Megasquirt and getting started

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Megasquirt and getting started
By Andy Whittle and Peter Florance

Decision Time
•Think about what problem you are solving by building this system. The answer to above will help you decide everything else below
•Fuel, ignition or both
–Fuel-only easier for newbies.
•Injection Method
–Single point injection (throttle body).
–Multi port (individual injectors).

Trigger Decisions
•Trigger Method
–Distributor, Generic Toothed Wheel, OEM Wheel or CAS
•Trigger Sensor type
–Points, hall, optical
–VR

Code Decisions
•Choose a code and or platform
–MS1-B&G
•Runs on MS1 chip. Fuel only
–MS1 Extra
•Runs on MS1 chip. Spark, fuel and extras
–MS2
•Runs on MS2 Daughterboard and and soon Microsquirt.
–Ms2 extra –
•Runs on MS2 Daughterboard (and Microsquirt?)

Packaging
•V2.2
•V3.0
•V3.57
•Microsquirt

Sensor Decisions
•O2 Sensors
–Wideband
•Accurate at wide range of AFR’s
•More expensive than narrow-band and can be finicky
•A must for forced induction; desirable performance applications
–Narrow-band
•Cheap, probably came with your car
•Only accurate at 14.7:1 otherwise only reads richer and leaner

Sensor Decisions, continued
•Coolant Temp Sensor
–OEM with pull-up resistor
–OEM with Easytherm
–GM (works with all codes)*
•Manifold Air Temp Sensor
–OEM with Easytherm
–GM (works with all codes)*

* GM sensors are Best for newbies
More sensors
•Throttle Position Sensor
–Careful, many throttle switches look like sensors
•Map Sensors
–250kpa –standard on V3.0 V2.2
–300kpa and 400kpa -optional

What to get
•Purchase a stim.
–The only way to learn the code and the tuning
•Timing Light
–A must for ignition setup; old non adjustable type works best with wasted spark
•Fuel Pressure Gauge (consider extending with hose to be viewable from passenger compartment during test.
•Voltmeter
–12V test light also useful
•Laptop with serial port
–Careful with USB adapters; check sticky list on MSEFI

Research and prep
•Get dyno curves or data from similar setup if possible
–Use for setting RPM bins
•Pick Injectors
–Use for choosing injector size (see Megamanual or check http://www.ncs-stl.com/fuel/ReqInjectors03.xls" onclick="window.open(this.href);return false; (very good for high RPM/high output applications where ‘turndown’ is important.
–Tip -find injectors off motor of similar size, # off cylinders and HP
–High/Low Impedance (Z) Injector
•Better ground needed for Low impedance
•Start with known running car
–Worst case-install many engine mods and Megasquirt at the time with not step by step testing.

Wiring
•Clean, waterproof wiring.
–Correct terminals and tooling for those terminals
•Wire colors and quality
•Wire routing.
•Step by step db37 pin verification before applying power and trying to start it. (See Peter’s checklist below)

Typical Wiring DiagramHarness made of low cost Auto-parts store components
Custom engine harness for BMWPeter’s First time wiring checklist
1.Find your wiring diagram
2.Disconnect the Squirt from the DB 37 (37 pin gang connector )
3.Check for fixed resistance to ground on 20 21 26 (around 3500 ohms depending on temp)
4.Check for resistance to ground that increases with throttle movement on 22 about 100ohms sweeping to about 4500 ohms
5.Turn key power on
6.Check pins 28, 32-35, 36 37 (and other ignition coil connections, boost, fan or other control device pins, if used) for 12 volts power
a)(I used meter as I was fairly confident; test-light to gnd would be better) Fidle pin 30 should be included if used.
Startup checklist continued
7.Check pins 28, 32-35, 36 37 (and other ignition coil connections, boost, fan or other control device pins, if used) again while cranking to make sure power is still there during cranking
8.Check to make sure there is no power on any other pin (test light still to gnd) Check for gnd (test light from +12v to tested pin) on pins 1-2 7-19
9.Connect Megasquirt to the DB37 and turn key on. Verify fuel pump runs and stops in two sec.
10.Connect laptop and check MAT, Coolant and TPS sensor.
1.Datalog this process and view it with Megalogviewer

Startup checklist continued
11.Check Map Sensor
a)See Table to right
12.Calibrate TPS in Megatune, noting Idle and WOT TPS ADC values in your log or other documentation -you'll need these later.

Startup checklist, continued
12.If you have a trigger wheel and MS1 Extra, check tooth values with Megatunix Tooth Logger. Crank with Trigger Logger to make sure that the trigger times are clean and even -they were except nice sine wave from compression.
13.Turn on fuel pumps but do not start it, check for fuel leaks
14.Start it, check for leaks and check Timing so that it matches what Megatune thinks the timing should be. See trigger angle to sync the Squirt to where the crank trigger wheel really ended up.
15.Check for RPM and sensor noise in the early datalogs (above). Datalog everything!
16.Posting for help? Please include datalog, msq and basic installation details.

All this, except the trigger angle, should take less than one hourTuning
•Speed density, Alpha-N, and MAF. How will I ever decide?
•Do I need to have target AFRs in some sort of table?
•Verify timing real early and often.
•Basic tuning early
–Stable RPM a must! Do not tune with a noisy RPM signal.
–Get VE table close before making other adjustments
•Getting it to start and a reasonable pulse width
•Backfiring on overrun, is it lean or is it rich?
•All o2 sensors get real confused with a dead miss.
•When does the motor need to start getting rich?
Tuning, continued
•Tuning for mileage? Is this the same thing?
More Tuning Why Acceleration Enrichment is necessary;There are a few that we have to consider. (Hang with me here)
1) You may remember from high school physics that water will boil at close to room temperature if you pull enough vacuum on it. Conversely, if you apply pressure you can raise the boiling temp up to 250F or more. 2) Water on the driveway always evaporated faster on a windy day than it does on a calm day. 3) Water on the driveway always evaporated faster on a hot day than it does on a cool day. 4) If you leave a cold glass of beer on the counter water droplets form on the side of the glass, apparently water from nowhere. 5) Cold air has more oxygen molecules per cubic foot that hot air. Acceleration Enrichment, continued
6.An intake manifold has a constantly changing air properties changing the amount of fuel that can condense on the walls.
7.Fuel in the intake constantly collects on the inside walls of the intake.
8.The amount (thickness) of this layer of fuel is constantly changing.
9.The earlier the fuel is injected in the intake airflow, the more area of the intake wall can get wet.
10.A VE table as we in the MegaSquirt world is designed to balance the amount of fuel delivered from the injectors with the air flow. The internal math of the MegaSquirt estimates this airflow and in turn calculates the matching injector pulse width. This airflow calculation is based on intake air temperature, RPM, intake manifold absolute pressure (KPA), and RPM.
Acceleration Enrichment, continued
11.An intake manifold often has hot water in it. This manifold is attached to hot things and is being blown on by constantly changing amounts of hot air coming off of the radiator and from the exhaust system.
12.Back pressure on the exhaust, weather caused buy high atmospheric pressure at the end of the exhaust system or by trying to flow too much exhaust through the system causes the motor to need less fuel.
13.The injector delivers fuel only after it has opened. The injector opening time consists of about the first 1.0 millisecond of the pulse width. So if MT reports 10 ms pw1 the injector is only supplying fuel for about 9 ms. This is a big deal if you have a cruse pulse width of say 4ms and your AE added PW is 6ms. The amount of fuel delivered goes from (4-1) or 3ms of fuel to (4-1)+6 or 9ms or three times the fuel. Plenty of fuel to put out the fire.
14.Way too much fuel feels just like way too little fuel from the driver’s seat. (the fire goes out
15.Fuel constantly collecting and evaporating in the walls and floor of the intake behaves much like the water based examples above.
Beyond Basic Installation
•Router boards, sequencer…
–What about all this cool stuff.

Helpful gadget
DB37 Rear Mount Screw Termination Board
Description
The ADAP37 is a DB37 Screw Termination Board that mounts directly to the rear DB37P connectors on most I/O boards. Popular where no ribbon cable is desired and room for external mounting is limited. Rear of board is shielded to prevent shorting accidents.