A New Lease On Internal Combustion

Somnus suggests we check out the latest issue of MIT's Technology Review, where researchers describe how they can dramatically boost engine output and efficiency by preventing pre-ignition, or "knock." How they do it: "Both turbocharging and direct injection are preexisting technologies, and neither looks particularly impressive... by combining them, and augmenting them with a novel way to use a small amount of ethanol, Cohn and his colleagues have created a design that they believe could triple the power of a test engine."

Old

[jevring]

Wow, this is yesterdays news. People in the tuning industry have been controlling "knock" in various ways for a long time. Either by raising the octane number on your ful (add ethanol or booster), so that you can had move advanced ignition timing, or simply retarding your timing and using the same octane rating fuel as you normally use

Why stick with petrol?

[shplorb]

This sounds an awful lot like a modern diesel engine. Modern diesels are turbocharged and use common-rail injection to achieve insane pressures at the injector heads (for really fine atomisation of the fuel), which directly inject into the cylinder. I believe the newer engines even stagger the injection during the compression and combustion cycles too to achieve more power and cleaner burning.

(NB: I'm not a revhead so I might be talking shit)

I don't get it

[roman_mir]

How do we go from this:

A vehicle that used this approach would operate around 25 percent more efficiently than a vehicle with a conventional engine.

to this: ...Cohn and his colleagues have created a design that they believe could triple the power of a test engine, an advance that could allow automakers to convert small engines designed for economy cars into muscular engines with more than enough power for SUVs or sports cars.

does a 25% increase in efficiency translate into tripling the power output?

Since when is this news

[Ninety-9 SE-L]

Um, we figured this out decades ago. Race engines types of higher octane solutions to raise boost and compression. Methanol, Ethanol, Alcohol, Race fuel. It's simple chemistry. Pure gasoline packs more energy but is unstable, additives like Ethanol raise octane ratings making the fuel more stable but packing less punch (energy per volume of fuel). E85 is equivalent to 108-116 octane, good stuff, but not for a Buick. Throw it into a regular car and you need to suck down more fuel to get the same output, however, throw it into a high compression or high boost engine, and you can more effectively make power. High compression engines are definitely more efficient, ask me how I know. I run 12:1 on 93 octane and get 37MPG on the highway, my car also runs 13s at the track. Before I went high compression, I made about 30MPG on 87 Octane. Calculate this out and I save money even though I'm paying 20c more per gallon. This is racing technology and it's not even remotely new. The only thing that's new is E85 is available at more places and cars are being set up to run E85. If you put E85 in a regular car, you're an idiot. If you buy a car that's supposed to run E85, make sure that it's set up to make the most out of the fuel and never go back to standard gasoline.

Kids and car enthusiasts did this decades ago

[Oz0ne]

Seriously. Direct injection, fine tuned control of timing, and turbo charging all put together is what you see in a large number of hobbiest race cars. Drag, autocross, whatever. A lot of times they'll skimp on tolerances thus reducing the reliability of the engine, but it's not at all uncommon to take a solid normally aspirated engine and triple it's output with some good planning and bit of machine work.

I've personally never added a turbo where there wasn't one before, but I HAVE done machine work, timing work, and injector work. I've taken a car from 220 hp to 290 hp with no detriment to the mileage, just better fuel/air mixtures and precise timing. It doesn't surprise me at all that people who've actually studied combustion instead of working on it for fun have been able to triple the output.

What's surprising is how inneficiently tuned a lot of engines come from the factory.

Re:Not the final solution

[Rei]

and 90% of cars should be much smaller,

Americans would never accept that. You might as well just say "and fairy princesses should fly down from candyland and give us all ponies to ride."

I think a more realistic possibility is that vehicles will just get much lighter. As an example, if Boeing can make the Dreamliner out of carbon fibre, perhaps it's not that long before we start seing reasonably priced, mass-produced carbon fibre car bodies. There's also reasonably good odds of significant price reduction in titanium and titanium alloys, and aluminium use is becoming more widespread in the automotive industry.

My ideal "dream" situation? A "grid" transportation system, in which vehicles are networked together without any humans behind the wheel (except "offroad"). electric vehicles which get their power from the road (standing wave transmission, perhaps). Autoconvoying and optimized speeds to greatly reduce traffic, increase road capacity, and reduce wind resistance. With vehicles much lighter from being pure-electric without need for even carrying the power source, high speed "bulletways" with coils of wire embedded in them, so that vehicles with halbach arrays (magnetic arrays with highly lopsided fields -- near double-strength on one side, near zero on the other) can employ "Inductrac" style maglev, eliminating rolling losses and having very little maglev losses at high speeds.

  * Greatly reduced wind resistance and no rolling losses.
  * Still your own, personal vehicle (the profiles would likely be a bit different from present day for optimal convoying, though)
  * Never having to drive. Play, sleep, work, chat, whatever during the trip.
  * Less need for roads eating up cityspace
  * Less traffic
  * Much faster travel, to the degree that airlines would be needed much less often.
  * Much less energy use
  * Independent of oil.
  * No need to even be in your vehicle while it's moving -- automated delivery, automated pickup of your kids or groceries (if the store will load for you), etc.
  * The great economic benefits of travel being automated and fast.
  * Much less space used up downtown for parking, as vehicles can drive themselves to and from less convenient parking without you.
  * No speeding tickets
  * Very few accidents (no human error, no drunk driving, etc)

The benefits go on, and on, and on. Unfortunately, we have all of our existing infrastructure to deal with. Thankfully, it can be moved towards in stages. First hybrids, then plugin hybrids, then electrics, then grid-power electrics. First radar-assisted braking (like we have now), then wireless transponders to assist traffic, then increasing wireless information exchange and planning. Once vehicles are light enough, all-electric, and are designed for high-speeds with automated operation, inductrac-style maglev becomes realistic for long stretches.

Re:Rudolph Diesel

[LiENUS]

It's actually more like 100% preignition in a diesel, but they're built to withstand it without grenading. By design its impossible for diesel to have pre-ignition unless somethings wrong. so its 0% preignition, there is however 100% detonation which is a completely different thing. Pre-ignition is where your intake charge and fuel mixture ignite before your spark plug fires. Since diesels have no spark plug there is no spark plug firing event however intake charge also lacks fuel. So it can't ignite before it is supposed to. The fuel is injected after the compression stroke has already been made and the fuel ignites as soon as it injects, thus 0% preignition 100% detonation.

Re:Not the final solution

[Osty]

* Never having to drive. Play, sleep, work, chat, whatever during the trip.

I'm not sure I'd put that in the "benefit" column. I enjoy driving. What I fear most when people start talking about future transportation technology is that almost everybody assumes that driving is a chore and nobody should have to do it anymore. While it would be great to get the people who don't like driving off the road (the people who eat, read, do their makeup, change clothes, etc all while driving), if the solution involves removing my own ability to drive then I'm against it.

Note that I didn't say anything about what I would drive. Electric, hybrid, magnetic, petrol, whatever, I'm fine with it as long as I'm allowed to stay in control of my personal vehicle.

Re:brief review of article

[dgatwood]

I missed the "every few months" part. So that removes the safety concern. It still doesn't address the other problem, though.

Jiffy lube says to change oil my oil every 3,000 miles or three months. The manufacturer says 5,000 or six months. Even if I forget to change it and go 7,000, my car does not stop running because my car does not burn oil. If yours does, this probably indicates that your rings are worn or some such problem. Indeed, I could drive for 400,000+ miles [synthetic-...ilters.com] on synthetic oil in cool weather without my car suddenly stopping. That's a little extreme, but you get the picture. By contrast, if I run over the limit on changing the ethanol, the car will likely stop running. And that will either be another gauge that people will have to learn to watch or another idiot light that they will ignore and then their car will stop.

The point is that it's a significant change to the way the vehicle is maintained, with no real benefit when compared with today's alternative fuel technology, and it won't be out for four years, by which time fuel cells should be leaving such designs in the dust.

NiMH Batteries?

[kad77]

So producing hundreds of thousands of tons of NiMH or LiON batteries for cars is better for the planet than buying a 40mpg gasoline vehicle...

I've got some new crack-vitamins for you!

Re:brief review of article

[Andy Dodd]

"And that will either be another gauge that people will have to learn to watch or another idiot light that they will ignore and then their car will stop."

With modern engine control systems, it isn't too hard to back off the timing and the boost when the alcohol runs out.

They'll get a "low on alcohol" idiot light, and while their car will not stop, it will run like shit and they'll go get a refill.

Re:Turbo lag, premature combustion

[Anonymous Coward]

Variable vane technology has come to small turbos that are useful for spark-ignition passenger cars so you can have quick spool-up without having a small scroll that creates too much back-pressure at higher RPMs. The vanes act like a thumb over a garden hose directing high velocity jets at the turbine buckets at low gas flow so that the scroll can be sized for the full operating range of the engine without neccesarily needing a wastegate. This means the turbo is being used fully as it was meant to be, as a scavenger of waste heat that would otherwise be dumped out the exhaust.

The most efficient internal-combustion engine ever devised, the R-3350 radial of the Lockheed Constellation, actually geared the fluid-drive output of its 3 turbines directly to the driveshaft. The 2-speed centrifugal impeller of the supercharging was powered from the gearcase. It also used direct fuel injection. And water-alcohol injection.

As far as the alcohol injection is concerned, the description seems to imply that it is being used as a phase-change "intercooler" of sorts. (There's no 'inter' to the cooling however, maybe intracooler?) The amount of alcohol used also seems to imply that he isn't trying to claim any oxygenation of the fuel. And he seems to be specific that it's not direct fuel injection but rather direct alcohol injection during the compression stroke while the fuel-air mixture is being compressed.

Re:Why stick with petrol?

[drinkypoo]

Check out one of the new-model Volkswagen TDIs. They're back on sale even in California. Most people have a hard time even knowing they're a diesel if they don't see (or comprehend) the badging. With low-sulfur diesel you can use a catalyst, so the emissions are even quite good. (And if you run on veggie oil, or biodiesel, they're even better.)