49mpg possible from full size mechanical diesel?

[bondvagabond]

I have by standing on the shoulders of giants, (Jacob aziza, big Dave, and now diesel Dave), come up with a new project. I am to the point where I have so many questions it is easier to start a build thread to get some answers (we all like a build thread.)

I found a busted 1993 e-350 long wheel base van with a non turbo 7.3 idi motor for $100 plus a set of inside micrometers I had picked up for <$5 at a garage sale. As I waited for the AAA "free" tow truck to drag it home I could not help but see 2 ips, a full set of injector lines, and a heated filter housing in the sellers scrap metal trailer. He threw them in and away I went.

The ip was gushing fuel out the auto advance plunger so I was able to use the junk ip to fix it. $50 set of glow plugs and a quart of ATF and we were on the road. At this point I noticed the van had $100 worth of diesel in the tank, so I am only into the project $60. How's that for economy?

At this point I take it for a 600 mile round trip to get a base line, 70mph with overdrive auto trans and slipping torque converter, I averaged 20.4mpg using google maps route for the distance.

Years ago I had gotten my gears spinning with Jacob azizas threads about his 30mpg mechanical diesel, he is not super active here any more but on his blog he finally installed a zf5 overdrive transmission and has now broken 38mpg

Diesel Dave is getting around 60mpg with his modern computerized diesel. My van has much more in common with Jacobs mechanical diesel but I have a few advantages. I don't haul the same weight as him, maybe a few hundred pounds of tools and a motorcycle or car engine in need of repair. My gearing is 3.54:1 instead of his 3.73:1. I don't need to climb the cliffs they have in the Bay Area, I live in a land of rolling hills. I found a young transmission tech willing to trade me a zf6 transmission,clutch, pedals etc. for my auto trans and $250. My overdrive ratio is .72 where his zf5 is .75 if my memory is correct.

Finally, the baseline cod for a full size truck is around 0.44 where my vans is 0.37. I am also a diesel mechanic and trained machinist so I will be able to do more complex fabrication than Mr. Aziza perhaps?

All this leads me to the question...can I split the difference between Jacob aziza and diesel Dave's mpg numbers? (38+60)/2=49mpg
A lofty goal no doubt.

A very well educated diesel mechanic at my old job said that diesels tend to get the best fuel economy at peak torque rpm+200. The peak torque for my motor is 1400rpms plus 200= 1600rpms goal cruising engine speed. With my final drive ratio this puts me at exactly 60 mph in overdrive, or 55mph in direct drive. I have heard that direct drive is 5-10% more mechanically efficient so I will be experimenting with both.

Planned mods:
1. Trans adapter made and trans bolted in, need to finish driveshaft adapter and hang clutch pedal
2. Custom tiny primary long headers tuned to my 1600rpm sweet spot, with exhaust tuned to same.
3. Instead of slamming it I may try adding a second fuel tank. In my experiments with my ranger 700lbs or less had no negative effect on my mpg.
4.folding boat tail rear panels like what you see on the semi trucks these days.
5.belly pan
6. Grill block
7. I am a tall man at 6'5" so I think a "raised hood" that goes from the front edge of the hood to a point just below my sight line and just far enough away from window to allow wipers to work.
8.smooth wheel covers.
9. antennae delete
10. rear bumper delete. (I still have 11+ feet of crumple zone behind the driver, I'll be fine.
11.raise rear hitch 10"
12. Led lights all around
13. Lower rolling resistance tires when these wear out.
14. As far as I know the only fuel economy instrumentation available for mechanical diesels are the gps boat ones with flow meter at around $600, I am into the project so little it might be worth it.
15. Up timing, injector pop test/rebuild
16. Power steering delete
17. Convert to electric vacuum pump or manual brakes
18. Side view mirror to camera conversion
19. Tuned intake manifold
20. Less restrictive intake.

That should keep me busy for a while.
Economy is more than fuel so will keep tabs on project costs. So far I am at $360 including the van. Not too shabby.

Would welcome any advice/ideas. Will ad pictures as soon as I figure out how.

[deejaaa]

that was a good and lucky find.

[elhigh]

I think if you crack 49mpg on that thing you just wasted some good luck that might have been better spent on a lottery ticket.

That said, it's already doing better than 20mpg, which when I drove a 15-pass Dodge would have made me giddily happy. I think I only ever beat 15mpg one time.

Subscribed.

[dirtydave]

you need lots of engine off coasting

[bondvagabond]

I have been buying and repairing junk vehicles for 10+ years now so you start to get an idea of what to look for, short version is look for projects that need labor not parts to repair. I do frequently get accused of being lucky :-)

[bondvagabond]

Originally Posted by elhigh

I think if you crack 49mpg on that thing you just wasted some good luck that might have been better spent on a lottery ticket.

That said, it's already doing better than 20mpg, which when I drove a 15-pass Dodge would have made me giddily happy. I think I only ever beat 15mpg one time.

Subscribed.

Dodge never sold a diesel van, and I don't believe you could get the 1 tons with an overdrive trans. So they got crummy mileage. Why they never sold a van with the old 12v cummins is beyond me, they would have sold so many. Your van also didn't have a 6 speed manual or a bunch of the other toys mine will have either, but like I said, a lofty goal. If I can match Aziza's 38mpg I will be tickled pink.

[dirtydave]

I bet you can with 30-45 mph pulse and glide engine off coasting.

[2009Toyotoad]

Originally Posted by elhigh

I think if you crack 49mpg on that thing you just wasted some good luck that might have been better spent on a lottery ticket.

That said, it's already doing better than 20mpg, which when I drove a 15-pass Dodge would have made me giddily happy. I think I only ever beat 15mpg one time.

Subscribed.

I'm not so sure he won't come close to 49 MPG. The non-turbo version of the 7.3 were in a lot of delivery and service vans over the years but they were geared very low for load reasons. I do think, if there were a choice I would have gone with the 5.9 liter with 2 fewer cylinders to feed, and there are / were several bell housing adapters on the market for almost anything you wanted to use as a transmission.

But if he can find the right parts there are a few aftermarket Aux trannies(OD), such as Gear vendors, which will really bring the RPMs down for the flats.
It really comes down to getting units which will match up in terms of splines.

15 MPG on the long wheel base van, surprises me a bit. I'll get that MPG or real close to it on my 02' 8.1 liter gasser dually with a 4.10 rear end and overbuilt Allison 1000 transmission, and that's with 50% more rubber friction surface on the road.

[2009Toyotoad]

Originally Posted by bondvagabond

Dodge never sold a diesel van, and I don't believe you could get the 1 tons with an overdrive trans. So they got crummy mileage. Why they never sold a van with the old 12v cummins is beyond me, they would have sold so many. Your van also didn't have a 6 speed manual or a bunch of the other toys mine will have either, but like I said, a lofty goal. If I can match Aziza's 38mpg I will be tickled pink.

True, but there were several conversion kits sold to switch the 7.3 turbo to the 5.9 . Fortunately, you are starting from a diesel. So if you decide to switch to a 5.9 you don't need to replace the rest of the fuel system. Plus first and second gen 5.9 liter turbo were mechanical, I thought and the only major identified issue was the lift pump design which was corrected by going to the one from the H.O model.

As you probably know and may delete, it was the finicky EGR valve that was quirky on the 7.3 but only an "issue" on the turbo versions.

[slowmover]

I think you've already made your goal. The age of the vehicle calls for new wiring, rubber replacement (from windows to suspension to body bushings), brake lines, etc. The reliability of the van is more to the point. I've owned plenty of old cars and FE is not the primary ownership cost. Especially at that purchase price.

Careful tire choice, axle and wheel bearings plus brake performance and replacing worn out steering would be highest on my list. Vans tend to be run hard and not cared for. "Economy" for most Americans is in doing no maintenance at all.

Can't wait to hear what shape the fuel tank is in (said with the patience of been there and done that). Your other posts indicate familiarity with mech issues, so I'd be more concerned over defining how this van is supposed to pay its way. An impulse buy, or filling a genuine need?