Better Gas Mileage (tuning)

Discussion in '80-Series Tech' started by Tuning Haus, Jan 22, 2008.

  1. Tuning Haus

    Tuning Haus

    Messages:
    148
    would an aftermarket piggy back system like the Apex'i AFC fuel controller work with the landcruiser ECU?

    anyone ever thought or experience with trying to lean out the tune, to try to get better gas mileage?

    this is of course with a guidance of a wideband meter of some sort for a/f safety.

    any idea what a good a/f range should be? at idle, cruise and WOT (wide open throttle)?

    i know on my old 95 supra turbo, we tuned it to 15-16:1 a/f ratio at idle and cruise. WOT (wide open throttle) is 11.5:1 for safety

    i had 750whp but was still able to get 25 mpg if i cruised easily on the highway!
  2. landtank

    landtank SILVER Star

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    17,226
    Location:
    Groveland MA
    I had brought this up about 6 months ago. I've got a spare ECM and a wide band but right now the truck is being used for business so until spring any further work on it is on hold.
  3. Tuning Haus

    Tuning Haus

    Messages:
    148
    shoot i figured more people would have looked into this or tried it. being the ONLY thing most people see wrong on the landcruiser is the gas mileage!

    i guess i read somewhere on here that they had used a GREDDY EMANAGE to control the ECU. that is like a piggy back/standalone.
    didn't know it can be hooked up to the landcruiser ECU!

    http://forum.ih8mud.com/80-series-tech/190765-newbie-pix.html
  4. landtank

    landtank SILVER Star

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    17,226
    Location:
    Groveland MA
    IMO that's not the way to go about it.
  5. stereophile33

    stereophile33

    Messages:
    187
    Location:
    Portland, OR
    what engine management system is used on the cruisers?
    Jonathan
  6. Tuning Haus

    Tuning Haus

    Messages:
    148
    why would this not be the way to go?
  7. landtank

    landtank SILVER Star

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    17,226
    Location:
    Groveland MA
    Right now the stock unit controls the idling AFR to 14.7 and I think with a small change in the ECM you could alter that target and get what you are looking for.
  8. Tuning Haus

    Tuning Haus

    Messages:
    148
    that's good to know that factory stock, the idle is set at around 14.7:1 a/f ratio.

    that must be what cruising is set near to as well. i believe leaning it out to the 15's a/f wouldn't hurt the motor much if at all.

    question is, how much better would that give you as far as gas mileage is concerned? maybe 2-4 mpg?

    can you wire up an Apex'i AFC or of that sort to the factory landcruiser ECU?

    what was your way of going abouts this?
  9. landtank

    landtank SILVER Star

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    17,226
    Location:
    Groveland MA
    the way the ECU is designed all signal from various sensors pass through a resistor before heading onto the microprocessor. So a simple resistor change will shift the signal that the microprocessor sees and will result in a shift in that circuits control. The design and processors used in the LC ECU is the same as another company that I have worked with. However on those controllers the resistors were variable and a simple tweek would be all that was needed.

    I have the ECU just haven't had the time to verify the results.
  10. Tuning Haus

    Tuning Haus

    Messages:
    148
    so you're saying it CAN work right? with the piggy back fuel tuners on the stock ecu. it has worked with other toyota cars i've owned. but they were both supra turbos :)
  11. Tuning Haus

    Tuning Haus

    Messages:
    148
    so can someone (toyota master tech or a land cruiser guru) confirm what A/F ratio's SHOULD be or a healthy running land cruiser (STOCK):

    IDLE

    PART THROTTLE

    WIDE OPEN THROTTLE

  12. landtank

    landtank SILVER Star

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    17,226
    Location:
    Groveland MA
    I've given what the idle AFR is but as far as the other two it's most likely going to be load dependent. Everyone I know who has a wideband installed is boosted so they're not much help. I was going to do some work with my truck while still stock but haven't gotten around to it.
  13. Tuning Haus

    Tuning Haus

    Messages:
    148
    for the boosted parties, do they aim for around 11.5:1 a/f under boost and ~14.7:1 for cruise?

    i had my supra turbo at that but for idle and cruise i tried putting it up in the 15's:1
    had good luck with it and on 1000cc injectors, cruising on the highway i got 25 mpg with the a/f in the 15's

    i wonder if it would be safe for the Land cruisers to be in that area? low to mid 15's at idle. wonder how much help it would get in MPG. i'll probably get a wideband and see, hopefully shoot for around mid 15's IDLE AND CRUISE

    right now, my LC get's around 13-14 mpg
  14. CivicFerio

    CivicFerio

    Messages:
    168
    Location:
    Chatsworth, CA
    One the tricks they did in the OBD1 days is to install a variable resistor on the primary O2 sensor. This is done to fool the ECU that engine is running rich and pulls back the fuel. You'll know when to stop when the engine starts to lean misfire.

    14.7 A/F ratio is required to keep the cat in optimum working temperature. Richer will make it too hot and leaner will make it too cold. Factory ECU usually is a tad richer for safety reasons. So a tad leaner will usually gives best HP with the expense of NO emissions.
  15. landtank

    landtank SILVER Star

    Messages:
    17,226
    Location:
    Groveland MA
    on 95~97 trucks with the stock MAF under long boosted runs at WOT they are hitting @8.6 AFR. With my modified MAF it's up to 10.8 AFR and this is consistent with both Supercharged and turbo'd trucks.

    Not a lot, read: none that I know of, have had any success with piggy backing our ECM. Safari offered a UniChip that actually damaged it. So don't assume what you know to be true of other Toyota's will cross over into this truck.
  16. Tuning Haus

    Tuning Haus

    Messages:
    148
    do you know what the compression ratio is on the boosted landcruisers? with those metal head gaskets, do they decrease the compression ratio any (to run more boost)?

    also 8.6 is insannnnely rich and 10's are still REALLY rich too... i dont know if it's different for each boosted cars?
    i was told for my car 11.5:1 in full boost is still very conservative.

    so has anyone actually tried a small piggy back with their landcruisers? like a HKS VPC and or APEX'i AFC, etc?
    what all has people used besides reflashing their ECU's?
  17. landtank

    landtank SILVER Star

    Messages:
    17,226
    Location:
    Groveland MA
    from what I know everyone is running the stock HG. The only person that I know who has done any real work with piggy backs is Christo Slee and my understanding is that it didn't work out so well.

    IMO it's due to the stock MAF sensor. On the trucks that have reported OBDII readings, the stock MAF sensor will saturate at around 25 lbs of air. Once this happens the stock ECU goes into limp mode and dumps fuel. The thing to remember is that point fluctuates with air density. So today it might be 25lbs and tomorrow 26lbs.

    No flashing on these ECUs either that I know of.

    So that is it in a nut shell. We're nut a bunch of tuners by nature and I'm sure we'd love to see a nice thread from you on how you go about it.
  18. p8nt

    p8nt

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    Location:
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    <----- subscribed
  19. Tuning Haus

    Tuning Haus

    Messages:
    148
    just yesterday i discovered a few vacuum hoses popped loose under the intake manifold.

    my cold start idle was also pretty high in the last couple weeks. my gas mileage has gone worse.

    funny thing is when i tried to connect that vacuum hose back on (with the car running) i got electricuted or zapped a bit! lol

    i turned the car off and of course put it back on and walla, the high idle on cold starts have stopped!

    the gas mileage i believe will get better as well. i've increased mmy tire pressure to 38 psi all around. they were around 32-33 so we'll see if that helps any.... in my quest to increase gas mileage on the cruiser!!!
  20. Boone

    Boone

    Messages:
    790
    Location:
    Boone, nc
    Just for clarification civicferio stated that a richer mix would run hotter but that is backwards a leaner mix will run hotter than a richer mix. It might have just been a typo but i thought i'd clear that up.

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