Thread: BootMod3
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      12-13-2017, 02:57 PM   #3
Stubok
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Drives: Melbourne Red F30 328i M Sport
Join Date: Dec 2014
Location: Austin TX

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JB4 intercepts the sensors outputs and then manipulates them before sending revised values to the DME. As a result the DME adjusts its outputs to compensate. It also means the DME can sometimes see values that don't makes sense to it. Also some items like ignition timing can not be altered. boost and fuel pressure rail (allowing for a little extra fueling) can be but that's not taking the whole picture in.

Bootmod3 is actually a bootloader that allows the MEDV DME to be flashed over OBD2. That used to be the only way a tune could be loaded to the DME via OBD2. The other way was removing the DME, opening it and flashing directly. Similarly Bootmod3 was loaded to the DMEvia a bench flash using the boot pins. Once the DME was cracked and had Bootmod3 installed you were then free to upload tunes for your car, fuel type and any bolt ons you installed (ie downpipe, upgraded turbos etc) just by plugging your laptop or smart phone (and their agent device) into the obd2. It also means that adjustments can be made to the tune and new ones loaded over OBD2 when things change.

Now it seems you don't need to crack the DME and load Bootmod3 anymore, there is now a way to upload new Off The Shelf (OTS) or custom tunes over OBD2 without the need to crack it. See the latest threads on this on bimmerpost.

Either way with a proper tune, the DME gets actual sensor readings in real time and knows what to expect and what to do. The fuel, boost, ignition, Venos maps/tables can all be adjusted.

It's a lot safer and a lot more powerful. For example you can make a lot more power with ignition timing and better fueling without even increasing boost.

For N20 that's a big deal since it was designed to run efficiently (meaning lean) so throwing added boost and further leaning out the AF ration isn't a good idea. With a flash you can add a little boost, but more importantly fueling, venos and ignition timing and that results in a much better smoother more drivable outcome.

Just one other small thing I noticed changing from JB4 to my ACF Performance tune (loaded over bootmod3) was that the increases were evident at earlier Rpm's, while with JB4 they only came on once boost was at a positive value with rpm's in the 2800+ range.

Before I'd get some stutters and abnormalities when my engine transitioned from Normally aspirated to boost. Now I don't get any of that, just smooth power.
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