Power increase advice
 

im looking at taking my 2003 blob sti uk off the road for a while and doing an engine rebuild as the car is now on 75k and the clutch is on the way out

im looking at taking the car to around 450bhp

the mods i have so far are

• APS Induction kit
• Uprated fuel pump
• Full decat TSL exhaust and down pipe
• WRC Remap
• AST Suspension with anti dive kit, poly bushes and 4 wheel alignment setup

current power figure is 358bhp however the car is very laggy. it performs great on a drag strip but on a track it is very hard work to keep it on song!

what mods should i do with the rebuild?

how much power can the standard internals and gearbox take?

thx guys
J

V.8 Sti's like yours will take 400-430bhp all day long without any issue. After that you start to increase your chances of engine failure thus living on borrowed time, although i've heard of STi's taking over 500bhp on std internals and still running strong after 2-3+years. You take your chances really but at 450bhp it's not beyond the realm of possibility that your engine would be fine with that even at 75K miles.

75K miles isn't a huge amount of mileage in STi terms. If it were a WRX engine then i'd be concerned although you can take them up to c.320-330bhp but at 75K miles even withing max safe bhp limit long term prognosis isn't great for the WRX.

IMHO get more power from your std STi if you can, wait until it goes bang and then do the rebuild. You're going to do a rebuild anyway so you have nothing to lose. Your engine may well surprise you!!

Out of interest, 358bhp is well within your V.8 safety limits and at the limit of the OEM VF35 turbo used on the V.8. The VF35 is not a laggy turbo so i presume you're using a different turbo like a TD05 18/20G.

18G's are still very good for not being too laggy but the 20G (as i run) is very laggy, especially on a 2L. Once it's going though it keeps on going right to the red line but it does sound like your car needs a remap paying special attention to AFR's and the AVCS map. Tuning AVCS properly can reduce some of that lag. Mine is laggy in 1st/2nd/3rd gears and doesn't really get going till about 3800-4000rpm, although in 4th and 5th it comes in around 3500rpm which is about right for the 20G.

2.5 and wave goodbye to lag.

Edited to add: The gearbox is more than strong enough for your requirments, just get a proper turbo like the MD321T and bigger injectors c.700cc, + FMIC and you're away!! If you still have standard headers and uppipe it's worht changing to something like the GTspec GenII or Kakumei system.

no its defo a standard turbo mate, it doesnt hit full boost till about 4k its running 1.4Bar

That sounds a very late. What gear is that in ?

about the same in all the gears mate

its very all or nothing!

Doesn't sound right to me - can normally get full boost WAY before that. What does your mapper say about the slowness of the boost building?

Jesus, even on my WRX boost comes in before 4k.
Have you had it mapped for economy? ;)

Your VF35 should be kicking in very nicely from about 2800rpm with full boost by about 3100-3300rpm dependent on the mapping. As Duncan says...not right!!

Your WRX should be coming in around 2600rpm with full boost by 3000rpm.

Lots of laggy standard turbo's on SN. what going on?? :eek:

i didnt have it mapped it was done before i bought it

as i said up a drag strip it is great it pulls all the way up to the redline very well, a lot of people commented on how fast it is for the power its producing

but in track conditions you have to get exactly the right gear or your screwed

The std map on a catted wrx brings boost in really late.

Torque is what you need for track conditions ie boost earlier.

ive been recomended to buy headers to improve turbo spool

I would say that they would have the opposite effect if you change the up-pipe aswell (which you probably will). A bigger uppipe than std would just make it laggier.

At most you might want to port your headers, de-lug them, then wrap them and the std uppipe and see how that goes before spending any more dosh. These are things you can do yourself. The standard uppipe is pretty good with the only difference being that unlike aftermarket uppipes it's not made of stainless steel but it does a good job.

The std map calls for just over 1bar of boost from about 2800rpm at 43% throttle. I wouldn't have said that was particularly late as it's a factory compromise between cruising economy and blatting power but in practice it does start to come in fairly early. Without looking at your car it's difficult to say what it is because it probably will be something to do with mapping but also you could have an uppipe leak or cold air leak somewhere contributing to a lack of boost low down.

:eek: i never knew that do i have to start wqorrying about my WRX exhaust and remap with 77k? bit of a noob at the moment, is it mileage based? or power based?

I wouldn't worry Baz.

that is nothing as long as it is looked after..

Ran one Oe engine to 200k at 330bhp for most of it's life.. and it was still running when removed

Simon