Motoring myths do they still ring true

[figbat]

1. DPF clogs up.
2. Bit of redex and clears up.

By what mechanism does Redex clear a DPF?

DPFs block up in two ways:

(1) filling up with soot from the incomplete combustion of fuel. This is what they are designed to trap. Soot is carboniferous and so can be cleared from a DPF through heat - get the DPF hot and it burns away the soot. DPFs can be heated up passively or actively according to how the engine is running. The ECU monitors the pressure drop across the DPF and when needed will trigger an active regen session. Passive regen happens when using the engine hard, increasing exhaust temperatures.

(2) filling up with ash - a residue of the combustion of engine oil. Engine oil contains metallic elements which, when burnt, become metallic oxides (ash). You can’t clear ash by heating the DPF up because ash doesn’t burn. You can only clear it through mechanical or chemical cleaning. The chemicals needed to dissolve the ash are fairly potent and won’t survive coming through the engine combustion process, certainly not at the levels added to a tank of fuel.

 

[fossyant]

I suspect it doesn't suddenly clear it, but will raise combustion temperatures sooner - diesel engines take an age to warm up - if I commute to work, in winter, it might just be upto temperature after an hour of traffic - that's what kills them.

A severely clogged DFP can't be 'fixed' but I suspect a little preventative intervention (additives or being aware of the need to get diesels up to temperature to clean the DPF) is the best course of action, but folk don't do this - why would they, a vehicle is like white goods, get in drive, done !

 

[Ming the Merciless]

By what mechanism does Redex clear a DPF?

It works, you tell me how redex dpf cleaner does it.

 

[fossyant]

It works, you tell me how redex dpf cleaner does it.

He better ask Google AI !

 

[Drago]

By what mechanism does Redex clear a DPF?

DPFs block up in two ways:

(1) filling up with soot from the incomplete combustion of fuel. This is what they are designed to trap. Soot is carboniferous and so can be cleared from a DPF through heat - get the DPF hot and it burns away the soot. DPFs can be heated up passively or actively according to how the engine is running. The ECU monitors the pressure drop across the DPF and when needed will trigger an active regen session. Passive regen happens when using the engine hard, increasing exhaust temperatures.

(2) filling up with ash - a residue of the combustion of engine oil. Engine oil contains metallic elements which, when burnt, become metallic oxides (ash). You can’t clear ash by heating the DPF up because ash doesn’t burn. You can only clear it through mechanical or chemical cleaning. The chemicals needed to dissolve the ash are fairly potent and won’t survive coming through the engine combustion process, certainly not at the levels added to a tank of fuel.

Thats where Im skeptical of this stuff. Anything downstream of the combustion process is immune to these additives, which have been stripped to their molecular constituents but he heat and pressure.

 

[figbat]

He better ask Google AI !

Every word of my reply was from my own experience and knowledge of engines and chemistry.

I’ve done some research and it looks like under some circumstances the Redex DPF cleaner could catalyse the passive regeneration process and help reduce soot loading. However the very species that do the catalysing will also accumulate as additional ash in the DPF. Swings and roundabouts.

Of course this only applies to the Redex DPF cleaner, not to run-of-the mill “Redex”.

 

[biggs682]

Is it not a petrol, or is it an older DCi ?

Petrol

 

[Drago]

Every word of my reply was from my own experience and knowledge of engines and chemistry.

I’ve done some research and it looks like under some circumstances the Redex DPF cleaner could catalyse the passive regeneration process and help reduce soot loading. However the very species that do the catalysing will also accumulate as additional ash in the DPF. Swings and roundabouts.

Of course this only applies to the Redex DPF cleaner, not to run-of-the mill “Redex”.

Some additives, allegedly, assist with raising the combustion temperatures during the regen process.

 

[Zanelad]

Just remembered another one that was often used by a guy I used to do freelance work for if ever he was traveling with a trailer behind the transit van he would get as close to the back of anything bigger than the van as he could as it saved him fuel .

Many a mile was travelled watching brake lights like a hawk

I've seen quite a few Tesla drivers doing that behind HGVs on motorways. I guess to improve the range. Other EV drivers may do it, but it's easy to identify a Tesla as an EV.

 

[figbat]

Some additives, allegedly, assist with raising the combustion temperatures during the regen process.

From what I read, the Redex DPF cleaner includes certain metallic oxides which survive combustion (plausible) and then catalyse the thermal decomposition of soot in the DPF by lowering the activation temperature of the oxidation reaction.

I can’t see a relatively small amount of additive making a significant impact on combustion temperatures, although ignition improvers and cetane improvers can make combustion more effective.

 

[Andy in Germany]

Some that seem local to us:

Mercedes cars cannot be parked more than 15 metres from the owners' destination, regardless of things like pavements, disabled bays, or cycleways.

Putting winter tyres on your car gives it magical properties allowing the driver to ignore weather conditions.

 

[Animo]

I don't understand any of the last 100 posts but I've only ever put petrol in my car and it seems to still work

 

[Drago]

I don't understand any of the last 100 posts but I've only ever put petrol in my car and it seems to still work

You maniac!

 

[ebikeerwidnes]

Easy.

A quick spray of this...

View attachment 825343

Nothing worked on our - I had just learned to drive so my expertise was minimal

Had a "feature" where when you put you foot on the brake pedal the car would stop MOST of the times

always stopped second time

well - except fo that one time
but 3rd time worked


for a 17 year old lad that was fine

my dad had other views and sold it - to the garage we got it from who also seemed to think it was a feature

but starting it was its main problem - to me at 17 anyway

 

[biggs682]

Another one I remember from an elderly relative was if doing a long journey increase your tyre pressures by 3 psi as it should lessen the rolling resistance of tyres.

Please note I don't think this to be the case