[VegasG42]

Speaking of how the stock factory ECM adjusts to an increase in exhaust flow from the turbo exhaust outlet.

Is this something that the ECM is constantly having to adjust for ? Or does the increase of exhaust flow from a high flow catted DP fall within the air/fuel ratio parameters of what the car allows ?

In other words - will the car ever run rich or lean with the addition of the HFC DP, or will the car adjust to a correct ratio ?

Or is a tune required to get everything correct ?

[VegasG42]

Maybe I made the question too longwinded.

Will the AA catted downpipe ever cause your car to run rich or lean ?

[rons e92]

I'm theorizing here so someone can correct me if im wrong, but don't think it matters.

The DP likely reduces exhaust back pressure, which will potentially increase the max RMP of the turbine slightly, however being that the car runs a MAP sensor it'll know that and add more fuel.

The DP doesn't add capacity to the turbo chargers to force more air. It can spool quicker via reduced back pressure in the OEM cat, but again the MAP sensor would see ther and add fuel consistent with the stock mapping.

My G42 had an Active DP and when watching AFRs with mt JB4 I never really say anything out of the ordinary. I have Actice DPs on my G87 and although I went Racechip this time around I don't smell fuel like it's rich and it certainly doesn't seem to be running lean.

[Littlecoupe]

I haven't looked under our cars, but most modern vehicles have a post-cat O2 sensor. The fuel system will account for the MAP/MAF and O2 sensors to ensure the correct A/F ratio is maintained. Boost would be controlled by the electronic wastegate.

I can't imagine our engines would be tuned in a way to allow A/F to go too out of whack without setting off an error in the gauge cluster. Running rich or lean should be detected by the post-cat O2 sensor. No errors, then no issue.

I can attest to the sensitivity of our A/F ratio sensing in the B58. I had a BMS intake on my F22, the one that sits in the lower half of the airbox, any my car threw a MIL/CEL during a -35C cold snap we had for over a week. I think since the air was so cold and dense, the open intake was causing the fuel system to account for the increased density by adding more fuel. The code I had at the time was something about exceeding specified fueling parameters, I think it was dumping in more fuel to account for the air mass.

[tagoo]

I know that many computerized vehicles can adjust the airflow mixture within a certain range during closed loop operation(partial throttle). However, those same vehicles revert to an air/fuel/timing table for open loop (full throttle) operation. Such vehicles could see accurate air/fuel mixture during close loop, but see a lean condition at full throttle because the air/fuel/timing table is static at wide open throttle. Not sure if the B58 operates the same way - I suspect it does.

[VegasG42]

Perfect . Thank you for the replies.

This falls inline with what I figured how the correct A/F ratios are maintained. The slight increase in turbo spool speed with the increase in exhaust flow, would be matched and automatically adjusted by the ECM.

Same way the car would automatically adjust for cold or warm weather , or humid climates, or change in elevations geographically.

[VegasG42]

Originally Posted by tagoo

I know that many computerized vehicles can adjust the airflow mixture within a certain range during closed loop operation(partial throttle). However, those same vehicles revert to an air/fuel/timing table for open loop (full throttle) operation. Such vehicles could see accurate air/fuel mixture during close loop, but see a lean condition at full throttle because the air/fuel/timing table is static at wide open throttle. Not sure if the B58 operates the same way - I suspect it does.

I would imagine if the G42 uses a static A/F mapping table during WOT, there would still be a built in bit of variation to the mapping , for external factors such as weather, elevation , clean or dirty air filter, etc

[VegasG42]

And as others have said previously - WOT Dyno runs with an installed catted downpipe didn't reveal any problematic A/F ratios

[RockCrusher]

Originally Posted by VegasG42

Maybe I made the question too longwinded.

Will the AA catted downpipe ever cause your car to run rich or lean ?

See no mention of the fitting of this hardware requiring a "tune". The info at the web site claims it will not affect emissions. But is *not* legal in CA!

Link:

https://store.activeautowerke.com/pr...atted-downpipe

As others have touched upon the engine controller has some leeway to adapt to changes in factors that can affect fueling. Within reason the ECU can adapt with no error code. If the adaptation goes too far though a CEL will be triggered with (probably) a too rich or too lean error code.

Have to stress it is important this hardware be installed with *no* leaks. A leak can result in a CEL that might suggest a tune is required but it is just a bad installation.