Understanding Crankshaft duration and SOI

by **wicca** » Tue Jun 23, 2015 9:05 pm

Hi all,

have made my first mappings with succes (drivers wish, smoke map, torque map, removed EGR).
Made with VAG EDC SUITE (also have access to WinOLS, but find it quite heavy to use...)
Engine is a AVF 130 HP Passat from 2003, which now got 65 mg/stroke.
Target is to have a map that is economical until around 2200 RPM (that is around 120 km/h) for when driving on the highway (with cruise control activated), and become aggressive after this.
I am actually quite happy with the map now, performance wise... but want to look into making it more economic

I am trying to look into duration map, and the standard looks unlogic for me.
Can anyone explain why crankshaft rotation on mid area, is shorter to TopDeadCenter than both lower RPM and higher RPM.... my logic says it should be more like an incrementing line.... anything to do with emissions, efficiency, how it injects, etc... comments are very welcome :-)
What to be careful about?

Unfortunately I can not attach a Picture or file (it appears)... but as an example:

e.g. the row at 30 mg/stroke
5000 RPM 24,1 deg
4250 RPM 23,0
4000 RPM 22,5
3500 RPM 19,9
3000 RPM 15,8
2750 RPM 13,2
2500 RPM 11 <- whys is the range 2000-2500 lowest (makes no sense...)
2250 RPM 11
2000 RPM 11
1750 RPM 11,5
1500 RPM 12
1250 RPM 13
1000 RPM 13
and lower.. 13

Comments are welcome :-)

/Wicca

by **wicca** » Wed Jun 24, 2015 8:15 am

Posted numbers from a 0 degrees map, 90 degrees do not have those big numbers, but same tendency.
Nevertheless I have changed my map (same formula) big a little sharper timings + drivers wish map.
... will see how it reacts about it (last 2 days the CPU board have shown less L/km and a more steady cruise control... looks promising..

by **djwacik** » Thu Jun 25, 2015 7:26 am

Decalibrating stock duration maps is not a proper way of tuning.
If you want to tune for economy you should adjust SOI but do not forget that by disabling EGR you already advanced injection.

by **Anti** » Thu Jun 25, 2015 8:34 am

djwacik wrote:... by disabling EGR you already advanced injection.

So, one need retard boost in egr area to get less injectet fuel ?

by **djwacik** » Thu Jun 25, 2015 11:00 am

Fuel economy is not about injecting less fuel, it is about getting the most energy from injected fuel which in effect let you inject less but only using accelerator pedal (as it is the only fuel quantity adjuster in diesel engine).
To find best SOI you should use dyno.

by **wicca** » Fri Jun 26, 2015 11:25 am

First of all, thanks for your comments :-)

My idea was to advance the SOI timings, till I can hear it does not sound good anymore. Then postpone it a little again.
Might take some time of testing.

For now it has risen from between 15-17 km/l to more than 18 km/l, so I am on the right path... but I have not gone into detail mode yet as I do not have the knowledge of doing so...
Between 1750 RPM and 2250 RPM I focus on economy (SOI, duration, boost vs injection), after that it goes into aggressive mode.

What map do you combine to calculate the AFR the best... I find it quite more complex than expected as it variates on the original map (130 HP) depending on the RPM (and maybe other parameters as well...)

Boost map (I guess, could be calculated like this...)
AFR = (474 * (boost))/(mg/stroke)
e.g
AFR = (474 * 2,55)/65 mg
AFR = 18,6

Smoke limiter map... how is that calculated?

/Wicca

by **djwacik** » Fri Jun 26, 2015 11:30 am

Regarding calculating AFR - the only map where it could be done with is smoke map - airflow divided by permitted injection quantity is minimum permitted AFR (so richest possible mixture).

IMHO your way of tuning is not the best as you should just adjust it for performance (within fuel engine speed range) and then only at lower requested IQs (as requested by driver) you will find economy - SOI and IQs should be set to always deliver best performance that would give you maximum energy from fuel used by the engine so also maximum possible fuel economy.

by **wicca** » Fri Jun 26, 2015 11:57 pm

Nice comment, made me think..
Reason why I focus on the area, and not the whole map, is simply my lack of knowledge HOW to calculate the values.
If I do not have the theory right, then I have only practical feedback left (testing, testing and testing....)

Have attached the smoke limiter map, with some basic calculations (my adjustments + original 130 PS file)
How does that look in your eyes?

/Wicca

by **wicca** » Sun Jun 28, 2015 7:37 pm

Playing further around with SOI and duration (inspiration from other files and threads on this forum).

Original 130 HP map versus Modded map.
Original: Start to inject 4.4 deg before top dead center + 7.4 deg to burn it.. Means 3 deg after top dead center (helping the piston to push Down I believe)
Modded: Start to inject 6.5 deg before top dead center + 7.4 deg to burn it.. Means more fuel+compression build up, but less time afterwards helping to press the piston down again.

How is the relation for the best efficienty, focusing 100% on economy and 0% on emissions?
The modded file appears to be best economical wise (but I will test it more deeply with 1 week drive to work and home again...)

What is the best start of injection position and what is the best end of injection position? comments are more than welcome.. :-)

/Wicca

by **wicca** » Sun Jun 28, 2015 9:51 pm

Last question for today....
Looking on Duration selector (0-5, it is divided up in "maps").
E.g selector 5 is for all angles up to 4 degrees crankshaft rotation.
Looking on the SOI map and injection duration map, it starts e.g. with 10 mg at 1750 RPM, with 2,4 deg BTDC.
To this I add the duration which is 7.1 deg length
I end up at :2,4-7,1 = -4,7 (4.7 deg ATDC).

I think I have read somewhere that up to 3-4 deg ATDC is nice, and more is Waste.
Anyone know something about that?

/Wicca