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Thread: supra TT and 800cc denso injectors, low impedance : works well, but hard to restart

  1. #1

    Default supra TT and 800cc SARD injectors, low impedance : works well, but hard to restart

    Hi,
    i just finished my setup on my supra (euro spec) :
    - sequential hybrid turbos (munroe ones in australia well know for them)
    - stock fuel rail, tapped in an6 to have dual feed, fuel pressure dampener removed, fuel pressure regulator at 40 psi.
    - Before making the fuel mods, i tried to start with 550cc injectors and a 550cc basemap for my mapecu3. All works well : cold, hot starts, and cold compensation, in maf suppression mod.
    I have already disconnected the two stock O2 sensors, like it's advised in this forum.

    - Then, i mounted 800cc denso injectors, low impedance, instead of the 550 stock ones. I used a base map 850cc to start, and it works well, start is a bit difficult.
    I tried to run in first, second and 3th gear, with no boost pressure. It seems ok and i'll go to a professional map man with dyno. I can modify AFR, no problem.
    >>>But i have a problem : once the engine started, it's very difficult to restart. I have to turn key at least 5 or 6 times. And once engine started all is ok, and sounds great (?!).
    I even discharged my battery.
    Any idea ? I wonder if map ecu is fighting the oem ecu only during starting... What could i do ?
    I'm afraid to go far from my garage !
    Is it a matter of fuel pressure settings ?
    I join my map with configurations, for CLT compensation, O2 WBand resadings, EBC (not used at this time)...
    Thank you a lot for your answer.
    Marc, France
    Last edited by supra64; 19th-May-2017 at 10:03 AM.

  2. #2

    Default the .tbl file to help you...

    Here is my config file with map (primary map only, the secondary is a 550cc one)

    supra800cc8mai.tbl

  3. #3

    Default

    Hi Marc,

    Quick question. Are the new 800cc injectors the same impedance as the old 550cc injectors?
    MAP-ECU Support

  4. #4

    Default

    Quote Originally Posted by MAP-ECU Man View Post
    Hi Marc,

    Quick question. Are the new 800cc injectors the same impedance as the old 550cc injectors?
    Hi, thank you for answer.
    Yes they are low impedance (2,7 ohm somethink like that), 800cc denso, like stock denso 550cc injectors.
    I think i found the problem : I started this morning with 720cc basemap. As i saw in this forum, the problem is the line "0 mmHg" and low rpm during cranking. 0-200-400 rpm i think.
    Once engine start it's too rich (because of the 720cc map) and i need to swap with the other 800cc map. And AFR are more correct. I tried to richen -a lot- the aera 0 mmhg -> vaccum between 200 and 400 rpm.
    It seems to be better at idle, just after cranking. But still difficult with hot starts. Nevertheless i noticed if i wait 1 or 2 minutes before crancking, it's easier (?!). I don't think it's vapor lock, because this pb occurs, even if motor is cold : first start is perfect. I wait 10s idle, then stop. And restart is possible, whereas engine is still cold... looks like too wet plug ? I will have a look to them next week when i come back home.
    Perkaps should i make leaner line 0mmHg-200rpm and richer lines after 400 rpm ?
    I don't know what to do to enable hot start... help !
    Last edited by supra64; 11th-May-2017 at 08:16 PM.

  5. #5

    Default

    So just to confirm, Euro Spec is low impedance injectors like USDM and you have resistors in series with the injectors?

    One thing I forgot to ask is which wiring diagram and base table you are using? Based on what you have said, I wonder if the difference between the tables is the "MAF Out RPM=0" which is the MAPECU3 output when you turn on the ignition. This value is used by the OEM ECU as a starting point for fuelling.
    MAP-ECU Support

  6. #6

    Default

    Hi,
    yes euro spec are same supra as USDM. I kept the resistor box in serie, like with 550cc.
    I am in "maf elimination mode", with the harness. All was working great with 550cc.
    pb appeared with 800cc and engine restart.
    "Maf out rpm=0" field is setted to 450 like for USDM supra. I read on this forum that it is advised not to modify it.
    I noticed it's the first raw at 0 rpm used as starting point for fueling.
    Should i attempt to modify it a little ?
    I used CLT compensation setted at -0.02 or -0.03 % per degree to compensate cold enrichment made by the stock ECU. No IAT for the moment, neither baro compensation.
    I used the 850cc basetable : 2JZGTE850cc.tbl
    Last edited by supra64; 12th-May-2017 at 10:32 AM.

  7. #7

    Default

    Thank you for the information. You might be able to change the fuel table values around cranking voltage but some more information will help. Just to clarify, when you have the hard starting problem, can you please clarify the following:
    1. Is the coolant hot or cold?
    2. Is the engine and under bonnet hot, i.e. heat soak?
    3. Can you create a MAPCAL log file of the starting problem?
    MAP-ECU Support

  8. #8

    Default

    Quote Originally Posted by MAP-ECU Man View Post
    Thank you for the information. You might be able to change the fuel table values around cranking voltage but some more information will help. Just to clarify, when you have the hard starting problem, can you please clarify the following:
    1. Is the coolant hot or cold?
    2. Is the engine and under bonnet hot, i.e. heat soak?
    3. Can you create a MAPCAL log file of the starting problem?
    ok i will make a log file on sunday when i'll be back home.

  9. #9

    Default

    Hi,
    1- Is the coolant hot or cold?
    If coolant is hot or cold, the problem is still here : second start is very difficult. Unless i wait a few minutes.

    2- Is the engine and under bonnet hot, i.e. heat soak?
    The IAT sensor is under rubber air filter in which i made a hole. So there is no risk of heat soak. Weather was fine and temperature was between20 and 30c so indicated sensor values are ok. There is no bonnet for the moment (I removed it for new painting). And i disabled IAT compensation.

    3-Can you create a MAPCAL log file of the starting problem?

    -->> I join you the map i modified a little, and a few log files, engine hot :
    Files are here :

    https://www.dropbox.com/sh/ikdcloxhn...e9JQG-Vea?dl=0

    * log1idle_hot.log is when engine is hot, idling.
    * log2start5try is just after engine is off. I tried to start it and i needed 4 or 5 attempt to start.
    * log10gears1to5 is a log on road. I ran from idle to 5th gear engaged. It runs good.
    * log20start_difficult is after road trip : i stopped engine, and start was difficult. I made several attempts before this log.

    --> This morning, i made 3 logs with cold engine :
    * log31cold_first_start_ok : it's the first start : no problem, all is ok. Engine was idling during less than 1 minute.
    * log32cold_second_start_difficult : And now, it's difficult to start (?!) but it starts.
    *log33cold_third_try_failed : starting is impossible. And engine is still cold...

    Screenshot_cold_engine.pdf shows the mapcal dashboard page, where you can see temperature.
    The map is supra800cc13mai_v2.tbl

    This evening, i made an auto diagnostic : I have 3 default code : 21, 24 and 27.
    * number 21 means n1 O2 sensor problem : it's normal because it's disconnected to avoid closed loop problems during idling.
    * number 27 means n2 O2 sensor problem : Disconnected too to avoid closed loop problems
    * number 24 means Intake Air Temperature stock sensor problem (open or short circuit) : it's normal because i disconnected stock MAF to use mapecu3 MAP sensor and "MAF elimination mode".
    -->> All is ok ? no need of resistor to simulate stock IAT signal ?

    Last question : I read on pdf documentation : "It is vital that TPS Idle and TPS Max are set correctly otherwise TPS enrichment will not operate correctly".
    And supra basemap 550, 720 and 850cc have TPS idle setted to 475, 520 and 550 respectively. I used the value 550 for my 800cc injectors.
    -->> Should i measure voltage 0-5V precisely and convert it to the scale 0-4095 for idle and max ? Or is it useless ?

    thank you for your help !
    Attached Files Attached Files
    Last edited by supra64; 17th-May-2017 at 09:27 AM.

  10. #10

    Default

    Hi, any idea ?
    I'l try to decrease timing advance a frew degree (4 or 5) at low rev (200-400 rpm) in 0 to vaccum areas. I read it could make start easier when not absolutely cold (because gas burn then faster).
    I didn't change anything in timing advance by then.
    Last edited by supra64; 18th-May-2017 at 07:47 PM.

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