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."

Comments

Rudolph Diesel

[LiENUS]

Congratulations You've discovered the same thing as Rudolph Diesel except that you don't quite have it right. You don't need to use ethanol or port injection ditch both of those and use good ol fashioned vegetable oil. 0 preignition and you can turn the boost way up on a tiny engine.

Not the final solution

[dal20402]

I suppose my first question is, when the owner inevitably lets the ethanol run out, what happens? Can the engine computer dial down the boost enough to prevent detonation? Or does the engine just have to shut down?

That aside, it's always great to improve internal-combustion efficiency, but the real solutions will have a more dramatic effect than this. My own view is that the solution should be a plug-in series hybrid with about 60 miles of electric-only range and the ability to run maybe 400 more with the engine providing generator power. This would not seriously compromise the essential attributes of modern cars, while *dramatically* (think 80% or more) improving their fuel economy in many real-world usage patterns.

Then we should have nuclear power behind all those 220v outlets... and 90% of cars should be much smaller, with people able to obtain bigger trucks for big jobs on demand from time-share or rental companies... a guy can dream, can't he...

Re:Old

[AP2k]

Even still, water and alcohol injection used to cool the charge is not new, and has been around since the 30's.

Whoever wrote the article doesnt understand why SUVs and trucks have big engines. Its not because they are powerful, its because they need lots of torque. You can pull a trailor up a hill in an S2000 just like you can a road tractor, but the tractor will use much less fuel and less wearing of the engine doing it.B enignes arent going anywhere in SUVs any time soon, despite this seemingly "revolutionary" new technology.

I predict this will end up as a failure just like the last time an engine manufacturer tried this: http://en.wikipedia.org/wiki/Oldsmobile_V8_engine# Turbo_Jetfire

No matter how novel the technology, when the product's life depends solely on the customer, your product wont usually stay on the shelves for very long.

Re:Old

[drinkypoo]

This is exactly like water-injection and it's why we don't see water-injection in vehicles. No one wants to have a separate tank that we need to remember to fill-up, and the 10% increase provided by water just isn't enough. This is the same story except it's ethanol, not as easy to find as water, and it's 25% better mpg instead of 10%.

But the story is different because the system will know what to do when it runs out of ethanol, which is to say retard timing and reduce mileage and power output until you add more ethanol. Water injection is aftermarket and usually not compensated for automatically.

The mileage improvement is pretty compelling and I think we'll see it implemented if fuel prices rise much more.

Re:Check out the 07 MINI - it has this stuff alrea

[GameMaster]

You either need to read the article or, if you have, brush up on your reading comprehension skills. The technique used in the article is supposed to allow them to push the turbo pressure much higher than any modern car can handle, even when using high octane fuel. They're talking about using a separate direct injection system to pump a small amount of pure ethanol into the cylinder out of phase with the gasoline. It would cool the cylinder enough to stop knock when the gas is injected at extreme pressures. Supposedly, you would have to replace the ethanol about as often as you have to replace the oil (every few months).

Next time, please try reading the article instead of seeing "ethanol" and "turbocharger" in the summary and shooting your mouth off.

-GameMaster

Buy a direct injection turbo charged car today!

[Spoke]

People have long known that ethanol fuels have high octane ratings (the measure of how knock resistant a fuel is).

People have also long known that turbo charging an engine is a great way to extract more power out of a small engine.

People have also known that direct injection allows you to reduce the tendency to knock since it lets you inject fuel into the hot engine at the very last second - reducing the amount of time the air/fuel mixture has to heat up.

And guess what? Mazda produces cars today that has both direct injection and is turbo charged. For example, the MazdaSpeed 3.

It's 2.3 liter engine produces 263hp and 280lb/ft of torque and has an EPA fuel economy rating of 20/28mpg. So yes, while it does provide good power and decent gas mileage, it's nothing earth shattering compared to turbocharged cars without direct injection.

The engine has a very high compression ratio for a turbo charged gasoline engine (9.5:1), especially one that pushes over 15psi of boost into the cylinders. That is direct injection working for you.

For example, the slightly bigger turbo charged 2.5 liter Subaru WRX engine has a compression ratio of 8.4:1 and maximum boost of 11.6psi is rated at 230hp/235lb/ft of torque (though it is admittedly underrated) with similar fuel economy as the Mazdaspeed 3 considering that it is all-wheel-drive (20/26mpg EPA). The more powerful WRX STi has the same 2.5l displacement, 8.2:1 compression ratio and a bigger turbo pushing 14.5 psi is rated at 293hp/290lb/ft of torque but less fuel economy, 18/24mpg.

Unless there is a lot of potential still to be found by combining these 2 technologies, I see it as more of an evolution rather than a revolution. Perhaps a 1.0 liter engine would be able to muster 120+ hp/torque but I find it hard to believe that it could achieve mileage ratings significantly higher than a hybrid. And you still can't turn the engine off when idling or coasting down hill.

So how about a direct-injection, turbo-charged, atkinson cycle hybrid and combine the best of all technologies?

This is not news, or a discovery.

[a4r6]

For anyone that knows their stuff about car engines, this article is a joke.

Both turbocharging and direct injection are preexisting technologies, and neither looks particularly impressive. Indeed, used separately, they would lead to only marginal improvements in the performance of an internal-combustion engine. Really? So there aren't people slapping large turbochargers on little 3 liter supra engines and increasing the engine output 5-fold? Or is that only marginal?

That aside, the problem with this is that a turbocharged engine at full output is very inefficient. A larger naturally aspirated engine will always be more efficient than the small turbocharged engine of the same maximum output. That's because a lot of energy is wasted compressing the intake charge, more than can be made up for with the displacement decrease, even with the newest fanciest garrett turbos. The only merit efficiency-wise of turbo engines is engine efficiency at low loads (when the engine is not under boost) relative to the maximum output. There is obviously a balance to be struck here, and that's why 18 wheelers have big v8's with turbo chargers, rather than even bigger engines or smaller engines running under high pressure. Designing a motor vehicle is always a balancing act, and in most cases a turbo is not helpful because of the cost, reliability and other shortcomings versus the benefits.

Recently, car makers have started using direct injection to combat preignition that can damage an engine. It allows them to run leaner fuel mixtures, higher compression and more aggressive spark timing, improving the power/efficiency of engines. Direct injection has the exact same benefit with turbocharging. There are no compounded benefits from mixing the two technologies.

Re:brief review of article

[Anonymous Coward]

Who gives two shits about making petrol engines 25% more efficient when Diesels are already 50% better in practical applications.

Once again, this just shows that what Americans don't know about car technology could just about be crammed into the Grand Canyon.

Volkswagen already have quite a few turbocharged FSI petrol and Diesel engines - take a look at how efficient they are before swallowing this MIT bullshit.

Re:Old

[RingDev]

"...limiting their power"

Harsh. Apparently someone hasn't been keeping up on Diesel Technology lately. You know it was an Audi Diesel that one the last LeMans right?

I dirve a little VW Golf TDI. 115hp is nothing special, but 175 lbs/ft of torque is enough to get the car moving in a hurry. The car is almost as quick stock as my '88 Fiero with a 3.4l V6 (about 180 hp and 175lbs/ft).

When you have an engine that can (lightly/medium modded) put out 250 lbs/ft or torque from 1800rpm to 3500rpm, the concern is less about RPM and more about Gearing and shifting. Have you seen the new VW/Audi dual clutch manual automatic trannys? Their 6 speed DSG auto transmissions can upshift in 8ms. With that wide of gear range, and that fast of shifting, having a somewhat* limited rpm band is not an issue.

*I say somewhat because the vast, vast majority of drivers will never spin their engine over 3500 rpm. Hondas, Subarus, what have you, they are all designed (stock) as commuter vehicles. And if you have to turn 7k rpms to get your car off the line, it's not going to hold up to daily driving.

-Rick