300wKw 135i:nearly there.

The Goal: 300wkw 135i and the road to it thus far.

First things First: Prologue and a little history

First off I would just like to say I am not trying to show off or brag or gloat or to even make a name with this post. I am not the first person to do this, It’s simply to tell those that are interested, my story with this car. Hopefully it will help and maybe serve as a guide as to what is possible.

Also the power reading, I am using FR&R’s dyno. Some dyno’s may read lower some may give me more, for simplicity sake I am only using one. Take the figures how you like to. This was my yardstick.

I never bought the car to break any records or race it for times or to even push it as far as it could go. Having a sibling rivalry with my brother over who has the quicker car/bike/scooter since childhood pushed me into this.

I consider this my hobby, I’ll race another car in the name of fun, I don’t see it as an ego contest or tuner battle, if I lose it makes no difference. I would have had fun and got the chance to run against a faster car and maybe learn something.
I have modified cars in the past but am by no means an expert.

Now the Car:

The Car is a manual 2008 135i, I bought it after over a year of research and figured it would be the perfect platform to destroy my brothers Subaru STI, I also wanted something that I could mod myself and not rely on a tuner unlike him. it was also the exact opposite of his, his was loud with big fins, carbon fibre everywhere and noisy blow off valves, the 135 was quiet with no exterior mods and looked like an everyday car a mom would go shopping in. I liked the idea of a sleeper.

The JB4 was fitted 2 days after receiving the car.
I never dyno’d a baseline as I was purely out to beat my bro’s 250Wkw Subaru at the time, which I lost… quite badly! I had some Race fuel and could experiment with high boost maps such as map 7. I then started to beat my brother, He then decided he wanted 300wKw and started doing internals and bigger turbo to beat me…I needed to up my game.

The Race to 300wKw begins:

While his car was in and out of the garage getting parts changed, exhaust done and experimenting with bigger turbo’ s I fitted a BMS windscreen washer Meth kit along with the supporting mods, Charge pipe and diverter valves, in my garage with the help of a friend. The cost difference was large.

The race was too close for comfort for him, he still beat me but the cars ran neck and neck. He then went with an even bigger turbo.
I have not run the Subaru since, as the car was sold. anyone who knows Subaru's knows that they like to pop jk.

The Dyno’s: Controversy

There is some controversy about the power readings on different dynamometers, I don’t want to get into that. I am trying to be as strict and as fair as possible, using the same dyno the same fuel and same meth mix to judge different mods so far.

And I do realize that 300Wkw is not the same as 300Wkw on another dyno. They are all different. I just hope that by sticking to one I have done the mods justice.

All my dyno’s thus far have been on pump 95 with a little NF. Around half a bottle to a full bottle depending on how much fuel is in the tank. I dyno with the hood up, I don’t believe that the fan can replicate the airflow that the road can, this may be my one consession as I know several people dyno with it closed, I’m not really sure what difference it makes…???
I run a 60/40 mix of methanol by weight.

Also, the car runs like this all the time, it’s not a dyno queen although it is a bit of a garage queen as it sits in the garage most of the week and taken out on weekends and the odd mid-week run.

1st dyno: 277Wkw(371wHp) @WRC. JB4 and Meth kit.

It was about this time I dyno’d the car out of interest and it made 277wKw (371whp) at WRC in Edenvale.



2nd Dyno: Jb4 G5 ISO and Meth

I then upgraded to a G5 board and did the ISO mod which allows higher boost and isolated boost control.
Got the car Carbon Cleaned by George Smooth a few months later, which made a huge difference to the feel of the car.

I was already seeing higher boost after the clean wanted to dyno’d again but WRC had closed down so took it to FR&R. The car made 372.2hp.(277.5)wkw Which is similar to the 277wkw (371hp) but I think that it reads lower than WRC as the car definitely felt faster.




3rd Dyno: 396whp (295.3Wkw)

I added a set of downpipes: Spool up is much much quicker and the car breathes easier. I got them ceramic coated and the coating makes a difference.



Result!: meh, not quite!

Then intercooler, fitted myself in my garage with the help of a friend. The car feels like it is driving on a cold night all the time, the dyno does not show great results but on the road it’s definitely noticeable.


My final result from last night! 399.2whp!! (297.7Wkw)




I am 0.8 hp shy from my goal, now I may go to another dyno and get a higher or lower reading, I’m not worried about that. I want to stick to the same dyno for consistency. I can mess around with settings and maybe squeeze that 0.8hp out.


Next Up:

I’m going to dyno the car on a mix Ethanol, I have already been playing around with it and the car feels much sharper and responsive with it. Will just have to see how much, I suspect I won’t see much more top end power but I think the graph will look smoother.
Hopefully I can get the 300KW mark I have the walbro E85 pump going in for Ethanol testing and the BMS flash coming soon.

And Beyond?

Big turbo’s? Maybe… I am quite happy with the car now, it’s not quite 400hp nor is it 300wKw and I guess that depends on who's dyno but it is already a handful and I enjoy driving it.
I may just settle with the power or change to a different platform. I still need to think about that.

Finally: Thank you

Last up but not least, a thank you, during this journey with the 135i I have come across a great number of amazing people and just feel a thanks is long overdue.

All the Fanatics: This forum has been a great help to me to share experiences, gain insight, buy and sell parts and connect with likeminded people. I thank you for all you encouragement, support, advice, criticism and opinions. So thank you.

Twinz aka Charles: Thanks for all your amazing write ups and advice, they are incredibly helpful.

George Smooth: I really appreciate your openness and honesty with your modifications. It has helped and inspired me. You are a pioneer. You do things the way they should be done and your knowledge of this platform and tuning is incredible.

Burger motorsport: Terry Burger has created the easiest way to modify a car, I cannot think of rival that comes close to the ease, performance and safety and cost of this unit. Everything a mid-level tuner can hope for is possible with just the JB4. It has made this experience enjoyable and worry free, it is literally plug in performance. His customer support is second to none!

I have spent relatively very little getting to this performance level mainly because I have been doing things largely by myself so far, and I think it’s possible with any N54 car, that’s properly setup. I even think more power can be squeezed out with these mods and some tweaking or a more advanced ECU control.

Hopefully I see more fast x35’s on the road. If you need advice you can pm me and I will be happy to help if I can.

Chris.