[black e]

shockin330i started a thread about the torque dip in n55 a few days ago here:http://www.e90post.com/forums/showthread.php?t=482004
i speculated that it had to be a boost control issue and that the stock tune would spike boost on a dyno, (because it doesn't load the car like the real world does) then the DME pulls wastegate DC and/or closes the throttle blade to get the boost overrun under control , causing the big torque dip we see.
Well i decided to test this theory of mine on a dyno and show the results.
My car is a 2011 135i with the dual clutch trans (DCT) and has the following power mods (as of time of dynos):
PROcede v5 DCT1-5maps
Helix n55 FMIC
AA axelback
AR n55 catless DP
HP autowerks air filter
custom n55 charge pipe (for future meth bungs)

Now, this is 1 run in map1 and 1 run in map 0 within minutes of each other:


Here's the datalog from the map1 run:


This is the datalog from the map0 run:



Also note that, in the datalogs, CAN throttle and Throttle(pedal) are overlaid so that we can see when the DME is closing the throttle blade.
So, as we can see from the data logs, on map1 the boost goes up as expected, wastegate DC goes up normally as expected for whats needed to get the small turbo to try to keep up and the throttle blade has no closings. But in the map0 run we can see that the boost does overshoot and the DME goes nuts trying to correct it, it drops wastegate DC by a ton and it also closes the throttle blade even down to 35% opening....
So there you have it!

[black e]

93 views and no replies!
I guess everyone is speechless.... LOL

[Alessandro]

well done thanks for the info.

[atlharry]

As long as it only does it on a stock car on the the dyno, I've got no problems. It DOES illustrate the wastegate PID issues (a la Shiv's explanation) very well though.

Just to be fair, Mike/Terry has also brought that up as an issue.

Thanks for posting that up!

[FrankiE90]

sorry was mesmerized by
mr.5's "oil cooler" thread.

so it's boost control issue under dyno situations.
nothing traumatic to normal driving circumstances.

[Juiced46]

This is why I tell people to use a real loaded dyno, not crap unloaded dynojets. But have you logged it on the street to see if it is different?

[tscdennab]

So the N55 can't even be dynoed unless on a Mustang

By the way, do you see the dips on stock with no tune or are they always appearing on the Procede Stock map ? Maybe it's just a bug in the Procede bypass stuff. Not all values are 100% bypassed as far as I know.

[black e]

I'll post some street logs later today .
As far as I can tell almost every dyno that I've seen has the dip with the stock tune. There's a thread here that shows dyno runs of a car that gets flashed and the base runs were done on the stock tune (with the dip) and later on the flash (no dip) , so I would say is not procede related at all.

[Clap135]

6400 rpm, 10.5 psi, 93 percent duty cycle? You n55 guys are done untill single turbo upgrades come out. I am surprised bmw put such a shit turbo in there.

[Sniz]

Originally Posted by Clap135

6400 rpm, 10.5 psi, 93 percent duty cycle? You n55 guys are done untill single turbo upgrades come out. I am surprised bmw put such a shit turbo in there.

that is a shame, probably still an excellent street vehicle though.

[5soko]

Good info.

[IcebergM4]

Originally Posted by Clap135

6400 rpm, 10.5 psi, 93 percent duty cycle? You n55 guys are done untill single turbo upgrades come out. I am surprised bmw put such a shit turbo in there.

[jpsimon]

Originally Posted by Clap135

6400 rpm, 10.5 psi, 93 percent duty cycle? You n55 guys are done untill single turbo upgrades come out. I am surprised bmw put such a shit turbo in there.

luckily for them it should be A LOT cheaper to get a bigger single in there

[OpenFlash]

With the new maps I'm testing, we are 100% DC by 5500rpm

I'm still not 100% convinced the turbo is maxed out. Knowing BMW, i wouldn't be surprised if the wasegate rod is set super loose and can be tightened.

Shiv

[itsbrokeagain]

Originally Posted by shiv@vishnu

With the new maps I'm testing, we are 100% DC by 5500rpm

I'm still not 100% convinced the turbo is maxed out. Knowing BMW, i wouldn't be surprised if the wasegate rod is set super loose and can be tightened.

Shiv

This. BMW wouldnt have dumbed down the power THAT much. The turbine blade is less restrictive than one of the turbos on the N54, so it should be able to flow well.

[tscdennab]

It's truly disappointing. I really hope BMW will have a non-M twin-turbo I6 in the future, because when the time comes to get a new car I don't want to be without options.

[Clap135]

Originally Posted by shiv@vishnu

With the new maps I'm testing, we are 100% DC by 5500rpm

I'm still not 100% convinced the turbo is maxed out. Knowing BMW, i wouldn't be surprised if the wasegate rod is set super loose and can be tightened.

Shiv

I would be surprised, its pretty clear the turbo is out of steam, shame, but it is what it is. To drop 5psi and go up 50 percent in wgdc is a joke lol. Make you wonder where that turbo is on the map.

[Sniz]

Originally Posted by Clap135

I would be surprised, its pretty clear the turbo is out of steam, shame, but it is what it is. To drop 5psi and go up 50 percent in wgdc is a joke lol. Make you wonder where that turbo is on the map.

off the map lol

god how these engines would love a turbo that is at 50%dc at 15psi at redline.

I think the ECU would be like this

[shockin330i]

Originally Posted by Clap135

6400 rpm, 10.5 psi, 93 percent duty cycle? You n55 guys are done untill single turbo upgrades come out. I am surprised bmw put such a shit turbo in there.

Originally Posted by shiv@vishnu

Hi guys,
Quick update from today's testing:

2011 135
7DCT
15k miles
Provede v5 1-31 beta
Catless dp
Magnaflow cat-back
STOCK fmic
91oct Shell
Peak boost 14psi
5th Gear pulls



So as of a few days ago, we got around the fuel system limit that triggered a limp when trying to run more than 12psi above 5000rpm. Now we can basically run whatever the little turbo is willing to give me. In this case, it's a full 14psi up until 6000rpm. Above that, boost naturally falls off to 12psi. But without the fuel limitation, things became a lot more interesting. Especially at high RPM where the car makes considerably more power. Hopefully, we can make a solid 360whp when we install the FMIC. Because right now, datalogs show 120F intake temps at the top of 5th gear. Leaves a good deal of room for improvement.

On this dyno, my 135 put down 263whp/290lbft when it was stock. I'll have to dig up the file from the shop. Should have more info later this week.

Cheers,
Shiv

Its still a young engine

[shockin330i]

Originally Posted by maxnix

Yes, that has occurred to me also! And if one really wanted to retune, there is still the twin turbo option. Either can be sized up from the N54.

Eh, I'd rather stay with 1. AWD MS is currently working on a turbo upgrade for the n55. Should be awesome!

[Clap135]

Originally Posted by shockin330i

Its still a young engine

Young engine or not, you are out of turbo.

[black e]

Originally Posted by Clap135

Young engine or not, you are out of turbo.

there's many other platforms that can't really hold allot of boost up top with the stock boost control hardware ( solenoid/s, wastegate/s , DV/s ,ect) but that doesn't mean "the end of the road".
I've worked on a bunch of mzd speed 3/6 (also DI engines) and you can't get shit out of the motorcycle sized turbo with the stock hardware...but put a GM boost control solenoid with the correct resistor/s to match the OEM voltage and you can get the tiny turbo to hold 15PSI to redline....or take Evos on stock turbo, same problem , but change the OEM solenoid and/or OEM wastegate and they hold 23PSI to redline.
It might take some work but I'm sure we'll get more juice out of them.