Why are DI cars dirty?

[DemoFly]

I guess I never answered the thread title's question.

DI engines are dirty because of the fuel they burn. All engines have some reversion where unburnt fuel slips past the intake valves and leaves a carbon deposit in the intake valve chamber.

In port injected engines, the solvency of the gasoline washes away that carbon in real time. Both engines are making the same amount of carbon deposits, one is just cleaning it. Actually, a port injected engine makes a bit more carbon deposits. But, again, you're none the wiser because it washes them away in real time.

 

[Slick3914]

Several GM GDI V6 in my in law family. Buick, Chevy, etc. All get woefully poor fuel economy, but have excellent power for their displacement without a turbo.

My box van (Promaster) with PFI pentastar 3.6 gets better fuel economy and is the least aerodynamic thing on the road.

I disagree, my 2021 Chevy Traverse RS gets excellent fuel economy with the 3.6 DI V6.

 

[JRHAWK9]

Several GM GDI V6 in my in law family. Buick, Chevy, etc. All get woefully poor fuel economy, but have excellent power for their displacement without a turbo.

My other half has a '21 Acadia Denali AWD 3.6L. We recently took it on a 1,200 mile trip. Averaged 26.6mpg for the whole trip. Finished off getting gas at the same station and same pump as we started at.

This included 2+ hours of off-road driving at idle in off-road mode on a bumpy/narrow two track to get to a waterfall on the US/Canadian border (the 23.22mpg tank above). I was very impressed with how efficient that vehicle is for it's size and aerodynamics! On the way home we averaged 30+mpg....actual. The vehicle said we could go 660 miles on that tank, as I filled it up with half a tank left yet.

 

[atikovi]

I disagree, my 2021 Chevy Traverse RS gets excellent fuel economy with the 3.6 DI V6.

Until the timing chains give out at 80,000 miles and all that money you saved on gas can be used to fix it. (Based on the history of those engines and hopefully that issue has been fixed by now.)

 

[Ignatius]

Until the timing chains give out at 80,000 miles and all that money you saved on gas can be used to fix it. (Based on the history of those engines and hopefully that issue has been fixed by now.)

In my experience dealing with countless GM timing chain engines that give out, usually around 150,000 miles, by the time it happens the cost to repair far exceeds the value of the vehicle and even if repaired the engine will just be a reset ticking time bomb.

 

[BMWTurboDzl]

I cannot for the life of me figure out why manufacturers are all flocking to DI. The sooty intake valves, and the smoke on startup baffles me. This is cleaner and more efficient? I see so many GM products emit a black diesel like cloud on cold start-up.

PFI on the same vintage cars doesn't do that. In fact the inside on the tailpipe on my PFI van looks brand new after 40k miles.

More power, better MPG and better total emissions. A little more soot but soot is only a portion of total emissions.

 

[FowVay]

The contribution of black carbon aerosols into the atmosphere will lead to a measurable increase in solar radiation and ultimately be a major contributor to global warming.

It seemed like a good idea while the guys were sitting at the bar but it's something that isn't delivering the promises. Who knows, maybe it was all planned from the beginning in order to give another argument to support the cessation of the internal combustion engine and promote the EV promise. If you can't believe your own eyes then what can you believe?

 

[atikovi]

The contribution of black carbon aerosols into the atmosphere will lead to a measurable increase in solar radiation and ultimately be a major contributor to global warming.

What's that have to do with carbon deposits in the engine? Or are you referring to cans of black spray paint? I'd think black particles released into the atmosphere would block the sun and cause global cooling.

 

[FowVay]

Atikovi, go back and read the first post in this thread. Read it closely because it has some interesting viewpoints and subject matter. It mentions intake valve deposits, black smoke on start-up, and even a comment about black sooty deposits on the tailpipe of a port fuel injected vehicle. So you can see that this thread is not just about dirty intake valves but rather about the unclean operation of the entire GDI process.

My comment was in regard to how dirty and ecologically unsound the entire premise of the GDI platform is.

And that, sir, is what my comment has to do with carbon deposits in an engine. I don't believe any reasonably intelligent person would associate my comment with a black can of spray paint, but who knows?

 

[JRHAWK9]

Until the timing chains give out at 80,000 miles and all that money you saved on gas can be used to fix it. (Based on the history of those engines and hopefully that issue has been fixed by now.)

In my experience dealing with countless GM timing chain engines that give out, usually around 150,000 miles, by the time it happens the cost to repair far exceeds the value of the vehicle and even if repaired the engine will just be a reset ticking time bomb.

Hoping doing 3,000 mile OCI's with a good oil/filter will help with that if they have not fixed it. If they are failing due to soot from GDI, then I'd think it would help.

 

[atikovi]

Atikovi, go back and read the first post in this thread. Read it closely because it has some interesting viewpoints and subject matter. It mentions intake valve deposits, black smoke on start-up, and even a comment about black sooty deposits on the tailpipe of a port fuel injected vehicle.

I haven't gone around my neighborhood waiting for people to cold start their DI cars, so I can't say I've ever seen one make black smoke on start-up. If it did, there would be a mechanical problem and not something typical for that engine.

 

[vavavroom]

Let's not forget that manufacturers have been adding PFI back and many engines use dual-fuel delivery systems that have both GDI and PFI.

 

[PimTac]

GDI is very clean burning and give great fuel economy and power. Many are rated ULEV.

 

[Bladecutter]

You know, there are lots of manufacturers out there that aren't GM, where the GDI designs are actually done well, and you don't have intake valve deposits, start up smoke (never heard that complaint before today, honestly), rising oil-fuel levels, or early death cam chains.

Also, every time a company makes a car that gets great fuel mileage, some one comes along and says "It doesn't go as fast as my 396 Hemi Charger", and then the entire internet says that car that was designed for high fuel efficiency is under-powered, and it doesn't sell.

Why don't you people buy a vehicle from a car company that isn't in a duck measuring contest with Moe (Dodge) and Curly (Ford), where all three of them only care about selling the most pickup trucks with the biggest bragging rights to suburban dads across America.

There are more than three car companies with an average ownership experience of Bad, Worse, and Ghack.

 

[JohnnyG]

Lower Emissions > Greater fuel economy

GDI is all about increasing the blowby of what would normally go out the tailpipe and trying to force as much of it as possible into the crankcase.

HUH?

 

[JRHAWK9]

You know, there are lots of manufacturers out there that aren't GM, where the GDI designs are actually done well, and you don't have intake valve deposits, start up smoke (never heard that complaint before today, honestly), rising oil-fuel levels, or early death cam chains.

Also, every time a company makes a car that gets great fuel mileage, some one comes along and says "It doesn't go as fast as my 396 Hemi Charger", and then the entire internet says that car that was designed for high fuel efficiency is under-powered, and it doesn't sell.

Why don't you people buy a vehicle from a car company that isn't in a duck measuring contest with Moe (Dodge) and Curly (Ford), where all three of them only care about selling the most pickup trucks with the biggest bragging rights to suburban dads across America.

There are more than three car companies with an average ownership experience of Bad, Worse, and Ghack.

Coming from an owner of mostly German and Italian cars.

Valve deposits on GDI only systems are an issue on all brands of vehicles across the board. VW, BWM, Subaru, etc...they all have issues with it. Some are better than others, but I know a VW tech at a dealer who knows it's an issue. BMW used to have a head exchange program for the issue. Toyota and Ford have hybrid systems in a lot of their vehicles which use port injection to solely keep the valves clean.

I'm hoping there's more reasons than the bean counters as to why other manufacturers don't use a hybrid system.

I have a Subaru and valve deposits are also an issue.

 

[Bladecutter]

Coming from an owner of mostly German and Italian cars.

That's because I gave my 2014 Mazda CX-5 to my Daughter in Law in March 2021 with 80k miles on it.
GDI, no issues, no startup smoke, no intake deposits, great gas mileage, drove fantastically.

Before that I owned a 2011 RX-8, and a 2007 Nissan Altima, both also bought from new.

Just because I don't have something in my fleet today doesn't mean I don't have any experience with it at all.
Feel free to give credit to the 1992 Buick Park Avenue Ultra that I owned for being the last time GM will ever get money from me.

Also, I don't have to commute to work anymore, so I can keep a garage stocked full of vehicles that are more fun than a Toyota Camry.

 

[JRHAWK9]

2014 Mazda CX-5 to my Daughter in Law in March 2021 with 80k miles on it.
GDI, no issues, no startup smoke, no intake deposits,

Do have have any photos of the valves at 80K miles? Have you inspected them? This guy has.


Screen capture from the video. Only 17,000 miles on the car.

 

[OVERKILL]

You know, there are lots of manufacturers out there that aren't GM, where the GDI designs are actually done well, and you don't have intake valve deposits, start up smoke (never heard that complaint before today, honestly), rising oil-fuel levels, or early death cam chains.

The honour for that one goes to Honda, their 1.5L is arguably the biggest offender out there.

 

[sk_pete]

I cannot for the life of me figure out why manufacturers are all flocking to DI.

not all.
renault/dacia 0,9 has turbo-pfi. also made for lpg.