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Suggestions needed for MPG FAQ
I would appreciate suggestions and corrections on this MPG improvement FAQ. If you have seen this FAQ before, there are now several new paragraphs on EGT cylinder balancing 'on the cheap', the pros/cons of underdrive pulleys, and good driving habits that boost MPG in the real world.
Warning: this is a long post, and somewhat in jest I advise printing it out and setting it by the john in the bathroom for reading and thinking about a bit at a time. ---------------------- This was written for second gen Rams and has been modified 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 FAQ post: Ram Pickup MPG improvement discussion : {last modified 01-18-06} 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 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 Motor Co officially 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' back in 1999. This Snugtop F2 hard tonneau has a built-in 'Roofline Extention Spoiler' on the back that might help MPG a bit more than a conventional design. Fibernetics has a similar rear spoiler with a bit more angle, shown here 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.****************/forums/v...ic.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 conventional camper tops and removed tailgates hurt, but tonneaus helped about 11%. The Society of Automotive Engineers (SAE) gave these students a prize for their experiment. 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 One reason the Chevy Siverado gets better highway MPG than a Ram is that it has a lowered drop for better aerodynamics compared to the Ram and F150. {The Silverado also is not as high, slightly narrower, is about 400 lbs lighter, and has an 5.3V8 with a shorter stroke and 9.9 compression ratio.} 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 commercial product on the roof of the truck, but it did not appear to work in my test runs: 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. I used 3M 'Super Strong' outdoor mounting tape from Target to stick the vortex generators to the truck's sheet metal. The finished product looks like this: [img]http://www.****************/gallery/data/500/medium/1972SideWindowVGs.JPG[/img] [img]http://www.****************/gallery/data/500/medium/1972TaillightVGs.JPG[/img] 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. It has occurred to me that with a heat gun to soften the plastic you could make these vortex generators out of the various sized computer CD's or DVD discs but I have not tried that yet. There is also a commercial vortex generator called 'Airtabs' that is perhaps a bit lower in drag than a home made Wheeler type. These are available in black, white and clear plastic. They 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 will help 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 a wee bit 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? Optima batteries are usually 10-20 lbs lighter than conventional. Engine modifications Each of the cylinders in a Ram pickup engine is a little different than its neighbor cylinders due to 'production tolerance' at the factory. In the 2003 official Ram Field Service Manual (FSM) specifications for the 5.7 Hemi the table has a line saying the variation between cylinders can be 25% and still be acceptable to DaimlerChrysler. Each cylinder's fuel injector sprays slight different amounts of fuel per second, and each cylinder has a slightly different airflow through its intake runner, cylinder head port and valve. If you are lucky, just by chance your engine will have its highest flowing fuel injectors installed in the cylinders that also have the highest flowing airflow. If you are unlucky, your 'lemon' engine has the lowest flowing fuel injectors installed in the cylinders with the highest airflows, and vice versa. The amount of air mixed with fuel is called the 'air to fuel ratio' (AFR) and for decades racers and engineers have known that this AFR ratio affects fuel economy, torque, and the temperature of the exhaust gas coming out of the cylinder. Also for decades, people have tried to 'tune' the AFR by measuring the temperature of the exhaust gas. The best setups for this are expensive, but you can buy much less expensive instruments today. Sears has multimeters like this one with a retail price of $40 but is sometimes on sale for $20: http://www.sears.com/sr/javasr/produ...26+Accessories that has a Type K thermocouple that will measure from 0F to 1400F if you are careful not to burn the insulation, which is only rated to 550F. By drilling a hole in your exhaust manifold at the 'traditional' distance of 1 inch out from the exhaust port and inserting this thermocouple you can measure your exhaust gas temperature (EGT) and then swap around fuel injectors to the cylinders where the combinations yield nearly equal EGT for all cylinders. By equallizing your EGT you can improve both torque and fuel economy - and an added bonus is that your engine will be less likely to 'ping' on one cylinder. How much improvement can you get? It depends on how unlucky your engine was from the factory, but typical improvements if you can get the cylinders nearly equal are 6% better fuel economy at part throttle operation during highway cruise, and 4% better power at wide open throttle too. Some notes on EGT testing: If you can find the Sears multimeters on sale for $20 it might be better to buy 4 and test one side of a V8 at the same time, then later give away the other 3 multimeters as gifts to friends and family. With the 36 inch long leads from the thermocouple tip to multimeter you will have limited distance so mount the meter outside your windshield, at the rear edge of the hood, perhaps mounting 4 meters on the same board. Choose a hole size to drill that you can later close off with a blind rivet or tap and close with a stainless steel screw. Buy a $12 'muffler patch' kit and use the high temperature felt gasket material to place under and over the thermocouple wires for protection and insulation, then use a large stainless steel hose clamp to hold the thermocouple in place during testing. Make each test run on the same stretch of highway at about the same air temperature with the same gasoline. Measuring EGT at the rpm of maximum torque at full throttle is the normal spot to record the temperatures. Testing on a steep hill where rpm changes more slowly as the truck climbs and you can stay at legal speed is a wise idea. Have a partner drive while you watch the meters. One note on the limitations of EGT testing - your engine's cylinders also vary in their true 'dynamic' compression ratio due to sloppy factory tolerances. Cylinders with higher compression ratios will have LOWER EGT readings even if the AFR is the same. You can get hints about what cylinders have higher dynamic compression ratio by doing a compression test on all cylinders before EGT testing. The best way of balancing AFR on cylinders is to use a 'wide range' O2 sensor in each cylinder's exhaust. This has been very expensive in the past but the cost of wide range O2 instruments has been coming down. See these two links: http://carcraft.com/techarticles/116_0402_tune/ http://performancetrends.com/wide_band_uego.htm Valve Timing & MPG 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. Lesser duration on the exhaust valve cam lobe usually closes the valve later toward bottom dead center and gets the last little bit of energy out of the combustion pressure, increases 1500-2500 torque, but it also hurts higher rpm WOT horsepower when large amounts of exhaust gas is trying to escape the cylinder and now has to start later. 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 Ford 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. Coolant temperatures and thermostat settings 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 5.7 Hemi 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 thermostat swap in a 454 Suburban. Take these reports with a grain of salt considering who did them and how magazines live on advertising. 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 'excitation field current' inside the alternator's rotor. Because of this I see no benefit in slowing an alternator down - no significant horsepower will be saved or fuel economy gained. The AC compressor can be simply turned off when you want either more power or better MPG. NASCAR cooling system guru Howard Stewart points out that on modern engines like the Chrysler 4.7/5.7 with knock sensors if you slow down the water pump you might have more horsepower for the first few seconds at Wide Open Throttle, but then the cylinder head will begin overheating at its worst spot, some pinging will start, the knock sensors will trigger, and the PCM computer will start pulling back up to 16 degrees of ignition timing advance - then the horsepower declines much more than you "saved" with the water pump pulley reduction. If you must change pulleys it is best to just slow down the power steering pump alone. In the Cummins White Paper they cite a study where there was a 30% variation in MPG between professional drivers in the exact same truck over the same route. This is similar to GM research, such as this from from page A3 of The Wall St Journal on 11-21-2005: "Roger Clark, GM's senior manager of energy and drive quality in North America, said the current test does a good job measuring average mileage but the problem is the variation in how people drive. He cited a GM Study of 209 people driving the same midsize SUV. The fuel economy varied from about 13 miles per gallon to 23 miles per gallon, depending on the driver." There are 'experts' at driving to get the best MPG. You can read about John and Helen Taylor, a husband & wife couple who are sponsored by Shell and have won many contests at this link: http://www.scoop.co.nz/stories/SC0601/S00020.htm Note the list of good driving techniques for better MPG near the end of the article about the Taylors. 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.****************/forums/v...ic.php?t=52115 |
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Would really appreciate any suggestions,
such as: 1. tricks to make high compression ratios live with pump gasoline like cylinder head cooling tricks 2. which differentials have the least friction drag 2.1 which water pumps use the least hp to pump the same or more water 3. which fuel injectors spray the best droplets 4. any dyno information that shows a particular brand ignition really works in the 1500-3500 rpm range 5. any time q'mile slip information that shows changing out front tires to low rolling resistance ones really works 6. any dyno information that a particular bore coating or particular ring set reduces friction 7. any dyno information that cutting down cranks to fit Honda bearings reduces friction 8. any internal automatic transmission rebuilding tips that reduce friction 9. vehicle weight reduction tips of any sort 10. How you will soon have the Warp Drive system working inside the alternator after getting that 'beyond the grave' message from Scotty.... [image]http://seattlepi.nwsource.com/fun/speed/01212006.gif[/image] [image]http://seattlepi.nwsource.com/fun/speed/01202006.gif[/image] |
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Ha. leave the tailgate UP. This creates a vortex of high pressure air rolling axially (?) inside the bed that deflects the air coming over the cab, creating a "fastback" design. Tailgate down doesnt create or "hold" the vortex, and a huge vacuum builds behind the cab, all you have to do to check this is to open the slider a tad. Ford proved this on the new F150 wind tunnel test and so did MythBusters! Ditch the Gator-net!!!
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