New Fuel Economy Information site

[mpgmike]

Please ask in the X-Prize Sonata thread. Let's keep the topics separate.

[RealityRacer]

Okay. Just posted my questions there on the Xprize thread. This is fascinating information. Please let me know, I am very interested in doing these installations/modifications.

[mpgmike]

Since the topic of emissions has come up numerous times, let me say that we take a tough stance on that subject. In fact, we ourselves use an EMS 5003 5-gas emissions analyzer with Lab View software for our in-house testing. We have found that if we genuinely improve combustion efficiency, emissions go down and fuel economy goes up. Here is the Emissions page.

[redpoint5]

Combustion efficiency is only one of many factors in overall engine efficiency. It's also one of the more efficient aspects of modern engines, meaning even if we could achieve 100% combustion efficiency, overall engine efficiency would not drastically improve.

As I pointed out, gasoline engines could easily be made high compression like a diesel engine and gain efficiency, but that causes unacceptable increases in certain pollutants.

[RealityRacer]

Redpoint,
Engine efficiency is different from combustion efficiency. We stand to gain incredible efficiency increase by speeding up the burn and massing pressure on the piston between 15 degrees and 30 degrees after TDC. I have force vector calculations to support this claim.
Essentially, Combustion efficiency converts to Mechanical efficiency and reduces thermal losses since less fuel needs to be burned.
Instead of massing pressure on the piston during the critical crank angle degrees, fuel is burned in the catcons at 1800 degrees Farenheit in the upstream and downstream catcons. Seems like lots of waste to me that could be reduced.

I posted this earlier:....
According to Fueleconomy.gov website here are the stats that seem correct:
Petrol vehicles are 12% to 30% efficient,
Engine losses: 68% to 72% (thermal losses 58% to 62%),
Wind resistance: 8% to 12%,
Rolling resistance: 4% to 7%,
Braking: 4% to 7%,

So that would make engines overall 28% to 32% thermally efficient.
Combustion losses: 3%,
Friction losses: 3%

Discounting pumping efficiencies, we can improve engines theoretically by 64% to 68% (adding thermal, combustion and friction losses).
Compare that to 8% to 12% wind resistance losses.

[Ecky]

Most modern gasoline engine designs are near 40% efficient, and nowhere close to 12%. Even the big pushrod cam-in-block V8 in GM's Corvette, which lacks cam phasing, is in the mid 30's %, and modern transmissions keep engines in that range much more of the time.

Unfortunately, burn speed is asymptotic, and we're pretty far along that already. Smaller combustion chambers improve burn speed, as does increasing pressure (compression or boost), but you run into knock limits with gasoline and have to use a different fuel.

I think Mazda is thinking along the right lines with their compression ignition gasoline engines. You can largely bypass the inherent losses of the burn speed of gasoline by intentionally causing detonation at the optimal crank angle (which ends up being later than the current target of ~18%). Without doing this, we're effectively pretty close to the limits of gasoline engines. Maybe not "combustion" engines, but specifically those that rely on burning gasoline.

Going above... maybe 60%, is highly improbable, unless we start using exotic materials for engines. By simply compression air (nevermind combusting gasoline) you heat up the charge, and that concentration of heat then conducts through the piston and cylinder walls, and a large chunk of it is lost, just by virtue of having been compressed. Add to that, you will never extract 100% of energy from expansion. As long as what comes out of an engine's exhaust valves is above ambient, you're losing a huge amount of energy in the exhaust. Even combined cycle power plants, which concentrate waste heat and run it through the system once or even twice more, are only up around 60%.

Burn speed is not low hanging fruit in modern engines.

[mpgmike]

Ecky, I agree with you... to a point. First, new vehicles sport engines that enjoy efficiencies way beyond even the best offerings of 20 years ago; perhaps 50% better? New vehicles are getting better fuel economy -- not just from more efficient engines, but also lighter weight, better aerodynamics and -- wait for it:




Hybrid Electric Assist!!

If you own a brand new vehicle getting mythological mileage numbers, then maybe it is as good as it gets. However, if you rely on an older daily driver, I bet there's a comfortable 40% to 60% gain in engine efficiency on the table to be had. I'd go so far as to say I bet I could squeeze at least 20% out of the most efficient brand new engine with combustion efficiency improving technologies. They may not meet EPA's OEM requirements, but I will state that part of that guarantee is that actual emissions will at least not increase; but may actually improve.

For typical Ecomodders, older vehicles = cheaper vehicles. From what I've seen, at least 75% of the enthusiasts that congregate these pages are working on something at least 10 years old. So my claim that there is room for improvement stands.

[Ecky]

Originally Posted by mpgmike

Ecky, I agree with you... to a point. First, new vehicles sport engines that enjoy efficiencies way beyond even the best offerings of 20 years ago; perhaps 50% better? New vehicles are getting better fuel economy -- not just from more efficient engines, but also lighter weight, better aerodynamics and -- wait for it:




Hybrid Electric Assist!!

If you own a brand new vehicle getting mythological mileage numbers, then maybe it is as good as it gets. However, if you rely on an older daily driver, I bet there's a comfortable 40% to 60% gain in engine efficiency on the table to be had. I'd go so far as to say I bet I could squeeze at least 20% out of the most efficient brand new engine with combustion efficiency improving technologies. They may not meet EPA's OEM requirements, but I will state that part of that guarantee is that actual emissions will at least not increase; but may actually improve.

For typical Ecomodders, older vehicles = cheaper vehicles. From what I've seen, at least 75% of the enthusiasts that congregate these pages are working on something at least 10 years old. So my claim that there is room for improvement stands.

Honda and Toyota hit 40% efficiency in the 90's. 60mpg+ was achievable 30 years ago with various Civics, Corollas and Suzukis. GM's Ecotecs are probably on-par, and made their appearance in 1999. Aerocivic at its peak was delivering over 100mpg at highway speeds, from a 1992 engine, whose design originated in... '84, I think? Certainly in the 90's there were still dinosaur engines still making it into production vehicles (I'm looking at you, Ford 300) but it was the exception.

[mpgmike]

Ecky, is your point that none of the stuff I'm sharing could possibly work?!?

[Ecky]

Originally Posted by mpgmike

Ecky, is your point that none of the stuff I'm sharing could possibly work?!?

No, my point is that combustion efficiency is almost certainly not how it works, if it does work.