Best tips for gas mileage???

["Mad Max"]

So here's a question: What are the best ways to BOMB our rigs that will produce noticable benefits in mileage (almost always resulting in some increase on power)?



What mods have y'all made that you've noticed appreciable gains in mileage, even if whole 'package' mods, what are they and what were the costs, pros and cons, etc etc???



- S

 

[JLEONARD]

S,

Mileage is directly proportional to the weight of your right foot!

Let me answer this way... . in a way that I learned and use in the diesel boating applications.

A diesel is very precise in metering fuel. Fuel consumption is really based on actual horespower used, or horsepower in use. This is important in boating because since the engine is always working, you need to be at an efficient speed for the boat/engine/gear ratio combination.

And a general rule of thumb (backed up by manufacturer's data) is that fuel usage will be less at a given horsepower level for a higher rated engine than for a lower rated engine.

So in truck terms, generally the more hp your engine is BOMBed to, the better mileage you will get when you are cruising with a light foot.

So if you blow the doors off every PJ and DP and Hemi you end up next to on the boulevard and the interstae, your mileage is gonna pretty much suck.

(But the satisfaction factor will be huge

)



That's my take anyway. It was time to stir the pot.

Jay

 

[dpuckett]

I agree with JLEONARD to a point. The general consensus I have found here in the forums and through personal experience is that anything to lower EGT will help MPGs. Smaller housing, injectors that atomize better (PWs come to mind, though no personal experience), and timing. I bumped the timing up on my mom's truck the other day, and am already 50 miles "ahead" of where the guage "should" be for 1/2 tank. I moved the pump flange maybe 1/16 inch more to get a thin 1/8 inch between the factory marks. Gearing makes a difference in most vehicles, though the current truck I have (see sig) gets the 2nd best avg mpg of the 6 I've owned, bested only by a stock D250 w/ 3. 55. Age and pop pressure of the injectors will make a difference- once again, atomization and timing. Get a pyrometer (in the manifold) and boost guage, and then try to keep the numbers down while at cruise. You can drop 200* sometimes if you drop 3 mph, especially in a headwind. There is no reason why these pickups cant top 20 mpg on the highway, even in winter. I've had some "bad" combinations for mileage, and failed to average 20 or better in one- 93 W350 Xcab, flatbed, 4. 10, 5 speed with stock injectors and turbo. Got 18. 5 going 60-65.



THat novel's worth said, I think the best place to start would be timing, and a smaller turbine housing.

 

[KBalzuweit]

All I can say is I just turned up the pump and have no other mods and my cruise empty at 70mph fuel economy went up about an average of 3mpg.

 

[cerberusiam]

Air in and air out. Those are 2 of the cheapest modifications to increase power and mileage I have found.



The stock exhaust system was a joke. It was manufactured with intent to reduce the amount of HP and torque the engine could make with no other mods.



The air intake system was a little better but still limited the quality and quantity of charge air. A bigger element and a better source of fresh air makes a difference. A higher flowing aftercooler can also make a big difference. Air quality again.



Aerodynamics. Unfortuately there is only so much you can do with a box car to make it cut the air, but, a shell or bed cover will help. An air gate instead of an air dam at the back of the box. Cheap way is to take the tail gate off. That made as much as 1 mpg difference.



Lock-up TC with better torque multiplication. I will get booed for that but hey, its in all the newer ones for a reason. Lowering the rpms will lower fuel consumption all other things being equal. The 5 speeds already have that advantage so no help there. This is not a cheap mod and definitely not for the faint of heart.



Upgrading the compressor side of the turbo. The hot side is probably not as important for mileage and will reduce the EGT's when towing. The smaller ones are much more fun to drive but that leads to the heavy right foot affliction which kinda defeats the purpose of mileage.

 

[Bob Beauchaine]

After I installed my DD3+'s I isolated 602 miles on my aux. tank to see what my mileage would be with 300hp injectors - 22. 16mpg and 21. 11 for the first fill-up of both tanks. Thats about 2 mpg better than with the PW injectors. I feel that my truck breaths very well and that I have acheived a fair balance of air in exhaust out.



I do have to agree with Jay - It's all in how you apply the available power. I usually cruise at 70 mph with the cruise control on and only use my power in town when necessary.



Bob

 

[BushWakr - RIP]

Absolutely... . air in/air out... . a good start. .

A well tuned and timed injection pump

A set of larger injectors (with in reason for mileage purposes)

Alot more attention to using gears/RPM properly

Hybrid/modified turbo charger... . smaller exhaust housings really do basically one thing well, they improve spool times. The do other things poorly, such as high drive pressures, higher EGT's at the mid/top end, can be overspooled and other things as well

The compressor end can be a real help if the hybrid is configured properly. Look at some of the big HP guys who run singles for evidence of that.

You need the turbo combo that will supply as much boost as needed (only), at a preferred temperature. If you run the turbo outside it's map range you get boost at blast furnace temps.

I believe that Dodge went to a lock-up TC system for a couple reasons... one, the 1st gen transmission's (auto's) all run hotter than the 2nd gens... . and that is one reason why DC went to the lock-up system... HEAT. Second they, like other makers, were in a HP race to some extent and they knew that it would require other methods of power transfer to hold on to that extra HP.

Proof??... look at how our 727/A518 would handle 300 RWHP and for how long. With even some modest mods, we can drive the A518 into the 270*F range, that's why there is a temp sensor to lockout OD at that range on a stock truck.

When in lock-up, torque mulitiplication is not in the equation, it's lock-up. If I'd had the extra $$$ I would have gone lock-up though, no question.



Lets be honest, speaking personally here, but if we want hotrod performance we run the ragged edge and pray to the Acceleration Gods that it holds. If I/we want to strike a balance between hotrod and daily, working HP we may go easy on some of the things we do to these great 'ole gals.



There are some mods that can be made to really improve the performance and still be configured correctly to max out daily mileage and still provide riceburner stomping power/smoke when needed.

I personally took one of nascar's mods, and in conjuction with another one of my own, made a nice improvement in my mileage.



On my last dyno run I had some nasty temps and 284 RWHP. That run did not include some mods that you wouldn't normally run as a daily driver so I left them out. BUT at that time my RWHP had gone from 225 RWHP I think it was, to 284. I actually improved my mileage from about 16. 8'ish to a full 18 mpg as it sits now.



Well that's it. No flames intended here guys, just some time spent behind the wrenches, under the hood and listening to the real guru's who have been there and actually done that. .



Bob.