How does the ECU learn?

[jamesm]

Originally Posted by ft_sjo

You can achieve that, though.

agreed you can, by adjusting all of the counters to 0 as described in mad_sb's post on the topic. i'm not convinced this is (or isn't) the best way to do it, but you can do it that way.

[ft_sjo]

Originally Posted by jamesm

agreed you can, by adjusting all of the counters to 0 as described in mad_sb's post on the topic. i'm not convinced this is (or isn't) the best way to do it, but you can do it that way.

Why aren't you convinced? The timers are there for emissions reasons, not driveability or power.

[arghx7]

Originally Posted by u/Josh

Thanks for the reply. I was under the impression that this car had an almost wideband O2 sensor and thus assumed that the car did target some values other than 14.7:1 under closed loop operation. Is that incorrect?

What are the reasons OEM dont use wideband sensors and closed loop under all conditions? Is it just the cost and life of the sensors?

Some OEM's do. BMW's run closed loop at full load enriched conditions, and their stock wideband o2 sensors are the same style of sensor used in aftermarket widebands. As for most other OEM's besides BMW, cost and development time is part of the reason why they don't bother. Most cars rarely run in full load/enriched conditions, and new engines have larger and larger areas of closed loop, Lambda=1 operation. Does the average Camry today really need that? Even GM is still running narrowband O2 sensors on their new direct injected V8's. It's a cost thing.

Sometimes though, if the engine is having trouble meeting CO emissions standards, the car will be designed to run closed loop under heavy load. But where you'll really see development focused on is going closed loop after engine start as quickly as possible (fast warmup O2 sensors) to meet emissions standards.

Originally Posted by ft_sjo

Why aren't you convinced? The timers are there for emissions reasons, not driveability or power.

They're there for emissions and fuel economy. If set up correctly from the factory they're not going to hurt anything, but we've seen some driveability issues in the past (like '08 Subarus). When making your own tune, it's a bit of a judgment call. Nobody wants to piss away fuel by immediately going rich, but good driveability and sometimes knock sensitivity are issues with too much delay.

[jamesm]

Originally Posted by ft_sjo

Why aren't you convinced? The timers are there for emissions reasons, not driveability or power.

i just don't understand it all well enough to know for sure if they're there for a reason other than those you stated. i agree it probably is fine, i'd just want to understand the whole picture more before making that call.

[arghx7]

Originally Posted by jamesm

i just don't understand it all well enough to know for sure if they're there for a reason other than those you stated. i agree it probably is fine, i'd just want to understand the whole picture more before making that call.

I've given this explanation in other threads. Here's how enrichment delay timers really started. When the vehicle is being certified for fuel economy and emissions for the US market, it has to be driven on the US06 cycle:



The cycle above is driven two times. The first time is a warm-up run, and the second one takes measurements of C02 (to calculate fuel economy), plus emissions. The most important thing here besides fuel economy is CO emissions. CO emissions are directly related to enrichment. So if I'm at Lambda=1 or 14.7:1 AFR on pure gasoline, my CO at the tailpipe is almost 0. The catalytic converter takes care of it.

If I have to work the engine hard though, the AFR will enrich first to keep the catalyst temperature down. It may also need to do so to protect for knock but usually the spark timing is ok for that. See that big acceleration at about 130 seconds? That and a few other spots are where the mixture is most likely to enrich to keep cat temps down. This applies especially to an engine with a poor low end torque or bad power-to-weight ratio (4 cylinder trucks for example).

The enrichment/open loop delay timers were developed and tuned so that the vehicle can get through these accelerations without adding more fuel than necessary. The timer counts up and might only add extra fuel for a small period of time. That helps fuel economy and CO emissions. Some cars stay in closed loop at heavy loads, but still have an enrichment delay timer. Subaru engine management is not particularly sophisticated though.

What can happen during development is that the vehicle is tuned a certain way by the driveability guys at the OEM. Then as it becomes time to certify the vehicle for emissions, the emissions guys lengthen the delay timer to meet a CO and/or fuel economy target. The cat temp and knock sensor readings are supposed to be in spec for durability. Sometimes what can happen though, and I think the '08 Subarus are a good example, is that the car gets pushed out to production meeting emissions but having a hesitation. The engineers weren't given enough time and resources to get the balance right, and you get pissed off customers. It's cheaper to tune the vehicle with a long closed loop delay than to redesign the engine with new parts that can satisfy fuel economy, performance, and emissions.

[jamesm]

well i guess that answers that.... thanks for the explanation.