My bet is that the 273 V8 running slightly slower rpm would match the 3.9V8 in 'brake specific fuel consumption' because of the stroke difference and piston speed friction....but compression ratio differences will dominate.
Does a slant 6 variation have a better rod/stroke ratio that gives a slightly better force application angle at 10 degrees past top dead center? My guess is that slant 6 is slightly superior to the 3.9V6 here...but it is a small effect.
What are the pros and cons of V6 vs I6 vs V8 in terms of detonation resistance which is dominated by cylinder head design?
Back cylinders 7 & 8 of both LA and Magnum V8 seem to have cooling problems due to improper flow division...does the V6 have less problems and more consistent cylinder to cylinder temperatures?
Traditionally the middle cylinders of V8s that put the exhaust ports together in the center of the cylinder head have a hotspot...does the V6 have an advantage here?
For ultra high compression ratio at cruise rpm there probably needs to be some coolant system tweaks like are explained in the last chapter of 'How to Build Big Inch Mopar Small Blocks' .....any suggestions and ideas ?
If the line has been crossed and other engines besides the 273 V8 are options, why not a Motori diesel from a Jeep Liberty?
Motori also makes a V6 diesel version of the I4 used in the Liberty.....I think it can be legally brought into the USA as a tractor engine....
Motori is/was 51% owned by Roger Penske and 49% owned by DC subsidiary Detroit Diesel...and I am not sure if Daimler retained Detroit Diesel or spun it off to Cerberus...anyone know for sure?
Keep in mind that it is not really MPG we are after it is Cost Per Mile which is Fuel Cost divided by MPG.
Right now natural gas is $8 per million BTU cost. That is about equivalent to 80 cents per gallon of gasoline, since the typical gallon of 87 octane varies in the 107,000 to 120,000 BTU per gallon range....so a million BTU's is about ten gallons worth.
Chrysler built a considerable number of Compressed Natural Gas (CNG) Magnum 5.2 V8s and sold them to US Federal Agencies during the mid 1990s. Many of these CNG 5.2 V8s are now in junk yards.....but these are justly famous for blowing plenum gaskets if there is a backfire on the intake side of the engine. Perhaps a MPI intake manifold would cure this?
I suspect that for the next ten years or so natural gas will be the least expensive fuel that can be used in vehicles relatively easily. Honda sells a CNG Accord you can test drive along with a home compressor kit to fill the tanks at your own home.
Coal is only about $2 per million BTU. That is equivalent to 20 cents per gallon gasoline.
My grandfather built and ran a 'water gas shift reactor' kit using Council of Fuel Research plans (CFR was the for runner to the US Energy Department) during World War II. This device mounted on the rear bumper and turned coal/charcoal/coke into carbon monoxide gas (highly poisonous if not confined and even small amounts impair driving behavior) mixed with hydrogen gas (the H2 gas has most of the BTU) which was then fed to the engine for sparkplug ignition. A computer controlled version of this with an oxygen sensor to control air to fuel ratio would work even better than the 60 year ago technology. Somewhere, probably at the South African company SASOL there is an engineer who could design this modern version to work effectively.
