any benefit from 10% methanol map and gt spec 2 headers whilst running vf34 turbo apart from better spooling ~2-300rpm and ~10bhp gain-ie worth doing it now or leaving till i get new turbo like a md series one
martin

 

gained 30bhp and 10 lb/ft with a methanol map 2 yrs ago on my old wrx running a vf34,just a question of whether you think its worth a map for those gains?

 

For doing nothing apart from mapping on methanol I would say thats a cracking jump Its obviously a 10% gain??

 

If you are running the 3 bolt flange headers you will get a big improvement by replacing the existing uppipe with a "Special" which is purpose designed specifically for these headers to improve spool and torque.
The GT Spec tubular headers are not the best choice for a VF34 turbo.

 

harvey, for which turbos are the GT Spec tubulars needed rather than your ported OEM ones, to be considered a worthwhile upgrade? I'm assuming the GT Specs are best used with turbos that are capable of over 400bhp... or would it be at 450+?

Even when one does upgrade to the GT Specs, is it best to junk their up-pipe and replace it with one of your OEM ported jobs (presumably it's narrower than the GT Spec item?) for quicker spool up?

 

nice gains on methanol!!was it mapped for that i presume??
interesting re headers i thought tubular was the best way to go as even ported headers have their limits-i have a vf34 turbo at present and plan to upgrade to likely MD321 next year so would it be better to wait till i get turbo before changing headers??
i thought the gt headers came with uppipe already or are you recommending a different uppipe??
thanks
martin

 

There is no set breakpoint where fitting tubular headers becomes a clear choice or vice versa. However, GT Spec tubular headers on a VF34 would not be a choice I would make. Spool is moved up the rev range by a big margin. This has the effect of putting your foot down at say 3000 rpm and then waiting for something to happen. Ported O/E headers and matched uppipe will improve spool and responsiveness noticably over the originals as they come from Subaru. The car is crisper with more torque right across the rev range.

The GT Spec headers come with their own uppipe but I have designed a replacement uppipe which will improve the performance substantially and these have been fitted to numerous applications all the way from 380 bhp to nearly 600 bhp and some of the improvements have been astounding. Like 500 rpm earlier spooling. This margin will not be repeated in all instances but the improvements are such that once the replacement uppipe is fitted the fuel map needs attention as the car will need fuel in the new spooling area and generally across the rev range.
More fuel = more power.

 

probably best me just getting second methanol map on vf34 then when getting new turbo get gt 2 headers with your uppipe as 500rpm should easily offset bigget turbo
thanks
martin

 

Thanks harvey - I've always wanted a re. yours vs GT Spec.

I have a set of ported OEM headers/up-pipe to go on with a FMIC/IK/740s on my MY93 WRX (with TD05 16g). I take it that these ported jobs will be just perfect for this level of tune i.e. up to c.350bhp when mapped?

However, there'll be a chance later on that I'll want to go to 400+ on a S206, MD321T or your own HS420... would it be better to swap over to the GT Specs + your specialised up-pipe at that point, then?

 

yes andy mapped it again for the methanol

 

similar turbo, mine was a vf35. Fitted GT spec 2 headers with supplied up pipe and my turbo spooled up an easy 3000 rpm earlier.

been told that the vf34 is good for approx 10bhp over the 35 and I was running 370 bhp 360 lbs-ft of torque was on full boost of 1.5 bar at 2700 - 2800 rpm with 10% methanol

 

500 rpm was one particular example, Paul Armin on a 2.5 somewhere between 550 and 600 bhp. Different cars respond differently but we have not fitted a replacement performance uppipe that did not result in a worthwhile improvement.
Joz: For what you are doing for now I would stick with ported headers and matched uppipe.
Mac, is this a 2.5?
Obviously your previous setup was very laggy

 

nice i presume 2.5l 2005 sti from sidc?
will get run in map as new engine on murt then get 2 maps 280 and plus methanol on 2.1 stroker then get a MD321m possibly
martin

 

Beat me to it, harvey