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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Why do a MHD backend flash on Jb4?



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      05-15-2018, 01:40 PM   #1
MSully96
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Why do a MHD backend flash on Jb4?

Ive looked around a bit and cant seem to find answers although I see many people doing it. Given the mods in my signature, what benefit comes with doing an MHD backend flash? Within the coming months I'll have inlets and FMIC and that would mark my build complete...unless I get power hungry again and get a e85 fuel pump or upgrade turbos..

************************
5/19/18 UPDATE AFTER MHD PUMP BEF: Editing this post because this needs to be said. A few hours ago I did the pump bef via mhd and all I have to say is: My. God. After a little driving and giving the car time to re adapt map 5 and dial everything in, I am in shock at the difference this made. Responsiveness, smoothness, faster spool + a couple more pounds of boost, and the car throws me even further into the back seat! If anyone ever is on the fence about doing a BEF, there is no reason to wait or debate it. The outcome is UNREAL! Couldnt be happier!
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Last edited by MSully96; 05-19-2018 at 06:47 PM. Reason: WOW
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      05-15-2018, 03:03 PM   #2
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I am FBO and just did this. It's so much smoother than with just the jb4. I'm hitting 17psi on map2 and it feels just like stock except I look down and I'm going twice as fast as I thoguht. I'm going to get on a dyno soon and see the difference.

I'm sure there's a more technical answer about what it does but based on the smoothness, I'm sure it's much healthier for the car as well vs just using a jb4 map 2 or 5.
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      05-15-2018, 06:54 PM   #3
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Two of the biggest benefits from the BEF that you'll experience are proper timing adjustments and proper management of the fuel system, the latter is especially useful for running e85 blends so you don't lean out the afr but will still both be beneficial even without e85.

Instead of the JB4 tricking the dme into thinking the car is running at different parameters, the DME itself will be tuned for them and handle control of it which is both a bit safer and will give you some extra power, plus the "smoothness" everyone notes when flashing an MHD map. My recommendation if your fuel pumps are healthy and you have access to e85 would be to run a BEF setup for e25 or e30, ethanol is a lot less likely to knock and will keep your engine temps down which both allow you to run more timing and can potentially prolong the life of your engine. Not only that but the extra low end torque and high end HP is a blast and extremely noticeable
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      05-15-2018, 07:37 PM   #4
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Sorry to threadjack, but once you back end flash how do you turn off the cel for catless downpipes?
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      05-15-2018, 07:56 PM   #5
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From the FAQ:

Quote:
What is a back end flash map?

For those who prefer flash tunes but want to keep the benefits of JB4
functionality and features just add in a back end flash map. The BEF
are templates you can write to your DME using the MHD or ***********
N54 flashing systems that are specifically designed to compliment JB4
tuning. These maps adjust fueling, timing, load targets, VANOS, and
other functions on flash side while allowing the JB4 to retain its
superior absolute boost control, on the fly map changes, in dash
gauges, shift light, auto learning/self tuning, gear dependent boost
control, data logging, WMI integration, PI integration, NLS, and other
features. It's simply the best of both worlds and greatly eliminates
the need for expensive and time consuming "custom tuning" those
running flash only often have to resort to. Note BMS is not affiliated
with *********** or MHD, does not provide flashing tools, and no
flashing support is provided beyond the templates posted. Contact
*********** and/or MHD directly for flashing support and additional
information as needed.

What are the benefits of running a JB4 with a flash rather than flash
only for tuning?

While it's possible to tune an N54 without a JB4 doing so comes with
many disadvantages.

1) The JB4 includes more robust safety systems than are possible via
flash only. Starting with fundamental safety systems like reverting to
a safety map if boost exceeds your safety setting, if the air/fuel
ratio in either bank turns dangerously lean, or if fuel pressure drops
below a safe level. While you might think the DME alone can handle
these basic safety systems surprisingly it's not the case. The DME
will happily let you run along at full power and a 18:1 AFR, with
boost pegged if a WG line drops off, and the only fuel pressure safety
provided is when fuel pressure drops down so low fuel injection itself
has to be suspended. In addition to these basic safety systems the JB4
offers layered advanced safety systems. For example it monitors fuel
trims bank to bank and reverts to safety if they exceed more than a
15% variance indicating a possible fuel distribution or o2 sensor
issue. Port injection and WMI add extra failure points and the JB4
control provides advanced safety systems for them as well. The port
injection FAQ covers the basics.

2) The JB4 boost control system is programmed as absolute meaning
you'll always target a specific boost level. Unlike the DME which
naturally implements a LOAD control system where boost levels go down
when it's cold and go up when its warm. The opposite of what you
generally want for turbocharged performance. In addition the JB4 is
quick and easily adaptable to a wide range of setups eliminating the
need for expensive custom boost tuning and the risks that come with
repeated logs on systems that are not yet setup. It's not uncommon for
engine damage to occur while a new setup is initially being dialed in.
The JB4 automatically tunes wastegate dutycycle, fuel trims, and other
important tuning criteria full time in the background greatly
simplifying the tuning process. In addition the JB4 auto-tuning map
can self tune for various ethanol mixtures without the need of an
expensive and difficult to install flex fuel sensor. Pedal to boost
mapping, spool aggression, boost by gear, and other critical factors
can be easily adjusted in dash on the fly to suit the needs for the
particular track or racing situation.

3) On the fly changes. Whether it's changing the boost/power level,
boost by gear setting (including being able to disable it on the fly
for burn outs or if traction turns out to be better than expected),
pedal input, 2STEP RPM, or what gauges are shown in dash, the JB4
allows a wide range of user adjustment real time from the drivers seat
without having to use a 3rd party device or risk programming the DME
between runs. You're able to make the changes while out on the track
where you need to make them.

4) The JB4 allows for much better real time feedback to the driver.
User adjustable in dash gauges allow you to keep a constant eye on
boost, timing, knock, meth flow, and/or AFR, all selectable and
changeable on the fly from the drivers seat. A user adjustable shift
light can be triggered making rowing through the gears easier. JB4
Mobile allows wireless bluetooth logging via your Android or Apple
phone without a cable locked in your OBDII port. In addition you can
select map0 on the fly to allow OBDII port logging and diagnostics
when needed for vehicle service. The JB4 default logging set includes
all relevant data required for tuning including boost, timing
cylinders 1-6, AFR and fuel trims in both banks, high and low fuel
pressure, load, calculated torque, trans temperature, and many other
parameters. The JB4 provides a simple to use but incredibly robust
data logging system eliminating the need to select what parameters to
record before each run and providing instant on the fly charting
without the need of 3rd party internet programs. We routinely add
parameters to the JB4 logging set based on customer feedback and
evolving tuning requirements. The JB4 samples boost and analog sensors
250 times per second and CANbus specific data like air, fuel ratio,
fuel trims, and timing advance 10 times per second.

5) Integrated JB4 features such as no lift shift, 2step, anti-lag,
port injection control, flex fuel sensor, and progressive water/meth
(WMI) control eliminate the need for independent add on boxes that are
more difficult to install and technically unable to communicate with
each other. Integration allows these extra features to share
information for a smooth and cohesive tuning solution. For example
with the JB4 NLS and JB4 port injection control when you press the
clutch in for NLS your port injection flow is momentarily suspended to
avoid huge backfires that have been known to blow out o2 sensors and
in extreme cases blow up intake manifolds. When the DME requests a
torque drop due to traction or stability control the JB4, WMI, and PI
systems all respond accordingly. JB4 anti-lag has a dedicated user
adjustable boost limiter to avoid unnecessary engine stress while
engaged. WMI integration is able to hold boost levels low UNTIL fluid
is flowing adequately to prevent spool up and transitional knock,
adjust your boost target if the fluid being injected turns out not to
be as potent as was expected or required to prevent knock, and in the
event of a fail-safe depending on the severity of the situation either
lower your boost target partially OR instantly dump boost out the
diverters/close the throttle/cut timing. These are just some of the
many examples of why having add on boxes an features all integrated
through a single system is advantageous.

6) The JB4 is widely used and widely supported including free unlocked
back end flash maps and custom mapping support from BMS via the
n54tech support forum. BMS sponsors and attends several 1/4 mile and
1/2 mile races per year continuously improving the JB4 base maps and
features based on real world experience and feedback. These updates
are provided free of charge to JB4 customers via n54tech firmware
posts.

7) The JB4 hardware is robust, reliable, highly developed, and
upgradable, with many thousands of systems in use since 2008 when it
was first released. The key to the JB4’s success is that it DOES NOT
replace the factory engine computer or DME. The JB4 simply adds on to
functionality already provided by the DME. As a result the DME remains
in full control of your engine at all times with the JB4 dynamically
making small but impactful adjustments to add in extra safety systems
and features and dramatically improve performance.
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      05-16-2018, 10:41 AM   #6
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Thank you all for the input and the article Mike. Definitely convinced and going to give it a shot. Assuming I have the right device, a kdcan cable, Im sure I can find a quick guide for how to do it. Im running e25 now and with my current setup the car feels great but knowing it can get even better just with a BEF before inlets and FMIC, insane.
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      05-16-2018, 01:12 PM   #7
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Quote:
Originally Posted by MSully96 View Post
Thank you all for the input and the article Mike. Definitely convinced and going to give it a shot. Assuming I have the right device, a kdcan cable, Im sure I can find a quick guide for how to do it. Im running e25 now and with my current setup the car feels great but knowing it can get even better just with a BEF before inlets and FMIC, insane.
just make sure since you are running E maps without an intercooler to monitor your IAT temp.
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      05-16-2018, 02:12 PM   #8
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400hp for a 17 year old to go faster on the street? Do it!!! Its a great idea👍
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      05-17-2018, 02:54 PM   #9
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Quote:
Originally Posted by dublin14 View Post
400hp for a 17 year old to go faster on the street? Do it!!! Its a great idea👍
I believe your sarcasm has been misplaced mate.
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      05-18-2018, 01:54 PM   #10
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Quote:
Originally Posted by dublin14 View Post
400hp for a 17 year old to go faster on the street? Do it!!! Its a great idea👍
Yeah not sure what you meant by that but okay.
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      05-18-2018, 02:39 PM   #11
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Quote:
Originally Posted by MSully96 View Post
Yeah not sure what you meant by that but okay.
Somehow he posted in this thread but he thought he was in this one.

http://www.e90post.com/forums/showthread.php?t=1496354
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      05-19-2018, 06:46 PM   #12
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Edited the OP, take a look.
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      08-17-2018, 05:45 PM   #13
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Quote:
Originally Posted by MSully96 View Post
Ive looked around a bit and cant seem to find answers although I see many people doing it. Given the mods in my signature, what benefit comes with doing an MHD backend flash? Within the coming months I'll have inlets and FMIC and that would mark my build complete...unless I get power hungry again and get a e85 fuel pump or upgrade turbos..

************************
5/19/18 UPDATE AFTER MHD PUMP BEF: Editing this post because this needs to be said. A few hours ago I did the pump bef via mhd and all I have to say is: My. God. After a little driving and giving the car time to re adapt map 5 and dial everything in, I am in shock at the difference this made. Responsiveness, smoothness, faster spool + a couple more pounds of boost, and the car throws me even further into the back seat! If anyone ever is on the fence about doing a BEF, there is no reason to wait or debate it. The outcome is UNREAL! Couldnt be happier!
So the jb4 is on map 5 as well as a back end jb4 flash? I'm currently on g4 and deciding if I should upgrade to g5 then mhd flash or ditch jb4 altogether and go mhd flash only. I guess the question is, does jb4 g5 + mhd make more power than jb4 g5 only or mhd only.
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      08-17-2018, 06:45 PM   #14
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Quote:
Originally Posted by straightcashhomie View Post
So the jb4 is on map 5 as well as a back end jb4 flash? I'm currently on g4 and deciding if I should upgrade to g5 then mhd flash or ditch jb4 altogether and go mhd flash only. I guess the question is, does jb4 g5 + mhd make more power than jb4 g5 only or mhd only.
A car running MHD only car can make just as much power as a car running MHD + JB4, but having the JB4 adds some safety features that you wont get running MHD only (check out Mikes post above). IMO the JB4 is good but with MHD BEF it's way better.
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      08-18-2018, 03:54 PM   #15
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Quote:
Originally Posted by White330 View Post
A car running MHD only car can make just as much power as a car running MHD + JB4, but having the JB4 adds some safety features that you wont get running MHD only (check out Mikes post above). IMO the JB4 is good but with MHD BEF it's way better.
thanks for your reply man. I appreciate it. I will go with upgrading to JB4 to G5, THEN do the JB4 BEF with MHD. Since I did see some tunes stating it added 1-1.5 psi throughout each JB4 map.
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      08-18-2018, 08:28 PM   #16
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Quote:
Originally Posted by White330 View Post
A car running MHD only car can make just as much power as a car running MHD + JB4, but having the JB4 adds some safety features that you wont get running MHD only (check out Mikes post above). IMO the JB4 is good but with MHD BEF it's way better.
Right, the BEF gets the DME setup to be closer to the actual tuning so the JB4 has less heavy lifting to do on the tuning and and can focus on features, safety, and extras. You also get top notch tuning support, free maps, and a ton of options and flexibility for the car like logging to your smart phone, in dash gauges, on the fly boost by gear adjustment, zero boost valet map, etc.

Mike
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      08-18-2018, 09:39 PM   #17
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Have the day the car feels night and day with the BEF and the JB4. Throttle response is definitely different, not in a bad way but car feels much happier and the power is much better in every map
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      08-19-2018, 10:46 AM   #18
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Quote:
Originally Posted by Soden82 View Post
Have the day the car feels night and day with the BEF and the JB4. Throttle response is definitely different, not in a bad way but car feels much happier and the power is much better in every map
Can you explain to me how it works? You load the jb4 bef, but then run map 5 only?
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      08-19-2018, 10:47 AM   #19
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Quote:
Originally Posted by Mike@N54Tuning.com View Post
Right, the BEF gets the DME setup to be closer to the actual tuning so the JB4 has less heavy lifting to do on the tuning and and can focus on features, safety, and extras. You also get top notch tuning support, free maps, and a ton of options and flexibility for the car like logging to your smart phone, in dash gauges, on the fly boost by gear adjustment, zero boost valet map, etc.

Mike
Any deals on g5 board iso upgrade + 2 step 😉.

Also, general mhd question for those in thread. will I need dp fix for inspection, I've read mhd can pass inspection. PA allows one monitor unready, and jb4 only always have me a hard time with monitors
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      08-19-2018, 10:58 AM   #20
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Can someone explain technically what the backend flash does to the DME?

How is it different than an OTS MHD map?
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      08-19-2018, 11:16 AM   #21
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Quote:
Originally Posted by ferocity02 View Post
Can someone explain technically what the backend flash does to the DME?

How is it different than an OTS MHD map?
No expert here at all but from what I've read I believe BEF is just designed to work in conjunction WITH JB4. It let's JB4 handle the target boost loads while BEF works in the back end to take care of vanos/timing/AF/ etc.etc. OTS Map does all of the tuning alone without JB4S features (gauge controls, safety, etc.)
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