After a long trip, good news.

[ogrice]

I've recently completed a round trip from Seattle to Los Angeles. Each way i had 1000# of cargo in the bed and a 4000# car in tow. My normal mileage is between 15-16 mpg thru mountains and 17-18 on the flat going 60-65 mph the whole distance.
This trip I got 16.7 mpg thru the mountains and 19.1 on the flat going 65-70 with the same load in tow.
How did I achieve those gains.? Well, before I left I did a drive train tune up. I replaced my U joints, U bolt straps, and adjusted the center alignment on my drive shaft.
The bottom line about this post is to give everyone here a small reminder. If you have a vibration that only appears at a certain speed that can only be felt at your seat or can be heard or if you have been neglecting to check those driveline parts but want to get some more miles per tank, then keep reading.
First, I dropped the drive shaft and changed out all of the u joints. You are probably going to find out that over time your u joints and u joint straps get out of round. This out of round causes a slight imbalance in the drive shaft which takes away a small portion of the torque and turns it into a useless driveline vibration. It happens over a long time. I mean over the course of 50K-70K miles depending on the condition of your rig. After changing the u joints to heavy duty Spicer u jonts, I checked the lateral alignment of the drive shaft by comparing its straightness to a rope held tight from the yoke of the output shaft to the yoke of the differential. For those with two piece driveshafts, this alignment is very important for torque transfer to the wheels. I found out that mine was about 1/2" off from being straight.
After making the drive shaft alignment straight and changing all the u joints, i've found that I have regained some lost torque and a lot of vibration and noise that I have come to tolerate as normal are now gone. My work was good enought to yield a full mpg while towing.
For those readers and subscribers who have hung onto there rigs long enough to change out engines or transmissions or are going to hold onto them that long, please pay attention.
After doing this to your rig, you may be very surprised with the results.

[Barry Nave]

*og%rice*
Is this something your burning in the fuel? being this is your Sig ;)

[ogrice]

Nope.
Its been my email name for the last 6 years. Just keeping my profile here the same as everywhere else.

[Barry Nave]

:cool: ;)

[roclongrider]

Interesting information that I have never even considered. A project for this weekend for sure.
Thanks!!!

[moondoggie]

Good Day!

My pickup gets this mpg (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=004439#000014) (click in colored text). As it says in this link, in the 2000 - 2002 summers, I pulled a US Cargo SM625TA2 trailer (looks like the US Cargo SM727TA2 (http://www.uscargo.com/uscargo/products/enclosed/snowmate.asp) [click in colored text] except it's 25' long instead of 27') with a junior dragster & golf cart in it

[ogrice]

Just filled up my gas tank and the 19.1 mpg on the flat was in correct. I got 18.7 mpg. That is still .7-1 mpg more than the last towing trip for the same distance on my rig. I hope that the info that I post here helps get some more mileage out of each tank of fuel for those of you out there too.
For those who are stuck at a plateau for mileage, I'll briefly describe my rig so that others can compare.
93' std. cab dually, 5 spd trans.
18.7:1 CR. (got the pistons machined down)
fully balanced rotating assembly.
stock turbo w/ turbo master wastegate set @ 10#
phaser timing gears and new db2 4911 not turned up.
BD down pipe & 4" exhaust, K&N open element
dual electric fans, underdrive pulley.
6.2/6.5 NA diesel intake manifold w/ banks sidewinder upper intake plenum. (had to custom fabricate the turbo outlet pipe)

As a side note, my VW TDI Jetta got 50 mpg going north from Los Angeles to Seattle. 622 miles on 12.4 gallons of fuel.

The 240z blew up its u joints while my friend was driving. It cost him 100+ dollars to get it towed to my house. Otherwise, it would cost me a small fortune to get it out of the impound after a few days.

[ogrice]

to moondoggie

My rig is not the code c6p heavy duty truck like yours. I've got 3.73 rear gears and you have 4.10's. It's not really fair to you to try comparing mileage. I do not know how your rig holds up to other ones w/ 4.10's. From your mileage sheet I can definitely say that your rig holds its own. The most weight that i've towed is around 6600#. A lot of people, like yourself, have probably towed twice as much as me on numerous occasions.

To what I attribute the gas mileage that I get.....I think the setup that I have has had efficiency as its theme. I went out of my way to research things like lighter rotational mass, windage drag, diesel engine harmonics.
Hence my use of single mass flywheel, electric fans, underdrive pulleys, engine balancing, poly urethane engine mounts and suspension bushings, KYB shocks and struts.
I'm very fortunate to have this tight of a setup which gives me very good mileage.

[moondoggie]

Good Day!

I am extremely grateful for your reply. It

[ogrice]

I can explain the underdrive pulleys part. My truck has AC, no vacuum pump. I used a Ford racing billet aluminum main pulley. The spacing is aprrox. 1/10"-1/8" taller than the stock pulley, same bolt pattern. The belt deflection is negligible. I went w/ a 2.4m long belt to compensate for the shorter length. The total under drive for all the accessories is big. I mean at least 30% and maybe more. I'm in the process of changing my tach driver to the isspro unit for the 6.2 diesel because at 85 mph needle buried the tach reads only 2100 rpm and I understand that at 85mph it should read 2800-3000 rpm.
I have not noticed any negative effects on cooling and driving highway 95% of the time there are no effects to the charging system, even with towing. I did this because of all the testimonials I read how under driving the accessories will free up some hp/torq on the engine. The water pump and alternator make rated flow and amps at around 1500-1600 rpm h2o pump and 1200-1300 rpm for the alternator. Not to mention that the AC compressor doesn't need to spin any higher than at idle or 700rpm with the AC on. Winding the accessories too high is actually very wasteful.
As for where I got my information. It says it most of the time right in the instructions that it comes with. Not what it says on the advertisments, because if the product doesn't perform as the manafacturer says it should on its own installation instructions, then I can cash in on a warranty.
If what you do is 75% highway driving and don't mind opening up the dash to redo the tach driver, then you can benefit from underdrive accessories.
To be truthful, I stumbled onto the parts. I was asking about underdrive pulleys at the local speed shop and the guy behind the counter said that a Ford racing pulley will fit. I just happened to have the parts sitting in a box collecting dust.

[moondoggie]

Good Day!

Again, many thanks. Underdriving accessories as you've done makes perfect sense. It wouldn't work for lots of folks for reasons you already understand, but for folks like me it would work fine.

I sure wish a guy had time to pursue his ideas. I always thought a variable drive for at least the A/C would make sense. In other words, keep A/C compressor rpm constant regardless of engine rpm. That sucker's gotta waste LOTS of power most of the time, just so it can provide some A/C at idle and/or low rpm. Oh, well... :(

I think when mfg's switch to 42V you'll see brushless DC motor-driven chassis-mounted A/C compressors. This would allow maximizing the A/C compressor's efficiency, as it would always turn the same rpm. They'd also be less leak-prone - a few hose connections could be made semi-permanent.

on edit: I just re-read some of this stuff. I'll bet removing your engine-driven fan helped a lot too. With the fact that I rarely pull now, that's something I could for sure do, as long as I kept my eye on things. Hmmmm... :eek:

Blessings!

Brian Johnson, # 5044

[ogrice]

To Moondoggie:

I'm going to be installing propane inj., H20 inj., and crankcase evac all in one shot before summer hits. Just purchased a gm-8 core and I'm going to have the exh housing and impeller modified during the rebuild. After the whole setup is in place, I'll post my findings after the next road trip.

[moondoggie]

Good Day!

This ain't a bad deal. You spend all the money & bust your knuckles, we get all the advantage. :D Sure wish I could pursue some of this stuff... :(

Blessings!

Brian Johnson, # 5044