ULF: Capacitor-based Spray Control System

Hello Ulf,
Today, I connected a capacitor (marked as 104, but actually 100 nF) in parallel with a resistor (measured at 462 ohms using a multimeter) to adjust the injection rate.

I immediately got on the train and noticed that the engine was producing a bit more black smoke (during acceleration), but the maximum speed was slightly higher, as if the engine was running at a more optimal RPM.

The following changes were made:
Chip+10 cent tuning (1150 Ohm) + advanced injection timing.

My question: Could it be that the engine produces more soot due to the timing adjustment?

tim27 wrote:

My question: Could it be that the engine produces more soot due to the

advance in timing?

Hi Tim,

No, normally, with a slight advance in timing, the amount of soot should decrease... I can't explain why you observed more soot.

Hi Ulf,
'Thank you for your reply. However, could it be that by advancing the injection timing, the engine control unit (ECU) mistakenly believes that the end of the injection is occurring earlier, and therefore alters the programmed injection duration?'
'He wants to achieve higher performance and does this by injecting more diesel.'

That's the only way I can explain why there seems to be a bit more soot.

tim27 wrote:

Could it be that by advancing the injection timing, the control unit thinks that the end of the injection is earlier, and therefore alters the programmed injection end? "He wants to achieve higher performance and does this by injecting more diesel." Because only in this way can I explain the slightly more soot.

Hi Tim,

Apparently, you haven't quite grasped the principle of simple sensor value manipulation yet.

The engine control unit doesn't recognize that the fuel is being injected "too early for its mapping." Therefore, it cannot trigger a deliberate reaction, such as increasing the amount of fuel injected.

Sorry, Ulf.

You're right, I must have mixed something up there.

I saw something online ('according to the MFA') that suggests the engine should consume slightly less fuel. I think that might be quite accurate, don't you?

Best regards,

tim27 wrote:

According to the MFA, I saw that the engine should consume slightly less fuel? I think that could be quite accurate, right??

Hi Tim,

The MFA (Multi Function Analyzer) consistently displays insufficient values when used for analyzing boxing or 10c tuning processes.

By starting the irrigation process earlier, the effectiveness can increase slightly, potentially leading to a minimal real reduction in water consumption.

Hi Ulf,

Okay, so if I think about it, advancing the injection timing seems like a good idea for a €0.10 tuning modification because it reduces the risk of the pistons burning out.

Is that correct?

@tim
'Due to the earlier injection timing, the engine experiences higher mechanical stress. Injection timing towards a later point results in higher thermal stress.'

Whether I put more strain on the engine by mechanically advancing the injection timing or by doing more tuning, isn't that essentially the same thing?

Hello Tim,

No, it's not the same thing. For example, there's a difference between a blown head gasket caused by excessive pressure spikes and pistons, exhaust valves, or turbochargers overheating due to excessively late fuel injection.

Why don't you check out the book "Diesel Engine Technology 2002"? It occasionally appears in the advertising banners on these pages (due to a random function).
It also includes many nice diagrams of test engines, where parameters like injection timing and EGR (Exhaust Gas Recirculation) were varied.

Best regards, Rainer.