[Wareham]

Ive been pondering the idea of fitting an E46 M3 engine with N54 based turbos into my E91.

There doesn't seem to be much info on the internet of doing this swap so I thought I would start a thread to discuss with more experienced people to see if this is possible. well, its possible with the right skills, but what's actually needed.

You're probably thinking why, well.. why not? there's the slight bump up in displacement, 8k rev limiter and to be honest I just like a challenge. a low boosted 3.2 M3, if built right, should produce some smooth reliable figures.

Now first off, I'm aware that the N54 based TD03 turbos will most probably run out of puff at 8k rpm, so I was thinking of a set of stage 2 TD04 framed turbos would be better suited for this engine. Flanges between the N54 and S54 probably aren't the same, doesn't matter. Upgraded turbos with a separate manifold would be my preference and either converting to tubular or if the runners aren't far off then machine a new flange with cutting and welding.

Compression is a obvious issue. It needs lowering, I know. How much is the question. The N54 engine runs a 10.2:1 compression ratio, these being proven to hold 18+ psi reliably makes me think that would be a good compression aim. I have seen a lot of forged pistons with 9.0:1 compression ratio, however..

CP-Carrillo seem to produce a set for the S54 with quite a big compression selection, including 10.0:1 and 10.5:1 interestingly. I can only find these on the US site and not in UK, hopefully a UK supplier would be able to get some but its not the end of the world having to order from US.

https://store.vacmotorsports.com/cp-...s54-p2042.aspx

My only other thought would be what gearbox to use. I am currently auto in my E91 and would like to stick to auto with paddle shift, so use the M3 SMG box or fabricate the bell housing to suit the 335i box or create an adaptor for the 335i gearbox? what is the better system? both auto with paddle shift so I think that's going to have to be down to personal preference..

Not sure if the M3 ecu is capable of reading boost pressure so don't know what boosted M3 people do, will look into that.

It would be interesting to hear other peoples thoughts on this, good or bad. I can't find a documented build thread online anywhere for this idea so why not give it a go? It is certainly a intriguing idea..

[Wareham]

Someone must have some info on this...

Has it been done before ?

[therealdb1]

Originally Posted by G.wareham

Someone must have some info on this...

Has it been done before ?

Doubt it as it doesn't make sense.

It is a whole load of work to achieve what?

The N54 is a more modern engine that is widely regarded as one of the best starting blocks to tune from and fits in the E9x easily. Bolt on a few goodies and achieve 500 hp without trying too hard. I read somewhere (probably some blog from the USA) that there were claims of over 800 hp and there were issues with the DME having an 8200 rev limit.

[hassmaschine]

S54 turbo builds have been done many times in the past - look up Horsepower Freaks. The irony is turbo S54s (and S38s) piss all over any N54. But it won't be cheap, of course. I doubt you would want to use any parts off an N54. Basically none of it would bolt up or be optimized.

One difficult thing will be making the earlier electronics work in an E90. MSS54 uses CAN11h, the E90 uses BN2000 - they are not compatible. Maybe you could make some sort of bridge between the two to convert messages. Or use MSS70 (set up for BN2000), but most of the S54 tuning experience revolves around MSS54. You will almost certainly have to delete EWS.

It would seem to be a better goal would just to get a well tuned S54 to run N/A in an E91 or some other car (a difficult enough proposition), but it's going to be so much heavier than the M3 it came from, I'm not sure it wouldn't be better to just buy an M3 instead.

[Wareham]

Originally Posted by therealdb1

Doubt it as it doesn't make sense.

It is a whole load of work to achieve what?

The N54 is a more modern engine that is widely regarded as one of the best starting blocks to tune from and fits in the E9x easily. Bolt on a few goodies and achieve 500 hp without trying too hard. I read somewhere (probably some blog from the USA) that there were claims of over 800 hp and there were issues with the DME having an 8200 rev limit.

Yes I see your point completely, but I had just thought of the idea as more of a challenge. It doesn’t sound like many have done this if any..

Thinking about it though, it would be quite an accomplishment.

With the M3 engine being older, it still produces more than a stock 335i. So running low boost on twins my theory is that it would make good reliable power.

It would be a mix of older M3 engine with the newer M3 style forced induction, they must of done it for a reason

[Wareham]

Originally Posted by hassmaschine

S54 turbo builds have been done many times in the past - look up Horsepower Freaks. The irony is turbo S54s (and S38s) piss all over any N54. But it won't be cheap, of course. I doubt you would want to use any parts off an N54. Basically none of it would bolt up or be optimized.

One difficult thing will be making the earlier electronics work in an E90. MSS54 uses CAN11h, the E90 uses BN2000 - they are not compatible. Maybe you could make some sort of bridge between the two to convert messages. Or use MSS70 (set up for BN2000), but most of the S54 tuning experience revolves around MSS54. You will almost certainly have to delete EWS.

It would seem to be a better goal would just to get a well tuned S54 to run N/A in an E91 or some other car (a difficult enough proposition), but it's going to be so much heavier than the M3 it came from, I'm not sure it wouldn't be better to just buy an M3 instead.

I’ve found lots of single turbo S54 builds but not any twin turbo, especially the N54 based turbos.

From what I can gather researching, the N54 has a shorter stroke and longer rod length, surprisingly considering the S54 is a high revving engine.

My theory is that the S54 having a bigger stroke, would produce more torque lower down, therefore more exhaust gasses, resulting in better spool for turbos. Granted the turbos would have to be a suitable size to meet the requirements of where the power delivery would need to be.

[hassmaschine]

Twin turbo, maybe not - but I really doubt the N54 turbos would be very useful for the S54 anyway. Maybe, maybe not - better get comfortable looking at compressor maps.

Keeping in mind the S54 makes more power N/A than the stock N54 does with those stock turbos.. I think they will be too small.

[Wareham]

Yes, I agree they will be too small. They will no doubt run out of puff.

This is why I suggested about td04 framed, hybrid version of the N54 turbos