The following is a collection of my own research and experiences, I'm not sponsored or affiliated to either of the companies mentioned and I've tried to be as factual and unbiased as possible.
Hopefully this post will help you make an informed decision to go ahead and use Engine Carbon Clean, or avoid it.
Why I Decided To Get My Car Carbon Cleaned
I bought my E92 335i, without having done as much research as I should have, and it bit me hard, to the tune of several thousand £...
Not wanting to make that mistake again, I did a lot of lurking on the Audi owners forums prior to purchase. If there was a common fault I wanted to know what it was, how to spot it, how likely it is to happen and most importantly, how much to fix it.
One topic that came up a number of times was carbon build up, a common affliction of direct injection engines. Still sore were the scars from manually cleaning my 335i's intake valves, the whole process was incredibly laborious. The engine had to be stripped, each pair of intake and exhaust valves painstakingly cleaned using various wire brush Dremel attachments and drill bits, taking in the region of 12 hours. Despite the pain, it was a worthwhile undertaking, this was the state my 335i's intake valves were in after just 40k miles.
After reading through a number of posts on carbon cleaning, I stumbled across a thread on the a5oc forums by Cuppa titled I've got into Engine Carbon Cleaning. I'd never heard of the franchise Engine Carbon Clean before so was intrigued to read more. I assumed it was much the same process as TerraClean, however, it turns out that's not the case at all. Whatever the process was, if it could achieve even 50% of the effect of manually cleaning, I was all ears.
What Are The Differences Between TerraClean and Engine Carbon Clean?
The TerraClean system connects to your car's fuel delivery system, running it on a very highly refined, negatively charged fuel. The fuel reacts with the naturally positively charged carbon deposits in your engine to create carbon dioxide, that is then expelled through the exhaust. I was planning to use TerraClean on my direct injection E92 335i, however, when I contacted my local representative they replied with the following statement:
"Whilst the Terraclean service is extremely efficient at cleaning the whole of the induction and exhaust system on most vehicles from the point of injection it cannot clean any part of the induction system prior to the point of injection as the Terraclean product is fed into the fuel system upstream of the fuel injectors. Therefore this does mean that if there is a build-up of deposits in the inlet tract prior to the point of injection this cannot be removed by the normal Terraclean process.
In recognition of this Terraclean are currently developing a system which will clean from the input side of the throttle body. This system would give me the full and complete answer I was hoping to give to your query. Unfortunately I have been informed that this new system remains unavailable to me at the present time."
In other words, the standard TerraClean process would not actually have cleaned the intake valve area at all. This was back in April 2016 so you may wish to contact your local TerraClean rep to see if things have changed.
Engine Carbon Clean's system is quite different in it's approach. Their machine produces hydrogen and oxygen gas from tap water, that is then introduced into the air intake system after the MAF (mass air flow) sensor. The gases aren't forced into the intake, they are drawn naturally by the engine. The introduction of pure hydrogen and oxygen gases allow for complete combustion, reacting with the carbon deposits and drawing them out of the engine, then expelling them through the exhaust. Unlike the standard TerraClean process, Engine Carbon Clean's process can be used on direct injection engines.
How Much Does Engine Carbon Clean Cost?
The standard price of the Engine Carbon Clean service is £99 per car. However, I arranged for me and 4 mates to get all of our cars done at the same time, which brought the cost down to £80 each.
Just for reference, these are a couple of quotes I found for manual carbon cleaning:
- 034 Motorsport - from $1,195
- Kent Automotive - from £350+vat
Clearly, if Engine Carbon Clean works, it's a decent saving.
You'll also need to budget in for using a quarter of a tank of fuel, the car has to be running for 30 mins and, due to the Audi's rev limiter, needs to be taken for a spin half way through, more on this later.
The Engine Carbon Clean Process
On a bitterly cold morning in May we all descended on a local industrial estate. We'd agreed with a company, who don't work Saturday's, that we could use their car park for the carbon clean. I was advised by Serj (our Engine Carbon Clean rep) that my neighbours wouldn't be overly impressed with 5 hours of revving and a constant generator drone if we did it on my drive.
Between us we had quite an eclectic mix of cars to be cleaned;
- Audi S5 Sportback 3.0 V6T
- BMW E46 330d 2.9 I6
- Jaguar XK 4.2 V8
- Mercedes CLS 3.0 V6 320 CDI
- Range Rover Sport 2.7 TDV6
I was first up, as I'd have to go for a drive half way through the clean. A critical part of the cleaning process is revving the engine, ideally revving to red line. However, the Audi has a rev limiter so, when stationary, the car will only rev to 3 or 4k, red line is 7k.
Serj got to work loosening the intake ducting at the connection to the air filter housing. The hydrogen and oxygen feed was then inserted and sealed with duct tape, a bit crude but apparently the most effective method of sealing.
After 15 mins of mixed idling and revving it was time to take the car for a spin. Serj instructed me that I needed to drive the car spiritedly to have the best effect. You don't have to tell me twice to have a bit of fun...
I took the car on a short 15 mile run, averaging 11.3mpg and using quarter of a tank (I'd brimmed it before the clean), think I pretty much nailed the brief there.
Does Engine Carbon Clean Improve The Exhaust Sound?
One of the claims I'd seen on the web, corroborated by Serj too, is that the Engine Carbon Clean process will change / improve your car's exhaust sound. What it certainly won't do is make it sound better than the day it left the factory, what we're talking about is restoring the car's original sound.
Within 5 mins of starting the clean I noticed a difference in my car's sound, the exhaust note deepened, became slightly louder and had more of a rasp. The guys said (without prompt) that when I drove off at the half way mark there was a noticeable difference to the sound of my car.
I tried to capture the change in the video below, my phone's mic doesn't do the exhaust note justice, but you can just about hear the difference (use headphones to hear the bass difference).
Does Engine Carbon Clean Actually Work?
Whilst I haven't got any dyno or borescope evidence to prove it did or didn't work on my car, here are two accounts claiming it does (with evidence).
This a5oc post showing a V8 S5 regaining 21 bhp and 20 lbft originally sealed the deal for me.
I later came across this Facebook post showing more modest, 5 bhp and 19 lbft torque, but clear gains on a Golf Mk4 GT TDI.
In the interest of fairness though, here's a video of an RS4 where little improvement was seen, +13bhp. If you read the comments, the owner confirms the car was later stripped down and manually cleaned, finding a significant build up of carbon.
Final Thoughts
Did I personally notice a difference? Yes, it wasn't a massive difference, but noticeable nonetheless. In fact, all 5 of us noted a difference in our vehicles. The engine wasn't rough running by any means, but it seemed to be slightly smoother post clean.
The owner of the E46 330d was the most impressed of all of us, unsurprising after seeing the amount of soot it chucked out, leaving 2 blackened patches on the grass behind it. It's worth noting it didn't smoke under acceleration after the clean.
Would I recommend Engine Carbon Clean? Yes I would, if it either prolongs or prevents having to do a manual clean it's worth the money for me. Granted, it's never going to be as good as manually cleaning but I don't think anyone really expects it to be.
What do you think, is it a load of pseudo-science? Has anyone tried TerraClean on their S5? Let me know what you think in the comments below.
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