Non-hybrid cars that give Good Fuel Economy (highway)

Yes, diesel has higher theoretical efficiency. That doesn't necessarily mean it can deliver higher actual efficiency in real life, even when restricted to an atypical condition such as stead state cruising. According to our friends over at TDI club, while the VW ALH TDI has a peak reported efficiency of 197 g/kWh bsfc its steady state highway cruising bsfc at 2200rpm is about 250g/kWh. The Gen 3 Prius has a lower peak efficiency of ~220g/kWh bsfc, but thanks to its broad peak region and the variable gearing achieved through the PSD it can still cruise at highway speeds at ~230g/kWh.

This would seem to correlate pretty well with the data I can find on real world measured steady state operating MPG. This data from motortrend puts the current Jetta TDI at 51mpg at 55mph steady state.



Its unfortunate MT didn't see fit to run the Prius on this comparison, obviously would have been better to have data from as identical a case as possible. However, from Bob Wilson's endless circling, the Gen 3 Prius seems to be between 60 and 65mpg at a constant 55mph, which correlates surprisingly well to the established "60mpg at 60mph" rule of thumb many Prius owners have anecdotal noted over the years.



So it would seem that this difference between peak theoretical efficiency and actual cruising efficiency likely bears out in real world performance for steady state operating conditions. Yes a smaller TDI would have probably gotten better mpg, but likely because its doing less work not necessarily because its more efficient. According to the VCA extra urban numbers the Polo 1.2L uses about 13.9% less fuel than the Jetta at highway speeds, which might put it up around 59mpg (US) at 55mph steady state.

 

The competitions I read about were courses on public roads still open to all traffic. Just like when the team(Wayne was part of it) got the first reported >100mpg on a gen2 Prius. Wayne's daily driver is a manual 2005 Accord. His average is 48mpg. 37mpg is the highest on Fuelly for that year. He is Xcel on Cleanmpg.com

Yes, the engine got more fuel efficient, that doesn't explain how an Atkinsonized gas engine has less pumping losses than a diesel. Nearly all gasoline engines have throttle plate. At any position besides wide open, the plate restricts air flow, and the pistons have to suck air past it. Diesels don't have a throttle plate, and the cylinders don't have that restriction to work against to draw in air.

 

I was not talking about Gerdes alone, but he is one of a small select group. He has published his lifetime numbers before -- IIRC ~ 90 mpg. I'm pretty sure that was his only car, so driven wherever he wanted to go. I think he lives in Ill.

The numbers are real, just be aware of the context.

 

Not my field of expertise, but some of the ways pumping losses are reduced are discussed on one of Bob Wilson's pages here:
Modern Atkinson Engine

Note that pumping losses are not the only losses in the system, so the Prius engine doesn't have to have less pumping losses to be more efficient overall.

Rob

 

I said pumping losses, but I should have said partial-power losses. I tend to think of them together but you are right in saying that the throttle plate losses are only part of the total partial power losses.

All that said, the point remains: At low partial power the Prius has a considerably better BSFC than the diesels running around the US.

 

The Passat actually does a little better than the Jetta at highway speeds since it's running more efficiently by using urea for NOx control.

 

Over 13 years of posting the same information, what made this different?

The same outcome as ever other highway-only diesel thread was inevitable.

 

And as usual, you are wrong. Combustion is more complete in a Prius than a diesel, you just have to look at the particulate filter or the shiit coming out of the exhaust to know that. The high(er) compression ratio raises the delta T.

Actually, that notion has been debunked for years. Not that 60 mpg is bad guess, but correct for the dense fuel and all you have is a car that is heavier, less reliable, at a much higher price. Oh, and maybe a 5% reduction in energy/mile. Maybe.

You know, even though you lack understanding of basic and simple concepts, you should be able to get a clue: go through the list of hybrids on the road and count how many of the total are diesel hybrids. Do you really think TH knows what none of the diesel manufacturers have yet to figure out ?

 

The only Diesel Hybrid that I can think of off hand is the Volvo V60 plug-in hybrid. That seems to be a real all rounder, but very very expensive

Aside from that, the VW UP! or Golf diesel hybrid (not sure if either were actually produced)

 

Yup. The VW is a concept AFAIK.

Fueleconomy.gov lists 103 hybrids in the 2013-2014 US market. Diesel-hybrids: zip

I remember when TH was babbling about the Volvo. He was going to buy it the moment one became available LOL
No problem with the $75k car price, except this is the guy who thinks an unreliable car is the better value because it is a couple of thousand $ cheaper by sticker price.

He is so FOS.

 

Does your Prius tailpipe have a spotless tailpipe interior, or is it covered with a layer of black? Gasoline engines have their own particulates, but since people don't see them, they are just not concerned with them.

In the case of diesel, some of the particles are because of the physical properties of the liquid. Biodiesel produces less of them in a given engine. Other times it is because, whether deliberate modding, wear, or lack of maintenance, the engine is dumping too much fuel into the cylinder than can be burned. You will note that a smoker emits most of its smoke at starts from stops and gear shifts when there is a spike in power demand.

Diesel modders do it for the same reason gasoline ones do, to eek the most power out of the engine as possible. A rich mix means a better chance of burning all the available oxygen in the cylinder. On the ironic front, a diesel producing smoke likely isn't producing NOx during that time. It also has a cooling effect. I'm sure stock diesels, like gasoline engines, dump some extra fuel at wide open throttle for that cooling.

tl;dr version- Diesel particulates are not proof of the cycle being inefficient.

In the early years of the gen2 Prius, there was a Ford car(Reflex?) and Mercury SUV(Meta One?) diesel hybrid concepts.I don't remember any predicted fuel economy numbers, but they were PZEV for the time. The cost premium was quoted at $9000 while the Prius hybrid one was speculated at $5000. Even with cost improvements, we likely will only see a gasoline hybrid or a diesel for most car models. The additional cost of the larger battery might make the increase for diesel more viable with a PHV.

On an emissions related note, Cummings is aiming for a lower emission profile than the Prius with their 2.7L prototype.

 

I am just so amazed at all the "experts" we have here. Absolutely amazing.

 

https://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/45_2_SAN%20FRANCISCO_03-00_0294.pdf

 

How does this pertain to my point that particulate production isn't an indication of an engine cycle's efficiency? Yes, older diesels smoked, and running rich is likely the cause for most of it. I was never implying a diesel won't produce particulates outside this rich condition.

Is there a publish date for this paper? The newest reference in it was from 1999, and they used Reformulated California
grade diesel fuel (low sulfur content). Doesn't sound like it was ULSD, which produces around 8% less particulates that the previous diesel fuel.
http://www.adoptabus.org/downloads/ULSD%20FACT%20SHEET.pdf

 

You are confused.

I said that diesel PM ("soot") is ample evidence of incomplete combustion. Overall efficiency has many other factors in play, and in a modern engine used for regular driving incomplete combustion is a very, very minor contributor. So while incomplete combustion is a major contributor to exhaust pollutants, it is not an important part of efficiency discussions.

As for the reason for diesel PM, I gather that overall the engines run lean but micro-environments within the cylinder are fuel rich.

 

At what loads and rpm ?

Your statement is *way* too general