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IAT under or over blower?

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  • #16

    Re: IAT under or over blower?

    E85 versus methanol

    Incidentially, I agree with dieselgeek. I just like a wide degree of feedback before making any decisions. With respect to the IAT issue, BDS and Hilborne both install IAT's above the blower. Plus, I read a string elsewhere where a guy switched his IAT from below to above the blower and the car ran better on the street.

    Switching from E85 to methanol is NOT a simple task. Methanol is very corrosive and you must have special fuel tanks for it and all lines, regulators, etc. must be methanol compatible. Methanol is also more hygroscopic than ethanol. The complete fuel system should be flushed with gas when not in use. E85 is much more forgiving. I can run the same pump, lines, tank, with E85 as I do with race gas so I could switch between gas and E85 fairly easily.

    Pic of my set up (as MFI). Its not easy to see on this pic but basically the intake is low and two intake runner plenums are near impossible to put injectors on them.

    Click image for larger version

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    ed

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    • #17

      Re: IAT under or over blower?

      Bumping this thread.

      At startup, Ed's IAT's are insanely high at idle. Basically at coolant temp.

      The sensor is heatsoaked badly from the intake manifold. Gair at idle is less than 85%.

      Meanwhile the throttle body is sweating from the evaporating E85.

      I'm wondering if we can come up with a better correction method as I don't see much potential improvement in the IAT sensor placement; at least on the pressure side of the blower.

      Comments?
      Thanks
      Peter Florance
      PFTuning.com

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      • #18

        Re: IAT under or over blower?

        Agree with Peter that this is a real challenge for us. Conceptually, we agree with Scott but we cant get around the heat soak issue. We found a spot on the injector hat where we can place an IAT but because I am running e-85, the adiabatic cooling effect is pronounced. So, we would be avoiding the heatsoak issue and protecting the IAT sensor but we will now be in a coldsoak situation and still not getting the true temp. of the compressed intake charge. I would rather be getting corrections that will make it rich instead of lean in order to be conservative so above the blower would win out there. We really need some opinions here.

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        • #19

          Re: IAT under or over blower?

          Agree with Peter that this is a real challenge for us. Conceptually, we agree with Scott but we cant get around the heat soak issue. We found a spot on the injector hat where we can place an IAT but because I am running e-85, the adiabatic cooling effect is pronounced. So, we would be avoiding the heatsoak issue and protecting the IAT sensor but we will now be in a coldsoak situation and still not getting the true temp. of the compressed intake charge. I would rather be getting corrections that will make it rich instead of lean in order to be conservative so above the blower would win out there. We really need some opinions here.
          Could you make a phenolic insert to insulate the IAT body from the manifold to reduce head conduction to the element?
          Central TEXAS Sleeper
          USAF Physicist

          ROA# 9790

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          • #20

            Re: IAT under or over blower?

            Yea we discussed that idea too and I might be able to come up with something. Whatever it is it has to be sturdy and withstand heat, boost pressure, and be E85 resistant. I am sort of afraid to go dinkin with the intake and adding a phenolic insert not knowing if it will stand up to the conditions and screwing up my intake for nothin. I am wondering if we can just ball park-it by writing an algorithm for the correction by using the outside air temp, MAP, and coolant temperature?

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            • #21

              Re: IAT under or over blower?

              Im not very familiar with the software for MS, but isn't there a start and after start fueling vs. temperature table that can be adjusted for your unrealistically high IAT at startup? The IAT value should drop pretty rapidly once the motor starts, so you could adjust the hot start to de-compensate for the high IAT a bit once you charachterize the IAT thermal constant... The BS3 unit I run can do that...
              BKB
              Last edited by BKBridges; May 20th, 2014, 01:25 PM.
              www.FBthrottlebodies.com
              Bruce K Bridges

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              • #22

                Re: IAT under or over blower?

                BK, once I am operating at something beyond idle I DO think that the IAT will come down. The heat soak seems to be problematic restarting after it has sit without cooling down and during longer periods of idle. I think Peter can probably come up with a way to fudge it but I am not smart enough yet.

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                • #23

                  Re: IAT under or over blower?

                  Im not very familiar with the software for MS, but isn't there a start and after start fueling vs. temperature table that can be adjusted for your unrealistically high IAT at startup? The IAT value should drop pretty rapidly once the motor starts, so you could adjust the hot start to de-compensate for the high IAT a bit once you charachterize the IAT thermal constant... The BS3 unit I run can do that...
                  BKB
                  Really it's a problem on this car at any low mass flow (idle, after start etc).
                  I think a table of load vs. IAT correction might do it. May be tough sell to get added to MS2 though; he may need to upgrade to MS3 to get it.
                  Peter Florance
                  PFTuning.com

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                  • #24

                    Re: IAT under or over blower?

                    Peter, I am going to machine a piece of phenolic plate to fit into the air-bleed on the hat (above the blower) so we can at least experiment with the IAT above the blower. The air-bleed is already there and it shouldnt take much to machine the adapter. If it doesnt work out, I'll just put the air-bleed plate back in.

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