TECHNICAL NOTES ON THE EEC-IV MCU - Auto diagnostics

RPM 800 1200 1600 2000 2400 2800 3200 3600
Advance 0 0 0 1 6 6 6 6
Table 59: Power Enrich Spark (RPM vs. Added Spark Advance)
20 30 40 50 60 70 80 90 100
400 0 0 0 16 16 36 41 50 54
800 0 0 0 16 18 39 47 52 54
1200 0 0 0 29 45 50 52 57 60
1600 0 0 25 46 50 51 54 58 60
2000 0 0 51 49 51 53 57 59 62
2400 0 1 49 49 51 54 56 59 62
2800 0 2 50 52 54 55 57 60 64
3200 0 3 50 53 55 57 59 61 64
Table 60: Volumetric Efficiency (MAP vs. RPM)
Eectch98-Part5.fm
RPM 0 400 800 1200 1600 2000 2400 2800 3200 3600 4000 4400 4800 5200 5600 6000
Add Fuel 10 10 41 40 41 41 39 37 35 35 37 39 41 41 31 16
Table 61: Volumetric Efficiency WOT Enable (RPM vs. Additional fuel factor)
RPM 0 400 800 1200 1600 2000 2400 2800 3200
% TPS 35 27 26 25 24 23 22 21 20
Table 62: %Throttle Position Sensor for Wide Open Throttle (RPM vs. % factor)
These tables are very different from the OEM setup. But, for this engine combination,
it works. The items to note are the lean/retard overrun (high vacuum values
when you lift your foot off the accelerator pedals at speed) areas. Glance at the
spark table to see when the engine wakes up. Note that the VE table values can add
up to over 100%. Also, because the values in the %TPS for full throttle table are
low, and with the existing VE in the first table, the system will change the air
fuel ratio to rich instantly. Might also note the funny timing under 2800 rpm.
Remember the 2800 rpm stall converter. With this combo the engine can light em at
will in 1st, and 2nd. The car runs in the 13’s but you can see how mild the cam and
engine combination is.
Tuning Tools
In order to know if your wonder toy is about to melt down on one end of the air fuel
ratio spectrum or put a smile on an Arab Sheik’s face on the other end of the spectrum,
you need to monitor the fuel injection system and some of it’s sensors.
Here’s a list of tools:
* Digital Volt Meter (DVM) - (10 meg ohm impedance) for monitoring the Throttle
Position Sensor
* Vacuum Gage - For idle and part throttle analysis;
* Tachometer - If you don’t know, you’ve got a lot of learning to do;
* Performance analyzer - To give you an unbiased reference of the car’s performance
changes other than the uncalibrated seat of your pants;
* Scan Tool - To know what values the ecm is using internally;
EEC-IV Technical Notes: Modifications/Upgrades61 last edited: 9/29/98