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      04-14-2019, 11:10 AM   #12
PeterY
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Drives: Graphite E92 335i N54 6MT
Join Date: Jan 2012
Location: Melbourne, Australia

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2007 BMW 335i  [0.00]
Cool

Been a while since I've updated my build thread, the backlog of mods to review is very lengthy, and I am very time poor. I have lately been flat out busy between work and sorting out the race car as we approach the biggest production car race in Australia, held over the Easter weekend (wish us luck). Couple of photos of that beauty:





Moving on to my car, I will continue the front-end suspension discussion started earlier in this thread later on, as it's time consuming doing suspension mods reviews properly. Let's talk N54 tuning bins, and in particular focussing on the IKM0S from the E82 1M.

Background:

The N54 engine was managed by three DME's, MSD80, MSD81 and MSD87:

-MSD80, came on 2006-2007 E9x 335i
-MSD81, 2008+ almost all N54 cars except for the F01/2 740i
-MSD87, F01/02 740i (beyond the scope of this thread)

The above DME's has different bins running on them:

MSD80:
-I8A0S bin = all standard E9x 335i

MSD81:
-IJE0S bin = all standard E8x 135i, E9x 335i and E71 X6, including N54 cars tuned with the BMW PPK (Performance Power Kit)
-INA0S bin = 35is cars, i.e. 135is, 335is and Z4 sDrive35is (135is and 335is were USA only models)
-IKM0S bin = 1M (this is the one you need to remember )

Problem:

Speak to any manual N54 owner, and they will all tell you how hard it is to rev-match a N54. Pretty damn hard! The motor is just so damn lazy to rev up freely when it's not under load, I actually need to floor the accelerator to the carpet to blip the throttle when downshifting from 3rd -> 2nd, just to bring the revs high enough, and even then it's still very slow to build revs. When downshifting You have to hold down the clutch for longer waiting for the revs to rise before you can release the clutch pedal.

What's interesting, is that the DCT transmission had the ability to blip the throttle on the N54 extremely fast when it's downshifting this gave it away that the motor is actually capable of being revved up super quick and other electronic factors were playing a role to hold it back. Moreover, after driving an E82 1M, I noticed that throttle response is very sharp and precise on it.

Theory 1:
The standard N54 has a very heavy dual mass flywheel, and that's why you can't bring the revs up quick enough when free-revving the engine between shifts. The 1M has a lightweight flywheel, hence why it has a better throttle response, sounded promising enough to try at least.

As a result, you see heaps of people upgrading to a noisier lightweight single mass flywheel to hold more power, and also hoping the motor gains a sharper throttle response. On my car I used to have Motiv SST twin-plate clutch with a 25-30% lighter weight single mass flywheel. But I was disappointed to see that this barely reflected on an improved throttle response, I expected the motor to rev freely A LOT more , at this point, I knew 100% that there's another factor involved. (Btw, I don't think running this clutch kit was a good idea on a street car, apart from the fact that it's stupidly difficult to drive, it ended up failing after a few thousand kilometres, look in my sale thread here for photos).

Theory 2:

The N54 has a very long air intake tract, and as a result, it's super lazy to spin up quickly, because air has to travel a long distance round and round until it reaches the throttle plate. So from the moment you press the pedal, by the time air volume actually exits the turbos, goes through the outlets, then intercooler, charge-pipe and eventually arrives at the throttle body, it takes time, hence why the motor is lazy. Tbh at the time this made the most sense to be the reason behind the lazy N54 throttle, because when I drove a friend's M140i with the newer 3.0L 6 cyl B58 engine, the throttle response was very sharp and precise, it almost feels naturally aspirated, in my limited understanding at the time I attributed the good throttle response to the short intake tract of the B58.

Below are the N54 vs B58 air intake tracts lengths side by side, unfortunately I couldn't find the same type diagram for both, but you can still see the N54 has significantly longer air travel path from the moment it leaves the turbos, until it reaches the throttle plate:



Theory 3:

The speed at which the throttle plate opens is electronically controlled, and regardless of how fast you stab the accelerator with your foot on rev-matching while downshifting, it'll still open slow!

This by far made the most sense to be the cause of the issue, because the lightweight single mass flywheel that I had in the past, didn't reflect in making the motor spin up quick enough. It didn't make sense that I reduced the mass of the flywheel by ~30%, and the motor only feels like it revs 5-10% quicker. From an engineering point of view, it just didn't add up.

I turned around to ask everyone I know that is familiar with tuning N54's about this, and they all responded that there's nothing in the XDF's reflecting throttle plate movement speed, or on the contrary some sort of throttle plate actuation speed inhibitor.

I gave up at this point and just decided to live with it UNTIL I tried the 1M tune bin on my car....

Solution:

A few months ago, I picked a M3 DSC unit (module + pump), in an attempt to retrofit ///M Drive to my car. ///M drive is explained above in post #9. For the ///M button on the steering wheel to work, it needs either the MSS60 DME from the E9x M3, or MSD81 DME with the IKM0S bin loaded on it from the E82 1M.

Obviously my car being N54 powered, I can only flash the 1M tune to it. The 1M bin can only be flashed to the MSD81 DME (refer to the start of this post to workout which DME you have and which bin is loaded on it from factory).

What I discovered next was a nice surprise , the IKM0S turned out to have extremely sharp throttle response, it still remains as a linear throttle, i.e. 10% throttle = 10% torque request, but the IKM0S opens the throttle plate to the required angle IMMEDIATELY! If you tap the throttle very quickly on and off with your foot, the whole car will just jerk as the engine responds to the momentarily opened throttle plate, turned out that all the the standard N54 bins (I8A0S, IJE0S and INA0S) have built-in throttle dampening, which means they slow down the throttle plate movement to give you a more comfortable, more relaxed driving experience.

The 1M IKM0S bin feels amazingly satisfying to drive, I put 534km of pointless unplanned driving on mountain roads the day I discovered it, just for the sake of sheer driving pleasure. Ohhhhh I cannot describe how precise and how accurate the rev-matching and downshifting feel now, very satisfying! I love blipping the throttle in my flip flops and rev-match like a pro when slowing down LoL. I pretty much rev-match every single downshift now, it just feels gold

Looking through the 1M technical documentation, and I found this:



I can imagine BMW ///M engineers saying "Was ist das für eine Scheiße?" (What is this shit?) when a standard 135i got handed to them to use as a base for creating the 1M . At the end of the day, the N54 was developed by BMW AG to be used on standard passenger cars, the whole 1M thing and using the N54 in a ///M car was an afterthought, there was no need to tune it for a super fast/super responsive throttle plate actuation from the start, if anything, comfort was probably the goal when this engine was getting developed.

To make this factual, I did two logs on the same exact custom tune that I am running to examine the difference in the actuation speeds of the throttle plate, on one log I used IJE0S European E92 PPK bin, and on the other I used IKM0S European E82 1M bin (both running the same exact custom tune):

IJE0S (standard N54):



IKM0S (1M):



You can see that the throttle curve is steeper and sits closer to the actual pedal position on both opening and closing on the IKM0S (1M) bin, if you look at the time off the graph required for the throttle plate to go wide open in both cases, the IKM0S is faster by about 0.41s to fully open up to the maximum angle (i.e. WOT). Which is hugeeee in terms of feel and response when you're behind the steering wheel. This alone, has transformed the whole feel of the car for me

I noticed when I drove on bumpy roads, my foot wasn't very stable on the accelerator, the whole car jerked and surged lightly as my foot was pressing the throttle and releasing very tiny amount due to the bumpiness of the road. The standard N54 bins (I8A0S, IJE0S, and INA0S) all tend to ignore those tiny and brief accelerator inputs to provide an overall smoother ride for the occupants. But IKM0S (1M bin) will change the throttle plate position immediately with even the tiniest accelerator position change, and you can certainly feel it in the seat. In other words, all the standard N54 bins have a dampened throttle input for comfort, which is also the culprit for lazy throttle feel, and making it very hard to rev-match and blip the throttle quick enough on this particular motor as discussed earlier... etc.. But the 1M bin being developed by BMW ///M for a sports car, has been properly remapped to sort that, and to make it behave like a proper sports car should.

The DME tables that manage the throttle plate dampening or inhibition are not in the public XDF's, they're probably not even discovered yet, MHD Tuning do you know about this?

Once they're discovered, this feature can also be applied to standard N54 bins, but until that happens, running the 1M bin is the only solution to obtain a quicker throttle plate actuation.

Be mindful that throttle plate response and its actuation speed are a completely different thing to the "Linear Throttle" option that can be ticked in MHD, and of course different to turbo lag too. I only ever use linear throttle on my car under any case, not to be confused with the transient throttle response of an engine which is being discussed here.

🚨 NOTE: The IKM0S 1M bin will not work by just flashing it onto a regular 135i/335i. It has internal checks that it performs against the DME (powerclass coding... etc.) to verify that the car it's getting run on, is indeed a 1M. There are ways to turn off these internal checks by changing certain bits in the bin, all info on how to get there and migrate from I8A0S, IJE0S, INA0S to IKM0S in my next post, post 13. Now MSD81 car can run IKM0S

Last thing to consider, the 1M was the most powerful production version of the N54 motor and the most motorsport-oriented, naturally you'd expect it to form the best base tune foundation to use for a custom tune. If you're considering a custom tune, basing it on the IKM0S is the way to go (or the PPK IJE0S, but you'll miss out on the awesome razor sharp throttle response associated on the 1M bin).
__________________
Sparkling Metallic Graphite 335i Coupe 6MT (Build Thread) | MHD Custom Tune | Wagner EVO2 FMIC | Öhlins R&T coilovers with 8/14 Swift springs | Dinan Camber Plates | Rear HardRace fully ball-jointed toe arms, upper camber arms and guide rods | Front M3 control arms with Monoballs ball-joints | M3 Steering rack with servotronic retrofit | E93 M3 Front & Rear Sway Bars | Nolathane rear subframe bushings | HEL Performance SS braided brake lines | 19" BMW 437M wheels | BMW P steering wheel | CIC+Combox retrofit

Last edited by PeterY; 05-17-2020 at 08:06 AM..