Notice something today
 

Blackhawk has a 3speed auto in it. i was at a red light and as i took off slowly. i listened for the shiftes to see at what mph the shifts happen. 3rd gear(top gear)was at 30mph. now since i'm in the top gear, the gear that most automatics get better mpg. would this mean that i would get better mpg's in the city? because the engine is reviving somewhat high at 50-55mph without a 4th gear and/or overdrive.

that is interesting for you to bring up. I would think that you get alright mileage at lower speeds like 30-40 mph but I could see that you would get better around 50 or so. you are turning more rpms but you don't have the aero drag that you do at say 60+.

I have heard that most cars aero drag goes up exponentially from 53 mph and up. I know that this is a generalization first of all. the idea is that your mpg would continue to go up as speed goes up as long as drag was not a factor. if you were to test on a dyno where the car wasn't moving, you would see this.

I too have an auto. mine isn't as bad as yours (its a 4-spd) but I am turning almost 3k rpms at 60 mph. I haven't seen 60 in a while but I rev high compared to others. I get into overdrive around 35-40. it will kick in at 35 but if i try to accelerate at that point, it will drop a gear. 40 seems to keep me in top gear if I need to easily accelerate.

I have been trying a new technique I call it "PUNCH IT FOR FE" I give it half or better throttle until I get to 40 mph to get me into overdrive faster. so far it seems to be netting some gains for me.

"Punch it for FE" works on my GMC K1500 pickup. Once I got my SG I realized that touching the pedal at all in first or second results in instant MPG readings of 1 - 2 MPG. Even a "Feather touch" on the pedal does this. That is when I realized I had nothing to loose, just give it 1/4 throttle and get into a better gear quicker. I usually give my truck 1/4 throttle until it is ready to shift into third, then I back off the pedal.

-Jay

Yes Jay and BEEF this works. I have noticed the same thing. If you "feather touch" the gas pedal to get to O/D you are staying in the lower gears longer thus using more gas for a longer period of time. Just get on it "a little" to get to O/D and hold your cruising speed. Thank you Scangauge for showing me that.

i think i was misunderstood. i my question was: driving like a city speeds(since my car shifts to its top gear so quickly) give me better mpg's then say highway speeds. vecause the engine is really pushing without a fouth gear or overdrive.

Yup, I can report that "Punch it for FE" works for my automatic too.

I suspect that cruising at 30mph in high gear (and if your TC can lock, then with your TC locked) would be more efficient due to aerodynamic and engine efficiency reasons.

I apologize for highjacking this thread. I was trying to answer your question.

I would think that you would still get better FE at 50 mph and maybe slightly higher because of aerodynamics. there seems to be a threshold on aerodynamics where drag goes up drastically. I know it is different for each car depending on its own aerodynamics but I have heard that the average is around 53mph. also that is old information so that number may be higher.

you could also experiment with different speeds and the MPG at those speeds if you have a scangauge. many on here talk about their "SWEET SPOT" where FE is the best for their car. mine seems to be around 50 MPH which is where I try to stay if I can. obviously I don't go 50 on roads where the speed limit is 65. that is just plum dangerous.

I can't say for sure but I get better FE at almost highway speeds.

Yes your best city mileage should be when loafing along in top gear. However, if your TC isn't locked at that point it's probably not as good as going about 45 with the Torque Convertor locked up. Then there's often a glitch in the upward soar of the drag force vs speed graph, as the Cd of the vehicle might be different in laminar and turbulent flow regimes, so just after the transition to turbulence there might be a sweet spot where drage drops a bit before it goes swooping upwards again. However, this varies according to the air density, which changes with humidity, temperature altitude, and then windspeed relative to the car adds or subtracts to your optimum speed... in other words, trying to stay in the sweet spot every day is close to unpossible, and you'll get the odd amazing run in perfect conditions, but in general you're better off sticking to the sub 55 mph regime as best all round mpg speed.

Do you have any idea about TC Lockup?

I thought my car didn't have it (because fueleconomy.gov doesn't list it as a feature on my car, but does on many others), but when I said that to someone, he said to me, "It has O/D, right?" And when I confirmed, he said "Then it has lockup."

Maybe since yours doesn't have O/D, it doesn't have lockup either?

Since then, I believe I have confirmed this. Here's how: If I drive around with my foot on the gas @ 40MPH, and then let all the way off the gas, the tach drops from ~1900RPM to ~1200RPM, nearly instantly. If I drive around with my foot on the gas @ 50MPH, and then let all the way off the gas, the tach drops very slowly until I reach 45MPH, then drops nearly instantly to ~1200RPM. I am assuming that this is the TC unlocking at 45MPH.

I have also then wondered, am driving back roads (which I often am), where my speed will vary quite a bit, say in a range from 35-50, should I avoid TC lockup? (Explanation: I won't stay in lockup for long, but while I am in lockup, I am using more fuel in the decel from 50-45 because the RPMs are higher--my car is too old to have DFCO).

P.S. If anyone has been wondering where I've been, I've been busy. I will probably continue to be busy for a while. :( :confused: :)

I'm not aware of any correlation between OD and lockup, but I wouldn't be surprised if they usually come together.

Avoiding lockup will never do you any good. Lockup is better any time you're applying power (foot on the gas enough to accelerate, cruise, or very lightly decelerate). Unlocked is better when your foot is off the gas, unless you're going for DFCO (and even then, sometimes it's still better). When unlocked, energy is wasted sloshing the transmission fluid; the energy dissipates as heat instead of being moved through the drivetrain.

You want it unlocked any time the transmission shifts, when you're at a dead stop, and when you're starting from a dead stop. Any other time it's better locked.