[greenskeeper79]

When coasting, in gear, what rpm do your injectors start firing again?

 

[klhansen]

Not sure I've ever noticed a specific RPM. I believe the injector shutdown is based on actual engine load. Going down a slight grade in a lower gear is the only time I really notice it.

 

[greenskeeper79]

Not sure I've ever noticed a specific RPM. I believe the injector shutdown is based on actual engine load. Going down a slight grade in a lower gear is the only time I really notice it.

If you are in gear and coasting, and let the truck slow down on it's own when do the injectors start firing again? Is it when the truck reaches idle speed? A higher rpm than idle?

The reason I ask is I swapped PCMs, from an E99 manual PCM to an 00 auto PCM. However I am running a hydra chip with tuning for a manual PCM (DAC3 on a DPC422 PCM)

Prior to the swap if coasting in gear the injectors wouldn't fire until idle speed. Now with the newer auto PCM running manual tuning the injectors start to fire at approximately 1200 rpm.

I am trying to determine if this is "normal" for a newer manual PCM, specifically DAC3 programming.

The truck runs so much better with the newer PCM aside from this anomaly.

 

[rv6a]

I can't say that I have ever noticed when they start firing. I'm guessing when I push the clutch in as I'm coming to a stop. While going down grade if I touch the throttle they fire. Not much help, I know.

 

[greenskeeper79]

I hooked the truck up to my auto enginuity software

All readings are with running the hydra chip calibrations



OLD PCM (ZDR3 DPC-411 VIAE9W2)

INJECTOR PULSE WIDTH

IDLE = 0.25

COASTING IN GEAR ABOVE 700 RPMS = 0.06



NEW PCM (NVK3 DPC-422 VOAA7P6)

INJECTOR PULSE WIDTH

IDLE = 0.25

COASTING IN GEAR ABOVE 1150 RPMS = 0.06

COASTING IN GEAR BETWEEN 700-1150 RPMS = 0.16

The hydra tuning isn't overriding the programming for the auto transmission in regards to injector cut in. In fact it seems reasonable to assume that with an automatic transmission injector cut in would occur right at torque convertor unlock (in this case 1150 rpm)

 

[Traildust]

I have a 02 6 speed with an AEB4 code, it was re-flashed from the OEM AEB2. We have some long steep downgrades around here and I am pretty sure my injectors stop firing when I let off the throttle. On those long downgrades I can let off the fuel pedal and let it coast in gear down hill. My egt will drop as low as 170 to 160. If I had some way to read fuel flow I would know.
Bill

 

[greenskeeper79]

I was able to "hear" the injectors when firing on my 99 if I listened closely enough, AE confirmed it with the numbers posted above.

 

[greenskeeper79]

Tony at TDP was kind enough to send me a tuning file to try.

I reprogrammed and got these results on the NVK3 PCM

01 TDP file higher injector cut-in, not much different than stock 00 setting
(not sure how aggressive this file is)

02 1000 rpm DAC3 1000 rpm as expected

03 80 HP DAC3 higher injector cut-in, less power than 05

04 1000 rpm NVK3 1000 rpm as expected

05 80 HP NVK3 normal injector cut-in at idle, idle is higher than 01,03, and engine "misses" when accelerating between 1500-2000 (I assume this is because the PCM does not see TC lock), way more power than 03

WTS light and idle "hiccup" occurs when switching from DAC3 to NVK3 as expected

Is it possible that the PCM "ignores" the DAC3 programming because everything that is programmed DAC3 seems very similar power wise compared to stock 00 setting.

Not sure what to do next, aside from search around for a genuine DAC3 PCM to purchase, or an E99 California emissions truck is so goofy that I should just leave it stock.