Fuel Economy Solutions

[AKaiser]

Found this out there, I forget where. The link that took me to this might have originally come from here, but here it is again. Very insightful. One thing I noticed: according to the source, the 5. 9 should get it's best fuel economy somewhere around 1525 RPM, and based on the calculations there, I figure the 6. 7 should get the best economy at 1475 RPM.



updated FAQ on Ram MPG improvement (long)

 

[AKaiser]

Duct Tape over Grille

One of the things they did in the fuel economy test was to cover the grille up. There's a huge amount of unnecessary air flow going thru the massive grille on 2003 and up trucks.



I went to Menards and found some black duct tape, and pretty much covered up the grille entirely. It looks pretty good on my truck and there is no overheating problem as far as an empty stock truck plus Smarty SW1 goes. There are two air entry points: below the grille and the gap in the bumper, so there's plenty of cooling and charge air for the engine. Will keep informed on my results. Tape cost was less than $4. 00.

 

[PPettit]

Keep an eye on your EGT's while you are trying this. I thought about trying this but I'm a bit worried about air flow thru the intercooler. Now that the weather is cooling off some it probably is not a problem.

For all the guys who may try this on a 2nd gen truck, make sure your radiator is clean! Several other threads on here have documented how plugged up they can get.

For some interesting reading check out GasSavers.org - Helping You Save at the Pump



Phil

 

[AKaiser]

Radiator coolant temp never hits 200 F cruising 70-75 MPH on interstate. Not under any load except truck itself, empty.



Besides, why would airflow thru the intercooler be an issue unless there was a complete sealing off of the engine compartment or an extreme negative pressure that the compressor couldn't keep up with? The compressor draws air from the air filter box, pushes it thru the IC, then into the intake manifold. If that was a problem, wouldn't you notice a power loss?

 

[AKaiser]

For all the guys who may try this on a 2nd gen truck, make sure your radiator is clean! Several other threads on here have documented how plugged up they can get.

I can't see needing to do this on a 2G, since there's about 2/3 or less frontal area in the grill and quite a bit better aerodynamics than a 3G.

 

[AKaiser]

First FE report with duct tape, mostly backroads, is 21 MPG and it does stay a bit warmer. Too early to tell what effect, if any on FE. 21 is close to my mixed driving average.

 

[gathomas]

Blocking Grille for Fuel Mileage

After reading an article in another publication about a fellow in Calif. that taped cardboard accross the whole grille, result--30 MPG +. His truck: 97 Ram 3500 CTD

I have identical truck, so I decided to experiment.

I used black foam board 1/4" thick. I blocked off about 80% of the grille.

Results,--I went from 20 mpg to 24. 4 mpg that was in the heat of summer.



Sometime in October, I'm going to total "Block out" the grille, including the two lower slots where the fog lights are. I'm shooting for 30 MPG!! Oo.

 

[PPettit]

Radiator coolant temp never hits 200 F cruising 70-75 MPH on interstate. Not under any load except truck itself, empty.



Is 200* normal on a 3G? on my '01 I rarely run over 180 even in 100* weather with no load.



Besides, why would airflow thru the intercooler be an issue unless there was a complete sealing off of the engine compartment or an extreme negative pressure that the compressor couldn't keep up with? The compressor draws air from the air filter box, pushes it thru the IC, then into the intake manifold. If that was a problem, wouldn't you notice a power loss?

I am refering to the air flow across the intercooler, not the compressed air that flows thru it. Does that make sense?

Personally I don't think you will have any problems but it is better to approach these things with caution. I have tried blocking the grill on my VW Passat and saw a minor improvement in MPG but pulled the tape after seeing coolant temps rise. I suspect it is a wee bit more aero to begin with.....

 

[PPettit]

I can't see needing to do this on a 2G, since there's about 2/3 or less frontal area in the grill and quite a bit better aerodynamics than a 3G.

Hey, if it improves MPG and has no negative side effects why not!

 

[PPettit]

First FE report with duct tape, mostly backroads, is 21 MPG and it does stay a bit warmer. Too early to tell what effect, if any on FE. 21 is close to my mixed driving average.

Keep us posted. I love this stuff!



Phil

 

[JCotte]

This will be interesting if it works. Then we can tell the dealer the issue is with DC and not Cummins

 

[AKaiser]

Drove from Indy to Grand Haven, MI, IN-29 to US 31, and back to South Bend, down US 31 to US 30 E to Warsaw, IN, got 22 1/4 MPG, hand calc'd. Average speed, I'm guessing 63 MPH. Some stop-and-go/slow down-speed up, but mostly just cruise. Never exceeded 200 deg F on the coolant gauge.

 

[steved]

Could it be that the additional "heat" is making things run better? Mine seems to run better and get better mileage the "warmer" it runs. I get my best mileage when temps are well over 100*F.

steved

 

[AKaiser]

Could it be that the additional "heat" is making things run better? Mine seems to run better and get better mileage the "warmer" it runs. I get my best mileage when temps are well over 100*F.



steved

From what I've read, 200 degrees is pretty close to the optimum engine temperature for fuel economy. New Chrysler gas engines have a dual thermostat system-one for the head and one for the block. They keep the head temp lower to prevent knock, and keep the block higher to increase efficiency, or so I've read.

 

[ThrottleJockey]

I wouldn't mind trying a 203 or 210 degree thermostat in my engine, it has lower compression pistons in it, runs very cold as opposed to stock. Both EGT and coolant.

 

[brods]

Hey, if it improves MPG and has no negative side effects why not!

That is the ultimate question. If it was that simple and there were no negative effects, then why wouldn't the mfgs just do it??? There has got to be a trade-off somewhere!!

Engine Operating Temperature (Coolant and Lube Oil)



Low coolant temperatures indicate an engine that is too cold for efficient combustion. Fuel liquefies on the cold cylinder walls and fails to burn. Of course, excess heat causes engine failure.

Lube oil below the ideal temperature is more viscous and harder to pump. Oil above the ideal temperature is too thin to lubricate properly. Either way, the engine suffers.



Coolant and lube oil operating temperatures can contribute greatly to fuel efficiency. Typical cooling system operating temperatures are above 180̊ F. A 0. 4% fuel economy loss is associated with every 30̊ decrease in temperature.



Lube system operating temperatures run above 225̊ F, and a 1% fuel economy loss is associated with every 30̊ decrease in lube temperature.

Of course they do not say what the safe maximum temps are! http://www.everytime.cummins.com/every/pdf/MPG_Secrets_Whitepaper.pdf

The other concern with blocking off the radiator is that all the other coolers are there, power steering/brake booster cooler, transmission cooler, ac condenser, intercooler, etc.







As for the best mpg rpm, maybe in theory 1525 is best, but I'd bet the ECM programming has a great influence on max mpg. Cummins recommends around 2000 rpm for the ISB.

For maximum fuel economy or for vehicles operating 65 mph or faster, select a gearing combination that will result in an engine speed of approximately 2150 rpm at 65 mph checkpoint.



Gearing combinations that produce an engine speed less than 1900 rpm at the vehicle’’s intended cruise speed (mph) should be avoided.

It will be interesting to see what results the guys that swapped to 3. 42 gears get. That thread has had very little feedback on mpg changes.

 

[DPellegrin]

I 'm with PPettit on this one. I think you need to be very careful about blocking air flow across the intercooler. It's probably not an issue when the engine is operating at less that full power or peak torque. I'm thinking that Cummins/DC sized that intercooler just like they did the radiator i. e. for acceptable engine operation at worst case conditions-max power and high ambient temps. However, I am reminded of Cummins, DDC, Volvo, Mack prohibitions and recommendations for winter fronts on class 8 trucks. Prior to the widespread use of air-to-air intercoolers truck operators would completely block the radiators and many trucks ran thermostatically controlled "shutters". With the advent of air-to-air intercooling "winter fronts" now provide some airflow across the intercooler, albeit reduced. Should the engine be asked to provide full power or be lugged down to peak torque, turbo compressor out air temps can get pretty high necessitating some heat removal by the intercooler.



There is a way to test the effectiveness of aerodynamic modifications. It is called "road load coast down" and is basically the application of Newton's second law of motion. that says Force= mass times acceleration (F=MA). After preconditioning your vehicle find a fairly flat road, using a stop watch time the number of seconds it takes to coast down from say 40mph to 30mph, do this in both directions several times and take the average of the test runs. Then make whatever modification you are testing and do the same coast down. If the time is greater in the test condition then the modification has some merit and will provide improved aerodynamic drag characterisics of the vehicle and therefore better fuel economy.



Regards,

 

[PPettit]

I think I have tracked enough tanks of fuel to say beyond a shadow of a doubt that running RPM's at 2150 on an unloaded truck will kill your mileage. Yes the best BSFC (brake specific fuel consumption) for a 24V motor is at that RPM. That means that the engine makes the most torque for the least fuel. Good for a heavily loaded engine, not really so for a lightly loaded engine.



DPellegrin, Hows that MN winter weather treating you? I grew up in that part of the world but it's been a long time ago... .



Phil



"Originally Posted by CumminsPowerSpec

For maximum fuel economy or for vehicles operating 65 mph or faster, select a gearing combination that will result in an engine speed of approximately 2150 rpm at 65 mph checkpoint.



Gearing combinations that produce an engine speed less than 1900 rpm at the vehicle''s intended cruise speed (mph) should be avoided. "

 

[DodgeWarlock]

Tried covering the grille and folding mirrors on our 01 after reading a mag article. Two weekends(1st uncovered,2nd covered)in a row drove the same 200 miles of road with negligable weather differences. Used cruise control when possible and did not exceed 2000rpm if at all possible. Ran 60mph most of the way. Saw an increase of 3. 5 mpg versus the first weekend.



Tried same test on wife's commute to work(60 miles a day) over two weeks. Same parameters except max speed of 45mph and left mirrors out. Saw no increase in fuel economy. We knew the aero would affect more at higher speed but on a 2nd gen it only seems to make a difference at hwy speeds.



Saw an increase of maybe 5 degrees in coolant temp. Would spike an extra 5 when climbing long hills. Did not tow at any time during test due to lack of transmission temp gauge.