[Lonno]

yes its heavy, its converted to 4x4, with a popup camper top and is like the original poster was asking about running a 4bt in. but its not heavier than my truck.
Also, your automatic is going to suck more fuel around town than a stick in your 98 truck. dodges soggy torque converters suck fuel in town.

Yeah, I keep waiting for the tranny to start slipping so I can upgrade it and the t/c but sum bitch keeps hanging on. My 2001 Ram got better mileage with a built trans and triple disc t/c and I had that thing tuned pretty hot.

 

[dieseldude]

I am almost afraid to coment on this thread.
I have two trucks both standard and 4x4 with 4.10 gears both weigh about the same only 100-200lbs differance one has a ve6bt and one a ve 4bt.
I have compaired mileage and the 4bt gets on average 4 mpg better doing the same thing but is slower when loaded.
If I were building a vehicle that weighted 7000lbs loaded and it saw more secondary roads than interstates, towed under 5000lbs infrequently and fuel costs go back to $4+ a gallon, (as we all know they will) I would consider the 4bt.
If the vehicle is 7000lbs empty and I loaded it heavly or towing frequently or a 4bt is very expensive to aquire I would use a 6bt

 

[Russ McLean]

Added for the..... err.. discussion:

1998 Dodge Ram 6bt, 2wd, 47re, roughly 7k #'s, 3.54 rear, stock tire size, stock height with a shell so fairly aerodynamic. 50/50 town/highway driving. 16/17 mpg mildy driven. If I drive aggressive it's 14/15.

1970 Ford F250 4bt, 2wd, M5R2 5 speed, roughly 6k #'s, 3.73 rear, 33" tires, Lifted 5", very non-aero-dynamic. 50/50 driving is 22/24mpg. Hard driving might go into teens but I haven't seen a tank less than 20 in a long time.

I tow nothing so I cannot add to the DISCUSSION how mileage would react with a load. The 4bt might lose 5mpg for all I know pulling something heavy. I know the 4bt would rather have a small load than be empty. Truck responds much better when pushed up hill or pulling my boat (very light).

Let's keep this one open and civil guys. Good info in here.

Dave

>> "Let's keep this one open and civil guys..."

An example of the same 4BT engine (CPL #727) owned & operated by me.

1. Bought a 1986 Ford / Grumman bread truck and drove it home 320 miles. Shorter box, single wheel axle, 16.5 series tires. History unknown, I "believe" that I am the 3rd or 4th owner. The engine de-fuled at 56 MPH. Ran it locally for several months. Fuel consumption ran above 15 MPG.

2. Started working on the 4BT "tune" in the bread truck. Pyro, Tiny-Tach, piston fuel pump, older Dodge intercooler, VDO 85 MPH programmable speedometer. Sent the truck to a buddy with 6BT experience and had him install a 3,400 RPM spring and "bump-the-timing-by-ear". The truck now willingly drove 65 MPH on the highway. It had more, BUT, the truck was not designed as an autobahn cruiser. Fuel consumption was 15 MPG +/-, depending on the speed driven and the Toes-Out-Grill factor. It did not get many months of driving, we pealed the tread on one of the ancient tires. Replacement tires were quoted at $920+. We parked the truck and went looking for a project truck.

3. Bought a 1986 Ford F150 short bed pickup. $1,000 CraigsList "wonder", dead 300 CID 6 cyl, 2x4, had to trailer it home. Same engine & tune, smaller intercooler, overdrive trans, 3:07 axle gear, moved the pyro before the turbo. Drove it a bunch, MPGs seemed to come out on the low side of 25 MPG.

4. Changed rear axle to 2:75 ratio, added the 1952 Bell Telephone System service bed. To me, the decrease in engine speed was worth it for the quieter ride, a "somewhat" better fuel economy is a bonus. Truck now weighs 4,400 pounds with tools, estimated under 5,000 pounds in full tourist mode, including 2 passengers. MPGs seem to come out above 25 MPG. Effortlessly cruised thru West Texas at 85 MPH.

5. I am financially at least 6 months away from towing my single axle travel trailer ("light weigh", but has the aerodynamics of a cinder block).

MY TAKE-AWAYs:

1. The 4BT is a wonderful engine for a lighter vehicle that does not have to punch a large hole in the air. The 6BT is a better engine for heavy loads and/or high aerodynamic loads.

2. The current primary source of 4BT engines are take-outs or cut-outs from Hostess Bakery trucks. Be wary, Hostess went bankrupt twice, they ran the living snot out of these trucks.

3. Folks are finding that 6BT engines are often cheaper that 4BT engines.

4. "Your mileage may vary <wink>.

 

[boothybunch]

it's like i said in the beginning.

Swings and roundabouts.

Build it to SUIT YOUR SITUATION.

 

[eggman918]

Yoru right it would have been cheaper/easier to do a 6BT in my truck but it was too damn heavy/long to fit "comfortably" in it and I imagine that I will need to overhaul the 4 sooner than if I had shoehorned a 6 in it,but I think that I ended up with a better balanced package overall with the 4 but every build is a series of compromises.

 

[Dougal]

Good lord you are hard headed. Let me say it again for the cheap seats: ENGINE FRICTION IS NOT THE SUM TOTAL OF ENGINE-RELATED LOSSES !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! IT ISN'T EVEN THE BULK OF ENGINE RELATED LOSSES! ACCESSORIES ACCOUNT FOR MOST PARASITIC HP LOSS.

Here's my list:

Engine fan
Water pump
PS pump
Alternator
AC compressor
Lift pump
Injector pump (scales with cylinder count, but not linearly)

By including losses that don't scale with cylinder count. As I stated above (and you will likely ignore).

I get 72.5kw to climb an 8% grade at 65mph (typical speed limit), NOT INCLUDING drag (which you're guessing), drivetrain loss (again a guess), and rolling resistance (which you neglect). 70kw would be insufficient, while 115kw would leave you with no power to spare. Now, hook up a 3500lb trailer.

I happen to have a vehicle and trailer combo that weighs 5 tons combined. With the engine bone stock it took full throttle to maintain ~60MPH at 1850RPM on a 7% grade. That is real world experience. With a 4BT I would be turning 2500RPM and burning way more fuel than I do with the 6. These climbs aren't short, either; I live at an elevation of 1200ft, and travel to elevations between 7000 and 10,000ft. A 4BT would be absolutely miserable in my truck, and the OP's rig is likely to be used the same way.

The engine friction on the 4BT (CPL2303) doesn't include automotive accessories like PS or AC as the data is from an industrial engine spec sheet. The alternator, if included in the test, is only maintaining volts on a new battery so doing very little.
That leaves you with the lift pump which takes maybe 0.2kw (insignificant), then injection pumps, water pumps and cooling fans which do have 50% more work to do on an engine that is 50% bigger.
The 9 and 14.5kw I mentioned earlier are without accessories. Your PS, AC etc are all additional. They are also the same no matter which engine you choose.

The aero drag in my example is ~26kW and the total is 100kw at the ground. Weight is 3500kg (7700lb) and the example was to show what speed you could maintain up 8% at 1800rpm with 100kw at the wheels.
The 72.5kw you've got is just the power to climb the grade. Which is correct.

Why do you keep trying to twist the example to favour a 6BT? If towing significant weight at highway speeds at high elevations was important to the OP he'd be mentioning that.
Discuss each engine on it's merit's. The 4BT has a clear and distinct fuel economy advantage. We all know the 6BT is capable of more power. No-one is claiming otherwise.

It's amazing the discussions that can be had when everyone keeps civil and respectful!

 

[ryanroo]

I am almost afraid to coment on this thread.
I have two trucks both standard and 4x4 with 4.10 gears both weigh about the same only 100-200lbs differance one has a ve6bt and one a ve 4bt.
I have compaired mileage and the 4bt gets on average 4 mpg better doing the same thing but is slower when loaded.

Haha! agreed!

while a cool comparison, unless the two engines were installed in the same truck, and you used a meter to actually measure the amount of fuel going through each engine to do the exact same thing, all we have is an idle comparison. we are not even taking into consideration the set up on each engine. both may have VE pumps, but what of injector size, turbo variables, exhaust size and routing, etc? is one engine set up to be more efficient than the other?

there are so many variables to each individual truck and each person building it that to say so and so has a 6 that does this and such and such has a 4 that does this is all pretty moot as far as factual data goes.

while i appreciate the data being shown, i dont know how the isuzu engine ever came into question. i thought the decision was between 4bts and 6bts? none the less, is the question simply which uses more fuel, or which will provide the driver with the most fulfilling experience? perhaps the two are interchangeable, but they are not for me. i like to know i have power on tap for what i want to do. having driven b series in both 4 and 6, i was more impressed with the 6. it was better to drive and was in a bigger heavier vehicle. to me anyhow. i also like big blocks and gas station coffee, so i dont mind a fuel stop.

i really doubt that the best way to decide what is the best engine for this usage is hammering engineering documents and lab calculations/measurements back and forth. those things very rarely matter when building a custom vehicle. driver temperament and expectations and vehicle use/limitations are a much better source of intel when it comes to making a build plan. so what we need to know, is the absolute deciding factor fuel consumption, and if so, what does the rest of the vehicle set up and actual use look like?

 

[Dougal]

Haha! agreed!

while a cool comparison, unless the two engines were installed in the same truck, and you used a meter to actually measure the amount of fuel going through each engine to do the exact same thing, all we have is an idle comparison. we are not even taking into consideration the set up on each engine. both may have VE pumps, but what of injector size, turbo variables, exhaust size and routing, etc? is one engine set up to be more efficient than the other?

there are so many variables to each individual truck and each person building it that to say so and so has a 6 that does this and such and such has a 4 that does this is all pretty moot as far as factual data goes.

while i appreciate the data being shown, i dont know how the isuzu engine ever came into question. i thought the decision was between 4bts and 6bts? none the less, is the question simply which uses more fuel, or which will provide the driver with the most fulfilling experience? perhaps the two are interchangeable, but they are not for me. i like to know i have power on tap for what i want to do. having driven b series in both 4 and 6, i was more impressed with the 6. it was better to drive and was in a bigger heavier vehicle. to me anyhow. i also like big blocks and gas station coffee, so i dont mind a fuel stop.

i really doubt that the best way to decide what is the best engine for this usage is hammering engineering documents and lab calculations/measurements back and forth. those things very rarely matter when building a custom vehicle. driver temperament and expectations and vehicle use/limitations are a much better source of intel when it comes to making a build plan. so what we need to know, is the absolute deciding factor fuel consumption, and if so, what does the rest of the vehicle set up and actual use look like?

The Isuzu was bought up as an example of a similar engine to the 4BT but with far wider factory fitment. So you can see examples other than backhoes and bread-vans to show how they do in other applications. The factory 4x4 Isuzu NPS is a common RV chassis. These are 92/93 models with the 4BD1T.

IMO you need to consider each important point separately (weight, space, fuel economy, power, parts availability, cost etc) and then decide on which engine is best overall. The perfect engine for an application usually doesn't exist or is way outside budget. So you pick the best compromise.
And yes you have to like driving the end result too.

 

[MaxPF]

Added for the..... err.. discussion:

1998 Dodge Ram 6bt, 2wd, 47re, roughly 7k #'s, 3.54 rear, stock tire size, stock height with a shell so fairly aerodynamic. 50/50 town/highway driving. 16/17 mpg mildy driven. If I drive aggressive it's 14/15.

1970 Ford F250 4bt, 2wd, M5R2 5 speed, roughly 6k #'s, 3.73 rear, 33" tires, Lifted 5", very non-aero-dynamic. 50/50 driving is 22/24mpg. Hard driving might go into teens but I haven't seen a tank less than 20 in a long time.

I tow nothing so I cannot add to the DISCUSSION how mileage would react with a load. The 4bt might lose 5mpg for all I know pulling something heavy. I know the 4bt would rather have a small load than be empty. Truck responds much better when pushed up hill or pulling my boat (very light).

Let's keep this one open and civil guys. Good info in here.

Dave

A friend on the other side of town has a 72 4WD Suburban with a 93 6BT (VE pump), NV4500, 205, 3.73 gears, and 33" tires. I don't know what his current mileage figures run, but 20-21 was typical in the past. On one trip he was on the road for a LOT of miles at high speed. Here's his words for that trip:

So, 4450 miles eh?? Yep, 4450 miles door to door. I forget the exact number of gallons used, but it worked out to just barely under 19mpg. Something like 18.975?? That is pretty good considering how many days we spent at 80mph with headwinds, crosswinds, but seemingly no tail wind. Imagine that, no tail winds??

Not bad for operating so far above the engine's peak efficiency RPM. Had he kept his speed down to 65 (which is 10mph below the speed limit on most interstates) he would have no doubt been in the low 20's.

 

[MaxPF]

The engine friction on the 4BT (CPL2303) doesn't include automotive accessories like PS or AC as the data is from an industrial engine spec sheet. The alternator, if included in the test, is only maintaining volts on a new battery so doing very little.
That leaves you with the lift pump which takes maybe 0.2kw (insignificant), then injection pumps, water pumps and cooling fans which do have 50% more work to do on an engine that is 50% bigger.
The 9 and 14.5kw I mentioned earlier are without accessories. Your PS, AC etc are all additional. They are also the same no matter which engine you choose.

The aero drag in my example is ~26kW and the total is 100kw at the ground. Weight is 3500kg (7700lb) and the example was to show what speed you could maintain up 8% at 1800rpm with 100kw at the wheels.
The 72.5kw you've got is just the power to climb the grade. Which is correct.

Why do you keep trying to twist the example to favour a 6BT? If towing significant weight at highway speeds at high elevations was important to the OP he'd be mentioning that.
Discuss each engine on it's merit's. The 4BT has a clear and distinct fuel economy advantage. We all know the 6BT is capable of more power. No-one is claiming otherwise.

It's amazing the discussions that can be had when everyone keeps civil and respectful!

I'm not trying to "twist the example to favour a 6BT". You, on the other hand, appear obsessed with fuel economy at the expense of other realities. I never said the 4BT cannot get better fuel economy, I said the difference was small. And in percentage terms, it is.

In the post above I mentioned a friends 4wd 'burb which routinely gets ~20-21mpg (when he's NOT doing 80mph). Lonno's 2wd F-240 gets 22-24. So, for only a 10-15% penalty in fuel consumption you (potentially) get 50% more HP and torque. This directly translates to driveability and overall enjoyment of the vehicle. Most people are willing to sacrifice 10-15% in fuel consumption for 50% more power and torque. Particularly when the 6ers are commonly much less money to buy. THAT is reality.

If the OP wants 4BT fuel consumption with 6BT power he can find himself an ISB3.9 or ISB4.5. Uness he miraculously finds a smoking deal on an ISB 4 cylinder he will pay dearly for those couple extra mpg; the typical price difference can buy a LOT of diesel fuel. And in the end the larger engine can still make more HP and torque. To me, the main reason to choose (and pay more for) a 4 cylinder diesel if if the 6 is too long or heavy for the chassis. Fuel economy is a distant second.

 

[MaxPF]

I totally agree with you, But I can't comment further for fear of it being classed as attack

As long as you're not attacking someone it isn't an attack. Go ahead and tell us your observations.

 

[Dougal]

I'm not trying to "twist the example to favour a 6BT". You, on the other hand, appear obsessed with fuel economy at the expense of other realities. I never said the 4BT cannot get better fuel economy, I said the difference was small. And in percentage terms, it is.

I'm not convinced the difference is small. User reports here are in line with the approx 5mpg the engine friction suggests.

The difference between 20 and 25mpg is 25% better or 20% worse. That's huge.

Lonno's showing 6-7mpg, but the ram's slushy auto does account for some of that.
Dieseldude is average 4mpg difference.

Both these guys own and drive the vehicles themselves. It's as good as we're getting for comparison.

If we look at 6BT ram's on Fuelly there aren't any getting around 25mpg and very few breaking 20mpg:
http://www.fuelly.com/car/dodge/ram_2500/1994
http://www.fuelly.com/car/dodge/ram_2500/1995
http://www.fuelly.com/car/dodge/ram_2500/1996
http://www.fuelly.com/car/dodge/ram_2500/1997

Obviously there are petrol engines in those stats too, pulling the average down. But the higher mpg are all diesel and that's where I'm looking.

I'm pretty sure We all agree the 6BT has more power and is a lot easier to find.

 

[MaxPF]

I'm not convinced the difference is small. User reports here are in line with the approx 5mpg the engine friction suggests.

Again, the vehicle setups are dissimilar. The 'burb I referred to above is the closest to Lonno's F250. Same pump, manual trans, same gears, same tire size, similar dismal aerodynamics. The difference between them is 2-3mpg.

The difference between 20 and 25mpg is 25% better or 20% worse. That's huge.

OTOH, the differnce between 20 (72 Suburban, 6BT) and 22mpg (60-something F250, 4BT) from more closely matched setups is 10%, which is small given the difference in power and torque available.

Lonno's showing 6-7mpg, but the ram's slushy auto does account for some of that.
Dieseldude is average 4mpg difference.

Again, substantially different setups. Weight, overall gearing (including tire size), and aerodynamics need to be closely matched before you have what caould be considered even a rough comparison. For a true comparison we would need to build a vehicle and run each engine in the vehicle on a closed course for a sufficient number of miles to collect accurate data.

Both these guys own and drive the vehicles themselves. It's as good as we're getting for comparison.

Ehh, no.

If we look at 6BT ram's on Fuelly there aren't any getting around 25mpg and very few breaking 20mpg:
http://www.fuelly.com/car/dodge/ram_2500/1994
http://www.fuelly.com/car/dodge/ram_2500/1995
http://www.fuelly.com/car/dodge/ram_2500/1996
http://www.fuelly.com/car/dodge/ram_2500/1997

Obviously there are petrol engines in those stats too, pulling the average down. But the higher mpg are all diesel and that's where I'm looking.

Those era Rams were seldom geared (or tuned) for optimal economy. For a valid comparison one would need to put the same era 4BT in the same truck with the same gearing. Not something we are likely to see.

I'm pretty sure We all agree the 6BT has more power and is a lot easier to find.

And usually much cheaper

 

[Dougal]

Again, the vehicle setups are dissimilar. The 'burb I referred to above is the closest to Lonno's F250. Same pump, manual trans, same gears, same tire size, similar dismal aerodynamics. The difference between them is 2-3mpg.

The only similarities are the drivetrain.
The vehicles have completely different shapes and aerodynamic drag. On top of that you have different drivers in different areas driving them in completely different ways and also recording fuel consumption in a diffferent manner.

The differences far outweigh the similarities here and it's all relayed as 3rd hand information. You'll need to come up with a far better example.

I can guarantee in that slew of Ram's on Fuelly there are several regeared for higher mpg. It's a massive amount of data on a whole range of vehicles and none are seeing 25mpg.

Yet our members here with 4BT's are doing far better: http://www.4btswaps.com/forum/showthread.php?6254-Fuel-Log
Throw out the out-liers (extreme highs and lows) and you've still got many in the very high 20's.

 

[MaxPF]

The only similarities are the drivetrain.
The vehicles have completely different shapes and aerodynamic drag. On top of that you have different drivers in different areas driving them in completely different ways and also recording fuel consumption in a diffferent manner.

The differences far outweigh the similarities here and it's all relayed as 3rd hand information. You'll need to come up with a far better example.

Yet you're perfectly fine comparing two completely different vehicles with completely different drivetrains

I can guarantee in that slew of Ram's on Fuelly there are several regeared for higher mpg. It's a massive amount of data on a whole range of vehicles and none are seeing 25mpg.

Massive amount? There are 28 trucks in the 1996 data. The rest have less. You cannot "guarantee" anything about gearing since nobody specifies their drivetrain. The highest probablility suggests they are largely stock, and many may have larger than stock tires which negatively impacts fuel economy. Were the trucks empty or loaded? City, highway, or mixed. Driving style?

Yet our members here with 4BT's are doing far better: http://www.4btswaps.com/forum/showthread.php?6254-Fuel-Log
Throw out the out-liers (extreme highs and lows) and you've still got many in the very high 20's.

The high (or even mid) 20's are not in heavy venicles. If they are, well, I will be polite and call the data extremely suspect.

There are a couple on the first page alone that I can compare my vehicle to. The first is in post 15:

9944 miles AVG:19.4mpg to date 88 k5 blazer, 4.5" lift, 33 BFG M/T's, 3.42 gears, 3200 spring, 4l80e trans low stall converter
I'm becoming more and more skeptical of the 30mpg+ guys, I hope to find the secret one day

Here's another one:

Trip mileage: From Mesa AZ (elevation 1200 ft) to Chiricahua Natl Mon (elevation 5124 ft). and back, 535 miles (861km)
Four days , three nights.
The Scout towing the Casita 17'.
Speed: set for 65 mph, (104 km/h), 1900 RPM.
Stuck to back roads where we could, most were posted for 65 mph, some less, some freeway.
Gross Combined Weight, about 8000 lbs, (3628 kg)
Mileage up to Chiricahua Natl Mon, , 17.42 mpg
Return milage 19.91 mpg
Trip average 18.66 mpg
Fuel cost per mile @3.99 gal $0.23

This guy lives in the same town I do, and that trip is similar to trips I take (although I am usually loaded heavier). Neither of those vehicles do much better than mine.

 

[boothybunch]

As long as you're not attacking someone it isn't an attack. Go ahead and tell us your observations.

There is NO POINT saying anything because it get's removed at the smallest provocation. There are those that are right some of the time and those that are wrong none of the time.

BUT

There is no point (or fun) building a vehicle that has a limited use. How many times does your life stay they same day it, day out.

I have dealt with Rv's and everytime they have stated it's 7000 lb, it's been closer to 8500 or more.

NOW, If you could lay your hands on a 4bt and use it with an aux transmission, you could have your cake and eat it, but they are getting thin on the ground.

Look at EVERY ASPECT of the vehicle. If your going to be held to aiming for HIGH mpg, you might ruin something else. No point arguing over My mothers brother sisters uncles got a mate that get's 15mpg on a 4bt that's got 5000000 on the clock or the dad's mistress monday night one night stand shag that's got a 6bt that does 40 mpg. It's the dick behind the seat that controls the MPG. If you happy to cruise all day at 40mph, gear it for that. if you need more top end, you need to gear for that.

Your better having a reserve of power in case you need it than NOT having any.

If I was building this vehicle, I would rather have the 6bt and run a standard drive train that can be fixed almost anywhere and have a reserve of power because your gonna be running big wheels/tires and you will need ground clearance.

People start with fixed intentions, then they get side tracked

 

[Lonno]

In the post above I mentioned a friends 4wd 'burb which routinely gets ~20-21mpg (when he's NOT doing 80mph). Lonno's 2wd F-240 gets 22-24. So, for only a 10-15% penalty in fuel consumption you (potentially) get 50% more HP and torque. This directly translates to driveability and overall enjoyment of the vehicle. Most people are willing to sacrifice 10-15% in fuel consumption for 50% more power and torque. Particularly when the 6ers are commonly much less money to buy. QUOTE]

High teens is very impressive mileage especially for going 80. The 98 will be @ 2300+ rpms at or around 75mph and I'm sure the mpgs are not good in that range.

But I also don't care about the mileage, between the 2 trucks I visit the gas station maybe once a month. The 4bt is much more pleasant to drive (other than the noise ) than the 6. Not just because of the auto but the full size diesel transmission ratios are geared more for towing/hauling than normal DD. My 4bt may have less hp/tq but it is much faster, lighter, and peppier around town. Highway comfort goes to 6bt.

I'm not trying to push either one gents, just offering my 2 cents.

 

[scout4bta]

Yet you're perfectly fine comparing two completely different vehicles with completely different drivetrains

Massive amount? There are 28 trucks in the 1996 data. The rest have less. You cannot "guarantee" anything about gearing since nobody specifies their drivetrain. The highest probablility suggests they are largely stock, and many may have larger than stock tires which negatively impacts fuel economy. Were the trucks empty or loaded? City, highway, or mixed. Driving style?

cut……….

This guy lives in the same town I do, and that trip is similar to trips I take (although I am usually loaded heavier). Neither of those vehicles do much better than mine.

I've taken the same trip towing the Casita using my 92 Dodge 5 speed manual, stock 5.9-160hp, with factory gearing, tires and it gets 3 mpg less. Dodge is turning 1920 rpm and Scout is turning 1870 rpm @ 65 mph. For me that's a big incentive to use the Scout more.

 

[ryanroo]

The only similarities are the drivetrain.
The vehicles have completely different shapes and aerodynamic drag. On top of that you have different drivers in different areas driving them in completely different ways and also recording fuel consumption in a diffferent manner.

The differences far outweigh the similarities here and it's all relayed as 3rd hand information. You'll need to come up with a far better example.

I can guarantee in that slew of Ram's on Fuelly there are several regeared for higher mpg. It's a massive amount of data on a whole range of vehicles and none are seeing 25mpg.

Yet our members here with 4BT's are doing far better: http://www.4btswaps.com/forum/showthread.php?6254-Fuel-Log
Throw out the out-liers (extreme highs and lows) and you've still got many in the very high 20's.

what are you using to back the guarantee? third hand info?

you are using Lonno's trucks as a valid comparison, but they dont even have a similar drivetrain. 4bt is ve pumped. the 6bt is p-pumped. we all know the inline pump will hurt mileage compared to the ve just because of the static timing. these are completely invalid comparisons. both are modified in some way. that makes the comparison moot again. the same reason why dieseldudes trucks are not a for sure comparison either. they are close to the same, and i would take that as more valid comparison, but without knowing the build on both rigs and what they are it is just speculation as to why or what causes the difference.

Yet you're perfectly fine comparing two completely different vehicles with completely different drivetrains

this is why i question calling into view the data on an 4bd1-t info and NPS chassis. its like comparing a 5.0 mustang to a 5.0 camaro. one is a roach and the other works well. just because they are similar in size doesnt make them a good comparison. if we are going to the effort of calling technical data up to back an argument it needs to be technical data for the engine in question or it certainly cant be taken as evidence for one side or the other. it is just circumstantial.

IMO you need to consider each important point separately (weight, space, fuel economy, power, parts availability, cost etc) and then decide on which engine is best overall. The perfect engine for an application usually doesn't exist or is way outside budget. So you pick the best compromise.
And yes you have to like driving the end result too.

agreed. this is why the question i ask is what is the absolute restriction on the build, happiness with end result or fuel economy, and what circumstance is that economy value going to be in question.

that converted camper rig is sweet. needs a desert tan paint job and it would be perfect.

A friend on the other side of town has a 72 4WD Suburban with a 93 6BT (VE pump), NV4500, 205, 3.73 gears, and 33" tires. I don't know what his current mileage figures run, but 20-21 was typical in the past. On one trip he was on the road for a LOT of miles at high speed. Here's his words for that trip:

Not bad for operating so far above the engine's peak efficiency RPM. Had he kept his speed down to 65 (which is 10mph below the speed limit on most interstates) he would have no doubt been in the low 20's.

that sketchy bearded dude is a notorious hack and a liar! haha.

while still third hand info, i know this guy as well. he has no reason to lie about the performance of his burb. he doesnt care what any of us think. it is one of the best conversions i have ever looked at. everything is well executed and top quality. there is no need to question his results. he is more than intelligent enough to do the mileage calcs and like i said, he doesnt give a poop if we believe him so he isnt going to lie.

i wonder what the difference would be on his burb after the turbo swap? i would bet if he ran that trip again now that the turbo is more efficient he could do a little better.

regardless of any of this, i think we can all agree that on a test stand the 4bt will win the consumption argument. if the 6 was going to be more efficient, would they have even made the 4? the differences will come from application and driver. so if the absolute bottom line is fuel consumption, put the 4 in it. just make sure it is set up to be efficient. if the same variables that we all have to consider when building a custom apply to this build as well, then there are more questions to be asked of the OP and more info needed.

 

[roachie]

I've had 3 6bt powered 3/4 ton trucks that averaged over 20-22mpg. If a full size truck is only getting 25 with a 4b I cannot see any reason to use one.