Z32 Injector dead time

Discussion in 'Technical' started by Blue300, Oct 2, 2019.

  1. Blue300

    Blue300 Member

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    Hi, im after some advice regarding correct injector dead time.

    I have a set of deatswerks 740cc injectors running at 60psi fuel pressure. The fuel base map is setup ok accross the rev and load range.

    I had the haltech, injector dead time battery voltage on 1.850ms @ 13v, and 1.650ms @ 14v.
    At top end i was leaning out at mid 13 afr's on approx 21psi boost.
    I reset the injector dead time to 1.900ms @ 13v and 1.680ms @ 14v and left the fuel maps the same and is now feeling much better with afr's at low 12's. But looking at the logger data, fuel injector was at 92% duty cycle.

    On the deatswerks 740cc fuel injector characterization summary, at approx 4.5bar of fuel pressure 14v battery offset should be 0.719ms. But ive programed the ecu to twice that value, i must be doing something wrong because the dead time numbers are way off what they should be in the flow data if im reading it correctly.

    Advice will be much appreciated.
     
  2. MagicMike

    MagicMike Moderator Staff Member

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    Deadtime matters less at higher duty cycles.

    Use the fuel map to give more pulsewidth, leave the deadtime alone.

    I was going to post in your other thread that I think you are asking for trouble with such boost and afr.

    You need to log fuel pressure.
     
  3. Blue300

    Blue300 Member

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    Ok thanks, anything over 5000rpm and 60kpa manifold pressure on the fuel maps ive set to 100%.
    From 4000rpm to 5000rpm in the same manifold pressure is set from 92 - 98%.
    Im thinking the only way to monitor pressure would be through a digital fuel pressure gauge,
    Unless i increase the FPR even higher but then wouldnt that affect the dead time values
     
  4. MagicMike

    MagicMike Moderator Staff Member

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    Sounds like you are running out of pump then.

    Turn boost down until you sort out some kind of fuel pressure log or gauge so you can know what is happening.

    If you have a haltech just get a sensor and hook it up.
     
  5. Blue300

    Blue300 Member

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    Good idea with the haltech sensor, are there any haltech retailers in melbourne, 99% of everything for a performance car is in syd or qld.

    I got the fuel pump quite a while ago i think it was a dw 300lph pump, back then i thought it would ok for 14psi but now it could be maxing out at 22psi with 740 injectors.

    Im happy with how its performing now as long as the dead times and 60psi of fuel pressure that ive set wont screw anything up as im now going to try an advance the timing a little more.
    Because the injectors are brand new im hoping 92%+ duty cycle will be ok
     
  6. MagicMike

    MagicMike Moderator Staff Member

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    If you are leaner than 12.5 and don't know why, just stop. Certainly don't throw any more timing at it.

    You are guna have a bad time.
     
  7. Blue300

    Blue300 Member

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    The haltech i set at factory igniton timing. Ive increased it by 1 or 2 degrees over the whole igntion map but i think it might still have alot of advance in its potential.

    I need to find a good timing map from somewhere to compare against what ive currently set it to.
     
  8. MagicMike

    MagicMike Moderator Staff Member

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    Inb4partout
     
  9. Blue300

    Blue300 Member

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    I can totally understand tuners not wanting to hand out they're tuning data to just anyone.
    Id happily pay a tuner to get the best results of advancing the ignition timing but i'd rather the enjoyment of doing it myself through trial and erroe.
    Ive only done mechanical work on my car but ever since getting a haltech, i love finding out all the ways to make it run to its full potential, its good fun and very intresting to use
     
  10. zx299

    zx299 Well-Known Member

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    Firstly, never play with timing until you get your fuel sorted out :eek:

    And, if you insist on going down the DIY path, I would suggest you read EVERYTHING you can lay your hands on about tuning ....... multiple times, before continuing :cool:
     
  11. Blue300

    Blue300 Member

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    Defintley, i agree. Im pretty new to the car tuning and modifying scene and very much a beginner, there are many many parts, data and even terms im still unaware of.
    But to learn something you enjoy doing, you have to start somewhere.
     
  12. tassuperkart

    tassuperkart Its a lie I tell you!

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    If youre messing with injector dead times to make fuel ends meet then you have a fundamental config or setup problems. Surely that obvious......

    Firstly, petrol or corn juice?

    Next, voltage readings at the fuel pump @ 60psi base pressure plus boost pressure. Has the fuel pump wiring been upgraded to reflect this?
    Has the actual pump simply maxed out?

    you need to KNOW this stuff before you start guessing the engine needs more ignition..

    At that fuel pressure, those 740's should be flowing nearly 850cc which is good for about 650Hp.

    Im guessing your road tuning this...................

    What makes you "think" that the engine will tolerate more ignition? You have logged data from a knock sensor or just guessing?
    Going back to your tuning strategy, how can you determine this with a 600+ horsepower power pull on the road??? Or is this all on a dyno?

    Id suggest you forget about what you "think" and work with what you actually know. Just a few degrees of ignition either way of peak torque can mean either an insignificant loss in power OR a grenaded engine depending which way you "guess" it.

    Are the injectors correctly scaled to begin with? This will skew the duty cycle figures all over the show and the ECU may be erroneously reporting high duties as a result
    Go back through your datalogs and display injector durations in milliseconds at Max VE. Scale that against the RPM you are actually using and determine your actual duty from that.

    Knowing you have a fuelling issue that your bodging up to get around and THEN suggesting it needs more ignition is foolish to the extreme.
     
    MagicMike and Martin Williams like this.
  13. Blue300

    Blue300 Member

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    I found the problem as to why i would be running good afr's sometimes then it would lean out way too much, i tried reducing the timing down to 1 - 4 degrees btdc and it would still run lean.
    I thought it could be the fpr causing the problem so i put the stock fpr and fuel damper back in and still same problem.
    I was driving home it started to lean out even more until it lost all fuel pressure and wouldnt even start.
    The fuel pump wouldnt switch on at all to prime so i thought making the fuel pump work too hard at its full capacity has caused it to fail.

    While waiting for a tow truck and eating a pizza i had earlier purchased before the car broke down, i was reading an article on czp about a similar problem not about fluctuating fuel pressure with a new fpr installed, the underlying problem being the fpcu.
    I setup a bypass for the fpcu and just as the tow truck arrived i was able to start the car with the fuel pump whirring much lounder than ever from getting full battery voltage.

    Ive left the bypass in place and is now getting consistant afr's of 10.9 - 11.5 at full boost and high rpm with ignition advanced upto 8 degrees at 6000 - 7000rpm with 22psi boost.

    I know i shouldnt be running the fuel pump at full battery voltage on standard wiring so it looks like ill be upgrading the wiring to an appropriate gauge from the relay directly to the fuel pump
     
  14. zx299

    zx299 Well-Known Member

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    Do yourself a favour and just replace the fpcu
     
  15. Blue300

    Blue300 Member

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    I just typed into the search bar 'fpcu' and cane back with 3,860 results, im gusseing these damn fpcu's are very troublesome and getting a new one will still probably cause one issue or another down the track.
    The Dw300 fuel pump can handle max voltage of 18v. Or 12 amps at battery voltage of 13.5v, as long as im running minimum 8 gauge wire then im going to do away with the fpcu for good
     
  16. zx299

    zx299 Well-Known Member

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    Years ago when Ashpec (in the US) was developing a fpcu for twin pumps, he stated the oem fpcu could handle up to 30amps.

    Do you reckon you're going to be drawing more than that ?
     
  17. Blue300

    Blue300 Member

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    I wont be needing 30 amps of current for the fpcu to handle or to send to the fuel pump.

    Even if the oem fpcu can handle that much current i dont see the need to have it there in the first place, if i can comfortably run the fuel pump at the same speed the whole time
     
  18. rob260

    rob260 Moderator Staff Member

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    Most aftermarket fuel pumps will not run well on less than 12v. I’m not familiar with DW but have done plenty of Walbro installations and you always always always bypass the FPCU.

    The easiest way to do this is by grounding the earth wire from the bulkhead harness.

    Depending on the specs on your pump you may also wish to (be a really good idea to) power the pump via a dedicated relay.
     
  19. Blue300

    Blue300 Member

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    Im wanting to setup a dedicated relay as fuel pressure at 40psi draws 12amps at 13.5 volts so i reckon its not going to take long to burn out the oem relay.
    I was going to buy a walbro 460 but at the time i thought i may have had install problems with it being overdimensional
     
  20. rob260

    rob260 Moderator Staff Member

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    I don’t know what you mean by overdimensional? But they fit and work well.
     

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