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  • IAT under or over blower?

    OK EFI guru's, I am a newbie. Here is my project:

    65 chevy II with an odd-fire, 280 CI chevy v6 for pro-street! Blown with a 4-71 and bugcatcher injector. I am converting it from a MFI to EFI (never could get the mechanical FI to work very well) . I will be running E85, injectors will be above the blower on the hat. I just purchased an MS2 from megasquirt (controlling fuel only). SO.... first of what will likely by numerous questions: Should the IAT be below or above the blower? I am getting mixed opinions from the major EFI folks. Anybody running EFI with a blower that can help?

    ed

  • #2

    Re: IAT under or over blower?

    Under the blower. If any "EFI expert" tells you that you want it above the blower, dismiss them as inexperienced and don't listen to them anymore.

    The ECU needs to know the temperature of the incoming air charge so it can compensate. A blower like yours puts a TON of heat into the incoming air charge, easily tripling the ambient air temp with any amount of boost. That means the fuel quantity needs to change pretty dramatically to keep the same AFRs you're aiming for.

    Let me know when you are getting set up, there are some default parameters you will want to change in your microsquirt. You also might want to install the MS2-Extra software on it, as it's easier to use than the B&G firmware that comes on it by default. I/we can help you with that.

    How soon are you going to have it installed and ready?
    www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

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    • #3

      Re: IAT under or over blower?

      Wow. Thanks for the quick reply! Regarding the IAT...thats what I thought but more than one source stated that since I am injecting above the blower, there were issues with the IAT being exposed to both fuel and air for correct readings.

      Anyway, I have not received the megasquirt yet. Should arrive anyday. The bugcatcher is being converted from the mechanical injectors to the electronic injectors by Fox Engineering. He is also installing the TPS on the hat as well. So, I have plenty of time. The first thing I need to do is get all the sensors set up on the motor. Then, when the hat comes in, I can get ready to wire everything up. All comments, suggestions, etc. warmly welcomed and received.

      THANKS!
      ed

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      • #4

        Re: IAT under or over blower?

        Something else you may want to consider if you want the engine to have good drivability, is NOT using the up-high injector placement.

        Your best bet is to put the injectors down low as close to the intake valve as possible. given that it's a roots blower, a small percentage of fuel needs to be run through the blower (rule of thumb is 30% of your total fuel load shuld go through the blower to lube it).

        The reaosn for this is because with up-high injectors, whenever you stab the throttle the incoming air will reach the cylinders before the fuel can get there. You'll end up with a very bad tip-in stumble until the fuel gets to the chambers. There are a few workarounds, you can run the engine super rich at idle and the excess fuel becomes available for tip-in (same way the Mechanical Fuel Injection guys do it), this minimizes the stumble but it's not my first choice.

        Will this be a driver or a show car?
        www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

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        • #5

          Re: IAT under or over blower?

          also, getting fuel on the IAT sensor is no problem at all. You WANT the temp sensor to know the temp of the incoming air and fuel charge.
          www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

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          • #6

            Re: IAT under or over blower?

            DG,
            The old school blower needs some love (lube) from the fuel if its not a dry "sealed" unit...kind of neccesitating some injection above the lobes. Above and below is usually the optimal set-up. Since its a V6 the MS2 off the shelf should be able to run 6 below the blower and two on top...2 18lb units on top for lube and 6 of whatever size meets the HP target below. The pic is from Rich's website wwwfastmanefi.com
            BKB
            Attached Files
            www.FBthrottlebodies.com
            Bruce K Bridges

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            • #7

              Re: IAT under or over blower?

              DG,
              The old school blower needs some love (lube) from the fuel if its not a dry "sealed" unit...kind of neccesitating some injection above the lobes. Above and below is usually the optimal set-up. Since its a V6 the MS2 off the shelf should be able to run 6 below the blower and two on top...2 18lb units on top for lube and 6 of whatever size meets the HP target below. The pic is from Rich's website wwwfastmanefi.com
              BKB
              All, thanks again. Yes, the blower needs some fuel to lubricate the lobes. When I was running MFI I had to run it rich because of the momentary lean condition to which you refer whenever I went to WOT. There is a slight logistical issue running any port injection: the intake manifold I am using is the only production v6:4-71 made (from BDS) and does not have provisions for injectors on every intake runner. I can send you a pic later to clarify. My application will be mainly street/shows with a routine visit to the track when the mood strikes me.

              ed

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              • #8

                Re: IAT under or over blower?

                Unless your orig manifold is too dear to modify, you should be able to squeeze some bungs for the injectors in there for driveability. It will make it a driver rather than a sort of driver...
                BKB
                www.FBthrottlebodies.com
                Bruce K Bridges

                Comment


                • #9

                  Re: IAT under or over blower?

                  Dieselgeek, this is beginning to sound a lot like a straight 8 Buick project.

                  Comment


                  • #10

                    Re: IAT under or over blower?

                    dieselgeek, this is beginning to sound a lot like a straight 8 buick project.
                    lmao
                    I'm still learning

                    Comment


                    • #11

                      Re: IAT under or over blower?

                      Thanks all. Thought you would like to see a response from one of the professionals at Kinsler:


                      Hello Ed,

                      It is best for to measure the "Charge Air Temp" when possible to obtain the best engineering data.

                      The being said, you will need to recognize that the air temp sensor located below a supercharger will "Heat Soak" after the engine has been run and shut down. During a warm/hot restart, you will need to be able to compensate for the "Hot" reading and reduction of fuel injection during the re-start. We have had some applications where the sensor got damaged due to high charge temperatures.
                      If you run the engine at modest loads, and not high sustained loads, you should not have any issues.

                      In reality, if you are not concerned with "Engineering Data" but rather just want a simple tune and consistent running, you can install the sensor at the supercharger inlet. Provided you don't plan on changing superchargers or altering the drive ratio significantly, then the temperature rise on the outlet of the supercharger will remain fairly consistent and you will be able to obtain decent results with the sensor in the incoming air. If the incoming air changes, the outlet temp will also change.
                      Hope this helps.

                      Earl Miller
                      Kinsler Fuel Injection

                      The folks at Kinsler have always been pretty good and his response is logical in my mind. I will be running E85, not gas, so I think my intake charge will be fairly manageable at 8-10 PSI boost.

                      ed

                      Comment


                      • #12

                        Re: IAT under or over blower?

                        Well, based on my experience, Kinsler's method will end up running no better than a carburetor.

                        Meanwhile, don't you want to know the real temperature under your blower? 20psi can easily reach over 250 degrees fahrenheit (a 10-71 at 17psi on a 500" Barton Hemi did this).

                        Before I give a lecture though, what fuel did you plan on running?
                        www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

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                        • #13

                          Re: IAT under or over blower?

                          I plan to run E85.

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                          • #14

                            Re: IAT under or over blower?

                            two answers..
                            is there a way to get two readings?

                            I have an 80s subaru that did two readings. cold air at intake plenum and hot at the intake.

                            no turbo anywhere. (but could of course)..those still run today mind you.
                            Previously boxer3main
                            the death rate and fairy tales cannot kill the nature left behind.

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                            • #15

                              Re: IAT under or over blower?

                              Well, I guess it'l be a matter of opinion, but i don't consider the IAT down low as "Engineering Data" - think of it this way, what happens to the oxygen content in the air charge if you heat it to 3x it's ambient temperature? The Kinsler guy isn't necessarily wrong, but I believe in letting the EFI system do what it needs, after all that's why we choose to run EFI yes? A big part of the Ideal Gas Law - critical math inside an EFI ECU - is temperature.

                              Meanwhile, I think you will WANT to know if you're hitting 250+ degrees intake temps (which you may at that high of a boost), and at that point you will at least know that e85 is nowhere ready for those kinds of intake temps without hurting parts in the engine. Maybe run methanol at the track? and e85 on the street? switching tunes will be easy with your combo. Heck why not a pump gas tune for low RPM cruising and getting home safely if necessary.
                              www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

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