F30 BMW 328i F20 128i N20 Turbo Back Aftermarket Performance Exhaust Tuning

How tunable is the new BMW N20 inline 4-cylinder Twin Power Turbo Engine? How to get the most power output from the BMW N20 Twin Scroll Turbo inline 4 Cylinder? The answer is simple, a turbo-back exhaust and a tune.


The F30 BMW 328i, F10 528i, z4 Sdrive 28i, BMW X3 28i, among other BMW vehicles share this amazing N20 engine. The N20 4 Cylinder engine replaced the outgoing, less powerful, but more rev happy inline 3.0L 6-cylinder engine, that true enthusiasts will absolutely miss.

BMW downsized the displacement and the number of cylinders in the name of fuel efficiency, and to abide with new CAFE emissions regulations. The new N20 mill shows an increase in the low-end torque, decrease in weight, and lower C02 emissions. Even though we doubt that many enthusiasts will care too much about the later.

F30 BMW 328i F20 128i N20 Turbo Back Aftermarket Performance Exhaust Tuning

All of us BMW enthusiasts should be cheering the arrival of the N20 mill on the F30 3-series especially, simply because it is super easy and cheap to tune. Turbo charging opens up a huge door to improve the output of this entry-level engine. Just throw on some new downpipes with high-flow cats, add a cat-back exhaust and a tune. Even easier, just purchase a turbo-back exhaust. These minor bolt-on modifications could easily increase the F30’s N20 horse power figures to 300 hp and 300 lb-f of torque. Furthermore, we are positive that tuning companies will be able to stretch these figures up to 350 hp and 350 lb-ft of torque without compromising driveability and durability of this engine. These numbers are impossible to achieve in a naturally aspirated (N/A) engine without adding some type of forced induction or a larger cylinder bore, etc…

F30 BMW 328i F20 128i N20 Turbo Back Aftermarket Performance Exhaust Tuning
BMW claims that the 2.0-liter N20 engine takes back the F30 328i to its roots, way back to 1975 with the historical first 3 -series. That might be a long stretch, but turbo charging a 4 cylinder BMW makes the F30 328i that much more desirable by BMW enthusiasts because they are easy to tune.

The N20 engine displacement is exactly 1,997 cc, which is actually just shy of 2.0liters. In stock form it produces 240 hp @5,000 rpm and 260lb-ft of torque. The twin-scroll single turbo charger makes it possible for the max torque to develop at just 1,250 rpm without a noticeable turbo lag, which is pretty low in the rev band.

F30 BMW 328i F20 128i N20 Turbo Back Aftermarket Performance Exhaust Tuning
The N20 is very impressive, that it put down 233whp @5350rpm and 249 lb-ft @4450rpm. Yes, that is wheel horse power. That is ONLY 7hp less than what BMW is claiming at the flywheel, and ONLY 11lb-ft of torque at the wheels less than what BMW claims at the flywheel. BMW underrated their turbocharged engine, again, as they did with the N54 twin turbo 3.0L I6 and the N55 single twin scroll turbo 3.0L I6 that powers the F30 335i .

Our experience with the BMW N54 and N55 3.0L twin and single twin-scroll turbo charged systems, peak power usually plateaus at around mid 5K RPM, even if the redline is above the 5K mark at 7K rpm. The same with the N20 2.0L straight four. That prompts the driver to shift up through the gears at a lower rpm than usual to take advantage of the power band at lower to mid rpm range.

Many BMW enthusiasts will start modding their F30 N20 328i. The tough question that is on every tuners mind is which mods work best in optimizing the power of the N20 engine, without it blowing up because a couple of tuners with programming skills decided to write a crazy program that the N20 mill could not handle.
F30 BMW 328i F20 128i N20 Turbo Back Aftermarket Performance Exhaust Tuning
It’s best to stick with industry leaders in tuning, basically the companies that did fairly well in tuning the N55 and N44 engines without causing a disaster for the owners, and without the ECU throwing Check Engine Light (CEL), Malfunction Indicator Lamps (MIL). Or worse, “tuner codes” making it possible for dealers to identify that the engine has been messed around with, resulting in revoking the factory warranty on your new BMW. We wouldn’t want that to happen.

How do you reduce back-pressure in the F30 BMW N20 Engine?
Similarly to the turbocharged N54 and N55 engines that BMW produced prior to the N20, BMW’s stock downpipes result in a major bottleneck for exhaust flow in this section of the exhaust system. The result is increased back pressure.

What are the reasons behind such space confinement? BMW tries to achieve close to 50/50 weight distribution for optimum chassis balance on their cars, by moving the engine location further back behind the front axle. That usually creates limited space for bolt-on engine components around the firewall area, especially in the presence of a longitudinally oriented inline engine that powers the rear wheels. The new BMW N20 straight 4 cylinder engine in the F30 BMW 328i, 328xi, F20 BMW 128i, F10 528i, and Z4 Sdrive 28i is no exception. The same confinement is further increased with inline 6 cylinder engines that power rear wheel drive cars.

F30 BMW 328i F20 128i N20 Turbo Back Aftermarket Performance Exhaust Tuning

On the other hand, emissions control does not improve the situation. For emissions purposes, BMW designers decided to add built-in precats housed right after the turbo outlets. The result is an increase in exhaust back-pressure. But we have to give BMW credit, the design is innovative and genius in making use of the tight space available in the engine compartment. As a side effect of this design, the N20 turbo area, specifically the downpipe will retain excessive heat, resulting in less than full potential performance levels if driven hard, oh let’s say, on a track day. We wouldn’t want an F30 328i, F20 128i, F10 528i, or an E89 Z4 Sdrive 28i to go into limp mode on a track day.


On the other hand, installing an aftermarket down pipe, free-flowing cats, and a performance cat-back exhaust will free up an additional 20 hp at least. And that’s without software tuning. The key to get a major increase in performance from a turbo back exhaust is to maintain a full tube diameter throughout the bends from the turbo all the way back to the exit muffler. That could be achieved with high quality mandrel bent stainless steel exhaust tubing from one of the world’s most renounced performance exhaust manufacturers.

We have word that several BMW tuners are working on custom aftermarket performance exhaust components for the N20 engine. We will continue to monitor upcoming N20 tuning components and post them on this page as they rollout. So please bookmark this page and sign up for our RSS feed to stay updated with the latest details.

We suspect the following exhaust components will be developed for the N20 F30 BMW 3 Series, and N20 F20 BMW 1 Series:

Downpipes for the N20 F30 BMW 3 Series, and N20 F20 BMW 1 Series:

  • Active Autowerkes Signature down Pipes
  • aFe Mach Force XP Downpipe single turbo
  • Agency Power Downpipe
  • RD Sport Secondary Down Pipe Front
  • Supersprint Turbo Downpipe
  • Titek Catless Downpipe

Mid-pipe for the N20 F30 BMW 3 Series, and N20 F20 BMW 1 Series:

  • Meisterschaft complete or sectioned mid pipe
  • Eisenmann mid pipe

Cat –back exhaust for the N20 F30, F20, and E89:

  • Vishnu cat back
  • MXP Titanium cat-back
  • Milltek cat-back

F30 BMW 328i F20 128i N20 Turbo Back Aftermarket Performance Exhaust Tuning

If you have a few extra dollars laying around, put it to use. The 3 series and 1 series BMW’s deserves a gain in engine performance just because the underlying chassis is solid enough to handle the jump in performance without a huge sacrifice in drive-ability.

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4 Comments

  1. INGVALD says:

    I already had a custom stainless steel, metal catalyser made for my 2012 F10 528i N20. This would obviously also fit the F30 328i. I got a healthy improvement in responsiveness and also some extra horsepower (but I have not had it measured). Although barely visible even when you look under your car, the new metal catalyser is slimmer and looks like a perfect factory installation. The only problem I had so far is very minor vibration, mostly when I reverse the car (and I intend to have this inspected and adjusted for). Please note that I live outside the USA and will not be able to link directly to the place that made my catalyser.

    • Agreed, the same basic construction from the F10 N20 would essentially work for the F30 N20 because of the similarities in the exhaust flow from the same engine. Although physically the 528i is slightly longer than the 328i so the mounting points would be slightly off. On the other hand, if the only part you changed is the cat, then definitely have them check the area around catalytic converter, the heat shield, there might be slight interference as the engine vibrates at lower RPMs.

      Did the exhaust sound change a bit? It would be cool if you could take some pictures or a short video that you could share with others on the site.

      P.S: is your 528i an automatic or a manual?
      - Ray

  2. Sixteen78 says:

    N20 has lots of potential (coming from an Audi driver). I read somewhere that BMW just won an award for the N20 along with a few other engines.

  3. Supersprint says:

    Nice article! As we’re working on these cars right now, I wanted to give you a few info base on facts.
    At the moment we’ve worked on the Z4 28i and the F20 125i.The 1st has exactly the claimed power. We fitted a full exhaust system with a HJS metallic cat and we got 10hp more and a very healty torque increase, specially at low rpm. The sound is very good, except for the diesel-like noise from the engine bay, when the car is cold started.
    On the 125i we did the same kind of system. The car stock has 230hp, instead of the claimed 218! With the full system we got 240, but with less torque increase than the Z4.
    Also the downpipe is the same for the 125i, 328i and 32i, but it’s different for the Z4 and the F10 5 series.
    Next week we’ll have the 328i.