Optimizing acceleration

Discussion in 'Fuel Economy' started by brick, Mar 13, 2006.

  1. brick

    brick Answers to "that guy."

    I've thought about this a little more and it's starting to make more sense. The fact that they give me two sets of shift points indicates that there really isn't one good answer for "when do I shift?" It depends on how fast you are accelerating. If your rate of acceleration is glacial, it stands to reason that you could keep the revs under 1800RPM without the engine protesting, since the load is so ridiculously low. At faster rates of acceleration (higher engine load) you need to let it wind up a bit more so that it can produce the power that you are asking of it. So I guess that's just a whole lot of words for what we all think of as common sense. If the engine is struggling the gear is too high or your foot is too heavy.

    Maybe we need to add a new acronym: SWEL = Shift With Engine Load. Don't confine yourself to a single shifting pattern, but adapt to the rate of acceleration that is required for a given situation. What do you guys think? We're just over-complicating the obvious, yeah? It seems important, though, since experience tells me that finding the right throttle position for a given speed and gear can be very touchy with respect to FE, and I may be driving around in entirely the wrong gear a lot of the time.
    Last edited: May 4, 2006
  2. philmcneal

    philmcneal Has it been 10 years? Wow

    I think i cracked it to why Wayne perfers super slow acceleration. The high mpg rates (35 mpg +) never bought down my average as it would do if I were to follow the manual's way to acccelerate (5-15 mpg). Here's what I discovered:

    1st gear littlest amount of throttle possible (20-25 mpg rates) up to 2000 rpms

    Shift (now wayne perfers the fast shift so that he doesn't lose velocity, since I'm a noob I shift slow and wait for the clutch to be done its buisness before attempting to accelerate since I can't afford a clutch job)

    2nd gear should be down to 1000 rpms again, now extremely little throttle (30 -35 mpg rates) and your speed should climb slowly, we talking about like 1 kilometers per hour per second! but your patience will be rewarded as your instantenous mpg goes up along with it! climbing by 2 points as you get up to speed oh here comes 2000 rpms again!

    Shift (i sometimes clutch in, go into neutral and wait for the revs to drop before sliding it into 3rd to make the sync, although its much harder to do when your revs are so low and the difference is not that great)

    3rd gear revs should drop to 1500 rpms, now the littest amount of throttle possible (first trying just to maintain rpms, then slowly rising up slow) and then your speed will increase by 1 kph again (those using miles it could be harder to judge since your numbers mean a lot!) and these mpg rates will be around 35 - 45 mpg rates and then another battle to 2000 rpms!

    Shift (ok from 3rd to 4th for some odd reason, is the easist gear out of them all. The motion of just "Down" and the difference in rpms is so little that this shift is just the easist to master, I don't know I guess you can say this shift is the fastest shift I'll do without losing speed like my first 3.)

    4th gear now this is where it gets exciting! back down to 1500 rpms, and climbing slowly by 1 kph again. But rates are at 45-60 mpg almost and even when climbing a small incline or some sort, I don't even have to downshift (unless i'm down to 1000 again) because apparently the small pull is still good enough, although with the mpg meter minus 5-10 depending on the incline and then going back up as the road steadies itself, but still very good! Even when reaching as high as 2000 rpms you can start to see the max mpg i can get 60 + and then starts to drop again as you climb over 2000 rpms... kinda cool.

    Shift (now from 4th to 5th is a little odd, the drop is quite big and I'm glad it is because I have a decent overdrive to boot! When above 2000 rpms (highway reasons) when shifting I do the sliding in the neutral trick and wait for revs to drop before shoving it into 5th with no risistance (i hate that feeling, why should a gear reisist to be selected? because its not ready yet!).

    5th overdrive (drops to 1500 rpms): Depending on the revs, my mpgs can be as high as 100 when giving the littlist throttle possible, or as much as 50 mpg if I'm climbing a small incline. What I like about 5th is when you climb inclines with 5th, your speed bleeds a lot less as opposed to in 4th, this definately tells me there's less friction to battle at 5th for sure! Just the gearing for the overdrive is so deep is that we have to make sure never to lug it (under 40 mpg instanteous) but using 5th to MAINTAIN or BLEED off speed is okay and should be done if you want to save some brakes!

    So lession of the day is, what the book recommends is the best ACCELERATION TO EFFICENCY RATIO and what WE want is HIGH FUEL EFFICENCY WITH NO MENTION TO TIME WHATsoEVER. Since I drive in the heart of the city and red lights are a commonblode to me (I don't think I've timed all the green lights yet... maybe one day) so I think I'll be practicing more of this type of acceleration just because it does not dent my average ever and I'll never see anything below 40 mpg!!!!! AVERAGE ;D

    but hey this is just a civic ;)
  3. philmcneal

    philmcneal Has it been 10 years? Wow

    details of my commute, interestingly enough engine load never went over 40 percent :O

    2300 rpms MAX (!)
    4.9 LPK or 47 MPG
    64 Km/h MAX or 40 mph
    35 km/h AVG or 25 mph
    8.7 KM drive (5.3 miles)
    12 minute drive
    88 max coolant temp (C) (max is 90)
    2 stop signs
    9 turns
    9 lights
    gone through 5 green lights
    4 1st gear starting out
    4 FAS ( bump started before my momentum dropped below 30 km/h then idled for less than 10 seconds before 1st gear start)
    .4 liters consumed (.1 gallons)

    on my way home wasn't as pretty, since i dediced instead of FASing, i'm going to give little throttle for 5th gear instead (at least i'm saving gas legally)

    5.8 LPK (40 mpg)
    2400 RPMS MAX
    64 km/h max
    40 km/h average
    9.3 km drive (5.5 miles)
    15 minute drive
    90 max coolant temp
    1 stop signs
    5 turns
    11 lights
    2 minute construction work idling wait
    7 1st gear starts (ouch... everyone went fast and made the green and i slowed poked to stop at it
    0 FAS
    .6 liters consumed (.2 gallons)

    looks like slow accel (1kph per second) suits my driving enviroment very well although there were a few lights on my way home I could have made it if I speeded up a little bit faster... so hard to predict those lights sometimes since you can't see what's waiting behind there unless you crossed the intersection yourself. By that time its already too late, what they need is more of those blinking lights that go "prepare to stop" or numbers on the sidewalk signs letting us know when the light goes yellow. Since I didn't FAS on my way back my battery voltage was at a high 13.5 (normally 12.7 after all the FAS) before turning off so I hope the cold tempeatures will stablize it for the next warm day since I leave it outside than putting it in the garage. At least I know now FAS is the more inferior FE choice than to cruisng down in 5th gear at extremely low rpms (under 1500 for 100 + mpg going slight downhill or flat bleeding speed).

    edit: i forgot to add and i thought it was equally as important. As you shift to the next gear and slow accelerate towards 2000 rpms (1 kph per second) I notice as the MAP starts out around 6.5 to 7 but as you increase the speed that number drops in .3 increments allowing your FE to jump up. As more speed is built upon, that same pressure on the throttle magically goes lower and lower as maybe the ECU finally realized that "hey I want to really conserve fuel man! Light off the pressure!" and slowly as you gain speed that exactly what happens! when I reached in MAPS of under 5.5 then looking at the tach i'm at 2000 rpms and then the MAP will increase over 6 again (higher fuel consumption)!

    Good thing we manual boys have the choice to shift! Although I wish I can still make it fast and smooth somehow ;( I need more practice!
    Last edited: May 5, 2006
  4. LoneWolf

    LoneWolf Member

    Hey all Fisrt post to site.

    I've enjoyed the reading so far. some nice tricks and techniques that I am slowing intergrating into my driving style.

    One thing I did to help my mpg was to change my manual tranny oil over to a full synthetic. This helped a lot in my winter commuteing getting me about 15% improvement in winter time driving... I can't remember the exact numbers becuase I changed it 2 years ago. I will try and look up some old gas receipts since I write the overall milage on the back after filling up full.
  5. tbaleno

    tbaleno Well-Known Member

    I belive krousdb uses 0w20 in is transmision. Its a good tip to pay attention to the trany fluids and not overlook any alternatives that may save you a few mpgs.

    I think its only been mentioned twice in all the threads. Thanks for bringing it up again. It can never be said too many times.
  6. krousdb

    krousdb Defiant NX-74205

    Yup, 0W-20 Mobil One since the day I got it. Smooth as silk.
  7. philmcneal

    philmcneal Has it been 10 years? Wow

    i can't wait to do my first oil change lol, at least getting mid 40 mpg is not too bad for dino 5-20 eh?

    i heard changing the transmission oil is a pain though.
  8. gonavy

    gonavy Well-Known Member

    ...auto trannys have had throttle-sensitive shifting since the mid-80s, doing exactly what you describe. I seem to recall some MT Fords (Escort GT?) having the 'shift' light come on at different points too, depending on the throttle position/engine load. One for FE, one for performance. I'm not counting the 'passing gear' shift drop which has always been around in ATs.
  9. psyshack

    psyshack He who posts articles

    Ive been following this thread with alot of intrest. The SG reports awful FE when leaveing a light. And quite truthfuly,, it dosent matter if your shifting at 1500 to 2000 rpm or nailing gears at redline. Ive noticed this from the first time I installed the SG. I was playing with it this morning. Seemed no matter what I did it's bad. I dont think it would be good if I had the local HS football team pushing the car to 10 mph then bumping it off.

    I wish some other 06 Civic EX, LX and DX owners would join us here.
  10. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Psy:
    ___This is where the Prius I, II, HH, RXh, TCH, and FEH knock the IMA based hybrid’s and all non-hybrid’s into the gutter … There is nothing like their slow and steady accel via EV up to 30 + mph when pushing tanks. Honda had better learn this really fast given they have had over 10 years of development and they still haven’t figured it out yet :(

    ___Good Luck

  11. psyshack

    psyshack He who posts articles

    I got called out to a job at 4:00 pm that a college boy contractor installed wrong. I love watching the college boys get fired. :)

    Anyway I had to pick the wife up at 5:15 pm at her place of work. This left little time to be screwing around in rush hour traffic. I drove the heck out of the Civic from the east side of Tulsa over to the exaulted campus of the University of Tulsa. Some hwy road work but more street work than normal.

    I drove the car hard! Redline shifts, short cuts with a bit of drifting. Quick fast moves,, a rolling ticket, I was.

    In the end i only knocked two tenths off the tank average according to the SG and ended up at 50 mpg for the day by the time I got home.

    All normal. Even the gas gauge was in the proper area for the miles driven. Wife and I where both suprised to say the least.

    The Accord when driven like this does its best to drink gas like a hemi car. You can watch the gas gauge fall with city WOT use.

    The worse tank I ever did in the Civic is 29 mpg. That was redline shifts, high rpm cruseing, A/C on, windows down sunroof open the 0-60 vids. All sorts of none FE driving.

    I dont know that its worth it to putter around at low rpms in the Civic. in city traffic and keep the rpms at 1.5k to 2k rpm shift points. Im sure it helps some. But how much is the question.
  12. philmcneal

    philmcneal Has it been 10 years? Wow

    wow sounds like the electronic throttle position and the vtec really helps optimize your fuel usage, sounds like you got the best bang for your buck.

    with my car though, a normal throttle cable anything can happen.
  13. johnf514

    johnf514 Zoom? Try Glide!

    psyshack, do you have any trouble rev-matching and heel-toeing with the ETC? On the standardshift.com boards, there has been some debate as to whether or not electronic throttle benefits standard shift driving techniques. It'd be great to hear your input.
  14. psyshack

    psyshack He who posts articles


    In normal driving to advanced driving the drive by wire has made things easy. When running thru the gears its much better to shift. The holding of rpms helps alot here. The shifter has notchy cheap feeling. But it just flips thru the gears.

    As for heal and toe. I dont mess with it in this car. In a fast downshift the rev's are very close to what is needed. Not worth my time. This just leaves basic brake work to help with setting the car up for the sidewall grinding turn.

    I dont drive near as hard has I have in the past. My brother has a Fiat x/19 and a lancer rally art. I was hoping to beable to run a few auto-cross's this spring and summer with him. As of yet this hasnt happened. The local SCCA chapter is running on Saturdays now and he's a Sabath Keeper.

    In day to day street driving the drive by wire has been a blessing.
  15. johnf514

    johnf514 Zoom? Try Glide!

    Thanks for the info, psyshack. If you do decide to get your feet wet and heel toe, watch for the slight delay that the ETC may create in your car. I believe one of our members has a car equipped with drive by wire, and it produces a slight delay in revs.
  16. Sabrejet

    Sabrejet Member

    xcel, I apologize if you have discussed this in another thread, but I want to optimize the acceleration on my Civic. I currently don't have instrumentation; an MPGUINO and elm 327 w/Torque Pro is in the pipeline. Is instrumentation absolutely necessary to optimize the acceleration?

    After extensive testing, I have discovered the following about my car:

    - the 1st to 2nd shift doesn't occur below ~10 km/h. I let up on the pedal to upshift at this speed.

    -for the 2nd to 3rd shift, I let up at ~32 km/h; it doesn't shift below this no matter how much I try. However, it will hold 3rd down to 20 km/h once its in third. It also seems to lock up in 3rd, but I am not sure; more testing is needed here.

    -the 3rd to 4th occurs at ~52 km/h. Lock up doesn't happen until ~75 km/h, although it seems to like 80+ km/h to reliably maintain lock up. 4th stays engaged down to ~40 km/h I think.

    Now on to my technique: ~1/3 throttle to 10, let up, ~1/3 throttle to 32, let up, accl at 2k+ rpm to 52, let up, and then accl at 2k+ rpm to 80 km/h (about 1/2 throttle). Finally, I try to maintain a cruise speed between 80 and 100 km/h in lockup (and hopefully vtec stage 1; there's no way to tell). The speed limit is 120 max, and 60 min. At no point do I cross 2.5k RPM.

    Instead of trying to accl at 2k rpm w/o lockup from 3rd, would 1.5-2k w/lockup be better? Is the 1/2 throttle accl to 80+ too fast? May I know how you accelerate your Accord?
    Last edited: Apr 2, 2015

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