Any MPG Fans here??

[Pinger]

Looked very deep into how the combustion in a Diesel behaves. With a DI injection you have the combustion starting at various points in the cylinder (where the injector sprays)- from there the flame travels outward.

I don't dispute what you are saying - other than it's still not a flame front!
Points of ignition occur where the conditions are favourable ie, some fuel has atomised sufficiently, is entrained with air, and is at a suitably high temperature (at or above the auto ignition temp of the fuel). It follows then that if conditions were favourable there, then they will be in the immediate vicinity also and combustion will occur there too.
The process is one of the swirling air paring droplets of fuel from the (relatively) static injection sprays and ignition occurring when the atomisation/entrainment/auto ign temp criteria are met. A traversing flame front requires a combustible (pre-prepared) mixture and that it be below its auto ign temp (or spontaneous ignition would occur). These conditions are not present in diesel combustion.

Many will think this is dancing on a pinhead but the difference in the nature of combustion in SI and CI engines is what causes them to be allocated different thermodynamic processes namely 'constant volume' and 'constant pressure'. Of the two processes, the SI's constant volume process is the most efficient (theoretically) but that the CI engine generally delivers better fuel efficiency is testament to the operational advantages (discussed earlier) it enjoys.

Congrats on the LSR.

 

[Erik the Awful]

In my research I have found AREO does not really make much MPG.

Aero doesn't make mileage, and it doesn't make speed. Instead, the faster you go the more the air pushes back against the vehicle. Aero gains nothing, but rather helps you keep from losing. At higher speeds there is more to lose, thus aero "gains" are speed-dependent.

Below 50 mph aero will do nearly nothing for mileage. From 50 to 80 mph aerodynamics become important, but you're still better off chasing lean-cruise and other strategies.

Ride height matters. That "aero" Ford picture posted earlier is sitting about two inches too high for the skirting to be really effective. A splitter sticking out two inches would do a lot to prevent air bunching up on the nose from going under the truck. At the same time, downforce is bad for mileage. Don't put end plates on the splitter and try and keep the angle neutral.

 

[eXo0us]

I don't dispute what you are saying - other than it's still not a flame front!
Points of ignition occur where the conditions are favourable ie, some fuel has atomised sufficiently, is entrained with air, and is at a suitably high temperature (at or above the auto ignition temp of the fuel). It follows then that if conditions were favourable there, then they will be in the immediate vicinity also and combustion will occur there too.
The process is one of the swirling air paring droplets of fuel from the (relatively) static injection sprays and ignition occurring when the atomisation/entrainment/auto ign temp criteria are met. A traversing flame front requires a combustible (pre-prepared) mixture and that it be below its auto ign temp (or spontaneous ignition would occur). These conditions are not present in diesel combustion.

Many will think this is dancing on a pinhead but the difference in the nature of combustion in SI and CI engines is what causes them to be allocated different thermodynamic processes namely 'constant volume' and 'constant pressure'. Of the two processes, the SI's constant volume process is the most efficient (theoretically) but that the CI engine generally delivers better fuel efficiency is testament to the operational advantages (discussed earlier) it enjoys.

Congrats on the LSR.

Thanks.
English is not my first language - German is, maybe something is lost in translation

We used two stage injectors- experimented with various nozzle sizes and opening pressures. To get the self ignition going inject a little fuel before just before TDC and as soon as we have fire - spray at lot to make power, while the piston moves down. That fire has a certain speed until it found all oxygen in the cylinder. It's not a singular combustion even like in a SI.
Not sure how you call in English - apparently not flame front.

 

[Pinger]

Thanks.
English is not my first language - German is, maybe something is lost in translation

We used two stage injectors- experimented with various nozzle sizes and opening pressures. To get the self ignition going inject a little fuel before just before TDC and as soon as we have fire - spray at lot to make power, while the piston moves down. That fire has a certain speed until it found all oxygen in the cylinder. It's not a singular combustion even like in a SI.
Not sure how you call in English - apparently not flame front.

I can't remember where I read the expression ''burns off the nozzle'' but it describes well diesel combustion. The fuel burning as fast as it can find air - like a blowtorch.

You were obviously in quite deep. I've read a load of 'papers' on diesel combustion and the strategies employed ie pilot injection and multiple injections along with the main power producing one are staggering. Common rail technology was an absolute game-changer. I remember reading about 20 years back that 'Fiat had diesel technology that was going to revolutionise diesels'. They weren't joking. But in the headlong rush to transition to diesel (in Europe at least) there should have been a recognition that high NOx emissions would be their undoing. Instead, that warning was ignored and hastily applied SCR (Adblue!) has been a disaster.

 

[eXo0us]

Common rail technology was an absolute game-changer. I remember reading about 20 years back that 'Fiat had diesel technology that was going to revolutionise diesels'. They weren't joking. But in the headlong rush to transition to diesel (in Europe at least) there should have been a recognition that high NOx emissions would be their undoing. Instead, that warning was ignored and hastily applied SCR (Adblue!) has been a disaster.

While common rail CR is a great technology for Diesel fuel - it hard to trim for alternative fuels.
The high pressure pumps don't like the high viscosity of alternative fuels. The tolerances are to small in the injectors etc... yeah

Further, NOx and particulate actually got worse with early CR, a mechanical injected Euro 2 emission Diesel - those put out nice smoke the tailpipe - but it was all large particulate. It sank down to the ground rather fast and your lungs are pretty adapt in filtering it out. Then with all Euro 3 and 4 stages - they just made the particulate smaller so that the detectors of that time couldn't register them anymore. While decreasing fuel economy... yes more power - but less economic.

The most efficient Diesel cars where in the 90s and early 2000s. 3L/100km (78 MPG) for small cars and 4L (59MPG) for large sedans and station wagons were common. You could drive a VW bus with 6L (40MPG) and Mercedes Sprinter with 7L (34MPG) Then emission standards where tightened and we ended up with very few cars available for sale today which getting below 30MPG... PROGRESS Lets burn perceived cleaner - but need double the amount of fuel. And it did absolute nothing to clean up the air in cities.

96% of Europe’s urban population is exposed to unsafe levels of air pollution - NILU

Despite a noticeable drop in air pollution from road transport in 2020 due to COVID-19 lockdown measures, breaches of European air quality standards remain a common occurrence across the European Union (EU), according to the EEA briefing ‘Europe’s air quality status 2022’. The briefing was done...

www.nilu.com

Why? now we got Direct Injection Gasoline engines, which are not subject to Diesel particle and NOx testing - which are more fuel efficient but produce particulate and NOx.... lol Sorry for the rant. https://www.sae.org/news/2014/10/attacking-gdi-engine-particulate-emission

All what the standards did - was decrease the fuel economy of Diesel and make Gasoline burn dirty... Well intended but bad outcome.

My good old port inject Vortec 5.7L might be one of the cleanest burning engines out there.

 

[Pinger]

While common rail CR is a great technology for Diesel fuel - it hard to trim for alternative fuels.
The high pressure pumps don't like the high viscosity of alternative fuels. The tolerances are to small in the injectors etc... yeah

That doesn't surprise me. CR tech being direct injection is highly dependent on the fuel air interaction. Change the fuel characteristics (eg viscosity and ease of evaporation) and the system is out of kilter.

Further, NOx and particulate actually got worse with early CR, a mechanical injected Euro 2 emission Diesel - those put out nice smoke the tailpipe - but it was all large particulate. It sank down to the ground rather fast and your lungs are pretty adapt in filtering it out. Then with all Euro 3 and 4 stages - they just made the particulate smaller so that the detectors of that time couldn't register them anymore.

Good point re the smaller particles remaining airborne for longer. Also, the smaller the particle, the further into the human body it can travel.

While decreasing fuel economy... yes more power - but less economic.

Reduced CO2 (which improves fuel efficiency) and reduced NOx are mutually exclusive. Gain on one, lose on the other.

The most efficient Diesel cars where in the 90s and early 2000s. 3L/100km (78 MPG) for small cars and 4L (59MPG) for large sedans and station wagons were common. You could drive a VW bus with 6L (40MPG) and Mercedes Sprinter with 7L (34MPG) Then emission standards where tightened and we ended up with very few cars available for sale today which getting below 30MPG... PROGRESS Lets burn perceived cleaner - but need double the amount of fuel. And it did absolute nothing to clean up the air in cities.

We have to be careful here that when we view 90s diesels as fuel efficient we aren't overlooking that they were largely gutless until the advent of CR. For sure though, the latest NOx reduction measures have reduced fuel efficiency.

96% of Europe’s urban population is exposed to unsafe levels of air pollution - NILU

Despite a noticeable drop in air pollution from road transport in 2020 due to COVID-19 lockdown measures, breaches of European air quality standards remain a common occurrence across the European Union (EU), according to the EEA briefing ‘Europe’s air quality status 2022’. The briefing was done...

www.nilu.com

Some of the problems in cities is due to road planning / traffic calming. Slow a diesel down to a crawl when it then acceleartes particulate emissions will be high before the turbo spools and then NOx emissions will be when it does.
Also, re-mapping (reinstating the torque the OEMs had to dial out to pass NOx legislation), EGR, DPF, swirl flap, Adblue deletion are not helping. In the UK enforcement is lax and it is leading to cars being excluded from cities.

Why? now we got Direct Injection Gasoline engines, which are not subject to Diesel particle and NOx testing - which are more fuel efficient but produce particulate and NOx.... lol Sorry for the rant. https://www.sae.org/news/2014/10/attacking-gdi-engine-particulate-emission

All what the standards did - was decrease the fuel economy of Diesel and make Gasoline burn dirty... Well intended but bad outcome.

To be fair, the fuel economy of SI engines has improved with the adoption of GDI. But, along with turbocharging they are heading down the same path as diesels - ie higher NOx and particulate emissions and much greater complexity.

My good old port inject Vortec 5.7L might be one of the cleanest burning engines out there.

I'll see your port injection Vortec 5.7l and raise you a Vortec 5.7l running on LPG (propane)....

 

[eXo0us]

We have to be careful here that when we view 90s diesels as fuel efficient we aren't overlooking that they were largely gutless until the advent of CR. For sure though, the latest NOx reduction measures have reduced fuel efficiency.

You are correct there. Strapping on CR on an engine yielded 30% more power in many cases for the same cubic size.
Yet for most people a 90PS TDI in VW Golf is perfectly adequate to drive around town and the occasional road trip. You don't need 150Ps+

Mostly psychology for that rate race to ever more power. You had higher powered options back then - but people where buying the 3L/100km and 4L cars.
So the market was more interested in fuel economy over power. Not sure what has changed but the lower powered option disappeared.

In the UK enforcement is lax and it is leading to cars being excluded from cities.

It's that inability from Governments to steer the markets/traffic and understand basic engineering that lets me belief that ICE vehicles will be banned from Cities and eventually countries
Sitting in traffic is just something which a combustion engine is bad at. They are good at driving. EVs are amazing in sitting in traffic - it's the idea use case.
I'm driving an BMW EV for daily commute, the range doubles as soon there is a slow down. The car is cheaper in payments then what I paid in fuel alone before.

The good old V8 is for long trips and towing heavy stuff. Still, I'm optimizing for fuel economy it, I'm a engineer and like to tinker

 

[Pinger]

You are correct there. Strapping on CR on an engine yielded 30% more power in many cases for the same cubic size.
Yet for most people a 90PS TDI in VW Golf is perfectly adequate to drive around town and the occasional road trip. You don't need 150Ps+

Mostly psychology for that rate race to ever more power. You had higher powered options back then - but people where buying the 3L/100km and 4L cars.
So the market was more interested in fuel economy over power. Not sure what has changed but the lower powered option disappeared.

I think that here in the UK two separate things happened in parallel.
Many carried on with the size of car they were used to and enjoyed huge improvement in mpg. Others jumped to cars several sizes larger that with diesel power delivered the same mpg as their previous small cars with gasoline engines had. In essence, a free upgrade to a size of car they couldn't have contemplated the running costs of with a gasoline engine. Resulting CO2 reduction - zero.

It's that inability from Governments to steer the markets/traffic and understand basic engineering that lets me belief that ICE vehicles will be banned from Cities and eventually countries

They cannot even interpret the data. Much of the particulates they record are from (very fashionable) wood burning stoves.

Sitting in traffic is just something which a combustion engine is bad at.

Stop/start tech helps there but it does come with another layer of complexity and many just disengage it when they can.

They are good at driving. EVs are amazing in sitting in traffic - it's the idea use case.
I'm driving an BMW EV for daily commute, the range doubles as soon there is a slow down.

Agreed, cities suit re-gen braking to a tee.

The car is cheaper in payments then what I paid in fuel alone before.

The economic argument is falling apart in Europe due to the massive increases in electricity costs after Putin's exploits. Prior, many EV users were vocal about the cost savings. Entry pricing is still steep though and until battery production and recharging is 100% from renewable energy, the CO2 benefits moot.

The good old V8 is for long trips and towing heavy stuff. Still, I'm optimizing for fuel economy it, I'm a engineer and like to tinker

Mine has to do everything!

 

[L31MaxExpress]

I'll see your port injection Vortec 5.7l and raise you a Vortec 5.7l running on LPG (propane)....

I will raise you both, 383 based L31 on E85 using lean cruise. E85 burns cooler than gasoline or propane, further reducing NOx emissions. E85 also has a high oxygen content in the fuel which helps eliminate CO and HC emissions. E85 will run lean while at steady state cruise without the massive spike in NOX or HCs which practically eliminates CO emissions and does so without the need of a carbon buildup sensitive EGR valve and associated passageways and plumbing. Tested my 97 van on an IM240 cycle using a Mustang dyno and a 5 gas and it was cleaner than a late model direct injected Super Low Emission California spec Nissan V6. My vortec head TPI 383 in my old 83 G20 was also very clean running back in the day.

Just because the thing makes double the stock power does not mean it has to belch emissions. This was my TPI van back then using GM OBD1 electronic control and batch fire injection. It had a MSD 6a box on it, so that probably helped ensure a cleaner, full burn as well. By comparison, look at what the carb setup was allowed to run at, the EFI was fractions of the allowed values. I am going to guess that GenIII electronics using full sequential and coil near plug would have further reduced these numbers.

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[L31MaxExpress]

If I were purpose building an engine for fuel economy it would likely be a L99 4.3L Gen II engine. I would stroke it from 3" to 3.875" using a 6" rod. 3.765 x 3.875 bore and stroke for 345 cubic inches. Small bore limits the amount of timing needed and helps prevent detonation at high static compression ratios. Then it would get as much compression as physically possible and a smallish camshaft. Then I would use the aluminum LT1 heads milled down as far as possible. I would run it with a GenIV computer backed to a 6L80E automatic and 3.08 rear gear. The intake manifold would be a dual plane MPFI setup with a 90mm DBW throttle body on top. Small 1-1/2" primary Tri-y headers to optimize low-midrange torque production. For those that know GM well that is very close to the bore/stroke of a Buick 350 and those engines were well known as producing noticeably more torque than the 350 SBC. I did the tuning on a TBI swapped Buick 350 in an old Jeep Wagoneer (factory engine for that Jeep) and it had loads of low-midrange torque. That Buick 350 would spin 37s in 4 hi on dry pavement. That Jeep later had a 4L80E swapped into it and even on 37s the 350 chugged along at 70 mph effortlessly at 1,850 rpm.