3 ms·

> Some readers are bound to be a bit disappointed that the VNL doesn't improve fuel efficiency by quite as much as that ambitious research project. That's beca

by uticus 2y ago

> Some readers are bound to be a bit disappointed that the VNL doesn't improve fuel efficiency by quite as much as that ambitious research project. That's because it will take something drastically different than upgrading the truck - either switching to a completely new type of tractor/trailer, or switching to a different mode of transportation entirely. Long-haul transport has been economically incentivized for a good return on fuel cost since forever, unlike the typical four-wheeler configuration most of us drive. The trucks are pretty much maxed out on performance that they're able to do. I should lastly add, maxed out on performance when balanced against maintenance. Like, I could put a very performant F1-type high-tech engine in one, and possibly eke out some performance gains. But the overall schedule and cost will negate any fuel savings, not to mention the added hidden environmental burden of maintaining exotic frail engines.

jrmg 2y ago
It sounds like 7 percent of the 10 percent efficiency gains are from aerodynamics. I expected (probably naively) engine changes to play more of a role.
- SAI_Peregrinus 2y ago
  Diesel engines already have very high compression ratios. Compression ratio directly correlates with the ratio of temperature at combustion to the temperature outside the engine, which is the limiting factor in the Carnot efficiency. A gasoline engine will be able to get up to maybe 12:1 before knock is an issue, high-efficiency diesels can hit 25:1. Gas turbines can hit even higher ratios, but are far more complex & expensive (e.g. the GE GEnx-1B78/P2 turbofan has an overall compression ratio of 58 and thermal efficiency of 58%, but it has a list price somewhere around $20 million and is bigger than the entire truck cab).
- uticus 2y ago
  If you noticed, the article talked about aerodynamics in terms of frontal area and side fairings - on other words, the parts of the tractor interacting with the airstream. The trailer's leading edge is, well, a large, flat, un-aerodynamic rectangle. Lots of potential for aero improvements there. I sometimes see boat-tails etc attached to trailers, but my understanding is that they are usually attached (an unattached at destination) by tractor owner, as trailer owner doesn't pay for fuel costs. Could be wrong on that though.
bArray 2y ago
> I should lastly add, maxed out on performance when balanced against maintenance. Like, I could put a very performant F1-type high-tech engine in one, and possibly eke out some performance gains. But the overall schedule and cost will negate any fuel savings, not to mention the added hidden environmental burden of maintaining exotic frail engines. This would just be a flat rejection to any engine modifications at all. I suspect they would still be just as reliable and no more exotic than any other engine. And if want to go down the route of unmaintainable, I think we should discuss electric trucks. Each part is coded to work only with specific parts, insane costs to repair/maintain, no real standardization to any part, quite dangerous to work on, etc. The environmental burden of those is going to be insane.
- uticus 2y ago
  > This would just be a flat rejection to any engine modifications at all. I suspect they would still be just as reliable and no more exotic than any other engine. Not a flat rejection to any engine modifications, but an acknowledgement that meaningful and maintainable engine modifications have already been implemented. I'll say it again: performance and efficiency have to be balanced against cost, a large part of which is maintenance. There's nothing like simple capitalistic profit math calculations in a business setting to separate what really works from imagination, pointing to the intersection of gains vs cost. The operators have done the math, they have been ready for anything that moves the needle significantly to better profit for quite a while, but apparently it will take something more than upgrading the truck.
  - bArray 2y ago
    > meaningful and maintainable engine modifications have already been implemented. In the last 10 years alone, engine efficiency gains are really being made. I work with people who literally do this stuff. Not all improvements that can be made have yet been made. It was just 2007 that VVT was used in Caterpillar diesel engines [1]. > I'll say it again: performance and efficiency have to be balanced against cost, a large part of which is maintenance. Most engines are getting better maintenance wise. My 10 year old diesel has a significant number of sensors that allow it to predict issues before significant maintenance is required. These kinds of improvements should significantly improve reliability. > The operators have done the math, they have been ready for anything that moves the needle significantly to better profit for quite a while, but apparently it will take something more than upgrading the truck. It's a little more complex than that, it will be investment vs return. If anybody can innovate in this area, Volvo are a good candidate. I personally liked their (petrol) modular engine design [2]. I personally liked the B5254T3 with the Ford modifications. [1] https://en.wikipedia.org/wiki/Variable_valve_timing https://en.wikipedia.org/wiki/Variable_valve_timing [2] https://en.wikipedia.org/wiki/Volvo_Modular_engine https://en.wikipedia.org/wiki/Volvo_Modular_engine

by uticus 2y ago

jrmg 2y ago

It sounds like 7 percent of the 10 percent efficiency gains are from aerodynamics. I expected (probably naively) engine changes to play more of a role.

SAI_Peregrinus 2y ago
Diesel engines already have very high compression ratios. Compression ratio directly correlates with the ratio of temperature at combustion to the temperature outside the engine, which is the limiting factor in the Carnot efficiency. A gasoline engine will be able to get up to maybe 12:1 before knock is an issue, high-efficiency diesels can hit 25:1. Gas turbines can hit even higher ratios, but are far more complex & expensive (e.g. the GE GEnx-1B78/P2 turbofan has an overall compression ratio of 58 and thermal efficiency of 58%, but it has a list price somewhere around $20 million and is bigger than the entire truck cab).
uticus 2y ago
If you noticed, the article talked about aerodynamics in terms of frontal area and side fairings - on other words, the parts of the tractor interacting with the airstream. The trailer's leading edge is, well, a large, flat, un-aerodynamic rectangle. Lots of potential for aero improvements there. I sometimes see boat-tails etc attached to trailers, but my understanding is that they are usually attached (an unattached at destination) by tractor owner, as trailer owner doesn't pay for fuel costs. Could be wrong on that though.

bArray 2y ago

> I should lastly add, maxed out on performance when balanced against maintenance. Like, I could put a very performant F1-type high-tech engine in one, and possibly eke out some performance gains. But the overall schedule and cost will negate any fuel savings, not to mention the added hidden environmental burden of maintaining exotic frail engines. This would just be a flat rejection to any engine modifications at all. I suspect they would still be just as reliable and no more exotic than any other engine. And if want to go down the route of unmaintainable, I think we should discuss electric trucks. Each part is coded to work only with specific parts, insane costs to repair/maintain, no real standardization to any part, quite dangerous to work on, etc. The environmental burden of those is going to be insane.

uticus 2y ago
> This would just be a flat rejection to any engine modifications at all. I suspect they would still be just as reliable and no more exotic than any other engine. Not a flat rejection to any engine modifications, but an acknowledgement that meaningful and maintainable engine modifications have already been implemented. I'll say it again: performance and efficiency have to be balanced against cost, a large part of which is maintenance. There's nothing like simple capitalistic profit math calculations in a business setting to separate what really works from imagination, pointing to the intersection of gains vs cost. The operators have done the math, they have been ready for anything that moves the needle significantly to better profit for quite a while, but apparently it will take something more than upgrading the truck.
- bArray 2y ago
  > meaningful and maintainable engine modifications have already been implemented. In the last 10 years alone, engine efficiency gains are really being made. I work with people who literally do this stuff. Not all improvements that can be made have yet been made. It was just 2007 that VVT was used in Caterpillar diesel engines [1]. > I'll say it again: performance and efficiency have to be balanced against cost, a large part of which is maintenance. Most engines are getting better maintenance wise. My 10 year old diesel has a significant number of sensors that allow it to predict issues before significant maintenance is required. These kinds of improvements should significantly improve reliability. > The operators have done the math, they have been ready for anything that moves the needle significantly to better profit for quite a while, but apparently it will take something more than upgrading the truck. It's a little more complex than that, it will be investment vs return. If anybody can innovate in this area, Volvo are a good candidate. I personally liked their (petrol) modular engine design [2]. I personally liked the B5254T3 with the Ford modifications. [1] https://en.wikipedia.org/wiki/Variable_valve_timing https://en.wikipedia.org/wiki/Variable_valve_timing [2] https://en.wikipedia.org/wiki/Volvo_Modular_engine https://en.wikipedia.org/wiki/Volvo_Modular_engine