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Last Post 15 Jul 2014 01:14 PM by  shallam68@gmail.com
STS legal Miata engine management
 3 Replies
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New Member
New Member

03 Jul 2014 11:51 AM
    I'm having trouble navigating all the STS and MegaSquirt websites and forum threads on this. I looks 
    like things are easier than a couple years ago with the emissions stuff. It seems like the people that
    were building these have moved on to other projects. 

    I have a 1990 Miata I am building for STS.

    What's needed to stay withing the rules now? Just a Megasquirt in the ECU case?  The way I understand it, you can only use OEM sensors that came on the car, and you are allowed to replace everything in the ECU box. 

    If this is the solution, what actually needs to be done? 
    -Buy or build a megasquirt (what is needed? MS1, MS2, Microsquirt?)
    -Mount it in empty ECU box
    -Create a plug compatible connector to wiring harness
    -Determine a base map (how?)
    -Take it to a tuner for dyno tuning

    Are there other parts of the rules to be concerned with other than 14.10.F? Are people moving away from this? Are there other solutions now? 


    For reference:
    14.10.F The engine management system parameters and operation may be
    modified only via the methods listed below. These allowances also
    apply to forced induction cars, except that no changes to standard
    boost levels, intercoolers, or boost controls are permitted. Boost
    changes indirectly resulting from allowed modifications are permissible
    but directly altering or modifying the boost or turbo controls,
    either mechanically or electronically, is strictly prohibited. Traction
    control parameters may not be altered. Any OE OBD2 or newer communications
    port functionality must remain. The Check Engine Light
    (CEL) or Malfunction Indicator Light (MIL) may be disabled via software.
    Alternate software maps which violate these restrictions may
    not be present during competition, regardless of activation. Only OE
    sensors may be used for engine management.
    1. Reprogrammed ECU/PCM (via hardware and/or software) may be
    used in the standard housing.
    2. Supplementary (“Piggyback&rdquo ECU may be used subject to the
    following restrictions:
    a. Connects between the standard ECU/PCM and its wiring harness
    b. Must be plug-compatible with the standard ECU/PCM (no splices).
    3. Electronic components may be installed in-line between an engine’s
    sensors and ECU/PCM. These components may alter the
    signal coming from the sensor in order to affect the ECU/PCM operation
    of engine management system. Example: fuel controllers
    that modify the signal coming from an airflow sensor.
    4. Fuel pressure regulators may be replaced in lieu of electronic alterations
    to the fuel system. It is not permitted to electronically
    modify the fuel system AND replace a fuel pressure regulator.
    5. Ignition timing may be set at any point on factory adjustable distributor
    ignition systems.
    2015 SCCA® National Solo® Rules — 87
    14. Street Touring®
    6. VTEC controllers and other devices may be used which alter the
    timing of factory standard electronic variable valve timing systems.

    New Member
    New Member

    07 Jul 2014 10:41 AM
    Now that you can do a piggy back computer setup there is not alot of reason to put a mega squirt inside of the old ECU since that takes alot of time and effort. With the OBDII miata's the AEM FIC is a popular option that seems to work well and be fairly user freindly, the only issue is that it won't allow you to raise the red line. There is alot of information on this in the miata.net site as I recall. Hopefully this helps to steer you in the right direction.
    New Member
    New Member

    07 Jul 2014 11:12 AM

    I just saw a MS ECU that should work for you in the classified section.



    New Member
    New Member

    15 Jul 2014 01:14 PM
    Sorry for the delayed reply- off the grid last week.
    That listing is what prompted my question. I'm comfortable with a soldering iron and was trying to decide if I would rather pay more for someone else to build it or if I should do it myself. I think I'll wait for now and do more ms research.
    You are not authorized to post a reply.

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