Harley-Davidson Closed Loop ECM Fuel Map Revealed

Exactly what does a typical ECM fuel map look like on one of the closed loop Harley-Davidson systems? Here is a chance to take a closer look at a typical emissions controlled fuel map just as HD provides them to their customers. It will give you a lot of insight into the inner working of Harley, EPA requirements and a better idea why Nightrider XiED's are as effective as they are on these bikes. This will show you the critical portions of the ECM fuel, bias and ignition maps for the 103 Stage 2 download and the Stage 1 download. The Stage 2 is the upgrade that includes the SE-255 cams, so it would be considered a mild performance upgrade. The Stage 1 Download is the upgrade Dealers push so hard for riders to get if they upgrade exhaust and air cleaner. Both these upgrades are valid 50-state legal modification.

For Riders with SERT, SEST or TTS, there is nothing new here. For riders that do not have a software tuner, the information can be quite interesting.

Most riders want to start with the Air Fuel Map, so here it is. Notice all the cells in 'red' with the 14.6 AFR in them. This is the indicator to the ECM to run in closed loop mode, looking at the O2 sensor to determine if the engine is running at the desired fuel mixture. You will notice that the engine stay in closed loop to 3750 RPMs and 80kPa. The HD engine used manifold pressure or engine vacuum from the MAP sensor to determine the actual engine load. There is not a one for one correlation between throttle position and the MAP sensor reading, but this range is basically up to around 40% throttle.

The main thing to notice here is that the majority of riding time, the ECM is in closed loop operating mode. The O2 sensor is controlling the fuel mixture 95%+ of the time for most riders. The AFR table for H-D Stage 2 103 and HD Stage 1 for the 96 CID engines are virtually identical. If Harley-Davidson's Stage 1 and Stage 2 AFR tables are identical, you can make a reasonable assumption that the OEM AFR table is going to be the same or very similar.

RPM MAP (kPa)
20 30 40 50 60 70 75 80 90 100
750 14.6 14.6 14.6 14.6 14.6 14.6 14.6 13.9 12.7 12.5
1000 14.6 14.6 14.6 14.6 14.6 14.6 14.6 13.9 12.7 12.5
1250 14.6 14.6 14.6 14.6 14.6 14.6 14.6 13.9 12.7 12.5
1500 14.6 14.6 14.6 14.6 14.6 14.6 14.6 14.6 12.7 12.5
1750 14.6 14.6 14.6 14.6 14.6 14.6 14.6 14.6 12.7 12.5
2000 14.6 14.6 14.6 14.6 14.6 14.6 14.6 14.6 12.7 12.5
2250 14.6 14.6 14.6 14.6 14.6 14.6 14.6 14.6 12.7 12.5
2500 14.6 14.6 14.6 14.6 14.6 14.6 14.6 14.6 12.7 12.5
3000 14.6 14.6 14.6 14.6 14.6 14.6 14.6 13.9 12.7 12.5
3500 14.6 14.6 14.6 14.6 14.6 14.6 14.6 13.9 12.7 12.5
3750 14.6 14.6 14.6 14.6 14.6 14.6 14.6 13.9 12.7 12.5
4000 13.9 13.9 13.9 13.9 13.9 13.9 13.9 13.7 12.7 12.5
4500 13.2 13.2 13.2 13.2 13.2 13.1 13.0 12.8 12.6 12.5
5000 12.8 12.8 12.8 12.8 12.8 12.8 12.7 12.6 12.5 12.5
5500 12.8 12.8 12.8 12.8 12.8 12.7 12.6 12.5 12.5 12.5
6000 12.8 12.8 12.8 12.8 12.8 12.7 12.6 12.5 12.5 12.5
7000 12.8 12.8 12.8 12.8 12.8 12.7 12.6 12.5 12.5 12.5

The closed loop bias table shown below provides the 'centering' voltage that the ECM will try keep the mixture at when operating in closed loop mode. At a value of 500, the AFR is 14.6:1. As the values approach 700, the AFR actually is closer to 14.3:1. This is at least .3 AFR richer than most riders think the fuel mixture of their bike is actually operating at. For these bikes, H-D is richening the mixture as the load on the bike goes up. But the ECM is actually doing this automatically. So while the engine is idling around 14.6:1, the engine spends much of its time running around 14.5-14.4:1 AFR based on the closed loop bias values placed in the tables. This first map is from the H-D Stage 2 download. Notice how HD very definately richens the mixtue by raising the O2 Bias Values as the RPM and Engine Load goes up. This adds a significant amount of fuel when the bike is moving, but keeps the AFR at 14.6:1 when the engine is idleing.

RPM MAP (kPa)        
  30.0 45.0 60.0 80.0 100.0
1000 506 506 525 584 603
1500 564 564 564 584 603
2000 603 642 642 603 661
2500 642 681 681 642 661
3000 642 642 642 642 661

This second bias table below is from the Stage 1 download. Notice that the bias values are considerably lower, keeping the AFR about 0.1 leaner than the Stage 2 fuel map. H-D is still keeping the bias values considerably higher than the 500 millivolt value of 14.6:1, but they definately are not richening the values as much as in the Stage 2 download.

RPM MAP (kPa)        
  30.0 45.0 60.0 80.0 100.0
1000 564 564 564 584 622
1500 564 564 564 584 622
2000 564 564 564 584 622
2500 584 584 584 584 622
3000 622 622 622 622 622

 

The Ignition Map is probably the least understood table for the engine. There is a series of cell in the map that form a sweet spot that the engine is under load. The ignition map 'under load' follows a different set of rules than when the engine decelerating. It is fairly obvious from the table below were the engine is really under load and where you are 'off throttle'. There are also a lot of concessions to emissions regulations in this ignition map. But as far as a general purpose ignition map that could be used in most street bikes, this map could be used in a wide variety of situations.

 

RPM MAP (kPa)
20 30 40 50 60 70 75 80 90 100
750 18.0 18.0 18.0 18.0 11.0 10.5 7.0 -1.0 -4.0 -4.0
1000 18.0 18.0 18.0 18.0 11.0 10.5 7.0 0.0 -4.0 -4.0
1250 18.0 18.0 18.0 18.0 12.0 11.5 8.0 1.0 -4.0 -4.0
1500 18.0 18.0 18.0 18.0 14.5 13.0 10.0 2.0 0.0 -1.0
1750 20.0 20.0 19.5 19.0 18.5 16.0 12.0 8.0 5.0 2.0
2000 24.0 24.0 23.0 22.5 22.0 20.0 17.0 12.0 7.5 5.5
2250 29.0 29.0 28.0 27.0 26.0 24.0 21.0 16.0 11.0 9.5
2500 33.0 33.0 33.0 32.5 31.0 28.5 25.0 20.0 14.0 12.0
3000 38.0 38.0 38.0 38.0 38.0 33.5 29.0 22.0 16.0 14.0
3500 43.0 43.0 43.0 43.0 43.0 37.5 31.0 23.0 17.0 15.0
3750 45.0 45.0 45.0 45.0 45.0 40.0 32.0 24.0 18.0 15.0
4000 45.0 45.0 45.0 45.0 45.0 41.0 34.0 27.0 20.0 16.0
4500 45.0 45.0 45.0 45.0 45.0 41.0 36.0 30.0 23.5 19.0
5000 45.0 45.0 45.0 45.0 45.0 42.0 38.0 33.0 26.5 22.0
5500 45.0 45.0 45.0 45.0 45.0 42.0 39.0 35.0 30.5 26.0
6000 45.0 45.0 45.0 45.0 45.0 42.0 40.0 37.0 33.0 29.0
7000 45.0 45.0 45.0 45.0 45.0 42.0 40.0 37.0 34.0 31.0

The HD Stage 1 Ignition Map is listed below. It is very obvious that this map is more aggressive, with more advance. The exception is in the higher RPM, off throttle situations. The reason for this is generally to help reduce decel popping.

RPM MAP (kPa)
20 30 40 50 60 70 75 80 90 100
750 24.0 24.0 24.0 24.0 20.0 14.5 8.0 4.0 1.0 1.0
1000 24.0 24.0 24.0 24.0 20.0 14.5 9.0 5.0 2.0 1.5
1250 24.5 24.5 24.5 24.5 21.0 15.5 10.0 6.0 3.0 2.5
1500 25.0 25.0 25.0 25.0 22.0 17.0 12.0 7.0 4.0 3.5
1750 26.0 26.0 26.0 26.0 23.5 20.0 16.0 11.0 7.0 6.0
2000 27.0 27.0 27.0 27.0 25.5 22.5 19.5 15.0 10.0 8.5
2250 29.5 29.5 29.0 29.0 28.0 26.0 23.5 19.5 13.5 11.5
2500 32.5 32.5 32.0 32.5 31.5 30.0 27.0 23.0 16.0 14.0
3000 34.5 36.3 36.0 36.5 35.5 33.0 30.0 26.0 18.0 16.0
3500 35.0 38.8 39.0 39.0 39.0 37.0 33.5 28.0 19.0 17.0
3750 35.0 40.0 42.0 42.0 42.0 40.0 35.0 29.5 20.0 17.5
4000 35.0 40.0 43.0 43.0 43.0 41.0 36.0 30.0 20.5 18.0
4500 35.0 40.0 43.0 43.0 43.0 41.0 36.0 30.0 22.5 20.0
5000 35.0 40.0 42.0 42.0 42.0 39.0 35.0 30.0 25.0 22.5
5500 34.5 39.0 41.0 41.0 41.0 38.0 34.0 30.0 26.0 23.5
6000 34.0 38.0 40.0 40.0 40.0 38.0 33.5 30.5 27.5 26.0
7000 34.0 38.0 40.0 40.0 40.0 38.0 34.0 31.5 29.0 28.0

I hope this brief look at some portions of the ECM tables, namely the AFR map, the bias tables and the Ignition Advance map for the Harley-Davidson Stage 1 and Stage 2 bikes will provide some inside into how your own bikes ECM is set up. I am not trying to explain EFI and Dyno tuning here, just show what H-D did or has not done with their downloads.

The specific SERT Maps used to show this information was 200UH001-A1.MT6 (SE Stage 2 103 + SE-255 Cam) and 200TD001-A1.MT6 (SE Stage 1 TC96).

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