WhiteBlue wrote:The real interesting application would be using the original space of the diesel tank and not needing additional space in the boot. this way you could fit the system in already economical 50 mpg hatchbacks without compromising transport capacity. It would boost these cars to perhaps 60 mpg and cut fuel cost by 65%.
I agree completely. However, Belatti points out that only now are manufacturers starting to sell new vehicles thought for NGV, so the gas tank is already in place. As modifying the tank gas is not precisely easy or safe, at least in some south american countries we have no alternative.
Besides, I believe that in North America, NGV is not a good alternative, because NGV is less efficient from the point of view of energy and it costs more or less the same as gasoline, so there are no american cars that I know with tank modified at the factory.
WhiteBlue wrote:...In Germany the difference between gas and diesel is 0.9 €/L.
Is enough the 0.9 euros differential to save you money?
A quick check at
http://en.wikipedia.org/wiki/Fuel_effic ... nt_of_fuel gives me that regular gas has 38% more energy per liter, so unless gasoline is 38% more expensive than natural gas or biomethane, NGV is not a good alternative for your pocket.
For a diesel engine, things are worse (for NGV): a diesel engine has an efficiency of 45%, while a gasoline engine only gets 30%.
A common margin is 40% more miles per gallon for an efficient turbodiesel. For example, the current model Skoda Octavia, using Volkswagen engines, has a combined European fuel efficiency of 38.2 mpg for the 102 bhp petrol engine and 53.3 mpg for the 105 bhp — and heavier — diesel engine. The higher compression ratio is helpful in raising efficiency, but diesel fuel also contains approximately 10-20% more energy per unit volume than gasoline
http://www.fusel.com/diesel_engines.html
So, maybe NGV is a good alternative only for countries, like Colombia and Argentina, that have enough NGV for some decades more and do not want to import gasoline from other countries. These countries are giving their citizens a really low price for NGV because of macroeconomic reasons. So, unless Germany (or whatever country you live in
) starts to produce biomethane and find it can save some hard currency from going to the Saudis, I don't know if it's applicable for everybody.
On the other hand, it's a shame to keep natural gas burning on oil wells.
Chaparral wrote:... I think most people look at the $0.65 a litre for gas and then equate it back to the cost of the conversion versus the $1.60 per litre for unleaded 95 or $1.80 per litre diesel and say no Id need to drive so many kilometres over the next how many years to get my money back.
That's true even in Colombia. Most early adopters in my country have been taxis and buses, because the mileage is high enough to pay for the conversion in one year. Regular cars need 4 or 5 years to amortize the investment. As I said, an alternative is to pay-as-you-go at the gas station, but even then many people thinks that they're not going to keep their car 5 years more.
That was true, until now, when oil has increased price per barrel 5 times. Besides, my country used to subsidize gasoline and diesel, but for the last 6 years it has been dismounting those subsidies, because it has been predicted that once we ran off excess oil (to sell abroad and pay for the refined gasoline back) it was going to break the national finances
or we should build a refinery that in a few years (once oil is mostly exhausted) would have to be shut off.
