TOPIC: 2018 GMC Sierra 1500 6.2L V8 - Starting from scratch

2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 05 Jun 2019 16:21 #25

  • Andrew Leyva
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Thanks for the input! I appreciate all the commentary and tips...

Sure, I remember the days of the 850 cfm double pumper Holly's and high-rise manifolds, etc to increase the flow of EVERYTHING. My thought was to get the engine to struggle less and breathe better; less restrictive and more efficient airflow translate to less "throttle angle". In effect, not having to give it as much throttle (my right foot) and thereby using "less" gas. Much in the same way as shedding weight - takes less gas to move a lighter vehicle, etc... I think that panned out in the modest gains via the less restrictive intake and mufflers 14 mpg vs 11 mpg. I consider my endeavors a victory - albeit a small one! So, I may be confused. But, I thought a more EFFICIENT engine would translate to more mpg... To be sure - I understand more air more fuel.... I'm thinking less STRAIN less fuel

Regardless, I'm still having fun with all the experimentation!

I work out of town, so the going is slow. Here are the latest updates...

Thanks for asking, Claudio. Last week I was finally able to install the plugs, wires and coil packs. I installed all three components at once, fired it up and...WAIT FOR IT....it sounded horrible!! What the heck! Got a nice scan tool last Black Friday - dug it out and hooked it up. It said cylinder 8 misfire. Great! Of course, that is the one that is most difficult to access!! Swapped #8 coil pack with #2 coil pack (easiest to access) and reran the test. This time it indicated cylinder 2 misfire. Okay, so I have a bad coil pack! I emailed Granatelli that night. They called me the very next morning and had a replacement shipped out that day. They were very accommodating! What is interesting, even with the faulty coil pack, there was a CONSIDERABLE amount of water pooled under the tail pipe. It was like someone had spilled a small glass of water! I'll take that as more complete burn?? There is a bump in the mpg, but not much. Still, I haven't driven more than a half a tank on the new components. Acceleration ia excellent! Engine runs smooth and it sounds amazing! I'm really grateful for all your tips! Overall, I'm very happy with the upgrade.

The EFIE's finally arrived. Delay was something about flooding in the Ontario area. I'm perusing the forums now on the best way to install them. When installing the plugs and wires, I needed to remove the wheel well liner to better access the plugs. While doing so, I noticed the upstream O2 sensors were right there - so, I should have not much of a problem accessing them. I've seen George Wiseman's video and Ron's EFIE install video, but still unsure as to what wire is what. I'll have to do some research. I'll install them and the MAP controller ASAP - then it's Groovy time!
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2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 05 Jun 2019 16:29 #26

  • Andrew Leyva
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I went on eBay and got the shop manual on dvd, for my truck. 16,000 pages for $25! There is a wealth of information and should help me out tremendously! The manual says ECM computer optimizes the air fuel mixture to 14.7 to 1. MAP, MAF, O2 sensors, even engine RPM and vehicle speed are all calculated to maintain this ratio. I'm really looking forward to installing the EFIE and MAP enhancer!

For anybody curious here are some excerpts from the shop manual for 2018 GMC Sierra 1500, 6.2L L86 V8:

Fuel Metering Modes of Operation
The ECM monitors voltages from several sensors in order to determine how much fuel to give the engine. The ECM controls the amount of fuel delivered to the engine by changing the fuel injector pulse width. The fuel is delivered under one of several modes.

Starting Mode
The ECM supplies voltage to the fuel pump driver control module when the ECM detects that the ignition is ON. The voltage from the ECM to the fuel pump driver control module remains active for 2 s, unless the engine is in Crank or Run. While this voltage is being received, the fuel pump driver control module closes the ground switch of the fuel tank fuel pump module and also supplies a varying voltage to the fuel tank fuel pump module in order to maintain the desired fuel line pressure. The ECM calculates the air/fuel ratio based on inputs from the engine coolant temperature (ECT), manifold absolute pressure (MAP), mass air flow (MAF), and throttle position sensors. The system stays in starting mode until the engine speed reaches a predetermined RPM.
During a cold start, the engine control module (ECM) commands dual-pulse mode during Open Loop operation to improve cold start emissions. In dual-pulse mode, the injectors are energized twice during each injection event.
..
Clear Flood Mode
If the engine floods, the engine can be cleared by pressing the accelerator pedal down to the floor and then cranking the engine. When the throttle position sensor is at wide open throttle (WOT), the ECM reduces the fuel injector pulse width in order to increase the air to fuel ratio. The ECM holds this injector rate as long as the throttle stays wide open and the engine speed is below a predetermined RPM. If the throttle is not held wide open, the ECM returns to the starting mode.

Run Mode
The run mode has 2 conditions called Open Loop and Closed Loop. When the engine is first started and the engine speed is above a predetermined RPM, the system begins Open Loop operation. The ECM ignores the signal from the heated oxygen sensor (HO2S). The ECM calculates the air/fuel ratio based on inputs from the engine coolant temperature (ECT), manifold absolute pressure (MAP), mass air flow (MAF), and throttle position sensors. The system stays in Open Loop until meeting the following conditions:
The HO2S has varying voltage output, showing that the HO2S is hot enough to operate properly. The ECT sensor is above a specified temperature.
A specific amount of time has elapsed after starting the engine.
Specific values for the above conditions exist for each different engine, and are stored in the electrically erasable programmable read-only memory (EEPROM). The system begins Closed Loop operation after reaching these values. In Closed Loop, the ECM calculates the air/fuel ratio, injector ON time, based upon the signal from various sensors, but mainly from the HO2S. This allows the air/fuel ratio to stay very close to 14.7:1.

Acceleration Mode
When the driver pushes on the accelerator pedal, air flow into the cylinders increases rapidly. To prevent possible hesitation, the ECM increases the pulse width to the injectors to provide extra fuel during acceleration. This is also known as power enrichment. The ECM determines the amount of fuel required based upon throttle position, engine coolant temperature (ECT), manifold absolute pressure (MAP), mass air flow (MAF), and engine speed.

Deceleration Mode
When the driver releases the accelerator pedal, air flow into the engine is reduced. The ECM monitors the corresponding changes in throttle position, mass air flow (MAF), and manifold absolute pressure (MAP). The ECM shuts OFF fuel completely if the deceleration is very rapid, or for long periods, such as long, closed- throttle coast-down. The fuel shuts OFF in order to prevent damage to the catalytic converters.

Battery Voltage Correction Mode
When the battery voltage is low, the ECM compensates for the weak spark delivered by the ignition system in the following ways:
Increasing the amount of fuel delivered Increasing the idle RPM
Increasing the ignition dwell time

Fuel Cutoff Mode
The ECM cuts OFF fuel from the fuel injectors when the following conditions are met in order to protect the
powertrain from damage and improve driveability:
The ignition is OFF. This prevents engine run-on.
The ignition is ON but there is no ignition reference signal. This prevents flooding or backfiring.
The engine speed is too high, above red line.
The vehicle speed is too high, above rated tire speed.
During an extended, high speed, closed throttle coast down-This reduces emissions and increases engine braking.
During extended deceleration, in order to prevent damage to the catalytic converters

Fuel Trim
The ECM controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. The ECM monitors the heated oxygen sensor (HO2S) signal voltage while in Closed Loop and regulates the fuel delivery by adjusting the pulse width of the injectors based on this signal. The ideal fuel trim values are around 0 percent for both short and long term fuel trim. A positive fuel trim value indicates the ECM is adding fuel in order to compensate for a lean condition by increasing the pulse width. A negative fuel trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition by decreasing the pulse width. A change made to the fuel delivery changes the long and short term fuel trim values. The short term fuel trim values change rapidly in response to the HO2S signal voltage. These changes fine tune the engine fueling. The long term fuel trim makes coarse adjustments to fueling in order to re- center and restore control to short term fuel trim. A scan tool can be used to monitor the short and long term fuel trim values. The long term fuel trim diagnostic is based on an average of several of the long term speed load learn cells. The ECM selects the cells based on the engine speed and engine load. If the ECM detects an excessively lean or rich condition, the ECM will set a fuel trim diagnostic trouble code (DTC).
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2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 05 Jun 2019 16:40 #27

  • CLAUDIO CORDOVA
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Thank you for the great info! Much appreciated.

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2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 06 Jun 2019 11:29 #28

  • GregK
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Hi Andrew -
Yes, we've had a very wet spring here in Ontario, and we have had some flooding, so that's a plausible reason for the delay in getting your EFIEs
You will want to take a good look at this before you get under the truck:
oxygen sensor operations and wire colours
Pay attention to the sensor waveform graphics halfway down the page - the EFIE adds voltage to the signal sent to the ECU, so you want your sensors to read like the pic in the upper right when rolling. You'll get codes if the waveform looks like the pic below that. If your reader does live data, use that to adjust your offset voltage. and DO take George's advice about soldering rather than crimping.
what I did was I bought an o2 sensor harness extender to splice the EFIE into, so I didn't damage the factory harness, and so I could remove it if we ever go to visual inspections.
These guys were most helpful, speedy and inexpensive.
If you haven't already, look for George's EFIE adjustment video on youtube: it gets a tad confusing when he talks about what jumper wires are connected where, but rewind and read the manual and rewind and...the green and white wires are what are connected to each sensor, so that's where you read the offset; the black and white wire are the corrected output of the sensor to the computer that you can see the waveform with. (an oldschool analog sweep meter rather than an autoranging digital one is most helpful here...)
be gentle and adjust them in harmony, in small steps. seriously. you'll know when you've gone as far as you can by the sound of your truck. the key part is to turn it off (the truck) to store that in the ECU, then restart and drive. you have to make the truck re-learn.
I believe there's a GM re-learn drive cycle document in the documants section here you should reference...if you can't find it, I probably have it somewhere.

Same thing for the MAP sensor...measure, adjust, shut down, drive. I can get my ride to have a very low and rough loping idle, and the best economy so far is to back off just enough so that it smooths out. best economy doesn't necessarily mean best drivability though, so I had to back off just a hair more from there to make it "feel right"
I'm assuming a steam injection system would help immensely at the "best economy" settings, but I haven't had time to rig that up on mine yet to verify.

this is exciting! I can't wait to hear your results!
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2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 10 Jun 2019 12:11 #29

  • GregK
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woah - I just read post #25 of this thread and there are some serious nuggets of info in there!
Like "cold start dual pulse mode" and "battery voltage correction mode" and "run mode," where the conditions for closed loop fuel delivery are explained:
engine coolant temp must >= a certain temp, and/or the Oxygen sensor must be at a certain temp (Ron's right about insulating the exhaust to keep the heat in and make for faster warmups!), and the fallback/error check - elapsed run time.
I'd think the computer would look at the oxygen sensor first (it doesn't say it outright, but heated sensors make for shorter start-up and better efficiency), then the engine coolant temp (it takes the block longer to warm up than the exhaust, so make sure your cooling system is operating correctly -proper coolant type/level, correct temp t-stat), and THEN (AND as a check against the o2 sensor and ECT sensor), the elapsed run time since start. wow.

I'm wondering if there is a way to infer exhaust gas temps from oxygen sensor data...how can we get that data?? well, well...

EDIT: This Site confirms and expands on some of what was detailed by Andrew - I can confirm that from cold start on mine, o2 sensors aren't factored in/listened to until ECT is 55-60 degrees C (130 degrees F), at which point the EGR system is tested, because that's when I hear the solenoids under the hood actuating and I see RPMs start varying ever so slightly as the computer looks to find optimal hot idle by learning where to position the throttle plate.

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2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 18 Jun 2019 17:49 #30

  • Andrew Leyva
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Thank you for the info, GregK!! I knew someone would be able to find the gems in that post!

Just got back, but won't have time to install the EFIE. I did get the extension you mentioned; it arrived late last week. Hopefully, I got the right one. Here's a picture of it.



I haven't had the chance to compare it against the O2 sensor harness on the truck, yet. It's frustrating having these gaps installing all the goodies.

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2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 18 Jun 2019 21:02 #31

  • GregK
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Before I ordered my extender from them, I contacted their customer support via e-mail to confirm I was going to order the right one. Turns out that I was about to push the button on the wrong one, but they saved the day by pointing out the differences between what I thought was right and what actually was right. that made install a breeze. the toughest part was getting the EFIE wires through the firewall.

Andrew, I hope you can find the time sooner than later. I regret that it took me over a year to get around to it. goodness knows how much more I would've saved at the pump if I hadn't been so cautious.
Surely by now you have some solid mileage numbers, so you'll know pretty quickly how well this works for your application. all that will be left is to get your groove on this truck!
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2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 24 Jun 2019 17:40 #32

  • Andrew Leyva
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You were right Greg! Just went under the truck to start the install of the EFIE and lo the harness is a flat 4 way, the extension I got is 4 way cube style. I just emailed Ballenger to get the correct one.

Looked at the wires and according to the graphic you linked, the blue wire is the money wire!



Gonna wait until I get the correct extension. Progress is slow, but there is progress. My Dremel is scheduled to arrive today!!

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2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 25 Jun 2019 09:44 #33

  • GregK
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Happy to help...but just to confirm, your truck has only one or two upstream o2 sensors? wouldn't that mean 2 EFIEs and 2 extenders? (You're speaking in singular when I believe you should be pluralizing; I might be wrong, so like the wiring, it's always best to check)

and again, don't go cutting any wires until you've confirmed/verified that the blue one is indeed the signal wire!!

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2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 25 Jun 2019 16:33 #34

  • Andrew Leyva
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Yep! Bank 1, Sensor 1; Bank 2, Sensor 1 - pre cat HO2S. I'm going to stop by the local mechanics (good guys) to see if they can confirm the wires. They helped me identify the PCV before I got the shop manual. Surprisingly, the shop manual doesn't specify the wires. 16000 pages of info and no mention - but they DO instruct on repair and replacement.

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2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 25 Jun 2019 23:25 #35

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Sounds to me like you're on the right track...keep up the great work!

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2018 GMC Sierra 1500 6.2L V8 - Starting from scratch 26 Jun 2019 02:37 #36

  • Andrew Leyva
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Lol! Yeah, right on track, but somewhat of a dork. I'm having a hard time getting the harness apart/unclipped! Timidity's gotten the best of me and afraid of breaking the connection! I know it has to be super simple - trying not to force anything.

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