reposted from power and performance


http://www.dieselplace.com/forum/smileys/Star.gif* Ive danced around this issue on the forum and have decided to attack it directly.* What are the <font color="red">BEST</font><font color="black"> and most </font><font color="red">COST EFFECTIVE </font><font color="black">changes or tweaks to a 6.5 turbo diesel K3500 to get the most Miles Per Gallon??</font><font color="black">* Im not rich, so some $6K add on is pointless so don't list those.</font>


<font color="black">Im sure everyone can relate to this right now with the high fuel prices.http://www.dieselplace.com/forum/smileys/Dead.gif* Even more so in Alaska where we had a refinery change ownership and they did a drastic change in fuel prices in just a few weeks.</font>

Lower your gear ratio to 3.73 or 3.42 and run smaller tires.


You can get a used intercooler core from a dodge for $300 and fit it yourself.


Get a louvered tailgate.

QM


If you lower you gear ratio numerically AND run smaller tires, you're defeating the purpose.


Exhaust is always a good choice.


They say 1800 RPM is best for mileage also.

"Get a louvered tailgate."

This myth has been proven false a few times by different studies. The one below was carried out by a university in a very controlled manner. Leave the full tailgate UP for better economy (and less wear on the bed sides). Buy a bed cover if you really want to smooth the airflow out, but you probably won't save the $$ in gas that you spend on the bed cover.

http://popularmechanics.com/automotive/auto_technology/2004/3/04_sae_congress/index5.phtml

I'm not so sure about that.


I have recently installed a 5th wheel vented tailgate and swear that my mileage has gone up 1.


Crew Cab Dually Auto w/4.10's and 235/85's.


I'm now seeing 17mpg.

Billman: That article does say that the one exception is certain pickups with an 8 foot bed. Might be worth checking out if you guys are really interested in emprical data instead of wive's tales. They list out all the data from their studies and even compound it into expected fuel savings.

A lot of times, when someone gets a mod they are expecting to save fuel with, they tend to drive more economically because they are watching their economy. Same goes for HP increase mods - tend to drive harder to enjoy the new super-go-fast power. So, keep that in mind, too.

-Ryan

Billman,


Don't forget that smaller tires would have smaller rotating masses to turn. The smaller the gears the smaller the tires, vice versa is true, as well.


I say louvered but if I made one, I'd use diamond wire and 1 1/4" tube. Real simple and little wind drag.

Ryan - Excellent Point. Couldn't agree with you more.


A lot of that is done here...


QM - I'm still not gettin' it. Taller Thinner Tire is best, I think. What are you saying, less mass, less weight? Edited by: Billman

Proper tire pressure/alignment, Cetane/Lubricity improving fuel additive every tank, exhaust upgrades, clean or high flow air filter, and my favorite mod, dual breathers ;)

Billman,


Ever drive a big 4x4 with 35's or bigger. It takes alot of fuel to get them going and keep them going. Now, I understand that it's all relative to what size you are using or were using but each tire size down will weigh a little less and the rotationg mass (of the tire and wheel) is concentricly tighter as you step down the sizes. The smaller you go, the less resistance in air drag and weight drag.


Plus, you drop the gear ratio( even with a small tire size) the RPM drops and you burn less fuel.Edited by: quantum mechanic

QM what's with the Dodge intercooler?
By the way I have seen wind tunnel studies from Texas Tech that disprove the tailgate down theory on fuel savings. Has a lot to do with push if you're a NASCAR fan you get the picture.

I'd rather have the crap blow out the back than back up toward the cab. My beds are 8'


The dodge intercoolers are plentiful on www.car-parts.com (http://www.car-parts.com) $300-$400. There were a few ford one's but lots of dodge.

I still don't understand what the difference is. Why use a dodge intercooler, are they better than my gm one or what?

GM one? The only GM one is on the duramax, or maybe a bigger truck.


The spearco kit is ~$1250 or more for the 6.5


So $300 for a dodge one is relatively inexpensive.


Dodge turbo is only $200-300 also.

The lowest cost most effective was to increase MPG is to SLOW DOWN!!!! For example at 75 mph I get 19-19.7 MPG at 65 mph I get 21-21.5 MPG. on a 300 mile trip that 10 MPH takes about 37 minutes longer but save about 2 gallons so is 37 minutes worth 2 gallons of fuel more wear and tear on your truck? Rule of thumb every 5 mph you increase cruise speed above your overdrive lockup speed of at 1600 RPM you loose 1 MPG. I have driven serveral times at 55mph and have seen 24 mpg+ you just need to be in the right mood and have the time to spare. http://www.dieselplace.com/forum/smileys/Geek.gif


Mod's Exhaust, air cleaner/intake, &amp; gearing and tires. I changed the gearing and exhaust and figured it took 60,000 miles to pay for it and now I have an additional 80,000+ miles on since break even on those mod's so I'm bucks ahead. If you do mod's that cost bucks you need to feel you will own the truck long enough to make doing them worth while.Edited by: 16gaSxS

Thats true, slower engine speeds, slower fuel consumption, but I like how you high-lighted the SLOW DOWN, and in your sig is says you yourself suffer from Lead Foot Syndrome. Myself, I'll pay the extra 3 bucks to get there a half hour earlier.

Billman,


Don't forget that smaller tires would have smaller rotating masses to turn. The smaller the gears the smaller the tires, vice versa is true, as well.





QM, yeah but smaller tires travel less distance with every revolution. If you go from say 245/75/16 which is OEM on many of our trucks to say 235/85/16 you should have less rolling resistance since you have 10 mm less tire on the pavement and the 245 are 30.5 inchs and the 235 are 31.7 inch which mean you will travel further for every tire revolution. The problem seems to be with the guys who go to like 285/75/16 is that they have more rubber on the road which adds to rolling resistance and they add to the wind drag being wider and taller.

Thats true, slower engine speeds, slower fuel consumption, but I like how you high-lighted the SLOW DOWN, and in your sig is says you yourself suffer from Lead Foot Syndrome. Myself, I'll pay the extra 3 bucks to get there a half hour earlier.


well TDG I drive between 65-75 when going long distance most of the time and I will spend the extra too, It's just a suggestion if someone really wants to save fuel. And there has been times that I'm not in a hurry and I just throw on some tunes and set the cuise and go slower just because. It's not just the slower engine speed it's the need to make less power to over come what we aviation folks call DRAG. Wind drag causes the need for increased power to increase by the square. So if it take 50 hp to make your truck go 50 MPH it takes 200 HP to make it go 100 mph for the drag offset plus what ever increase in the running gear. And you know as well as any of use if you what more HP you have to burn more fuel. This is the reason gearing and tires only do so much it take a certain amount of power to move a truck at a give speed all the gearing and tires do is move the it to a more effiecent place in the power band for the engine. So slowing down moves us closer to that 1800 rpm "sweet spot" that these engines work well at and decrease the need for HP due to wind drag.


For folks that put a bunch of accesories that stick out in the wind you pay for those over and over. First you buy them and install them then you pay for extra fuel for the wind drag as you drive. Edited by: 16gaSxS

I agree completely, wind resistance plays a big role, less speed, less resistance, less fuel consumption. I just couldn't help but comment on what you said and your sig, thought it was kinda funny ;)


Just out of curiosity, what rearend and tire size are you running on yours? Mine's 3.73 with 265/75/16s and 70MPH is exactly 2000RPM on mine, and the computer has been corrected to the new tire size. From about 60 and up I can set the cruise and it will climb any of the small hills around my area no prob, never even kicking out of Lockup. I even find passing power to be very acceptable with out pushing it hard enough to make it kick down.

I agree completely, wind resistance plays a big role, less speed, less resistance, less fuel consumption. I just couldn't help but comment on what you said and your sig, thought it was kinda funny ;)


Just out of curiosity, what rearend and tire size are you running on yours? Mine's 3.73 with 265/75/16s and 70MPH is exactly 2000RPM on mine, and the computer has been corrected to the new tire size. From about 60 and up I can set the cruise and it will climb any of the small hills around my area no prob, never even kicking out of Lockup. I even find passing power to be very acceptable with out pushing it hard enough to make it kick down.





yeah it is funny for many years I only did a few mods gearing and exhaust and now with the extra power I got it I love to use it, it's why I stopped ridding motoercycles 18 years ago.


Anywho 3:42 gears truck came with 3:73 and I running stock size 245/75/16E at 65 I show right at 1800 rpm and even towing it will run up and own hills with out kicking down on most hills on the Instate it's only when I get carried away with real heavy stuff that it has to work real hard like pulling that 1050 gallon water tank.

Running less than 65 is not an option for me. I am delivering the sunday paper to Fairbanks. I am the first to leave the dock in Anchorage and with the stops in Denali I have to push in winter to drop off to delivery drivers before the stores open. Sadly an hours makes a huge difference in paper sales. I would go faster, but the 4:10 gearing and winter conditions keep the max cruise of that truck at 65mph (the actual speed limit).http://dieselplace.com/forum/smileys/Angry.gif


"and my favorite mod, dual breathers " ???what are you refering about by breathers???


Secondly to the gun with all the aerodynamic comment, how does a truck topper affect drag and milage? (good or bad) Secondly how much does is change from a model that is level with the cab roof, and one that swoops up from the cab roof to a higher level? Isnt there some sort of Kham effect or something like that? http://www.dieselplace.com/forum/smileys/HiHi.gif

Get yourself a gasser truck and run it for a while, then your 6.5 will be getting great mileagehttp://www.dieselplace.com/forum/smileys/HiHi.gif

How much does would it cost me to switch my 3.73 limited slip K2500 suburban (4x4) over to 3.43 limited slip? Is it something I can do in my driveway? I'd prefer it for the reduced engine wear in addition to the increased fuel mileage.

They sell gear sets with dial indicators and dvd instructions. Not sure about the IFS but the rear has to have the axles pulled out a little for the ring and pinoin swap. One thing to consider is that taller gears have bigger teeth and when you drop to 3.42 the teeth are thinner and easier to break.


If I was going to pull it apart that much I'd replace the limited slip for a detroit locker or newer Elocker which is a limited slip in passive mode and true locker at the push of a button.

I thought it would be cool to do a 5 or 6 speed conversion on my K2500 Suburban.


Pros:


You could swap out the final gear ratio on the manual trans to hit the sweet spot at your desired cruise speed without having to swap out the axle gears (not sure if you could get a high enough final drive for the 4.11 guys).


Use OEM parts, including trans, clutch pedals, etc...


A manual transmission Suburban!


Cons:


Installation, cost, ROI, Computer, cost, and did I mention cost?

Lotharius;


The better the fit of the topper to the truck the less air flow disturbance. My topper has a poor fit to the roof line and I lost aprox. 1/2 mpg at cruise. From what I understand if you can get one with real close fit then added drag is minor. How much weight are you carring in your box on your paper runs? When your due tires you might consider taller tires then either do a VSSB correction or figure the amount your speedometer is off and jsut figure that in to calculations. Since your buying tires anyway cheap way of lowering effective ratio. How many miles on your 1 Ton and how long do you plan on running it? Also what are your fuel costs per gallon for Diesel? Also in the winter what grade fuels are you running and are aviable?

Running less than 65 is not an option for me. I am delivering the sunday paper to Fairbanks. I am the first to leave the dock in Anchorage and with the stops in Denali I have to push in winter to drop off to delivery drivers before the stores open. Sadly an hours makes a huge difference in paper sales. I would go faster, but the 4:10 gearing and winter conditions keep the max cruise of that truck at 65mph (the actual speed limit).http://dieselplace.com/forum/smileys/Angry.gif


http://www.dieselplace.com/forum/smileys/HiHi.gif





AW YES the ANchorage to Fairbanks run. Been there done that and still missing the Great State of ALASKA. Wishing I was there. You could drop you rear end gear to 3.42's or bump your tire size up a couple sizes would do the same thing.