Original Information

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   20B Rotary Engine Info


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Power FC Information


Allows complete control of ECU functions.

To properly tune, datalogit and wideband O2 Sensor recommended


Basic Facts on Power FC


Controlling the ECU and engine basics

This pertains mostly to the Commander for the directions on it are obscure and do not instruct those who purchased it.

All units are in METRICS

1) There are three main screens that come up when the PowerFC is first powered.  1. MONITOR  2. SETTING  3. ETC.

The first is, MONITOR.  Once the engine is tuned correctly, your PowerFC Commander is used to MONITOR all of the data given to the ECU.  It monitors air temperature, water temperature, Engine RPMs, fuel output, ignition timing, and boost pressure based off of the electrical signals outputted from each Sensor located in the engine bay.  The Commander can give the information in numerical format (i.e. 724 RPMs, 82 deg C) and updates that for real time sensor data.  As with most engine monitoring there are features that may appear frivolous, but a more thorough understanding of the engine will make any tuner appreciate them. 


The second screen is SETTING.  It is were all of the tuning is done on the hand held Commander.  There are two things to understand when manipulating a cars fuel and timing, Load vs. RPM and Leading/Trailing Ignition.

Fuel Maps (Load vs. RPM)


That is an example of a mildly upgraded "Fuel Map".  It is what I use actually.  When I first installed my PowerFC I couldn't of told you the first thing about this map.  There are three main components to this map.

A)    It is a table that corresponds to the amount of fuel the car must output at certain times.  The values in that map are percentage corrections (145 or 1.45 means the injector on time is multiplied by 1.45).  For some, the numbers in the graphs are actually time in milliseconds the fuel injector is opened.  (those graphs have values from .3ms-23ms)  Another way of graphing fuel output is by the injector duty itself (Injector duty is the rate of flow as a percentage)  At a constant fuel pressure the increase in time open equals an increase in amount of fuel dispensed. 

B)    The first amount that is used to calculate fuel output is Intake Air Pressure AKA LOAD.  In other words, How much air, at this moment, is going into the engine per square inch?  The zero on the graph is the load equal to atmospheric pressure.  (On NA cars this is achieved at WOT)

C)    The second variable is engine RPMs.  More fuel is needed per second when the engine is spinning at faster speeds.

So, the amount of fuel that is needed at that moment is calculated on the speed of the engine and how much the air is compressed.

Detailed STOCK Fuel Map and Zones



Ignition Maps (Leading/Trailing)

On a rotary engine the ignition cycle is totally different than it's piston counterpart.  Since the chamber in which the gas is ignited is in the shape of a crescent, there are two spark plugs on each end of it.  This maximizes the combustion of the fuel.  (some rotary engines have three points of ignition) 

There are two maps which look similar to the previous one.  Each control when the two spark plugs will fire.  The plug located higher on the engine is known as the Trailing plug because in the ignition cycle it is at the rear end of the compressed air/fuel mix.  The bottom plug is known as the Leading for reasons stated prior.

One thing to remember: There are actually two sparks coming from the leading spark plug for each combustion.  The second is known as a waste spark.  It not only burns the last of the fuel but also happens to coincide with the first spark of the other rotor.  The leading plugs always fire at the same time every time.

There are three tables to adjust when referring to ignition timing.  IGL, IGT and Split (IGL - IGT).  Split is the difference between leading (IGL) and trailing (IGT) ignition. Leading should always fire before trailing, so you want to see positive numbers or zero. Negative split occurs when this gets reversed and trailing fires before leading. (rx7.HomeIP.net)

Go to the Wide Band O2 page for more detail on tools used in tuning.


Ignition Timing Map (Leading Plug)

That is an example of a Ignition Timing Map for the leading spark plugs.  The map is once again measured in RPM vs. Load.  This time, the units of data is degrees.  A positive number is in degrees ATDC (After Top Dead Center).  Negatives mean BTDC (Before Top Dead Center)

Example of TDC


The general rule of thumb is to tune the Ignition Timing Maps while on a dyno.  The goal is to obtain the most HP without subjecting the engine to detonation.  Typical tuning advances the timing until knock is detected.  At that point, the timing is retarded 2-3 degrees for safety and longevity.

The third option is ETC. which contains miscellaneous features.  The version of the PFC can be checked here.  A unique display screen of all the sensor operations and voltages can be selected under Input Output Check Display.  Original Function Setting has advanced functions that are rarely used in normal operations.  LCD/LED adjust allows the user to adjust the backlight and display.  All Data Init DO NOT enable this unless you are reverting back to original maps and states.  This is a "reset" button.






Owning a PowerFC

After reading the bits and pieces of information from www.rx7club.com/forum  I decided to stop by the local RX-7 shop to investigate further.  Chris Sanders from Banzai Racing gave me more than enough information to judge when the Power FC would be right for me.  My first thought was to hold off modifying my car that much until another year or so.  Temptation got the best of me and I ordered both a FMIC and the Power FC at the same time.  My car has had a unique history as do most RX-7s.  I had a brand new engine installed back in Jan 03 and the car was for the most part stock exceptions being a HKS BOV, down pipe and Apexi N1 Cat back.  It is most commonly accepted that no more than three engine mods can be done before ECU modification must occur.  After having the car back for a while I noticed my main catalytic converter was falling into pieces causing rough and varying idle.  I then replaced that with a High Flow cat to try and stay in the safety zone of upgrading.  It was not long before that was no longer satisfying. 

I wanted a better ECU.  The options being: a remapped stock ECU, the Power FC, and Haltech ECU, the three most popular choices.  I read that the Haltech required a premix of oil and gas because it doesn't have oil metering control.  I know I would fail to remember mixing every time I fill up so that was off my list.  The remapped ECU was almost as much as the PFC and I loved the idea of tinkering so I purchased the Power FC.  To more than meet the three modification limit I also bought Airinx air filters and the Blitz Front Mount Intercooler.

I assumed that there would be constant tinkering necessary to operate a vehicle with a PFC.  I purchased the unit with the commander, the handheld display, with the thought that it would be needed to tune my engine.  I bought my setup from SRMotorsports with upgraded maps used on cars with the similar number of modifications.  *Although this is highly not recommended*  I was too stubborn to have an expert tune my car. 

My FMIC was not shipped when I got my Power FC.  I was so eager to try it that I risked my engine's safety to see what would happen.  After disconnecting the battery, I removed the passenger side kick panel and found the ECU in the back corner.  I removed the many screws that anchor the computer to the vehicle.  The PowerFC doesn't come with threads holes for screws, only two sides of Velcro with adhesive on the backs.  For most, the setup is to "piggyback" the PFC to the stock ECU.  This doesn't allow the kick panel to sit in it's proper position.  I chose to replace the stock ECU completely.  To get the Commander plug (which looks a lot like a PS/2 port) to fit while mounting the PFC in the stock location, I had to cut one of the brackets to allow for the increased accessibility.  I ran the cord for the Commander under the rug and at that point it becomes obvious that a mounting bracket would be nice for the commander.

I then plugged the battery back in and got in the driver's seat.  I turned over the engine and without any noticeable hesitation the engine came to life. The car revved sharply and slowly sank down to approximately 1500 RPMs.  For about five minutes the car did random things like bounce from 1000 to 1800 RPMS and creep in Idle speed.  After the car warmed up to about 80C another two minutes passed before the car dropped to 800-900RPM idle.  (my installation was plagued with broken rubber hose vacuum leaks and, after getting the GReddy elbow, the Accelerated Warm-up line had been disabled and also had a substantial leak.)  I took it for a slow test drive after idling for about 15-20 minutes.  I felt as if the car was learning how to react to the load and RPMs that I gave it.  (It was learning)  After 10 minutes of slow cruising I then gave it some gas.  There was VERY noticeable difference from the stock ECU to this setup.

I repaired all of my vacuum lines.  Chris from Banzai had located many reasons why my Idle wasn't at the 720 RPM mark.  One serious reason being that the engine made a clicking noise like a overactive solenoid.  This was in fact a spark plug wire that had separated and the sound was the spark streaking across a 3/4inch gap in the wire to the plug connector. 

One thing that the car cut back on doing was the excess backfiring that was happening without the PowerFC.  The engine ran smooth and boosted the correct 10-8-10 PSI pattern.

Every time I change something on the engine (i.e. oil change, air filter cleaning, spark plug wires) the ECU seems to relearn the system and runs a little rougher that normal.  This subsides about 5 minutes later and the car behaves perfectly.

The only unexplainable issue I have had was cruising at about 55MPH  (90C engine temps) My car, when shifting gears, would rev to redline.  When in gear the car would accelerate as much as possible.  I have had throttle cabling problems similar to this in my 1988 GXL and the entire line was is correct position.  I shut down the car twice and restarted it and the problem disappeared.

This site is meant to give information related to the 1993 (o)Mazda RX-7 Twin Turbo.  Anything from rotary engines to wiring diagrams and turbo upgrades to tuning info, this site has it all! efini 93 rx7 13b anfini Turbo RX-7 Turbo RX7 turbo rx7 rx7tt rx-7tt  As well as the Rotary Engine Pickup Truck aka REPU repu