Miles per gallon - how much?
06-12-2006, 10:15 PM
#1
Thread Starter
Join Date: May 2006
Posts: 7
Miles per gallon - how much?
I own a 1968 Mustang 289 4 barrel, dual exhaust flowmaster. How many miles per gallon should i be able to get with a well tuned engine,and what mods or adjustments have you members done to improve your mileage?
06-12-2006, 10:32 PM
#3
2nd Gear Member
Join Date: Nov 2005
Location:
Posts: 182
RE: Miles per gallon - how much?
I have a 67, well built motor, edelbrock 500CFM Performer, performer intake. The performer comes jetted VERY rich. Out of the box, I used to get about 11MPG, and the motor would smoke every time I started it after sitting a couple days. I ended up stepping up the metering rods about FIVE sizes, until it just started to stutter in the mid-range. Then I chucked the rods up in my drill press with some fine emery cloth, and just took them down a couple tenths at a time until the mid range problem went away.
The best part of this little exercise, is that the power went UP and SO DID THE MILEAGE!! The blue smoke problem went away too. Mileage is now about 18 - 20 MPG depending on cruise speed. The C4 is not 1:1 in 3rd gear, and the motor tachs about 2800 at 65MPH, which is not exactly "economy" gearing. If you have an AOD, you might expect 25 MPG if the carb is dialed in properly.
Don't be afraid to tinker. Lean it out, and test drive it. Nothing heavy, just see if it runs reliable. If it's still running good, and plugs are not real LIGHT GREY, lean it out some more. When it's "right" you'll be close to the "ideal" air/fuel mixture, which is about 14:1. Plug color should be about like the color of the palm of your hand on the insulator part of the plug. This is the zone where your engine will make the most efficient use of the fuel (most power also!!)
It may take a while to find the "just right" spot, but just keep trying. When you find it, you'll know it!!
The best part of this little exercise, is that the power went UP and SO DID THE MILEAGE!! The blue smoke problem went away too. Mileage is now about 18 - 20 MPG depending on cruise speed. The C4 is not 1:1 in 3rd gear, and the motor tachs about 2800 at 65MPH, which is not exactly "economy" gearing. If you have an AOD, you might expect 25 MPG if the carb is dialed in properly.
Don't be afraid to tinker. Lean it out, and test drive it. Nothing heavy, just see if it runs reliable. If it's still running good, and plugs are not real LIGHT GREY, lean it out some more. When it's "right" you'll be close to the "ideal" air/fuel mixture, which is about 14:1. Plug color should be about like the color of the palm of your hand on the insulator part of the plug. This is the zone where your engine will make the most efficient use of the fuel (most power also!!)
It may take a while to find the "just right" spot, but just keep trying. When you find it, you'll know it!!
06-12-2006, 10:37 PM
#5
2nd Gear Member
Join Date: Jun 2005
Location: San Diego
Posts: 325
RE: Miles per gallon - how much?
i get about 14 in the city and somewhere around 19 on the highway with 100k miles on my 289 / C4 combo.
I have long tube headers, dual magnaflows, K&N filter, smog pump removed, 2.79:1 gears, and 235's on 17" wheels.
I have long tube headers, dual magnaflows, K&N filter, smog pump removed, 2.79:1 gears, and 235's on 17" wheels.
06-12-2006, 10:38 PM
#6
5th Gear Member
Join Date: May 2005
Location:
Posts: 2,445
RE: Miles per gallon - how much?
Based on your signature line, I'd say 10-12 mpg. Best adjustment would be between brain and foot. Another really good one is between eye and speedometer.
Shell did a whole group of comercials on getting better mileage. It was really good. Unfortunately not many people paid attention. Ford did a class for people who bought the Hybrid Escape. The results of changing ones driving habits significantly improved mileage, even with a Hybrid!
Truth told, there are more variables like rear end ratio, type of driving, altitude, topography, etc. I'd think 18 mpg would be a good target goal for combined, if you are running anything less than 3.50 gears. If you hit 18, shoot for 20.
I'm getting 22 combined with my '04 4Runner, but I drive it like an old man. I've gotten as bad as 17 by not paying attention to my driving habits...but it was a lot of fun!
Good luck,
Shell did a whole group of comercials on getting better mileage. It was really good. Unfortunately not many people paid attention. Ford did a class for people who bought the Hybrid Escape. The results of changing ones driving habits significantly improved mileage, even with a Hybrid!
Truth told, there are more variables like rear end ratio, type of driving, altitude, topography, etc. I'd think 18 mpg would be a good target goal for combined, if you are running anything less than 3.50 gears. If you hit 18, shoot for 20.
I'm getting 22 combined with my '04 4Runner, but I drive it like an old man. I've gotten as bad as 17 by not paying attention to my driving habits...but it was a lot of fun!
Good luck,
06-12-2006, 10:40 PM
#7
2nd Gear Member
Join Date: Jun 2005
Location: San Diego
Posts: 325
RE: Miles per gallon - how much?
ORIGINAL: JBradley500
i think the best i could do to improve gas mileage is not to drive anymore...efficiency of fuel was not an issue back in the good ol' days.
i think the best i could do to improve gas mileage is not to drive anymore...efficiency of fuel was not an issue back in the good ol' days.
i just picked up a yamaha V-Star last week that has become my daily driver. 50 mpg [sm=goodidea.gif]
The fuel savings more than pay for it's insurance [8D]
06-13-2006, 12:37 AM
#9
5th Gear Member
Join Date: Mar 2005
Location: Marquette Mi
Posts: 3,566
RE: Miles per gallon - how much?
Its true about leaning the carb, finding power and improving mileage. Even a large V8 can get decent mileage if it is geared, cammed, and has the right intake and exhaust on it, then driven decently. 22mpg from a 7.5L with a carb in a 4000lb vehicle can be done.
The stock 60s era cams arent so great for mileage, technology has come a long way in the last 30-40 years, same with intakes, and exhaust. If you want better mileage make the engine not work so hard. Get the right cam so it makes torque down low, use a tall gear like a 3.00 or 2.79 to keep the revs low. Covering more distance for each revolution is the idea, if it burns the same fuel at 2500 rpm as it does at 1700 rpm then gear it so it is at cruise speed between those points.
A single plane intake on a small engine isnt going to get good mileage, at low rpm the fuel will puddle in the intake the puddle will grow untill it runs into a cylinder creating a rich condition in that one. Dual planes dont do that, the velocity stays up in the intake and the fuel wont fall out of the airstream. Carb size is up for debate, it will only flow as much air as is needed and you just need to jet it so the air/fuel ratio is right. Going with jets that are too small will hurt power, economy, and overheat the engine, while causing severe driveability issues.
Lean is power, but too lean hurts parts. Power means efficiency. Get the max power from your combination and gear it so it runs in the torque rich part of the curve, and you will get good mileage. More power down low means the car moves easier taking less throttle to get to the desired speed.
When building an engine there are things you can do to improve mileage. Shorter pistons skirts can reduce drag and weight, lighter pins also decrease drag, getting the engine balanced will make a difference. Roller cams and full roller rockers will also benefit reducing parasitic drag. Add in thermal barrier and friction reduction coatings and you can see marked improvements.
Making the car lighter and more aerodynamic has a large impact as well. Cant do much about your 67 Mustangs aero qualities? Sure you can. Keeping air from under the car helps, lowering can make an improvement in aero, so does keeping air out of dead spaces like behind the headlights. Waxing the car helps a little, if you have decent paint keep it clean and waxed.
Alignments, tire pressures, wheel bearings, and brakes all have to be right, check your tires. Go to the max pressure they are rated for. the 17" Goodyears on my daily driver are rated at 45psi, so they are at 45psi. When I run them at 32 like the tire shop had them I cant get over 25mpg, when they are maxed I get 28-31mpg.
Repack your wheel bearings yearly. Pull the front rotor or hub off and repack them bearings. Make sure the rear bearings arent dragging either. While you are there check the brakes, if they are draging you are fighting them as well as rolling resistance, wind resistance, and the natural tendencey of a body at rest to stay at rest. If you can push the car easily up a slight hill by yourself, you arent wasting much in the suspension and drivetrain.
Every little bit helps.
The stock 60s era cams arent so great for mileage, technology has come a long way in the last 30-40 years, same with intakes, and exhaust. If you want better mileage make the engine not work so hard. Get the right cam so it makes torque down low, use a tall gear like a 3.00 or 2.79 to keep the revs low. Covering more distance for each revolution is the idea, if it burns the same fuel at 2500 rpm as it does at 1700 rpm then gear it so it is at cruise speed between those points.
A single plane intake on a small engine isnt going to get good mileage, at low rpm the fuel will puddle in the intake the puddle will grow untill it runs into a cylinder creating a rich condition in that one. Dual planes dont do that, the velocity stays up in the intake and the fuel wont fall out of the airstream. Carb size is up for debate, it will only flow as much air as is needed and you just need to jet it so the air/fuel ratio is right. Going with jets that are too small will hurt power, economy, and overheat the engine, while causing severe driveability issues.
Lean is power, but too lean hurts parts. Power means efficiency. Get the max power from your combination and gear it so it runs in the torque rich part of the curve, and you will get good mileage. More power down low means the car moves easier taking less throttle to get to the desired speed.
When building an engine there are things you can do to improve mileage. Shorter pistons skirts can reduce drag and weight, lighter pins also decrease drag, getting the engine balanced will make a difference. Roller cams and full roller rockers will also benefit reducing parasitic drag. Add in thermal barrier and friction reduction coatings and you can see marked improvements.
Making the car lighter and more aerodynamic has a large impact as well. Cant do much about your 67 Mustangs aero qualities? Sure you can. Keeping air from under the car helps, lowering can make an improvement in aero, so does keeping air out of dead spaces like behind the headlights. Waxing the car helps a little, if you have decent paint keep it clean and waxed.
Alignments, tire pressures, wheel bearings, and brakes all have to be right, check your tires. Go to the max pressure they are rated for. the 17" Goodyears on my daily driver are rated at 45psi, so they are at 45psi. When I run them at 32 like the tire shop had them I cant get over 25mpg, when they are maxed I get 28-31mpg.
Repack your wheel bearings yearly. Pull the front rotor or hub off and repack them bearings. Make sure the rear bearings arent dragging either. While you are there check the brakes, if they are draging you are fighting them as well as rolling resistance, wind resistance, and the natural tendencey of a body at rest to stay at rest. If you can push the car easily up a slight hill by yourself, you arent wasting much in the suspension and drivetrain.
Every little bit helps.