I wonder if anyone knows the control program for the engine management system.

I assume it takes inputs from throttle position, air density, RPM, coolant temp, oxygen in the exhaust; maybe more things.

I assume it (a) sets spark timing; (b) sets duration of fuel injection pulse; (c) sets valve timing; (d) ??

Can anyone explain the algorithm that connects these input and output variables?

There are over 60 proprietary equations - all legal trade secrets.

The MAF uses a expontenial equation to translate the voltage into grams per second of air flow/{{ it takes roughly 0.75 grams per second per HP]

so a 278 HP Q might use 208 grams per second and the MAF can read up to 255 g/sec or 340 HP worth at 5.000 volts and at idle about 6 grams per second is consummed but the reading is 1.10 volts.

http://www.brownsword.ca/ecucoding.html

http://www.stealth316.com/2-air-fuel-flow.htm

http://www.ngml.ksu.edu/classe...s.PDFh ... g/diy_efi/

Those are interesting references.

What does the Q computer control besides timing and fuel? Is the valve timing under computer control? Is it continuous or stepped? What variables control the valve timing?

The VVT is an on/off solenoid to allow oil pressure to advance the intake cams 20 degrees. Retarded at idle, advanced when oil pressure rises with rpm and in drive after warmup, VVT solenoid closes off oil pressure at 4500-4700 rpm so cam retards back to 8 degrees over lap by 4,700-5,000 rpms.VVT boost low mid range torque by 5-10% allowing more filling time when runner air velocity is low.

ECU controls EGR, fuel evaporation cannister, AC compressor cutoff, coolant fans on some models, variable speed fuel pump.

The ECU shares signals: speed, rpm, and TPS voltage with TCU......the TCU tells ecu what gear the tranny is in for timing and speed limiter function.

The ECU even monitors battery voltage to adjust injector duration during cranking and operation to detect alternator failure.............13.7 volts at injectors is normal, a lower voltage will require longer injector duration.

They tested oem injectors down to 8 volts and created a correction table and equation.

The one thing lacking is actual fuel pressure measurement....they make assumptions [that each 10% increase in throttle opening represents [a 1.6 decrease in vacuum in inches.....18<2.0] as the engine vacuum is not measured either .....so cruise at 34 psi and WOT at 43.4 psi [13% flow difference] inbetween partial acceleration [half throttle] is estimated by TPS and rpm.EXACT TPS voltage is critical as the 0.4-4.4 volts is divided into 10-10% increments.....11 throttle positions....closed then 10%>90% and WOT~~~100%.Tip in throttle knock [in 4th gear] comes from not decreasing timing fast enough and dirty lean injectors.....the air flow changes faster than ECU can calculate on old OBDI systems.

TCU commands ECU to cut timing before, during, and ramp up after shift.............this is fixed [adjusted only by ATF temperature] as the TCU assumes the tranny is new and responding correctly [not slipping taking too long to shift].

All this worked out on dyno and equations created to come close less what ever safety factor was picked.

The other thing lacking is measuring fuel temperature and air temperature.........the coolant sensor and a signal from AC is used to determine summer vs normal vs winter mode as the flame speed varies as the air/gasoline temperature [going into cylinder] varies from 50F to 150-200F......resulting in a need to decrease timing to avoid knock.

OBD2 fixed all these guesses!

Fantastic breakdown Q45tech! How do you know if the VVT solenoids are working properly?

The Consult has a test showing if ecu applies the cut voltage.To my knowledge the system has never failed [unlike the J30] in an engine where the oil was changed every 90 days.You can hear the solenoid click with a stethoscope.

As to actually working one could monitor the MAF voltage say at 4000 and 5500 rpm and develop a chart but it would be subtle as I doubt the change would be 5%.

I always rely on my 55-90 mph [4000 to 6700 rpm in 2nd]acceleration times to tell me if something is wrong [power drop].

Never though of a test really.

Seem to remember some talk [long ago] that either JWT or Dinan was lowering the VVT shift rpm down to 4250-4300 rpm in their reprogramming. Probably just a jimmick as 300-400 rpm goes by so quickly except in 2nd gear and above where it might feel better for a second as the VE begins to roll downward at 4100 rpm..............dropping 20% from peak by 6,000 rpm.......337 vs 270lb/ft at 6,000 [with JWT].