The Skyactive engine platform found in the ND MX-5 vehicles is a particularly complex system.  Throughout our development we’ve made an effort to balance our efforts in simplifying the tuning system, as well as offering RaceROM features in the limited free space available to us in the ROM.  This means our RaceROM offerings are slightly different than in other platforms as there are either simplified forms being used, or something altogether unique.

With a framework for the platform in place, we’ll be working with our dealers in order to balance the features for this platform, with the practical limits of the ECU.

The Mazda Mx-5 SkyactivG cars use a high compression (14.0:1) 1.8L or 2.0L 4 cylinder engine utilising direct injection with a high degree of freedom of cam timing on both inlet and exhaust cams.  This allows the engine to use many complex strategies to deliver high power and high efficiency for such a small capacity. The control system components are as below.

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Mazda have employed ion sensing technology to model per cylinder detonation, pre ignition and air fuel ratio and uses these in many of the airflow and ignition timing strategies to preserve reliability while maintaining a high as possible performance and low emissions.

Ion sensing involves measuring the electrical current flow after the spark initially bridges the gap between the center electrode of the sparkplug and the ground strap.  In the event of a misfire, no current flow can be easily detected, making it a fairly stable and accurate method of measuring misfires. 

The 4-2-1 type exhaust pipes have been adopted for the exhaust manifold to create an engine with a high compression ratio.

Two types of load and airflow estimation have been adopted for the intake air amount measurement to achieve stable combustion free from abnormal combustion.

• L-jetronic (The intake air amount is directly detected by measuring the amount of intake air flow using the MAF sensor.) MAF sensor adopted

• D-jetronic (The intake air amount is detected indirectly by measuring the intake manifold pressure (pressure between downstream of the throttle valve and intake manifold) using the MAP sensor.) MAP sensor adopted

• IAT sensor No.1 and No.2 adopted

To improve the fuel economy and emission performance, an electric variable valve timing control has been adopted for the intake side, and a hydraulic variable valve timing control for the exhaust side. The electric type is adopted for the intake side to achieve expanded valve overlap and delayed closing of the intake valve (enlarged intake valve opening angle). The Hydraulic Lash Adjuster (HLA) has been adopted to achieve the maintenance-free valve clearance.

• Intake side: Electric variable valve timing control with independent CMP sensor

• Electric variable valve timing motor/driver

• Electric variable valve timing relay

• Exhaust side: Hydraulic variable valve timing control with independent CMP sensor

Engine hydraulic pressure switching control (using Engine oil solenoid valve) has been adopted to reduce the oil pump operation load on the engine.

To improve engine reliability, an ion sensor has been adopted which detects pre-ignition.

Some other features Mazda have listed as advances with their SkyActiv technology are.

Sliding resistance reduction

• Rocker arm (with built-in needle roller bearing) adopted for cam-contact area

• Reduced valve spring load

• Narrowed down crankshaft journal

• Optimized piston skirt shape

• Lowered piston ring tension

• Lowered drive belt tension

• Suppressed chain tensioner load by stabilized timing chain behaviour

• Oil shower pipe adopted

Mechanical resistance loss reduction

• Optimized oil passage

• Optimized oil pump shape

• Engine oil control adopted

Cooling loss reduction in early stage of combustion

• Piston cavity adopted

Pumping loss reduction

• Variable valve timing mechanism adopted on both intake and exhaust sides for fine control of exhaust amount and internal EGR volume

Cooling efficiency improvement

• Air seal cowl and flaps adopted

• Optimized cooling fan shape

• Optimized engine coolant passage

• Optimized water pump impeller shape

Combustion efficiency improvement

• Multiple hole-type fuel injectors

• High-pressure fuel pump

ProECU software has been introduced to allow reprogramming of the factory ECU in order to tune the necessary components of the calibration in order to allow for modifications and increases in power.  This is not a standalone repalcement ECU so you shouldn't run into the associated issues or disadvantages of setting up a purpose-built ECU and control system from scratch.

The software allows easy control over most factory parameters including:

• Boost Targets and wastegate control

• Target AFR

• Ignition Timing

• Fuel Delivery including fuel pump calibration (using the same style pump as OEM)

• Airflow Measurement and fuel compensation

Ecutek offers full control of forced induction on SkyactivG cars.  As such we offer a well refined product that should be able to cope with the full range of forced induction and naturally aspirated modifications. We have also detailed some instructions on both of the example ROMs (NASP and FI) to help you tune these cars along with an example ROM to get you started. The YouTube video of the ECU Connect app highlights the advantages of packaging the tune with the EVI-BT and ECU Connect. 

Below are some links to the newsletters detailing the progress we have made on the product
• EcuTek release Mazda MX-5 ND RaceROM Update - http://mailchi.mp/ecutek/ecutek-release-mazda-mx-5-nd-racerom-update
• EcuTek release Mazda MX-5 ND RaceROM update for forced induct... - http://us7.campaign-archive1.com/?u=3293297053d29d26e037ea32b&id=9ae74a9f47
• EcuTek release Mazda MX-5 Skyactiv-G Retail kits - http://eepurl.com/bIa8ur
• EcuTek release Mazda MX-5 Skyactiv-G - http://eepurl.com/bHgUc5

You should be able to expect around a 15hp increase for NASP tunes and about 250hp in total for forced induction modifications.  See the dyno plots below to gauge the expected results for these types of modifications.

To get started there is an NASP example ROM and logs for the above power graph, these can be used to compare the results you achieve and the corresponding log from the stock ROM.

PSM4EB-example-v1-en...bin

tuned 182hp (1) (1).csv

stock 166hp (1) (1).csv

The key changes on the ROM are:

• Increased intake cam advance over 6000rpm where the stock ROM appears to deliberately reduce the intake advance in order to reduce power.

• Leaned out target AFR slightly

• Raised cat temp threshold to reduce temperature-based enrichment.

• Changed ignition maps to use just the base ignition map with increased advance.

• Raised rev limit to get a little more top end power.

Forced Induction example ROM is significantly more complex the Logs below show the changes between the stock and the modified vehicle.

• The key changes to the ROM are
  Increased intake cam advance over 6000rpm where the stock ROM appears to deliberately reduce the intake advance in order to reduce power.

• Leaned out target AFR slightly

• Raised cat temp threshold to reduce temperature-based enrichment.

• Changed ignition maps to use just the base ignition map with increased advance.

• Raised rev limit to get a little more top end power.

• Made the FI pressure multiplier map match the boost ratio profile of the turbo kit

• Use the neutral torque override to drive the torque and desired load

• Enabled RR speed density and used this to determine airflow when experiencing positive manifold pressure

• Used the throttle limit tables to improve drivability

• Disabled the EGT correction