How To Build a 500hp, 11sec. N54 335xi for less than $1,500

There were believers, doubters, and some people who were just downright confused when we wrote our “How to give your N54 BMW 500hp for $1,500” article.  This follow-up article is for all of you, as we show exactly how we took a stock 300hp N54 335xi and turned it into a 500hp beast running 11.9@116mph in the ¼ mile.  This was all achieved on the stock turbochargers, by following the advice given in our original article.

THE PROJECT CAR

Our project car started out as an 09 E92 335xi with 62k miles, equipped with the infamous N54 engine and BMW’s AWD xDrive system.  Straight off the dealership lot this 335xi came in 100% stock form. All of the original equipment was in place and from the look of it, no modifications were ever installed on this particular 335xi.  It had no mechanical issues, no CEL, no rough idle, it was holding boost, and driving exactly how you would expect a decently maintained N54 should.

BASELINE DYNO RESULTS

Before installing the ARM FBO Kit we wanted to get baseline runs to see what our 335xi was putting down in stock form.  During our initial dyno session the 100% stock N54 put down 237awhp/280awtq, not remarkable by any means. Keeping in mind, this is the AWD version, making output slightly less than the standard RWD model.  If this were a standard 335i in RWD form, we’d expect to be making about 10% more power/torque straight out of the box with the stock N54, somewhere in the realm of 265whp/300wtq.

THE UPGRADES

After getting our baseline numbers, we were ready to begin installing our FBO N54 kit by following our 500hp article to the letter.  Below is a list of the exact upgrades we installed on our 335xi project car:

ARM 7” FMIC w/Hose Upgrade

ARM N54 3” Catless Downpipes (AWD Version)

ARM N54 Charge Pipe w/TiAL Q BOV

ARM N54 Dual Cone Intake

JB4 Tuner w/E30 Back-End Flash (BEF)

For a complete list of all ARM N54 upgrades CLICK HERE.

We also installed a custom M3 catback section purely for looks, since the rear-end of our 335xi was looking a bit out of place with the full M3 front-end conversion.  Power and performance-wise, the cat-back section alone offers little to no improvement. It was done solely for aesthetics which is a good thing, considering the sound was pretty unimpressive, not very loud or that good of a tone with the secondary catalysts in place.  With the secondary catalysts removed we would expect an increase in volume and change in sound from the exhaust.

INITIAL ROAD TESTING

The transformation from a stock N54 to a full bolt-on (FBO) N54 is monstrous to say the least.  For those of you going straight from a stock N54 to a FBO N54, you will be shockingly surprised at how hard it pulls!  Not only is the power increased of course, but the delivery of power is greatly improved.  Peak torque (over 450wtq) is available from 2,700rpm and 90% of the power is available all the way to 6,000rpm.  

With all of our new upgrades installed, we took our N54 335xi out for some test runs.  We ran it against SRT8’s, a gang of Mustang GT’s, a couple C7 Corvettes, even a Gen 1 Dodge Viper, coming out ahead against all of them.  But the N54 giveth, and the N54 taketh away. Before we could get it back on the dyno, we began to see persistent misfires.

DIAGNOSING MISFIRES

Misfires on the N54 are common after installing a tune of any type, much more so with an E85 blend, so we weren’t surprised when we began to see misfires on cylinders 1 and 4.  If you have the same issue as we did, you’ll find it is more than likely the coil pack(s).

In our case, to diagnose if it was indeed the coil packs that were failing we swapped the packs from the misfiring two cylinders with the ones from two well-functioning cylinders, 2 and 3.  Sure enough, we began getting misfires on cylinders 2 and 3, but not 1 and 4. With the cause accurately diagnosed as the coil packs we remedied it by ordering a full set of OEM replacement coil packs.  To save time in the future we went ahead and replaced the spark plugs as well since half the job is already done while installing the coil packs. If you don’t want to make the up front investment of 6 coil packs at a price of about $40 each up front, we suggest getting at least one extra, just in case another coil pack goes, you have it on-hand. This was the only additional maintenance we needed to perform above and beyond the initial oil change.

FBO RESULTS

Once we had our 335xi back up and running smoothly, we returned to the dyno.  This time putting down a massive 401awhp and 461awtq. That’s 164awhp and 181awtq more than stock!

While the peak gains are impressive, what really stands out is the “area under the curve” as it’s commonly referred to, which is in essence the big-picture delta or change throughout the rpm range, not just peak gains, and on the N54 it’s incredible to say the least.  With all of the upgrades this 335xi is making well over 100awhp and 150awtq throughout most of the rpm range, which really, is quite insane considering the minimal investment put into this build. A true testament to what an N54 is capable of with basic modifications.

DYNOJET vs. MUSTANG DYNO

Although we were very happy with the results on the DynoJet, we had the opportunity to run it on a Mustang dyno for comparison. So we strapped our project 335xi down on the Mustang dyno, which traditionally reads much lower than a DynoJet.  On the Mustang dyno our 335xi put down a very similar 388awhp and an enormous 498awtq. Only 13whp less and a strong 37wtq more than our DynoJet results. However, dyno charts aren’t the only way to measure results, so we put the 335xi to the test at the drag strip to see what it could do in the quarter mile.  

¼ MILE TESTING

Brake-boosting the AWD N54 yielded a best blistering fast time of 11.9 @ 116mph.  That’s about two full seconds faster than a stock N54 335xi which typically run in the 13.8 to 14.00 second range.  To say that again, TWO FULL SECONDS off the stock time, on the stock turbos, with only bolt ons and a tune.

What’s even more impressive is that it did so consistently, after 10+ runs, all of the times were within .3 of a second and 2mph from each other.  We attribute the consistent performance of the 335xi to the AWD system and automatic 6 speed ZF transmission which eliminated errors in shifting and keeping traction on launch.  However, if this were a RWD 335i we would expect to see trap speeds closer to 120mph.  

To put that time into perspective, this means that the full-weight FBO N54 335xi on 20” wheels with an all-in cost of only $17,000 was crossing the quarter mile mark at about the same time as a 2015+ DCT F80 M3 / F82 M4 with the S55 engine.  Not to say that a 335i is a better car overall, but if you pulled up to an M3/M4 at a stop light, you’d keep up just fine.

THE RUNDOWN

Our main goal for project 335xi was to show N54 owners what’s possible in terms of power and performance without making major modifications or investing a huge amount of money.  By following the advice given in our original article we were able to achieve over 500hp (that’s crank HP) and get into the 11’s in the quarter mile.  Very impressive results considering the minimal investment put into the project.

For more info on making your N54 faster:

CLICK HERE

Or email us at:

getarmed@armmotorsports.com