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TPI Question

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by 72Blazerod, Oct 5, 2001.

  1. 72Blazerod

    72Blazerod 1/2 ton status

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    I have a lead on a 1991 Camaro 5.7L TPI engine with all the bits and pieces. The guy who has it keeps saying that it is a "speed density" engine. Does anyone know exactly what this means? I take it it is something good because he keeps mentioning it. Any info would be appreciated.

    Thanks,

    Rod

    <a target="_blank" href=http://communities.msn.ca/72BlazerodsOldChevyTruckPage/photoalbums.msnw>http://communities.msn.ca/72BlazerodsOldChevyTruckPage/photoalbums.msnw</a>
     
  2. BobK

    BobK 1/2 ton status

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    The speed density is a little more desireable than the MAF system(Mass Air Flow).Here is a link to some good info. on TPI systems.It has definitions of the speed density and MAF systems.
    <a target="_blank" href=http://www.jimsperformance.com/portinj.html>http://www.jimsperformance.com/portinj.html</a>

    <font color=green>BobK<font color=green>
     
  3. Steve_Chin

    Steve_Chin 1/2 ton status

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    The MAF systems measure the mass of the air going into the throttle body, where the Speed-Density systems calculate the mass of the air going in by measuring the manifold absolute pressure, inlet air temperature (thus crudely calculating relative air density), and engine speed. Both measure the position of the throttle blades and engine speed in order to determine the proper amount of fuel to deliver.

    There really is no real benefit to the Speed-Density systems other than packaging and a slight increase in the cross-sectional area of the air inlet in front of the throttle body. The MAF systems are more flexible in that you can make some modest changes without having to recalibrate the PROM. Any changes to an engine that increase the airflow or change timing events (i.e. cams, bigger intakes, ported heads, headers, high ratio rockers, etc.) would require recalibration of the PROM on a Speed-Density setup.

    FWIW, GM changed from MAF to Speed-Density on the TPI systems in '90. In '94 GM went back to an MAF system with the LT-1/LT-4 and continues with MAF systems on the LS-1/LS-6.
     
  4. BurbinOR

    BurbinOR 3/4 ton status

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    Speed density allows you to get a little crazier with the motor/cam. MAF was the original method till they went to Speed Density. Check my response to you on the other post for more info on the net than you can digest. I have Speed Density TPI on my 406...........not even close to stock and it screams.

    <font color=blue>'79 ONE TON TPI K5 - See it at---&gt;<a target="_blank" href=http://www.blazzinor.rockcrawler.com>www.blazzinor.rockcrawler.com</a>
     
  5. Steve_Chin

    Steve_Chin 1/2 ton status

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    The Speed-Density system is *easier* to get a little crazier with the engine and cam because it lacks the obstruction presented by the MAF, but the MAF can be modified to allow enough flow to move a reasonably large engine with big heads and a big cam, according to TPiS. The downside is that the Speed-Density system does require reprogramming of the PROM when changing just about anything that increases air flow through the engine (other than the air filter). Either system should work well, provided it is set up properly for the rest of the engine combination.
     

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