Author Topic: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck  (Read 13721 times)

Offline vtsteam

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I've recently resurrected my 1996 Chevy Silverado 4WD pickup truck. She had been sitting in a field for four years with multiple issues, including, the need for new ball joints, new front axle hubs, new 4WD actuator, new front disks and rotors, rebuilding of the frames under the pickup bed, new rear bumper, new rear cab mounts, new emergency brake cables, new steering box, new upper control arms, new battery, new fuel tank, and patching a number of rust holes by welding in patch panels. I did all of that last summer.

Why did I do all that? I don't know. I like the truck. I don't know why. It feels good to drive it again. It feels good not to have brought it to a wrecking yard. It actually looks solid now, and drives very nicely. It does hard work around here, hauls cords of wood, steel shapes, and sand for when I have to deal with 600 feet of driveway after an ice storm. The poor thing deserved a second chance.

I like that truck. Despite all the time and money I put into it, it's a tiny fraction of what a new 21st century annoying piece of digitized plasticized oversized hype in the form of a pickup truck would now cost me. The only thing I don't like about it is..... it's original, when acquired used, average fuel consumption of 15 miles per gallon.

Well, I'm going to do my best to change that. In fact, even with no changes, other than adding a bluetooth monitor to the truck's OBDII port that communicates with my cellphone, I am able to monitor fuel consumption on the fly, as well as about a hundred other engine parameters, and have changed my driving habits to the point where average fuel consumption is about 18 mpg presently.

But that's just a start. I have plans.  :zap:

The first one is, ummm, reprogramming the truck's computer, or PCM as it is called. Well actually not that one. I'm thinking about trading its old PCM for a later one, because it is more programmable with open source and free software called UniversalPatcher, PCM Hammer, and TuneRPro.

To make the swap, I would have to re-pin new connectors onto the old wiring harness, and this isn't a trivial undertaking as the old and new connectors are different styles (and number -- 5 in the old and 2 in the new) and have a total of 128 pins, with no correspondence of positioning for the wires.

Rather than re-pin the connector -- which is not easily reversible if I don't like the swap, I've decided to try to make an adapter cable.

More later......
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline cwelkie

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #1 on: January 22, 2025, 08:46:38 AM »
Well done on resurrecting the "ole girl".  There are still many years of service available yet.  It's always nice to hear of someone else that is of the opinion that it's cheaper to maintain than replace a vehicle.  Besides, it's got to the point where one can't operate any "dash board controls" with gloves on in a new vehicle!

Building an adapter cable is likely the best way to go.  It reminds me of installing a Ford V8 into a Volvo 245 (wagon) many years ago.  I left the Volvo engine bay cable in place and added the Mustang cable alongside and connected to two together at the appropriate places.

Good luck with your quest ...
Charlie

Offline AdeV

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #2 on: January 22, 2025, 04:21:52 PM »
If you really want to avoid the electrodigicals... you'd be better off with a 1966 Silverado with a quadrabog carburettor....

Extra points if you can tell which YouTube channel I've been watching way too much of, perfect!
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline vtsteam

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #3 on: January 22, 2025, 05:59:24 PM »
Thanks kindly, Charlie! :beer: What I like about the old truck is that it is very easy to work on, and parts are super available. You could practically build a new '96 Silverado from available parts.

I do like the fact that it is heavily built, though that tends to mitigate against fuel economy. But it does mean that the frame has lasted in the Northeastern winters where salt on roads is heavy. Most vehicles here die, not from mechanical issues but rust. This truck was somehow preserved when I bought it years ago, and after the repairs I now undercoat it with a commercial oil compound each fall to keep it that way. I've also reduced driving it in winter.

The cross frames under the bed were rusted away at the ends, since they were thin hat-shaped sections spot welded to the bed floor -- almost designed to rust. Last summer I pulled the bed off, ground them off, and replaced with much heavier steel square tube. The bed itself was fine, since it had a bed liner and someone had smeared grease under it before installing.

Square tube for frames:

 


 


A fabricated X main frame cross member and spare tire winch from channel iron:

 




Fair warning, the adapter cable Idea is kinda iffy for a lot of reasons, including fit in the space available, signal noise, and just the sheer difficulty of the solder work needed for all these crossing lines. We'll see. It's a real madmodder project, and may even seem a waste of time to a few. Not for me. I like learning things along the way, even if it turns out that a project idea isn't workable.

BTW, the cable is not intended for regular use. It's just for experimenting while deciding if I want to commit to a re-pin and the newer PCM. I could end up staying with the old one, if I don't like the change

Most people contemplating a PCM swap like this one are after increased performance, and that has clearly been achieved by others -- generally in combination with other mechanical changes like headers, air induction, etc.  But my goal is solely in increasing fuel economy in an otherwise stock vehicle, and that is a questionable hope for a PCM swap. We'll see. No one else has done it for this purpose that I'm aware of. so it's a crap shoot.
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #4 on: January 22, 2025, 06:26:12 PM »
If you really want to avoid the electrodigicals... you'd be better off with a 1966 Silverado with a quadrabog carburettor....

Extra points if you can tell which YouTube channel I've been watching way too much of, perfect!

HaHa Ade, I know exactly who you mean! Well rust here means that '66 Chevy pickups must be distant memories, at least within several hundred miles, and if they do exist, people want crazy money for clapped out rustbuckets of that vintage locally. For some reason, you can still find early nineties Silverados for $4K to $5K and occasionally not in bad shape within  the neighboring states.

I'm pretty comfortable with the PCM in my truck -- heh, '96 is the computer era, when you think about it, earlier even than Windows 98. it's DOS era. It's really interesting how sophisticated nevertheless these control computers were for their time.

Here's the kind in my truck, called a "BlackBox" PCM by Chevy enthusiasts. This one is a junkyard donor box, which I am robbing for the connectors:

 
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #5 on: January 22, 2025, 06:29:26 PM »
Opening it up:

 


It contains two PC boards which are piggybacked to each other:

 


There is an interesting system of aluminum tape and cement to transfer heat to the outer case heat sinks.
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #6 on: January 22, 2025, 06:31:43 PM »
Here are the boards apart. There's a cemented rubber shock absorber framework between the boards:

 


And here's the outer side of the boards:

 

I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #7 on: January 22, 2025, 07:04:57 PM »
Here I am removing the soldered connectors, which I will use in the adapter cable. It's an old Radio Shack (who?) solder sucker -- maybe the same era as the PCM!

 
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #8 on: January 22, 2025, 07:07:35 PM »
Here are the connectors I got out of the box. There are 5 of them. Three are 32 pint, one is 24 pin, and then there's an odd center connector, that actually just has a pair of pins shorted by the harness. The multipin connectors are color coded Red, Blue, Black, and White (or gray), and I've marked tops and bottoms as well as the color.

 


I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline AdeV

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #9 on: January 23, 2025, 04:33:10 AM »
Seems like a brave choice to me, mucking around with the OEM stuff.... Were you never tempted to do something like replace it all with a Megasquirt? EFI (if you've not already got it on the truck) would also be good for fuel economy, not to mention cold starting etc.

I know what you mean about '96. We were still just getting over the shock of seeing WIndows 95 for the first time... Most of us were still using i486 powered computers (the Pentium was out, but sooo expensive, but also sooo fast), computer memory was measured in megabytes not gigabytes, and a 1GB hard drive was considered cavernous!
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline BillTodd

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #10 on: January 23, 2025, 09:29:03 AM »
This reminded me of my brother's approach to complex electronics ....

Faced with a 3.0l Merc with dead injection and a tight filming schedule ( the Bond film 'Octopussy' I think ) . To get the recalcitrant merc to roll a few hundred yards down a railway line, he simply sawed off the injector and welded on a carb :-)

https://randomrailways.wordpress.com/2021/01/01/bond-on-rails/



« Last Edit: January 25, 2025, 01:21:07 PM by BillTodd »
Bill

Offline vtsteam

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #11 on: January 23, 2025, 11:56:11 AM »
Seems like a brave choice to me, mucking around with the OEM stuff.... Were you never tempted to do something like replace it all with a Megasquirt? EFI (if you've not already got it on the truck) would also be good for fuel economy, not to mention cold starting etc.

I know what you mean about '96. We were still just getting over the shock of seeing WIndows 95 for the first time... Most of us were still using i486 powered computers (the Pentium was out, but sooo expensive, but also sooo fast), computer memory was measured in megabytes not gigabytes, and a 1GB hard drive was considered cavernous!

Thanks Ade, :beer: I actually don't feel brave re. the OEM stuff -- I don't know much about the megaSquirt, but just looked it up and it seems much more involved and costly -- I'm on a water budget, not even up to good beer standards :lol:. Looks like you need $600 to play megasquirt, and that doesn't include options like various temp and crank position sensors, etc. Also you may need a wideband O2 sensor -- mucho additional dinero.

The OEM PCM I will be swapping in is called an 0411 by Chevy folks -- and specifically I will be using one tuned for a 2001-2002 Chevy Express Van, which had options for the same 5.0L Chevy Vortec engine I have in the '96. So basically the tune is already set up except for a few parameters, which are documented. I'm not breaking new ground here. The PCM, pre-programmed for the swap cost $150, and probably would have worked by simply repinning the connectors. No need for the cable I'm making.

But I'm a cautious experimenter, and if there are problems I don't know about, and I want to return to my old black box PCM, the cable would allow a simple swap back by plugging the old one back in.

A possible issue, for instance, might be passing inspection with a swapped PCM, in my state. The new PCM contains the VIN of the vehicle. It presently has the VIN of a 2001 Express Van. I can change that with editing software to match the Silverado's actual VIN -- but how will that affect the other engine parameters the PCM uses? The VIN encodes many vehicle and engine options. Does the PCM look at the VIN and decide what engine and options are onboard and how to operate?

I don't know. That's just one issue I can come up with among many I can think of, and I don't seem to get knowledgeable answers when I ask others about their experiences. For one thing, every state has different rules for inspection. So one person's answer may not work for me. Some states don't care about a PCM swap. Others insist that the VIN of the PCM match the vehicle VIN.

Anyway, I think a cable will be worth it for me to just experiment with what I have and get real answers to my questions.

Oh yes Win95 -- I forgot about that! Yes Win98 was so advanced! Actually, I was originally a TRS80 guy to start with, and then a Amiga fan, before eventually getting a genuine IBM PC. I was kind of disappointed at how conservative the PC was when I first got it. My old LNW-80 (home-built 5.3 Mhz TRS-80 upgraded clone) ran circles around the PC, but I did like the open spec and swappable boards in the IBM. Which of course led to IBMs downfall in the PC market. I sure wish Amiga had survived, it was to me the best combination of forward thinking at the time. Oh well....  :beer:


I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #12 on: January 23, 2025, 12:03:52 PM »
This reminded me of my brothers approach to complex electronics ....

Faced with a 3.0l Merc with dead injection and a tight filming schedule ( the Bond film 'Octopussy' I think ) . To get the recalcitrant merc to roll a few hundred yards down a railway line, he simply sawed off the injector and welded on a carb :-)

Thanks Bill :beer: I love that!  :thumbup: :clap:
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #13 on: January 23, 2025, 12:56:36 PM »
I should add a few things about this project, since the PCM swap is actually just a part of what I have planned. I'm also hoping to address the Silverado's wind resistance, to try to improve fuel economy. To relate to you, my cousins across the pond, let's just say it presently has the aerodynamics of Winchester cathedral.

I've come to realize just how this affects the truck at various speeds by installing an inexpensive bluetooth monitor dongle in my truck's OBDII port, and using a program on my cell phone to record several parameters while driving. Very interesting stuff. My truck gets better gas mileage, for instance, at 35-45 mph, than it does at 50-55 mph. Obviously, wind resistance is a big factor here.

BTW in case anyone is interested, the dongle I use is a Vgate iCar Pro Bluetooth, which cost me about $30.

I run the Torque Pro App on my phone and tablet (about $5). This is an amazing, to me, combination. I can configure any on-screen gauges to monitor a selection of maybe a hundred different engine and vehicle parameters, in real time, and even create logs.

Here's a graphed example of a log I created for some specific engine parameters I wanted to record for a test drive which included idling, in town driving, highway driving, and country road (curvy, hilly, low traffic, few stops) driving. I'm attaching a screenshot example (sorry, too wide for forum inline placement).





I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
« Reply #14 on: January 25, 2025, 10:41:28 AM »
Here is a great little series of DIY experiments with a pickup truck aimed at reducing air resistance:

https://www.amateuraerodynamics.com/2022/04/optimizing-aerodynamics-of-truck-part-1.html

And this is a PC board I've been working on to mount the connectors. I managed to get a mask onto it after many trials and much tribulation using printer transfer methods.

 


I haven't etched it yet. I finally hit on a transfer method that works for me. That took a week of experimenting. Some here may recall a similar problem I had back when I wanted to make an etched brass plaque for my electronic leadscrew project. I never did get a good enough mask then. I might revisit that now that I have a system that works.

re. pc boards for this cable....I would have liked to have just spliced wires between the old PCM to the new PCM connectors point to point, in order to make up a conversion cable. Unfortunately, the salvaged PCM connectors are right angle PC mount, and that would not work for a cable. So I drew up two short narrow PC boards that bring out the pins. I can then solder wires in the proper direction as a cable. These narrow boards mimic the orientation and spacing of the two back-to-back PC boards that I removed the connectors from. This orientation and spacing will help mate the connectors easily to the vehicle's bundled and wrapped connector harness. That's the hope, anyway.

I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg