Gas Efficiency
#5
08-28-2005 | 11:06 PM
Champion
Joined: Aug 2005
Posts: 3,313
Likes: 8
RE: Gas Efficiency
This was written for second gen Rams
and has been modified but needs
to be re-written for 3rd gen Rams
but the basic principles apply.
With the dual sparkplugs and deep-in-block knock sensors the 5.7 might really
benefit from a special design piston that raises compression ratio and shifts
the combustion space over toward the exhaust side.
Aerodynamics is even more important on 3rd gen Rams to improve highway mpg
because they have gotten taller, wider (increases frontal area) and blunter
(worse in engineering term called Cd or 'coefficient of drag').
Those with Cummins engines may first want to read the 'White Paper'
from Cummins called:
"Secrets of Better Fuel Economy: The Physics of MPG"
which is oriented toward 18 wheel trucks but 90% applies to Ram pickups too.
http://www.cummins.com/na/pdf/en/pro..._Whitepape.pdf
beginning of original post:
Ram Pickup MPG improvement discussion :
{last modified 08-02-05}
Many Ram pickup owners start trying to improve MPG by first trying engine
modifications. Unfortunately, the efficiency of most modern engines is
already highly developed after 100 years of improvements, and this is the
toughest place to start, and many Ram owners make bad choices and waste money
that could have simply been spent on more gasoline.
The cheapest and most cost effective mods are usually aerodynamic improvements
that help high speed highway MPG, because a factory stock Ram has the Cd of a
brick, perhaps because many buyers value a big grille over a slick shape.
Second easiest MPG improvement comes when it is time to buy new rubber, where
good choices about the rolling resistance of tires will improve both City and
Highway MPG. Unfortunately finding information about what engineers call Crr
of a tire requires a good deal of looking and most tire makers actually hide
this information.
Next, there are drivetrain mods that will allow your engine to operate at 2/3
throttle and the best piston speed. This is where it turns fuel into
horsepower most efficiently even without internal engine part changes. Yes, I
said 'piston speed' and not a 'magic' rpm range called 'The Powerband'
Last, for the most work and the most money, there are mods to the engine
itself that will improve fuel efficiency when the throttle is only partially
open, but be prepared to give up some of the engine stuff you read in the past
in old hot rod magazines that was based on engines operating at full throttle
and meant for producing maximum horsepower.
This is a long article that is divided into three main sections: aero mods,
tire mods, and engine&drivetrain mods. At the end are weblinks to much
additional information. Feel free to skip to anything that suits your fancy.
AERODYNAMIC MODS
As others have said, a hard tonneau can lower the aerodynamic drag. I
installed a ARE hard tonneau and found it was good for about 1 mpg
improvement. Ford says that a soft tonneau is good for +1 mpg on the F150 and
tried to get the EPA to allow them to add this to their highway MPG result by
re-classifying the tonneau 'standard equipment.'
This Fibernetics hard tonneau has a 'Roofline Extention Spoiler' on the back
that might help MPG a bit more than a conventional design. Here's a view of
the rear spoiler, but on a F150:
There is an interesting student project on a aero improvements tried on a
Dodge Ram model truck several posts down at this link:
http://www.dodgetrucks.org/forums/viewtopic.php?t=52115
If there are astericks in the above weblink, replace them with the letters
d-o-d-g-e-t-r-u-c-k-s.-o-r-g without any dashes, or go directly to the stored
old pages here:
http://web.archive.org/web/200304141...affner/did.htm
and
http://web.archive.org/web/200304142...er/Tonneau.htm
Note that the students found that camper tops and removed tailgates hurt, but
tonneaus and lowered tailgates helped slightly.
It is possible that a 2inch front/4 inch rear drop on a Ram suspension could
improve the aerodynamic drag. There is some evidence that on a 1996 Indy Ram
this improved the Cd by a few hundreds.
The 3rd gen body on the SRT10 Ram uses a 4/6 inch lowered stance, a rear wing,
tonneau, and perhaps partially block off of the 'too big' radiator grille to
lower its aerodynamic Cd from the 0.50 of the stock 2500 Ram to the SRT10's
value of 0.45
Bug shields at the front of Rams nearly always hurt MPG.
The Dodge Ram Diesel that set the Bonneville speed record had 'Mooneye' wheel
cover discs. These are supposed to reduce aero drag by 1-2% but hurt brake
cooling. I also notice this Ram had mirrors and wipers removed.
A MPG test over a roundtrip of a section of I40 at a steady 70 mph showed
0.7 MPG worse without the Ram's stock front bumper air dam, than with the
stock air dam in place. Other 2500/3500 Diesel Ram owners have reported
better MPG after taking off their air dam on the TDR website - but those tests
did not seem to be carefully done.
I have recently had some aerodynamic success with home-made little aluminum
tabs called 'Wheeler Vortex Generators'. I mounted 5 just behind the side cab
windows, and another 5 just in front of the rear brake lights. These improved
my coasting speed down a 6% grade hill by 2 mph, and also improved MPG at a
steady 70 mph by 1 mpg.
I had previously tried this product on the roof of the truck, but it did not
work:
The vortex generators I made were cut from 5 inch by 7 inch aluminum
'flashing' from Home Depot. You cut the flashing into 3 and 9/16th inch
circles, and then bend the sides up to form the 'wings'. A circle of course
has 360 degrees. The front of the wings take up 107 degrees of the circle,
and the back takes up 22 degrees. The finished product looks like this:
but without the magnet backing. I used 3M 'Super Strong' outdoor mounting
tape from Target to stick the vortex generators to the truck's sheet metal.
I am still testing with the Wheeler Vortex generators. I have tried bending
dimes into tiny ones for the mirrors - but no measureable change. I have also
tried little 1.5 inch ones on the bottom of the Ram airdam - felt more stable
but MPG tests showed worse results. The best results have been on the sides of
the cab and on the sides of the pickup bed ahead of the tail lights. This
inexpensive mod can be good for better MPG especially at higher speeds.
There is also a commercial vortex generator called 'Airtabs' made of various
plastics and perhaps a bit lower in drag than a home made Wheeler type. These
are $3 each.
TIRE MODS
Increasing the air pressure in your tires, and picking a narrow 'rib tread'
commercial delivery truck type tire that has low rolling resistance
definitely helps MPG. Raising the air pressure by 15 psi to the max 70 psi in
Goodyear Wrangler HT 235/85R16E tires increased my mpg by +1 in a 311 mile
test run - but the ride was bone jarring. A narrow, highway rib tire like the
HT gives the lowest rolling resistance. Wide, aggressive tread tires can be
three times harder to roll. It might pay to have a 4 tire set for the weekday
commute, and a weekend mudder wide tire set.
Consumers Reports is the only organization I know of that tests for rolling
resistance of tires.
Quote from CR:
" Fuel mileage at a price. Some tires roll with less drag than others. The
lower a tire's rolling resistance, the more fuel you can save. Those savings
can be significant. {Pickup and SUV} Tires with the lowest rolling resistance
delivered nearly 2 mpg more at a steady 65 mph in our highway tests {2003
four-wheel-drive Ford Explorer XLT 4x4} than those with the highest rolling
resistance. The catch: While some high-scoring tires had low rolling
resistance, most tires with the lowest rolling resistance also had lower
overall scores."
In their 11/2004 Pickup & SUV tire test CR the
lowest rolling resistance tires rated 'excellent' were the:
Bridgestone Dueler H/T (D684)
Michelin Cross Terrain
Continental ContiTrac
BF Goodrich Radial Long Trail T/A
The Pickup & SUV tires with the worst rolling resistance were the:
Pirelli Scorpion STA
Kelly Safari Signature
Yokohama Geolander H/T-SG051
A tire with a 'very good' rolling resistance and high scores in other handling
and braking tests was the Hankook DynaPro AS RH03
The California Air Resources board is pressing the tire companies to make
rolling resistance measurements on tires freely available to the public by
2008, one of the few worth while things CARB has ever done in my opinion
The lower profile 17 and 20 inch tire designs used on the 2003-2005
5.7Hemi Rams have a 'sticker' tire tread and higher rolling resistance than
earlier year Rams. It is probable that if a manufacturer makes available a
235 85 R17 tire in Load
Range E it would be lower rolling resistance than the stock tires and might
improve MPG by 1-2 at 70 mph.
The 2006 Ram press release says the new model will have 'low rolling
resistance tires.'
ENGINE, LUBRICANT, EXHAUST & DRIVETRAIN MODS
Switching to synthetic lubricants - - engine oil, diff, Amsoil C+ Mopar-spec
transmission fluid, and syn greases in wheel bearings is good for 2-5% MPG
improvement. That is only about 0.5 mpg but every little bit helps.
Larry Shepard writes in the 'Magnum Engines' book published by Mopar Perf that
running engine oil and transmission ATF levels 1-0.5 quarts below the 'add'
marks on the dipsticks can increase MPG slightly due to less oil drag. If you
do this, you must check levels very frequently to see that you don't drop oil
levels even lower into the 'danger zone.'
Another 'non-sexy' but effective way to increase mpg is to keep an electric
block heater on while the truck is parked. The Dodge PCM computer richens the
mixture until the coolant temperature gets to 147 degrees F. By keeping the
block warm the engine goes into the more fuel efficient 'closed loop' control
sooner. This MPG improvement works best on trucks that do short trips. At 8
cents per kw-hr electric rates, running a 700 watt block heater for 8 hrs
costs 45 cents.
I changed out my original 3.55 differential gears on my 1995 Ram 5.9V8 46RH
auto to some $75 new-in-box (but 20 years old) Mopar ones of 3.21 ratio in
hopes of better mpg. I got about a
1 mpg improvement at 70 mph. Quarter mile times got worse by 0.75 second. My
5.9V8 now accelerates about like a 5.2, but has about a 5 mph increase in top
speed in 3rd gear as the gear ratio is more matched to peak hp. There is also
less engine noise while driving.
The Performance Trends software Fuel Economy Calculator predicts that above 74
mph a totally stock 1995 Ram 5.9V8 gets best MPG with a 3.55 diff gear, but
that if either the truck slows down below 70 mph, or the aerodynamics of the
truck are improved with such things as a tonneau bed cover or vortex
generators, then a 3.21 diff gear gives better MPG.
Note that on the 5.7Hemi with the new auto trans the overdrive gear ratio was
made "taller" to 0.67 from the old 0.69 at the same time that the 17 or 20
inch wheels & tires were made larger in diameter. This has an effect like
changing from 3.55
to 3.21 in the experiment above. The 2006 Hemi Rams with MDS come with a
factory standard 3.21 differential ratio.
A less restrictive muffler can help on a Ram. I switched from the stock
stainless steel muffler to Walker's 'QuietFlow' type made of aluminized steel
and gained about +1 mpg and dropped 0.2 seconds from the Q'mile. The QuietFlow
is as quiet as the stock muffler and has a 'Helmholz Resonator' section to get
rid of 'Drone' at highway speed rpms like the stock muffler had. Walker also
owns DynoMax, and the tech on the telephone told me the DynoMax is about 10%
less
restrictive than the QuietFlow but much louder. After 15,000 miles, my
QuietFlow began to rattle and I had to squeeze a dent in it with a large
C-clamp to stop the noise.
I later replaced the QuietFlow with a 30 inch long 'straight through' DynoMax
UltraFlo Stainless Steel 2.5 inch in, 2.5 inch out.
http://www.dynomax.com/mufflers.stm
part number 17298. This cut the wide open throttle exhaust backpressure from 7
psi to 5 psi. This reduction in backpressure only yielded a gain of about 0.2
MPG. The Ultraflo 17298 was a little louder than both the stock muffler and
the QuietFlow but just barely. Unfortunately it had a 'drone' at around 1800
rpm because it did not have the Helmholtz Resonator section like the previous
two mufflers. I later had to add an additional 16 inch long UltraFlo at the
very end of the pipe as a tip to eliminate the 1700-2000 rpm resonance when
cruising in overdrive. If you have a muffler without the Helmholtz Resonator
section you need to avoid having your tailpipe length from muffler outlet to
exhaust pipe tip anywhere near 66 inches - otherwise it will make this 'drone
noise' the same way a church organ makes a deep tone with a special length of
pipe. Make your tailpipe either much shorter or much longer.
I also moved my exhaust outlet to face rearward. A rear facing exhaust oulet
has a very very small 'jet engine' push to it - notice most cars exhaust
backwards - but trucks that pull trailers need a side exhaust to safety
exhaust carbon monoxide away from where it could cause
a deadly build up inside a camper.
On the 5.7 Hemi Rams, the large exhaust pipe sizes, muffler and resonator are
already fairly low restriction.
Headers are heavily advertised as helping MPG - a psychologically trick that
helps create sales - but in most cases headers don't do much because the
primary pipes on them are too short. Many headers are put on at the same time
as new less restrictive exhausts - and the header gets the credit for what the
bigger muffler actually did.
If you do buy a set of headers, try to get a custom set with primary pipe
lengths around 42-46 inches and don't worry if the primary diameter is
anywhere from 1.375 to 1.750 inches. This is in line with what Larry Shepard
found works best on the street with Mopar smallblock V8s, and it also agrees
with the estimates of the PerformanceTrends software program 'Engine Analyser
3.0' about getting torque gains from 1500-2000 rpm and then again from
3800-5000 rpm. The short primary pipe lengths that most header companies sell
give gains from 4000-5000 rpm only and don't really improve MPG in day to day
driving. To get the most MPG gains from a set of 42-48 inch primary pipe
headers you would also need to change your differential gears to a lower
numerical number - like 3.55 down to 3.21 - to make use of the extra torque
now available at the lower rpms.
A carefull MPG test of a 1995 1500 SB CC Ram with the 5.9V8 AT (3.21 diff)
with and without the "viscous clutch" radiator fan blades showed a 0.8 MPG
improvement without the fan. No overheating occured in this steady 70 MPH
test run over 212 miles.
There was also no sign of overheating at stoplights or city driving in
mild winter temperatures. Several Diesel Ram owners have posted that they can
run without a fan in winter and gain 0.5 to 1 MPG.
With the electric fan & clutch fan combo on the 5.7 Hemi Rams it is probable
that the clutch fan could be removed for all but the hottest weather or towing
service.
Weight reduction is supposed to improve City MPG where acceleration dominates.
The rule of thumb is
" A 10% reduction in weight yields a 6% improvement in City MPG."
So 540 lbs off a 5400 lb Ram might increase 14 MPG to 14.8 mpg.
At a steady 70 mph however, a 10% increase or decrease in weight only affects
MPG by about 3%.
The US Army is giving some of your tax dollars to Ford as a Research grant to
try out ways to cut the weight of a pickup truck by 25%.
Aluminum wheels save 40 lbs total. New Aluminum Magnum heads save 46 lbs.
Aluminum diff and rear axles saves 150 lbs. Fiberglass leaf springs save 75
lbs or monoleaf steel springs save 40 lbs. Do Google searches for 'monoleaf
spring' or 'fiberglass spring' to find suppliers who can make such springs for
Ram pickups.
Do you really need that rear bumper - are damaged bumpers less expensive to
replace than damaged sheet metal?
It is possible that 'Rhoads' style variable hydraulic lifters installed on a
Magnum engine would increase MPG by opening the exhaust valve later and nearer
bottom dead center and closing the intake valve sooner. One Ram owner with a
heavily modified 406 stroker Magnum V8 measured a 3 MPG gain when Rhoads
lifters were installed, but his camshaft was pretty 'wild' to the point that
he only had 7 inches vacuum at idle originally and that improved to 11 inches
of vacuum after the Rhoads lifters were fitted.
http://www.rhoadslifters.com/new_products.html
A 'RV' grind camshaft with lesser duration does this too.
This gets the last little bit of energy out of the combustion
pressure, increases 1500-2500 torque, but it also hurts higher rpm horsepower.
Higher compression ratio pistons are a reliable way to get better MPG.
Usually this means you have to purchase more expensive higher octane gasoline.
Raising the compression ratio from 9 to 9.5 is estimated to give 1% better
MPG. On a Magnum 5.9V8, changing the stock head gasket thickness of 0.047
inches to a Cometic 0.025 gasket will raise the compression ratio from 8.9 to
9.3. Replacing the stock 5.9V8 pistons (with their -13 cc depressions in the
crowns) with flat top pistons of compression height 1.626 inches will raise
the compression ratio from 8.9 to 10.2 Using flat top 1.67 inch compression
height pistons will raise the compression ratio from 8.9 to 11.3
This webpage has hard to find details about compression ratio increases from
milling cylinder heads of various sizes and makes.
http://home.isoa.net/~mharrisj/mill.html
Jim McFarland is an advocate of modifying piston tops. His design for the 4.00
inch Chevy 350 piston could easily be applied on flat top Magnum 5.2 pistons:
The 'soapdish' piston top on Magnum 5.9V8s might need some modification but
the 3 sets of dimples might still go in the same general areas. McFarland
claims 2-5% gains from this piston top modification. More info at:
http://circletrack.com/techarticles/99078/
Special ceramic coatings on the crowns of pistons and on the combustion
chamber of the cylinder head can improve both fuel economy and torque by
holding heat inside where it can produce pressure on the piston. Racing
engine builder Joe Sherman states that these coatings can add 2-3% to
performance, but if professionally applied they can be so expensive that the
mod would not pay for itself in fuel savings. There is an article about
applying coatings yourself at:
http://circletrack.com/techarticles/...139_0307_coat/
Fitting 6.1 Hemi cylinder heads on a 5.7 Hemi should boost the compression
ratio by about 1 point, and the sodium filled exhaust valve on the 6.1 cyl
head would also help control pinging and detonation with this higher ratio.
There are combustion chamber designs that claim to allow compression ratios of
12 to 14 on 87 octane gasoline. You can read about them at:
http://www.theoldone.com/articles/The_Soft_Head_1999/
Sparkplug and ignition advance changes.
I did a careful test run of 311 miles after indexing sparkplugs in a 5.9V8 and
measured what might have been a 4% improvement. That could be random
variation. To index the plugs, buy 16 instead of the usual 8 and choose plugs
that tighten down so that the gap
points toward the V of the engine and the ground electrode is on the fender
side. Return the 8 plugs you don't use to the store or give them to another
Ram owner. This puts the metal post of the ground electrode over against the
metal wall of the cylinder head where it does not
block the growth of the flame. See this webpage for a view of the combustion
chamber. In the picture the bottom is toward the fender and the top is toward
the center V of the V8 engine:
There is an article with several good illustrations of sparkplug indexing at
this Phord site:
http://www.fordmuscle.com/archives/2...gs/index.shtml
On a 5.7Hemi, it is very probable that by re-arranging the stock 16 plugs to
their best position in the cylinder that is 'lucky for them', you could
achieve indexing without buying more than 4-6 additional plugs at most,
perhaps none at all. Aim the open gap toward the exhaust valve.
Tests of the Bosch+4 sparkplugs at 60 and 70 mph highway speeds with 87 octane
gasoline found no MPG improvement - actually a slight loss - on a 1500 1995 SB
CC
Ram with 5.9V8 AT. A further test of the Bosch+4 sparkplugs with one of the
electrodes closest to the exhaust valve cut off (making a Bosch+3) also showed
no MPG gain. Consumers Reports found similar results when trying Bosch+4
sparkplugs on a Honda.
There is controversy about MPG and thermostat temperatures. Pure theory says
that cooler air intake temperatures give improved MPG because cooler air takes
slightly less hp to compress, and if the thermostat is cooler on old fashioned
iron or aluminum intake manifolds with coolant cross-over passages there will
be less temperature rise in the intake air as it passes through. Modern
intake manifolds such as the ones on the 4.7V8 and 5.7Hemi are made of
insulating plastic so this does not apply as much - although the incoming air
can still pick up heat from the metal cylinder head ports.
But hotter oil on cylinder walls has less viscosity and creates less
friction against the piston rings - which can also mean better MPG. The
Cummins 'Secrets of Better Fuel Economy' white paper listed at the top has a
graph showing
this on page 12. Theory also predicts that hotter block walls and cylinder
heads will absorb less heat from combustion and permit a greater pressure
'push' on the
piston.
Some Dakota owners who switched to 180 degree thermostats have reported less
ping, peppier acceleration and about +1 mpg, although most reports like this
are just about what their next tank of gasoline yielded - not a careful test
that you can trust.
Other Dakota owners reported no mpg change or a loss. Four Wheeler magazine
reported +0.8 mpg gain with a 192 to 180 deg thermo swap in a 454 Suburban.
My own experiments with failed thermostat that cracked and stayed open at
around 140 degrees, then later thermostats of 180, 195 (stock) and 205 showed
no significant
improvement in MPG at steady 60 mph highway cruise on a 1995 5.9V8 Ram CCab
shortbed, although the 205 did show a small 0.2 MPG gain in one 300 mile test
run. The 180 degree thermostat also did not reducing pinging, nor did the 205
thermostat increase pinging. This may be because the PCM computer senses
coolant temperature and either advances or retards ignition timing as
necessary according to the tables in the memory of the computer. The cracked
thermostat that stayed open at about 140 did reduce pinging. When you read
that 180 degree thermostats reduced pinging on old carburetor engines that
might be true, but consider that todays computer controlled engines 'have a
mind of their own.'
The Fuel Economy Calculator from Performance Trends software predicts that a
change from a 195 degree thermostat to a 175 worsens MPG by about 0.20 at a
steady 70 mph.
Respected tech editior Marlan Davis of Hot Rod magazine has reported that
all things considered, fuel economy is better with coolant at 210 degrees F.
Perhaps that is why the factory thermostat on the 5.7 Hemi is now marked 203
F, which is were it begins opening. Note that on 4.7 and 5.7Hemi engines the
thermostat position and function has been totally redesigned to control the
coolant in, rather than the coolant out temperature. The 5.7V8 now also has a
closing bypass post sticking out from it that closes off the passage and
results in greater coolant flow to the radiator once the engine is up to
designed temperature.
Undersized crank pulleys can increase MPG slightly by driving the power
steering, air conditioning compressor, and water pump at lower rpm where there
will be less friction.
Some who have tried undersized pulley sets report an additional oversized
alternator pulley in a pulley set is too slow for the street truck that may
have to idle a long time without enough
rpm to charge the battery. The horsepower that an alternator consumes is
mostly set not by the rpm it turns, but by how much the 'voltage regulator'
inside the Ram pickups PCM computer increases the 'field' inside the
alternator. Because of this I see no benefit in slowing an alternator down -
no significant horsepower will be saved.
The last MPG technique is the simplest, but the one few of us want to hear. I
have done several 300-400 mile test runs at steady 60 or 70 mph on I95.
Slowing down from 70 to 60 mph saved 3-4 mpg each time. I also did a 80 mph
test run once driving with the crazy flow of traffic from north of West Palm
Beach to Ft Lauderdale. This lowered MPG by 4 compared to going 70 mph.
Notice that I don't claim this slowing down is 'cheap' because of the
question: 'How much is your time worth ?'
If you want to read more about MPG improvements that work,
the US government has put a book online at:
http://books.nap.edu/books/030904530...8.html#pagetop
In the Appendix of this book is an interesting table where the Dept of Energy
sent a questionaire to all the auto makers and asked them what various mods
were worth to improving MPG.
The EPA has put out a long report on fuel economy trends from 1975-2005.
There is much good tech info here, especially around page 36.
http://www.theautochannel.com/link.h...q/fetrends.htm
Kevin Gertgen's Fuel Economy Calculator software is very impressive and can be
read about at:
http://www.performancetrends.com/fue...calculator.htm
There is an online Java based webpage calculator at:
http://www.bgsoflex.com/mpg.html
Jeffery Diamond's Mopar specific gas mileage mod table is worth pondering:
http://victorylibrary.com/mopar/mileage-c.htm
There is a collection of aerodynamic links concentrated on pickup trucks at:
http://www.dodgetrucks.org/forums/viewtopic.php?t=52115
and has been modified but needs
to be re-written for 3rd gen Rams
but the basic principles apply.
With the dual sparkplugs and deep-in-block knock sensors the 5.7 might really
benefit from a special design piston that raises compression ratio and shifts
the combustion space over toward the exhaust side.
Aerodynamics is even more important on 3rd gen Rams to improve highway mpg
because they have gotten taller, wider (increases frontal area) and blunter
(worse in engineering term called Cd or 'coefficient of drag').
Those with Cummins engines may first want to read the 'White Paper'
from Cummins called:
"Secrets of Better Fuel Economy: The Physics of MPG"
which is oriented toward 18 wheel trucks but 90% applies to Ram pickups too.
http://www.cummins.com/na/pdf/en/pro..._Whitepape.pdf
beginning of original post:
Ram Pickup MPG improvement discussion :
{last modified 08-02-05}
Many Ram pickup owners start trying to improve MPG by first trying engine
modifications. Unfortunately, the efficiency of most modern engines is
already highly developed after 100 years of improvements, and this is the
toughest place to start, and many Ram owners make bad choices and waste money
that could have simply been spent on more gasoline.
The cheapest and most cost effective mods are usually aerodynamic improvements
that help high speed highway MPG, because a factory stock Ram has the Cd of a
brick, perhaps because many buyers value a big grille over a slick shape.
Second easiest MPG improvement comes when it is time to buy new rubber, where
good choices about the rolling resistance of tires will improve both City and
Highway MPG. Unfortunately finding information about what engineers call Crr
of a tire requires a good deal of looking and most tire makers actually hide
this information.
Next, there are drivetrain mods that will allow your engine to operate at 2/3
throttle and the best piston speed. This is where it turns fuel into
horsepower most efficiently even without internal engine part changes. Yes, I
said 'piston speed' and not a 'magic' rpm range called 'The Powerband'
Last, for the most work and the most money, there are mods to the engine
itself that will improve fuel efficiency when the throttle is only partially
open, but be prepared to give up some of the engine stuff you read in the past
in old hot rod magazines that was based on engines operating at full throttle
and meant for producing maximum horsepower.
This is a long article that is divided into three main sections: aero mods,
tire mods, and engine&drivetrain mods. At the end are weblinks to much
additional information. Feel free to skip to anything that suits your fancy.
AERODYNAMIC MODS
As others have said, a hard tonneau can lower the aerodynamic drag. I
installed a ARE hard tonneau and found it was good for about 1 mpg
improvement. Ford says that a soft tonneau is good for +1 mpg on the F150 and
tried to get the EPA to allow them to add this to their highway MPG result by
re-classifying the tonneau 'standard equipment.'
This Fibernetics hard tonneau has a 'Roofline Extention Spoiler' on the back
that might help MPG a bit more than a conventional design. Here's a view of
the rear spoiler, but on a F150:
There is an interesting student project on a aero improvements tried on a
Dodge Ram model truck several posts down at this link:
http://www.dodgetrucks.org/forums/viewtopic.php?t=52115
If there are astericks in the above weblink, replace them with the letters
d-o-d-g-e-t-r-u-c-k-s.-o-r-g without any dashes, or go directly to the stored
old pages here:
http://web.archive.org/web/200304141...affner/did.htm
and
http://web.archive.org/web/200304142...er/Tonneau.htm
Note that the students found that camper tops and removed tailgates hurt, but
tonneaus and lowered tailgates helped slightly.
It is possible that a 2inch front/4 inch rear drop on a Ram suspension could
improve the aerodynamic drag. There is some evidence that on a 1996 Indy Ram
this improved the Cd by a few hundreds.
The 3rd gen body on the SRT10 Ram uses a 4/6 inch lowered stance, a rear wing,
tonneau, and perhaps partially block off of the 'too big' radiator grille to
lower its aerodynamic Cd from the 0.50 of the stock 2500 Ram to the SRT10's
value of 0.45
Bug shields at the front of Rams nearly always hurt MPG.
The Dodge Ram Diesel that set the Bonneville speed record had 'Mooneye' wheel
cover discs. These are supposed to reduce aero drag by 1-2% but hurt brake
cooling. I also notice this Ram had mirrors and wipers removed.
A MPG test over a roundtrip of a section of I40 at a steady 70 mph showed
0.7 MPG worse without the Ram's stock front bumper air dam, than with the
stock air dam in place. Other 2500/3500 Diesel Ram owners have reported
better MPG after taking off their air dam on the TDR website - but those tests
did not seem to be carefully done.
I have recently had some aerodynamic success with home-made little aluminum
tabs called 'Wheeler Vortex Generators'. I mounted 5 just behind the side cab
windows, and another 5 just in front of the rear brake lights. These improved
my coasting speed down a 6% grade hill by 2 mph, and also improved MPG at a
steady 70 mph by 1 mpg.
I had previously tried this product on the roof of the truck, but it did not
work:
The vortex generators I made were cut from 5 inch by 7 inch aluminum
'flashing' from Home Depot. You cut the flashing into 3 and 9/16th inch
circles, and then bend the sides up to form the 'wings'. A circle of course
has 360 degrees. The front of the wings take up 107 degrees of the circle,
and the back takes up 22 degrees. The finished product looks like this:
but without the magnet backing. I used 3M 'Super Strong' outdoor mounting
tape from Target to stick the vortex generators to the truck's sheet metal.
I am still testing with the Wheeler Vortex generators. I have tried bending
dimes into tiny ones for the mirrors - but no measureable change. I have also
tried little 1.5 inch ones on the bottom of the Ram airdam - felt more stable
but MPG tests showed worse results. The best results have been on the sides of
the cab and on the sides of the pickup bed ahead of the tail lights. This
inexpensive mod can be good for better MPG especially at higher speeds.
There is also a commercial vortex generator called 'Airtabs' made of various
plastics and perhaps a bit lower in drag than a home made Wheeler type. These
are $3 each.
TIRE MODS
Increasing the air pressure in your tires, and picking a narrow 'rib tread'
commercial delivery truck type tire that has low rolling resistance
definitely helps MPG. Raising the air pressure by 15 psi to the max 70 psi in
Goodyear Wrangler HT 235/85R16E tires increased my mpg by +1 in a 311 mile
test run - but the ride was bone jarring. A narrow, highway rib tire like the
HT gives the lowest rolling resistance. Wide, aggressive tread tires can be
three times harder to roll. It might pay to have a 4 tire set for the weekday
commute, and a weekend mudder wide tire set.
Consumers Reports is the only organization I know of that tests for rolling
resistance of tires.
Quote from CR:
" Fuel mileage at a price. Some tires roll with less drag than others. The
lower a tire's rolling resistance, the more fuel you can save. Those savings
can be significant. {Pickup and SUV} Tires with the lowest rolling resistance
delivered nearly 2 mpg more at a steady 65 mph in our highway tests {2003
four-wheel-drive Ford Explorer XLT 4x4} than those with the highest rolling
resistance. The catch: While some high-scoring tires had low rolling
resistance, most tires with the lowest rolling resistance also had lower
overall scores."
In their 11/2004 Pickup & SUV tire test CR the
lowest rolling resistance tires rated 'excellent' were the:
Bridgestone Dueler H/T (D684)
Michelin Cross Terrain
Continental ContiTrac
BF Goodrich Radial Long Trail T/A
The Pickup & SUV tires with the worst rolling resistance were the:
Pirelli Scorpion STA
Kelly Safari Signature
Yokohama Geolander H/T-SG051
A tire with a 'very good' rolling resistance and high scores in other handling
and braking tests was the Hankook DynaPro AS RH03
The California Air Resources board is pressing the tire companies to make
rolling resistance measurements on tires freely available to the public by
2008, one of the few worth while things CARB has ever done in my opinion
The lower profile 17 and 20 inch tire designs used on the 2003-2005
5.7Hemi Rams have a 'sticker' tire tread and higher rolling resistance than
earlier year Rams. It is probable that if a manufacturer makes available a
235 85 R17 tire in Load
Range E it would be lower rolling resistance than the stock tires and might
improve MPG by 1-2 at 70 mph.
The 2006 Ram press release says the new model will have 'low rolling
resistance tires.'
ENGINE, LUBRICANT, EXHAUST & DRIVETRAIN MODS
Switching to synthetic lubricants - - engine oil, diff, Amsoil C+ Mopar-spec
transmission fluid, and syn greases in wheel bearings is good for 2-5% MPG
improvement. That is only about 0.5 mpg but every little bit helps.
Larry Shepard writes in the 'Magnum Engines' book published by Mopar Perf that
running engine oil and transmission ATF levels 1-0.5 quarts below the 'add'
marks on the dipsticks can increase MPG slightly due to less oil drag. If you
do this, you must check levels very frequently to see that you don't drop oil
levels even lower into the 'danger zone.'
Another 'non-sexy' but effective way to increase mpg is to keep an electric
block heater on while the truck is parked. The Dodge PCM computer richens the
mixture until the coolant temperature gets to 147 degrees F. By keeping the
block warm the engine goes into the more fuel efficient 'closed loop' control
sooner. This MPG improvement works best on trucks that do short trips. At 8
cents per kw-hr electric rates, running a 700 watt block heater for 8 hrs
costs 45 cents.
I changed out my original 3.55 differential gears on my 1995 Ram 5.9V8 46RH
auto to some $75 new-in-box (but 20 years old) Mopar ones of 3.21 ratio in
hopes of better mpg. I got about a
1 mpg improvement at 70 mph. Quarter mile times got worse by 0.75 second. My
5.9V8 now accelerates about like a 5.2, but has about a 5 mph increase in top
speed in 3rd gear as the gear ratio is more matched to peak hp. There is also
less engine noise while driving.
The Performance Trends software Fuel Economy Calculator predicts that above 74
mph a totally stock 1995 Ram 5.9V8 gets best MPG with a 3.55 diff gear, but
that if either the truck slows down below 70 mph, or the aerodynamics of the
truck are improved with such things as a tonneau bed cover or vortex
generators, then a 3.21 diff gear gives better MPG.
Note that on the 5.7Hemi with the new auto trans the overdrive gear ratio was
made "taller" to 0.67 from the old 0.69 at the same time that the 17 or 20
inch wheels & tires were made larger in diameter. This has an effect like
changing from 3.55
to 3.21 in the experiment above. The 2006 Hemi Rams with MDS come with a
factory standard 3.21 differential ratio.
A less restrictive muffler can help on a Ram. I switched from the stock
stainless steel muffler to Walker's 'QuietFlow' type made of aluminized steel
and gained about +1 mpg and dropped 0.2 seconds from the Q'mile. The QuietFlow
is as quiet as the stock muffler and has a 'Helmholz Resonator' section to get
rid of 'Drone' at highway speed rpms like the stock muffler had. Walker also
owns DynoMax, and the tech on the telephone told me the DynoMax is about 10%
less
restrictive than the QuietFlow but much louder. After 15,000 miles, my
QuietFlow began to rattle and I had to squeeze a dent in it with a large
C-clamp to stop the noise.
I later replaced the QuietFlow with a 30 inch long 'straight through' DynoMax
UltraFlo Stainless Steel 2.5 inch in, 2.5 inch out.
http://www.dynomax.com/mufflers.stm
part number 17298. This cut the wide open throttle exhaust backpressure from 7
psi to 5 psi. This reduction in backpressure only yielded a gain of about 0.2
MPG. The Ultraflo 17298 was a little louder than both the stock muffler and
the QuietFlow but just barely. Unfortunately it had a 'drone' at around 1800
rpm because it did not have the Helmholtz Resonator section like the previous
two mufflers. I later had to add an additional 16 inch long UltraFlo at the
very end of the pipe as a tip to eliminate the 1700-2000 rpm resonance when
cruising in overdrive. If you have a muffler without the Helmholtz Resonator
section you need to avoid having your tailpipe length from muffler outlet to
exhaust pipe tip anywhere near 66 inches - otherwise it will make this 'drone
noise' the same way a church organ makes a deep tone with a special length of
pipe. Make your tailpipe either much shorter or much longer.
I also moved my exhaust outlet to face rearward. A rear facing exhaust oulet
has a very very small 'jet engine' push to it - notice most cars exhaust
backwards - but trucks that pull trailers need a side exhaust to safety
exhaust carbon monoxide away from where it could cause
a deadly build up inside a camper.
On the 5.7 Hemi Rams, the large exhaust pipe sizes, muffler and resonator are
already fairly low restriction.
Headers are heavily advertised as helping MPG - a psychologically trick that
helps create sales - but in most cases headers don't do much because the
primary pipes on them are too short. Many headers are put on at the same time
as new less restrictive exhausts - and the header gets the credit for what the
bigger muffler actually did.
If you do buy a set of headers, try to get a custom set with primary pipe
lengths around 42-46 inches and don't worry if the primary diameter is
anywhere from 1.375 to 1.750 inches. This is in line with what Larry Shepard
found works best on the street with Mopar smallblock V8s, and it also agrees
with the estimates of the PerformanceTrends software program 'Engine Analyser
3.0' about getting torque gains from 1500-2000 rpm and then again from
3800-5000 rpm. The short primary pipe lengths that most header companies sell
give gains from 4000-5000 rpm only and don't really improve MPG in day to day
driving. To get the most MPG gains from a set of 42-48 inch primary pipe
headers you would also need to change your differential gears to a lower
numerical number - like 3.55 down to 3.21 - to make use of the extra torque
now available at the lower rpms.
A carefull MPG test of a 1995 1500 SB CC Ram with the 5.9V8 AT (3.21 diff)
with and without the "viscous clutch" radiator fan blades showed a 0.8 MPG
improvement without the fan. No overheating occured in this steady 70 MPH
test run over 212 miles.
There was also no sign of overheating at stoplights or city driving in
mild winter temperatures. Several Diesel Ram owners have posted that they can
run without a fan in winter and gain 0.5 to 1 MPG.
With the electric fan & clutch fan combo on the 5.7 Hemi Rams it is probable
that the clutch fan could be removed for all but the hottest weather or towing
service.
Weight reduction is supposed to improve City MPG where acceleration dominates.
The rule of thumb is
" A 10% reduction in weight yields a 6% improvement in City MPG."
So 540 lbs off a 5400 lb Ram might increase 14 MPG to 14.8 mpg.
At a steady 70 mph however, a 10% increase or decrease in weight only affects
MPG by about 3%.
The US Army is giving some of your tax dollars to Ford as a Research grant to
try out ways to cut the weight of a pickup truck by 25%.
Aluminum wheels save 40 lbs total. New Aluminum Magnum heads save 46 lbs.
Aluminum diff and rear axles saves 150 lbs. Fiberglass leaf springs save 75
lbs or monoleaf steel springs save 40 lbs. Do Google searches for 'monoleaf
spring' or 'fiberglass spring' to find suppliers who can make such springs for
Ram pickups.
Do you really need that rear bumper - are damaged bumpers less expensive to
replace than damaged sheet metal?
It is possible that 'Rhoads' style variable hydraulic lifters installed on a
Magnum engine would increase MPG by opening the exhaust valve later and nearer
bottom dead center and closing the intake valve sooner. One Ram owner with a
heavily modified 406 stroker Magnum V8 measured a 3 MPG gain when Rhoads
lifters were installed, but his camshaft was pretty 'wild' to the point that
he only had 7 inches vacuum at idle originally and that improved to 11 inches
of vacuum after the Rhoads lifters were fitted.
http://www.rhoadslifters.com/new_products.html
A 'RV' grind camshaft with lesser duration does this too.
This gets the last little bit of energy out of the combustion
pressure, increases 1500-2500 torque, but it also hurts higher rpm horsepower.
Higher compression ratio pistons are a reliable way to get better MPG.
Usually this means you have to purchase more expensive higher octane gasoline.
Raising the compression ratio from 9 to 9.5 is estimated to give 1% better
MPG. On a Magnum 5.9V8, changing the stock head gasket thickness of 0.047
inches to a Cometic 0.025 gasket will raise the compression ratio from 8.9 to
9.3. Replacing the stock 5.9V8 pistons (with their -13 cc depressions in the
crowns) with flat top pistons of compression height 1.626 inches will raise
the compression ratio from 8.9 to 10.2 Using flat top 1.67 inch compression
height pistons will raise the compression ratio from 8.9 to 11.3
This webpage has hard to find details about compression ratio increases from
milling cylinder heads of various sizes and makes.
http://home.isoa.net/~mharrisj/mill.html
Jim McFarland is an advocate of modifying piston tops. His design for the 4.00
inch Chevy 350 piston could easily be applied on flat top Magnum 5.2 pistons:
The 'soapdish' piston top on Magnum 5.9V8s might need some modification but
the 3 sets of dimples might still go in the same general areas. McFarland
claims 2-5% gains from this piston top modification. More info at:
http://circletrack.com/techarticles/99078/
Special ceramic coatings on the crowns of pistons and on the combustion
chamber of the cylinder head can improve both fuel economy and torque by
holding heat inside where it can produce pressure on the piston. Racing
engine builder Joe Sherman states that these coatings can add 2-3% to
performance, but if professionally applied they can be so expensive that the
mod would not pay for itself in fuel savings. There is an article about
applying coatings yourself at:
http://circletrack.com/techarticles/...139_0307_coat/
Fitting 6.1 Hemi cylinder heads on a 5.7 Hemi should boost the compression
ratio by about 1 point, and the sodium filled exhaust valve on the 6.1 cyl
head would also help control pinging and detonation with this higher ratio.
There are combustion chamber designs that claim to allow compression ratios of
12 to 14 on 87 octane gasoline. You can read about them at:
http://www.theoldone.com/articles/The_Soft_Head_1999/
Sparkplug and ignition advance changes.
I did a careful test run of 311 miles after indexing sparkplugs in a 5.9V8 and
measured what might have been a 4% improvement. That could be random
variation. To index the plugs, buy 16 instead of the usual 8 and choose plugs
that tighten down so that the gap
points toward the V of the engine and the ground electrode is on the fender
side. Return the 8 plugs you don't use to the store or give them to another
Ram owner. This puts the metal post of the ground electrode over against the
metal wall of the cylinder head where it does not
block the growth of the flame. See this webpage for a view of the combustion
chamber. In the picture the bottom is toward the fender and the top is toward
the center V of the V8 engine:
There is an article with several good illustrations of sparkplug indexing at
this Phord site:
http://www.fordmuscle.com/archives/2...gs/index.shtml
On a 5.7Hemi, it is very probable that by re-arranging the stock 16 plugs to
their best position in the cylinder that is 'lucky for them', you could
achieve indexing without buying more than 4-6 additional plugs at most,
perhaps none at all. Aim the open gap toward the exhaust valve.
Tests of the Bosch+4 sparkplugs at 60 and 70 mph highway speeds with 87 octane
gasoline found no MPG improvement - actually a slight loss - on a 1500 1995 SB
CC
Ram with 5.9V8 AT. A further test of the Bosch+4 sparkplugs with one of the
electrodes closest to the exhaust valve cut off (making a Bosch+3) also showed
no MPG gain. Consumers Reports found similar results when trying Bosch+4
sparkplugs on a Honda.
There is controversy about MPG and thermostat temperatures. Pure theory says
that cooler air intake temperatures give improved MPG because cooler air takes
slightly less hp to compress, and if the thermostat is cooler on old fashioned
iron or aluminum intake manifolds with coolant cross-over passages there will
be less temperature rise in the intake air as it passes through. Modern
intake manifolds such as the ones on the 4.7V8 and 5.7Hemi are made of
insulating plastic so this does not apply as much - although the incoming air
can still pick up heat from the metal cylinder head ports.
But hotter oil on cylinder walls has less viscosity and creates less
friction against the piston rings - which can also mean better MPG. The
Cummins 'Secrets of Better Fuel Economy' white paper listed at the top has a
graph showing
this on page 12. Theory also predicts that hotter block walls and cylinder
heads will absorb less heat from combustion and permit a greater pressure
'push' on the
piston.
Some Dakota owners who switched to 180 degree thermostats have reported less
ping, peppier acceleration and about +1 mpg, although most reports like this
are just about what their next tank of gasoline yielded - not a careful test
that you can trust.
Other Dakota owners reported no mpg change or a loss. Four Wheeler magazine
reported +0.8 mpg gain with a 192 to 180 deg thermo swap in a 454 Suburban.
My own experiments with failed thermostat that cracked and stayed open at
around 140 degrees, then later thermostats of 180, 195 (stock) and 205 showed
no significant
improvement in MPG at steady 60 mph highway cruise on a 1995 5.9V8 Ram CCab
shortbed, although the 205 did show a small 0.2 MPG gain in one 300 mile test
run. The 180 degree thermostat also did not reducing pinging, nor did the 205
thermostat increase pinging. This may be because the PCM computer senses
coolant temperature and either advances or retards ignition timing as
necessary according to the tables in the memory of the computer. The cracked
thermostat that stayed open at about 140 did reduce pinging. When you read
that 180 degree thermostats reduced pinging on old carburetor engines that
might be true, but consider that todays computer controlled engines 'have a
mind of their own.'
The Fuel Economy Calculator from Performance Trends software predicts that a
change from a 195 degree thermostat to a 175 worsens MPG by about 0.20 at a
steady 70 mph.
Respected tech editior Marlan Davis of Hot Rod magazine has reported that
all things considered, fuel economy is better with coolant at 210 degrees F.
Perhaps that is why the factory thermostat on the 5.7 Hemi is now marked 203
F, which is were it begins opening. Note that on 4.7 and 5.7Hemi engines the
thermostat position and function has been totally redesigned to control the
coolant in, rather than the coolant out temperature. The 5.7V8 now also has a
closing bypass post sticking out from it that closes off the passage and
results in greater coolant flow to the radiator once the engine is up to
designed temperature.
Undersized crank pulleys can increase MPG slightly by driving the power
steering, air conditioning compressor, and water pump at lower rpm where there
will be less friction.
Some who have tried undersized pulley sets report an additional oversized
alternator pulley in a pulley set is too slow for the street truck that may
have to idle a long time without enough
rpm to charge the battery. The horsepower that an alternator consumes is
mostly set not by the rpm it turns, but by how much the 'voltage regulator'
inside the Ram pickups PCM computer increases the 'field' inside the
alternator. Because of this I see no benefit in slowing an alternator down -
no significant horsepower will be saved.
The last MPG technique is the simplest, but the one few of us want to hear. I
have done several 300-400 mile test runs at steady 60 or 70 mph on I95.
Slowing down from 70 to 60 mph saved 3-4 mpg each time. I also did a 80 mph
test run once driving with the crazy flow of traffic from north of West Palm
Beach to Ft Lauderdale. This lowered MPG by 4 compared to going 70 mph.
Notice that I don't claim this slowing down is 'cheap' because of the
question: 'How much is your time worth ?'
If you want to read more about MPG improvements that work,
the US government has put a book online at:
http://books.nap.edu/books/030904530...8.html#pagetop
In the Appendix of this book is an interesting table where the Dept of Energy
sent a questionaire to all the auto makers and asked them what various mods
were worth to improving MPG.
The EPA has put out a long report on fuel economy trends from 1975-2005.
There is much good tech info here, especially around page 36.
http://www.theautochannel.com/link.h...q/fetrends.htm
Kevin Gertgen's Fuel Economy Calculator software is very impressive and can be
read about at:
http://www.performancetrends.com/fue...calculator.htm
There is an online Java based webpage calculator at:
http://www.bgsoflex.com/mpg.html
Jeffery Diamond's Mopar specific gas mileage mod table is worth pondering:
http://victorylibrary.com/mopar/mileage-c.htm
There is a collection of aerodynamic links concentrated on pickup trucks at:
http://www.dodgetrucks.org/forums/viewtopic.php?t=52115