C5 X7 additive

[xf1ref]

I just want to share something I saw today when I have checked the Exhaust parameters saved on pdf files from this month.
Seems that fuel additive is injected into the tank even if I didn't refuel nor removed the cap of the tank. I knew that the additive is injected only when refueling.

The parameters from left are from 19th Aug and on the right from 26th Aug..

[GiveMeABreak]

I’m not sure what you’re trying to say there that doesn’t look to be anything abnormal in the PDF read out.

The additive is only injected when you add fuel. When the car is stopped and ignition is switched off, the computer memorised the fuel level in the tank. Then when the car is started again, (whether or not you’ve opened the fuel cap or not, depending on system), it measures the fuel in the tank again and if it’s a higher level it calculates the difference and injects the right amount of additive into the tank.

[xf1ref]

The pdf are fine, I'm just trying to say about the difference of 1ML of additive. I didn't know that additive is injected even if I didn't add fuel.

[GiveMeABreak]

It’s not, that difference is because the amount of additive in the tank is only estimated. It’s not physically measured by anything.

The engine ECU receives the information on the amount of fuel put in the vehicle, via the BSI, from the following components:

• Fuel gauge
• Wheel speed sensors

Depending on the quantity of fuel put in, the engine ECU takes the following actions:

• To determine the quantity of additive to be injected into the fuel tank
• To control the fuel additive pump

So the only way to know for sure how much additive there is in the additive tank is to physically remove the tank and measure it (which is the official procedure), but most people go by the estimate (if they have Diagbox), or when the additive low warning comes on. That is when the system thinks it needs topping up - so will allow you to drive normally, but sooner or later it will go into reduced performance mode until you top it up.

Some will pre-emptively top the tank up at anything from under half a litre or less, but additive is not injected without fuelling,