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View Full Version : How overall timing and timing pull are calculated by the ECU(according to the bosch m



XXXX
12-29-2005, 10:04 PM
Originally posted by LA Wolfsburg on VWvortex

http://forums.vwvortex.com/zerothread?id=2363607

"i just read the bosch motronic manual and learned some new things.
lets start with the basics. (if you dont know what ignition timing is, http://www.howstuffworks.com has a great write up on it.) our ecus are load based, so when the motor is on, the ecu is directly manipulating the amount of torque the engine produces. so the ecu figures out how much torque it wants based on the reading from the pedal sensor (and some other variables), and then adds the amount of fuel and air required and calculates the optimum ignition angle to produce a large enough charge to make that amount of torque.
overall timing is calculated based on the following:
A twin three-dimensional table lookup that corrects the ignition timing angle for intake air temperature and is also a function of engine load, and engine speed.
+
A three-dimensional lookup that corrects for engine coolant temperature and is also a function of load.
+
The main timing lookup table which is a function of engine speed and engine load. On variable valve timing or variable cam lift engines this can be two or four tables that are representative of the state of the switchover. These timing lookups are the ones that are changed in performance chips. Bosch refers to these lookups as the base RON lookup tables.
+
A three dimensional lookup that corrects for air-fuel ratio and is also a function of engine speed.
+
Ignition timing adaptation values (what we fool around with using lemmiwinks)
+
Cylinder selective timing retardation. (IKC also known as timing pull/timing retard)
=
Ignition advance angle (*BTDC)
now none of this is really new stuff. what i was most interested in finding was how the ecu calculates IKC (timing pull). i originally made the assumption by looking at all of our logs that it was based on numerous variables, most importantly IAT. this was wrong. under normal operation conditions, timing pull is calculated based on the following variables only:
engine load
engine rpm
knock sensor voltage
now if youve seen a lot of logs, this doesnt seem to make much sense, since weve seen knock voltage be quite high with no timing pull. but its not the actual voltage we should be concerned with, its the variation in voltage. the noise signal detected by the sensors is compared to a reference signal that is obtained via a low-pass filter from previous combustion strokes. the reference level is therefore representative of the background engine noise when the engine is not knocking. the ecu compares how load the current combustion is compared to the reference signal and above a certain threshold, knock is assumed to occur. based on the size of the variation between current combustion and reference, the ecu adjusts the overall timing a specified amount for whatever cylinder is knocking the instant it detects knock. if knock continues, the adjustment becomes larger. when knock stops, the adjustment decreases a specified amount over a specified amount of time.
so when we log and see that knock voltage is high but there is no timing pull, the reason is that there is no knocking its just that the high knock voltage is normal engine noise. knock is actually represented by large, sudden increases of voltage (on a graph they would look like big spikes). im guessing that we rarely see these spikes because they happen so fast and most of us use data logging software with a really low sampling rate. never fear though, because timing pull will indicate whether we are knocking or not. if you see a small amount of timing pull, you are probably on the verge of knocking. if you see a large amount you are probably knocking. if the timing pull decreases over time, the adjustment stopped the knock and everything after the initial adjustment was fine. if your timing pull stays the same you probably were knocking and would continue to knock if the adjustment is taken away. if it increases, then you are continuing to knock. the maximum amount of timing that can be pulled is around 12 degrees.
so when logging, it is best to look at timing pull as opposed to knock voltage because most software does not have a fast enough sampling rate to display the knock voltage spikes. you also should not be looking at simply whether or not youre getting timing pull, you should be looking at when in the rpm range you are getting it, how large it is and whether it increases, stays the same, or decreases.
if you have any other questions about how the ecu works, i read the whole book so i probably know the answer.
"

one8t
12-30-2005, 09:56 AM
??????
Anything to add or just a REVO commercial?

k0mpresd
12-30-2005, 10:54 AM
Originally posted by one8t
??????
Anything to add or just a REVO commercial?
umm...what????!!

maybe you should try reading a book...

the info that was posted is from the bosch manual its how your ecu calculates load, timing advance, and timing pull...so the info posted is basically the info your ecu uses to calculate how much power youre going to make

EVIL-AUDI
12-30-2005, 11:00 AM
The only REVO reference I see is in his sig. Read it again.

XXXX
12-30-2005, 11:32 AM
Originally posted by one8t
??????
Anything to add or just a REVO commercial?
The guy that wrote the post on Vortex is running Unitronic.
How did you came up with this being REVO commercial?

one8t
12-30-2005, 02:45 PM
Amazing. The Bosch info is all great and wonderful, but it's like posting a page out of a Bentley manual. It's a reference book, it's not new or revolutionary. I read the book.

In terms of the REVO commercial, I am a df and did not realize it was his sig, tough to pick up, personally. After all the Bosch crap was posted, there are 3 quotes. The words Bosch or timing do not appear in the 3 quotes. What connection is there to these 3 quotes and the Bosch timing logic quote? 2 of the three quotes have bold print mentioning the superiority of REVO tuning. What the quotes are in response to, I have no f'in idea.

Sorry for the interruption!

94jedi
12-30-2005, 02:48 PM
Originally posted by one8t
Amazing. The Bosch info is all great and wonderful, but it's like posting a page out of a Bentley manual. It's a reference book, it's not new or revolutionary. I read the book.

In terms of the REVO commercial, after all the Bosch crap was posted, there are 3 quotes. The words Bosch or timing do not appear in the 3 quotes. What connection is there to these 3 quotes and the Bosch timing logic quote? 2 of the three quotes have bold print mentioning the superiority of REVO tuning. What the quotes are in response to, I have no f'in idea.

bro, you must be new to forum posting. That's his sig. [wrench]

k0mpresd
12-30-2005, 06:30 PM
Originally posted by one8t
Amazing. The Bosch info is all great and wonderful, but it's like posting a page out of a Bentley manual. It's a reference book, it's not new or revolutionary. I read the book.

In terms of the REVO commercial, I am a df and did not realize it was his sig, tough to pick up, personally. After all the Bosch crap was posted, there are 3 quotes. The words Bosch or timing do not appear in the 3 quotes. What connection is there to these 3 quotes and the Bosch timing logic quote? 2 of the three quotes have bold print mentioning the superiority of REVO tuning. What the quotes are in response to, I have no f'in idea.

Sorry for the interruption!
that made no sense @ all

LateraLex
12-30-2005, 08:19 PM
I found it interesting.