Gripless

Grap the dyno plot from @Niran build thread linked below. Look at the power at each 500 rpm and the power the car makes. Even a stock turbo sti can push 145 kW at 3500 rpm while that car is still at 100 kW so you're almost 50% more power down low. Niran's already at 190 kW by 3500 rpm so almost double the power i.e. He wins. Now if you draw an imaginary line from say 2000 or 2500 rpm to the peak power. A) the plot should stay above that to be torquey and good to drive. It should start close and go up as vertically as possible then curve across to peak. B) exactly on that line is like BMW and Audi nice linear smooth power. C) If it stays below that line then rapidly come up like a string hanging under the two points the car will be peaky and S*** to drive daily. that one you posted is all over the place so maybe ok to drive but a bit laggy under 4000 rpm as the turbo spools slowly. if you take 10-15% for the header length and another 7-10% for drive train 4wd loss it's no as bad as it seems. plus boxers are balanced motors and weight of the block is stuff all so there are advantages to be found. oh yeah that's 254 kW on a stock turbo so some thing to think about even though it's a 2.5 sti.

Not sure these guys will do the stock ecu without ecutek fees, licenses etc but they are local. http://www.wrcdevelopments.com/about

Isn't launch control just a two step rev limiter. It doesn't build boost just holds the rpm limit low which the clutch in. anti lag will build boost but from the sounds of it you want the anti lag only while the launch limiter is active. Not sure on the link what your options have, but you could use speed as one of the conditions and under 10 kph have it enabled. It's a trick used on old ecus when you didn't have a clutch switch and you only want something to work on launch.

Stock ecu

Yes but that 22 psi is low down in the sub 4000rpm range as the Stock Wastegate actuator and pill can't hold more than about 15 psi well before the redline which is why the peak power isn't as high. The area under the curve is about 30% greater which is what makes a car fast and drivable. Peak power isn't everything That plot you put up looks like it will drive like a modified vtec, nothing then everything like a switch. I have a dyno plot here of a ej20 on 14 psi making 214 kW at the wheels. The plot is a straight line from 2500 up to 7250 rpm and 214 kW then flat to 8000 rpm.

I want to order the usd$40 one that looks like the stock one and give it a go. only thing is twin scroll all have bends in the rod and they only sell single scroll straight ones so have to customize it.

@Pappu1 I found them somewhere else originally but... https://jtune.co.nz/products/subaru-twin-scroll-t4-turbo-kit That link is for a full kit but has links on the lower right hand side to the pipes. twin scroll is all new to me since I got the v11 and stopped playing with NA cars again. Ceramic coating works about 10% more efficiency than the pipe alone but it's about $850 to get the stock headers and dump pipe done. But even the $250 to do the exhaust housing makes a difference if you want to stay stock and gain power and increase spool up.

Thicker steel traps the initial heat so may indeed spool the turbo faster through less energy lost as heat, so true under limited conditions. Seen dyno runs that have a few hundred rpm quicker spool with the header heat soaked over a cold set. bigger pipe will allow higher power than the stock ones, so true agian over something well over stock hp. factory headers may be worn from heat cycling and good heavier after market ones could be a nice option. then they look pretty and all shiny which is the most important factor. Edit: Marketing is very loose with claim details as while there is likely evidence to support claims it's for pretty specific cases or tested on older or standard model factory parts. The cake is a lie!

Not saying that this is the case with these headers but there is the practice of binning. ie say Tomei design and get headers made at SSI. they have a quality standard that must be met in the contract. Anything that fails that isn't scrapped it is sold to another brand that has lower standards. this isn't a bad thing if the brand you buy isn't too low down that quality chain or is an over supply issue. Some of the standards are based on finishing like a finer grind on flat surfaces or even little chips like the edges like @StrokedEJ last photo, though that could be as much as laying it on the edge on concrete after purchase, that can still fail quality control if done in the factory. Having seen some lower binning levels samples from some manufacturing plants those headers look pretty tidy from the pictures. And @StrokedEJ mentioned weight is a dead give away that the material used is to save money either being thinner or lower specification. Flanges should be nice and thick too, which they are and holes are tapered.

I did wonder about the factory ecu controllers ability to cycle the 4 port fast enough. It must be twice as sensitive to each cycle so the frequency ideally would need to be higher, maybe the newer ecu or external controllers cycle faster than the older ecu. isnt the point though that you can run different boost levels with a light spring giving low boost and then the dual port give is the higher boost settings. With si drive you called have i 7psi, s 20psi and s# 28 psi or whatever max psi you want. Also limp mode would still work correctly as the ecu will be coded with the Wastegate low psi rating. Not sure if limp still monitors boost pressure so just guessing and hope not to find out. if it's a track car then sure it is just wasted parts where a spring will do and far less to go wrong.

How much more power do you want? What's your budget? Do you drive the car everyday?

Fred the fan and Ron the radiator always hang out with Pete and Jeff before anyone asks who they are.

Welcome to the Americans own the Internet and therefore all Subarus must be single scroll now. Tomei do their one that with cams makes 400 wheel hp which I'm pretty sure @mlracing.co.nz can get. Hks must do one as well. There may be other Japanese brands as well. EFR one is in @Niran build thread. J tune make a replacement up-pipe so that must open more options with its t04 flange like Garrett. https://www.edoperformance.com/products/tr-gtx2971-twin-scroll-for-subaru-wrx-02-07-and-sti-04-18

That will be as effective as a single port and seems pointless You are still always applying pressure to the bottom, with 3 port setup so best case zero sum across diaphragm. Boost top and bottom just equals out so back to spring pressure, With 4 port you get atom bottom and boost top until it's cycled so boost plus spring to keep the gate closed.

Has anyone other than @Niran looked at more than the outdated factory actuators? Oem looking dual ports for usd$30 good for 25psi (higher options are available) https://www.speedyracer.com/Turbocharger-Internal-Wastegate-Actuator-Dual-Port-fits-T3-T3-T4-T04E- They still need a 4 port solenoid which seems to be about $180 but gives a fully stock look. A fully electronic actuator based ones for reasonable Cost. VW ELECTRONIC TURBO ACTUATOR 1.2 TSI 1.2 TFSI https://www.ebay.co.uk/p/GENUINE-VW-ELECTRONIC-TURBO-ACTUATOR-03F145725G-CBZA-CBZB-1-2-TSI-1-2-TFSI/652325228 depends on the control signal but if it's PWM then it would be plug and play (well tuning needed)

You could put the horn in front of Pete he won't mind, won't make too much difference as long as it's not going to hit pete when you go over bumps. give the alloy pipe a clean while you're there, but don't polish it. A light scuff with scouring pad from the kitchen works. Rough surface coolers better.

I'd name it Pete the Power steering cooler

Maybe true a few years ago, but to find a clean and tidy sti wouldn't that be bloody hard?

Can always just pick the other model parts up that bolt on so it's still OEM just newer. must be some v6-8 parts that fit. that way you get a little more power for way less spend and it still looks original and tidy.

What's the factory pressure written inside the drivers door sill by the lock catch? Think factory there is a few psi difference front to rear due to the weight balance to keep the DCCD happy. Somewhere between that factory pressure and the max psi rating on the tyre works. Think im some thing like 38 front 36 rear on 45 profiles but it's the value on the door sill plus 2psi over winter. you can run more on pure nitrogen as it won't expand as much with heat like the 21% oxygen content in the air. Which is only a benefit in traffic really where the tyres don't heat up. Low pressure like 35 psi on 45 profile tyres won't be pretty at 100kph and a big pot hole.

Page 127 under "danger to manifold" section.

Don't forget header length and heat losses add up, one of the reasons why the newer FA series has the front mount turbo. im pretty sure the stock sti can hit close to 240 kW with the stock turbo

Pitty the Nissan ones seemed to have a circlip which would have been nice. Looks like Mitsubishi one from galant is the same and pressed or welded together. Those LSD spring plates are just long life shims the alloy breaks down before the gears. But if the gears are worn the springs allow it to be more predictable. Used to be a few hundred each and common in America.

Only thing I couldn't see was the larger bearing carrier must add weight and offset the saving in the wheel. otherwise heaps of cool things. think I'd still keep my gfb BOV without the noise it's not right, and the boost solenoid. I can see why they have them built in as an option and is likely better than most OEM ones and shortens the hose mess.

@nztintin Yeah that sums it up alright average results at best and high wear rate. If the spiders are already wearing then it will be unpredictable. I think maybe it's binding the coupler to the diff housing so it will be forced to turn the shaft, or its just crushed so it locks up. There was a Subaru post somewhere that did the same but no results posted. That's how I found that d1nz link the first time. @Loren yeah I don't get it fully either but the Nissan guys get results with it so it kind of works. thicker oil or a new unit in the diff sounds like the only reasonable options. Is the coupler sealed or can you open it? Could get a new set of plates (dealer will tell you if there's a rebuild kit) to go in it or fill it with thick grease and seal it up. If you where going to weld it then sell the LSD and F*** an open diff with welding. Assuming the LSD is worth more to someone else.