[bobbyggx]

Hi guys,

My car runs okay, but it is a bit on the slow side. I did some logging and I noticed that my target boost is a bit lower than the other logs I've seen on the internet. This is quite strange for me, as I would know what steps to execute if I am not meeting the target boost, but I am shocked to see that the Target boost itself is lower than it should be. From what does this target boost depends on?

Here is an exemplary log. The boost is in hPA with Atmospheric pressure around 960hPa, thus I have a peak boost at 5645rpms which equalas to 0.645bars (9.35psi). Usually at that point N55 engine is requesting around 11-11.5psi (0.79bars) and it is keeping it until 6300rpms while mine is dropping to 0,540bars (7.83psi).
http://datazap.me/u/bobbyggx/testo2?...data=1-2-5-6-7

Do you have any pointers for me? I did a boost leak test -> nothing came up. I boosted the system up to 22psi. Based on the above log the Wastegate Duty Cycle is okay, thus it is not indicating a leak as well. The Target and the Actual boost are close enough, I think, but the question is what is the reason to have a lower target boost value?

The DME has been updated to Daten 61.1.

Thanks in advance!

[bobbyggx]

Anyone? I am welcoming all sorts of ideas.

[weehe126]

What are your mods? What tune do you have? We have no idea what target boost used to be or what it should be.

[AJL]

Yeah, how did you even record that log? It doesn't appear to be from MHD..

Definitely need more information about what has been done to the car.

[bobbyggx]

The car is fully stock. It had JB4 installed, but I removed it. I want to be sure that everything is intact before starting any major projects.

It is '11 F10 N55.

Data has been logged with TestO, which I found to be a very good and useful tool. The Data logging is very fast. I don't have MHD, but I am hoping they would release the F series versions and I am hopping on!

[AJL]

Originally Posted by bobbyggx

The car is fully stock. It had JB4 installed, but I removed it. I want to be sure that everything is intact before starting any major projects.

It is '11 F10 N55.

Data has been logged with TestO, which I found to be a very good and useful tool. The Data logging is very fast. I don't have MHD, but I am hoping they would release the F series versions and I am hopping on!

I don't think they are going to be releasing MHD for FXX N55 vehicles. Your best bet would probably be bootmod3.

Anyway its hard to tell if everything is okay from that log, but here is one of my car on MHD 1+. Didn't hit the boost target most of the time..

http://datazap.me/u/ajl/baseline-dyn...21-22-23-24-25

[bobbyggx]

What is missing for you in my log? Bootmod3 would be better than the JB4?

Btw, what is consider a normal value for the MAF sensor on N55? My car, as it is visible from the log, is doing peak of 845 kg/h which I think is a bit low, but this "thought" is coming from a previous diesel owner, thus I am not sure if I am right?

EDIT/UPDATE:

I've examined your log and the MAF Req WGDC g/s and I can see that in my case I am running 100+ g/s less.

For example at 4500rpms your g/s value is roughly 276g/s. At the same rpms my Airmass reading is 639 kg/h (which is 639kg/3600 (seconds in 1h)*1000(1kg = 1k g) = 177 g/s roughly). The situation at 6500rpms, in your log, is 357g/s while in mine is 233g/s.

So, may be, if the reading of the air mass is low the DME is adjusting the Target boost, as it sees that there is not enough air. I am not sure why BMW did this thing, but in F10 the airflow channel is quite narrow compared to E9X LCI.

F10 is sucking air from a whole with similar size as the red rectangle.


E9X, a lot huger air channel:

[weehe126]

You are on the stock tune, you can't compare your g/s to his stage 1+ flash g/s. 11psi sounds right to me for a ppk tune. The stock boost target will change with the weather/altitude. It will always target the same LOAD not boost.

[AJL]

Originally Posted by bobbyggx

What is missing for you in my log? Bootmod3 would be better than the JB4?

I'm not an expert on these things, so someone feel free to correct me if I'm wrong.. But in general things like timing corrections, and fuel rail pressure are important to log if you're trying to determine how well an engine is running. They point to potential issues with fuel quality, plugs that need to be replaced, hpfp issues, etc...

Bootmod3/MHD and JB4 are fundamentally different in how they function.

JB4 is a piggyback and does not actually change the DME programming, just the values the DME sees. This is why you can just remove it and the car is back to stock.

Bootmod3/MHD actually change table values on the DME and do not require you to install additional hardware like the JB4. Vehicles with an MEVD1726 or newer DME have stronger protection against tampering. This is why products such as MHD and Bootmod3 require a bench flash to unlock before you can flash maps through OBD on newer models.

Tl;Dr JB4 is quick and cheap..but hey, it works. MHD/Bootmod3 is more expensive but will yield better results most of the time because there is direct control of engine parameters.

[bobbyggx]

Originally Posted by weehe126

You are on the stock tune, you can't compare your g/s to his stage 1+ flash g/s. 11psi sounds right to me for a ppk tune. The stock boost target will change with the weather/altitude. It will always target the same LOAD not boost.

My Peak is 9.4psi and I am getting around 8.4 of actual boost which seems low even for stock, isnt it? I am always testing at night when the wether is around 20 degrees celsius. Altitude is around 600m.

When I get back I will include the fueling values in the log as well. I didn't include them because before I removed the JB4 i had some logs and the timing, pressure - everything was fine.

I have ordered new sparknplugs (OEM for N55, Bosch) and I will install them when I get back to see if there would be a positive outcome.

Basically my MAF is okay then, with the values that it is reading? Or I got you wrong?

[weehe126]

That's normal boost

[bobbyggx]

So my log looks completely normal from Boost and Airmass point of view?

[AJL]

Originally Posted by bobbyggx

So my log looks completely normal from Boost and Airmass point of view?

Yeah, pretty much.

[bobbyggx]

Thank you! I measured the car on a Dyno and it produced 270hp on the crankshaft, that is why I started looking for a problem. I've replaced some o-rings (after pressurized Boost leak test there was a small leek from the O-ring between the charge pipe and the throttle body at around 20psi) cleaned the collector and the car feels a bit better, but I wasn't sure if it is a mind thing or there is an actual effect. Once I am back I would go and do another Dyno test to see if the stock situation is any better.

I will report back the results.

[roadcraftatx]

Hi guys,

Im running bm3 stage 2 in my N54, and I am having some issues with the boost target... I´ve been trying to increased it using different tables like boost limit, boost set limit, and boost multiplier with no success. I cannot get more than 8 psi of boost target. Any advice how to fix this? Thanks

[weehe126]

Originally Posted by roadcraftatx

Hi guys,

Im running bm3 stage 2 in my N54, and I am having some issues with the boost target... I´ve been trying to increased it using different tables like boost limit, boost set limit, and boost multiplier with no success. I cannot get more than 8 psi of boost target. Any advice how to fix this? Thanks

I strongly suggest you use the OTS tunes. This is the N55 section.