The problems with GDI

[Ayrton]

I had read that the better part of twenty years ago, before Mercedes went Direct Injection, they tested having a reservoir of Techron in the engine compartment. It would periodically be applied to the backside of valves (perhaps mixed with some fuel? IDK).

It seems they instead engineered engines that do pretty well without that. Their engines seem to get quite a lot of deposits, but not interfere with performance for the length of most ownership.

Customers would have likely balked at the idea of more maintenance (Techron needing fill up each year or whenever), but I found it fascinating.

 

[SimpleSyrup]

Sure, but when are they added? At the gas station? Who adds them? The truck driver?

At Costco, then blend them at the station after delivery. Other companies have the drivers do it at the terminal. There was an old article from the Costco magazine talking about this. Since Costco has this huge footprint, and there's tons of terminals, they didn't want to risk dealing with a bunch of slackjawed clowns screwing up their gas and destroying cars. So the only way Costco could ensure the gas was in spec on delivery was to add the seasonings after delivery, not before.

 

[Revving2Redline]

Which specifically - if you know or can share?

Redline Si-1 or Gumout Multi-system
CRC IVD Turbo cleaner
Lucas Throttle Spray with PEA
Gumout Multi-system or BG EPR or Liquimoly for engine flush. Have used High Performance Lubricants EC30 which is actually a better value as it replaces some oil and its in the crankcase for some time.

Say no to seafoam, mmo or any fuel additive wothout pea. Even in the gallon of Hotshots LX4, I added four ounces of Redline Si-1 to the gallon to give it a detergent

 

[esandes]

GDI engines really, REALLY need a factory catch can...

The GM LGX 3.6 has one and it still has carbon buildup. Even those with catch cans end up with it.

wonder how?

Catch cans only delay the inevitable fouling of the intake valves. There's no perfect separation.

The only way to cope with the fouling of GDI engines and its negative effect on performance and fuel efficiency is to have a turbo. The additional pressure to the intake valves helps to overcome the additional pressure drop caused from the fouling.

I do not plan to walnut blast my intake valves and intake ports every 15k miles because if I did there would be a negligible difference in performance and fuel economy with all of my GDI turbo engines.

I'd be really interested to know more about the catch can separator design. The internals, inlet device, mist eliminate, can diameter and flow rate.

The real solution to clean the GDI crud is a hybrid fuel injection system. Port fuel injection for light load and direct fuel injection for heavy load. Some car makers have this design.

 

[esandes]

The problems are lazy, broke vehicle owners who won't do the necessary maintenance and won't take unpopular steps to reduce the carbon / soot buildup.
Mid/premium fuel, 12k intake spray cleanings, shortened OCIs and Dexos 1 Gen 3 oils are just 4 of numerous, unpopular ways to help keep the engines cleaner.
Do a Google Search on this subject and find more ways. But if you just want to look at your GDI / TGDI outside in the backyard and continue to sit on your hands, then expect conditions to worsen over time.

Not really. The direct injection design doesn't allow for the cleaning effect on the intake valve and port like port fuel injection naturally does.

Those chemical additives for cleaning don't really clean off the baked on carbon too well. I'd rather resort to an Italian tune up followed by engine brake/vacuum coasting.

 

[ChrisD46]

In my Hyundai 2.4L GDI engine I routinely perform all the preventative maintenance that Triple_Seven suggests . I also run a 3500 mile / 6 month OCI (which ever comes first) and the oil that comes out of this vehicle is quite disgusting : Very dark oil loaded with soot and the smell of fuel in the oil will make you gag when changing it . Once while at Advanced Auto (my usual place to recycle my oil) a worker in back noticed how black and smelly my oil was while I emptied into their used oil receptacle saying , “Looks like you were long overdue on your last oil change” ? I replied : “It would appear that way but this OCI was actually just a little over 3000 miles / 4 months on the oil” . No , I don’t care for GDI - at least in this specific Hyundai iteration I have with my ‘17 2.4L GDI engine … I much prefer mass port fuel injection engines as they run cleaner and are easier to service ridding intake valve deposits via cleaners in the gas tank.

 

[2002 Maxima SE]

Who here has serviced their air-oil separator? If so what was its condition? I have a 2014 Mazda3 coming up on 60k miles. I need to change the coolant soon and should at least check this too while I'm down there. I'll add that in the service manual diagram the air/oil separator looks too small to be effective.

View attachment 249138View attachment 249139View attachment 249140

I owned a 2013 Mazda CX-5. There is no maintenance on the oil separator. The fluid that falls out in the separator drains back to the oil pan. Very smart design by Mazda.

 

[MRC01]

I owned a 2013 Mazda CX-5. There is no maintenance on the oil separator. The fluid that falls out in the separator drains back to the oil pan. Very smart design by Mazda.

If so, that is great. Seems that a drain from the separator to the oil pan would require a 1-way valve to prevent crankcase pressure from going the "wrong way" through the PCV system. I'll check it out when I flush the coolant.

 

[2strokeNorthstar]

GDI engines really, REALLY need a factory catch can...

Catch cans are technically not legal for road use in CA.

 

[ChrisD46]

VW even recommends an "Italian" tune up (15 to 20 minutes) at 3000 RPM (have to use a gear or 2 lower than the highest) to burn away deposits.

Just double checking , is it 3000 RPM’s or 4000 RPM’s for your typical Italian tune up on the highway / interstate ? …I’ve heard 4000 RPM’s previously.

 

[Urshurak776]

In my Hyundai 2.4L GDI engine I routinely perform all the preventative maintenance that Triple_Seven suggests . I also run a 3500 mile / 6 month OCI (which ever comes first) and the oil that comes out of this vehicle is quite disgusting : Very dark oil loaded with soot and the smell of fuel in the oil will make you gag when changing it . Once while at Advanced Auto (my usual place to recycle my oil) a worker in back noticed how black and smelly my oil was while I emptied into their used oil receptacle saying , “Looks like you were long overdue on your last oil change” ? I replied : “It would appear that way but this OCI was actually just a little over 3000 miles / 4 months on the oil” . No , I don’t care for GDI - at least in this specific Hyundai iteration I have with my ‘17 2.4L GDI engine … I much prefer mass port fuel injection engines as they run cleaner and are easier to service ridding intake valve deposits via cleaners in the gas tank.

This is interesting to me Chris. My sons 2019 Hyundai with the 2.4L GDI does not leave the oil like this. I am doing 4K OCI in his car (He actually went to 4,500 miles last time) and in no way is the drained oil like that. No discerning fuel smell and the oil really isn't all that bad when I drain it.

No idea what the difference is between your engine and this one. I cut open his oil filter (EcoGard X10479) in the oil filter section. Used Valvoline R&P last two oil changes. His car has slight oil useage. Maybe half a quart in 4500 miles. Hoping the R&P can help. (After one OCI, no difference. On the second OCI now.)

 

[MRC01]

Just double checking , is it 3000 RPM’s or 4000 RPM’s for your typical Italian tune up on the highway / interstate ? …I’ve heard 4000 RPM’s previously.

The classic Italian tuneup is to redline, or just shy of it to avoid triggering the rev limiter. Done properly, after the engine is warmed up, all temps & pressures in the normal range, and smoothly, it should not hurt anything.

 

[MRC01]

Catch cans are technically not legal for road use in CA.

Why? I can't think of any problem they could cause with emissions or anything else.

 

[Faawrenchbndr]

Why? I can't think of any problem they could cause with emissions or anything else.

Because it’s California and it’s a modification to the emissions system that isn’t CARB approved

 

[2strokeNorthstar]

Because it’s California and it’s a modification to the emissions system that isn’t CARB approved

That's a bingo

 

[MRC01]

Because it’s California and it’s a modification to the emissions system that isn’t CARB approved

OK so purely for legal/regulatory reasons, not for any technical/engineering/practical reason.

 

[oilcandave]

...a lot of this oil buildup is from oil gettin sucked down intake guides..remember the guides and stems run dry until the guide seals start to weep oil..until then the guides and stems wear fast..this is very old school knowledge..anyone remember all this talk when lead was takin away many years ago. Lead was just not for the valve seats but also lubed the stems below the seal.

 

[b_b]

my experience has taught me piston rings go way before valve stem guides.

 

[oilcandave]

my experience has taught me piston rings go way before valve stem guides.

Okay..didnt know rings would cause cooked oil on the back of intakes on a GDI motor..

Once just a little oil starts to make its way down the stem past the seal, wear slows to a crawl. When that starts to happen the oil will cook on the backside of the intakes to various degrees.