I’m starting to suspect my turbo on my S4 TII has gone bad, it doesn’t even reach 0 on the boost/vacuum gauge, and has a loud wailing siren noise any time the boost increases (again it just stays in a vacuum, never reaches zero but it will increase from the lowest -20 reading). So I’m debating just going the route of a BNR turbo, but I’m not totally 100% sure on what exactly I’m getting out of it, would they simply repair my faulty turbo and it would be making more power, and if that’s the case can I keep the stock ECU, IC, fuel injectors, etc.?

 

welcome to the board.

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the simple answer is no. they are upgrading the turbo in their build. the added power comes from bigger, more efficient wheels and housing (in the case of the compressor).

again, the simple answer is no. if you want to keep all that stuff, then just have the turbo rebuilt. in the event that there is damage that would require modifications, then you may or may not need to upgrade other things for the sake of the engine's safety, but you can cross that bridge if you end up there.

you can find out if they will do a simple rebuild for you. if not, then you can look elsewhere.

 

Might be silly to ask, but have you tested for boost leaks?

 

Honest question, Why would you need a updated injectors or a non stock ecu if you are using the BNR turbo? if the wastegate is set to the same 7psi but your charge air is cooler due to a more efficient compressor, add to that the ported wastegate work Brian does, couldn't that just bolt on the stock system? I get it if you ripped the catalytics off and have a big down pipe and such. In disclosure I did have a S5 turbo done by BNR, but it's part of a build on an '80 and I'm running a Haltech, so I'm not quite sure of the limitations of the stock ECU. I seem to recall reading the ECU map goes to 8psi, so if that is accurate I can't see where a BNR turbo would be an issue, unless you over-boost. So there is a thin margin.

 

Just fwiw, I’m running a panspeed s5 hybrid turbo (equivalent to a Bnr stage 3). I used to run it with rtek 1.7, apexi neo, 550cc primary, 720cc secondaries. I forget what boost level tbh.

now I’m on apexi power fc. 720cc primaries, 850cc secondaries, fmic, walbro 255lph rewired to relay, intake. 17 psi no problems. I forget what my injector duty cycle is.

just for a reference so you can see the potential in growing your build around an upgraded turbo.

 

Yeah, at first I thought it was a boost leak and after searching all over the engine bay, I found two hoses underneath the car unplugged and just routed new hoses in their place. The stock S shaped turbo inlet also had a really fat tear in it, so I made my own intake setup out of metal pipe and it was airtight, but I ended up not being able to use it since the S4 AFM needs to be 100% level to work, so I had to seal it up the stock one and put it back on. It was airtight now when I checked it, and as soon as I can get my hands on an S5 AFM I’m going to do away with the stock one and put my intake back on. But even though it’s airtight now, there wasn’t much of a difference. Still makes that loud siren noise every time the boost gauge moves a little bit.

 

in theory, you're right. it shouldn't be an issue if you plan to run stock boost on the BNR with stock parts. however, the turbo would also be moving more air at the same boost levels. how much more? i don't know, but i'm sure someone smarter than me could approximate it. i imagine the stock injectors can handle more air to a point, but at some point they will need to be upgraded because realistically, why would you upgrade the turbo to run stock boost? as for the ECU, i remember it being capable of going marginally over stock levels, but it does quit at some point. i wouldn't trust it.