2008 BMW 135i: Mods, Specs, & Build Page

Rather than writing single posts every time I put a new mod on, or something goes wrong, I figured it would be good to start a build page for my 2008 BMW 135i. Here I will start from the beginning, from when I first bought the car to now, and will document all the mods along the way and problems I’ve run into as I search (slowly) for 600hp. Lets get going.

The Car: 2008 BMW 135i, ‘Year One of the One”

After searching for 6 months, I found the perfect 135i. With 32,500 miles on it, for $17K, I got a black ‘Year One of the One’ that was bone stock. It didn’t even have window tint on it (and it still doesn’t). It has the sport package, and is the only BMW I’ve ever ridden in that doesn’t have power seats somehow. She is a 6-speed manual with the infamous N54 engine. Here is a quick picture, with more to follow:

Black 2008 BMW 135i

135i Current Modifications List:


Matte Black Kidney Grills


BMS Dual Cone Intakes

BMS Cowl Filters

BMS JB4: Piggyback Tuner (you can read our N54 Guide to Piggyback and Flash Tunes Here)


Bone stock


Bone stock (hopefully coilovers eventually)

135i Tires & Wheels:

Front: 225/40/18 Michelin Pilot Super Sports

Rear: 255/35/18 Michelin Pilot Super Sports

Soon to Come:

Downpipes (read our N54 Downpipes Guide Here)

Window tint (15% front, 5% rear)

FMIC (probably VRSF)

Chargepipe (ER and Tial BOV)

The First Mods: Matte Black Kidney Grills & Cowl Filters

I had to start off with the basis. With an all black 135i (thank god it didn’t come with the chrome trim), I had to change the chrome kidney grills. Just plain ugly on an all black 1er. I also knew I was going eventually do a ton of mods to it, so I bought the cowl filters from BMS. The cowl filters are fantastic because: 1) you can completely uninstall the cowl, meaning you don’t have to spend 15 minutes removing it every time you are trying to get into the engine bay, and 2) it amplifies the engine noise (and the dual cone intake ‘whoosh’).

135i Matte Black Kidney Grills:

135i black kidney grills

You can see a picture of the BMS Cowl Filters below in my dual cone intake picture

The 1st 135i Performance Mod: BMS Dual Cone Intakes

If you haven’t read our N54 Guide to Dual Cone Intakes and don’t have dual cones on your car right now, you should go read it! Dual cones are a great way to pick up 20whp+ and 15wtq+ for less than $120. You can buy them here. I would recommend this as a first performance mod for every N54. They are super easy to install, very inexpensive, and generate great horsepower returns for the money. Not to mention how freakin awesome they sound!

BMW 135i Dual Cone Intakes

The 2nd 135i Performance Mod: JuiceBox 4 (JB4)

After the noticeable increase in power from the dual cones, it was time to start putting some serious power down. This called for Burger Motorsports JB4. You can click here to read about the Cobb vs. JB4 vs. ProCEDE. Anyways, the JB4 is responsible for holding the most N54 world records, and is a fantastic plug and play piggyback tuner to add 80whp+ and 80wtq+. The power addition from the JB4 only increases as you add more mods to your N54.

I picked one of these up from Amazon, you can see the link above, and installed it immediately. Zach had been running the JB4 on his 335i for awhile now, so I had felt the power and been behind the wheel of it and was itching to do the same to the 135i. I barely knew how the steering wheel functions worked, but I knew that Map 5 was all I needed. I loaded up the map and hit the road to feel the power.

I was driving down the road, in second gear, and went foot to the floor with the accelerator. She took off…until I hit 4K RPMS, at which point I triggered about 30 full seconds worth of misfires! Well crap. At this point my car had about 38K miles on it, so I had figured the spark plugs and ignition coils had never been replaced on the car, but was too eager to get the JB4 installed that I didn’t care to change them first.

Read: Why You NEED to Change your N54 Spark Plugs and Ignition Coils before installing a JB4.

Road Bump: New Spark Plugs and Ignition Coils

We have a DIY guide on this here: N54 Spark Plug DIY. You need to change your spark plugs and ignition coils prior to installing your JB4 otherwise you are going to be sidelined for a week like I was for the new parts to come in and for me to get them installed. The DIY is pretty easy but here are the tools you will need:

N54 Special Spark Plug Socket

N54 Bosch Spark Plugs (run NGK if you have 500whp+)

N54 Ignition Coils

Here are what my spark plugs looked like after 38K miles:

N54 spark plugs

Now that my spark plugs and ignition coils were in place….it was time to get the JB4 terrorizing the streets.

No Misfires! Sh*t…now I can’t even hook-up in 3rd gear!

The new plugs and coils eliminated all of the misfire problems, but now the problem was too much power! First gear would put me throw me into a 90 degree angle, 2nd gear would send me into the next lane of traffic, and 3rd gear was like I was power-sliding all down the road. I still had the stock run-flats on, and I had done a pretty good job of wearing them down to the bones. The run flat tires suck, and are like $400 a tire so I said hell nah, and went with the best tire setup for N54’s: Michelin Pilot Super Sports.

New Michelin Pilot Super Sports from TireRack.com

This is the first time I had ever bought tires online. I would normally just go to NTB and get them there, but the problem is, nobody stocks Michelin PSS’s anymore! They are nearly impossible to find, but fortunately, Tire Rack had them for about $205 per tire! Shipped to my door I got two 255/35/18 Pilot Super Sports for $447. And then it was only $36 to get them mounted and balanced from NTB! Sounded like a steal to me. Here is how the tires showed up at my door:
Tire Rack: Revolutionizing tire buying since 1979.

tire rack N54 michelin pilot super sports

I changed from the run-flat 215/40/18 in the front to 225/40/18 Michelin Pilot Super Sports

215 in the front seemed way too skinny for me. After all, that’s what my 200hp Mazda was running in the fronts. I wanted some more beef up front to hold up for all the added power. Here is how the 225’s look in the front:

I changed from the run-flat 245/35/18 in the rear to 255/35/18 Michelin Pilot Super Sports

Again, 245 was a little too skinny for the JB4 in my opinion, plus the 255’s just look awesome from the rear. The tires are almost flush with the fenders and give it a lot more stance.

135i 255/35/18

135i 255/35/18

135i 255/35/18

135i Water Pump Failure at 41K Miles!?

I knew the water pumps on these cars were terrible (most common N54 problems) but 41k miles!? The weather here in Houston has been brutal (for Houston standards), and I think that played a role in my water pump going dead. I was driving to work in the morning, and it was about 25 degrees outside, and I got the orange “engine overheating” light to pop up on the dash. I didn’t worry about it too much, because it was 25 freakin degrees outside, so I knew the engine wasn’t actually overheating. Then the light came on again, but this time it was red. I lost all throttle response and the car went into “super limp mode”.

I had to pull over on the side of the highway to let the engine cool down for a second. Then 5 minutes later the same thing happened. I was about 5 miles away from a BMW dealership that was right near my office, so I had to keep driving and stopping until I could just barely coast it into their service garage.

I told them it was the water pump, but they said they still had to run a $210 “diagnostic test” on the car. So great, now I was locked in to getting fixed at the dealership otherwise I would have had to pay the $210 fee plus a tow truck to get it back to my place. Get this, they tried to charge me $810 for the water pump itself. And then $750 for install. I laughed at their price and told them no thanks, that I would buy my own part. Of course, the BMW dealership doesn’t let people do this because they love to rape you on the parts margins. After I got a good laugh in, the service rep “spoke to his manager” and said they would let me bring my own part in. I over-nighted an OEM water pump for $400 and saved myself $410. I still had to pay for the service though at their astonishing $250/hour rate.

To be continued once more Mods arrive 🙂