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Mass Air v/s Speed density

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  • Mass Air v/s Speed density

    It seems like a lot of the custom EFI set ups use speed density, but most OEMs use Mass Air. What are the pros and cons of each? Can you use mass air with Mega Squirt? I am not trying to stir anything up, just want to learn.
    http://www.bangshift.com/forum/forum...-consolidation

  • #2

    Re: Mass Air v/s Speed density

    Re: Mass Air v/s Speed density

    Mass air flow (MAF) sensors do a good job a measuring exactly how much air is in the system, but even the big ones usually aren't large enough for most aftermarket horsepower levels. The sensors are expensive to make compared to just a vaccum and temperature sensor (speed density). So even if you get a large enough MAF for your application, if you decide to step up to more HP, you may need a new expensive MAF. Where as speed density you can put the largest throttlebody you can find (or reasonably use) and as you step up Horsepower (new cam, heads, exhaust, etc) the fuel and EFI side of it doesn't need to upgrade anything (as long as your injectors also had extra capacity early on, which you'd have to upgrade too with a MAF system if you sized them too small for more HP). Speed Density is a lot more forgiving with upgrades.

    OEM's use them primarily for emission requirements, to know exactly how much air is flowing into the engine, even before the O2 sensors warm up enough to start providing feed back. And yup, megasquirt has settings to work with them.
    Escaped on a technicality.

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    • #3

      Re: Mass Air v/s Speed density

      Re: Mass Air v/s Speed density

      Randal pretty much nailed it.

      I think the reason why all the aftermarket standalone EFI systems are Speed Density is because it's so easy to make the changes for parts upgrades, there's no point for a MAF really. Also, a MAF can be a huge air restriction depending on the application.

      Meanwhile, there are guys out there who SWEAR by their MAFs - mostly megasquirt guys - a MAF is a really awesome way to run a two stroke engine, all the jet ski guys are running them.

      www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

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      • #4

        Re: Mass Air v/s Speed density

        Re: Mass Air v/s Speed density

        Randal pretty much nailed it.

        I think the reason why all the aftermarket standalone EFI systems are Speed Density is because it's so easy to make the changes for parts upgrades, there's no point for a MAF really. Also, a MAF can be a huge air restriction depending on the application.
        That, and an aftermarket ECU company only needs to stock three or four MAP sensors. You'd need to keep a lot more different MAFs around.

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        • #5

          Re: Mass Air v/s Speed density

          Re: Mass Air v/s Speed density

          Randal pretty much nailed it.

          I think the reason why all the aftermarket standalone EFI systems are Speed Density is because it's so easy to make the changes for parts upgrades, there's no point for a MAF really. Also, a MAF can be a huge air restriction depending on the application.

          Meanwhile, there are guys out there who SWEAR by their MAFs - mostly megasquirt guys - a MAF is a really awesome way to run a two stroke engine, all the jet ski guys are running them.

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          • #6

            Re: Mass Air v/s Speed density

            One more decision maker

            Click image for larger version

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ID:	854533I agree with all of the above. Additionaly, design wise, MAF sensors usually end up as a round tube. The round tube leads to the big hose. A properly sized MAF hosed into a properly sized throttle body works well. But, in some applications it kinda ruins the vibe.
            Attached Files
            Last edited by BKBridges; April 18th, 2011, 08:54 PM.
            www.FBthrottlebodies.com
            Bruce K Bridges

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            • #7

              Re: Mass Air v/s Speed density

              Dang - that is pretty stuff right there.
              Flying south, with a flock of bird dogs.

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              • #8

                Re: Mass Air v/s Speed density

                As was mentioned, SD gives you a lot more freedom in packaging the intake system. With blowers, turbos, stacks, etc. you are not restrained by a MAF.


                (Why is stacks repeating? I only typed it once)
                Last edited by Arrowhead; April 20th, 2011, 05:35 AM.
                http://sites.google.com/site/arrowheadshotrodsite/

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                • #9

                  Re: Mass Air v/s Speed density

                  stacked stacks

                  Dang - that is pretty stuff right there.
                  Why thank you! Speed density made it all possible (and my mom)
                  Bruce
                  www.FBthrottlebodies.com
                  Bruce K Bridges

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