MIT Researcher Explains Why Fuel Economy is Still Low Despite Advances in Fuel Efficiency

Similar to hydrogen, the answer depends immensely on how you make the stuff.

Corn ? Uggh
Sugar beets in Brazil ? Better, but the NG inputs are hard to figure
Switchgrass ? Around 1.5x better IIRC

 

The comparison, relative fuel efficiency, is only valid between an SC and turbocharging. Since the SC only requires power during on boost engine operation it is inherently more fuel efficient.

But then we are left with the second half of the boosted engine efficiency (lack of) equation, derating/detuning of the engine for non-boost operation in order to provide the compression margin required "on-boost".

But what if we could find a way to run a DFI engine at the 12:1 (14:1[??]) standard...??

Provide "super-cooled" boost pressure.

Assume we have a liquid-to-air intercooler (fully insulated from the engine compartment heat) and a cannister, insulated reservoir, both filled with anti-freeze. A/C refrigerant would be used to continuously maintain the anti-freeze at 20F and a small motor/pump maintains a continuous flow through the intercooling system.

Then we add a positive displacement SC wherein the SC RPM can be independently controlled using the Toyota CVT/PSD concept. No throttle plate. The SC's RPM is used to "limit" atmospheric pressure below "WOT"/off-boost, AND provide BOOST otherwise.

The outflow from the SC is "piped"/ducted directly to the engine intake AND the intercooler intake with a "blend door/vane" used to determine the "mix" entering the engine intake.

Using the above system, Super-cooled, pressurized intake airflow, what might be the "on-boost" limit for EFFECTIVE compression ratio..??

20:1....??

And how small, low volume, might the core Atkinson cycle engine be made ??

Considering passenger car ONLY use, the A/C "overhead" might well be minuscule.

 

Your links are labelled "Browser Warning" and do not follow through.

 

I finally found a workaround for the "Browser Warning" and was able to read the articles.

Frustrating...The SC modification was successful but abandoned ONLY due to the high noise factor...with no FE or power measurements...???!!!

PISS.

But the more interesting aspect for me was the recognition that the primary target for FE improvement would be the hwy cruise mode.

It's also quite a shame the op didn't know to make use of the Ford EcoBoost turbo wastegate/throttle plate control transition. Wastegate remaining fully closed until the throttle plate is fully open, accelerator pedal at mid-point. Or absent the EcoBoost's "linear" control of the wastegate position the transition would be with the throttle wide open and the accelerator fully depressed or almost so.

But the same technique could have applied to the SC had not the noise factor been to great.

 

modern diesels are generally pretty unreliable engines .
What could go wrong with high pressure injectors, fuel pumps, underengineered transmissions, turbos and emission equipment? A lot... and it usually does go. Even Toyota diesels are considerably less reliable then their petrols, let alone Prius.

 

"...Modern (Passenger car) diesels are generally pretty unreliable...."

Agreed?

 

i have no experience with real trucks, but only with cars and suvs....so my own opinion can be only based on that. Are there real trucks sold with petrol engines anymore? Not in Europe.

Even commercial vehicles here have diesels, but they use smaller turbos, iron blocks, lesser pressure injectors/pumps and are generally bulletproof.

 

Sorry, I should have been more clear, I meant commerical freight hauling over-the-road trucks.

Generally bulletproof...agreed.

 

Sorry, I should have been more clear, I meant commerical freight hauling over-the-road trucks.

Generally bulletproof...agreed.