[zackz]

About the DDE, it's better to retune the wastegate actuator duty cycle map after porting the hole, in order to find a good compromise between low throttle lag and low overboost....

[pheno]

Originally Posted by zackz

About the DDE, it's better to retune the wastegate actuator duty cycle map after porting the hole, in order to find a good compromise between low throttle lag and low overboost....

Thanks. That's good to know. Have you done any logging with TestO by the way ? We're wondering here if label BPACD_rOut described as STAT_LADEDRUCKSTELLER_ANSTEURUNG_WERT, Tastverhältnis zur Endstufenansteuerung, is bigger turbo's wastegate actuator duty cycle.

[35d]

Originally Posted by pheno

Thanks. That's good to know. Have you done any logging with TestO by the way ? We're wondering here if label BPACD_rOut described as STAT_LADEDRUCKSTELLER_ANSTEURUNG_WERT, Tastverhältnis zur Endstufenansteuerung, is bigger turbo's wastegate actuator duty cycle.

I don't mind testing that for you of you want. Maybe by removing the vacum for the Wastagte and seeing if logs no value can help idetify if it is it. Got a few days before I get the car on the lift to sort the overboost issue out

[pheno]

Originally Posted by 35d

I don't mind testing that for you of you want. Maybe by removing the vacum for the Wastagte and seeing if logs no value can help idetify if it is it. Got a few days before I get the car on the lift to sort the overboost issue out

That would be fantastic and would serve many of us in the future thinking about the same :-) What comes to testing I'll let other guys to comment on that better. But your idea sounds reasonable. Now in the logs we can see that when duty cycle is going down, actual boost pressure is going up.

[pheno]

Originally Posted by iaknown

Hmmm, so who will be first to log it??

Maybe it would be worth to log this also with D73N57C0:

IALDS, STAT_LADEDRUCKSTELLER_ANSTEUERUNG_WERT, TrbCh_rPs, Ladedrucksteller - Ausgangstastverhältnis

EDIT: Ok, got a response from a guru at other forum which hopefully resolves all.

"PCR_rCtlVal is only the "set point" part of duty cycle. Real duty cycle that is sent to turbo is the result of "set point" and "boost pid controller" .

TrbCh_rPs is the output value of duty cycle that is sent to the turbo actuator (result of "set point" and "pid controller", as stated in other mail.).


Following the naming pattern, this must be duty cycle for LP turbo:

TrbChLP_rPs, Niederdruck-Ladedrucksteller - Ausgangstastverhältnis

[TDIwyse]

Originally Posted by iaknown

...
My logs show the stock wastegate holding the boost just fine through the entire range.

Hey iaknown, would like to compare logs of boost, boost set point and back pressure (http://www.e90post.com/forums/showpo...&postcount=211) to gain some insight on the relationship of how much boost we can push the LP turbo to at upper rpm's before the back pressure gets out of hand.

If the compressor map of the K26 we've been looking at is correct, it just doesn't seem reasonable to be pushing more than 3000 mbar at the turbo outlet (so less at the intake manifold due to pressure drop across the intercooler) at the upper rpm's. But if the drive pressure is still looking good at those higher boost levels, then I'm thinking I'll back off my wastegate controller and let it have more leash to make more boost before opening and dumping the pressure.

[pheno]

pheno, drive pressure is how much pressure is on the exhaust side of the turbo that drives the turbine which pushes the cold side air into the manifold .

TDIwyse, Follow-up to this.. any idea how ecu calculates and what sensors it needs to calculate this drive pressure ? Thanks.

[iaknown]

Originally Posted by 35d

I don't mind testing that for you of you want. Maybe by removing the vacum for the Wastagte and seeing if logs no value can help idetify if it is it. Got a few days before I get the car on the lift to sort the overboost issue out

The pressure converter(solenoid) won't know/care that the vacuum is unhooked. You're logging the electrical signal so the vacuum is irrelevant. What may be better is logging your good remap vs that experimental remap with the large dip when the wastegate opens too early. We should definitely be able to see the difference in duty cycle between those 2 maps.

[iaknown]

Originally Posted by TDIwyse

Hey iaknown, would like to compare logs of boost, boost set point and back pressure (http://www.e90post.com/forums/showpo...&postcount=211) to gain some insight on the relationship of how much boost we can push the LP turbo to at upper rpm's before the back pressure gets out of hand.

I was referring to my piggyback boost logs earlier but I can certainly log those parameters with TestO. Not sure when though as the weather is not looking good starting this evening...

[TDIwyse]

Originally Posted by pheno

pheno, drive pressure is how much pressure is on the exhaust side of the turbo that drives the turbine which pushes the cold side air into the manifold .

TDIwyse, Follow-up to this.. any idea how ecu calculates and what sensors it needs to calculate this drive pressure ? Thanks.

Yozh posted this: http://www.e90post.com/forums/showpo...9&postcount=63

There is an EMP (Exhaust Manifold Pressure) sensor already in the system. This should allow for a direct sensor measurement, which is what I "think" I was measuring on the log showing EMP to IMP ratio.

Regarding EMP to IMP ratio's, I came across this which says below ~2:1 is a good rule for a street driven vehicle ...

Taken from Maximum Boost by Corky Bell, page 169-170 :

Exhaust manifold pressure (EMP) will be called the only evil thing brought to bear by the turbo. The reason EMP is an undesirable quantity is the fact that it is always greater than the intake manifold pressure (IMP) generated by the turbo. When this occurs, a certain portion of the burned exhaust gas is pushed back into the combustion chamber during the cam overlap period.

It is this writer's opinion that a good street turbo system will show the ratio of EMP to IMP to be approximately 2. If a ratio of greater than 2 exists, the turbo is too small and choking the system down and not permitting much power gain. If the ratio is less than 2, often the boost threshold will be higher than desirable for commuter car use. This situation is offset by the fact that as the ratio comes down, power goes up. In fact, one of the design parameters of a race turbo system is that the EMP/IMP ratio be less than 1. When this crossover point is reached, where intake pressure becomes greater than exhaust pressure, a turbo can begin to make serious power. This is one of the reasons the 1987 Formula 1 racers could generate over 1000 bhp from 1.5 litres.

[TDIwyse]

Originally Posted by iaknown

I was referring to my piggyback boost logs earlier but I can certainly log those parameters with TestO. Not sure when though as the weather is not looking good starting this evening...

Yeah, weather sucks here too ... record lows again for overnight.

Curious as to others thoughts on the Corky Bell EMP to IMP ratio comment. If that's true I'm going to let more boost flow ... I'll try to get some logs of what happens to the EMP to IMP ratio as I dial the EWG back ...

[TDIwyse]

Originally Posted by TDIwyse

...
There is an EMP (Exhaust Manifold Pressure) sensor already in the system. This should allow for a direct sensor measurement, which is what I "think" I was measuring on the log showing EMP to IMP ratio.

And from the BMW Advanced Diesel Tech pdf

[pheno]

Originally Posted by TDIwyse

And from the BMW Advanced Diesel Tech pdf

Thanks. Good picture. So there is exhaust pressure sensor. Simple as that.

[zackz]

Originally Posted by pheno

Thanks. That's good to know. Have you done any logging with TestO by the way ? We're wondering here if label BPACD_rOut described as STAT_LADEDRUCKSTELLER_ANSTEURUNG_WERT, Tastverhältnis zur Endstufenansteuerung, is bigger turbo's wastegate actuator duty cycle.

I'm sorry, curently not enough time to do logs...

I will do logs after porting the wastegate and with the new remap

[zackz]

Originally Posted by pheno

Maybe it would be worth to log this also with D73N57C0:

IALDS, STAT_LADEDRUCKSTELLER_ANSTEUERUNG_WERT, TrbCh_rPs, Ladedrucksteller - Ausgangstastverhältnis

EDIT: Ok, got a response from a guru at other forum which hopefully resolves all.

"PCR_rCtlVal is only the "set point" part of duty cycle. Real duty cycle that is sent to turbo is the result of "set point" and "boost pid controller" .

TrbCh_rPs is the output value of duty cycle that is sent to the turbo actuator (result of "set point" and "pid controller", as stated in other mail.).


Following the naming pattern, this must be duty cycle for LP turbo:

TrbChLP_rPs, Niederdruck-Ladedrucksteller - Ausgangstastverhältnis

Yeap exactly, the DDE has a map for wastegate opening starting points, then with the help of the boost sensor, the DDE changes duty cycle of the actuator if the actual boost is lower/higher than the specified one in the boost map.

So, if you want a better throttle response, you can close the wastegate flapper a little more with the map, but the actual boost will be higher too just before the DDE reacts to open the wastegate, an overboost will happen during few seconds...

All is a story of compromises!

[DWR]

I have been debating whether to chime in here. But I thought something would be helpful. There are some incorrect assumptions about volumetric efficiency of this engine in the upper rpm range. For a fixed AFR, airflow will roughly follow horsepower. Look at TDIwyse's post http://www.e90post.com/forums/showpost.php?p=17366294
You will see horsepower falling after 4300 rpm. I'm told AFR is actually dropping in that region. So airflow is topping off, if not dropping, because volumetric efficiency is dropping - this is a diesel engine If you are wondering why we aren't off the compressor map, I hope this tidbit helps.

[TDIwyse]

Originally Posted by DWR

I have been debating whether to chime in here. But I thought something would be helpful. There are some incorrect assumptions about volumetric efficiency of this engine in the upper rpm range. For a fixed AFR, airflow will roughly follow horsepower. Look at TDIwyse's post http://www.e90post.com/forums/showpost.php?p=17366294
You will see horsepower falling after 4300 rpm. I'm told AFR is actually dropping in that region. So airflow is topping off, if not dropping, because volumetric efficiency is dropping - this is a diesel engine If you are wondering why we aren't off the compressor map, I hope this tidbit helps.

Thanks for the feedback and being willing to discuss this.

A/F ratio is falling, as is boost (due to the internal and external wastegates opening up). If it's OK to run ~3300 mbar boost at the upper rpm's, I can pull back the wastegate controller and allow more boost ... but I'm still not sure where the boundary is on how much boost at ~4500 rpm is OK. Based on the compressor map and calculations of Not2Fast, it seemed like ~3000 mbar (taking out a couple psi for intercooler loss) is just over the choke line ... unless one really lowers the efficiency of the turbo to ~65% (changing the efficiency really impacts flow).

What are your thoughts on the EMP to IMP ratio I logged? Does that seem like a reasonable operation region? Or do you think allowing a little more boost at 4500 rpm would be OK for turbo health?

Don't worry, I won't cast blame if I blow something up ... I am my own warranty/repair shop :-)

[DWR]

Originally Posted by TDIwyse

Based on the compressor map and calculations of Not2Fast, it seemed like ~3000 mbar (taking out a couple psi for intercooler loss) is just over the choke line ... unless one really lowers the efficiency of the turbo to ~65% (changing the efficiency really impacts flow)

I think 65% efficiency at 4500 rpm, for your vehicle, is too high.

[DWR]

Originally Posted by TDIwyse

What are your thoughts on the EMP to IMP ratio I logged? Does that seem like a reasonable operation region? Or do you think allowing a little more boost at 4500 rpm would be OK for turbo health?

That ratio is a rule of thumb and it is a measure of the system efficiency. It is based on things that can practically be measured. It cannot be supported, from an engineering standpoint, unless a handful of assumptions are correct. EMP is not a direct measure of drive pressure on the turbo, if there is back pressure after the turbo. Anyone measure that? However, EMP is a good indicator as to whether you might 'lift' a cylinder head - although I wouldn't worry too much in a diesel.

Measuring in and out temperature of the compressed air along with in and out pressure will tell you where you are on the map. If an industrious individual wished to share that data, I would be happy to share the calculation method and results with the group. So, yes TDIwyse we can get pretty close to predicting the rotational speed of the turbo. I think that is ultimately what you are asking, isn't it? BTW, the DDE calculates turbo rotational speed. When I get some time I need to see if there is a limit parameter (anyone else is also welcome to take a gander).

Don't worry, I won't cast blame if I blow something up ... I am my own warranty/repair shop :-)

I am not worried, I had you sign the release.

[DWR]

Originally Posted by DWR

I think 65% efficiency at 4500 rpm, for your vehicle, is too high.

If you didn't have the H20/Methanol injection to bring down the temps, you wouldn't be able to get as much air into the cylinders. Then the pressure would go higher. So those folks that are reporting these higher boost pressures, what are their IATs? Are we comparing apples to apples?

[TDIwyse]

Originally Posted by DWR

That ratio is a rule of thumb and it is a measure of the system efficiency. It is based on things that can practically be measured. It cannot be supported, from an engineering standpoint, unless a handful of assumptions are correct. EMP is not a direct measure of drive pressure on the turbo, if there is back pressure after the turbo. Anyone measure that? However, EMP is a good indicator as to whether you might 'lift' a cylinder head - although I wouldn't worry too much in a diesel.

Measuring in and out temperature of the compressed air along with in and out pressure will tell you where you are on the map. If an industrious individual wished to share that data, I would be happy to share the calculation method and results with the group. So, yes TDIwyse we can get pretty close to predicting the rotational speed of the turbo. I think that is ultimately what you are asking, isn't it? BTW, the DDE calculates turbo rotational speed. When I get some time I need to see if there is a limit parameter (anyone else is also welcome to take a gander).

I am not worried, I had you sign the release.

I had measured the back pressure previously (http://www.e90post.com/forums/showpo...7&postcount=60) using the built in differential pressure sensor. But this was with a partially clogged SCR (see posts after that one that shows partial clogging). With the partial clogged SCR the back pressure was ~9-10psi. I should repeat that with the fully open exhaust ... But we should then be able to know the turbo pressure from the EMP and then subtract the back pressure, correct?

Yes, the speed, or overspeed, is what I'm after... What job, or AssMod, is the turbine speed calculation? I'd like to log that.

[DWR]

Originally Posted by TDIwyse

But we should then be able to know the turbo pressure from the EMP and then subtract the back pressure, correct?

Yes, you are correct.

Yes, the speed, or overspeed, is what I'm after... What job, or AssMod, is the turbine speed calculation? I'd like to log that.

Not sure if it is LP or HP. I would guess it is HP because that is the one that could have a problem if some of the actuators fail. STAT_ASMod_nTrbCH_WERT, number 129 in MESSWERTTAB

Also OBD PID74 that may be dead, STAT_OBD_PID74_I15031_A_WERT