Throttle Position During Acceleration and its effect on FE

[omgwtfbyobbq]

This?

It pretty much sums up why diesels get so much better mileage than gassers. Even though peak efficiency is about the same when taking into account the difference in BTU per gallon, they have better BSFC ovals in terms of low load driving.

[MetroMPG]

BSFC plots engine load (throttle input) against fuel consumption, and it's a way to see at what point an engine is producing the most power for the least amount of fuel consumed.

It's a useful thing to know when considering acceleration tactics, but not particularly useful once at cruise (when you want the lowest overall fuel consumption rate, regardless of whether it's the most efficient in terms of power produced per unit of fuel burned).

[omgwtfbyobbq]

It can be, if the driver decides to pulse and glide, depending on curcumstances. But than again, I guess that's not cruising, even though the pulse and glide driver can have the same average speed and the one cruising, as well as better mileage.

[MetroMPG]

I'd make the same distinction: P&G isn't cruising, even though it can have the same avg speed.

I tend not to P&G on (infrequent) freeway trips. I save it for shorter, lower average speed rural highway driving. I try do it in moderation because it's harder on the vehicle (and the driver) than cruising.

[Compaq888]

Well I tried the Moderate accelaration technique. Shifted into 2nd at 10mph, 3rd at 15mph, into 4th at 20mph, into 5th at 30mph.

Barely did any P&G because my speedo would plummet like a fat man off a roof.(Yes I know objects of different weight fall at the same rate.)

Whenever I saw a yellow or red I coasted in gear.

Did a trip of about 25 miles. ALL CITY 42.9MPG <---Scangauge data
Stopped at about 50-60% of the lights. Which means it's real life data, that's how it usually is in the daytime.

My best tank thus far is 42.00mpg and that's mixed driving(freeway and streets) and that's with really slow accelaration.

[onegammyleg]

Originally Posted by LxMike

my cars auto tranny the t.c will lock up at 42 mph. when it does rpm's drop 300-400 and mileage jumps from low 30's to consistent mid 40's and nearly 50 at times. I think this is my next mileage exp to work on.

You might want to investigate the way your TC systems locks up.
Perhaps you can force an early lock up manually with just a switch and some extra wires.

[molecule]

whats the relationship between BSFC and Torque...???
i think in this lies the total answer per engine
because transmissions are torque multipliers...
and clearly any engines power output is going to be related to its fuel consuption fairly directly...
your best pull on a dynamometer is most accurately interpreted in 3rd gear...
because its a 1:1 ratio or the closest to it...and then considering the final drive gearing...
i haven't mastered this math...but i'm sure its what needs to be looked at...

cross reference your dyno plot with a bsfc plot and i think you could find your 'target average rpm' fairly easily...
leading you finally to the best speed to maintain in 5th gear...etc
and i wont be surprised if your average rpm for acceleration should be up over 3k on many engines...

personally, when i accelerate, i can feel the engine produce near its maximum acceleration when pressing the pedal further induces no gain...
its somewhere close to 33% and i carry the lower gears to higher rpm...4k-5k...
because they multiply the torque more...so use it while you can get it...

[JanGeo]

Originally Posted by Compaq888

Barely did any P&G because my speedo would plummet like a fat man off a roof.(Yes I know objects of different weight fall at the same rate.)

In air objects of different densities fall at different rates i.e. a feather falls slower than a paper clip although they weight about the same weight. So your small frontal area heavy car does better than a lighter one on a downhill or coasting on a level surface. This helps you with the pulse glide because with higher weight you can run the engine under load longer and then coast longer. Your best savings for coasting is going to be on slight downhills. Now if you are not rolling freely then you need to check your wheel drag. The greatest savings while coasting is at higher speeds if you keep the engine running - with the SG you can now see at what minimum coasting speed your mileage drops below "in gear" mileage.

[rh77]

If I know I'm going to be cruising under load, I get into top gear +TC, with 45% throttle, lifting to shift at 3000 RPM, get up to the desired speed +5 MPH, and let off the gas to drive with load on hills, etc. It gets to the optimum FE quicker, instead of lagging in low 20's on a slow accel.

Also, my TC is super sensitive in cold weather and requires something to kick in. Prob. coolant temp/trans. load. I've looked into a switch, but I believe I have a TCM.

RH77
Referring to the 'Teg

[molecule]

i forgot to link the calculator i host...
yeah i stole it...but only because i lost the original link to the site...
credits of creator are still on the page

you can open in text editor to change default values...
or just enter them in the page each time
differential gear is the final drive...and then just choose a gear
http://users.adelphia.net/~digitalcongo/tirecalc.htm