datalog vs reality

[dusterbd13]

attached is the data log from the most recent testing on my 7727 ecm equipped, TPI based small block mopar. I'm baffled. according to the sensor data, I'm running dead lean. according to plug reading and my nose, its incredibly rich. plugs are black and sooty after just a little run time, hard to start without opening the throttle considerably, and rich enough to make my eyes water.


I have no dead cylenders, and no observed leaks upstream of the oxygen sensor (heated 4 wire, bosch, located in drivers side long tube header collector.


so what am I missing? is it tuning, or mechanical? what should I check next?

I'm running AXCN $8d.

[dusterbd13]

the other baffling thing that may play into this, is that to get tunerpro to talk to the ecm, I had to use the 10k resister. from what ive been reading, this should not have to be used. I'm also getting lots of connection errors blinking during the datalogging.

[Eds]

Regarding the connection errors you are experiencing, I also had the same problem. I followed the Moates support info and the errors stopped. See attached.

http://support.moates.net/usb-driver...eshooting-101/

[bradyzq]

It's mechanical....ish.

You're running so rich that you're not getting a complete burn.

This means that some unburnt oxygen is making it into the exhaust, which reads as lean. Start leaning it out, and eventually you'll see the sensor flip to full rich, to match what you're seeing and smelling.

[steveo]

or it's actually running lean and the resulting misfires cause unburned fuel to enter the exhaust? really lean input can look a lot like really rich, as the unburned fuel can pool up, not fire, then burn rich/inefficient on subsequent ignition. i always have these guys say their car is running rich due to exhaust smell, i end up removing a ton of fuel to fix it....

experiment. go 20% richer and see what happens, then 15% leaner. you'll quickly figure out what direction to go in.

[bradyzq]

or it's actually running lean and the resulting misfires cause unburned fuel to enter the exhaust? really lean input can look a lot like really rich, as the unburned fuel can pool up, not fire, then burn rich/inefficient on subsequent ignition. i always have these guys say their car is running rich due to exhaust smell, i end up removing a ton of fuel to fix it....

experiment. go 20% richer and see what happens, then 15% leaner. you'll quickly figure out what direction to go in.

I have never seen a car with rich exhaust smell, lean O2 reading and sooty plugs require MORE fuel.

If it's actually lean enough to cause a lean misfire, there will be even more unburnt oxygen in the exhaust on the misfire, so it would show even leaner. And the plugs would be clean.

Additionally, when you open the throttle while cranking, you are letting more air into the engine, thereby leaning it out compared to cranking with closed throttle. Another hint that you are too rich.

[dusterbd13]

looking through the datalogs again tonight, I'm noticing that in open loop my oxygen sensor is either 450 or 0. no changes from those two, and 0 for most of it. ideas?

I'm going to burn a new prom shortly when I get this damn optispark on my buddys corvette replaced that ive leaned all the VE tables by 20%. (corvette was not planned. just showed up on a rollback today with a presumably bad ignition rotor. ran great, cut off. spark from coil to opti, but no fire at plugs. this is a miserable job, but should be over by Friday night)

also, should I lean out crank fuel based on the need to crack open the throttle?