Diesel vs Petrol; Which is Better for ECU Tuning?

One of the most common questions we are asked is: Which is better to remap, diesel or petrol?

Let us state right from the beginning that it's not possible to give a perfectly accurate and scientific answer to this question. However, there are points to consider that may clarify the situation a bit and also be useful for you. We will discuss this topic further in the following article.

Is a diesel car better than a petrol car?

In general, if by this question you mean a good driving experience, significant power, and fewer hassles, then answering it becomes much more complicated. But if the question is about which is better for ECU tuning, it becomes somewhat more specific and precise (although this still means the answer is harder to arrive at!).

But let’s give a one-word answer right at the beginning so we don’t confuse you with conditions and uncertainties! After this brief answer, we will delve into more detailed explanations because, otherwise, our colleagues will kill us!

The answer is that, in our opinion, "diesel" cars are better for ECU tuning! But wait! Hold on until you read our explanations and then we can discuss this opinion further.

Let’s start by examining and comparing the maps for diesel and petrol cars.

ECU maps for diesel cars:

It is logical that many of the maps for diesel and petrol cars are identical—not in terms of their numbers and dimensions, but in terms of the nature of the maps. For example, if a car is turbocharged rather than naturally aspirated, we will have "turbo pressure" maps in both petrol and diesel. Naturally, due to the different operational characteristics of diesel and petrol vehicles, the numbers in these maps will differ for each type of vehicle, but the functionality is the same and exists in both. Many of these identical maps are present in both types of engines, such as torque request in take-off conditions maps, maximum torque limiters, and so on.

But which maps are different?
One of the maps specific to diesel vehicles is the “rail pressure” map. Naturally this map does not exist in petrol vehicles. The function of this map in diesel vehicles is to control fuel injection. The equivalent of this map for controlling fuel injection in petrol vehicles consists of other maps that we will discuss later.

ECU Maps for Petrol Cars:

As mentioned above, similar tables such as turbo pressure or air intake exist in both types of vehicles. However, there are also different tables that are specific to only one type of these vehicles (diesel or petrol).

It can almost be said that in general, the equivalent of the rail pressure maps in diesel vehicles is the spark advance and optimal spark advance maps in petrol vehicles. The function of this map is to control the timing of the spark plug operation, which will vary depending on the type of ECU and its control strategy (most often based on engine load and RPM), but the underlying logic is the same.

With that said, why are diesel vehicles better for ECU remapping?

As we stated, this is an experiential opinion and somewhat personal. However, it can generally be said that diesel vehicles experience a greater increase in torque and power after remapping, which can be largely measured on a dynamometer.

But one should also keep in mind that diesel vehicles have more issues than petrol vehicles, as they have components like DPF (Diesel Particulate Filter), EGR (Exhaust Gas Recirculation), and AdBlue that can lead to various problems (especially in performance).

 

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