I've been doing some reading, and am about to pull the trigger on a JB4. But before I do I have a few questions:

How many of you have it on your DD?
At what mileage did you install it, and what is your current mileage?
Assuming you can stay out of the throttle, how much worse are your MPGs?
Does the auto code deletion feature work well?

Thanks!

 

I can only speak to a couple of your questions since I haven't upgraded from JB3 to JB4, yet.

- I've been running it on my daily driver for about a year or so now. I ran the JB+ for about 3-6 months before that.

- I've logged nearly 12k miles (41k-50k) with it.

- I don't really track my mileage. Due to traffic during my daily commute I'm out of the boost most of time. I would say there hasn't been a change during normal use though. During "spirited" drives it defiantly has an impact on mileage but that is to be expected when making more power.

- The JB3 doesn't have the code delete feature so I can't comment on how well it works personlly.

I would recommend joining n54tech for more research and support on any BMS products. Terry provides first rate support.

 

I have the JB4 on an auto 535i. I get 17.5 mpg in suburban driving, depends of how hard I hit the throttle. Highway is high 20s. Doing quick sprints and hard acceleration definitely chews up gas, so it comes down to driving style. I would say the difference is minimal if you drive in the same manner as before the install.
Overall I tend to drive faster than without the JB4, just because you get used to all that power on tap. Why else would you go through the trouble of installing it if you aren't gonna rip it once in a while?

 

I have it.
Installed at 32000 miles, have had it for 6000 miles now.
MPG dropped from around 20ish to around 18.3, mostly because you are more heavy footed after installing it.
Code delete works perfectly, have took my car in for service numerous times after deleting codes.

 

Separate question about JB4....Does it improve throttle response and reduce turbo lag. I'm less interested how fast my top end speed is, and more interested in low-end torque and responsiveness from standstill. Anyone?

 

Yes there are also different map settings you can set to for changes in throttle and turbo lag.

 

I installed mine at 50000 and I have 54000 now. The car is a beast! Before, if I turned off the DSC, place in sports mode and turn off AC then floor it at 10 mph, I might get the tires to chirp but the car of course moved on out. Now, if I do the same the the back end will fishtail and clearly leave a nice set of black marks. I love the power this mod added! Gas miles actually increased 0.5 I consistently get 24 with town and high combined 28-29 if I reset on the interstate. This is of course not jamming the throttle all the time...

 

I put it on at 41K miles and about to hit 60K. Love it. Mileage drops a little when driving around town hitting it hard. When on business trips hitting a lot of interstate I get around 27-28mpg. Auto code removal works great. Had my car in 2 times for warranty work they never mentioned anything. It will be the best mod you do to the car. I did the DCI also and now looking at Meth. Currently putting my car kitty money into a countermeasure LI product and a specdock.

Just do it the Burger tuning guys are great!

 

Are there any real world HP numbers? Very interested in this as my next mod...

 

http://www.e90post.com/forums/showthread.php?t=416797
Numerous DYNO spreadsheets of N54 engine with JB4, Proceed, Cobb, etc...
Many Dynos are of stock vehicles and many of vehicles with other engine mods along with the tune.