Wideband lambda values with vag-com

[DuncS3]

Hi,

Have been looking at logging lambda values with Sita via vag-com, and on my chipped S3 have got these values from meas block 031:

rpm value
3720 0.906
3920 0.891
4160 0.883
4360 0.883
4560 0.883
4760 0.883
4960 0.891
5120 0.883
5320 0.883
5480 0.867
5640 0.883
5800 0.875
5920 0.821
6080 0.782
6200 0.75
6320 0.75
6400 0.758
6520 0.805
6640 0.828
6760 0.821

4th gear tickover to redline pull

0.75 at 6k or so is rich (the car is chipped) - supposedly I should be seeing 0.83. Anyone know about this enough to comment - I mean are the values I am seeing BAD?

Going to get some more figures tonight...

PS If you dont know and want to, this link helps:

http://www.mainlineauto.com.au/products ... on/afr806/

scroll to bottom of page for a chart

Dunc

[SunDiver]

Well, I'm a new S4 owner so not completely up on Audis yet but I also have a 250hp 1.8 turbo MX-5 with onboard wideband and full replacement ECU - it can even autotune (even under boost) via the wideband. Anyway, the values certainly aren't bad; bad would be if they were up near 1.0 or even over it (beyond stoich for petrol). It seems you're running down around 11:1 A/F ratio minimum thru' peak torque and slightly leaner at the top end; up to around 12:1. I don't know what a "good" value is for the S3 but FWIW, I run around 11.5:1 on the '5 at peak torque leaning out a tad to 12:1 at the top end. In other words pretty much where you're at with your map - perhaps a teensy bit leaner. General rule of thumb for turbo engines suggests your values for A/F to be pretty good. OEM Impreza maps often get as rich as 10:1 but they sacrifice power for safety. For me, my 11.5:1 gives a good reliable knock-free (the ECU uses a knock sensor too) map that runs year round regardless of ambient air temp. I do also have a huge FMIC too so that undoubtedly helps. Obviously it's a four cylinder 1.8 with a Garrett GT28 ball bearing turbo; different setup but it'd be close I'd offer. I'm no Audi guru but your map looks safely slightly rich rather than risky lean. Assuming of course that the WB is correctly calibrated. Additionally though I'm not aware of how effective the IC setup so the safely rich could well be appropriate.

As an aside, I have a portable wideband as well that I used to use before I had my downpipe drilled and tapped for a port. Out of curiosity I'd like to datalog my newly-acquired S4 but I have no intention of attempting any DIY tuning on it. Sounds like I clearly need to to order VAG-COM and look into what it can do.

A

[DuncS3]

Hi Sundiver - Vag com is a worthy investment for any VAG car - and thanks for your input!

Dunc

[S2tuner]

Dunc, what ECU is this? can you tell me the ECU part number that comes up with VAG-Com? It might not be wideband lambda...

Cheers,

Mihnea

[DuncS3]

Would this be the part number - taken from a vag com log?

8N0 906 018 BH

Its an 02 car

Cheers

[S2tuner]

Hi Dunc,

Ok then, it's a WBO2 indeed if it's from that ECU part number. The mixture isn't too bad, you can check in block 112 for EGTs and see what happens, if the mixture is being enriched by the ECU to keep EGTs down or not...

HTH,

Mihnea

[DuncS3]

Mihnea,

Appreciate your technical input greatly. Can you elaborate if you have time on what I should be looking for with regard to EGTs and fuel.

I thought 0.75 was on the max side of rich stoich (yeah I've read a webpage so got some jargon now!)

If you dont mind as a comparison here is a stock mode log of 031 Lambda:

0.93 3440
0.922 3640
0.899 3800
0.891 4000
0.906 4160
0.891 4320
0.883 4480
0.891 4640
0.883 4800
0.899 4960
0.883 5080
0.883 5240
0.891 5360
0.891 5520
0.883 5640
0.883 5760
0.867 5920
0.883 6040
0.891 6160
0.891 6280
0.867 6360
0.836 6480
0.813 6560
0.789 6680
0.805 6760
0.813 6800
0.844 6880
0.852 6960
0.906 7000

[S2tuner]

Dunc, the EGTs you should be reading in block 112 shouldn't exceed 920 degrees C. This is where the stock EGT limit is programmed, and if EGTs go above that, the ECU will dump more fuel in to keep the EGT sensor/regulation circuits inside of it happy.... This will also prevent your wideband O2 sensor from melting BTW

The ECU is programmed in stock mode to run as lean as possible without hitting the EGT limit, once it does so, it will enrich the mixture by itself. So, provided your MAF is ok and the EGT limit isn't exceeded, you could be basically running almost any fuel mixture at WOT, including 1.00


Cheers,


Mihnea

PS: do you still have the GT30R S3???

[DuncS3]

Thanks again - re the disco potato, thats Ryan isnt it?

Dunc

[DuncS3]

PS If my EGTs were above 920 degrees C, what would cause this? Natural thing I guess would be lean mixture but I'm seeing rich.

Dunc