PCLink "Statistics" page question - why is my Max Primary Inj DC reading > 100% there?

[Pete_89t2]

Subject is the question - how is it even possible for the injector's max duty cycle to be greater than 100%? This is with a G4+ Fury, in an FD RX7 that has primary & staged secondary injectors. Unless the number shown in statistics page is also adding the contribution from the secondary injectors to the primary % on the stats page?

My injectors seem to be operating normally, and I've never seen my primaries go beyond ~85% in the logs, and the secondaries stage in as they should. But today when I checked the Statistics page , I'm seeing "Max Primary Inj DC = 125%" after clearing all the stats a few days ago.

[Vaughan]

The statistics value shows the max calculated required injector DC, while your injectors can't physically be open more than 100% of the time your fuel settings can result in a calculation of more than 100% injector opening.

One commonish reason for overly high injector DC is excessive accel enrichment but only a log of the event happening would actually show it, note PCLogs may not pick up sudden sharp spikes in the fuel calculation but you could setup the ECU logging to log only when injector DC goes over a certain percentage.

[Adamw]

Have a look at max MAP as well, if you get a big backfire that spikes the MAP for example then the Inj DC will also be spiked proportionally.  The other common cause I have seen is if using modelled mode with fuel system type set to FP sensor, if the fuel pressure is low when you start cranking then the ecu will increase DC trying to achieve the correct fuel mass with no/low pressure. 

[Pete_89t2]

1 hour ago, Vaughan said:

The statistics value shows the max calculated required injector DC, while your injectors can't physically be open more than 100% of the time your fuel settings can result in a calculation of more than 100% injector opening.

One commonish reason for overly high injector DC is excessive accel enrichment but only a log of the event happening would actually show it, note PCLogs may not pick up sudden sharp spikes in the fuel calculation but you could setup the ECU logging to log only when injector DC goes over a certain percentage.

Thanks Vaughan, that make sense - I'll have to take a closer look at my logs, especially where the secondaries stage in. I could be briefly pushing the primaries past 100% when that initial staging "accel fuel" setting kicks in.

18 minutes ago, Adamw said:

Have a look at max MAP as well, if you get a big backfire that spikes the MAP for example then the Inj DC will also be spiked proportionally.  The other common cause I have seen is if using modelled mode with fuel system type set to FP sensor, if the fuel pressure is low when you start cranking then the ecu will increase DC trying to achieve the correct fuel mass with no/low pressure. 

Thanks Adam. The max MAP statistic is just slightly above my highest boost target, so no backfires. I am using modeled mode with fuel system type set to FP sensor, so that may be worth a look. The engine typically fires right off on the 1st crank, so I doubt fuel pressure is an issue. But now that I think of it, I did a rotary compression test recently, with the fuel injectors & ignition coils all temporarily disabled in PCLink. So in a case like that, and zero fuel pressure while cranking for the test (I pulled the fuel pump fuse to ensure no fuel), would the calculated DC% while cranking skyrocket and get captured in the statistics?

[Adamw]

8 hours ago, Pete_89t2 said:

would the calculated DC% while cranking skyrocket and get captured in the statistics?

I suspect that would be it.  

[Pete_89t2]

2 hours ago, Adamw said:

I suspect that would be it.  

Thanks, I'll just reset the stats again then & see what that results in after a few drives.