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Charge temp table... again

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  • Charge temp table... again

    I have read every thread on the forum regarding the subject, I have tried different approaches described and yet I am still finding myself in a situation where my AFRs jump with even slight air temperature changes

    to give you an idea, I go from 11.2 to ??? (because my WBO2 doesn't read below 10 so who knows what it really is... sometimes I feel I can run a hose from my exhaust straight back into the fuel tank) - and this is when ambient temp goes from 28 celsius to 15-18

    I am running Autronic IAT sensor in my intake manifold (in the back, on the right side, I plan to move it to the left side where stock Spec C sensor used to be to move it away further away from the turbo) and upgdaded bar and plate top mounted intercooler

    the last approach I tried was increasing the charge temp value so that the ECU doesn't rely too much on air temp compensation, and it seemed to work at first, but as temps dropped more the car still ran too rich

    Dyno time is hard to get over here, and is pretty expensive, so it means I wasted all that time and effort dialing my AFRs with a table that didn't work from the start, and all those charge table modifications and base fuel table alternations were useless as well....... aaaaaaahr, I love my SM4 but that chage table is so frustrating!

    I am sure I don't have such a unique setup, can someone share a charge table for a similar setup? Subaru, TMIC, Autronic IAT in manifold
    I will be building a new shortblock over the winter, break it in and put on the dyno again to dial in fuel, so I just want to be certain I will be doing it with the right tools from the start

  • #2
    Im using the charge temp table for the PnP V6 STI SM4 and the temps here recently changed from ~30C to under 15C and my AFRs stayed pretty steady.

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    • #3
      oh I know it works, I just seek help setting it up or a base table I could start of from a car with a similar configuration

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      • #4
        ... thats what I suggested. the map from the PnP SM4 for the STI as a base.

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        • #5
          yep
          this is what I used for my initial tune

          air temps dropped, car ran pig rich

          are you using Autronic IAT sensor and where did you mount it?
          Attached Files
          Last edited by Hyper; September 20th, 2015, 11:58 PM.

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          • #6
            Try changing the setting of the cell(s) being use at the time it is running 'pig rich' or lean - whichever the case may be - to either 0 or 100. So, setting it to the extreme ends of compensation. I'd be interested to know if it changes the AFR so radically as what you are experiencing.

            Something I've noted that DOES affect AFR is fuel temp. And probably injector temp as well.

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            • #7
              Using the Autronic IAT just above the fuel injector in the back right cylinder (closest to turbo)

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              • #8
                Originally posted by Nutzy View Post
                Try changing the setting of the cell(s) being use at the time it is running 'pig rich' or lean - whichever the case may be - to either 0 or 100. So, setting it to the extreme ends of compensation. I'd be interested to know if it changes the AFR so radically as what you are experiencing.

                Something I've noted that DOES affect AFR is fuel temp. And probably injector temp as well.

                whenever I make 5-10% percent changes in my fuel table per given IAT I see instant change in AFRs
                I understand where you are coming from with respect to fuel temp, but I am running stock fuel pressure with stock fuel system, so I am not really pushing/heating it up in my caes

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                • #9
                  Originally posted by Hyper View Post
                  whenever I make 5-10% percent changes in my fuel table per given IAT I see instant change in AFRs
                  I understand where you are coming from with respect to fuel temp, but I am running stock fuel pressure with stock fuel system, so I am not really pushing/heating it up in my caes
                  OK, I have found my charge temp table to be pretty insensitive.

                  Is there some other factor that is a multiplier of this table?

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                  • #10
                    I'm sorry, I thought you were referring to the fuel base table

                    setting extreme ends does change AFR, experimented at idle

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                    • #11
                      Originally posted by Hyper View Post
                      I'm sorry, I thought you were referring to the fuel base table

                      setting extreme ends does change AFR, experimented at idle
                      Yes, it will change AFR, but can it change it by 1 or 2 points as you were indicating?

                      I have played around with the charge temp table a fair bit and have not been able to dial out the idle going lean by about 1 AFR once things get all toasty under the hood. This is why I suspect there is more to it than just CHG T compensation.

                      I'm using SM4 default values. The IAT is the SM4 unit and is screwed into the plastic intake manifold just behind the throttle body - good airflow there.

                      Just as an aside, flex fuel sensors also incorporate fuel temp in their output so the ECU can increase pulsewidth as the fuel warms up.

                      Another point, some fuel regs are appalling at maintaining fuel pressure as temp increases - yes, Malpassi. I'm looking at you!

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                      • #12
                        Hyper, looking through the Ring log file that you sent I notice there are a few things that need further investigation.

                        Firstly, the fuel pressure does not seem to track the manifold pressure linearly on the vacuum side. On the boost side the logging suggests the base fuel pressure is about 3.15 bar while at about 50 kpa manifold pressure the base fuel pressure looks to be 3.5 bar and around 15 kpa manifold pressure the base fuel pressure looks like 3.75 bar. There will be a difference due to the baro pressure if the FP sensor is gauge type but from the log the Baro looks to have been about 95 kpa so that will only be 5 kpa offset. If the pressure reg can't bypass enough fuel at light loads the fuel pressure can vary significantly due to pump voltage supply and temperatures.

                        The other thing is that the injector comp does not seem to be correct. This can be seen at the end of the log where the AFR changes by 1 whole ratio when the fans turn off and the voltage changes slightly. The cal shows ID1000 injectors and all the ID comps are very good so do you have different injectors?

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                        • #13
                          Also check jumper JP3 to make sure the link is on pins 2 & 3.

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                          • #14
                            Ian, I can confirm JP3 is at 2-3

                            The fuel system is stock with the exception of walbro fuel pump, perhaps the FP deviations have to do something with the sensor located BEFORE the fuel rails input? This is the best known location when running stock fuel lines
                            my FRP is stock too

                            I can also confirm my injectors are genuine ID, I think the AFR changes due to the ground offset issue with the LC-1 - last time I am using it, will be buying a decent wideband over the winter

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                            • #15
                              bumping my old thread
                              I've been working on few things in the off-season, redid fuel system, and most importantly I got one of those Lateral Performance intercoolers/radiators, that mimics old school WRC S5 cars, super short piping!

                              wondering if anyone can share a charge temp table that is meant for FMIC subarus that I could start with?

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