Why are DI cars dirty?

[Fabulous50s]

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.

 

[wpod]

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.

Soot.

 

[Fabulous50s]

Right.

But please read my post. Why the flocking to sooty GDI?

 

[drtyler]

Right.

But please read my post. Why the flocking to sooty GDI?

Increases in corporate fuel economy would be my guess.

 

[DemoFly]

It leaves more deposits on the intake valves, but that doesn't mean it isn't cleaner and more efficient.

 

[AZjeff]

Why the switch is simple: "Engine technology supplier Bosch says that direct injection can return a 15 percent gain in fuel economy while boosting low-end torque as much as 50 percent."

 

[Fabulous50s]

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.

 

[Ignatius]

Increases in corporate fuel economy would be my guess.

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.

 

[blufeb95]

Port injection\carbs\TBI gives greater time for the fuel to atomize in the intake, GDI engines shoot the fuel right in the cylinder which ultimately leaves more micro droplets that don't fully atomize and turn to soot when burned because only the outter part of the droplet will burn then when the oxygen is all used up the remaining droplet is super heated in an anaerobic environment effectively turns into particles of charcoal, it's well known for happening in diesel engines because diesel fuel is so much less volatile than gasoline and atomizes much more poorly resulting in larger size particle emissions.

 

[OneLonelyBurrito]

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.

It has to do with how the fuel is being mixed in the cylinder. With direct injection, the fuel doesn't have as much time to atomize before the combustion process starts. The creates pockets of rich fuel mixture and rich fuel mixer creates soot. GDI engine are especially prone to soot production on cold start because of the lack of atomization.

 

[Fabulous50s]

Doing some reading....

Looks like we will end up woth GDI and DPFs on gasoline vehicles.......

 

[edyvw]

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.

Maybe it is due to the fact that it is GM product?

DI has been in vehicles since 1997-1998, and yet here we are in 2022 and people just found out about it.

 

[MRC01]

As others have said: increased torque, power and efficiency. The drawback is a dry (air only) intake which can gunk up since there's no fuel being sprayed there which keeps it clean.

Some manufacturers mitigate tendency to build up intake deposits with air/oil separators in PCV system, with valves that resist deposit formation, or with dual fuel systems that occasionally inject fuel into the intake to keep it clean in addition to injecting directly into the cylinder.

 

[CKN]

Yes-D.I. vehicles will be pretty much the norm-just like push button ignition. Either get use to it or give your dinosaur a new heart...........

 

[vw7674]

there was a belief they could get lower octane fuel to burn by introducing it to the chamber later & later, avoiding preignition damage as well.
seeing as it leaves valves so dirty, D.I. saves nothing & provides an incremental improvement so small, it's the smart ones like Toyota that knew already & left some valve-cleaning injectors in place to avoid the manual valve clean$$$$ings.
The fuel washing the cylinder walls & oil dilution is the, uh. 'bonus' ?

 

[ecotourist]

DI has been in vehicles since 1997-1998, and yet here we are in 2022 and people just found out about it.

It's older than that. The late '50s /early '60s Mercedes 300sl convertible and gullwing models both had direct fuel injection.

The Germans used DI in their aero engines in WWII but of course that isn't automotive use. That was one of the advantages of the ME 109 over the Spitfire. It worked better upside down. A Spitfire in a loop had to be keep more or less upright or the carbureted engine would quit.

 

[riverblue]

Direct injection engines produce extra noise, vibration, long-term maintenance costs, and, in the absence of gasoline particulate filters, carcinogenic, cardiotoxic, climate-warming black carbon aerosols (aka PM2.5).

 

[Zaedock]

Why the switch is simple: "Engine technology supplier Bosch says that direct injection can return a 15 percent gain in fuel economy while boosting low-end torque as much as 50 percent."

I attained a similar Torque increase after applying a Thrush sticker to my rear window.

 

[Mainia]

....

 

[edyvw]

It's older than that. The late '50s /early '60s Mercedes 300sl convertible and gullwing models both had direct fuel injection.

The Germans used DI in their aero engines in WWII but of course that isn't automotive use. That was one of the advantages of the ME 109 over the Spitfire. It worked better upside down. A Spitfire in a loop had to be keep more or less upright or the carbureted engine would quit.

I know that. Diesel DI was present even longer, but mainstream is since Volvo/Mitsubishi used it in S40/Carisma.