

 

Thought I'd done well then.

I do hear what you're saying tho Matty,from a fresh start/new build 10k minimum for north of 400

But I still think,if sourcing 2nd hand/recon parts....
Forged shortblock 2.5k
Recon 400+ turbo 1.2k
Recon 6 speed setup 1.5k
740cc injectors £150
New high flow fuel pump £100
Plus a few other bits and bats brakes ect
You could build a 400+ Reliable car for under 6k

 

Add brakes, suspension parts, front mount, mapping and then ofcourse labour cost if your not hands on.
I've been there, the costs spiral.

 

Hands on is the best way to be,including mapping
Add brakes,arb,droplinks,fmic and ESL. Still around 6k

 

If you can build a 400+ classic thats useable to its full potential and also reliable from a standard car for 6 grand then kudos to ya fella, most can't

 

No kudos for me mate,I've not done it,just bought one that had already been done,then remapped it.
Just saying,for 6k you could build a safe 400+ classic