JB4 w/ BEF vs MHD by itself


Oct 2, 2017
N55 DCT E82
2011 DCT 135i w/ DP, CP, intake, exhaust, and soon will have 7" intercooler.

Currently running MHD stage 2.

Considering buying a JB4. With the BEF is tq reported correctly to the transmission? I want to start running an ethanol mix but the small tank on the 1 series combined with the lack of many flex fuel stations around me and some out of state road trips makes me hesitate. I figure map 5 will allow me to mix E30-E50 when available but won't be a big hassle when I can only get 91. JB4 can always be used as a meth controller in the future if I upgrade the turbo.



New Member
Sep 30, 2017
2011 135i
I never ran a BEF when I was stock turbo. My DCT held up fine running e50 on map 5, and map 7 when i rarely used it.

That isn't to say you shouldn't run one. I don't have experience with the current BEFs that BMS provides on n54tech, but my car ran like crap on on the old ones. If they do not have a high load, you should be able to have Terry increase the load by shooting him an email. Otherwise work with a tuner to make you a custom BEF.

When my JB4 actually worked correctly, I loved it with the stock turbo. It certainly provides flexibility and a ton of great options. I really miss having bluetooth compatibility lol.