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What is the Fuel % for positive pressure

Practical Dyno Tuning

Discussion and questions related to the course Practical Dyno Tuning


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Hi,

I have finished the turbo engine tuning videos so as some of the work examples on some of the e- manager platforms,

I have tune some Honda turbo engines using hondata, which makes the fuel map for you 9retty much, you hit create boost table and it will automatically show all the boost columns you decide if you want 1 bar 2 bar to be displayed and so on.

I have a full grasp on how to create the ignition table from scratch using the base N/A table, and I have pick up how to create a fuel map for naturally aspirated engines. From scratch, using the hp tuning steps,

But so far all the videos and work examples do not mention how much fuel we need to add per psi or per colum as we move on to the positive pressure,

On naturally aspirated we normally copy the last fuel colum past it on the next one and add 5% as a starting point, does this technique stills apply for every 20 kpa?

So my question is, What is the Fuel % we need to add per 10-20 kpa as we move into boost?

Let's say we will run 170 kpa or 10 psi how much fuel we add for every 10 - 20 kpa load?

Thanks you in advance

There isn't a fixed rule as to how much fuel you need to add for a given boost as this will depend on the engine and the turbocharger to a large degree. What you're going to find though is that as you start the tuning process and build up to the positive boost areas of the map, you'll be able to extrapolate the trend that you're seeing out into the positive boost areas of the map.

The other reason it's hard to give a specific percentage change is that the numbers in the fuel map will depend on the way the ECU operates. For example if you're tuning an injection-time based fuel table then you'll need to change the fuel numbers to achieve a different AFR table. On the other hand with a more modern VE based fuel model the AFR is accounted for elsewhere and you tend to get to a point where the VE numbers in the table plateau and don't keep climbing indefinitely with boost.

What Andre said.

There is also the question of adiabatic efficiency and heat soak - how much heat the compression of the charge is adding to it and how the charge cooling efficiency changes over time. Both those are going to affect the charge density - how much oxygen there actually is in the charge and so how much fuel is going to be required.

I would expect this these to chage significantly as boost levels increase and time passes, so some sort of temperature correction will be needed and you may even find you are adding quite a bit more fuel just to try and lower charge and exhaust gas temperatures.