AFR Gauge

[Tinus89]

I'm also reading with a lot of interest Meinolf!

[Meinolf]

Hi,

 

I'm back from my trip to Vienna, so here we go. You asked for more details, so that's what you'll get in the same order as mentioned in the previous post. Several of the pictures will be based on a 5AM as used in my Norge 1200 2V and Mana just because that's my current area of interest. But the principles apply to the 15M/15RC as well.

 

Several of the pictures used are from this link: https://x-engineer.org/automotive-engineering/internal-combustion-engines/performance/air-fuel-ratio-lambda-engine-performance/because they are already with English text, the rest of the pictures are mine.

 

 

- the highest power is developed at Lamba 0.86 & the best efficiency is developed at Lambda 1.05

I guess this one is pretty self-explanatory. The highest power is developed, if all other factors incl. ignition timing are equal, at Lambda = 0.86.

- the min./max. correlation of NOx, CO and HC in relation to Lambda

Once again a rather simple correlation. A rich mixture causes high HC and CO emissions, a lean mixture comes with high NOx emissions. The 2nd picture shows the emissions if Lambda is set to 1.0, which is also the mixture at which the catalyst works best.

 

 

- the degree to which a given engine (at that time it was the V11 and the Jackal, currently a Norge 1200 2V, a Aprilia Mana, a Aprilia RST 1000, a Yamaha GTS1000 and a Yamaha MT01 are being logged and tuned)

Above sentence was incomplete. It should have finished with "...works well within a Lambda range." This combines a number of factors. The older engines such as V11 or Jackal were not (well) designed to run at Lambda > 1.0. They feel rough when operating in this range. This roughness can be mitigated by a) working on a smooth transition of mixture between the breakpoints. But the 15M/RC use 16x16 tables and lack sufficient resolution in the low load areas, both TPS and rpm. And by synchronizing the mixure (=Lambda) between the left and right cylinder.

 

- the throttling loss as measured with a MAP sensor

I've logged pressure in the intake with a MAP sensor. Once again a simple correlation. The TPS (Throttle position sensor) is exactly what the name suggests, a throttle. The more it's closed, the bigger the throttling effect. So why would one provide a rich mixture is the throttling effect is high. The %-values are in relation to absolute barometric pressure, 100% means almost not throttle lost, 30% is corresponding to a loss of 70% versus barometric pressure. Based on this a target Lambda table was created.

 

 

- histograms at which breakpoints and load areas > 90% of my actual road driving happens

The recent trip to Vienna was logged, ~ 5.25mio datasets  (Lambda le/ri, TPS, rpm) or 30h or driving time. No highways, just country roads, and my Lady was accompanying me with her bike. If driving alone the number of datasets at higher TPS/rpm would increase. Nevertheless, most of the driving happens at rpm's

 

https://drive.google.com/open?id=1YNHSYaxCZVnlrIGnu4MEnYfWGO6BJUVC

 

- considerations how the effect of ignition in relation to Lambda could be optimized. While the speed of mixture burning is quite constant regardless of Lambda, the deviation of actual mixture ignition in the combustion chamber varies +/- 20%.

 

Measuring Lambda/rpm/TPS is easy, the highest power is at Lambda = 0.86. But what about ignition timing and it's effects on power, roughness and emissions as well as pre-ignition and pinging? The literature states that the highest pressure in the ignition chamber should occur ~10-15° past TDC. The actual speed of the mixture burning after it's been ignited is quite stable, but the speed at which it ignites varies a lot with the mixture.

 

IF I knew which Lambda Guzzi (or Marelli) had in mind when creating the ignition tables and IF I'd reason to believe that they actually used data from a dyno for the respective models and IF all trim tables and factors were considered I could begin to 2nd guess how the ignition should be changed in line with the target Lambda table I'm using. However, the first two IFs are unknowns. And, as I don't have a dyno and the required measuring equipment at my disposal, it is a seat of pants area.

 

Cheers

Meinolf

[68C]

Thank you for helping us better understand the FI system.