Do you need a Retune?

By Steven Tramoli

Do you need a Retune?

FUNDAMENTALS OF MODERN ECU MAPPING.

You are our most valuable asset and helping you understand what we do is an investment that we believe both tuner and client will benefit from. The job that we do is often abstract and obscure and we don’t think it should be that way.

If you would like some background information on Internal Combustion Engines we suggest you follow the link. There is also some information on Forced Induction available.

ONE OF THE MOST COMMON QUESTIONS WE GET IS “WILL I NEED A RETUNE IF I CHANGE ABC OR XYZ?”.

Sometimes the answer is more obvious than you may think!

In order to answer the question you need to understand 2 things.

A) What does a tune file do?
B) What effect does the particular mod set have on the engine?

And if your are in doubt book in some logging. We have specialist diagnostic tools that allow us to see exactly how the car is behaving. Read the rest of the article to find out more.

SO WHY DON’T WE ANSWER THE FIRST QUESTION? WHAT DOES A TUNE FILE DO?

Let’s rehash the important bits relevant to this article.

You may have heard from a lot of people that in order to make more power you require more Air, Fuel & Spark.

Let’s break this down:

AIR TO FUEL RATIO

The ratio of air and fuel effects, fuel economy, efficiency of combustion and the temperature of combustion. There is an optimal Air to Fuel Ratio for every motor. We find this optimal figure and tune the vehicle accordingly. On most maps this value is typically a requested value. If there are any changes or inconsistencies with the amount of air or the fuel delivery, the vehicle will do its best compensate and ensure that the target value is met. These changes or inconstancies can either occur due to hardware upgrades or from faults in the hardware itself which may require maintenance.

BOOST LEVELS

In order to create combustion, a motor will use a mixture of air and fuel. By increasing the compression pressure of the turbocharger we can introduce more oxygen into the motor which will in turn create greater combustion forces. We will typically tune a vehicle so that we can reduce unnecessary boost and utilise it to create smooth power delivery without surging and through smart tuning we can continue to generate power all the way to the rev limiter without feeling as if the vehicle has “run out of puff”. Reducing the restriction in a system can sometimes increase the level of boost. In most circumstances the air to fuel ratio will remain in its target value and will not require further adjustment. There needs to be significant changes to the system to throw this values so far out that a retune will be required.

TIMING

During the combustion cycle the pistons move up and down inside the combustion chamber. By igniting the air and fuel mixture early its possible to achieve increased power. Usually when a car is optimised for 98 octane its the timing which has been “advanced” to take advantage of the higher quality fuel. Through port tuning we can optimise cars even further so that they can take advantage of higher octane fuels all the way up to 110 octane. Vehicles equipped with a “knock sensor” will automatically turn down or “retard” the ignition timing in order to ensure the safe operation of the vehicle when a fault occurs. This can occur from low quality fuel, fouled or failing plugs and failing coil packs.

SO TELL ME ABOUT SOME SIMPLE MODS AND WHAT THEY DO.

INTAKES

Restriction in the intake system can reduce the volume of air reaching the combustion chamber. By adding an intake most vehicles can see a mild improvement in power and improved response along with a better sound. The greater the boost level the more restrictive the intake becomes therefore without a software tune intakes will typically have a very small effect on performance. Tunes running safer, mild levels of boost more effectively take advantage OEM equipment and higher boost files have a greater need for intake upgrades.

EXHAUSTS

Restriction can be found on the exhaust side of an engine as well. This is particularly apparent on turbocharged vehicles as the exhaust gases are used to create boost on the intake side. The downpipe straight off the turbocharger is the most relevant upgrade for performance. The reduction in restriction allows for a mild increase in boost levels independent of other changes.

UPGRADE FUEL PUMPS

High Pressure Fuel Pumps improve the vehicles ability to maintain fuel pressure under heavy load. In order to take advantage of the benefits of a high pressure fuel pump inreased boost levels are required so that the motor will compensate with more fuel to maintain the air to fuel ratio. These upgrades are suggested as precautionary upgrade for tuned and modified vehicles but become more important on vehicles which run high levels of boost.

TURBOCHARGERS

The stock turbocharger on a vehicle can be upgraded to a larger version to allow for higher boost pressures. The higher boost level means much more air can enter the combustion chamber and can be mixed with greater volumes of fuel to create more power. Changing a turbocharger makes significant changes to the behaviour of the motor and will typically require a change to software file on the vehicle.

WATER METHANOL INJECTION

Water Meth, as its commonly known, its one of the best bang for your buck upgrades you can do to a turbocharged vehicle. By introducing a high octane fuel and water to the combustion chamber it allows for higher boost levels and more aggressively advanced ignition timing. While most vehicles will pick up a fair amount of power and torque from a Water Meth it also opens up opportunities for tuners to modify the file to take further advantage of this mod.

A NOTE ON HARDWARE MAINTENANCE.

There are certain components which will prevent a vehicle from performing to the level that a tune file requests. The components effect the performance of the motor as a whole and cannot be rectified through software. Two examples are below:

DIVERTER VALVES

A faulty diverter valve will prevent the vehicle from achieving its requested boost levels. By limiting the amount of air the vehicle will compensate by reducing the fuel input. This leads to a very “flat” feeling power curve and much slower performance. An error will often been recorded which a scan tool can read but it can often only be detected by comparing the boost level of the vehicle to the originally requested value from the file upgrade. An experienced performance mechanic will often be able to find and rectify this. We are distributors for Turbosmart who manufacture performance upgrades for these parts and upgrades can often be suggested as a preventative measure. Replacement of the part will result in an immediate return of the power loss from the fault.

CAMSHAFT SENSORS

The ECU relies on inputs from large number of sources. The Camshaft Sensor is one of these sources. A faulty Camshaft Sensor can result in dramatic power losses on a vehicle. It can be hard to detect purely from logging alone. Luckily an experienced mechanic will be able to perform a scan on the vehicle and be able to source and install a replacement part. Many vehicles across many manufacturers suffer from Camshaft Sensor faults, some easy to fix and other can be quite time consuming to diagnose and repair. As with Diverter Valves, replacement of the part will result in an immediate return of the power loss from the fault.

DO I NEED A RETUNE?

Now that you have an understanding of the basics of tuning and the effects of some modifications you have some insight into how we come to a conclusion as to whether or not your vehicle requires retuning.

Ask yourself the following questions:

  1. What effect does my modification have on the vehicle?
  2. Does it have an effect on actual changes made in a tune file?

If you are unsure, consult your tuner. We run through the same basic questions to decide whether or not a retune is required. A logging service can also be offered as well if you to see live information on the vehicles behaviour which typically wont be felt on the road. Running a vehicle on a dyno can give you definitive information, however, the operator needs to take the time to check the data stream and know what to look for. Make sure that your operator is not just taking the car for 3 runs and taking it off. This will not give sufficient data in most situations.

Do I need a retune? For simple modifications, typically not. For major modifications you should contact your tuner and ask the question.

We hope that this article helps you cut through a lot of the noise and offers you a clearer understanding of tuning your vehicle both via software and with hardware. This knowledge should also assist you in making decisions on your hardware modification pathway. If you have details questions and would like to have a direct consultation feel free to contact us directly and we will assist.