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Discussion Starter #1
So I recently drove my 97 and 99 back to back. Wow does the 99 have louder injectors over 30% throttle. Below that you can hardly hear them firing. The 97 is actually quieter than the 99 above 30% throttle.

The 99 has a new fuel pump and rebuilt regulator with OEM parts. I do not have a fuel pressure gauge, but when checked at idle it is at 68 psi, and the truck runs great with good power.

I also have done sound deadening with foam in the dash, door seal mod, new steering shaft seal, and foam under the shifter boots.


I am thinking of doing the Hutch mod kit from drivendiesel for $199, HPO cross and the Fuel Rail Crossover™ (FRx) from riffraff for $180 to try to quite it down.

Any thoughts?
 

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I think normally it's the other way around.
Is the 97 a cali model? (With split shot injectors)

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Discussion Starter #3
I think normally it's the other way around.
Is the 97 a cali model? (With split shot injectors)

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97 isn't cali model

Pulled the hydra chip. Injectors are nice and quiet now throughout the go pedal range.

Why the hydra makes them noisy above 30% throttle I have no idea.

The only thing I can think of is that the PCM/HEX code for my truck doesn't have any tuning and I had to use a difference PCM/HEX code to program the chip.

I am going to look to see if any other tuners offer downloadable programming for the hydra chip.
 

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Ah, tuning could very well be it.
I do believe several others offer tunes for the hydra.

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Discussion Starter #5
After some research it appears I have an ZDR3 PCM and should probably switch it out for a DCA3 for better programming?
 

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@[email protected] would know best.
I can't remember the code they usually recommend.

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Discussion Starter #7
I have researched that the base tuning in the E99 PCM is bunk, so I read it is a good idea to upgrade the PCM and then download the hydra tunes for the newer PCM to make the truck run right. There are no specific PHP tunes for the PCM that is currently in the truck.
 

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interesting...

maybe try gearhead tune, or give a call to PHP maybe they can fix their tune
 

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Discussion Starter #9
I wonder if a CLB5 DAC-401 PCM would swap in so I can use the newer tuning files?
 

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Discussion Starter #10
Looks like I'd actually need a DPC-421
 

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Discussion Starter #11
found a DPC-421 out of an F-450, I'll assume it will work with any of the DPC-421 program files
 

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Discussion Starter #12 (Edited)
The swap was as easy as it gets. Took a DPC-422 PCM out of a 2000 truck with automatic transmission. Prior to swapping I moved the hydra chip to the new PCM and programmed it on my workbench with DAC3, Hex code VOAA7P6 which is for 2000 zf6 truck.

I was concerned about the additional shunt wiring for the california emissions but it turns out that the wires go to unused pins on the new PCM (no SES light)

Noticeable differences:

1) truck idles much smoother at first start and coming off throttle

2) power is smooth throughout the rpm band

3) injector cutoff is higher for whatever reason. Coasting in gear with the newer PCM cuts off the injectors above 1200rpm, the old PCM cut the injectors off at anything above idle

4) exhaust note is "cleaner", hard to describe, probably has something to do with different timing strategies compared to cali emissions.

5) MUCH quieter injector noise regardless of throttle input

I should have done this a long time ago, E99 and cali emission programming is terrible!
 
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