How To Install a BMW N54 Single Turbo Kit (135i & 335i)

I want to kick off this post with a reminder that I’m installing the Doc Race single turbo kit outside of the car on an engine stand. Part of the reason I bought this kit was because I blew my motor which required to me remove and re-install a new motor. Great excuse to upgrade… right?!

Be sure to check out my separate blog post about everything you need to complete this swap, it will help tremendously as you read on.


The kit showed up about 4 weeks after I ordered it and came complete. I didn’t want to gamble with other vendors’ long lead times and kits that arrived with missing or poor-fitting parts. Doc Race knocked it out of the park and I’m glad I chose their kit!


Everything looked beautiful. I opted for the ceramic coating option and a ball-bearing 6266 turbo. The kit includes almost everything you need to convert to single turbo! Now let’s get these beautiful pieces where they belong…


Manifold studs replaced, manifold, heat shield and water pipe installed.


I had to mock-up the turbo… it did not disappoint.


Everything fit perfectly, just as it should. It was a lot easier to install the hot parts outside of the car, but I couldn’t do much more before having to install the motor.




Another night’s worth of work and I had everything else hooked up well enough to try starting the car. Since I was working pretty quickly, I didn’t document everything but I will highlight the important parts.

  • Wrap the downpipe AND manifold in exhaust heat wrap!
  • Use heat sheath on the oil feed line and vacuum lines .
  • Clock the turbo so that the oil feed line is at the top center of the cartridge.
  • Wastegate springs… install them accordingly.
    • I initially installed the white & green TiAL wastegate springs (11.6psi) but was getting 17psi at wastegate pressure.
    • I switched to the single black spring (8.7psi) and now get 11psi at wastegate pressure.
    • This kit is known to overboost by ~2psi and TiAL underrates their springs.
  • Once everything is installed, make sure the vacuum lines aren’t pinched or rubbing on anything. Go over them twice.
  • Plug the Mac Solenoid into one of the OEM boost solenoid plugs. The other plug can be left unplugged, or you can leave an OEM boost solenoid plugged in (but not routed anywhere) to avoid a check engine light.
  • If you’re using JB4, make sure you have the correct firmware and backend flash loaded. Go through this checklist on N54tech.

Single Turbo Install

Single Turbo Install

This was the first time I tried to turn over this used motor and see if the single turbo kit worked…

REJOICE! The long nights paid off.






Fast-forward to 6 months later. My experience with this kit has been fantastic and mostly problem-free. I had an O2 sensor die on me, but I ordered a pair from FCPEuro with a lifetime warranty. They’re fairly easy to swap out with the proper socket adapter and I’ll never have to pay for another sensor again.

I made 749whp and 643wtq at 29psi for those of you who like to push the envelope like myself. Otherwise if you’re easily amused, you can expect ~450whp at 11psi and ~550whp at 16psi. Check out my complete modification list if you’d like to follow my build.


I’ve done full lapping days at Road America with the car, brutal 1/2 mile events and even snapped an axle at the 1/4 mile track. The car is a blast to drive and sounds amazing.

I’m frequently changing my oil (every 2-3k miles) for peace of mind. Always keep an eye on things. Check vacuum and oil lines for melting or damage. Protect your ignition system from the hot top-mounted turbo. Just use common sense and stay on top of your maintenance and you’ll be fine. I couldn’t be happier with my decision!

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6 Replies to “How To Install a BMW N54 Single Turbo Kit (135i & 335i)”

  1. Is it really necessary to exhaust wrap your headers and downpipe when they are already ceramic coated. I have read that ceramic coated parts don’t like to be wrapped.

    1. Doc Race has started including oil drain line sheathing with their kit so the manifold doesn’t have to be wrapped, but I still recommend it. The downpipe should be wrapped for sure. Way too much heat near the valve cover otherwise.

  2. I Know I should have shopped more until I found a manual transmission 135i, but the automatic 2008 one I got was so new that I couldn’t say no. Have it FBO now (ok missing the exhaust) but not enough! What’s your thoughts on single turbo it? You think the transmission can handle this much power?
    Love your car, your posts/vids! Keep it up!

    1. Autos are more common, so I understand your reasoning. I see a lot of guys running 500-600whp in their 6AT. I think you will be okay as long as your transmission is in good working condition and you aren’t shooting for the moon when it comes to power.

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