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Water/methanol diesel injection.

Practical Diesel Tuning

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So I just installed a water/meth kit on my bmw n57 engine.

It's running like a champ with hybrid turbo, bigger hpfp and so on. Been running somewhere between 400-500 hp estimated without any noticable smoke.

It took some tweaking to get the soi of the W/M injection correct, but I now kicks inn just before WOT conditions and the engine seems relatively happy with that. To early injections seem to be giving me occational hesetation and turbo shutter when cruising up a steep hill.

Now.. to the point. At WOT as the car revs past 2500 rpm the injection starts and you without a doubt feel it as it pulls significantly harder and it sounds and feels smooth and nice. Egt's are almost a 150c° lower and all wold be well except that when the wm kicks in, it is laying a lot of black smoke. My boost pressure is on point, so what is causing this?

Am I using a wm nozzle that is too big, pushing to much water making the diesel not burn complete, or have a mixed the water/meth wrong? Aiming at 50/50.


It sounds like you have a good thing going. Nicely done. I'll give you two suggestions on the smoke. The inexpensive option is to use a smaller jet and watch the smoke output. My hunch is that you're running too large of a jet. If you want to get a little big more precise you could install a WBO2 sensor and see exactly what your AFR is when the car is running clean, then target that same minimum lamba with the water meth by either raising boost or tuning your H20/Meth injection quantities and/or ratio.

You're on the right path, keep us in the loop.


Thank you for a very good answer Nick. I appreciate it alot.

I do apologise for the late answer, but as a result of the extra power from me wm I blew my gearbox to pieces. Just installed a new stronger 8hp box and got her back on the road. Not been able to really do some good pulls yet as I am having issues getting the new box correctly tuned and having slip on full power.

Maby we could see hpacademy do a course in gearbox tuning? I've done some attempts but without any great luck, so having to pay someone else to do it, alltho so far not successfully. (For the 8hp bmw gearboxes xhp is the greatest option, but because this box now is not original to the car I have not been able to get this to work together with xhp)

Anyway, I did as you suggested and tried to turn up the boost. I notice no smoke utill I passed 80% throttle. And when looking at the logs properly I appear to reach the physical limit of the map sensor, this causing boost pressure to halt, but fueling to keep on rising, hence lowering the afr and smoking.

So, thank you for pointing me in the right direction. As soon as I get my gearbox sorted I will upgrade the map and try again.🙂

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