COKING IN DIRECT INJECTION ENGINES?

The Audi direct Injection engines are having a lot of trouble with "carbon buildup" as well.

The issue is that there is no longer fuel trickling down the intake runners to work as a solvent to keep the carbon washed off the valves.

It seems a lot of gasoline direct injection engines are going to be battling this issue for a bit until a real solution is discovered. An intake system cleaning procedure with each oil change may be the only way to mitigate issues for the moment.

 

I read on a Porsche forum that there that this issue has cropped up in Porsches also. I'm waiting to hear a definitive answer to the problem before I pony up for a car with DFI.

Dave

 

There are a number of threads on this subject over at "Bob is the Oil Guy".

For all the "inefficiency" of port fuel injection, at least the intake valves are washed with fuel--and the detergents in the fuel can clean off the deposits.

 

Understood. Another point of concern is the actual life span of the injectors themselves ---- no data yet as the DFI engines haven't been out in the field long enough. Of course, all the manufacturer's "predictions" say "no problem" ........but, a modern EFI injector is a precision devise, and adapting it to tolerate long-term exposure to the combustion chamber environment sure seems problematic to me --------- I'm with you --- I'll be on the sidelines watching until we know for sure what happens after 50-60K miles get racked up on these engines.

So what's Ferrari's new 30K service looking like in the future ????

1) Timing belts
2) Complete clutch (if it's an F1 trans.)
*) Replace all injectors ???

........the list and the $$$$ just grows and grows.....how exactly is that an "improvement" for the owner ?

 

I have a DI Audi S5, but only 6 months so far. I did a lot of reading before and after taking the plunge.

Aside from oil vapours being circulated back to the intake manifold via the PCV system, there are two other factors which don't get a lot of recognition yet among the masses concerned about carbon build-up. The early reports from those using catch cans is that they are capturing a bit of oil, but are still encountering carbon deposit buildup.

1 - oil. Lubrizol published a technical paper 2 years ago that showed the latest Euro-IV and VW spec 504 low-SAPS oils have a much lower volatility than earlier 502 or mid- or high-SAPS oils, and these low SAPS oils show 40% less intake deposits. It's hard to find a list of which oils are actually low-SAPS EURO-IV compliant, the best indicator is to find the VW 504.00 specification oils. It's definitely a nuisance, though, as VW North America (and Audi) don't even use 504 oils in their service, they still use older spec 502 oils.

2. - even bigger factor/culprit - passive EGR. Instead of the old exhaust gas recirculation systems that piped small amounts of exhaust gases into the intake manifold, many cars with variable valve timing now use passive EGR, where they control the exhaust and intake valve timing to allow reversion (backflow) of some exhaust gas into the intake manifold at the end of the exhaust stroke/beginning of the intake stroke. This is done for emissions reduction reasons, same as with the piped EGR, but the downside is that the reversion passive EGR gases are hotter than the piped-in EGR and is overheating the oil vapours coming in the PCV systems and causing the carbon deposit buildups. The only cure here would be to have one of the aftermarket tuning vendors like APR build a map that eliminates the passive EGR valve timing modes... so far, I haven't heard of any such offerings.

 

Could you please tell me a bit more about the differences between 504 low-SAPS oils and 502's ?

 

A lot of times this "passive" EGR is not controlled electronically but set in base timing of the camshafts. A lot of the Ferraris have this crossover set, which is what you are checking when setting camshaft timing by using valve lift.

 

Here's a Lubrizol web page with a comparison tool:
http://www.lubrizol.com/EuropeanEngineOils/RelativePerformanceToolIntro.html

Here's their paper on lower SAPS engine oils - slide 19 shows the DI gasoline engine oil comparison between Euro III and Euro IV spec oils specifically referring to valve deposit buildup:
http://www.lubrizol.com/EuropeanEngineOils/UEIL2006LowerSAPS.html

 

David- Ferrari's DI cars have no belts (chains), no clutch similar to earlier cars (wet clutch packs), and there is no telling on the injectors.

Taz
Terry Phillips

 

Be careful with low-SAPS oils. North American gasoline still has high amounts of sulfur and these oils' additive packages isn't adequate for extended intervals even in port-injection engines. When direct-injection engines are destroying the leading readily available conventional synthetics in short order, low-SAPS oils don't stand a chance.

The definitive solution is Toyota's dual system that also has injectors in the manifold.

 

Good point; my plan is to use the low-SAPS VW504 oil for shorter duration intervals, around 10K km (6K miles). That should address the additive package depletion and allow me to use the low volatility oil that reduces carbon deposit buildups.

The Lexus solution is good; another good home brew solution is to add water or methanol injection nozzles to the intake manifolds above each port. That is effective in eliminating the carbon buildups, but does require monitoring and refilling another fluid level regularly.

 

Lubro Moly (Liqui Moly) makes a product called "Ventil Sauber" that is designed to clean intake valves and the entire fuel system. You add it to a tank of gas. It is not a new product, been around for years; I wonder if it might help prevent a problem if you used it every few thousand miles (perhaps each oil change).

http://www.liqui-moly.de/liquimoly/produktdb.nsf/id/e_1014.html

 

Ventil Sauber is a good product, but is typically used as a fuel additive...so it never has a chance to do its job on a direct injected engine, because the fuel never sees the intake manifold and valves. This is where the intake cleaning procedure mentioned by JoshECS comes into play...it typically involves introducing a solvent directly into the intake manifold (often through the PVC system) to attack the carbon in the manifold and on the valves. And yes it is typically messy, smoky, and probably harmful to the cats...

 

As others have noted, fuel additives don't usually work on direct injection engines. In some European markets the fuel is of good enough quality that the engines are programmed to go through a periodic lean burn cycle that burns off deposits. Sadly that does not apply to the US. Other locales have even worse fuel.

We ended up lemoning our Audi RS4 because of persistent problems. I understand some people have avoided this fate. Some use catch cans to separate oil vapour from the crankcase that goes goes back into the intake. Stop and start is a prime culprit.

The new Ferraris lend themselves to every day driving more than ever. However, if this includes stop and go driving, they may be more suspect to carbon problems than if they had been reserved for weekend or track blasts.

Until fuel quality improves or manufacturers find a work-around, this will continue to be a problem. VW, Audi, BMW, MINI, Mercedes, Porsche, and Ferrari have all seen some signs of trouble in various markets. In the meantime, the promised increases in fuel efficiency, power, and emissions become moot. A DI engine that has carboned up valves is not going to be more efficient than an old port injected engine. IMHO this is a quick sop to appease emissions, mileage, and horsepower junkies. But at present it doesn't work for long.

 

The problems with those running "Catch cans" is most are running a standard design that only traps a small portion of the compounds that cause the deposits. The average popular "catchcan"only traps from 15% to a tops of 30% of the offending compounds and oil mist. Only a few seem to actually prevent most of this, and as stated, the EGR emulation will always cause some coking from back filling into the intake port. A good premium full synthetic oil is a must as well as Lubrizol and Amsoil have demonstrated. Aside form that, only the few proven to trap 95% plus have a positive affect on preventing this. The RX (Genuine one, not the cheap China made counterfeits McNally sells), the Elite Engineering E2-X, and the E2 new design, and Colorado Speed has a version as well. Unless a properly designed system is installed, the issue will not be prevented.

 

No one has just mentioned cleaning the valves. In the old days we rebuilt carbs, rebuilt distributor advance. Have we not forgotten the dark days of this and 70's smog controls. DI problems are a joke. It is so easy to clean the valves with walnut shells that when I did it on a BMW with DI I liked the result so much I now walnut shell my Ferrari at every 30k service including balancing and cleaning my fuel injectors out of the car. It is like brushing your teeth. You got to brush them. No amount of mouth wash or dentine chewing gum is going to do the job. As a diy guy DI carbon build up is a non-issue. Those who don't diy have to pay someone to do it just like changing your brake pads. No big deal.

 

I diy and still avoid direct injection. I like working on my "fun" cars but don't want to deal with cleaning the valves on a car I drive daily and put 15-20k a year on. Just the failed engineering bothers me, knowing that every mile I put on it performance is degrading. Some are worse than others of course but still, I don't like it.

The only real fix for this is to have both a port and direct injector, Toyota D4S.

 

I'd like to do this to the valves on my V2 Lamborghini but frankly I haven't found a reference that gave me enough confidence to try this out. In point of fact a certain well respected tech on here castigated me when I asked as just postponing the inevitable.

Well I'm all ears now having run across this post so if you wouldn't mind please expounding upon what you've had success with using?

I've heard of pouring a bit of water in while it's running to clean up the carbon.

But I do remember the walnut shell treatment that was being pushed many years ago.

 

Interesting resurrection of an old post! I posted in this thread 5.5 years ago, and just last month had the intake valves cleaned on my 2010 S5 for the first time, at 60K km. I had the dealer perform the walnut shell blasting for $600 CAN, about $450 USD, during a routine service. I don't have the equipment to perform the intake valve cleaning myself.

 

From that price I'm assuming they don't have to take the heads off to do the service?

Could you tell a difference in performance after the service?

 

Who am I the low hanging fruit to go against any professional? All I got are decades of experience racing cars, fixing race cars, and fixing Ferraris, and building race motors. That said I'm totally self trained so do your own research to see if what I say makes sence.

Materials needed
air compressor
shop vac
shop vac stepdown attachment that goes from the big 3" hose to about a 1" hose
walnut shells
sand blaster head
airgun

easiest done during major service. I am a camshaft remover during my majors for many reasons cleaning intake valves being one of them.

remove cam shafts all the valves close
remove intake plenum to access valves
stick stepdown attachment into port attached to shopvac
stick pointed nozzle of sandblaster into port
nozzle should occlude the whole port or modify something that will fit the whole port this prevents shells from going everywhere.
turn on shop vac blast walnut shells at the valves blindly. takes 10 seconds or less
remove sandblaster tip poke in airgun blow in compressed air stirs up any shell remains to be sucked by shop vac.
inspect rinse and repeat if not clean enough

search youtube for walnut shell cleaning BMW heads

This method has been tried and true. All the OEM use this method. Not a big deal. People freak out about getting shells inside the motor that's why the valves are closed. You can bring every cylinder into TDC combustion and close the intake valves but it is faster to just take the cams out IMO. Shells are just wood and they will burn out safely even if some does manage to get in. Considering the whole cat convert reversion on 355's wood shavings in the engine would be welcome by comparison. Bottom line nothing gets into the motor unless you are sloppy and not paying attention.
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What engines are you doing this on? The thread was originally about DI engines, but I'm assuming you are doing this on earlier engines as well. So if that's the case, are you seeing a lot of deposits during an average major of say a 355 to warrant cleaning the valves?




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Just need the intake manifold(s) off to access the intake valves for cleaning.

Yes, I could feel a difference in the power at full throttle, high rpm.