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View Full Version : AFR Behaviour. Some advice is welcome



eliotroyano
27th May, 2016, 02:30 PM
Hi friends. I need some advice about what can cause a weird issue. This problem is from a VAG 1.8T drive by cable petrol based engine with M383 ECU. The problem is a sudden AFR step down that occurs after boost ramp finish. All hardware was checked many times without any issue or leak.

The attached pics shows you , AFR(purple), boost (blue), RPM (black), EGT (red) & oil pressure (green) of my datalog system. In these pics I have remarked a zone where AFR changes abruptly (almost -1.0 AFR) aprox. in the same area all time under boost. Also attached are some log extracts from a bigger log. In general max load barely pass 10.5ms.

Log1 --> http://i66.tinypic.com/fqu0g.jpg
Log2 --> http://i66.tinypic.com/2vxq03o.jpg
log3 --> http://i66.tinypic.com/2r5gcom.jpg

Then do you know or have seen that kind of behaviour before? What could cause it?

eliotroyano
30th May, 2016, 06:38 PM
Any ideas friends?

koira
31st May, 2016, 06:34 AM
Fuel pressure regulator?

eliotroyano
31st May, 2016, 12:57 PM
Fuel pressure regulator? I have tested it and also test others FPR and same issue.

mexanico1971
31st May, 2016, 01:07 PM
What"s your target for AFR ?
I don"t know everything , what is M383 ECU ?
is this OEM set up ?

BRs

xirtam
31st May, 2016, 02:43 PM
RPM ----> Target AFR ------>Log AFR knock? VE?

OVERSPEED
31st May, 2016, 04:21 PM
Try lowering FGATO as I said before...don?t trust only in LTFT to adjust it

eliotroyano
31st May, 2016, 08:53 PM
What"s your target for AFR ?
I don"t know everything , what is M383 ECU ?
is this OEM set up ?
BRs
It is a big turbo setup for a 1.8T AGU drive-by-cable engine with 06A906018CG M383 ECU. AFR Target is 11.75:1 from 4000+rpm.


RPM ----> Target AFR ------>Log AFR knock? VE?
Max knock retard is -2?.


Try lowering FGATO as I said before...don?t trust only in LTFT to adjust it
Junior I tryied in little steps but all the time AFR suddenly step down. Until how much should I lower FGAT0, LTFT +20%? I do not want to compensate for the AFR step, as you saw in past, I will like to know what cause it.

OVERSPEED
31st May, 2016, 10:30 PM
+20% LTFT is wrong indeed... but AFR goes to same value ?

eliotroyano
1st June, 2016, 02:16 AM
+20% LTFT is wrong indeed... but AFR goes to same value ?
No, but just change a little.

xirtam
1st June, 2016, 04:32 AM
MAF may need Rescale

eliotroyano
1st June, 2016, 06:01 PM
MAF may need Rescale
I am using complete VR6 OBD1 MAF (housing + sensor) with it associated MLHFM map.