Injector Pulsewidth "Bottoms-Out" at 2.3ms

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01-11-2016
jlpearl

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Injector Pulsewidth "Bottoms-Out" at 2.3ms

Hi All, I'm a long time lurker and infrequent writer.

I am currently tuning a '04 Silverado SS with a 408, big cam (spec sheet included), 3bar SD, 60lb Deatschwerks injectors at 48psi, and a single turbo. I am having trouble getting the fueling correct at idle. If I drop the VE table to something <= 25, the LTFT and STFT will max out and get me around 14.1 on my wideband. I expect I have issues with my injector data, but I got the data directly from DW. In this tune I did halve the injector voltage offsets to see if it would drop the pulsewidth below 2.3ms, but it did not make a difference.

This is a return style fuel system, so I copied the 0kPa column across for voltage offset and set a constant flow rate. I have attached the latest tune and data log. The truck starts and idles well but achieving proper lambda and transient behavior has been difficult. I changed the transient fuel to .002 per information I saw here, but there seems to be something else that I am missing. Any thoughts would be greatly appreciated. Thanks!
01-12-2016
jlpearl

It looks like the problem was related to the MAF DTCs not being turned off correctly. I made the adjusted to 0 - MIL on First Error and the behavior in open loop is MUCH better. I'll report further if this is not the fix.
01-14-2016
KFZ)^

Are you aware of what the minimum injector pulse is for those?

Injector flow rate is not "flat" just because the fuel system is return style. Intake manifold pressure still influences flow rate.

I suspect the injector data.
01-15-2016
schpenxel

Is the regulator boost / vacuum referenced or no?

Also remember the reported inj PW on gen 3 vehicles is the actual electrical PW. So, base PW + offset + short pulse adder.

(Also, good God look at that knock)

I also saw them go down to 2.1 msec in one spot
01-16-2016
KFZ)^

Quote:

Originally Posted by schpenxel

Is the regulator boost / vacuum referenced or no?

Also remember the reported inj PW on gen 3 vehicles is the actual electrical PW. So, base PW + offset + short pulse adder.

Good points/questions. Hopefully jlpearl is making progress and will let us know how it's going.