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Frequently asked

FAQs - Restoring efficiency and reducing emissions

What does DPF and EGR mean and why are they important?

What is a DPF?

A diesel particulate filter (DPF) is a device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine. It does this by trapping solid particles while letting gaseous components escape. All modern diesel cars are fitted with a DPF. It is important to maintain the DPF in good condition to prevent blockages as a they are very expensive to replace. A new one from a car manufacturer can cost anywhere between £1,000 and £3,500 and more depending on the make and model of the vehicle.

What is an EGR valve?

An EGR (Exhaust Gas Recirculation) system is a method to control harmful Nitrogen Oxides (NOx) emissions, produced as a by-product during the combustion process. The EGR system works by returning a small portion of exhaust gas to the engine’s combustion chambers through the intake manifold, lowering combustion temperatures and therefore reducing the amount of NOx emitted.

The EGR valve is the main component of the EGR system, and a frequent problem is sticking due to a buildup of carbon deposits. In worst cases, the EGR valve and EGR passages can be completely blocked and need replacing.

How do you take payment?

Your local agent will have their own set methods of taking payment which will include cash, credit card (some) and BACS (some). Cheques are not accepted (unless agreed as part of a contract with a company).

What is the effect of the service?

The effect of the service depends how dirty it is to start with (which depends on how it has been driven, the quality of fuel used, how many miles on the clock and age of the car).

Imagine a car wash, i.e. dirty car in = massive benefits, clean car in = no real difference.

Carbon build-up is worse in:

  • diesels
  • high mileage cars
  • cars never/rarely driven hard as they never get hot
  • taxis and buses are worst as they are sat idling lot of the time with lots of start-stop driving.

Carbon build-up can cause the following...

  • smoky exhaust
  • louder rumbly engine and lumpy idle
  • flat spots or car feeling sluggish (reduced throttle response)
  • increased emissions and reduced MPG
  • DPF and EGR valve issues, swirl flaps sticking, throttle body sticking, turbo vanes and waste gates etc. getting sooted up

So cleaning out the carbon combats and reverses the above.  But it’s all about what you’ve already lost and getting it back, not adding or improving like a modification would.  Carrying out the service on a new/clean car will produce little difference. You don’t really notice on a day-to-day basis, but it builds up over time.

What do you need to perform the clean?

In order to perform the clean, we need the engine warmed up (ideally driven) and also enough room to position our vehicle close enough to attach a hose from the unit to the air intake of the engine.  Our generator is electrically powered so a nearby electrical socket is required, although some agents do utilise a portable petrol generator upon request.

What is the process?

Upon arrival we check the engine for any obvious noises or signs that we ought not proceed with the clean, e.g. leaking oil/coolant, noisy turbo (failing mechanically) or noisy cats (failing mechanically), engine management lights, error codes or any other issues and record them on the job sheet.  We perform a general health check of the engine by starting the engine and revving the engine through the rev range a couple of times (revving exercise) and then holding the revs higher than idle for approx. 20 seconds.  This also allows us to gauge the levels of carbon in the engine already by ear and also feel the throttle response for any graininess, hunting at idle or flat spots.

We then ask the owner to fill in and sign a work sheet prior to commencing the job.

We then turn off the engine and connect the pipe to the air intake(s) of the engine.  The hydrogen and oxygen gas is fed into the air intake of the engine through a pipe…

  • After the air filter(s)
  • After the MAF sensor(s) if present
  • The intake is sealed around the pipe using duct tape. This is ideal for creating a temporary seal as it adapts to all vehicles and is not a permanent measure (we would not advocate the use of duct tape for permanent vehicle repairs).

We then repeat the revving exercise to ensure we have a tight seal around the pipe.

We then turn on the unit and let the engine idle for a minimum of 30 minutes.  Every 10 minutes during this time we will repeat the revving exercise until the engineer is satisfied the job is complete.

The engineer will then disconnect the pipe and reseal the air intake.

The process will be the same as the above on all engines unless there is a rev limited at standstill. If the rev limited cannot be bypassed and the rev limiter is sufficiently low enough in the rev range then the system may not be hot enough to clean properly. As such the engineer may at his discretion choose to split the clean into two parts, punctuated with the owner having to take the car out for a very short ‘spirited’ drive in between.

What is it actually doing? (How does it work?)

The hydrogen and oxygen gas enter the car through the air intake.  The Hydrogen and oxygen gas burn with a much higher temperature, but much faster than the fuel.  This heat generated with an excess of oxygen then reacts with the carbon and the resulting gases exit the car via the exhaust system, cleaning the components on the way out also, i.e. the CAT and DPF on diesel cars.

The EGR valve itself will also be cleaned where present (and not blocked off and the motor is still operational) although some of the slurry which gathers in the pipework may remain.

How long does it take?

Minimum of 30 minutes for the procedure, plus connection and disconnection time.

Connnection/disconnection can be simple and only take 2 minutes, or can be complex and take much longer depending upon the layout and complexity of the intake system, e.g. Audi C5 RS6, some BMWs and Mercedes, some Japanese vehicles, motorbikes, etc.

If the engineer is attempting to clean an EGR, unblock a DPF or unstick a turbo or swirl flap issue then he may choose to run the unit for longer.

How often should I get a carbon clean done?

It is up to you on how you want to maintain your car.  You can leave it until it feels sluggish/noisy again or until you develop and issue, or you could add it to your annual service routine to help prevent issues developing and keep it running in good condition.

Isn’t this just for diesels (what type of engines)?

This process will work on petrol, diesel or even LPG engines and ship engines running on bunker fuel.

Does this work on vans too (what type of vehicles)?

This process can be used to clean ANY petrol, diesel or LPG engine no matter what it is in, e.g. car, motorbike, bus, tractor, tank, generator, lawnmower, etc.

My annual service is due – should I do a carbon clean before or after the service?

Normally you would do a carbon clean before the service as it is recommended to change your oil after this is done.  The only situation where we would recommend performing the clean after service is if there are any pre-existing issues with the car which need fixing first, e.g. oil leak, coolant leak, etc.

I’m going to have a remap – should I do a carbon clean before or after the remap?

Do a carbon clean before the remap as you will then get a remap on to a clean car (definitely if you are having a custom map).

How is this any different to me just revving it or driving it hard myself (known as an Italian Tune Up)?

To remove the carbon you need three components – heat and hydrogen/oxygen.  The Italian tune up method helps elevate temperatures, but not enough to be effective, nor does it introduce any additional oxygen or hydrogen.

What chemicals do you use to clean?

No chemicals. We only use Hydrogen gas, Oxygen gas, and the heat from the combustion process.

Are you steam cleaning the engine?

No. The hydrogen does not reconstitute back into water.

Why doesn’t the gas burn up in the cylinder?

Not all the gas is consumed in the combustion chamber. A mixture of 66% hydrogen ignited with 33% oxygen in lab conditions would indeed just produce water with nothing left over – the stoichiometric ratio would have to be perfect for this to occur. Any shift in the ratio of gases would leave either unreacted hydrogen or oxygen.

Hence with a different gas ratio, plus the interaction with the petrol/diesel combustion process means not all the gas is consumed.

How fast do you pump in the gases?

We don’t pump them, we allow the natural vacuum of the intake to draw the right amount of gases required for the engine size.

Does it clean the inlet manifold on direct injection cars?

It cleans the air ports to it but can’t be sure how much carbon is there beforehand. The procedure will have a cleaning effect to some degree, but some residual carbon may be left depending upon the level of build-up.

Typically with a direct injection car, especially a VW/Audi FSI engine, then the engineer may split the process into two cleans, punctuated with a spirited drive in between to remove as much as is possible.

Do you clean the fuel line?

No, but we recommend owners use good quality fuels.

I’ve got a sticky turbo - will this fix my turbo?

We have great success cleaning turbos as long as the issue is down to carbon build-up.  If the issue is mechanical then no clean will fix it and indeed a failed turbo where the only thing holding it together is carbon build up will thus be exposed.

My CAT is rattling – will this fix it?

The system will clean the catalyst convertor (CAT), but be aware that if a CAT is already breaking up inside that cleaning them out may accelerate this process as the carbon build-up may be acting like a glue holding them together.

My DPF is blocked/constantly regenerating, etc. will this fix it?

We have great success cleaning DPFs although this may take additional time depending upon how badly they are blocked.  If the DPF has been left and is so blocked that there is no flow of gas then the process may not be able to unblock them.

I have blanked off my EGR and or removed my DPF/CAT. Will it still work?

The process will still clean wherever the gas can get to, so obviously if the EGR valve is blocked off then it won’t be able to clean it.

Is this the same as chemical-based engine cleaning?

Very different service. We use hydrogen to remove carbon build-up via the respiratory system of the engine using its own vacuum to draw the hydrogen through the air intake and out of the exhaust.

Doesn't hydrogen and oxygen just make water in my engine?

No. The hydrogen does not reconstitute back into water.

How much hydrogen does the process use?

Depending on size of vehicle approx. 60-105 litres. The Engine Carbon Clean unit calculates the amount required and produces sufficient hydrogen to be effective.

Are there any risks?

This is a service to remove carbon build-up.  If your vehicle has a pre-existing issue or fault which is being masked by the carbon build up and perhaps the carbon is the only thing still holding a part together, (e.g. a failing catalytic converter) then the removal of the carbon will expose the issue.

Can hydrogen damage the engine?

(aside from exposing issues as detailed above) Hydrogen is a non-corrosive gas so it is not detrimental to any component within the engine. It only targets carbon build-up.

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Ready to give Engine Carbon Clean a go?
Please don’t hesitate to book a service with us today – we would love to help out.