Big Diesel, MPG increase ideas?

[Isaac Zachary]

Originally Posted by ps2fixer

Small diesel engines in vehicles seem to be so uncommon...

Chevrolet offers a 2.8L 4 cylinder diesel in their full sized vans, including their one ton (3500) extended vans and their midsized pickups. Their pickups with that option are rated to get up to 29-31mpg on the highway.

From 2015 to 2019 Ford offered a 3.2L 5 cylinder diesel engine in their midsized vans, pickups and SUV's.

[ps2fixer]

Yea, but I'd never buy anything around 2000 or newer xD. Besides the massive price increase, the extra electronics I'm not a fan of, strict EPA gizmos and such.

Pretty interesting on the van though.

I remember hearing about the 5 cyl gas engine, didn't know there was a diesel made that way too, or maybe what I heard was the diesel. Been ages since I last heard about it.

[cRiPpLe_rOoStEr]

Originally Posted by ps2fixer

I wonder what other applications used the 3.9L Cummings. Kind of late now since I already own the 7.3L but would be interesting to read a bit more about it assuming it's used in the US in something.

AFAIK the only emissions-certified application for the B3.9 stateside was in some walk-through vans, yet the engine can be legally swapped into trucks within the same class.

Random/interesting idea, take a 5.9/6.7L cummings, disable 3 cylinders (and keep it balanced yet) and throw it in a small vehicle, small truck or rwd car.

IIRC there were some 3-cyl engines based on the same design for agricultural tractors from Case-IH and New Holland. On a sidenote, there was a time when it used to be common to fit a 3-cyl 2.9L Diesel engine into Ford F-1000 trucks in my country as an attempt to save fuel, even though it was clearly underpowered.

[Isaac Zachary]

Originally Posted by cRiPpLe_rOoStEr

AFAIK the only emissions-certified application for the B3.9 stateside was in some walk-through vans, yet the engine can be legally swapped into trucks within the same class.




IIRC there were some 3-cyl engines based on the same design for agricultural tractors from Case-IH and New Holland. On a sidenote, there was a time when it used to be common to fit a 3-cyl 2.9L Diesel engine into Ford F-1000 trucks in my country as an attempt to save fuel, even though it was clearly underpowered.

An "underpowered" engine on truck chassis would seem like an opportunity to add a hybrid system... If you're alright with the upfront costs of course.

I've driven vehicles with over 30,000lbs over steep passes with less than 200hp. I wonder if there's a clear definition of what "underpowered" is or is it purely a personal point of view?

[ME_Andy]

The 7.3L is renowned for its durability. Congrats, I'm slightly jealous.

[Piotrsko]

Originally Posted by Isaac Zachary

I've driven vehicles with over 30,000lbs over steep passes with less than 200hp. I wonder if there's a clear definition of what "underpowered" is or is it purely a personal point of view?

Same here from VW bugs with 50 hp(maybe) to 50 passenger schoolbusses to trucks at AGVWR. It's not a problem with going slowly up the hill, it's the eejuts in a hurry not thinking that is the problem. If you can maintain 5 above the posted speed limit, you have enough power, extra is just gravy.

[ps2fixer]

Im my state, I can swap any engine into any vehicle, no emission testing etc. Can put older engines in newer vehicles and all that too. There's people in the states running tractor engines in their trucks, atleast a few people that I've seen videos on. One guy used small tractor engines, 3 and 4 cylinder and got impressive mpg figures, like 30+ mpg for a full sized pickup and was expecting 40mpg out of a mustang he was working on. The other guy didn't care about mpg, he has a monster columbine engine in his truck.

I'd say there's probably two basic ways to define underpowered, the typical person one would be what they feel is powerful enough probably based on experence (newer vehicles and such). Then the real world where a vehicle is loaded to it's max capacity, and has to drive up the steepest hill in the country. If it can't maintain power, I suspect it could be stated it's under powered. A 5hp briggs engine can move 100,000lbs, it would be extremely slow and need insane gearing, so getting up a hill with a giant load is more about torque multiplication than raw power. Granted double the power requires half the gear reduction.

In the context of cars, under powered is a little harder to define since the application is more about getting from point a to point b. Getting up to express way speeds would probably be what defines under powered in my book. If it can't get up to speed within the on ramp distance, then you can't properly merge with traffic going 75mph. In my area, the ramps are fairly long, but a city over they are stupid short, I mean like 300ft after the sharp bend and it's an entrance/exit ramp (clover leaf style road). Just about no vehicle of size can get up to speed fast enough. My lexus does it fine, my T100 I might hit 60mph from going 30 around the corner. My diesel I haven't driven in that area yet, but I suspect it would be more like 50mph, it's not exactly a fast truck lol.

@ME_Andy

Yea, that's the only reason I bought the truck with the 7.3L, I wouldn't touch the 6.0L and anything else it too new besides the IDI trucks, and I wanted the power stroke for the better mpg and such. These trucks had alright integrity so it's a pretty solid vehicle all around. If I couldn't get the 7.3L diesel in the format I wanted, I'd be forced to buy a newer Tundra and my 2nd best pick (like the 2006 era when the 5.7L was an option). The GVWR on the truck went up quite a bit for that generation so I suspect it would handle a larger load pretty well. Before that, they were more like a F150/1500.

@Piotrsko

I don't think you can get much more "underpowered" than a VW caddy, 47hp diesel 1.5L (I think we had the 1.6L too). People easily got 40mpg+ out of those little trucks though. I was going to buy a couple ages ago, but the guy was shady and didn't tell me the issues about the trucks and wanted $1000 each for rusted out trashed trucks.

Quick google shows the VW beetle was around 40-50hp in the 60's. 1970+ ones got around 60hp or so.




Anyway small update on the truck, glow plugs all replaced, no more smoke on startup. Oil changed, transfercase fluid changed. My dad was working on the drive shaft, I suspect it's swapped out now, haven't test drove it yet. Got a few more things and it should be caught up on maintenance and repairs. I've been focused on my business lately, so haven't really done much with the truck and haven't needed to haul anything. My dad has a line on more wood though, so fair chances I'll be using it again fairly soon. My neighbor also mentioned about wanting part of his property clear cut and stumps removed. He's not motivated though right now, he said maybe in 2-3 years.

Also, finally getting some nicer weather here, high today is 45, massive heat wave for our area lol.

[Piotrsko]

I did 750,000 miles in a 72 1600 dualport superbug, 11 engine remans, 2 trannies, 3 suspension rebuilds and numerous bearing and brake replacements. Wont even mention CV joint maintenance, but I wore out a couple of splined tool bits. When the bug had a fresh engine it would pull a 3% local hill in 4th, everything stiffer had to be 45mph in 3rd which was a bit above factory redline. After 30,000 miles it was 3rd gear to pull that hill. VW said their engine was rated at 50 BHP from the factory using the approved CALI smog accessories and I know that the cooling fan/alternator took 12 dyno'ed horse to cool at redline. Any more I find gaggle to be somewhat overly optimistic

I know people who got 50mph in VW diesel pickups between Palmdale and Tehachapi, including the infamous 3% hill. One friend clamed 70 mpg, but she wasn't taken seriously.

[ps2fixer]

That's a lot of miles on a vw bug. Pretty interesting it lost power so fast, even 30k miles. 11 engines would average out to be 68.2k miles per engine. I assume you bought all the engines from the same source? Maybe they weren't rebuilding the engine for longevity or something. Maybe that engine just isn't the great, but a ton of people use them in dune buggies, I figured that people would choose an engine because of ease of modding and longevity.

I've put 80k miles on my corolla and did feel a bit of a power decrease, but is was probably 5-10% and the engine was at 300k miles, 1.8L. I did almost nothing to the car maintenance wise besides oil. It was a beat up trashed car to start with, and I fixed the major stuff and just drove it. I took it off road a little and used it like a mini truck, I hauled scrap in it and such. Probably 2000lbs of junk stacked in the car, trunk etc and the suspension was just about maxed out. Stock it has maybe 4in of ground clearance, and with the load in it, it was more like 1-2in lol.

I've read a little more about the propane injection and every time someone mentions mpg, their claims seem very high. Basically every claim works out to around 30% gain except one that claimed a 60% gain in a VW TDI car. One guy explained how he did a DIY style install that didn't really meter the propane or anything, just based it off of pressures and the logic more psi is more flow/gas. It was an gas propane setup, not liquid, he had the first regulator right at the tank set to 10psi, and the second regulator right before the injection point set to around 1psi. He stated how long his propane lasted, and his mpg, so I reversed the logic and he's using about 20% propane vs 80% diesel by volume which is right spot on with what other people say the mix is safe at. He set it up so the propane only injected when the throttle was pressed far enough to make a little boost using a micro switch. The VW guy used a pressure switch on the boost side of the turbo to activate his propane. Seems like a combo of both would be needed and have to monitor EGT's. The VW guy used a fork truck vaporizer and used liquid propane and used a solenoid to turn the propane on/off and the injection point was before the turbo. He didn't speak english super great, and I don't think he knew how the system worked too well, seemed like he bought it as a kit from somewhere or something.

Anyway, at the 20% level, I think that's pushing the limits a little for how much propane is added, I was thinking starting off around the 10% mark. Of course I'd need to buy the propane solenoids and such to try this.

The guy doing the double regulator setup claimed 29mpg out of his truck, but he didn't give much info like auto/stick, gear ratio etc. He said his normal mpg was around 21-22mpg which is just over 30% gains.

If this propane setup is truly good for 20%+ gains, I don't understand why every diesel doesn't run propane with it. The fuel savings alone would easily pay for a proper system within 50k miles. Of course I'm assuming bulk propane prices, not the $20 for a 20lber refill which is over $4/gal.

It would be interesting to put this idea to the test and figure a way to meter mpg fairly accurately for quick aba style tests at different amounts of propane, say 0%, 1%, 5% 10% 20% for starts. It would be interesting if it only took a tiny amount of propane to get the mpg benefits.

I do need to get a gauge for EGT and get some base line numbers. From what I read, EGT at low load with diesel + propane is less than normal diesel, but at higher loads (and more propane in a digital system) the EGT can get too hot so either needs to be turned off or keep out of the throttle. People online said the extra power comes in low to mid rpm which sounds perfect for mpg and daily driving.

Assuming the 26.6mpg is accurate for the expressway trip at 60mph, a 30% gain would be 34.6mpg, add some areo mods and in ideal situations the truck could pull some impressive numbers, but that's a lot of assuming and theory talk. Hitting a typical driving average of 25mpg I think would be a pretty solid goal to start with, and more or less confirm the more ideal mileage when I take a long trip again.

[Tahoe_Hybrid]

Originally Posted by ps2fixer

Tell that to my fuel usage vs distance traveled. I know the fuel tanks aren't great for being consistent so that tank might be abnormally high, but not quite that much. The next tank ended up being around 16mpg, averaged together it's still 20mpg, double of what you state.

I don't drive the truck like I stole it, it's a stick, and it's got the highest geared axle it could come with stock, 3.55. The topper on it helps slightly with areo. My dad's is the same thing but 4.10 gearing, no topper, and he was getting 15mpg with a tuner and beating the snot out of it. Both trucks have stock sized tires, not 40in like a lot of people like to do.

Generally speaking, the physical shape of a fuel/gas tank is tapered in at the top, so it should hold less fuel at the top vs the bottom. However if you're using the fuel gauge, then it depends how the OE company designed the float in the tank. I've had vehicles that were very linear like my corolla, while my dad's Camry goes 80+ miles before coming off full. Tank mounted angle and a ton of factors effect the reading including the wiring, connectors etc. It's a resistive based reading.

Anyway, as I drive the truck more, the mpg I'm getting should average out and become more and more accurate. Ball park 20mpg is right in the range I see a lot of people claiming with similar gearing and similar speeds.

Remember, this isn't the 7.3 IDI engine, it's the power stroke. It injects the fuel at much higher pressure which makes it burn better, plus the computer has more control over timing and such. I've seen some claims that the IDI's can do alright, but that's with modifying timing and injection amounts (like tuning a carb).

Empty a 4 cylinder would give better mpg I'm sure, but make the whole vehicle weight 19k lbs and that 4 banger will have a heck of a time with hills. 7.3L isn't my first pick for engine size, there's no real happy medium in the diesel world for Ford's. A cummins swap could give better mpg, but the cost of another truck, doing the swap etc will likely far outweigh any fuel savings I'd have. No point in spending a $1 to save $0.01.



Cylinder deactivation would be a neat concept on a diesel. I wouldn't trust Ford's electronics to do a good job though if it was designed that way from the factory (like their gas 8-6-4 setups, people always seem to have problems with it). I suspect an cylinder not getting fuel for extended times might have excess wear, but I don't know how the oil circuits are in the 7.3L. Moving the "dead" cylinders around would offset that issue, but then it takes a fast computer to process which cylinders to kill and such.

Ironically, I had a through of what the 7.3L would be like as a 4 cyl. It would turn into a 3.65L. I saw a video of someone reworking an engine and claiming to recover enough heat out of the engine to not need a radiator. If I remember right, one of the engines he did was the 4.3L v6, but turned it into a 3 cylinder. The head was removed and I suspect a block off plate was added, not sure how the actual cylinder deactivation was done, might have removed the pistons, or maybe they were left in to keep balance. I can't seem to find the video or any pages about it now. I do remember one of the things he did with the heat was pre-heat the gas coming into the engine. If I remember right, the target was just below the boiling point, or maybe it was over the boiling point but under pressure where it didn't boil till sprayed into the cylinder. I figured it was more on the lines of conspiracy theory, but I don't think the guy was claiming super crazy numbers and he converted several engines.

Anyway, a 3.65L that was tuned a bit hotter than factory with a turbo that works well with it and intercooler might meet my needs for hauling and give good mpg while empty. Most 4 cyl engines seem to be half that size so it would probably have a nice vibration running too lol.

also the cylinder deactivation works just fine if something goes wrong it's operator error i.e 7-10k oil changes...

there is many many engines that ran 1/2 as an air compressor those has the lest amount of "wear and tear"


if you check any AFM engine their will be more wear on the AFM cylinders then the non AFM cylinders

MY AFM engine barely runs at 1800rpm at 85mph (superOD 3.08 rear end) in v4 mode yeah this is less then an actual 4 banger which would be at 3500 to 3800rpm
this is double the weight too...


(the faster the engine runs the more wear it gets)


No vibration running if the correct cylinders are disabled.. all ready told you which ones AFM engines use special lifters for cylinders 1, 4, 6, and 7 which turn them "off" i made a mistake on the other post so it runs 2-3-5-8 cylinders which balances the engine