High MPG work truck

[oil pan 4]

I blew a fuel injector return line on the drive home from work, dropped fuel milage for the last tank to just under 15mpg.
I figured I should throw that one out.

I installed a new thermostat, comes up to temp fast and runs a little hotter than what I would like to see.

[ECONORAM]

Originally Posted by oil pan 4

To be fair this time last year I was trying hard to get 16.4mpg in the bitter cold, new tires and thin air here.
I was doing things like running a 50% or more grill block and using my two 650watt block heaters whenever possible.
So far with out trying I am getting near 19 on the day to day drive with the turbo and I am driving 5 to 10 mph faster now that I have more power in over drive to overcome the cross winds.

That is pretty good!

I recall my 81 Rabbit had a cap missing off of one injector return line when I bought it. Actually, the salesman had put a piece of vacuum tube on it, which didn't work. Bought a new cap and gained 4 mpg immediately!

[oil pan 4]

Changed oil from rotella 10w-30 blend to old SL rated synthetic 5w-40 with the good oil filter.

[oil pan 4]

Adding a second turbocharger and intercooler has helped fuel milage.
In an unfair test that favored the single turbo setup it was beat by the twins and intercooler setup by about 1/2 MPG.

The single turbo setup had a cold air intake, where the twin setup was drawing hot under hood air. (diesels like cool air)
Also the cross winds were far worse during the twin turbo setup test.

[virtip]

Heya there, just saw your build from a google search and decided I ought to drop my 2 cents.

A year ago, I had a 1991 Dodge single cab 150 4x4 Pickemup with a 360CI TBI v8, NP435 Manual tranny (no O/D), a 3.56 axle ratio, and a curb weight of 5,600 lbs.

now it was by no means a dedicated mileage rig. we actually purchased the thing to haul hay! which it did magnificently.

before I knew it, the Dodge was my daily driver (don't ask). and I decided to see what mileage was possible out of a dinosaur.

I got 18 average miles to the gallon. blew my mind! now granted, my route is about 75 highway miles round trip, and I never broke 60mph (more from lack of O/D than anything else).

Moral of the story is, if I can get that out of a steel brick with a gas siphon and no overdrive, you probably have room for improvement from a hypermiling diesel Suburban.

-Tanner

[oil pan 4]

I had no problem getting mid to low 20mpg with the N/A diesel engine when I lived on the east coast. Thin air and cross winds that blow almost every single day out of the north or south from lunch time till almost sun down are killing MPGs.
The few and far between cross wind free tests I get show a 2 to 3 MPG improvement.

This is what it looks like so far:
Question: Turbo charging a turbocharger - Page 12 - Diesel Place : Chevrolet and GMC Diesel Truck Forums

[oil pan 4]

I just finished a drive on a different rought with the car.
Last time I drove this rought was at night with absolutly no wind, the lincoln town car was putting up a legendary 26.2MPG at 65mph on the instant MPG read out.
Now the same drive with 30mph+ head/cross wind gave me a 22.6 MPG reading.
These strong sustained eastern NM - western TX cross winds kill fuel milage.
This big car has no problem getting around 25mpg on the open road as long as you keep it under 70 and don't have any winds.

[mikeyjd]

Good read. I wish I had your know-how to put into my truck.

[oil pan 4]

Originally Posted by mikeyjd

Good read. I wish I had your know-how to put into my truck.

The cummins forums are alive with swaps, compounding and intercooling non intercooled trucks, more so than the 6.5L guys.
I think the 91 cummins has an H1C turbo, its kind of a small by todays standards.
The H1C uses a T3 exhaust manifold flange and has a 3 inch down pipe, I believe that even tho the turbos changed over the years cummins stuck with Holsets that used the T3 manifold and 3'' down pipe for many years.
The oil hookups on the Holsets have changed very little if any from 1989 through today.
They used the T3 flange till 2007.

As long as the turbo bolts to the maifold, every thing else is easy.

[oil pan 4]

After almost 2 years the suburban has ram air again.
Also replaced the air filter, Its been on there for more than a year and I didn't realize how dirty it was until I pulled it off and had dirt dumping out of the air cleaner where it wasn't sealed up.