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My build/conversion project


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Wasnt sure in which section to post this, so opted for here for now.


I did say, I would let you into my build idea at Christmas, so here goes. :)


The car as it is right now

Its a Subaru Legacy BG5 Twin turbo GT-B Ltd in Cashmere yellow.






Its a bit of an oddball car to be honest. One or two things didnt stack up when I bought it so a bit of research was required.


First, the roof. The eagle eyed amongst you will have noticed the lack of roof rails. Having taken the roof lining out, I can assure you that the factory did it. No signs of any work to fill any holes.

That LED me to find out that the only models that had no roof rails were either the BK model which the USA got but that had a flat roof, or the BG model that they called the 'racing wagon'. These were made to order for the track.


The next item we found that was odd was the interior trim. Nothing matched. The front seats, the door cards and the rear seats all have different materials. The carpets were also just thrown in and not fixed down. Under the carpets were signs of a cage being fitted.


At this stage I would have said it was probably used on track and then stripped of its best bits, and any old interior thrown in, just to sell it. What stops me saying that though, is, why use a Ltd model, with the rare front bumper and special trim fascia bits?  Its all a bit odd. 


Anyway, its only been in the country for about 2 years and off the road in my ownership for over a year of that time. We bought it as 'spares or repairs'. This was due to the engine failing to start on occasion for the previous owner and various garages couldnt work out why. He didnt want to risk it any more and we bought it.


Strangely, once we trailered it home, it was fine and work flawlessly for a few months. Then, one day it wouldnt start. Lights on dash but nothing else. Despite my knowledge of these cars, we just couldnt get it started. As I had another GT-B anyway, this got put on the back burner.


Then, I came across these pictures:






My first thought was similar to 'I want those wide wings'. Not sure about the full body kit, but the wings are just awesome.


Thats where the plans started!!!


I've never been particularly conservative when it comes to altering my cars. I dont like following trends.

This was my last car that I owned for about 5 years and gradually it evolved into this.




Anyway, I,m still looking onto bodywork mods that may or may not happen. Mechanically, however, things are changing.


This is the work done so far:

Complete loom change. (never did find out why the car wouldnt start, so stripped the entire loom out and started again)


With the engine out, cleaning can start.









Next stage was to swap out the gearbox and rear diff. The Legacy ones are ok for up to about 340-350bhp. An upgrade was required, so a box and diff were aquired from a WRX and fitted.


Its worth pointing out that at this point in time, the plan was to go for about 400bhp by changing the twin turbo setup for a single turbo.


Its was just after the gearbox was fitted that my plans changed a bit. :ph34r:


I managed to obtain a very good condition 2.5 nitrided bottom end for a good price. The plan was to use this in a single turbo conversion with a MD321T turbo and stage one was to reign it in to 400bhp for now before increasing power later with more supporting mods.


It was whilst I was looking for a turbo that things changed again, with the arrival of a GT35 turbo. It was a bit of an impulse buy and only once I had it, I realised it needs rotated up and down pipes and external wastegate.


This is fast becoming an expensive project. With so many changes so far, who knows where its going? :lol:  :lol:


I have actually collected some bits together for the original conversion, which I am now going to have to change for different items for the new plan.


I used to be indecisive, now i'm not so sure :D


This wont be a quickly built project, so please dont expect updates every week, although I will update as I go. :)

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Nice job with finding the info out on the car to the best you could anyway. I will put colour down to Son like Father ;) 

Anyway moving on ;) 

If you get this looking like that speedhunter car I think you will be following your son in the magazines look's amazing, and feel honored to be able to see the build just like the guys from Holland and see the car grow. 


I will just point out Us Mod's are working hard to get a project section just for you and Savage for these types of builds.


And already feels like Christmas waiting to see the car being built to the next stage :D 

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I agree with the wing and bodykit opinions you have buuut it does look like you would have a very individual motor when completed and not afraid to kick up its heels either 


It will be great to have all these great project threads in one place and we are hopeing that will be along in the very near future.


Going to enjoy following this one as well :)

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Loving the look of your old 4 door legacy , nice work fella

As for wide arch legacy's abw have just fattened up Damien Bradley's(700hp) time attack classic legacy and that looks sweet too.might be worth having a look at that for some bodywork inspiration (once you've got the mechanical side sorted) .I'd like to know a bit more about the twin turbo set up so will be keeping an eye on your build and probably pestering you with a few questions at a later date .

best of luck with the project and the new year


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I have seen Damien's wide arch work. It's absolutely superb. Not sure how that would convert to a later estate, but that's in the future after the mechanical work anyway.

My current twin turbo set up is just the standard GT-B set up. The vast majority of which will be coming out very soon.

Any questions you may have about it, please ask.

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Cheers chap , just mainly curiosity (at the moment lol) as to what other differences there is between single and twin .

Other than the obvious extra turbo ,up pipe , headers and vacuum .

things like do they run 2 actuators?

Does the intercooler have two entries ? (Or is there some sort of 2 into 1 plenum prior to the core)

Is the sump , oil pick up ect... the same as single ? (Or are they different like the twin scroll)

Heads are they the same (if not what's the difference)

Does the twin set up use any extra sensors / solenoids .

And thats just off the top of my head I bet you wish you hadn't said"ask away" now :-D

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The off side head is the same as the Impreza turbo. The offside is also the same except for having oil feeds at the rear for the other turbo. The oil galleries are present on the single turbo heads, but are blocked off.


Where as an impreza has a two port solenoid on the offside suspension turret. The twin turbo Legacy has a solenoid box. A vastly over complicated vacuum powered system that was conceived by the devil himself. The vacuum system has a tank in the nearside inner wing which stores vacuum. The solenoid box is a rats nest of vacuum hose and solenoids. These control all aspects of the twin turbo system.


The intercooler has two separate feeds, one from the primary and one from the secondary.


The sump and pick up is the same as Impreza. Medchanically, the heads are the same, depending which model the Legacy heads come from. GTB are shims over buckets and GT are Shims under buckets.


The twin set up has no additional sensors but plenty of solenoids in that box.


I will try and find some pictures. If not, I will take some when I remove mine.

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Thanks for that tlag

I know a little bit about classic impreza's even then only really v1 to v4, but that's only what I've either had to research or come across while fettling mine .

don't go outta your way for the pics bud (I'm in no rush just curious) saying that once you do start to pull the motor appart .....

I wouldn't mind a pic of the exhaust manifold/upipe set up and one of the turbo outlet / intercooler pipework ;-)

thanks again


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  • 1 month later...

As promised. Next update time :)

First some info before news of the work.

I've managed to obtain the rotated up and down pipes required to cope with the GT35. I still need an exhaust manifold to suit and a wastegate.

I have now decided to do this build in phases.

In the first phase, I will build the long motor and configure it to run a single TD series turbo with standard pipework.

Second phase, once the I'm happy with the motor pulling good and strong, I will pull the pipework and turbo off and fit the rotated pipes and the GT35.

Whatever I do from here on in, I will need to have the ecu sent away and an ESL board fitting to allow mapping. It will come back from ESL with a base map which will simply allow the car to run off boost. It can then be mapped for the TD series turbo and later, the map can be tweeted for the GT.

Doing it this way is a win win situation.

It means I get the car on the road this spring, all things being equal. It also gives me time to run the engine without putting excess strain on it from the start. It also gives me more time to find the right parts at the right price.

So, onwards to today's work. :)

Pulled the EJ25 block out of storage and mounted it on the engine stand. It's still wrapped up to protect it for now though.


For the eagle eyed amongst you, the black crank is visible which can only mean one thing. It's a nitrided item :)


Next, I unwrapped the heads to be stripped down. I needed to remove everything from them so that they can be sent to the machine shop, so here's the first valve coming out.


Here's a shot of the mating face of the head, as it is now.


So, the next steps will be done from the comfort of the living room. Ordering bits :)

I need to order some forged pistons. The block I have has the original subaru ones in, but I'm reliably informed that these particular ones are about at there limits at 350bhp.

Once I have made the decision on which pistons, I can then work out which thickness of head gasket to get. Once I have the head gaskets, the heads will go the machine shop and the heads will be machined to suit the block, all internal sharp edges you can see in the picture will be feathered and smoothed to avoid hotspots and then the heads wil be skimmed, polished and ported.

Oh, yeah, I think I forgot to mention. This will be a 2.5 bottom end with 2.0 heads, which is why they need so much machine work.

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been looking forward to a update on this thread   B)


are you going to get the bores " pinned" on the 2.5 block or will the scd be ok for your target power ?


what injectors are you intending to use to run it in ? as I used the standard ones that were in my uk turbo (380cc) which max out at 300 hp so that kept things simple for the base running in map ;)


 then the day before the td remap i fitted a fpr and some nissmo 555cc injectors which I'd had flowed by mark at lateral as there good for just over 400 which ample for the td05 on a 2ltr running a exedy stage 1 clutch

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The standard legacy injectors are 440 which should be ok for the base map. I will need larger ones for the mapping session though. I already have a higher spec fuel pump and am expecting to need a swirl pot/extra pumps when I go to second phase. We'll have to see.

It's not that easy finding larger side feed injectors. Converting to top feed may be the way to go, as well as parallel fuel rails. especially as I already have some freshly flowed 660's

The SCD should be good for my aims. The problem may be that that my aims get bigger eventually, but I'll cross that bridge much later on :)

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Yeah I like seeing something outta the ordinary and learning a few things along the way.

Tlag how will you overcome the single turbo from twin turbo loom and ecu differences ?

Or is it just a case of swapping the ecu / engine loom from a single turbo version and swapping that devils box full of solenoids for a 3port

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The twin turbo vac system is way over complicated. The simple way is to simply rip it all out and instal the tiny vac system from an Impreza.

The twin turbo loom can be very simply converted to single turbo by changing four wires at the ecu. (I have a friendly guru with more knowledge than me on that)

The ecu I already have is one that can be readily converted by ESL so that's not a problem.

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Living room time complete. :)

Orders placed so I just have to wait for the post for the next few days to see what turns up. Then I can get the heads off to the machine shop. Ooh, getting exciting now

To get this moving along, I have ordered some Mahle powerpak pistons, which come with pins and rings. Cosworth head gaskets and ARP head bolt set.

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