[CoralRed]

Hi All!

I’m in the planning stages of N54-swapping my 2011 auto e91. I got super lucky with the donor—- a 1-owner 2008 AW over Terra manual 335i w/108k miles.

My overall goal for the build is a car that is sorted and (as) reliable (as an n54 can be) but natural I’d like to boost the performance. Nothing crazy and I want to use quality parts. My Hp goal is somewhere around 400… let’s say somewhere between 375 and 450. During the build the usual N54 issue areas will be addressed and it’ll get walnut blasted.

I owned a 135 for 16 years so I’m very familiar with the platform but my car was all BMW parts so I’m pretty new to the n54 tuning scene.

My thoughts are:


-new turbos. Either BMW or RB (probably billets?)
-tune: MHD?
-intercooler?
-catted down pipes (VR?). My county does emissions testing so probably need the cats
-intake? My 135 had AFe that worked well for me.
-oil cooler?
-performance radiator?
-anything else I might be missing?


I’m in the process of doing some digging in my end as is the expert doing the build but wanted to get some thoughts from the n54 tuning community in case there’s something I’m not considering.


Thanks!

[oVeRdOsE.]

-new turbos. Either BMW or RB (probably billets?)

you can go OEM hybrid or RB.
If you have the budget single for sure, makes the car more reliable (if done correctly), less heat, better sound, less torque on low rpm so easier on the engine.
I mean, the engine will be out, this is a good ''while Im there''


-tune: MHD?

For your goals, yes 100%.

-intercooler?

This one can be put on hold and you can do some loggin to see if temps are fine with OEM. But always a good idea, a 5'' stepped will be enough. 7.5'' are too big for your goal

-catted down pipes (VR?). My county does emissions testing so probably need the cats

N54 likes downpipe, and some flash tune highly recommend this

-intake? My 135 had AFe that worked well for me.

intake and turbo inlet. Try to find one that still had the air duct.

-oil cooler?

on all tuned N54 yes, use OEM used, they work fine and you're sure it will fits.

-performance radiator?

on boosted TT always a good idea, but this is mainly for reliability than cooling performance. Since OEM-like always separate where the plastic plenum meet the metal rad.

-anything else I might be missing?

injectors, coils, sparkplug, latest HPFP, crank belt guard, metal pcv valve, catch can high side at least, water pump & thermostat if old; might be a good idea to add in the budget.
Transmission support are not the same if you want to keep the 6mt, a bit of fab there, nothing crazy.

no need for a LPFP for 450bhp.

[suspect]

Originally Posted by CoralRed

Hi All!

I’m in the planning stages of N54-swapping my 2011 auto e91. I got super lucky with the donor—- a 1-owner 2008 AW over Terra manual 335i w/108k miles.

My overall goal for the build is a car that is sorted and (as) reliable (as an n54 can be) but natural I’d like to boost the performance. Nothing crazy and I want to use quality parts. My Hp goal is somewhere around 400… let’s say somewhere between 375 and 450. During the build the usual N54 issue areas will be addressed and it’ll get walnut blasted.

I owned a 135 for 16 years so I’m very familiar with the platform but my car was all BMW parts so I’m pretty new to the n54 tuning scene.

My thoughts are:


-new turbos. Either BMW or RB (probably billets?)
-tune: MHD?
-intercooler?
-catted down pipes (VR?). My county does emissions testing so probably need the cats
-intake? My 135 had AFe that worked well for me.
-oil cooler?
-performance radiator?
-anything else I might be missing?


I’m in the process of doing some digging in my end and the shop doing the build is a huge help as well but wanted to get some thoughts from the n54 tuning community.


Thanks!

MHD stage1+ 98RON(93OCT) with 5.5" intercooler will give you 400bhp.

[lookalikehuuh]

Keep in mind that High flow catted DPs won't be able to pass an emissions test. You will get codes for catalyst below efficiency even with the best catted DPs. In other words, when its time for emissions test you will have to swap the in the original cats before the car will pass an emissions test.

I personally use the VRSF High flow catted DPs because I hate the smell that cars with no cats have, plus I don't need another reason for the police to pull me over.

[oVeRdOsE.]

Originally Posted by lookalikehuuh

Keep in mind that High flow catted DPs won't be able to pass an emissions test. You will get codes for catalyst below efficiency even with the best catted DPs. In other words, when its time for emissions test you will have to swap the in the original cats before the car will pass an emissions test.

I personally use the VRSF High flow catted DPs because I hate the smell that cars with no cats have, plus I don't need another reason for the police to pull me over.

is that stringent?

swapping downpipe for emission is not an easy job !

maybe go single exit (for that L6 sound) and flange 1 pre cat where it's easy to swap, and daily the car with a test pipe.

[CoralRed]

Thanks all, for your thoughts so far!

For the turbos: does anyone make a hybrid OEM set up? I hadn’t thought about doing a single (I thought they were for high HP applications?) but I’d probably like to leave it closer to stock. Plus, I’d probably rather spend the $$$ elsewhere… I.e suspension, interior swap. But I’ll check it out!

For the downpipes…. I definitely wasn’t aware the catted pipes may still pose an issue… I don’t want to have to change them out. Texas DOES allow for one monitor to not be active so that may be an out…

[oVeRdOsE.]

if you go on speedtech website, you'll see tons of single turbo choice, and some of them is to keep the power close to stock.

Depending on what you do, and your engine mileage, this can be debatable going small single turbo is it's more or less expensive than upgraded twins on long run.

everything is simplier, you even can get some turbo no coolant lines. Youll have only 2 O2 sensor instead of 4.
The wastegate will be external, so bye the rattle.
Intake is simpler, you don't gave intakes anymore
No more oem vacuum lines, in fact you reduce a lot the vacuum line qty.
Less heat.
Ill go for a small bottom mount.
A lot of space for future improvement. Power is a drug, and knowing those engine can put down shit ton of power, swapping a turbo is a somewhat easy upgrade.

up to you, going into a such huge project, you might rethink. OEM suspension on those E90 are already very very good. BMW nailed it.


For hybrid TT, back in the days there was a kit that you can DIY, you mainly upgrade the cold side and wheel, keeping the hot side the same and change the waste gate actuator.

[lookalikehuuh]

Originally Posted by oVeRdOsE.

is that stringent?

swapping downpipe for emission is not an easy job !

maybe go single exit (for that L6 sound) and flange 1 pre cat where it's easy to swap, and daily the car with a test pipe.

Oh yeah its crazy how stringent the catalyst system can be. My car has zero smell, zero soot or anything, but the car will trigger the catalyst below efficiency code within 100 miles if I remove MHD from the car.

[CoralRed]

Thanks all!!