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Discussion Starter · #101 ·
At full load GM limits rail pressure to 2000 bar, GDE does not change this. FYI, the fuel system in the 2019+ vehicles is rated for up to 2500 bar, but GM elected to not change peak fuel pressure above 2000 bar.
Thanks for the response. My question was actually does the GDE tune increase fuel rail pressure for the same power output. For example, cruising down the highway at 70mph, is the fuel rail pressure the same between the OEM tune and the GDE tune? I was under the impression that the fuel rail pressure could be lowered by the ECU as conditions allow, but maybe I was mistaken?
 

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Took a 100 mile mostly freeway drive today for work. Speeds were 55 to 75 MPH. Have made this run many times before and get 32 and change MPG like clockwork, something like 32.6 is pretty typical. This was my result from today's trip with the GDE compliant tune. One trip is hardly definitive, but it is safe to say that the compliant tune gives up nothing fuel economy wise to the pre EPA tune. It actually seems to do a little better. I drove it like I always do, was not doing anything special today. I do live in mile high Denver, the thin air here helps fuel economy. Apples to apples, the compliant tune did a few percent better than what I usually see. The truck had a regen prior to this trip, so that did not enter in.

It really does run like a smooth turbine on the compliant settings, I continue to be amazed - so much better than factory settings, which feel positively agricultural in direct comparison.

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Took a 100 mile mostly freeway drive today for work. Speeds were 55 to 75 MPH. Have made this run many times before and get 32 and change MPG like clockwork, something like 32.6 is pretty typical. This was my result from today's trip with the GDE compliant tune. One trip is hardly definitive, but it is safe to say that the compliant tune gives up nothing fuel economy wise to the pre EPA tune. It actually seems to do a little better. I drove it like I always do, was not doing anything special today. I do live in mile high Denver, the thin air here helps fuel economy. Apples to apples, the compliant tune did a few percent better than what I usually see. The truck had a regen prior to this trip, so that did not enter in.

It really does run like a smooth turbine on the compliant settings, I continue to be amazed - so much better than factory settings, which feel positively agricultural in direct comparison.

View attachment 408277
You need to hand calculate it, going by the DIC when tuned is often times a fool's errand because it's way off from what it actually is. I've hand calculated a couple of tanks or so with the GDE compliant tune and it was off by around 1-2 MPG.
 

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You need to hand calculate it, going by the DIC when tuned is often times a fool's errand because it's way off from what it actually is. I've hand calculated a couple of tanks or so with the GDE compliant tune and it was off by around 1-2 MPG.
Agree - did do the hand calc thing for awhile and my experience is similar to yours. I assume the slightly off readings from the DIC are comparable to each other though :LOL:
 

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Discussion Starter · #105 ·
My stock truck DIC has also been off 1 or 2mpg the few times I hand calculated it as well.
 

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My stock truck DIC has also been off 1 or 2mpg the few times I hand calculated it as well.
I hand calculated mine when stock with stock tires and it was always within .2MPG-ish so I stopped bothering. Tuned and with larger tires (adjusted for in the tune) the amount it's off by has varied.
 

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Thanks for the response. My question was actually does the GDE tune increase fuel rail pressure for the same power output. For example, cruising down the highway at 70mph, is the fuel rail pressure the same between the OEM tune and the GDE tune? I was under the impression that the fuel rail pressure could be lowered by the ECU as conditions allow, but maybe I was mistaken?
More or less the same answer. Some part load areas are lower fuel pressure than stock and other are higher, all points within 100 bar. It is more for emission control than output anyway.
 

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Completed the 2nd regen, which is the 1st one to be entirely on GDE's compliant tune, it went 371 miles, which is a nice improvement from OEM, which was around 275 miles, but of course less than the 700 plus miles it used to go when EGR was not running with the old non compliant settings. The emissions monitors have all reset except for PM (particulate matter - DPF) which apparently takes longer. Waiting for that to reset so I can take it in for emissions.

The truck continues to run fantastic - I would not know the difference between the old settings and the compliant ones as far as the driving experience goes. GDE can correct me, but my impression is their settings use less EGR and more DEF than factory. DEF use seems to be more, but it has been a long time. The oil has not turned inky black in about 700 miles of driving, which is much different than what I recall the stock behavior. GDE's settings are likely much "cleaner" than factory on the soot front.
 

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How does the truck return equal / better mpg with emissions compliant tune / shorter regen interval compared to the non compliant tune with the longer regen interval .. considering mpg drops like a rock during regen ?
 

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How does the truck return equal / better mpg with emissions compliant tune / shorter regen interval compared to the non compliant tune with the longer regen interval .. considering mpg drops like a rock during regen ?
Regens only last 20-30 minutes and fuel economy on the freeway drops around 6mpg, over the course of a tank of fuel it's really not that much impact.

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