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Bw efr 6258g vs IHI vf 36


Dre

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Anyone out there used a efr 6258 twin scroll on 2 litre engine or know of someone who has.Looking at replacing a vf 45 with either a efr 6258 or vf 36.I need to be able to clock compressor housing to 12 o clock position.Custom up pipe,turbo down pipe,tgv deletes and fuelling will be done at same time.I’ve had two tunes done on the vf 45 and custom 2 1/2” turbo back decat exhaust.First tune was a torque monster running 19.5 psi which I liked a lot but would not hold the tune.Second tune was less boost running 18 psi and moving the tune further up the rpm range.Car is a 2007 Legacy jdm manual and I would like to initially use the factory tmic.

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All the information available for the baby efr turbo I’ve read is based on 2.5 L engines.Efr power rating is 260-440 hp.Apparenly spools up a lot faster then a Sti turbo and does not taper off boost at redline,2.0 L engine.Factory tmic stays as I’m not interested in big power figures,but will probably be replaced by a fmic later,or sooner if required.Vf turbo is a easier install if I can clock the turbo compressor housing,waiting to hear back from the workshop.

The vf 45 turbo design is a bit of a orphan and I want a larger exhaust housing.

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Problem is mating to the limited design of the TMIC. Suppose the 90 degree section could be left off which could open custom options up slightly. 

Every option is a heap of work as headers and uppipe are needed along with a custom downpipe and compressor outlet so it’s a fairly expensive route regardless. Just go for a custom FMIC at the same time and you’ll end up with a much better setup for not a lot more

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10 minutes ago, boon said:

Custom up-pipe/downpipe or are you just going to change to STI headers?

If you're going the custom option, seems like a shitload of $ to spend to make 200kw.

I’ll use my factory headers.200-210 kw atw and max torque  kicking in just after 3000-3500 rpm makes for a great practical road car.Vf45 is pretty much maxed out at 18 psi,full boost starts at 2800 rpm and stays flat to 5200  rpm and tapers off. Has been tuned running 19.8 psi,torque comes in harder but boost tapers off earlier.Computer would not hold tune.My thoughts are that the vf45 turbo is working outside it’s efficiency range above 18 psi,9.5 compression and tmic.Power for both tunes 185 kw atw on different dyno’s.

Don’t forget the Legacy short block starts to get unreliable at 200 kw atw and the heads run out of flow at 240-250 kw atw.

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I'm doing a build with a similar turbo, 6758 v-band EWG. It's a single-scroll turbo but I'm running twin-scroll Impreza headers and making a customer rotated pedestal. I'll be running my car in with a VF36 however while I get stuff fabricated.

 

From the results I've seen in my own car and in speaking to others with very similar setups, VF36 will max out around apporx 240kw on 98 and approx 280kw on Ethonol.

 

In regards to the 6758 for my motor, 2.1L, I'm expecting to make some decent power as I'll be running it at some pretty high boost levels with a balanced motor that flows a lot of air. A friend of mine is running this on Hyabusa motor, 1300cc, on 7psi making well over 300kw. This is dedicated track car however, so I don't really know if it's comparable. 

 

While my friend and I have identical 6758s, they are not the 'off-the-shelf' variant. They've been modified to run in the Indy Car series so I don't know if they flow any differently or what have you.

 

However, buy a turbo to suit a) your driving style and preference b) power goal. There is no magic turbo, so like most people, you'll have to sacrifice one or the other to find that happy-medium 

 

Re: your comment above about "boost tapering off" - are you saying the boost line is not horizontal all the way after hitting the target boost level? I can understand torque and power tapering off but if your boost is taping off wouldn't that be a leak or something?

 

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No leak,just a small turbo running out of puff.Yeah,the efr turbos are nice.Was looking at the 6258 twin scroll,vf36 on steroids.Spoke to a guy in the States,mentioned that if you don’t like turbo whine this is not the turbo for you.

 

 

 

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Will need to do a bit of customising to the uppipe if using the Legacy headers as the uppipe to turbo flange is different

 

What was the peak torque you’d see with either of those tunes? Seems like you’re needing a heap of boost to get 185kw. Obviously it’s tapering by the point you’ve hit peak power, as most OEM Subaru turbo’s do, but mine gets 192kw and only momentarily peaks at 16.9psi

 

Also what are you meaning when you say that the computer won’t hold the higher boost tune? 

That it was knocking and had to drop the IAM to stay safe?

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PBMS 19.8 psi 715nm

TT       18.0 psi 385 nm

Car went onto PBMS Dyno three times for reflash after car lost tune.No knocking,or fault codes.TT found the passenger side exhaust avcs was playing up.The winding in the oil solenoid valve motor had a break.

Regarding boost and power output,car runs turbo back 2.5” decat exhaust with factory mufflers.Possibly shows how inefficient the factory tmic is.

 

Edited by Dre
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