Improving fuel economy

[2000StreetRod]

For ease of reference this page contains the latest fuel economy results and associated vehicle configuration. Please note that Upstate South Carolina is fairly hilly for both city and highway driving. Highway mileage is based on a 100 mile round trip between Greenville and Gaffney maintaining posted speed limits using cruise control. Approximately 20 of the 100 miles is boulevard/city driving.

Fuel Economy Results - Goal 20 mpg city

87 octane unleaded regular with up to 10% ethanol
City driving: 16.4 mpg
Highway driving: 23.0 mpg

Associated Configuration

Body: 3900 lbs with full tank & spare tire, no driver, side steps removed
Tires: BFG P235/75R15XL Long Trail TA Tour @35psi
Suspension: front lowered 0.75 inch via torsion bars, rear lowered 0.75 inch by replacing monoleaf springs with 3+1 leaf springs, Edelbrock IAS lowering shocks
Rear axle: 3.73:1 open differential with Super Tech 75W140 synthetic lubricant
Induction: Spectre cone air filter with 4 inch dia. outlet drawing air from engine compartment, Lightning 90 mm MAF sensor, 4 inch to 3 inch dia. 45 deg angle silicone hose, 75 mm ported and polished Ford non-production racing throttle body, 75 to 65 mm throttle body outlet to intake manifold inlet adapter, 00M12 kit, AutoMeter 5978 wideband air/fuel ratio meter
Exhaust: Stock
4.0L SOHC V6: Stock
Ignition: Champion 4401 Truck Plugs alloy electrodes with 0.056 in gap, original stock plug wires
PCM: Custom tune for engine performance and shifting by Henson Performance
Engine oil: Super Tech full synthetic 5W30, remote Mobil 1 full flow filter (M1-301), remote Amsoil bypass filter (EABP90), thermostatically controlled (215 deg F) external 6 pass cooler, Accusump
Engine coolant: 2 row radiator, 195 degree thermostat
5R55E: Mercon V ATF, remote Mobil 1 full flow filter (M1-301), radiator & dual external coolers, valve body bonded separator plate/gasket and improved solenoid bracket, reverse servo D ring gaskets

Introduction

The increase in fuel prices and the warming of the weather has prompted me to investigate ways to improve my fuel economy. My 2000 Explorer Sport got 14.5 mpg on my last tank of gas which was all city driving. This compares with 19.5 mpg (also totally city) for our stock 2006 Toyota Highlander with a V6 engine. Even though the 2011/2012 winter has been fairly mild here in Greenville, SC I suspect my fuel economy has suffered due to running the engine while scraping ice off the windows. That's one disadvantage of keeping the vehicle outside.

Just prior to my latest tank fill I completed my third and final engine flush and oil and filter change. Hopefully, most of the sludge has been removed from the engine so I am again using full synthetic oil. The synthetic engine oil should improve my fuel economy on the next tank. I have full synthetic oil in the rear axle (2WD vehicle). I could switch from Mercon V to full synthetic in the 5R55E but I doubt that the cost is warranted at this time.

One thing I realized is the A/C compressor engages when defrost is selected. I understand that A/C helps clear the windshield by removing moisture in the air but I'm going to investigate a method to disable the A/C. As I recall my 1950 and 1956 Oldsmobiles had no A/C and the defroster seemed to work OK.

 

[wood1]

Aldive did this with pretty good success with his SOHC. You must have seen his gas mileage thread?

Miss that guy...

 

[wood1]

Ah, obviously you have seen Aldive's thread... it's the only sticky in this forum. Hope your's is as successful.

 

[DaExplorer]

One thing I realized is the A/C compressor engages when defrost is selected. I understand that A/C helps clear the windshield by removing moisture in the air but I'm going to investigate a method to disable the A/C. As I recall my 1950 and 1956 Oldsmobiles had no A/C and the defroster seemed to work OK.

Try unplugging the ac low pressure switch.

 

[Keeper0311]

Could take the back seats out.

 

[2000StreetRod]

Function selector switch

Try unplugging the ac low pressure switch.

As I recall the Function Selector Switch is a two gang single pole 8 position electrical switch with an integrated vacuum switch that would be difficult to modify. I want to be able to control activation of the A/C compressor while in the driver seat. The electrical wiring diagram indicates that battery voltage from Fuse 10 (7.5 amps) in the Central Junction Box passes thru one gang of the Function Selector Switch to the PCM (Pin 41) when the A/C is enabled (Max A/C, Norm A/C, Panel/Floor, Def/Flr & Defrost). It should not be difficult to insert a switch in series with the path (purple wire) to open the circuit. Since the PCM has no way of detecting the Function Selector Switch position, opening the path should not result in a diagnostic trouble code. I can mount the switch in an inconspicuous but easily accessible location. Possibly next to my Accusump control switch.

 

[2000StreetRod]

Techron

Advance Auto had a two-for-the-cost-of-one special today on the 20 ounce size of Techron fuel injector cleaner. That's the only kind of fuel injector cleaner I've ever used so I purchased two bottles. I have a full fuel tank in the Highlander so I'll put a bottle in it tomorrow. My Sport's fuel tank is only half full and I want to see if the full synthetic engine oil makes a difference on the fuel economy so I'll put the Techron in after my next fill up.

 

[2000StreetRod]

VIS yes or no?

The 1997 and 1998 SOHC V6 came with a variable intake system (VIS). The length of the intake runners in the upper intake manifold are PCM controlled. Above 3,000 rpm the PCM energizes a vacuum solenoid that activates a vacuum motor that moves a lever arm. I wonder if the intake runners below 3,000 rpm result in more fuel efficiency than the fixed length runners in my 2000 Sport.

The 1999 and later PCM does not support VIS. The 1997/1998 PCM pin that was dedicated to the VIS solenoid is dedicated to detecting the fuel cap is left open on the later PCMs. I'm considering obtaining and installing a VIS if there might be both fuel economy and performance gains. I think the fuel lines are in the rear on the 1997/1998 but are in the front on the 1999 and later. That should not be much of a problem. The 1997/1998 uses a return fuel system and my 2000 uses a returnless system which I would want to retain. I could purchase a 3,000 rpm switch module to activate the VIS solenoid. Al Franklin achieved excellent fuel economy on his 1999 model. I wonder if the VIS engines have more potential.

 

[2000StreetRod]

Goal - 20 mpg city

I've decided to pursue a goal of exceeding 20 mpg for city driving. My wife and I rarely leave town and when we do we drive the 2006 Highlander. Since it got 19.5 mpg on its last tank for all city driving that includes Meals-on-Wheels deliveries when the engine is left running I should be able to achieve that with my Sport. I suspect that part of my increase in fuel consumption is due to an increase in fuel ethanol content. When I first purchased my Sport I was buying ethanol free unleaded regular. It is no longer readily available. I've been rereading Al Franklin's fuel economy quest thread and have already performed some of the modifications he did for highway driving.

I have attempted to reduce intake airflow resistance in several ways. I replaced the stock 65 mm throttle body with a ported and polished 75 mm Ford racing throttle body.

I replaced the somewhat restrictive "silencer" gasket with a thick taper gasket that matches the throttle body 75 mm output port to the intake manifold 65 mm inlet port.

I replaced the stock 55 mm MAF sensor and air filter with a Lightning 90 mm MAF sensor and Spectre cone filter.

Then I got James Henson to generate a custom tune to make it all play together. I should point out that the tune was mainly for performance and not fuel economy.

Part of my intake modification strategy was to increase intake airspeed as air traveled from the air filter to the intake manifold. I hoped this might result in a minor ram effect. I don't know whether or not the idea was successful and can't think of any way to test it. I'm not satisfied with the cone filter drawing air from the engine compartment - especially during summer city driving. I plan to purchase an Amsoil drop in filter and fabricate a custom air filter enclosure to mate with the 90 mm MAF sensor adapter.

 

[2000StreetRod]

Champion Truck Plugs

When I purchased my Sport in May 2009 the previous owner had just replaced the spark plugs with new Autolite plugs. Its been almost three years but less than 7,000 miles since then but new plugs may improve my fuel economy. I did some reading on the internet and became interested in the Champion Truck Plug that used to have copper on both electrodes. The only ones I found available now specify an alloy (?) on both electrodes but are still considered heavy duty. I ordered six 4401 plugs ($2.28 each) from Rock Auto which are obsolete and replaced by 3401 single platinum. I don't want to install single element electrode plugs on my stock waste spark system since the center electrode wears on one bank and the outer electrode wears on the other bank. I speculate that double platinum and double irridium plugs may not last very long due to the tiny diameter of the center electrode. I also think they are over priced.

The weather here has been mild and I have not had to defrost the windows prior to driving on the current tank of gas. It will be interesting to see if that and the synthetic engine oil will improve my city mpg. On the next tank I will burn 20 Ounces on Techron and I'll probably install the new plugs for following tank full.

 

[2000StreetRod]

Start up miss

This morning when I started my Sport the idle was unsteady for about 20 seconds as I backed out of the driveway. I haven't driven it for several days and we've had some rain which may have contributed to the problem. However, I suspect new plugs are warranted. Surprisingly, six new Champion Truck Plugs arrived from Rock Auto this afternoon.

According to the literature:
They have a copper cored center electrode that has a spark area 20% greater than a conventional plug for longer life and heavy duty performance.
The insulator upper is black glazed zirconium encased ceramic that offers 40% more strength providing durability under rough driving conditions.
They have a semi-conductor suppressor to eliminate RF interference.
The shell is triple coated with special anti-seizing coating.
The copper cored ground electrode dissipates heat at a rate ten times greater than a conventional plug to prevent pre-ignition under high load conditions.

They look good to me and I am very interested in the reduced detonation claim since lugging the engine more should result in better city driving fuel economy.

The forum consensus appears to be that the stock ignition system is more than adequate. However, Al Franklin (aldive) reported improved idle and slightly better highway fuel economy when he installed a Screamin Deamon coil pack and gapped the spark plugs at 0.065 inches. I am definitely not a fan of Ford's waste spark ignition system. The gap of the plug firing on the exhaust stroke reduces the total current flowing thru the coil high voltage secondary circuit by increasing the total resistance of the path. Also, the voltage required to bridge the exhaust stroke plug gap reduces the voltage available at the compression stroke plug gap. Unfortunately, since there are only three trigger wires (paths to ground in the low voltage primary circuit) from the PCM it is difficult to convert to a single spark ignition system. The stock coil pack is reported to have a secondary voltage of 40KV. I suspect the Sceamin Deamon has a different transformer ratio resulting in a higher secondary voltage but it still must fire both plugs.

I have a used stock coil pack and will investigate the idea of only firing one plug per coil section to increase secondary voltage and current. I think I could mount the second coil pack directly above the stock one. If I move #1, #2 and #3 wires from the lower coil pack to the upper coil pack, and short all other plug wire terminals on both coil packs to ground, then only one plug would be fired by each section of the coil packs. I'd also have to splice a pigtail and connector to the PCM to coil pack wires for the upper coil pack. It would still be a waste spark ignition system but implemented with two coil packs. My concerns are that the PCM may not be able to simultaneously short two primary circuits and if it can it may overheat.

 

[Black Dynomite]

I recall from Aldive's thread that he thought the best bang for buck when chasing improved fuel economy (aside from driving style), was the efan. I recently did UDPs and an efan and I think he may have been correct. While I havent taken any measurements yet, I am sure I have netted some decent gains. The engine revs more freely and going by the message center and scanguage, I think the fuel economy has improved by a noticeable margin. I've only done around town driving but due to the flat terrain and mild climate, my fan never comes on anymore (unless I use the AC). I have a 195 stat and the temp seems to stabilize at 197-200 when I'm out running errands. In the coming weeks I should be able to accurately track my fuel economy, I'm hoping for a decent gain.

 

[wood1]

I thought I read that Al liked the underdrive pulley's as the best bang for the buck? Could be wrong...

 

[2000StreetRod]

best results

Great mileage is the result of driving techniques and the synergistic results of all the mods.

If I were starting from scratch now, I would start with the following mods:

(1) underdrive pulleys
(2) electric fan
(3) full synthetic fluids everywhere
(4) synthetic wheel bearing grease
(5) free flowing air intake ( such as a Mac )
(6) custom cat back exhaust with 2 1/2" piping
(7) custom computer tune designed for max mileage

Al eventually generated his own custom tunes for fuel economy using the Advantage III Pro Racer software.

Some of the changes are listed below:

Changed the time delay to go open loop.
Upped the EGR flow quite a lot.
The open loop throttle position was raised.
The idle was lowered.
The basic fuel table was modified significiently.

and some other tricks

He was fairly secretive about specific tune modifications. I suspect he may have increased the closed loop Air/Fuel ratio above 14.7:1 but he would not confirm it. My Bosch Fuel Injection Management manual states that best fuel economy occurs at 15.4:1 but the nitrous oxide emissions increase rapidly above 14.7:1 due to the three way catalytic converter design. I think modifying the A/F ratio is just as effective (and less expensive and dangerous) as HHO which Al eventually experimented with. I may purchase a Pro Racer software package in the future.

 

[2000StreetRod]

engine oil temperature

I suspect I made a mistake when I routed my engine oil thru the radiator oil cooler instead of the ATF. I have two external stock type ATF coolers and one external engine oil cooler.

I assumed that the radiator was warming the ATF in the stock implementation which would be more beneficial for the engine oil. The desired ATF temperature is 150 degrees F and the desired engine oil temperature is 180 degrees F. This winter I noticed that the ATF temperature was higher than desired and the engine oil temperature was lower than desired. The 5R55E external cooling loop is internally thermostatically controlled so excessive external cooling is not a concern. I thought that the radiator temperature may exceed 150 degrees in the summer but now I'm questioning that. I've noticed that the IAT (cone filter draws air from engine compartment after passing thru radiator) stays below 150 degrees when the vehicle is stopped. I'll try using my remote sensing thermostat to read the radiator temperature. I think my winter fuel economy has been impacted by running the engine with the oil temperature below 100 degrees. I plan to purchase an oil thermostat that bypasses the engine oil cooler when the temperature is below 165 degrees. I'll route the ATF thru the radiator oil cooler if it stays below 160 degrees. Hopefully it will since I replaced the one inch thick single row with a two inch thick double row radiator and have no overheating problems.

 

[IZwack]

Besides driving habit, best bang for the buck is weight - cauz it usually costs nothing to remove something from the vehicle. So I think you should look at getting rid of some of those coolers/filters, using a smaller battery, etc.. I ran my Explorer with a Civic's battery w/o any problems - even ran an 8k winch on it. The engine might even survive with a thinner single row radiator carrying around less coolant.

EDIT - another idea is to replace the steel stock spare wheel with a lighter one. I think the stock tear drop wheels are lighter. And if you still have the transfer case shield that runs across both frame rails, I'd get rid of that too.

 

[2000StreetRod]

weight reduction

Besides driving habit, best bang for the buck is weight - cauz it usually costs nothing to remove something from the vehicle. So I think you should look at getting rid of some of those coolers/filters, using a smaller battery, etc.. I ran my Explorer with a Civic's battery w/o any problems - even ran an 8k winch on it. The engine might even survive with a thinner single row radiator carrying around less coolant.

EDIT - another idea is to replace the steel stock spare wheel with a lighter one. I think the stock tear drop wheels are lighter. And if you still have the transfer case shield that runs across both frame rails, I'd get rid of that too.

I agree that weight reduction will result in a significant improvement in fuel economy - especially for city and hilly driving. That's one of the reasons I removed my side steps. Having 2WD I don't have the added weight associated with a transfer case, front axle and driveshaft. As far as the coolers/filters I prefer to increase the engine/transmission life over a slight increase in fuel economy. The same goes for the double row radiator. I was disappointed that the mono-leaf to multi-leaf spring replacement resulted in a weight gain but I prefer the multi-leaf springs. Since I only drive in the city or on short trips I could replacement the stock fuel tank with a 5 gallon one. Or I could keep my tank less than a quarter full but that would make it difficult to calculate gas mileage. The lower weight wheels may be worth investigating but I like the looks of the current ones - probably something to do with my age/generation.

 

[2000StreetRod]

Significant gain

My fuel economy improved significantly on the last tank.
214.1 miles/12.957 gals = 16.5 mpg

The changes from the previous tank full (14.5 mpg):
No aggressive driving
No engine idling while deicing windows
Full synthetic engine oil

I filled up this morning at the same station, same pump, facing the same direction and automatic pump shutoff.

To prevent a potential major fuel economy drop I did something I should have done immediately after purchasing my Sport, I bought a locking fuel cap.

Since it was unusually warm weather (75 degrees) and the Sport was well warmed up after numerous errands I took some measurements with my remote sensing thermometer after shutting off the engine:

ATF remote oil filter exterior - 116 deg F
Engine oil remote bypass filter exterior - 137 deg F
Engine oil remote full flow filter exterior - 133 deg F
Aft radiator core (upper, center) - 150 deg F
Radiator side (internal cooler area) - 133 deg F

The above are inconsistent with what my A pillar pod temperature gauge displayed (ATF - 165 deg F, eng oil 125 deg F). The sensors for the gauge are located at the remote filter inlets. I've suspected since the installation that the engine oil reading was incorrect but I think I've confirmed the ATF reading with a PCM datalog. Further investigation is needed before I install an engine oil cooler thermostat control.

After my fillup I added 20 ounces of Techron to the tank.

 

[Joe Dirt]

This is a great thread Dale... Nice work. I like how you're actually sharing what you're doing, and not keeping it a national security-esque secret.

 

[2000StreetRod]

radiator oil cooler

Al Franklin's ATF flowed thru three coolers: an external aftermarket ATF cooler, a stock ATF cooler and the radiator internal ATF cooler. He also added a fin cooler around his remote ATF filter. His external ATF temperature was around 135 degrees F when the outside air temperature was around 95 degrees F. In order for the ATF to be that low his 5R55E must have had the modification to keep the external cooling path always open.

I have two stock ATF coolers in parallel after the remote ATF filter and my radiator internal cooler is being used to cool engine oil. I reviewed some past datalogs and found that my external ATF temperature increased to 200 degrees F when the inlet air temperature was only 40 degrees F. The 5R55E internal thermostat is designed to open the external cooling loop when the torque converter termperature reaches 150 degrees F. I suspect the internal thermostat is working because the external temperature increases with time but my external cooling capacity is inadequate.

My radiator has no trouble maintaining the thermostatically controlled engine coolant temperature of 195 degrees F. That means that the radiator temperature is significantly less than 195 degrees. I plan to return to the stock configuration of the ATF passing thru the radiator after the external coolers. The goal is to keep the internal ATF temperature (as reported by the PCM) between 150 and 180 or less degrees.

I will add an oil thermostatic switch between the engine oil remote filters and the external cooler that begins to open the path to the oil cooler at about 165 degrees F and is full open at 180 degrees F. Cold engine oil is less effective and less fuel efficient than warm oil.