Carbon issues with direct injection engines

[NutBucket]

Yes, Toyota does that in some engines. Was discussed previously.

 

[Ramses]

Wouldn't Seafoam work to hit the valve if the right kind were sprayed into a vacuum line? I'm not advising this, BTW, just food for thought.

The interwebs says it does not, wether that is because the deposits are for some reason formed such that it can't remove them or because folks are not administering it correctly/enough of, I can't say. A regular suck into intake will not take off hard thick stuff in one go from any engine, it needs to soak it and sit, frequently more than once, to dissolve the goo bonding the carbon together so that it will release.

 

[KentState]

I kinda assumed that I would need to get the engine in the vette walnut blasted eventually. Honestly though, I'll probably pick up a catch can and stick a scope down there periodically. If it gets bad that's an excuse to pull the heads and have them ported... which is an excuse to get a new cam... which is an excuse to get new valves and springs... which is an excuse... well it all ends up with a 427ci LT1 and lots of boost....

$500 seems very reasonable for blasting the intake valve area. It's not a hard procedure, just time consuming. I doubt that it would be very difficult to DIY if you had a media blaster. Shit I have a 50lb bag of walnut media in the basement (but it's larger stuff for tumbling not for blasting).

I went with a catch can on mine when I got the S/C. You can see it in the lower left hand corner.



Will be curious to see if it does help in the long run. Just as an aside, the LT1 uses RTV seals which are a huge pain. Not as easy as the LSx engines in doing work.

 

[Brian Stirling]

Have to pull off the intake manifold and all the crap connected to it.

Yeah, after posting I checked youtube and it makes sense. It would be nice to have an in situ method that's more economicial.


Brian

 

[soccerballtux]

It wouldn't help any as there isn't any way for seafoam to splash onto the intake valves.

I wonder if any of these issues will be covered under warranty, as there is literally zero preventative maintenance an owner could conceivably do to prevent this..

it's been tough for the BMW owners. this is a significant problem on the 335d, and CPO warranty rejection for the codes the engine is throwing are not uncommon on this.

personally, I'm willing to deal with it for THAT engine/performance in particular

the BMW X5d has the exact same engine but no issues, many theorize due to the lighter engine load from lower coefficient of drag on the highway of the 335d. Solution? drive with a lead foot. keeps the valves clean.

another solution, and someone else touched on-- EGR delete. I believe the EGR was determined to be the main source of trouble here. EGR delete + DPF removal takes highway gas milage from 34 to 38MPGs on the 335d. Not seeing any downsides...

 

[soccerballtux]

I dunno, I've had it clean some pretty gnarly looking stuff given enough time to soak in(diesel EGR passage in an euro intake most recently), the trick is, and the bottle used to say as much I think, that you basically have to choke the motor off with the stuff in order to completely soak into the carbon on the valves, then let it sit, then do it again to blow out the soaked (and in theory dissolved/loosened) crud. Preferably with hard, high RPM driving. I'd rather not put chunks of carbon like that through my motor personally, I've seen carbon pieces hard enough to bend valves. I'd also rather not put chunks of walnut through. Nothing that just blows some solvent across briefly is going to take off serious hard baked carbon, it's got to soak into it one way or another, or use mechanical removal. Wonder if some anti-stick coatings on the back of the valves would help? All of that carbon cleaning stuff works by dissolving the goo bonding the carbon together/to whatever it's attached to. I'd imagine regular treatments before it becomes so dense and packed would be helpful too. I've also used oven cleaner, the more environmentally un-friendly the better, to eat carbon.

lol you don't put 'chunks of walnut through'. The valves are closed, walnut blasted, and on the same device that's blasting, a vacuum that sucks them back up

 

[soccerballtux]

I am left wondering why manufacturers would take a step backwards with a problematic system like DI. It seems like carbon build up is a drawback for this system.

hello? EPA, duh

on the SV1000 motorcycle to get the emissions where they need to be there's an air-rerouting system that takes air from the airbox, bypasses the engine, and puts it into the exhaust, so that the tailpipe 'emissions' are 'leaner'. It just waters them down. It's called the PAIR system and it's completely superfluous.

and that's done because of impossible-to-achieve EPA restrictions

 

[Ramses]

It takes a might small particle to score a bearing. Human hair sized. I've seen people get away with a lot of things, port matching heads on the car and worse, but I don't recommend it.

 

[soccerballtux]

If it's creating deposits from overlap in the combustion cycle then I wouldn't think driving hard would help much if any. In a variocam motor there might be less overlap at high RPM than low or vice versa but I don't see that being significant. Though thoroughly "using" a motor is always a good thing.

higher air speed from greater volume creates more turbulence preventing, and knocking, the carbon off. also, higher heat from the heavier load helps loosen it

 

[Ramses]

The regular application of an "italian tuneup" is never a bad thing.

 

[996GT2]

How is this problem avoided on diesel trucks? Direct injection has been commonplace on heavy trucks for a long time, and those trucks often go a million miles between major engine overhauls. Not to mention they routinely go 30,000 miles between oil changes.

 

[soccerballtux]

How is this problem avoided on diesel trucks? Direct injection has been commonplace on heavy trucks for a long time, and those trucks often go a million miles between major engine overhauls. Not to mention they routinely go 30,000 miles between oil changes.

if I had 20 quarts of oil I could go 30k miles too

I would guess it's the engine load. trucks drive pretty damn hard

 

[Ramses]

Diesels have been direct injection for decades. It's not an issue till EGR happens. The cam profiles are radically different between gas and diesel. Bunch of difference in compression, mixture and byproducts too.

 

[Jimzz]

I want to say that some DI engines *do* now spray fuel on the valves, as an "extra" injector of sorts? The ECM somehow figures out when it's appropriate, and maybe cuts the other one off at the time.

Theoretically the N55 engine has less trouble than the N54 as well, but time will tell. Not sure what BMW changed in this regard (if anything).

Wouldn't Seafoam work to hit the valve if the right kind were sprayed into a vacuum line? I'm not advising this, BTW, just food for thought.

Spraying in cleaner into the vacuum lines and throttle body can help keep the valves clean. I would not use seafoam as its primary ingredient is a pale oil, hence the white smoke when people use it.

And driving hard "Italian tune up" does almost nothing for the DI issue. The carbon on the valves is not some super soft thing that can get blown off at higher RPMs, its needs a cleaner/gas to hit it.
CRC has a new DI cleaner. It uses Liquefied Petroleum Gas, diesel fuel and some solvent. I have not used it yet but would try it.
http://crcindustries.com/auto/?s=05319

 

[NetWareHead]

I want to say that some DI engines *do* now spray fuel on the valves, as an "extra" injector of sorts? The ECM somehow figures out when it's appropriate, and maybe cuts the other one off at the time

Follow my train of thought for a second please. The purpose of DI is to avoid the injection of fuel during the intake stroke. The absence of fuel during the compression stroke means there is no chance for detonation at higher compression ratios or during valve timings that are higher performance.

Furthermore, if a small amount of fuel is injected during intake stroke for the purpose of washing the back of the intake valves, I would imagine that this small amount of fuel is not stoichiometically optimal and would result in a lean condition during the compression stroke (at least until the rest of the fuel enters the cylinder during the injection event). How would engine knocking be controlled in such a situation? Or am I not understanding something here...

 

[Mark R]

Follow my train of thought for a second please. The purpose of DI is to avoid the injection of fuel during the intake stroke. The absence of fuel during the compression stroke means there is no chance for detonation at higher compression ratios or during valve timings that are higher performance.

Under most conditions, DI injects during the intake stroke, this ensures full mixing of fuel and air - so called homogeneous charge. Typically, this will be slightly lean under moderate load, and very rich under high load to minimize detonation.

The advantage of DI is that under certain conditions (e.g. cold starting, very light loads, idle) it is possible to inject during compression, so that you get a very rich mixture around the spark plug, even though the overall combustion ratio is ultra-lean. This is called stratified. The rich mixture provides easy ignition and good stable combustion. The excess air allows the catalyst to provide very high efficiency removal of unburned fuel.

 

[LTC8K6]

I believe there are indeed a few port and direct gasoline engines out there.

http://blog.caranddriver.com/audi-g...urbo-four-and-the-sq5’s-twin-turbo-diesel-v6/

Like some Toyota engines, this Audi powerplant family uses both direct and port injection. Direct injection is used to stabilize the idle and in full-load situations, while the port injectors are put to work under partial loads, where Audi engineers say port injection is better at mixing the fuel and air, with less soot produced and reduced CO2 emissions compared to direct injection. Unlike the Toyota setup, this engine operates either as a port-injected engine or a direct-injected one, and never uses both injectors simultaneously. The third-generation EA888 is said to be about 11 pounds lighter than the second gen, despite the wealth of new features.

Toyota's D4-S system is port and direct injection.

http://www.ft86club.com/forums/attachment.php?attachmentid=3868&stc=1&d=1326052791

A new V-6 3.5-liter gasoline engine (2GR-FSE) uses a
newly developed stoichiometric direct injection system
with two fuel injectors in each cylinder (D-4S: Direct
injection 4-stroke gasoline engine system Superior
version). One is a direct injection injector generating a
dual-fan-shaped spray with wide dispersion, while the
other is a port injector. With this system, the engine
achieves a power level among the highest for production
engines of this displacement and a fuel economy rating
of 24mpg on the EPA cycle. Emissions are among the
lowest level for this class of sedans, meeting Ultra Low
Emission Vehicle standards (ULEV-II).

 

[NetWareHead]

Under most conditions, DI injects during the intake stroke, this ensures full mixing of fuel and air - so called homogeneous charge. Typically, this will be slightly lean under moderate load, and very rich under high load to minimize detonation.

Ok so this is where my misunderstanding lies. I was thinking that gasoline DI injects like a diesel engine DI does

 

[Ramses]

Interesting that port injection is superior under some circumstances. Wouldn't be the first time that new tech was introduced that wasn't across the board superior to the old stuff though. It's usually to meet smog standards when it happens. Like the euro guys grudgingly getting rid of CIS years ago.

 

[Ramses]

Ok so this is where my misunderstanding lies. I was thinking that gasoline DI injects like a diesel engine DI does

Diesels are a different animal in a lot of ways, there is a lot of stuff that is perfect on one but rubbish for the other.

 

[EightySix Four]

I went with a catch can on mine when I got the S/C. You can see it in the lower left hand corner.



Will be curious to see if it does help in the long run. Just as an aside, the LT1 uses RTV seals which are a huge pain. Not as easy as the LSx engines in doing work.

Inject meth. Problem solved.

 

[Ramses]

Could be worse..

 

[The Boston Dangler]

Could be worse..

no way that's real. that huge pile of coal? come on

 

[The Boston Dangler]

wouldn't an atkinson cycle circulate a lean mixture back over the intake valves to clean them?

https://www.youtube.com/watch?v=z45fM2N-4C4&list=PL30C950600B683799&index=18

 

[Ramses]

no way that's real. that huge pile of coal? come on

Yep, it happens. My euro 1Y code NA intake I finally rummaged up was not much better. Was no fun to clean. While the diesel intake clogging goo is different than gasser valve carbon deposits, it could still be worse.

https://www.google.com/search?q=tdi...a=X&ei=RWBeVci0M8u5oQSPw4P4BQ&ved=0CAcQ_AUoAg