Cummins 4BT & Diesel Conversions Forums banner

1 - 19 of 19 Posts

·
Registered
Joined
·
1,453 Posts
If high MPG is your highest priority, buy a VW TDI and keep it in good repair.
 

·
Registered
Joined
·
11,029 Posts
There are just some many things that can affect fuel mileage. A company named Trident Sports Cars in the UK has built what might be considered the ultimate diesel sports car. Beautiful design, super powerful (top speed in the, 190 MPH range), and when driven in a sane manner gets 58 MPG. Not sure of current price but when it came out 6 years ago it was $162,000. That sort of eliminates most of us from that consumer market. As Russ said, the VW diesels have a great reputation for fuel mileage. We have one member who's running a 4bt Cummins in a hot rod and can get into the 40 MPG range. That is not normal for most applications. Low to mid 20's is most common. First you have to decide what type of vehicle you want and need.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #4
I have access to a 4BT, as of right now it will be the project. I was pretty vague in my original request. I am leaning towards a 95 suburban 4x4 or a 91 f150 2d as the donor, both having factory OD automatics in them. I am guessing there adapters available to mate the motor/tranny. I am really leaning towards the F150 since my drag cars are mustangs...stick to the ford theme maybe. Or I have a roller foxbody coupe that might make a interesting swap. I am thinking more long the lines of a 1/2 ton truck. I have hotrods and currently working on a 42 willys cj2a kabota swap then this would most likely round out s my last swap/retirement truck. I don't need big power on this one.
 

·
Registered
Joined
·
1,453 Posts
My 1986 F150 (see build thread below) is similar to your 1991 F150. The big difference is no automatic, I do not have direct experience with auto trans. Sticking an OD automatic behind a 4bt is not a trivial matter. Involves adapters and computers for any recent trans. The stock 1995 Chevy trans has a reputation of quickly failing under 4bt torque (lots of low RPM torque that the trans is not designed for).

My F150 has over 70,000 miles and 37 states on it. I get in the low/mid 20's MPG - have not measured it in years - The 4bt loves to run down the interstate with the cruise control turned on (at the speed limit (or maybe just a little bit more)).
 

·
Registered
Joined
·
11,029 Posts
If you want to do a automatic on the Ford, you need to know which one it has. It could be the E4OD. Which engine does the truck have now? If it's the 300 I6, 302W, or 351W it will have the small block Ford bellhousing. The small block Ford adapter plate is found on a lot of 4bts. They were all manual transmission but it can be adapted to an automatic. You'd need the flex plate, spacer, and wave ring assembly to mate to the torque converter. You'll also need a 6 bolt torque converter with a stall speed in the 1300 RPM range. The Ford diesels used a 6 bolt. You'll also need an outboard controller to mate it to the Cummins as that transmission was electronically controlled. This is all pretty much standard when mating most newer automatics to a Cummins. A somewhat better transmission that came out a bit later was the 4R100. Same mods still apply. One mod that must be made to the Cummins adapter plate is making a hole to access the torque converter bolts. Since the Fords were all manual there was no provision for it. Here's a photo of a modified adapter. The big round hole near the bottom is for that purpose.
 

Attachments

·
Registered
Joined
·
11,029 Posts
Yes, that's why the lion share of our swaps are manual transmissions. Some people just want an automatic and there's no issue there, but cost tends to be a lot higher. The cheapest automatics would probably be the Dodge units that came behind the Cummins . The 46RH, 47RH, and 47RE could all be adapted to a 4bt using stock Dodge Cummins parts. The 47 series had a lock up torque converter which would give better mileage. The RE series would require an outboard controller since it's computer controlled. If you are looking at MPG numbers, the manuals will usually be higher than the automatics. The 91 Ford you mentioned won't have much in the way of computer controls. The next series of truck after that had more. A sort of ideal swap candidate would be a Ford F250 in the '87-91 range that had a diesel. No computer junk in one of those at all. I drive a '90 F250. It costs a bit more to adapt a Cummins to those but you don't have to worry about frame strength or much anything else. The one main item you'd need to change is the radiator. The monster size unit in those would be way too big for a 4bt. Fine if you were going 6bt.
 

·
Premium Member
Joined
·
867 Posts
Had used a Nissan Qashqai, VW and a Skoda in the UK, all diesel and manual and all could get 50+ MPG (Imperial gallon) (17 plus K's to the litre)
 

·
Registered
Joined
·
2,180 Posts
The Wife and I have been kicking around the idea of a late '60's Ford Galaxie with a "200HP" 4bt mated to the double OD ZF S6-40. Being a "Big block" car with a full frame I doubt the 4BT would overtax it could make a nicely balanced
jTK5D.jpg
package with a little thought.
Thinking this would get unbelievable mileage with a fair amount of Show & GO ability.
 

·
Registered
Joined
·
1,453 Posts
Love it !!!! A Dodge/6bt combo power steering/vacuum pump will allow you to use the stock power steering, vacuum brakes and vacuum accessories (good luck on finding a stock vacuum heater control that still works). I have a Dorman replacement pump ("improved" design - not rebuilt) that is trouble free so far.
 

·
Registered
Joined
·
26 Posts
That would be one sweet cruiser! Always liked the Ford Galaxies.

On a different note speaking of double overs, has anyone tried Chevy's 6l90e behind a diesel?
I hear ya loud and clear on the zf; I'm a "handshaker" guy too, especially enjoy shifting roadrangers, and all my vehicles are standard. But my nv4500 with 3.73's isn't tall enough for me and the 6l90e is one auto I have come to like.

A company called Zero Gravity Performance has a kit I haven't heard of anyone running one.

I'll probably just swap to 3.42's if I ever have a good excuse but just thought I'd ask.
 

·
Registered
Joined
·
26 Posts
Back to Brushtrooper's post,
I have know clue what type of vehicles tickle your fancy, or what constitutes your idea of a high MPG vehicle; whether you are thinking of a daily commuter, a cruiser, or a working truck etc.
But we have to remember that we simply can't change some given facts
  • It takes X amount of energy to move X amount of weight at X speed.
  • Wind resistance multiplies the faster you drive.
  • There are only X BTUs of energy in each gallon of diesel fuel.
  • We live in an imperfect world=nothing can possibly be 100% efficient
So to a certain extent whether you are using a 1.9, 3.0, 3.9, 5.9, or a 7.6L engine, it will still take X amount of fuel to move 4875lb. at 73 mph at the same wind resistance and engine/drivetrain efficiency. So to get better fuel mileage we need to change one of the variables in the equation.
  1. Lower the weight.
  2. Lower the speed.
  3. Lower the wind resistance.
  4. Increase the efficiency of converting of diesel fuel to useful power.
Thick books could be written on the subject of increasing efficiency but here's some of the basics.
  1. Proper gearing, this is by far the big one. Especially with diesel engines the gears will make or break the vehicle. Even on a semi truck you'd think if you had 18 gears to pick from that you'd always have a gear where you need one. Not so, if the truck is not spec'd with the correct gears for the type of work it's doing it is a pain to drive, is not efficient and has more wear and tear. You weren't specific what engine you were thinking of but it should be geared to be at rated peak torque rpms at your projected operating speeds simply because that is generally where diesels are most efficient.
  2. Advancing injection timing (simply giving the fuel more time in cylinder to burn more completely)
  3. An efficient and properly sized turbo charger. (Personally I think a vgt charger would the cat's wiskers on a dedicated MPG rig)
  4. Decrease parisitic drivetrain loss (think standard gearbox vs. an auto trans; 2wd vs. 4x4; some would go as far as to run a lighter weight synthetic engine oil)
There's more be said but it's late and I'm tired. Maybe some others that have more actual tested and proven tricks will chime in.
The thing with diesels is the ability to tinker 😏 with them😉! And so many variables compared to a gas engine's fixed a/f ratio!
 

·
Registered
Joined
·
6 Posts
It can be done without resorting to a shoebox car. My son has a 2016 BMW 328d. It has an 8-speed automatic and he gets from 45 to 50mpg. It's a nice car! It does take the engine 30 miles to warm up when it's below freezing, but it has an electric heater so you never know it.
 

·
Registered
Joined
·
8 Posts
I have access to a 4BT, as of right now it will be the project. I was pretty vague in my original request. I am leaning towards a 95 suburban 4x4 or a 91 f150 2d as the donor, both having factory OD automatics in them. I am guessing there adapters available to mate the motor/tranny. I am really leaning towards the F150 since my drag cars are mustangs...stick to the ford theme maybe. Or I have a roller foxbody coupe that might make a interesting swap. I am thinking more long the lines of a 1/2 ton truck. I have hotrods and currently working on a 42 willys cj2a kabota swap then this would most likely round out s my last swap/retirement truck. I don't need big power on this one.
the average Ford Overdrive automatic transmission won’t do well with a 4BT in front of it. It’s best to have diesel specific trans because unless one of these guys has done the conversion and has a program guide, you’re looking at a specific setup but custom computer programming.
There is a reading UPS used the Chevy trans.
 

·
Premium Member
Joined
·
115 Posts
Any suggestions for build gear towards hi MPG. Any thoughts/suggestions
Google Michael Vanozzi's Hot Vapor engine. I think his patent was recently granted. He has a FB group, and has offered his design to anyone who wants to build it. His system is for a 350 Chevy SB. Plus it uses a turbo. Check it out. Tell him Gene Climer sent you.
 
1 - 19 of 19 Posts
Top