Why are DI cars dirty?

My Wife's Subaru Outback tailpipe is sparkly clean, also the beast gets over 34MPG average !
My little Ford TP is sooty and gets 25 MPG ave in the summer.
Both cars have (very) high compression, high specific out put D.I. engines

Maybe I'll take some comparative TP photos when I head out for a grocery run at Noon.

... just BC we like to look at pictures :)
Here are some pic I took yesterday,FWIW. Its no fun lying on the driveway with ants crawling on you :)
The Ford looks about three shades lighter than from winter when it was inky black. I used a flash so the carbon buildup is actually a couple shades darker than it appears here.

2021 Subaru Outback 2.5L FB D.I. Tailpipe
subaru_20220731_132645.jpg


Ford Ecosport 2.0L D.I Tailpipe
ford_20220731_132915.jpg
 
And my early 80s VW with SOHC, mechanical CIS injection would get over 40mpg.... what gets that now? A hybrid?
do you realize back then, cars were light because minimal crash protection compared to today.
today family ev/hybrid car coming closer to 2ton..
 
do you realize back then, cars were light because minimal crash protection compared to today.
today family ev/hybrid car coming closer to 2ton..
I see this analogy repeated, but it neglects a fair assumption that technology should also evolve to lessen or remove the gap created by weight differences. Also, plastic.
 
And my early 80s VW with SOHC, mechanical CIS injection would get over 40mpg.... what gets that now? A hybrid?

Smaller, forced induction engines are inherently less efficient when they are making power.

Full size American FWD cars of the 90s would routinely get 30mpg with loafing V6s. Took my grandmothers 1992 Mercury sable with the head gasket blowing 3.8 on several road trips in the early 2000s and got 30+ mpg, GM 3800 equipped Bonniville would do the same.

Older diesels don't carbon up valves because they had open crancase vents and had no EGR. Pretty much just fresh air to the engine.

Comparing today's VW GTI to an 80's GTI: a lot more power, better safety, friendlier emissions, more comfort, and I'm not going to feel like I'm driving in a literal tin can; so really better overall. Sure it may not be as simple, but technological advancements are rarely simpler than what they replace.

I see this analogy repeated, but it neglects a fair assumption that technology should also evolve to lessen or remove the gap created by weight differences. Also, plastic.

We've progressed technology to better form, shape, and place where the materials go. There is better materials if you want to pay for it but I can't imagine the price of a car that's made out of titanium. Lots of plastic used in the interior definitely but every old car I've been in has used an abundant of plastic on the interior; except the fit and finish of today's plastics is a lot better.
 
Comparing today's VW GTI to an 80's GTI: a lot more power, better safety, friendlier emissions, more comfort, and I'm not going to feel like I'm driving in a literal tin can; so really better overall. Sure it may not be as simple, but technological advancements are rarely simpler than what they replace.



We've progressed technology to better form, shape, and place where the materials go. There is better materials if you want to pay for it but I can't imagine the price of a car that's made out of titanium. Lots of plastic used in the interior definitely but every old car I've been in has used an abundant of plastic on the interior; except the fit and finish of today's plastics is a lot better.
My point is that we were getting better gas mileage 40 years ago in econoboxes then we are today. We now have GDI 10 speed gear boxes etc. But my old 5 speed manual VWs were the king of economic transport.
 
My point is that we were getting better gas mileage 40 years ago in econoboxes then we are today. We now have GDI 10 speed gear boxes etc. But my old 5 speed manual VWs were the king of economic transport.
I think part of that is a focus on emissions. Higher mpg is not necessarily lower emissions even if you burn less fuel. The other part is vehicles weigh more. More airbags more electronics, dual cats.
 
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.
CAFE
 
I have an '18 Forester XT (Turbo), and '22 Forester. Both of course GDI. I do the CRC cleaner every 7/8 K miles. I have no doubt that vehicles with GDI have degraded performance in say 50K miles. At 50K miles I will have the '18 Walnut shell blasted. Based on the condition of the '18 I will determine whether to get it done at that mileage (both having had CRC treatments).

I am frankly almost shocked that manufactures have continued to go the GDI route. I can forsee class actions.

I predict the intakes o n my '18 will be very good. We'll see. It will have had 6 cleanings..well under $100. Seems like a no-brainer to me.
 
I think part of that is a focus on emissions. Higher mpg is not necessarily lower emissions even if you burn less fuel. The other part is vehicles weigh more. More airbags more electronics, dual cats.
Yep, for instance in 1975 the standard for fleet NOx emissions was 3.1g per mile. Tier 3 standards will be in full effect for 2025 for an average of 0.03g/mi for both NOx and NMOG emissions combined. There are “bins” within that that allow up to 0.16g/mi, but an automakers entire fleet average must be at 0.03. So it doesn’t really matter if you have a vehicle getting 10 or 15mpg, as long as your emissions are within the limits you’re good according to the EPA.
 
GDI use in passenger vehicles predates PFI by several years. its advantages and disadvantages are well known and clearly automakers know what they’re doing
 
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Audi/VW 3.0-liter V-6 and 5.2-liter V-10
Ford 3.5L EcoBoost and V6 engines
Lexus 2GR-FSE engines
Subaru 2.0-liter I4
Toyota D4-S 3.5-liter V6 and 5.0-liter V-8 engines

My GDI engine doesn't seem to smoke on startup. I'll have to stick my finger up the tailpipe to see how sooty it is there. Maybe more soot under some conditions is offset by all-over less soot and fewer emissions due to increased fuel economy over a comparable PFI engine?
I don't see any obvious smoke from mine but in the winter the snow in my parking spot will turn completely black from soot right under the exhaust.
 
My point is that we were getting better gas mileage 40 years ago in econoboxes then we are today. We now have GDI 10 speed gear boxes etc. But my old 5 speed manual VWs were the king of economic transport.
I would blame it on nitrogen monoxide emission limits and the extra 1/2 ton you are pulling around. Often engineering is unable to calibrate/tune to run lean cruise and simultaneously meet NOx target. Also with the high compression, the engine often will cover up knock with added fuel, My little ford 4 cylinder will regularly drop to 6 to 7 mpg on the DIC readout with a light throttle going up a hill. Crazy stuff
 
The old Bosch CIS Motronic, and later Jetronic simply held the mixture at 14.7:1 unless in warmup or throttle valve hit the WOT switch. Pretty simple system. And sprayed fuel all the time on the back of the intake valves. Crazy how that even worked. Very good atomization.

If we could do lean cruise we would make lots of NOx but that gallon of fuel would move our butts a lot further.
 
And my early 80s VW with SOHC, mechanical CIS injection would get over 40mpg.... what gets that now? A hybrid?
My 2019 Accent with a 1.6 GDI and 6sp auto averages 40mpg+ and it makes 140hp and will pull a 0-100 of 8 secs. It's power to fuel consumption to ratio (so basically overall efficiency) surprised me since I was just after something cheap and cheerful.

I think the fact small, basic economy cars can now produce the same straight line performance as a 2000s V6 sedan, while maintaining the fuel efficiency and handling of the untra lightweight economy cars of the 80s - despite the added weight in safety features and tech - is fantastic, personally!

On thing I have noticed is it produces a nice soot cloud on the first WOT run if it hasn't been driven hard in a while (the girlfriend is the main driver). The first is the worst by far which makes me wonder if it's blowing the carbon off the valves.
No issues in 105,000km though, mostly hwy.
 
The old Bosch CIS Motronic, and later Jetronic simply held the mixture at 14.7:1 unless in warmup or throttle valve hit the WOT switch. Pretty simple system. And sprayed fuel all the time on the back of the intake valves. Crazy how that even worked. Very good atomization.

If we could do lean cruise we would make lots of NOx but that gallon of fuel would move our butts a lot further.

Sounds like burning leaner and adding SCR would be a good option!

I have SCR in my 21' Vauxhall Insignia and 20L of AdBlue will go 10,000miles. Hardly a big deal.
 
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