27 replies to this topic

[NTSOS]

Do you all have any thoughts on potential air flow robbing problems due to carbon build up on the back side of intake valves with the use of gasoline direct injection sytems?

Direct Injection and Intake Valve Carbon Build Up

I just ordered an F150 with an Eco-Boost engine and I never really thought about it until I read the article.......figures, a web search reveals alot of information on the subject!

Thanks!

John

[cheapracer]

Got a Mate in Sydney (VW and Audi workshop) cleaning one or two Audi's per week with as little as 50,000 kms. He loves the money it's bringing in.

[NTSOS]

Got a Mate in Sydney (VW and Audi workshop) cleaning one or two Audi's per week with as little as 50,000 kms. He loves the money it's bringing in.

Good for him, but somewhat disturbing news for direct injection owners.......did not they think this deal through?

Thanks!

John

[cheapracer]

I suggested to him to fit old style water injection systems (bottle, 0.40 idle jet and vacuum line) as a possible cure and he looked at me and said "and that helps me how...?"

[Lee Nicolle]

One of the few virtues of unleaded fuel has been fairly clean engines. Even on old carby leaded engines they do stay a lot cleaner.
This seems to go against the flow.
I have seen a 40k 2 year old V6 Commodore with similar deposits on the intake valves as the Audi. Though the engine had far more problems than that. It was a true lemon Chinadore that the heads were truly stuffed and being replaced under GM warranty. They were also porous into the exhaust ports!!

[NTSOS]

I suggested to him to fit old style water injection systems (bottle, 0.40 idle jet and vacuum line) as a possible cure and he looked at me and said "and that helps me how...?"

Maybe a periodic SeaFoam spray as well!

[kikiturbo2]

it is even worse in DI engines that use variable valve lift instead of a normal throttle.. When they get clogged intake valves that usually results in engines that won't operate at small throttles, will cut out in slow traffic, etc etc... Cars that are used exclusively in city traffic are especially prone to this..

[gruntguru]

A full synthetic engine oil would definitely help and possible cure the problem completely. In particular, the Royal Purple racing range is highly solvent to carbon.

[cheapracer]

It was a true lemon Chinadore

Yeah nice try Lee but the engines are made in Australia.

[Magoo]

Every 20,000 miles or so, I might pull a can of Top Engine Cleaner or similar solvent in through a vacuum line.

[NTSOS]

it is even worse in DI engines that use variable valve lift instead of a normal throttle.. When they get clogged intake valves that usually results in engines that won't operate at small throttles, will cut out in slow traffic, etc etc... Cars that are used exclusively in city traffic are especially prone to this..

Yes sir, I can see where that would be a major source of endless problems with this type of engine air flow control.

Thanks!

John

[NTSOS]

A full synthetic engine oil would definitely help and possible cure the problem completely. In particular, the Royal Purple racing range is highly solvent to carbon.

I'm not sure what type of oil the Audi and BMW engines were using in the early days of DI, but yes, the latest spec oil might be a solution as it seems to be also PCV related.

Thanks!

John

[NTSOS]

Every 20,000 miles or so, I might pull a can of Top Engine Cleaner or similar solvent in through a vacuum line.

Yes, a good plan.....SeaFoam Spray includes a little tube that inserts into the inlet tract and you remove it after an application!

Thanks!

John

[NTSOS]

Do you all think that using a PCV oil separator on the ECO-Boost would be a good or bad idea. Used one on a GT-500 that kept the intake manifold intercooler core very clean as opposed to an oily buildup without it.

JLT Oil Separator

Thanks!

John

[gruntguru]

I suspect that the small quantity of oil that passes the intake valve stem seals (essential for guide lubrication) will cause the problem regardles of PCV design.
I do wonder how Diesels (also dry intake) cope with this issue. High detergent oil? Cooler intake valve?

[NTSOS]

Here is an interesting take from another forum that supports the use of better quality oil, but claims the problem stems from the increased injector pressure of the DI diluting the crank case oil with gasoline thus affecting the oil flash point temp. Still doesn't address the reason why diesel engines don't seem to suffer this fate.

#22 07-12-2011, 09:31 PM
m6pwr
Registered User
Location: Ramona, CA Join Date: Jan 2008
Posts: 9
Mein auto: '87 M6, '04 330i zhp
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Intake valve/intake tract deposits are a fairly well documented problem in gasoline direct injection (GDI) engines, particularly turbocharged GDI engines.

The problem in a nutshell is fuel dilution which lowers the flash point of the oil (the point at which oil starts to give off vapors) and causes oily vapors to be sucked (via the crankcase ventilation system) into the intake tract where over time carbon deposits build up that interfere with air flow. This was never a problem in the "old" port injection engines because the intake valves were constantly washed by detergent gasoline. In GDI motors the intake valves see nothing but air and oily vapors.

Where does the fuel dilution come from? In the N54 the HPFP delivers fuel through the injectors at between 1400-1700 psi - - even as the piston is on the compression stroke. Compare this with about 75 psi in port injection. With those kinds of pressures, you get a degree of blowby of fuel past the piston rings. As fuel dilution builds, the flash point of the oil lowers and you get more oily vapors. The high heat associated with turbocharging cooks the oil real good as it flows thru the turbo bearings and adds to the tendency of the oil to give off vapors. Its the job of the oil separators in the crankcase ventilation system to return these oily vapors to a liquid state and send it back to the crankcase before it can get sucked into the intake tract. An engine with top notch piston ring sealing and very efficient oil separators can keep fuel dilution in check and minimize deposits. Fortunately, the BMW N54 doesn't seem to be afflicted with deposit control problems as much as other makes - - http://www.autoobser....-adopters.html. Nevertheless, there have been some anecdotal reports of deposit problems.

What to do if you're worried about GDI and deposits? The lubricants industry has attempted to deal with the problem with its latest standards represented in ILSAC GF-5/API-SN. These standards were developed expressly to deal with the problems associated with GDI turbocharging and deposit formation. The API-SN rating is very new (and as far as I know its restricted to viscosities in the xW30 range). I don't know of any SN oil that carries the BMW LL01 approval. FWIW there is a new oil on the market that does carry the BMW LL01 approval and touts its deposit control performance and says it exceeds GF-5. Its the Pennzoil Ultra Euro 5w40 (the Ferrari oil). It is a Group IV PAO base stock which is a true synthetic (resists heat shear and lowering flash point better than petroleum base stock). As some have noted, Group V ester base oils also do a very good job of resisting the effects of heat and fuel dilution. If you're not worried about BMW LL01 approval you can get ester based oils like Motul 300V or Redline in the 5w30 or 5w40 viscosities allowed by BMW in the N54.

Or, if you're not worried at all about GDI etc., you can always just use BMW's High Performance 5w30 synthetic (probably a Group III "highly refined" petroleum base stock that can be represented as a synthetic) at BMW's specified oil change intervals.

I hope all this doesn't sound too preachy or over complicated- - I'm just trying to add to the discussion. I posted something like this on the e90Post in response to a question about oil in the N54 and was told to shut up, stop trying to impress, and stop disturbing the peace and tranquility of the forum. Hope I'm not repeating the sin here.

[bigleagueslider]

Still doesn't address the reason why diesel engines don't seem to suffer this fate.

NTSOS,

A diesel engine does not have an intake airflow throttle, and is usually turbocharged, so there is not a negative pressure differential at the valve stem/valve guide, which would cause oil to migrate into the intake port. One obvious solution for GDI engines would be throttleless intake VVT systems, such as BMW's, Infiniti's or FIAT's.

Another issue may be the higher operating temps at the intake valves with GDI. With port injection, the latent heat of the fuel helps to cool the intake valve head and seat surfaces as it flows by.

slider

[gruntguru]

Can't agree with the "High injection pressure" theory. Higher injection pressures create smaller droplets, higher evaporation and less tendency to wet the cylinder. The location of the spray is another story. Perhaps the proximity of the injection process increases the possibility of wall-wetting.

[NTSOS]

NTSOS,

A diesel engine does not have an intake airflow throttle, and is usually turbocharged, so there is not a negative pressure differential at the valve stem/valve guide, which would cause oil to migrate into the intake port. One obvious solution for GDI engines would be throttleless intake VVT systems, such as BMW's, Infiniti's or FIAT's.

Another issue may be the higher operating temps at the intake valves with GDI. With port injection, the latent heat of the fuel helps to cool the intake valve head and seat surfaces as it flows by.

slider

Makes sense...........there is also a device on a diesel engine that controls crankcase pressure and is vented to the intake manifold and/or compressor inlet and depending on the condition of the engine, could allow oily vapors to impinge on the back sides of the intake valves on it's way into the operating cylinder.....think it's a CDR valve.

Thanks!

John

[NTSOS]

Can't agree with the "High injection pressure" theory. Higher injection pressures create smaller droplets, higher evaporation and less tendency to wet the cylinder. The location of the spray is another story. Perhaps the proximity of the injection process increases the possibility of wall-wetting.

That's ok......not my theory, but what you said does make sense, maybe it is a proximity deal!

Thanks!

John

[Magoo]

Can't agree with the "High injection pressure" theory. Higher injection pressures create smaller droplets, higher evaporation and less tendency to wet the cylinder. The location of the spray is another story. Perhaps the proximity of the injection process increases the possibility of wall-wetting.

That is exactly right. GG nails it. This is what they know now that they didn't know as the game started: injector pattern is absolutely critical. An injector might have eight orifices, each one carefully aimed in a different direction, and they've done a ton of modeling to sort it out. We'll see, but the Ford people are very confident that their GDI in the EcoBoost engines will not suffer the problems of earlier implementations.

[NTSOS]

That is exactly right. GG nails it. This is what they know now that they didn't know as the game started: injector pattern is absolutely critical. An injector might have eight orifices, each one carefully aimed in a different direction, and they've done a ton of modeling to sort it out. We'll see, but the Ford people are very confident that their GDI in the EcoBoost engines will not suffer the problems of earlier implementations.

Great, I was starting to think I made a bad decision!

Thanks!

John

[TDIMeister]

Still doesn't address the reason why diesel engines don't seem to suffer this fate.

They do, and how!


The problem is only partially due to crankcase vapors, the rest is exhaust particulate matter, which -- an inconvenient truth -- DI gasoline engines also generate, from the EGR system, which said engines also have.

Edited by TDIMeister, 28 October 2011 - 02:35.

[NTSOS]

They do, and how!


The problem is only partially due to crankcase vapors, the rest is exhaust particulate matter, which -- an inconvenient truth -- DI gasoline engines also generate, from the EGR system, which said engines also have.

EGR, interesting....back to hand wringing mode!

What plan of attack would you suggest to help lessen or circumvent said problems as the little ECO motor and the affected sub-systems age?

Thanks man!

John

[gruntguru]

Yes John, that's what the ports on your new truck will look like after a couple of weeks of driving.

[TDIMeister]

The above picture is an extreme example and was taken at a time before ultra low sulphur Diesel was available. Such level of restriction was sadly not uncommon but things have reportedly gotten better with ULSD.

Like Cheap, a friend of mine who's a VW technician is also making handsome money cleaning out the carbon deposits from the intakes of customers' VW/Audi T-FSI engines at a rate of several a week. He reported that several spoonfuls of gunk can be simply scooped out. Nice money, but a frustrating job to do, and opening up one of these T-FSIs always makes him shake his head at some design approaches VAG took. Two VAG dealers in my hometown of about 400000 people refer many customers' cars diagnosed with this problem to my friend because 1. Customers don't want to pay the dealer rate of some CAD$600 to do the job and, 2. Dealer techs don't want to do the job because the book rate pays much less that the actual number of hours required to do the job.

[NTSOS]

Yes John, that's what the ports on your new truck will look like after a couple of weeks of driving.

Oh geeze, I wonder what they will look like after a month or two?

A friend suggested using a company that designs and maintains towing solutions and I think I'll have them take care of the engine maintenance!

Note the attention to detail!

















John

[NTSOS]

The above picture is an extreme example and was taken at a time before ultra low sulphur Diesel was available. Such level of restriction was sadly not uncommon but things have reportedly gotten better with ULSD.

Like Cheap, a friend of mine who's a VW technician is also making handsome money cleaning out the carbon deposits from the intakes of customers' VW/Audi T-FSI engines at a rate of several a week. He reported that several spoonfuls of gunk can be simply scooped out. Nice money, but a frustrating job to do, and opening up one of these T-FSIs always makes him shake his head at some design approaches VAG took. Two VAG dealers in my hometown of about 400000 people refer many customers' cars diagnosed with this problem to my friend because 1. Customers don't want to pay the dealer rate of some CAD$600 to do the job and, 2. Dealer techs don't want to do the job because the book rate pays much less that the actual number of hours required to do the job.

Very disturbing for the unsuspecting early consumers of the "new technology"!

John