Engine Tuning Guide

​Chapter -1 :  Where to start

Choice of Vehicle for our guide

I shall focus this paper on Turbo Diesel vehicles as these provide the easiest way to see real time results without the need for a lot of equipment. This is because the diesel engine can run lean without causing failure. A lean petrol engine will burn a piston, valve or turbo. Additionally the turbo allows for a percentage increase in power gains because they are from factory set to run within moderate limits. We can increase this limit safely and mildly but see big improvements.

Do not make the mistake that you can easily make a better map manufactures spend thousands of hours creating these maps, millions of pounds and engineers that have spent 6 years in universities studying all manner of maths to do this. So you’re out before you start then? Well no, the manufacturer makes a map that is a constant state, i.e.: it works in any country with any fuel quality, at any altitude above sea level and any external temperature from snow to desert. This means we can tune the map to suit our environment.

Firstly you need to understand what an ECU is, what it really does. It’s a mistake to think it just makes the engine run by adding fuel and ignition (spark in petrol, compression in diesel). An ECU has to do many jobs that you don’t even consider, however you need to have an understanding of these other features because that will affect how you tune it. On average an ECU in 2015 will have in the region of 10,000 parameters, of these around 33% will be in RAM that cannot be altered and the remaining in FLASH which can be altered so that’s about 7700 things you can change.

The day in the life of an ECU

I’ll give you an example, an ECU will control engine temperature, too do this water is pumped around the engine and passes through a radiator to be cooled. So on start up with cold water and a cold engine the ECU has to deal with all the parts both inside and outside expanding at different rates and the exhaust gasses exiting carrying pollution. For example a piston typically an aluminium alloy expands quicker than the metal of the cylinder wall, typically a cast iron or steel. This can cause a slap noise and allows gasses to escape past the piston rings into the sump and out into the atmosphere if not recirculated. To counter this a cold diesel will inject a small amount of pre injection fuel to warm the cylinder before its main injection and firing compression thus removing noise and decreasing the pollution level in the exhaust as a higher temperature is achieved inside the cylinder. So moving on the engine is now hot, the ECU now needs to cool it down so the pumped water relies on air flowing through the radiator, simple enough as the car drives along the road, come to a stop in traffic and now we need the typically electric fan to cut in when the temperature is too hot. This is done with a simple sensor in the water system, easy all taken care of nothing much to do then... wrong the ECU will take the signal from the water temperature sensor, it will then look at the outside air temperature taken from the mass airflow sensor of if fitted an external sensor, it will also look at the ABS sensor to measure road speed, with a map created for road speed to air speed through the radiator it will decide at what temperature to switch the fan on, and what temp to switch it off. Done? No it will also then look at another map and add in a time delay for switching the fan off this is to prevent a fan from repeatedly going on, off on off which will reduce the relay that provides power to the fans life span. This is calculated from several maps and sensors. Engine speed and therefore water speed through the radiator, airflow through the radiator to calculate efficiency in degree’s per second, outside conditions, the torque map because you need to know how much heat the engine is producing..... now do you see how many things go on inside your ECU? We haven’t even got into the factors to make the engine run. On a recent remap I only changed the air conditioning pump setting so that after 30% throttle the pump dropped out until the throttle was set below 30% this saw an extra 25bhp out of the engine.

How an ECU processes information

Our ECU does this by using a set of pre made set of maps to carry out calculations.

These maps have fixed numbers on the X and Y axis but the ECU will calculate all the steps in between these numbers. For example where it has 35mg of fuel and 40mg of fuel in the map axis the ECU will calculate the values or 36 – 37 – 38 and 39, actually it will calculate the values for 35.001, 35.002 and so on. It will then use the calculation it has made and apply it to another map, this will then give it an adjusted value based on the second map, this process then repeats for the third fourth fifth and so on until it has a final answer.

Then it takes this final answer and applies it to yet another set of maps, this next set of maps  controls the output signal, the signal that the engine actually receives.

The types of sensor an ECU has.

ECU sensors, the 3 catagories.

An ECU has 3 main types of sensor it has sensors that provide Commands in, for example the throttle pedal (TPS) which sends a request to the ECU. Then it has the Monitoring sensors, such as the mass air flow (MAF) which tells it the quantity of X and finally it has the Correction sensors the lambda which tell the ECU that it needs to change it calculations to make a particular problem corrected.

EEPROM vs FLASH EEPROM

I have added in this section to quickly describe the differences between eeprom and flash eeprom.

An eeprom is an acronym, that is it is a shortened word used to describe a sentence. eeprom stands for electrically erasable programmable read-only memory

Flash memory uses an eeprom, but it uses a different type of eeprom

A eeprom needs to be completely erased and then reprogrammed and requires a high voltage to do  this. (this where the heat comes from)

A flash eeprom uses standard computer voltages to write and can have just one part of the memory   change

If I have 1-2-3-4-5-6-7-8-9 in an eeprom and I want to have 1-2 3-4-5-6-7-8-8 I have to erase the entire chip so it will read 0-0-0-0-0-0-0-0-0 Then I send the new set of numbers to it all of them 1-2-3-4-5-6-7-8-8

If I have a flash memory chip and I want to do the same I will not erase any numbers I will only send   Change 9 to 8.

One chip can have both types of data on it i.e. you see one black thing with legs sticking out but  inside it are 2 eeproms one on top of the other (there can be many inside) or.  One programming can write to 2 eeproms at the same time, one can be in the instrument cluster and the other in the radio in the boot of the car!

The main chip on a ECU, the MCU, will use flash memory stored in an eeprom, some MCU's have on board flash memory what this means is inside the MCU is a eeprom others use external eeprom to store the flash memory, they will also have eeproms with fixed memory.

Think of a MCU as a suitcase you can put what you want inside it some manufactures will put 2 shirts 2 pairs of shoes and hat in the case but then put there soap in a separate bag so as not to get their clothes contaminated should the soap leak.

The reason to put eeprom inside an MCU or not? A eeprom generates heat and it can only be used a limited amount of times. If you need 10 eeproms to store all your information you will need a fan to cool down your MCU, if you put your 10 eeproms outside then the MCU will be much cooler and the eeproms will be cooled down by the air around them.

​Chapter -2 : What you need to know and have before you start.

You need to be able to do these following things before you can map a car.

Your mathematical ability

Maths, you need to have a reasonable understanding of maths, and how to use a scientific calculator as you get more involved. By the end of this guide you will know what 14x(1-2.373 to the power of 0.263)/ A squared x (B + 460) means, now don’t worry I will break this down into each part of the equation later on and it is not as complicated as you may think, that said it would help if you knew why there are parts of the equation inside ( )and what to the power of means.

Considering vehicles condition

To design a map you need to understand what condition a car is in, who is driving it and for what   purpose and what its mechanical problems are. A 20,000 mile car will be able to be mapped further than a 80,000 mile car, assuming they have had identical daily use, as the internal condition