[GuidoDoc]

I have done tons of reading and I have been using ATR for several months to build my own tunes. There is decent info and experience out there for n54 engines but less so for n55.

Dilemma is load overshoots. Actual load goes above requested load at the top of the curve early in the pull so I get throttle closure. Articles suggest adjusting waste gate duty to reduce boost and thereby reduce the overshoot. Why not just raise the load target much higher and let the engine/turbo max out where they can. I am not getting misfire/timing pulled/overheating or any other problem, just that the DME says "too much load delivered, close throttle for a moment" (yes my DME talks).

example- http://www.datazap.me/u/guidodoc/agg...a=2-4-14-16-17

When I load a map that caps load request at about 155 I am fine and never get throttle closure. Max load request of ~160 and I get closures. Too further complicate the matter, this doesn't happen on every pull. I am sure that has to do with small external things that cause less power/load to be delivered.

Anyone know what is max load possible with without FMIC/DP/turbo upgrades?

[asrautox]

Originally Posted by GuidoDoc

I have done tons of reading and I have been using ATR for several months to build my own tunes. There is decent info and experience out there for n54 engines but less so for n55.

Dilemma is load overshoots. Actual load goes above requested load at the top of the curve early in the pull so I get throttle closure. Articles suggest adjusting waste gate duty to reduce boost and thereby reduce the overshoot. Why not just raise the load target much higher and let the engine/turbo max out where they can. I am not getting misfire/timing pulled/overheating or any other problem, just that the DME says "too much load delivered, close throttle for a moment" (yes my DME talks).

example- http://www.datazap.me/u/guidodoc/agg...a=2-4-14-16-17

When I load a map that caps load request at about 155 I am fine and never get throttle closure. Max load request of ~160 and I get closures. Too further complicate the matter, this doesn't happen on every pull. I am sure that has to do with small external things that cause less power/load to be delivered.

Anyone know what is max load possible with without FMIC/DP/turbo upgrades?

That's the other, less-safe way to do it. If you're tuning on pump gas, I'd recommend making small incremental adjustments to the load ceiling to see if you start getting timing corrections. With corrected timing, you can probably target 200-210ish peak loads.

[Unklejoe]

Originally Posted by GuidoDoc

I have done tons of reading and I have been using ATR for several months to build my own tunes. There is decent info and experience out there for n54 engines but less so for n55.

Dilemma is load overshoots. Actual load goes above requested load at the top of the curve early in the pull so I get throttle closure. Articles suggest adjusting waste gate duty to reduce boost and thereby reduce the overshoot. Why not just raise the load target much higher and let the engine/turbo max out where they can. I am not getting misfire/timing pulled/overheating or any other problem, just that the DME says "too much load delivered, close throttle for a moment" (yes my DME talks).

example- http://www.datazap.me/u/guidodoc/agg...a=2-4-14-16-17

When I load a map that caps load request at about 155 I am fine and never get throttle closure. Max load request of ~160 and I get closures. Too further complicate the matter, this doesn't happen on every pull. I am sure that has to do with small external things that cause less power/load to be delivered.

Anyone know what is max load possible with without FMIC/DP/turbo upgrades?

I would think that adjusting the base WGDC is the better approach. The goal is to allow the ECU to achieve its target via the boost control loop, not move the target higher than what's physically possible so that you never exceed it.

The boost control loop was tuned by BMW to provide a semi overdamped response within a certain "pull-in" range and set point. If you aren't familiar with control loops, the set point would be the target boost (which is based on requested load) and the pull-in range is how far away the actual boost can be from the target boost while the loop still works properly.

Since you're essentially changing the set point, two problems are introduced. The first problem is that the system that's being controlled has different characteristics when run at higher pressures, which changes the response of the loop. The second is that your initial conditions are getting further and further away from the set point.

To fix this, two things must be done.

The first thing is to try to bring the initial conditions closer to the set point. I'm not too familiar with the BMW platform, but I'm pretty sure this is what the WGDC base table is for. Essentially, you would tune the car with the loop completely disabled and manually dial in the WGDC base values until the requested boost and actual boost match. Then, you can re-enable the loop. At this point, the loop would only have to make very small corrections. I don't know if this is possible with the BMW platform or not.

The second thing is to try to change the loop constants so that you can maintain a nice overdamped response. This is much more difficult. To be honest, if you got the base WGDC dialed in, you might not need to do this. This is usually done via extensive modeling and fine tuning. The control loop is probably a PID or PI loop with a few conditions.

I've seen approaches where the tuner just raises the requested load so high that the actual load never gets near it, but I don't think that's the right approach.

Hopefully someone with experience on this actual platform will chime in.

[GuidoDoc]

Those responses make sense. I made some tweaks and am able to get the same load without the TP closures. It seems like it mostly was in transition from spool mode to regular.

Load max of 200 seems a long shot without tons of changes in a stock car. I am getting to 160.

Would love to hear from protune freaks what kind of load they can get from stock N55.

[Unklejoe]

My car's actual load was around 180 in the 3800 RPM range, tapering down to the low 130's towards redline. This was on my stock turbo.

[GuidoDoc]

Originally Posted by Unklejoe

My car's actual load was around 180 in the 3800 RPM range, tapering down to the low 130's towards redline. This was on my stock turbo.

Do you have a DP or other bolt on mods? Who made your map?

[Joey911]

Hey OP, I want to learn to tune my own N55 using ATR also... Can you guide we where to start to learn?

[GuidoDoc]

Originally Posted by Joey911

Hey OP, I want to learn to tune my own N55 using ATR also... Can you guide we where to start to learn?

Cobb has an ATR manual, read and understand it. Then there are a couple posts on this site that are helpful.

http://www.e90post.com/forums/showthread.php?t=475578

http://www.e90post.com/forums/showthread.php?t=792736

Then do some more search and read. More posts about n54 but most of it still applies.

Then I studied the maps that came from Cobb and my stock map ( I have the BMW PPK). I created a spreadsheet of the differences and then did the best I could to understand what the changes were doing.

Then I took a stage one map, did some baseline pulls, then started small changes. Little bit at a time and logged to see the effects.

Right now I am at a very stable self made custom map with load increases that went from 140 now up to 160 and boost went up to ~12 psi (But we are targeting load). I am happy to help you along the way but disclaimer, I am not a protuner and make no guarantees. Tune at your own risk, but the ECU is smart to protect us from anything but drastic stupidity.

[Joey911]

Originally Posted by GuidoDoc

Cobb has an ATR manual, read and understand it. Then there are a couple posts on this site that are helpful.

http://www.e90post.com/forums/showthread.php?t=475578

http://www.e90post.com/forums/showthread.php?t=792736

Then do some more search and read. More posts about n54 but most of it still applies.

Then I studied the maps that came from Cobb and my stock map ( I have the BMW PPK). I created a spreadsheet of the differences and then did the best I could to understand what the changes were doing.

Then I took a stage one map, did some baseline pulls, then started small changes. Little bit at a time and logged to see the effects.

Right now I am at a very stable self made custom map with load increases that went from 140 now up to 160 and boost went up to ~12 psi (But we are targeting load). I am happy to help you along the way but disclaimer, I am not a protuner and make no guarantees. Tune at your own risk, but the ECU is smart to protect us from anything but drastic stupidity.

Thanks! Doing the readings now.

[GuidoDoc]

So I did some more tweaking and learning and I think I have hit the max. Remember I am full stock other than an ER chargepipe, K&N drop in filter and the Cobb AP.

Started with PPK from the factory with max load actual of 149. Then made some adjustments and got to a very smooth map with no TP closure and no timing pulls with max load actual of 166.

Increases in load above this level (up to 173) result in timing being pulled. One or two cylinders in a given pull by 1-3 degrees. Not the same cylinder so I don't think it is hardware. Most likely knock, right?

I also noticed the engine temps running about 10-20 degrees hotter than normal. Related?

I reread articles about adjusting AFR and timing for knock and it seems like the only way to keep load (and power) at the higher levels where I am currently getting knock is more octane. I already use 93 so little option there on a routine basis. Enriching the fuel mixture or retarding timing will eliminate knock but I will lose power so in the end the higher map doesn't offer any advantage, right?

Thoughts?

[Cory S]

I myself, along with asrautox, are working on my OTS maps.

The ONLY thing that keeps popping up, is actual load slightly exceeding requested load. (but not on EVERY pull!!!) I mean, the DME tries to keep actual load as close as the requested load as it can, but this is just too close IMO. Timing is OK for now. AFR is set to 12.2 now.

I have seen online datalogs of load ceilings far higher than actual loads, but smooth across the RPM range... What are they changing to do this? I'm guessing some TQ limits, limit ceilings, WGDC %'s etc......

[NOPOWER]

I'm working on my 135i N55 tuning as well and I'm facing a lot of the same challenges: throttle closures, inconsistent behavior in terms of requested vs actual load, a rocky boost curve I'm not proud of, etc.

What's the best way to collaborate? I loathe the fact that Cobb doesn't have a DIYer's tuning forum, and I've considered creating a Cobb tuning Facebook group, which I'll do in a heartbeat if anyone wants to join.

My most recent tune results, still a work in progress but much much better than OTS Stg2+ Aggressive: http://www.datazap.me/u/nopower/2016...r-v104-0?log=1

Peak load: 199

Current mod list:

• Stock airbox, K&N drop-in filter
• Stock turbo
• VRSF 5" stepped FMIC
• VRSF charge pipe
• GFB DV+
• VRSF catless DP
• Stock catback
• BMS short shifter, clutch restrictor delete
• ... and an AEM water/meth kit sitting on my desk waiting on the fuel cell

[GuidoDoc]

That log looks similar to the point where I felt like I hit the limit. Timing pulled on multiple cylinders but otherwise not to bad. Does the TP closure happen consistently in that range?

Does anyone know how increased load relates to HP/TQ at the wheels? I imagine there is a lot more to it because pushing load too high causes timing pull which decreases power. So load can't be a direct relationship.

From my reading and tweaking when you start having to retard timing as the only way to fix the map you have hit the limits of the fuel and hardware. Do others agree?

[Cory S]

The DME will pull timing for MANY reasons. Not just load/boost overshoots. The knock sensors are also VERY sensitive. I found, the more timing I command at loads above 185 (with proper fuel), the LESS timing corrections I have. Also, running too rich causes timing corrections randomly from what my logs tell me. I get much less correction commanding 12.2:1 AFR, VS. 11.7:1 AFR. These engines like to run a little leaner than your standard boosted NON-DI engines. I've seen many setups with JB4's running above 4000RPM in the 12.8-13.2:1 range.

[NOPOWER]

FYI, we've taken this discussion to a new Facebook group dedicated to N55 tuning:

https://www.facebook.com/groups/981209798660613/

Originally Posted by GuidoDoc

That log looks similar to the point where I felt like I hit the limit. Timing pulled on multiple cylinders but otherwise not to bad. Does the TP closure happen consistently in that range?

Does anyone know how increased load relates to HP/TQ at the wheels? I imagine there is a lot more to it because pushing load too high causes timing pull which decreases power. So load can't be a direct relationship.

Yes, very consistently, but look at the logs with ACCEL PED POS vs. TPS ACT. The DME is actually pulling throttle as self-defense against going over the target load, and based on the Cobb tuning guide that can & will cause timing issues:

Throttle Closures – The primary method of controlling boost on this car is done with the assistance of the drive-by-wire throttle system. The factory tune allows the throttle to close to less than 20% (of the ~100% max) which can result in consistent torque delivery, but reduced performance. There are two main offenders that will result in throttle closures: overshoots of load and boost. Major throttle closures can result in turbulent airflow entering the cylinders causing timing corrections. It is imperative when analyzing logs to assure no throttle closures are present during a timing correction event as these could create a false positive. We recommend adjusting these limits higher to take full control of the throttle and keep closures to a minimum. See our OTS maps for effective examples.

Originally Posted by GuidoDoc

From my reading and tweaking when you start having to retard timing as the only way to fix the map you have hit the limits of the fuel and hardware. Do others agree?

No, the first step is to reduce the WGDC (Base) map by 10% at a time until actual load comes in under target load without throttle closures.

[Rob_BMW_PNW]

What do you guys think of these logs?
135i 2011 DCT N55
ETS 5 inch FMIC, CP, 92 octane.

Auto WOT I 'think' it dropped me into 2nd and I just did a big pull through 4th
http://www.datazap.me/u/robertnguyen...log=0&data=1-6

MT WOT 3rd into 4th and redline
http://www.datazap.me/u/robertnguyen...log=1&data=1-6

[Rob_BMW_PNW]

Was just reading the AFR should be leaner, and I got low 11s lol

[joshe92]

Cobb removed the ATR and now it will come back updated, and you will have to pay for a training to use it!