INTRODUCTIVE ARGUMENTS

What is a ECU and what is its use.

The ECUs are electronic devices able to draw the conditions of exercise of the engine and to modify the functioning of the interested organs; they govern all the vital functions of the engine, from fuel injection in the cylinders to the correct phase of spark in the combustion chamber, to the antisliding braking systems (ABS), to the drive control systems.

Fig. 1, Bosch Motronic ML 5.4 ECU

The advance and injection ECUs mounted on series cars that are treated here, constantly intervene in the optimal regulation of the engine with the variation of the outside conditions both athmospherical and of load on car.

To function correctly a ECU needs some signals that it receives from some devices called sensors, that are mounted in precise points of the engine; they are:

• Temperature sensor and volume of immitted air in the cylinder sensor
• Engine temperature
• Number of rotations
• Knock sensor
• Throttle valve position sensor
• Oxygen quantity sensor in the discharge gas (lambda probe)

The drawing and elaboration of these data is made in real time during the functioning of the engine; the signals that the ECU sends to the control organs are:

• Time of opening of the fuel injector
• Correction of the advance phase
• Regulation of idle

The advantages of this system are:

• Fuel saving
• Increase of power in some conditions
• Bigger torque, therefore more acceleration
• Less pollutant discharge gas
• Better cold advance
• Constant idle in all conditions

Where are installed car ECUs

Normally the ECUs are situated in the following locations:

• In the carpet in the right passenger side as illustrated in Fig. 4
• In the central pillar under the dashboard or under the glove box, see Fig. 5.
• In the engine opening, see Fig. 6.

Fig. 4, ECU housing in the right side

Fig. 5, ECU housing under the dashboard

Fig. 6, ECU housing in the engine zone

What is a EPROM?

A EPROM ( Erasable Programmable Read Only Memory ) is a particular electronic component able to memorize thousands of data; there are different models each with a different memory capacity; the EPROM characteristic is that it can be erased ad re-programmed many times.

Fig. 7, Eprom 27C256

The erasure is made by submitting it to an emission of ultraviolet rays of a specifical lenght for a cartain amount of time, while the programmation is made with a particular device called "EPROM Programmer". A sample of application software for Eprom Programmer is shown in the Fig. 8.

Fig. 8, Eprom Programmer: application software

Where the Eprom is situated in the ECU

In the most diffused ECUs in commerce, every Eprom has its housing as shown in the figures:

Fig. 9, Eprom housing in the Bosch Motronic ML 5.4 ECU

Fig. 10, Eprom housing in DELCO ECU

Fig. 11, Eprom housing in the IAW Marelli ECU

How to read EPROM data

In the ECUs the EPROM contain operation program and parameters regarding the engine functioning in the different opeartion conditions, or the so-called 'mapping'. An example is made in Fig. 12, where you can see how tha quantity of gasoline injected in the cylinders is function of the two different variables, the load and the engine rating.

Fig. 12, Example of mapping

Once slipped from the housing and inserted in a adequate 'EPROM Programmer', the memory content can be read and transferred as a File in a Personal Computer.

Phases of a change

The change operations are extremely simple because you work essentially with graphic parameters; the change sequence is made by 7 phases listed below:

1. Open the ECU,
2. Extract EPROM memory,
3. Read with the Eprom reader/programmer
4. Elaboration of characteristic curves,
5. Reprogram a new memory,
6. Insert it in the ECU,
7. Last, proof the car.

In phase of Proof the same Eprom (not the original; it's better to save it...) can be erased with EPROM eraser and then reused again in point 5.

In these phases obviously the Eprom emulator is not used, that directly linked to the Computer consents to change in real time the characteristical curves avoiding points 4,5,6 and obtaining the result to prove directly the effect of change during the running or on an engine proof bench.

The Program doesn't have in itself a default mapping, it consents to the operator to set the parameters he prefer. The responsability of all the changes on engine is at the operator charge.

No part of the ECU can be damaged by a wrong programmation, the power degrees, or those that pilot the actuators, as injectors, advance coils, ecc.. can be damaged only from the outside, due to short circuits or wrong polarizations, but not to wrong instructions.

The engine can be damaged if the project tolerances, as shown in this example:

if in a turbocompressed car able to deliver normally 100 HP the mapping is changed to make it deliver 200 HP acting on injection, on ignition advance, on overbooster and on rotations limitator, taking it for example from 7,000 to 9,000 rotations and from 0.7 to 2.5 bars without making the necessary mechanical changes to sustain the surplus of delivered power…. well… I think that that engine will not have a long life…

Obviously when the engine data are changed you must know where and how to act… you cannot think to change an engine without knowledge of the facts.

I personally suggest to those who don't have to try on circuit competitions, to make these changes not to get the maximum deliverable power from the propeller and/or a speed increase (not legal), but to correct defects of engine functioning due to a wrong Air-fuel blending, to a wrong ignition advance or if you need an increase of the torque at low ratings, then a pick-up improvement and a better engine elasticity, with reduced consumption.

How to read a mapping

With the program EPROM MAPS ANALYSIS you can visualize the different mappings both for injection and for advance. An example of EPROM content is represented by the following image:

Fig. 13, Hex-Ascii forma mapping

This unintelligible sequence of numbers and letters is converted by the program in a readable graphic as indicated in the figure below:

Fig. 14, Single curve graphic

How to change a mapping

Obviously changing the single values in specifical points of the EPROM mapping you will get different engine performances in that operation condition.

The program EPROM MAPS ANALYSIS consents to avoid the complex and difficult calculation necessary to change the single values, acting directly on the graphic by changing the curves as indicated in the following figures.

First of all you read the Eprom and save the content in a file, you execute te program and by clicking on a key you choose the file to be loaded in memory (Fig. 15).

Fig. 15, Direct selection of data files

At this point by clicking on the key you generate a file identical to the original on which you can make changes; from now onward the same key will not have the same function.

From the information card indicated in Fig. 16, you choose the address of the function of Eprom to be changed by inserting it in the numerical display and pressing the push button AME to confirm the data.

Fig. 16, Information Card Database

If for example you want to visualize a mapping of injection or of advance, once inserted the base starting address, it will be displayed on both the Graphical Displays as curves, as indicated in Figg. 17.

Fig. 17, Curve visualization

Now it is possible to move with advancement keys to choose the curve that you want to change.

Once selected the curve it is possible to vary it by acting on the multiplication factor selector and on the increasing and decreasing keys to increase and decrease the same curve, as indicated in the Fig. 18, or some points on it as indicated in Fig. 19. The quantity of points that you want to display for each curve is given by the base step display

Fig. 18, Increasing of an entire curve

Figura 19, increasing of a single point

All this can be easily compared to the original by overlapping the two curves, as indicated in Fig. 20, using the curve overlapping switch where the same has been before entirely increased and then some single points have been corrected.

Fig. 20, Comparison of a single curve with the original

The comparison can also be extended to other curves as indicated in Fig. 21, so to compare them contemporaneously. This is obtained enabling the overlapping switch

Fig. 21, Comparison of many curves with the original