Can someone help me understand hysterisis table with regard EGR and Boost with regard EDC16 ecu.
When switching from one state to the other....feedback or not....what is the difference between the two states ?

I am familiar with the concept with petrols where lambda feedback is switched off and fueling tables are used.
Obviously this doesnt apply to diesels as such.

So can someone help me get my head around what happens with a thorough explanation.
Many thanks for any help.
:P

Anyone can help to explain this hysteresis table? :eh: :(

Thanks for the help ;)

For those that want to know....I will help you.
From what I can tell, you have the N75 tables, Boost tables and hysterisis tables that work together.
There are 3 boost tables.... each with an N75 table in mine.....but only boost and n75 map 3 are ever active.

OPENLOOP mode.
The turbo is controlled by the N75 wastegate tables only.
The ECU does not care how much boost this gives...only that the requested VNT/N75 duty is met.

FEEDBACK mode
The turbo is controlled by the PID controller.
The ECU looks up requested boost and compares to actual boost.
It closes the wastegate to increase actual boost and opens the wastegate to lower actual boost......whatever is required to get requested boost.
The initial wastegate value chosen come from the N75 tables and works from there.
So its best to get the N75 values as accurate as possible to begin with.

HYSTERISIS tables.
Selecting which mode the turbo should be in is the job of the hysterisis tables.
On mine 0-1500rpm @ 40mg + will swap from openloop to feedback.
Dropping below 38mg between 0-1500rpm will fall back into openloop mode.
Basically at low~ idle speeds the turbo is controlled by the N75 tables only.

You could set hysterisis between 40-38 mg down to 2-1mg instead.
This would force Feedback mode at all times.

You could set hysterisis to 100-98mg across the whole rpm range.
This would force openloop mode at all times.

I understand the PID controller updates a long term value tables.
Whether they take precedence I am unsure.

Is it possible that it's the other way around for hysteresis table? Lower injection quantity - > closed loop, after certain point (40mg for example) it goes open loop?

No, what Relic says is correct. For boost control: Low IQ --> Open loop, High IQ --> feedback.

For EGR hysteresis, I would say (not 100% sure):

Low IQ --> feedback mode using MAF as target and duty % taken from EGR duty table as initial value that is corrected by PID controller if actual MAF is different from target MAF

High IQ --> EGR not active

Thanks peeeece.

Relic wrote:I am familiar with the concept with petrols where lambda feedback is switched off and fueling tables are used.
Obviously this doesn't apply to diesels as such.
:P

Could someone explain how engine control system in turbo diesel cars work? When and what is going open loop and when and what is working in closed loop. I know that petrol cars are trying to achieve perfect AF ratio while in closed loop (using lambda sensor as feedback). What are diesel car trying to achieve in closed loop - what is their feedback? Are all types of maps used at all times?
I guess system goes open loop when there is greater demand for instant power (hard acceleration) and takes values from tables (maps) disregarding AF ratio (if it's even looking at that). This is just my tough based on observation - some cars give a lot of smoke while accelerating (harder) but otherwise (smooth driving) no smoke. Black smoke is consequence of not properly burned diesel fuel.
It would be really great if someone could explain all this or point to a document that explains it.

peeeece wrote:No, what Relic says is correct. For boost control: Low IQ --> Open loop, High IQ --> feedback.

For EGR hysteresis, I would say (not 100% sure):

Low IQ --> feedback mode using MAF as target and duty % taken from EGR duty table as initial value that is corrected by PID controller if actual MAF is different from target MAF

High IQ --> EGR not active

Yeah sorry forgot about egr.
:thumbup:

On mine the hysterisis table act like a switch to turn EGR on and off.
In feedback mode... the ECU cuts the actual MAF (say 1200mg) to the requested MAF in the EGR tables for that IQ vs rpm
(say 600mg)...by opening the EGR valve.
The EGR duty tables are used to calibrate the valve and make sure it gives the requested EGR MAF.
In openloop mode the EGR is off.... you get 100% of the MAF.
[Lambda should be locked to whichever is active]
[If requested EGR MAF is greater than actual MAF ....the valve will stay shut]

Using IBDII SAE to log "Requested EGR %" will give 100% MAF vs the EGR MAF as a percentage.
So this basically tells you "along with the current MAF" what the MAF would be with the EGR off.

zex24 wrote:Is it possible that it's the other way around for hysteresis table? Lower injection quantity - > closed loop, after certain point (40mg for example) it goes open loop?

I was logging boost in the two modes.
After taking ages to establish only N75 map 3 and boost map 3 were used....
at idle it was logged as openloop and the N75 table was 55% duty.....as was the log.
In feedback mode logged N75 duty was not the same as that in the N75 table....even with high speed logging.
But it appears there is only a small windows the PID can correct the boost so that requested boost = actual boost.

I am currently going through the process of N75 calibraiton at the moment.
I have lowered hysterisis to force feedback mode above 9mg.
I have locked 1st gear torque limiter at 10mg.
The attached is 5 consecutive attempts to fine tune the N75.... to make actual boost = requested boost.

Relic wrote:

peeeece wrote:No, what Relic says is correct. For boost control: Low IQ --> Open loop, High IQ --> feedback.

For EGR hysteresis, I would say (not 100% sure):

Low IQ --> feedback mode using MAF as target and duty % taken from EGR duty table as initial value that is corrected by PID controller if actual MAF is different from target MAF

High IQ --> EGR not active

Yeah sorry forgot about egr.
:thumbup:

On mine the hysterisis table act like a switch to turn EGR on and off.
In feedback mode... the ECU cuts the actual MAF (say 1200mg) to the requested MAF in the EGR tables for that IQ vs rpm
(say 600mg)...by opening the EGR valve.
The EGR duty tables are used to calibrate the valve and make sure it gives the requested EGR MAF.
In openloop mode the EGR is off.... you get 100% of the MAF.
[Lambda should be locked to whichever is active]
[If requested EGR MAF is greater than actual MAF ....the valve will stay shut]

What does it mean? How to loock lambda? On HDS now with EGR colosed, I have always Maf > target Maf on oem with open egr Maf folow nearly target maf.

EDIT

What does it mean? How to loock lambda?

On HDS now, with EGR colosed, I have always Maf (per one stroke) > target Maf. So should be shut.
On oem with open egr Maf (per one stroke) follow nearly target maf value.
If I want my current targhet maf follow the new values ​​how must I do?

I want to say first define a target then chase that target.
Now with egr closed chasing the target is the opposite,target maf track maf per one stroke