I have been wondering which is better for overall fuel economy.
Is it better to accelerate briskly (not flooring it) up to the speed limit, or target speed??

OR

Accelerate slowly with little boost, but taking much longer to reach your target speed.

So, less throttle over longer timespan, or more throttle for much shorter time?

 

Not sure, but you would think that for people with autos that the quicker that the t/c locks up the better. However, you should probably try to keep the boost down too. I;m kinda goin in circles, but there is probably an efficient middle line.

phil

 

Same as any other internal combustion engine. The quicker you accelerate, the lower the fuel efficiency will be for that period of time. Best to accel slowly, low boost/load for max fuel econ.
With that said, you won't really notice any difference if you only acclerate once getting on the freeway and then drive at a constant speed for 400mi. You'll notice it alot more in stop and go traffic where more of your total fuel consumption is spent on accelerating.

 

In town traffic is more the point. So your voting a slower acceleration over a much longer time is better than a quicker acceleration over much shorter time?

 

Counter to what we've been taught, gasser fuel economy improves with brisk (not full throttle) acceleration up to cruising speed - this is because pumping losses are reduced with wider throttle plate openings. This has been discussed in several of the auto mags in the technical sections. That's the same reason gassers use ultra-tall overdrives and/or rear axle ratios - to maximize economy by cruising at larger throttle openings (reduced pumping losses) and lower RPM (reduced frictional losses).

Now, since a diesel doesn't have a throttle plate, it won't benefit from this technique.

Rusty

 

That's true, Rusty - and a diesel will definitely get better fuel economy by keeping boost under 10psi

 

Don't know if I am doing it right or wrong, but i get the better MPG using cruise control.
If I don't have my speed set, I use the accerate button.
With the speed set, like gettin back on a freeway, I hit resume, and let the computer figger it out, Works well for me.

 

Inner city driving the trick with a heavy vehicle is to keep it rolling- so accelerating slowly and letting a gap open up and then letting it roll will net you a lower consumption.
The CTD is most fuel efficient near it's rated HP, but since you won't consume that many HP-hours if you accelerate slowly and let it roll the worse efficiency is going to be more than set off by the lower energy consumption.

The cruise control being more efficient comes from the accelerator being moved less than going manual because the ECM won't "tip in" that often to get the turbo up to boost.

Just my 2c

AlpineRAM

 

I dont know about where you guys live, but here, if you let a gap open up from accelerating slowly that gap will be filled with cars cutting in front of you. Some of the worst drivers in the world live right here. They brought their island ways of driving with them. They sucked there, and they suck even worse here in heavy traffic.

 

Yeah I think we have somethin like that where I live too

 

It's safer to drive like Mario Andretti in the draft rather than leave "1 alligator, 2 alligator" between vehicles like we should, so all the bonehead drivers won't try to force their way in front of you and the next vehicle.

 

Most of them are oblivious to the fact that a 7500+# truck will simply demolish their little Honduh if we cant stop. Even the gigantic wing and fartcan wont stop that from happening!

 

Too true. Some older guy in a late 80s Accord cut straight into a roundabout (yes they do have these in America) without even looking to see if anyone was coming around it from his left. Fortunately I was paying attention and slowed down to prevent t-boning him. He would never have known I was there had I not laid on the horn. T-boning him would have put my front bumper/grill into his driver side windows... not too smart.

I've actually heard people say that these trucks and SUVs are terrible because if you get hit by one you hardly stand a chance. Trucks and SUVs are not the problem people, it's the crap that you are driving.

Another thing that I love about driving my truck is that I don't have to watch my rear view mirror as much in stop and go traffic to make sure I'm not going to be rear ended. If you rear end me, chances are you're going underneath my truck, and I won't have a scratch. When the tow truck gets there I'll put it in 4X4 and drive off of your hood.

 

I took part in a national who can get the best mpgs competition while in collage during the '70s. This is what we were taught and it definitely proved to be true. Don't know how it relates to diesels though but it's the way I drive now and average 22-24 mpgs.

 

Thats how Im leaning also. I think its better to use that abundant low end torque to get the truck moving then back off the throttle. Oh course i dont know for sure, that the reason for this thread.