Lugging the engine

Stay above 2000 rpms. Heck, stay between 2500-4000 whenever it's operating temp, and 2000-3500 before it's operating temp.

Below 2000 rpms the engine is running inefficiently (besides the added vibration) and will produce more combustion byproducts over time.

Some people think lower RPM's mean better fuel mileage. This is not always the case.

If you have the car in 3rd at 3,000 rpm's at 1/4 throttle you're using less gas than if you were to upshift to 4th and drive at 2,000 rpm's at 1/3 throttle. The reason is because the engine may be rotating slower, but you are also applying more throttle to maintain the same speed, increasing the amount of air the engine consumes, which increases the amount of fuel the engine consumes. The lower the vacuum the less gas required to create combustion.

This is the reason why cars had (Have) Overdrive transmissions. When driving around town, leave the car in "Drive" (3rd gear) to save gas. When driving over 45-50 MPH shift to Overdrive (4th gear) to lower the RPMs. Our cars don't have overdrive transmissions. They have locking torque converters instead, which allow the torque converter to slip below 45 MPH, keeping the RPM's slightly higher when on the gas, then lock up maintaining a steady lower RPM above 45 MPH.

Now, if you were to drive the car in 3rd gear at 5,000 RPM's at 60% throttle, you would be using more gas than if you were in 5th gear at 2,500 RPM at 1/4 throttle. It is for this reason I wanted to install a vacuum guage on my F150 4 speed stickshift for a while. By keeping an eye on the vacuum you can see how much air the engine consumes. Low RPM's with high vacuum means more fuel is required. Higher RPM's with lower vacuum means less gas. There is a fine line between gas saving RPM's and gas wasting RPM's, which is why I wanted the guage. The truck is a 4.9L carb'd straight six, and guzzles $10 worth of gas a day.

I know this may sound ignorant, but what is the point in having a LGT if you are not going to be taking advantage of the turbo? lol..

I like the way you think. lol

Stay above 2000 rpms. Heck, stay between 2500-4000 whenever it's operating temp, and 2000-3500 before it's operating temp.

 

Below 2000 rpms the engine is running inefficiently (besides the added vibration) and will produce more combustion byproducts over time.

Hmmm didnt know that, I keep my LGT between 1500-2000 rpms, and shift at 3k or whenever the green flashing light tells me to.

Why would "lugging" an engine be different for small displacement, vs. large?

Moreover, the whole 1K rpm in 5th, vs 1.5K in 4th, vs 2.2K in 3rd at roughly 25 mph...

Gas mileage depends on the load. At very low load, 5th gear will get the best

Why would "lugging" an engine be different for small displacement, vs. large?

Gas mileage depends on the load. At very low load, 5th gear will get the best.

 

 

Small displacement engines "generally" rev higher and produce less torque at low rpms than a large engine. Don't think I'd have any concern for running a 6.2 liter engine under 2k and would be harder to lugg don't you think?

So its ok to operate our LGT engines under 2K if no load? Would the load be greater by virtue of running at 2k as apposed to 3 or 4k?

Platinum_racing how is that inline six holding up? I just got rid of my '87 3/4 ton 300 inline six w/4spd man that had 200k hard city miles on it. I thought the fuel injected model was slow how does the single barrel do in city traffic?

For 1986 the carb was horrible. It doesn't run bad, but it throws the Emission light on if the wind blows too hard. It was the last year 300 that still used the carb, so as a result it was kind of a hybrid/electronic carb. It has all these wires going into it everywhere, with random solenoids all over the place supposedly to make it more efficient. It runs good, and has a lot of low end grunt though. The only problem is the electronics that make the carb work it's magic. I wanted to get a carb off a 1978, since those don't have any form of electronics (Except electric choke). It bolts right up and I can simply leave all the wires hanging, just gotta pull the Emission bulb out of the dashboard. It sounds better with the carb too. Nice glub glub glub and decent popping when decelerating. I straightpiped it and it's still not very loud, but it's got an excellent tone. In street driving it's not too bad actually, as you already know you can just let out the clutch without giving it gas to maneuver in traffic. It's not as powerful as the decked out 1990 Dodge 1-Ton Cummins Turbo Diesel I used to have, but it serves it's purpose. I raced a 1996 Bronco w/ a 302 and it was dead even all the way. The F150 is way lighter than the F250, especially seeing as how mine is a short frame 6' stepside bed. I think mine has 3:08's in the rear., which helps. It will bury the needle if you want it to, that's for sure.....

I've also got an MSD coil, 14" Edelbrock filter, new fuel pump, new cap/rotor/wires/plugs, Grant steering wheel, Pioneer truck boxes, JVC deck, APC fog lights, 2" rear drop shackles, and a SunPro tach on the column. Having 4 on the floor makes this truck much better than the 3 speed auto. The frame cracked a while ago however, so I bought a new rear frame segment from an identical 86' Stepside in the junkyard, but never got it together. I got all the rust off the new rear frame, welded new supports for the bed mounts, and cleaned up the diff and suspension and painted it all black. Turns out my best friend has an 86 300 F150 4WD Long Bed he's willing to part with, so I was planning on taking the motor off mine, stripping all the performance parts off and swapping them over to the new truck, then rebuilding the other 300 top to bottom and make it a real screamer. When it's done I'll put it in the 4WD truck. The only problem is the new truck is an automatic. I want to keep my 4 speed transmission, but I don't think the transfer case off the 4WD will fit.

http://www.cardomain.com/ride/2957859

This was before I did some bodywork to the truck.

For 1986 the carb was horrible. It doesn't run bad, but it throws the Emission light on if the wind blows too hard. It was the last year 300 that still used the carb, so as a result it was kind of a hybrid/electronic carb. It has all these wires going into it everywhere, with random solenoids all over the place supposedly to make it more efficient. It runs good, and has a lot of low end grunt though. The only problem is the electronics that make the carb work it's magic. I wanted to get a carb off a 1978, since those don't have any form of electronics (Except electric choke). It bolts right up and I can simply leave all the wires hanging, just gotta pull the Emission bulb out of the dashboard. It sounds better with the carb too. Nice glub glub glub and decent popping when decelerating. I straightpiped it and it's still not very loud, but it's got an excellent tone. In street driving it's not too bad actually, as you already know you can just let out the clutch without giving it gas to maneuver in traffic. It's not as powerful as the decked out 1990 Dodge 1-Ton Cummins Turbo Diesel I used to have, but it serves it's purpose. I raced a 1996 Bronco w/ a 302 and it was dead even all the way. The F150 is way lighter than the F250, especially seeing as how mine is a short frame 6' stepside bed. I think mine has 3:08's in the rear., which helps. It will bury the needle if you want it to, that's for sure.....

 

I've also got an MSD coil, 14" Edelbrock filter, new fuel pump, new cap/rotor/wires/plugs, Grant steering wheel, Pioneer truck boxes, JVC deck, APC fog lights, 2" rear drop shackles, and a SunPro tach on the column. Having 4 on the floor makes this truck much better than the 3 speed auto. The frame cracked a while ago however, so I bought a new rear frame segment from an identical 86' Stepside in the junkyard, but never got it together. I got all the rust off the new rear frame, welded new supports for the bed mounts, and cleaned up the diff and suspension and painted it all black. Turns out my best friend has an 86 300 F150 4WD Long Bed he's willing to part with, so I was planning on taking the motor off mine, stripping all the performance parts off and swapping them over to the new truck, then rebuilding the other 300 top to bottom and make it a real screamer. When it's done I'll put it in the 4WD truck. The only problem is the new truck is an automatic. I want to keep my 4 speed transmission, but I don't think the transfer case off the 4WD will fit.

 

http://www.cardomain.com/ride/2957859

 

This was before I did some bodywork to the truck.

For 1986 the carb was horrible. It doesn't run bad, but it throws the Emission light on if the wind blows too hard. It was the last year 300 that still used the carb, so as a result it was kind of a hybrid/electronic carb. It has all these wires going into it everywhere, with random solenoids all over the place supposedly to make it more efficient. It runs good, and has a lot of low end grunt though. The only problem is the electronics that make the carb work it's magic. I wanted to get a carb off a 1978, since those don't have any form of electronics (Except electric choke). It bolts right up and I can simply leave all the wires hanging, just gotta pull the Emission bulb out of the dashboard. It sounds better with the carb too. Nice glub glub glub and decent popping when decelerating. I straightpiped it and it's still not very loud, but it's got an excellent tone. In street driving it's not too bad actually, as you already know you can just let out the clutch without giving it gas to maneuver in traffic. It's not as powerful as the decked out 1990 Dodge 1-Ton Cummins Turbo Diesel I used to have, but it serves it's purpose. I raced a 1996 Bronco w/ a 302 and it was dead even all the way. The F150 is way lighter than the F250, especially seeing as how mine is a short frame 6' stepside bed. I think mine has 3:08's in the rear., which helps. It will bury the needle if you want it to, that's for sure.....

 

I've also got an MSD coil, 14" Edelbrock filter, new fuel pump, new cap/rotor/wires/plugs, Grant steering wheel, Pioneer truck boxes, JVC deck, APC fog lights, 2" rear drop shackles, and a SunPro tach on the column. Having 4 on the floor makes this truck much better than the 3 speed auto. The frame cracked a while ago however, so I bought a new rear frame segment from an identical 86' Stepside in the junkyard, but never got it together. I got all the rust off the new rear frame, welded new supports for the bed mounts, and cleaned up the diff and suspension and painted it all black. Turns out my best friend has an 86 300 F150 4WD Long Bed he's willing to part with, so I was planning on taking the motor off mine, stripping all the performance parts off and swapping them over to the new truck, then rebuilding the other 300 top to bottom and make it a real screamer. When it's done I'll put it in the 4WD truck. The only problem is the new truck is an automatic. I want to keep my 4 speed transmission, but I don't think the transfer case off the 4WD will fit.

 

http://www.cardomain.com/ride/2957859

 

This was before I did some bodywork to the truck.

What were we talking about? Oh yeah, lugging.

Some people think lower RPM's mean better fuel mileage. This is not always the case.

 

If you have the car in 3rd at 3,000 rpm's at 1/4 throttle you're using less gas than if you were to upshift to 4th and drive at 2,000 rpm's at 1/3 throttle. The reason is because the engine may be rotating slower, but you are also applying more throttle to maintain the same speed, increasing the amount of air the engine consumes, which increases the amount of fuel the engine consumes. The lower the vacuum the less gas required to create combustion.

Not always, but almost always when cruising. There could be better combustion and less pumping loss (due to intake and valve timing) at speeds above idle, but the lower the rpm, the more pressure you extract from the combustion. You're wrong about throttle/vacuum. The more you open the throttle, the lower the vacuum and the less the pumping losses.

Not always, but almost always when cruising. There could be better combustion and less pumping loss (due to intake and valve timing) at speeds above idle, but the lower the rpm, the more pressure you extract from the combustion. You're wrong about throttle/vacuum. The more you open the throttle, the lower the vacuum and the less the pumping losses.

Exactly why the technique I read about was mentioned.

Not always, but almost always when cruising. There could be better combustion and less pumping loss (due to intake and valve timing) at speeds above idle, but the lower the rpm, the more pressure you extract from the combustion. You're wrong about throttle/vacuum. The more you open the throttle, the lower the vacuum and the less the pumping losses.

yea i was thinking about that today too. sure you open the throttle more at higher gears and it sucks in more air, but it does it at less frequency than it would in a lower gear at faster RPM. like it was mentioned before, it all depends on load. high load at low RPMs is gonna use more gas than low load at high rpms (1k in 5th vs 2.2k in 3rd).

thats one of the reasons why smaller engines are more efficient. because they run at WOT more often (in order to accelerate) they have greater volumetric efficiency (everything is OPEN) and thus burn things more efficiently. thats also why smaller engines w/ FI are almost always win in terms of efficiency.

thus, imho, accelerate quickly at to your cruising speed and then put it in 5th as soon as you can. this enables you to run at max efficiency when at high load, and then cruise using least gas at low load. i cruise around town > 40mph in 5th, but seldom accelerate in it. usually its a quick 1 > 2> double clutch > 5th for me. down to 3 if i need to accelerate/place a load on the engine.