E90 335i N54 Project Car
Here it is - our first in-house N54 project car. It's about time we dove into the crowded N54 tuning market and see what the N54 is all about. We are not newbs in turbo performance and technology - we have more experience with the N20 turbo 328i than any other race team and we now run an M4 GT4 S55 turbo in IMSA racing. We built a N54 135i for One Lap of America in 2008. On the street side, BimmerWorld prez James Clay famously owns a turbo S52-powered E36 wagon and our sales leader Phil has a turbo S50 E36 M3. We wanted to see what it would take to own and track an N54-powered car.
Finding a RWD stick shift that has not been neglected or abused is not as easy as we hoped. The N54 was only available in the E9X platform for just a few model years - 2007-2010. Engine specs were identical in all years so it didn't really matter which year to buy (although 2007 model year has limited coding and programming options). It really came down getting a RWD stick shift that was clean, unmodified, and strong. We desired the minimal amount of work to bring it up to original peak condition before the real tuning started. We searched for a year before landing this 2010 E90 335i manual RWD sedan with just 74,000 miles.
Project 335i First Photo Shoot
Project 335i July 2018
Every used car is going to have speed bumps before it can be ready for the track. Ours was no different, even with a careful pre-purchase inspection. We knew going in that it would probably need fluids changed, air filter, spark plugs, coils, and probably a walnut blast for carbon buildup. But we had a few additional hiccups that delayed getting our car trackworthy.
Almost right away we had clutch slippage. It would appear one or more of the previous owners didn’t clutch smoothly or enjoyed too many drifts. Or both. Our project had barely got off the ground we already had a major overhaul to complete. See below for more on our Clutch Masters 850 upgrade.
The needs for a track car vary from one model to another. What may be bulletproof on M3 is a common weak point on a 330ci. No two builds are ever the same, even within the same model. Nearly all of BimmerWorld’s previous track cars have been naturally-aspirated cars (with a few personal exceptions like James’ turbo S52 E36 wagon). So approaching a 335i N54 track car required a fresh approach. We can't say that it's typical for ownership but we feel that many of our customers are going through a lot of the same things and can empathize with our experiences. We won't say the N54 is incorrigible (can't be tamed) but it does take commitment and perseverance (and deep pockets). Read on for own experiences building an N54 for the track...
335i Track Car Build
Here’s our take on building a 335i N54 for the track. Take a hard honest look at your car and decide what its true needs are. Racy brakes or fat rubber won’t matter much when you’re limping along due to overheating. We’ve tried to put these preparations into order of most-to-least important but they are not set in stone. Vehicle condition and needs vary.
Assuming the rest of the car is ready for track speeds, the most important area to focus on is safety. Even in stock form the car is too fast and too heavy for street or high performance pads. What the 335i needs for advanced track driving is a set of true racing brake pads that have enough stopping power to slow the heavy car down from high speeds. The rest of the system should be capable for most drivers up to an advanced level during 15-20 minute lapping sessions. The stock rotors are a decent size and will do a good job of taking the heat. Brake lines and premium DOT4 fluid will also give you a reliably solid pedal for consistent laps.
For some drivers who are exceeding the capabilities of the stock brakes there are other options. A Big Brake Kit will have larger rotors and a stronger, stiffer caliper. The caliper rigidity makes a big difference in brake feel as well as torque. It lets you brake later and deeper into a corner. The larger rotor does a better job of absorbing and dissipating heat which lets you out-brake the stock system more consistently. We put a set of StopTech ST60 brakes on our car, see below for the details.
Also remember that brakes should be matched to your selected tire type, just like suspension and alignment settings. The grip potential of a slick tire is largely lost when weak brakes are applied (you'll burn through the brakes faster than you will the tires). And the converse is true - ultra strong brakes will quickly reveal the deficiencies of slippery tires. A balanced approach to car building should always be used.
There are plenty of things that can ruin an N54 track day but high temps are at the top. The engine bay is so compact and with so little moving air that heat soak in the fluid and air systems is a real concern. Power output is reduced when water temp reaches 245°F or oil temp reaches 304°F. These are low thresholds for track use, which we routinely hit in our initial events. Since this is a protective measure in the engine electronics we don’t really want to change or remove these limits through software. Upgrading the system hardware instead will reduce temperatures across the board and keep temps well below the danger zone.
Make sure your water pump and thermostat are not more than 70,000 miles old. The water pump is electric and the circuits inside fail before any mechanical issues appear. The water pump dies with little or zero warning so before planning an expensive track weekend, have your water pump and thermostat overhauled.
Upgrade the engine oil cooler. Oil temps always run hot on the track. Also use a really high quality oil that is engineered for high temps.
Upgrade the engine water radiator. Our goal here is more capacity to reduce heat soak and get more surface area for more cooling.
Install a lower temp thermostat. The thermostat is electronically controlled but still operates like a traditional thermostat. At a certain temperature the valve inside opens and allows hot coolant to flow into the radiators. A thermostat with a lower activating temp will circulate more fluid.
Again, we know the temperature thresholds can be changed in the software. But BMW put them there for a reason (and it’s not to ruin the fun). Our experience tells us that if you modify or remove the limit, it just causes a failure somewhere else. We haven’t experimented with what the next system failure would be because all of our hardware upgrades lowered temps by degrees!
Ignition - Coils & Plugs
Ignition coils are right at the top of potential limp mode causes along with high temps. Is there any solution to chronic ignition coil failures? Not really. The best you can hope for is to correct any issues that may be the root cause of repeated coil failures, such as valve cover oil leaks. There is no preventative mileage recommendation for coil maintenance. They either work of they don’t. It’s best to have 1, 3, or even 6 spare coils handy in case you need to replace one on the fly.
Spark plugs should be changed every 40,000 miles per BMW. It’s not a bad idea to go one step colder on a spark plug. With the added heat of high RPM running engine knock is more likely to happen with stock plugs. Engine knock (ping) will cause the ECU to reduce power.
Due to a number of deficiencies in the N54, carbon and oil sludge builds up on the backs of the intake valves, cylinder head, and intake manifold. As the carbon residue thickens and hardens it prevents proper valve operation and affects air flow and fuel quality. This leads to all sorts of running and drivability issues. Cleaning out the carbon has huge benefits on track and street N54s. We were amazed at how much better the car ran after cleaning ours. From a track perspective the carbon can lead to misfires and engine pinging.
We also opted to replace our stock diverter valves with a traditional blow-off valve. For emissions purposes BMW used two diverter valves to redirect charged intake air back to the turbos when you lift off the gas. This keeps the air contained in the engine instead of releasing it into the air. But they are made from plastic and may no longer seal tightly when closed, leading to lost boost pressure (boost leaks). We used a TiAL blow-off valve in our favorite blue hue. The BOV is rated for a lot more power than the diverter valves and restores the familiar turbo “whoosh” sound missing from the stock system.
Just as overheating fluid can affect performance so can overheated air. We plan on turning up the boost on this car and that means more heat. Hotter air is not ideal for horsepower and the computer will dial back power if intake temperatures are too high. A larger and more efficient intercooler will help lower air temps as much as possible. We partnered again with CSF of California to develop a new stepped intercooler for the 335i. The stepped design greatly increases surface area and fits with only small trimming of the undertray.
Rubber suspension bushings degrade with time and exposure to temperatures and chemicals. Our car’s front thrust arm bushings were shot when they car arrived, resulting in vague and loose steering feel. We installed a set of our sealed monoball bushings to add precision and durability to that spot. At the same time we installed the stock M3 lower control arms to get the better inside bearing and a bit more negative camber. Both of these are suitable for street use and do not add any more noise, vibration, or harshness.
For the rear, there are no major issues to address right away. One common upgrade for a lot of drivers is a better subframe mount. We chose to wait on the mounts but installed Powerflex stiffening inserts for the time being. We may avoid M3 subframe mounts since they are not a perfect fit and go straight to solid aluminum mounts.
Rear Toe Arms
One minor issue is with the rear alignment and tire clearance. The stock suspension only has a limited adjustment range for camber and toe and we wanted to be able to adjust them further. We installed our aluminum race arms that give plenty of adjustment but are also lighter and use a solid Heim joint instead of squishy rubber. Changing the alignment also plays a factor in tire clearance. Our car is a facelift design (2009-2011 E90 LCI) and has less rear body clearance than the 2006-2008 E90 sedan and the E92 coupes. So it’s more challenging to fit wider rubber and making alignment changes necessary for clearance. More on this below.
The fact that this falls so low down on the list makes it clear how important regular maintenance is on the N54. With so much torque available, especially when tuned, grip under acceleration is vital. A limited slip gets you out of corners faster with less wheelspin. It also lets you get into the power sooner rather than waiting for the best (safest) moment to pour on the boost. We have yet to install a LSD into our 335i and are currently evaluating several options.
Jumping up in tire size is an obvious track upgrade - wider front tires to balance out understeer and more grip from wider rear tires. We left wheels and tires to last on this list because everything ahead of it is so important. We also believe the driver should understand WHY more grip is needed and not just jump up into a faster spec.
As mentioned above the LCI E90 has less wheel clearance in the rear than any other E9X model. The rear quarters are “pinched” compared to others. Our ideal setup would be 18x9.5” wheels in front and rear so we can run a 275 width tire. But that width is a bit too wide for the LCI rear fender and rubs on the outside. It can almost clear by cranking in the rear camber but that is not the best fix. We trimmed and rolled the inside of the fender lip and that gave us a little more room. A pre-LCI E90 sedan and E92 coupes do not have the clearance issue and is what we recommend. For the LCI sedan a 9.0” ET31 is an easy fit but restricts us to 255-265 width tires. For the time being we are running the 9.5”/275mm set using our forged TA16 wheels.
Bonus Items & Fun Stuff
With all the serious prep work taken care of we could settle in and start tuning our N54 for more power and changing out the suspension for better handling.
Just days into our ownership we noticed our car had a clutch issue. On hard launches the engine revved but the car stayed put. Either the previous owner enjoyed launching the car more than we realized or it was abused to the point of no return. This was now an important turning point in our 335i's journey and it was barely a week into our ownership. We didn't plan on doing a clutch until much later so our clutch choice had to match our future plans for the car as well as who and what type of driving it will see. A factory clutch was not even considered because it would slip and overheat with repeated hard use.
We've been using Clutch Masters on our race and project cars for years and they were a natural choice for this project. We considered their FX350 kit that has great holding ability and is driver friendly. But we ultimately chose the Twin Disc FX850 kit that uses two smaller discs and a solid pressure plate design.
The FX850 includes two 8.5" clutch discs - a Kevlar that holds up to extreme heat and a Fibertough hybrid material that is easy to use. But what really sealed the deal for us was the pressure plate. Instead of a traditional pressure plate with weak drive straps and rivets the Twin Disc uses a machined aluminum cover with grade 10.9 bolts and no drive straps. This kit is also lighter than any factory or sport clutch, even with the included flywheel. There's really nothing to fail on this clutch even if it's abused. These same clutch components are used in drag racing muscle cars making 900hp. Our little 3.0-liter 6 cylinder won't give it any problems, even when we're pushing 700hp.
The only question mark of this kit was how would it behave on a normal street car. Given the Kevlar disc's touchy engagement would this clutch be too annoying to use on a daily driver? And how would the aluminum flywheel and solid pressure plate be for noise? The driver has some adjustment period when first taking the wheel. The engine revs quicker than you expect which requires you to re-learn rev matching. And the Kevlar disc doesn't want to be smooth, although it's offset by the Fibertough disc's 'softer' material. With a half-hour of use you will be launching and rev-matching just as before. We're quite sure we won't ever have to think about this clutch ever again.
Update: we now have 7 track days as well as many road trips and dyno runs and the clutch feels just as strong as Day 1. Multiple people have driven it on the street and the track and they don't feel intimidated by its impressive specs. We've made the N54 clutch bulletproof!
No BimmerWorld Project Car would be complete with extensive suspension tuning. Given the track-focused nature of this project we didn’t hesitate to go straight to MCS dampers and Eibach race springs. Coil overs are more advantageous for track use for a number of reasons:
+ customize spring rates, pick a spring that best suits your requirements
+ most have adjustable damper rates that work with a range of springs and suspension control
+ many coil overs come with adjustable camber plates to set a better alignment
+ set ride height and corner balance
The MCS dampers are true motorsport-grade shocks with adjustable rates. We have extensive experience with these shocks on a lot of different vehicles. For our intended use the MCS was our top option. We spec'd our kit with Eibach 2.25" race springs. We chose rates that will be capable on the track and still somewhat comfortable on the street (depending on your definition). Ultimately we would prefer a stiffer spring for track use but a dual-purpose car always compromises between speed and comfort. Ground Control camber plates top off the front strut assembly.
Contrary to perceptions, bearings do wear on non-M cars as well. It’s not just S54 and S65 engines that see bearing wear. Our N54 had 83,000 miles when we decided to pull the oil pan and check the bearings. We didn’t have any indication or hint of the wear so we were shocked to find significant wear on three out of six cylinders. And it makes sense when you think about the stresses and forces being applied to bearings of a high-output turbo engine. We hadn’t heard of “early” bearing wear on N54 engine previously but now we were looking at it first hand. A new set of factory bearings with WPC treatment were installed.
Just like any other area of the car, braking performance can and should be upgraded for regular serious track use. As we detailed above the above-average driver will get by with an upgrade to racing pads, better brake fluid, and stainless steel lines. But to get any better braking will require a different caliper and larger rotor. We chose a 6-piston StopTech 355mm system. This rotor is slightly larger and wider than stock rotors, which helps in managing heat from race pads. They also cool faster thanks to an aluminum hat and directional vaning. But the greatest improvement comes from the fixed caliper. The stock caliper slides on a pair of pins. The mounting method causes the caliper to flex as the brakes are applied. This is amplified by the single piston layout. It's like squeezing a tennis ball with just the fingers on your right hand. A fixed caliper is like squeezing the tennis ball with the entire palm of both hands. The force is greater in strength and equal to both sides. You can feel the difference in the pedal under extreme braking. The StopTech kit just gives you more stability and confidence that allows you to brake later and deeper into the corner.
Intake & Exhaust
As part of our ongoing product development we installed an Injen cold air intake and a MagnaFlow exhaust.
The N54 335i is so muffled from the factory with two turbos, four catalytic converters, a resonator, and a large muffler. We don't know why the engineers (or marketers) felt the need to silence the 335i so much. Not only would a MagnaFlow E90 exhaust waken the car up but it will save a bunch of weight as well. This is the MagnaFlow Sport system that removes the secondary cats and center resonator. The rear muffler is reduced to two small sport mufflers. This is a cut and clamp style system which requires removing the stock exhaust and cutting it just ahead of the original secondary cats. Removing these cats does not affect the check engine light and removing them also eliminates a potential blockage when they fail. Overall, we're very pleased with the Sport sound on the 335i. It has a great rumble at all RPM and when lifting off the throttle. Drone is more noticeable than the stock system but is only in a narrow RPM range.
Let the Tuning Begin!
300hp/300ft-lbs of torque should be plenty of power for most people. Until you get used to it or are being passed by X5’s with 450hp…. Tuning the N54 for more power is SO EASY that you only have to think of a power figure and it can happen. 400hp? 500hp? 600hp? Why not 1,000hp? Enthusiasts can’t wait to get their hands on it. It’s also starting to find its way into other non-BMW builds (240ZMW anyone?)
Products Chosen for our Project E90 335i N54
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