Is it worth trying a petrol additive?

[monkeh]

I have had good results with Archoil 6200 in a previous petrol car which was failing emissions due to replacing the cats with sports cats. it failed the MOT and I ran this for around 100 miles on the advice of the mot tester (who didnt sell it to me ) and it made it through. I now use 9800-dmax in the wifes diesel once or twice a year, just to help clean out the DPF and injectors. we don't notice any change in MPG but it is quieter

 

[Petrol Pete]

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Sea Foam Motor Treatment | Sea Foam

Sea Foam Motor Treatment works in fuel and oil systems to clean and lubricate critical engine areas. Safe and effective when used in any gasoline or diesel engine.

seafoamworks.com

 

[Deleted member 65149]

I have had good results with Archoil 6200 in a previous petrol car which was failing emissions due to replacing the cats with sports cats. it failed the MOT and I ran this for around 100 miles on the advice of the mot tester (who didnt sell it to me ) and it made it through. I now use 9800-dmax in the wifes diesel once or twice a year, just to help clean out the DPF and injectors. we don't notice any change in MPG but it is quieter

Thanks, I’ll check it out. Of course I don’t have a DPF on my normally aspirated direct injection petrol car, but I think there’s something similar in the exhaust system because these engines produce more NOx than standard petrol engines.

BTW, when the car had its MoT last week the emission results came out as very good. I think the issue is a mix of carbon build up and water hanging around because of all the short journeys.

 

[Deleted member 65149]

Sea Foam Motor Treatment | Sea Foam

Sea Foam Motor Treatment works in fuel and oil systems to clean and lubricate critical engine areas. Safe and effective when used in any gasoline or diesel engine.

seafoamworks.com

Ah, now I understand. That doesn’t look like treatment for anything in the exhaust system, which is where my issues are.

 

[GeeJayW]

Thanks, I’ll check it out. Of course I don’t have a DPF on my normally aspirated direct injection petrol car, but I think there’s something similar in the exhaust system because these engines produce more NOx than standard petrol engines.

BTW, when the car had its MoT last week the emission results came out as very good. I think the issue is a mix of carbon build up and water hanging around because of all the short journeys.

Direct injection petrol (GDI) engines make more particulate than port injected variants, which is why they now have to be fitted with gasoline particulate filters to comply with the regulations.

Not sure that by definition GDI make more NOx? This is more strongly linked with Lambda or Air:Fuel ratio, and as petrol engines mostly run at Lambda=1 so that the 3-way catalyst can function, I’d expect engine-out NOx to be similar to other engines. Happy to be corrected on that though.

In any case tailpipe NOx should be low as a result of having a 3-way catalyst. A 3-way catalyst doesn’t work on a diesel, which is why tailpipe NOx is an issue.

 

[zipdip]

Would it smoke if you have a DPF fitted ?

Don't see why not.

 

[grober]

https://seafoamworks.com/uploads/2021/05/1420-SF-4001CA-SFMT-SDS-CA-ENG-v20210526-sfi.pdf
PETROLEUM DISTILLATES/SOLVENT -----POSSIBLY OXYGENATED AROMATICS e.g. TOLUENE ---AND 20-30% ISOPROPYL ALCOHOL
the name sea foam will give a clue to its carburettor based marine engine origins with its ingredients designed to sequester/ mop up water in fuel/oil systems----since its likely to contain oxygenated species to do this-- and its the oxygen in water that damages the NOx SENSORS I WOULD NOT RECOMMEND YOU USE THIS PRODUCT!!!!!!


UNLESS THE AFTERMARKET PRODUCT DESCRIPTION STATES SPECIFICALLY ITS DESIGNED FOR USE IN VEHICLES WITH NOx REDUCING EXHAUST SYSTEMS ---DO NOT USE ANY AFTERMARKET FUEL TREATMENT

 

[Bellow]

I've had the NOx sensors replaced twice now but the car has only covered 36k miles.

Is there any way of finding out specifically how they failed? Eg, contaminated (and with what), corroded, etc. Once the failure mode is identified perhaps a solution would be obvious. Are they amenable to removal for inspection/diagnosis?

 

[neilrr]

Is it worth trying a petrol additive?​

Well, according to the 168 previous threads on this topic, some say yes, some say no.

HTH.

 

[Deleted member 65149]

Direct injection petrol (GDI) engines make more particulate than port injected variants, which is why they now have to be fitted with gasoline particulate filters to comply with the regulations.

Not sure that by definition GDI make more NOx? This is more strongly linked with Lambda or Air:Fuel ratio, and as petrol engines mostly run at Lambda=1 so that the 3-way catalyst can function, I’d expect engine-out NOx to be similar to other engines. Happy to be corrected on that though.

In any case tailpipe NOx should be low as a result of having a 3-way catalyst. A 3-way catalyst doesn’t work on a diesel, which is why tailpipe NOx is an issue.

https://seafoamworks.com/uploads/2021/05/1420-SF-4001CA-SFMT-SDS-CA-ENG-v20210526-sfi.pdf
PETROLEUM DISTILLATES/SOLVENT -----POSSIBLY OXYGENATED AROMATICS e.g. TOLUENE ---AND 20-30% ISOPROPYL ALCOHOL
the name sea foam will give a clue to its carburettor based marine engine origins with its ingredients designed to sequester/ mop up water in fuel/oil systems----since its likely to contain oxygenated species to do this-- and its the oxygen in water that damages the NOx SENSORS I WOULD NOT RECOMMEND YOU USE THIS PRODUCT!!!!!!


UNLESS THE AFTERMARKET PRODUCT DESCRIPTION STATES SPECIFICALLY ITS DESIGNED FOR USE IN VEHICLES WITH NOx REDUCING EXHAUST SYSTEMS ---DO NOT USE ANY AFTERMARKET FUEL TREATMENT

Thank you guys. It's these two responses that are adding to my hesitancy with using any such product. Nothing on any of the sales literature for the additives that I've seen gives any mention of it being safe to use with a GDI (or CGI as Mercedes calls it) engine. I'll send an email to Cataclean to see if they can give me any reassurance for my particular set up. They SAY that the product is good for "all engines" but I'd like some reassurance before using it.

Mercedes own words on the M276 CGI engine and its exhaust emissions makes me think that there's a lot that could be adversely affected by coming into contact with what's not designed to be there:

The combustion process developed by Mercedes engineers, with several injection pulses in rapid succession per power stroke, also benefits the smooth running characteristics and exhaust emissions of the V6 engine. Measurements have shown that untreated emissions (hydrocarbons) are reduced by more than half during the warm-up phase. Precisely controlled injection and combustion also allows higher temperatures to be achieved in the exhaust manifold, which ensures that the catalytic converters reach their best operating temperature more rapidly. The direct-injection petrol engine reaches an exhaust temperature of more than 700 degrees Celsius just eleven seconds after a cold start. Exhaust gas aftertreatment is by two close-coupled, closed-loop catalytic converters with linear lambda control which comes into operation immediately after cold-starting.

Mercedes-Benz reduces nitrogen oxide emissions in two ways: with an electrically controlled, cooled, twin-pipe exhaust gas recirculation system, which returns up to 40 percent of the exhaust gases to the cylinders depending on the engine’s operating point, and by two underbody Nox storage-type catalytic converters. During lean-burn operation these converters absorb the nitrogen oxides and release them during brief regeneration phases, so that these pollutants react with the other exhaust gas constituents to produce harmless nitrogen. Sensors located upstream and downstream of the catalytic converters monitor their operation.

 

[Deleted member 65149]

Is it worth trying a petrol additive?​

Well, according to the 168 previous threads on this topic, some say yes, some say no.

HTH.

AFAIK those "168 previous threads" related to cleaning fuel injectors and engine components. I'm looking for possible solutions to the after engine bits: catalytic converters, particulate filters and oxygen sensors.

 

[GeeJayW]

Thank you guys. It's these two responses that are adding to my hesitancy with using any such product. Nothing on any of the sales literature for the additives that I've seen gives any mention of it being safe to use with a GDI (or CGI as Mercedes calls it) engine. I'll send an email to Cataclean to see if they can give me any reassurance for my particular set up. They SAY that the product is good for "all engines" but I'd like some reassurance before using it.

Mercedes own words on the M276 CGI engine and its exhaust emissions makes me think that there's a lot that could be adversely affected by coming into contact with what's not designed to be there:

The combustion process developed by Mercedes engineers, with several injection pulses in rapid succession per power stroke, also benefits the smooth running characteristics and exhaust emissions of the V6 engine. Measurements have shown that untreated emissions (hydrocarbons) are reduced by more than half during the warm-up phase. Precisely controlled injection and combustion also allows higher temperatures to be achieved in the exhaust manifold, which ensures that the catalytic converters reach their best operating temperature more rapidly. The direct-injection petrol engine reaches an exhaust temperature of more than 700 degrees Celsius just eleven seconds after a cold start. Exhaust gas aftertreatment is by two close-coupled, closed-loop catalytic converters with linear lambda control which comes into operation immediately after cold-starting.

Mercedes-Benz reduces nitrogen oxide emissions in two ways: with an electrically controlled, cooled, twin-pipe exhaust gas recirculation system, which returns up to 40 percent of the exhaust gases to the cylinders depending on the engine’s operating point, and by two underbody Nox storage-type catalytic converters. During lean-burn operation these converters absorb the nitrogen oxides and release them during brief regeneration phases, so that these pollutants react with the other exhaust gas constituents to produce harmless nitrogen. Sensors located upstream and downstream of the catalytic converters monitor their operation.

Ah OK, under lean-burn operation there is too much oxygen in the exhaust gases to reduce the NOx, hence the need for de-NOx traps. This is the same problem for diesels. The good news is, if the engine can be made to operate lean enough, engine out NOx, HC and CO drop off quite dramatically, and what HC and CO there is, is very easily dealt with by the oxidation catalyst materials in the main cat. The bad news is that running slightly lean (say Lambda 1.05-1.10) results in a higher NOx peak than conventional petrol engines.

As soon as the car undergoes an acceleration or goes up a hill, the Lambda will shift to something more like 0.9-1.0 where a reducing environment (less oxygen) can be created in the exhaust which can than break down the stored NOx.

 

[markjay]

Red line it every week, problem solved.

But red-lining a diesel engine feels wrong on so many levels.....

 

[Bellow]

But red-lining a diesel engine feels wrong on so many levels.....

Diesels are my red line.

Here though is a case of a petrol engine suffering from an issue more associated with diesels. Not entirely surprising given petrol engine development has gone the same high pressure route as diesels.

 

[Deleted member 65149]

But red-lining a diesel engine feels wrong on so many levels.....

I think the red-lining suggestion was for me, and I would never have a Diesel engine!

 

[Deleted member 65149]

Ah OK, under lean-burn operation there is too much oxygen in the exhaust gases to reduce the NOx, hence the need for de-NOx traps. This is the same problem for diesels. The good news is, if the engine can be made to operate lean enough, engine out NOx, HC and CO drop off quite dramatically, and what HC and CO there is, is very easily dealt with by the oxidation catalyst materials in the main cat. The bad news is that running slightly lean (say Lambda 1.05-1.10) results in a higher NOx peak than conventional petrol engines.

As soon as the car undergoes an acceleration or goes up a hill, the Lambda will shift to something more like 0.9-1.0 where a reducing environment (less oxygen) can be created in the exhaust which can than break down the stored NOx.

This is all getting beyond my chemistry pay grade. Does this mean I may be able to fix things by always accelerating hard up hills?

 

[HB]

But red-lining a diesel engine feels wrong on so many levels.....

I’ll take you out in the SQ7 at full chat and you’ll see. Ours runs 550bhp and 1100 nm

 

[GeeJayW]

This is all getting beyond my chemistry pay grade. Does this mean I may be able to fix things by always accelerating hard up hills?

Not really. The de-NOx storage catalysts are temporary 'buffers' that hold enough NOx during lean-burn operation that can then be processed at times in the journey when the engine is under enough load to warrant a move back towards Lambda <=1, in other words when there's less oxygen in the feed gas. This will happen pulling away from the lights or going up hills in the normal way. Lean-burn operation will most likely be limited to steady light-load conditions.

The main problem for the NOx sensors in your case is I think that the majority of your journeys are short urban trips.

I don't know whether the additives you've listed above perform as per the claims made by the manufacturers, I've not used acetone before as a fuel additive. The dose rates they mention are quite high (500ml/15 litres) and it's worth considering that some of whatever goes in the fuel also ends up in the engine oil/sump. So if you do end up trying it out, it might be prudent to change the engine oil afterwards too.

 

[Deleted member 65149]

Just had a reply from Cataclean:

Good afternoon Tim,


Thank you for your enquiry.


Cataclean is completely safe with all combustion engines, including your 2012 Mercedes C350.

If the fault code is caused due to build-up in the catalytic converter then Cataclean could help, Cataclean’s patented technology is for cleaning both pre and post combustion, including the catalytic converter. I do know these vehicles are very efficient even from cold-starts for emissions with the close-coupled, close-looped dual catalytic converters.


If you have any more questions please do not hesitate to contact me directly.

Best regards,


Zach Baigent

Technical Director

Sounds promising. For £13.45 I might give it a try.

 

[GeeJayW]

I’ll take you out in the SQ7 at full chat and you’ll see. Ours runs 550bhp and 1100 nm

Not for long unless you're going up a very steep hill.