ok so reading all you're guys fun stuff i came to one conclusion i had to post.

here's what i found on my 2000 mile trip to idaho and back to the west end of oregon.
mpg in oregon doing 65-70 on the highway 16 mpg
mpg in idaho doing 75-80 14mpg highway.
rev difference 1800 in oregon and 2200 (about) in idaho.

so about 400 rpm difference costed me 2 mpg average. (this is over two tanks in oregon each way and two in idaho each way)

oh and the torque curve for a stock 360 5.9 engine is a torque peak at 3500 rpms at 335 ft lbs and 245 hp at 4000 rpm. those are engine dyno'ed. i do believe that those numbers are for the 2001 model year or at least that's what i was looking for. granted those are ideal numbers so i doubt i'd be making over 300 and 200 at the wheels. probably something like 280ft lbs and 190hp. one of these days i'll do a pull and find out for sure to find out what is really going down.

 

the one thing that i have always been wondering is what burns more fuel.. pushing down harder on the pedal or higher rpms? i have a 5 speed and i can run it in 5th from 25mph at the lowest.. but i gotta really push on the throttle to get it to go.. the rpms are very low.. like 1100.. so its not really putting much fuel in the engine but i do have the pedal pretty much to the floor.. so anyway is it better to be easy on the gas but have the engine rev up higher or have the rpms low but be harder on throttle??

 

higher revs kill fuel mileage.. aka more fuel is being put into the engine. opening the throttle at low rpm's just allows more air to flow in. the stroke of the engine is what pulls the air in through the throttle body.

but the mass air flow sensor probably kicks the volume of fuel that is being injected in up to keep the air/fuel ratio correct. if i remember correctly i think dodge set that at 14:1 to reduce pinging.

 

This is a pretty interesting topic. I really tend to baby my truck....when driving city I rarely get up to 2000 rpm while accelerating. Thats going pretty slow....but I see what you mean how it takes such a long time to get to speed. [sm=confused06.gif]

 

Where did you see these dynos? They did not show up on my hours of searching. When you put it to the wheels (stock) its just short of 2K. I really don't know WTF you are talking about unless you are talking about a dyno from a Supercharged 408.

You don't have a carbeurator anymore. If your your max torque occurs at 1800 keep 3.55's. You cannot judge what your mpg is going to be at different gear ratios simply by driving up and down the road at different rpms. It's 14.7:1. This is a Stoichiometric formula that has nothing to do with pinging. It has to do with emissions and where your catalyst operates most efficiently. If anything, 14.7:1 is the most absolutely worst a/f ratio for pinging.

 

http://hypertech.com/get_dynochart.p...1366590&tp=pdf

i've found it elsewhere but that was the first place i found it again.

those are also wheel dyno's not engine dyno's. i've seen the engine dyno somewhere and it was 245 hp and 335 ft lbs torque. for the 2001 model year.

 

That is like no other dyno I've seen thus far even from built cars:
http://krcperformance.net/newcontent/dyno.html

I know the butt dyno is unreliable, and I also am going to have my truck dyno'd soon, but I can tell you most assuredly that my truck does not reflect any of the torque properties exhibited by Hypertech's dyno, although I sincerely wish it did. Looking at that dyno, the torque curve starts @ 230 ft/lbs. , ends @ 215 ft/lbs. , with a peak @ 280 ft/lbs. So, essentially (+/- ~30%) the torque band stays the same throughout a power band of 50 hp. @ ~1000rpm to 200hp @ ~ 4000 rpm.

 

yeah a real dyno would be nice. everything is subjective. i can't say that i believe the numbers i've seen and i can't say that i don't.

the numbers to me are just an estimate of what i might be getting. in all honestly the only way to truely know what you're engine is doing is to do a pull yourself and find out. machines may be good at building engines but they are in no means perfect there are tolerances EVERYWHERE.

list of things i want eventually...
Milling machine
Metal Lathe
Dyno
hydraulic lift
and too much land that i don't know what to do with it.... well make MUD PITS!

oh and a drag strip in my back yard.

 

In answer to the original question

"How should I accelerate if I want the best MPG?"

- the answer depends a little on whether you are accelerating from stoplight to stoplight in city driving,
or whether you are accelerating to get up to a steady speed that you intend to run at for some time,
like on an entrance ramp to an interstate highway.

Let's answer the complicated stoplight-to-stoplight City driving acceleration first:
you want to accelerate at the slowest rate that will correctly 'time' you on through the next stoplight.
Here you want to avoid using the brake later, and even worse, having to stop and idle.
Braking, stops and idling are fuel wasters and overwhelm any method of acceleration.

The question of how to accelerate up to a desired speed is much easier.
You want to accelerate up to what ever top speed
by opening the throttle up to close to
'fuel enrichment kick in'
as possible but just below where it starts,
and then you need to shift before the pistons start moving more than about 1400 feet per minute up and down in the bores.
Above 1200 feet per minute the piston rings start creating so much extra friction that fuel economy suffers.

For a 3.7/3.9/5.9 or 5.7 Dodge engine this means accelerating at about 75% throttle,
and then shifting around 2200-2600 rpm.

If you have an automatic transmission this means 'lifting your foot' around 2200-2600 rpm so that the automatic will shift to the next gear.

In one of the above posts someone says that they have seen a hot rod magazine's engine dyno that shows that at full throttle an engine gets the best fuel economy near the peak torque rpm.
Then they make a very common mistake,
and say that:
"This means that to get the best fuel economy at part-throttle I should drive around at this rpm of peak torque at WIDE OPEN THROTTLE all the time"

This is not true.
First, most of those hot rod magazine dyno graphs are of carburetor engines that stay at about the same air to fuel ratio - they don't have to worry about 'fuel enrichment' kicking in on a modern fuel injected engine.
Second, the low point BSFC (brake specific fuel consumption) on the hot rod magazine's is
NOT THE LOWEST BSFC THAT ENGINE CAN DO
if the dyno test had been re-run at 90% throttle, then 80% throttle, then 70%, etc
the lowest BSFC and best fuel economy is usually found at about
70-80% throttle and an rpm where the pistons are moving about 1000-1400 feet per minute.

If you want to see a dyno-like graph that shows this,
look at figures 1 and 2 in this .pdf file

http://www.epa.gov/otaq/presentation...02-01-2743.pdf

That average piston speed depends on the stroke of the crankshaft.
Short stroke engines can run a bit more rpm
but long stroke engines have to run slower rpm.

It can be surprising to find that 8,000 rpm very short stroke 'weed wacker' gas engine are running at the same piston speed as big stroke 392 ci V8 Hemi industrial engines powering water pumps, or even 9 foot stroke 100,000 hp/1,000,000 ft-lbs of torque K98 Man Marine diesels churning along at 98 rpm.

Another question asked above is:

If my engine is running 75% throttle at 1500 rpm when the truck is at 60 mph,
and I shift to a gear where
I am instead running 37% throttle at 3,000 rpm for the same truck speed 60 mph
what dominates how much fuel is being used
- having closed the throttle more
- or a higher engine rpm?

Answer: the engine will use more fuel at 3,000 rpm and 37% throttle.

The horsepower at a steady speed that a Ram pickup needs depends on
1. air drag
2. tire drag
3. friction losses in gears, bearings, and piston ring rubbing
4. positive pressure in the exhaust & negative pressure in the intake ("vacuum") that act against piston movement.
5. (this is tricky) how much ignition lead is having to be used because firing the sparkplug before top dead center creates a pressure that works the wrong way against the rising piston

At the same speed the air drag and tire drag is the same for Ram pickups that have the same tires and the same total weight.

At higher rpm and a more closed throtle
the friction goes up,
the vacuum 'sucks up' against the piston as it tries to go down
and more degrees of 'vacuum advance' has to be used on the ignition.
Result = worse fuel economy
and more fuel used each second.

Don't believe this?

Well, now ask yourself:

"How does the MDS work on the 2006 5.7 Hemi V8? "

The rpm stays the same when MDS kicks in,
the 4 shut off pistons are still going up & down creating the same friction,
where is the 10-20% better fuel economy Chrysler advertises coming from?
{reconsider numbers 4 & 5 above for the answer}

Then ask yourself:
how does an overdrive gear work to improve MPG in any vehicle?
{answer lies in numbers 3, 4, 5}

Then ask yourself:
why do car guys argue about whether cylinder cut-out or CVT transmissions are the better answer to quick improvement in vehicle MPG? Why is Dodge trying both MDS in the 5.7 Hemi and CVT in their small cars?

Still don't believe any of this and want a 'Real World' demonstration?

Go drive a Nissan Murano with a CVT transmission.
This vehicle (or Dodge Caliber/Nitro) has a JATCO built continuously variable transmission that the engine computer can set to any ratio.

At what rpm does the engine stay at as you accelerate at part throttle in 'economy' mode?

At what rpm does the computer and CVT keep the engine when the vehicle is going a steady 60 mph?

If the stroke of that 3.5L V6 is 3.21 inches
and you get piston speed by mulitplying:
2 times (stroke divided by 12) times rpm
at what average piston speed is the Murano's engine going for best economy setting?

How much throttle opening do you have to use to get the CVT to switch operation into 'maximum acceleration' ? At what engine rpm does the computer use for maximum acceleration? Is it peak torque or peak hp. Why?

for more info
see this Car and Driver Magazine weblink:

http://www.caranddriver.com/reviews/...awd-page3.html

a quote from the article:

"Bottom line, the engineers at Jatco who developed Xtronic with Nissan claim a 14-percent improvement in acceleration and a 12-percent boost in EPA combined fuel economy relative to typical four- and five-speed automatics."

 

wow hank you covered that really well.....

not only do you write books you link to them! oh i love it!

i've been wondering what kind of transmission they put in the caliber. now i know. they even put a CVT in it. my highschool team tried to do that for our robotics competition you might have heard of it FIRST... www.usfirst.org. we never finished it but it would have been REALLY cool.