Diesel Auris beats hybrid Auris

By the way, we have on our forum a member that got first an Auris 90Hp Diesel for some few months, waiting for the Auris HSD. Driving the same routes and same driving style, he got the same fuel consumption 4,7 lt/100km. But in Eu diesel costs some 8% less than gasoline.

 

It was 2011 that one of the italian leader company (same that fiat partly uses for their cars) presented a Fiat Bravo diesel with a CNG conversion. Not very clever, i think they are forced to use a mix of just 40% CNG and the rest is diesel.
On truck, it gives more massive advantages.



Landi Renzo

 

Natural gas and propane need a spark to ignite. Converting a diesel vehicle, after manufacture, to run on them 100% will take more time and cost, than converting a gasoline one. CNG injection on a diesel truck costs less, and it does clean up the exhaust some. Plus, you aren't tied to limited CNG stations.

Chevy offers a bi-fuel gasoline and CNG Silverado and Impala. Ford has a conversion prepped option on some of their trucks that will make converting to 100% easier. These are all gasoline engines. With natural gas being higher octane than gasoline, this means the full potential of CNG is lost if the compression ratio is set for regular, 87 octane, gasoline. As for commercial trucks, the majors do offer models, but I don't know if they are converted gasoline or diesel engines, or if the conversions are more in depth, like increasing the CR of a gasoline ICE for CNG.

The real hurdle in the US is refueling stations. There isn't many for public use to support passenger cars. It would be great if we could get more localized truck fleets on it. The cost of a private station for such is easier to justify than a public one.

Do you grill with gas or charcoal?
Most of the diesel stink comes from the sulfur content. ULSD smells better than the old stuff.
Any sulfur natural gas may contain is removed before it gets to the customer. Without the odorant, it doesn't have a smell. With the lower emissions, a CNG vehicle should emit less small than a gasoline one.

 

Maxwell61, great and cheap LPG conversion, what about valves lubrication? Are you not worried?

I read that Diesel LPG/CNG conversion can make diesel car cleaner, it reduces PM, but I have my doubts about NOx formation in such a engine.

 

On passanger cars, ther's an interesting FIAT experience on an MPV of some year ago, the Multipla (an odd but smart car). It was available on a bifuel (gas/CNG) version and a monofuel only CNG version with the compression ratio optimally set for CNG: well the difference in FE and performance was pityfully small (a bit unexpected) and the monofuel did'nt got any sale success, even in a country like Italy, with plenty of CNG refueling stations.

Yes, this is your US problem....no CNG strategy for passenger cars. The home refuelling system as the one proposed from Honda is not really a solution, and costs electricity to run and is a low pressure long job.

I've also read many times of unbelievable extra price for the dual fuel system in US and this is puzzling: the tecnology is extremely cheap and simple and no justification whatsoever can be found. Other than a precise will to keep the tecnology away from the crowd.

FCA and VW sells in EU their quite large selection of in-house dual fuel cars, LPG or CNG, with a very reasonable overprice, more o less the difference btw a gasoline or diesel engine. You could have it tomorrow.

 

No, i'm not, for several reasons.

First the system is fitted with the so-called "micro-injection" of gasoline if certain parameters are met: injection time and RPM, when the engine is on a heavy load that can trigger high temperatures on the valves. Actually not the Engine Load per se.

Second, a wide range of LPG/CNG applications, both on Prius gen2 and 3, passed without any problem the mark of the 100,000 km and in some case of 300,000 km.

Third, the typical ICE temperatures of the hybrid tends strongly on the cold side, especially in EU without too many long stretch as in US, for example, and a lot more of city driving.
But the most useful bit is the Atkinson cycle: the problems with the valves in LPG/CNG applications is on the exahust side, due to the still present combustion flame when the valve opens; the Atkinson have exhaust gas with a particularly poor energy content (infact cannot be turbocharged other than using a volumetric compressor) and this happen to make safer (to high temp) the exhaust valves more than any other engine.

Edit: "lubrification of the valves" is total misconception. The problem is high combustion temperature, higher with LPG and CNG than gasoline. As a matter of fact, the alleged "lubrification system" sometime ago fitted with the aftermarket gas system, demonstrated their total unusefulness and are now mostly no more used...

 

Some few Euro6 have SCR+Urea, i can remember Peugeot 1,6 tdi but there are others. But they are all Euro6; i guess that's the way they could pass from euro 5 to euro 6....

 

Diesels make more NOx because they run lean. They run lean because there is no throttle plate; they control output by fuel flow. The lack of a throttle plate improves efficiency by eliminating the pumping losses a petrol engine has when a vacuum is formed behind a partially opened throttle plate. It does mean that there is an excess of oxygen in the engine for most of its operation.

NOx is produced when there is excess oxygen in relation to the amount of fuel to be burned, and high heat. Any ICE can produce NOx under those conditions. Petrol ones can limit the amount of air getting in by the throttle plate. So they'll have only enough oxygen to burn the fuel, and no excess to form extra NOx. If a diesel to CNG conversion involves installing a throttle plate, it should produce NOx in the levels of a petrol.

What about the output of those CNG engines? Potential fuel savings may have gone elsewhere.

Honda dropped the home refueling idea when some residential NG supplies turned out to be too wet, and it lead to corroding the tanks and fuel system.

I believe the extra cost comes from stricter regulations and certifications concerning the systems. Tried looking for the cost of GM's bi-fuel system. For the pick up truck, it appears you have to go through the fleet system to find any info. The Impala's release has been delayed. Looks like next summer.

 

The link for the complete tech card are:

The Dual Fuel : http://www.metanoauto.com/modules.php?name=Forums&file=viewtopic&t=48
The CNG only : http://www.metanoauto.com/modules.php?name=Forums&file=viewtopic&t=52

Basically:
92hp vs 95hp, same revs
130 Nm vs 133hp same revs
5,9 vs 5,2 kg/100km FC
157 vs 160 km/h top speed
CO2 150 g/km same for the 2

Sounds inconsistent, with a gas fuel on board, certification and rules are tight everywhere. I've read of extra 5000 $ or so for a CNG version in US, commonly some +2000 $ in EU for a factory CNG version as Golf TGI, it must be something odd your side of the pond for CNG cars...
And something strange for Honda in EU: altough there's the biggest market of the world for CNG in Germany and Italy and Spain, the Civic CNG is not imported/produced....

 

In the US the tanks have to rated for a 250 bar pressure (50 bar more than EU ones), and they also have to be warranted for 20 years, driving the price to the sky. Just one small tank kit is 3000 $, without VAT and without the ECU/Injectors WT1659 Type 2 CNG Cylinder - Gas Cylinders and Natural Gas Tanks

 

When this bi-fuel Impala finally gets to the dealers, it will be the second factory CNG car we have had for private sale. Before that, we had, the now discontinued, Civic CNG, which wasn't a large sum more than the petrol model.

The $5000 figures you are hearing are likely for conversions. Without public stations, CNG is really only of interest to fleet operators.