I'm logging my 996tt x50 for the first time using a friend's Durametric. I'm a long time datalogger of Audi's and VW's, so in general I'm very familiar with this stuff, just haven't done it on the 911 until now.

This is a 3rd gear WOT pull.

While logging, I noticed my A/F is very rich.

1.) What's normal A/F for this car? anyone have data/graphs they can point me to?
2.) What are likely causes leading to an overly rich condition like this?
- Boost leak after the MAF?
- Are my MAF readings high too?
- I'm assuming injector duty cycle shouldn't be near 100% (I'm stock) and is likely a result of MAF reading more air than is actually going into the engine and thus adding more fuel to match, but in reality adding too much since the air's not all going in.
3.) I suspect I'm hitting the limit on the O2 sensors at 0.73 (meaning I could be even richer) - is that in fact the limit that can be recorded?

Red lines are from this log (pink was from prior log with less variables recorded)...

0.8-0.9 bar on my stock x50 - I assume this is normal:


Not sure what normal MAF readings are for this car (ignore the g/s in the legend, that's from a template for a different car):



I assume I'm way too rich here and that I'm hitting a sensor limit at 0.73 and thus might be even richer in that stretch:


and here's the injector duty cycle:



Any help appreciated. I'm sure there's not many people with stock x50's that have logged them, so any close data would help.

I did have some hoses come loose previously, but were fixed by a good local shop. Perhaps one came loose again. Do folks here use a pressure testing rig to check for leaks? Is there a good connection spot near the maf? Again, I previously did so on Audi/VW and that worked well for finding such leaks.

Here's the full set of graphs for those interested (I wanted to keep focus above):
http://ctny.audiworld.com/mark/996tt...ple_rate_test/

Thanks,
Mark

 

I don't know if my Durametric data will help?

I remember testing my injector duty cycle as 83% max at 4900rpm.

UK 2002 X50 with Milltek exhaust & 200 cel cats

3rd & 4th gear WOT run:-

RPMEngine loadIgnition angleOxygen sensing, bank 1 Lambda ValueOxygen sensing, bank 2Boost pressure of sensor140640.87211.020.991003.2146655.0521.75111003.24156572.0920.250.970.991005.85170173.2820.250.981.011029.25179375.53210.990.991045.5192185.89210.981.011057.69210899.4220.250.990.971135.97232110819.50.960.971229.022559116.4320.250.980.951330.782826132.23180.980.9714653095146.513.50.921.011622.53442154.3511.250.851.011695.463792161.789.750.761.011726.254143169.759.750.741.011722.264474174.9610.50.751.011738.864814175.510.50.761.011731.365165168.3712.750.761.011751.175420162.35150.7511763.755732158.115.750.770.991776.876000144.23180.790.971808.286246135.4920.250.7711827.466509134.2922.50.780.991826.56632949.810.50.9812099.49change to 4th gear5148107.1519.50.7711064.725433160.4715.750.771.061861.445623164.15150.7511837.695745154.3815.750.7611809.375909150.8215.750.770.981823.716061143.6915.750.80.991824.336211138.8619.50.790.991834.45617820.3417.251.0111790.42607216.7821511201.36582116.5417.25511114.17561316.5216.5511082.5535815.6518.75511069.25508415.619.5511058.71449416.4218.75511048.12315016.1913.5511042.81202519.54-2.25511032.3

 

Those data look reasonable to me, EXCEPT for the injector duty cycle.

The boost is about 1 bar, MAF is about 1350, AFR is a tad low, but that's on the safer side. The injector duty cycle at 100% is worrisome. I would recommend that you check over the fuel system. One possibility is that you have a leak in your fuel pump, which a lot of guys have had. It's a split hose inside the fuel tank, at least it was for me. Could also be a loaded fuel filter.

Jon

 

I don't know if my Durametric data will help?

I remember testing my injector duty cycle as 83% max at 4900rpm.

UK 2002 X50 with Milltek exhaust & 200 cel cats

3rd & 4th gear WOT run:-

RPM.doc

 

Could you email me your excel file to me so I can graph it? Thanks!

 

Kenco911, Oh, nevermind, I see you posted the .doc while I had started to reply. Thanks. BTW, you're log captures two different things for Bank1 and Bank2:

Oxygen sensing, bank 1 Lambda Value <--- This is true wideband A/F
Oxygen sensing, bank 2 <--- Not sure what this is???

Not positive, but I would guess that maybe you intended instead to log this:
Oxygen sensing, bank 2 Lambda Value

 

MarkP,

Any joy with your fuelling issue?

 

I haven't had a chance to look much more into it, however I did log Specified and Actual A/F to see what the ECU was asking for. Indeed the car is running richer than requested:




I don't have enough experience logging these cars yet to know what's normal, but on my VW (which also has a wideband) I'd wouldn't expect to see that discrepancy from 4000-5500. It's not going to be exact match, but should be much closer. Also it seems 0.73 lambda is the minimum reading on the sensor, so from a general/practical standpoint, the car shouldn't be operating at the limit of any sensor, so that doesn't seem right either.

I did check and I have no fault codes, so apparently if there is an issue, it's not bad enough to trigger a code.

As an aside, here's old data from my VW (and also using logging software with a much higher sampling rate which I wish durametric could also achieve). If you squint, you can see each actual is following the desired much more closely:


to be continued...

 

Your data don't look too bad. As for running rich my first guess would be your plugs rather than a post MAF leak. You're holding boost very well and matches requested value.