FA headers on the Unicorn

I bought a set of FA headers off a 2015+ WRX to test on my car when I had the turbo out for reasons.

What I have found is the exhaust outlets appear to be a little bigger. The general shape of the gasket is the same other than the center bolt being offset slightly. I don't know if that was for an engineering reason or to force a new part number for the gaskets.

The big reason this won't work out though is because the FA headers are wider. I don't recall en exact number but it was more than a quarter inch.

I'm not saying no one could bend them to force them to work but I wouldn't trust anything built like that. Looks like we are stuck with custom headers for the foreseeable future.

https://imgur.com/gallery/adjVSBv/comment/1718423063

EDIT: Added labels for clarity

EJ25 vf54 head side exhaust flange diameter 1.48 inches

FA20 head side exhaust flange diameter 1.636 inches

EJ25 vf54 head side exhaust flange hole spacing 2.4 inches

FA20 head side exhaust flange hole spacing 2.4 inches

EJ25 vf54 top FA20 bottom

EJ25 vf54 top FA20 bottom Note: I lined up the left side with a stud that came out of the engine with the nut. The right side holes were over half way covered about 1/4 inch overlap.

EJ25 vf54 head side exhaust flange with EJ25 vf54 gasket

FA20 head side exhaust flange with EJ25 vf54 gasket

I'd like to add to this thread , I will be attempting to file down the bolt holes in the FA20 header and then bend the pipes a bit if required.

I have an ej25 with a blown bearing for test fit purposes.

I still want to make this work because killerb advised they could sell me one of their T3/t4 flange adapters to suit the header:

https://forums.nasioc.com/forums/showthread.php?p=46105546#post46105546

Aside from actually fitting to the block you should consider the smaller size runners are going to hamper the flow out of the cylinder and probably create more backpressure than the stock header. The FA20 header is designed for an engine moving half a liter less air.

Why not see if an aftermarket header like ETS would improve on our engine vs trying to use another OEM part that will ultimately be more restrictive.

The FA20 runners are bigger inner diameter as per the OP.

I'm going to modify what I have in front of me, then if everything is going well, perform the same modification to an aftermarket header.

For testing, I think the stock one is a good start, considering the header and turbo (mgt2259s) cost me less than $400 AUD.

Aside from actually fitting to the block you should consider the smaller size runners are going to hamper the flow out of the cylinder and probably create more backpressure than the stock header. The FA20 header is designed for an engine moving half a liter less air.

 

Why not see if an aftermarket header like ETS would improve on our engine vs trying to use another OEM part that will ultimately be more restrictive.

FA headers have the larger diameter holes and less restrictive sections in the pipe. Just based on looks it'll have better flow. It'll be a significant amount of fab work to make them fit and there will be significant benefit to porting the exhaust ports on the heads to match where the new headers end up lining up.

ETS doesn't make the EJ low center mount turbo headers any more and destroyed the jig. I emailed them. They aren't even interested in a group buy. I have only found one set of ETS headers not installed and the owner was still planning on using them so he didn't want to sell.

If moral hazard can get these to work with a good write up guide and minimal modification it'll mean the FA header and turbo kits should work for this platform. Charge pipes would potentially line up as well as J pipes. We already know the intercoolers and most cat-back exhaust components fit.

Nevermind I had to edit this, I was thinking the grey header was the fa20 and the other was ours.

I added picture comments after I saw your post. There are comments on the imgur album but I posted the pictures individually so they would show in the thread.

Could you redrill center hole and elongate the two others to fit? 1/4" wider is only 1/8" on each side. The larger ports of the manifolds should line up with ours.

That being said what is the WRX manifolds going to buy us? I think the larger exhaust manifold is likely to cause a little more lag, but it could contribute to additional boost control issues if using the VF54 (I am not even sure those bolt up)

Are there more turbo options for the WRX?

Are there more turbo options for the WRX?

Yeah for sure. And if you could swap the assembly, then some related parts would be closer to bolt on, such as an FMIC.

It buys you about 1000 options for different turbos instead of just one. It potentially buys you WRX J pipes, aftermarket headers and twin scroll turbo options, external waste gates, WRX charge pipes, WRX turbo intakes, and pretty much anything else we would want to try to cram in there.

If the engine shapes and sizes are about the same in theory you could fabricated brackets where needed and get a whole host of other stuff to fit for aftermarket upgrades without going full custom.

It buys you about 1000 options for different turbos instead of just one. It potentially buys you WRX J pipes, aftermarket headers and twin scroll turbo options, external waste gates, WRX charge pipes, WRX turbo intakes, and pretty much anything else we would want to try to cram in there....

Yes to all of these things! honestly if its down to squashing the thing down by a 1/4" and making a few holes into slots i'd think that it should work pretty well. did you do a comparison of where the 2 hold the turbo in relation to where it bolts to the heads?

Yes to all of these things! honestly if its down to squashing the thing down by a 1/4" and making a few holes into slots i'd think that it should work pretty well. did you do a comparison of where the 2 hold the turbo in relation to where it bolts to the heads?

The exhaust holes are centered on the 2 outer bolt holes on the flanges. It would seem to be on the inner studs were offset in a north south directions. The FA block is a little wider, most likely to accommodate the extra 7mm of stroke. Give the larger exhaust flange holes it should line up to cover and potentially seal. We just have to have someone brave enough to bolt things up and pressure test.

just spitballing, but if you squeeze the FA20 header a bit, wouldnt that change the angle of the flanges?

It would, but the question would be whether or not it would change enough to cause it to leak or if it would still be within the tolerances that a gasket could still seal.

It would, but the question would be whether or not it would change enough to cause it to leak or if it would still be within the tolerances that a gasket could still seal.

Its a MLS gasket, it is not going to have much a tolerance.

just spitballing, but if you squeeze the FA20 header a bit, wouldnt that change the angle of the flanges?

yes but it would pretty slight. that said it wouldn't be a simple turn it on its side and sit on procedure more of a bolt both sides to a plate and draw them together while applying some heat. with such a small difference tho you may be able to get away with slotting some holes and doing some careful porting to both the head and manifold since there is clearly a good amount of extra space between the ID of the gasket and the ID of the pipe

I hope that you also have looked at this thread: https://legacygt.com/forums/showthread.php/eleguas-badass-br9-wagon-241754.html

It might give you some bad ideas though.

But also realize that a diameter change from the head to the header can actually result in worse flow than a smooth transition so if you are increasing the diameter you'd have to mod the cylinder head too in order to get a smooth transition to the larger diameter.

I hope that you also have looked at this thread: https://legacygt.com/forums/showthread.php/eleguas-badass-br9-wagon-241754.html

 

 

It might give you some bad ideas though.

 

 

But also realize that a diameter change from the head to the header can actually result in worse flow than a smooth transition so if you are increasing the diameter you'd have to mod the cylinder head too in order to get a smooth transition to the larger diameter.

That why I suggested porting the exhaust outlets on the heads.

Alright so I had time today to slot the holes and test fit again to the ej25 block I have laying around.

Looks good, did not need any bending or any extra force when bolting the header to the block. Only had to slot the two inner bolt holes (2 out of 6).

I see no visible gaps even without using gaskets.

Obviously if buying aftermarket headers I wouldn't recommend using a grinder to make slots, just take it to a machine shop to have the bolt holes turned into ovals.

My plan over the next week is find a day to actually swap my VF54 for this MGT2259s and header, then to start the car up. Hoping to bolt up a lot of the 2015+ WRX exhaust also.

Just wanted to update with the progress I've made today.

Ran into 3 small issues:

1. The oil feed hard line needed to be swapped with the one from the VF54 because of the different fitting on the end. Also had to bend the VF54 hard line a bit to route around the wastegate actuator.

2. Cut a piece of coolant hard pipe from the VF54 to use as one of the coolant pipes takes a longer path on the mgt2259s. Could have probably just used a new longer hose but I decided to go with this option today.

3. I used a longer oil filter up until now ( FB25 forester style), now I will either need to rig up an external oil filter or find a smaller one as the oil filter now is fouling on the compressor outlet. Alternatively might be able to just clock the compressor housing, will remove the filter tomorrow and see how much room I am left with.

3. I used a longer oil filter up until now ( FB25 forester style), now I will either need to rig up an external oil filter or find a smaller one as the oil filter now is fouling on the compressor outlet. Alternatively might be able to just clock the compressor housing, will remove the filter tomorrow and see how much room I am left with.

NICE! the standard short filter is almost half the length of the longer one so it should give you 2 inches or so

I was hoping that the shorter filter would do the trick but the compressor housing still touched the plastic timing cover.

So yesterday I took the time to clock the compressor housing. Will test fit again this weekend and update with pics and progress.