08 ECU Re-Learning

[Malu59RT]

On my first few cars (non-Viper), I was told that after putting mods on the car, I should un-plug the battery. Once re-plugged, the car would "re-learn" the new parameters. Is there any truth to this for the 08 cars?

When I un-plugged the car for a car show, I did get 200 miles on 1 tank (first time in 8000 miles) so I got slightly better fuel economy, and on the butt dyno, it actually did feel faster. I never felt anything when I pulled the mufflers, or when I put the K&N, but don't know if I should have unplugged the battery after each mod. Thanks in advance for the information.

Jason

 

[Grant]

The ECU is constantly adjusting the car's fueling under part-throttle conditions, based on feedback from the oxygen sensors. Any long-term trends in fueling correction (say for example your car always runs lean at 3000 RPM at 25% throttle) will be "learned" by the ECU and saved. Reseting the ECU may reset these parameters, but these only affect part-throttle conditions. At WOT, the ECU disregards any feedback from the oxygen sensors.

Cars with knock detection (which I think includes the '06 and '08 Vipers?) typically also learn and adjust for knock. If knock is encountered, ECUs pull timing, and may "learn" to adjust timing to avoid future knock. How this is done depends on the ECU. Many do it differently, and some don't do it at all. Reseting the ECU can clear any learned timing reductions due to knock. Since knock is generally only encountered at WOT, this typically doesn't affect part-throttle operation.

I wish I had more information specific to the '08 ECUs, but I'm not sure anyone does at this point.

 

[Racer Robbie]

For whatever it is worth i installed a K&N Filter-charger on my new 2008 Mazda Miata and it really screwed it up. The car ran like crap because the new '08 ECU had no way to adjust for the increase of air into the engine. K & N confirmed this on the phone and told me that mods on a '08 car can really screw up the drivabilty.

 

[Malu59RT]

Robbie,

Thankfully the 08 Viper's haven't had such issues with the K&N, which makes me think the stock filter isn't that restrictive, or the K&N doesn't allow that much more air to pass. I've heard without a filter at all, the car will set off a CEL.

 

[Racer Robbie]

After the screw up with the Filter Charger from K & N I went out and installed just a replacement filter, by K & N, in the stock air box. It did not mess up the ECM but I did not see any real gain over the stock OEM filter. Then I installed a Goodwin Racing full exhaust system including cats and there is where I got a huge seat of the pants boost in power with no problems with the ECM or codes produced. I therefor concluded that the new '08 ECM can not handle an increase of air in the intake but loves an open exhausts.