05 Corvette Lean issue..

[DavidMcgwier13]

I am new to tuning so please be understanding with replys. I am working on an 05 Corvette fresh motor 6.2L with a fairly large cam. I have gone trough the tune many times and cant seem to get the car more fuel. My fuel trims will start out low then after a while they climb and will not come back down. I have tried to recalibrate the MAF and PE tables via "The Tuning School" guides. Ive updated the injector flow rates and scaned the car several times. I thought maybe there was a vacuum leak but cant seem to find it. Pulled a plug to check it the old school way, the plug reads lean... very lean. Where have I gone wrong?

[wetcoast]

Long tube headers?

[DavidMcgwier13]

Long tube headers?

Yes.. Also someone else tuned this car before I got it.

[wetcoast]

From what I've gathered the general consensus seems to be that long tube headers move the narrow band O2 sensors from their original locations in the stock manifolds. This has a couple of 'side effects'.

First, when you move the NBO2 away from the cylinder, it doesn't get as hot as the stock location which skews the NBO2 voltage slightly. Here's a graph of the difference, I can't speak to the accuracy of the test data but it gives you the idea.

3_narrowo2_afr.gif

Secondly, the ECU uses the Closed Loop Airflow and Closed loop integrator delay to adjust the amount of fuel injected to induce NBO2 switching. When you change the location of the NBO2 the time it takes from injection to response at the NBO2 is different and thus confuses the ECU into thinking the fuel isn't responding and it adds or subtracts more fuel.

You'll likely notice that the LTFT and STFT are all way off the VE you would expect if tuned with your wideband.

This is as much as I've gathered in my reading. Take it for what it's worth.

[DavidMcgwier13]

From what I've gathered the general consensus seems to be that long tube headers move the narrow band O2 sensors from their original locations in the stock manifolds. This has a couple of 'side effects'.

First, when you move the NBO2 away from the cylinder, it doesn't get as hot as the stock location which skews the NBO2 voltage slightly. Here's a graph of the difference, I can't speak to the accuracy of the test data but it gives you the idea.

3_narrowo2_afr.gif

Secondly, the ECU uses the Closed Loop Airflow and Closed loop integrator delay to adjust the amount of fuel injected to induce NBO2 switching. When you change the location of the NBO2 the time it takes from injection to response at the NBO2 is different and thus confuses the ECU into thinking the fuel isn't responding and it adds or subtracts more fuel.

You'll likely notice that the LTFT and STFT are all way off the VE you would expect if tuned with your wideband.

This is as much as I've gathered in my reading. Take it for what it's worth.

Thank you for the info.. I'll see what I can do to correct it.

[Eaglegoat]

Only tune with a wideband. Then make adjustments to your narrow band settings so they react appropriately.

Also that test isn't exactly indicative of what happens with narrowbands. They are heated o2 sensors. They have a heat control circuit. That doesn't mean they can adjust to anything but they are adaptable (think artic circle to death valley). The biggest changes are going to come from the integrator delay table, then your o2 switch voltage, then your proportional fueling, IMHO.