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I gotta say hyundai hit the spot with the choice of this 4 cylinder, what is it about the direct injection technology that makes it so efficient and strong ?

I can' t believe under this mid sized sedan is a 4 cylinder that's providing all the power! never once does it ever feel underpowered, very nimple and very "light" responsive feeling at the pedal! plenty of reserved power for passing lane as well!
 

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The car that my Limited replaced was a 08 Dodge Avenger SXT with a 2.4.
The performance difference in the Sonata is like night and day.
The Dodge only had a four speed auto.
Also I could only average about 24-25 mpg with the Dodge and right now I'am getting 29 with the Limited.
What a difference three years makes.
 

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I have had people ask if I had a v-6 and when I told them nope just a 4 cyc they were amazed. Great motor and I hope it lasts.
 

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While not near a direct comparison, I am driving a Dodge Caliber as a rental. WHAT a POS! It is the TRUE definition of a DOG. Makes the Sonata an animal! :laughing:
 

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DI allows higher compression ratios which boosts torque so the car feels faster. While other cars can barely squeeze 160 ft lb of torque, the 2.4 pumps out 184.
 

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i will be ready to buy in november, i have not gone to test drive the car until i am ready in fears i may make an early purchase thus hurting myself financially. Instead I have choosen to get as knoledgable as posible on the cars i am interested via online research instead. I just want to ask if you could compare the powwr to any other car you have driven what would it be? how does it match up to other 2.4's , like those found in an altima, cmary, etc. thanks. i have driven an altima several times and was very pleased with its feel. is it similar or dare i say better?
 

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I was driving an 09 Mazda 6 before this (4cyl, AT, 5 speed) and the difference is pretty awesome. The Sonata is way punchier. Just wish the steering was a little tighter..
 

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QUOTE (Bearcats @ Sep 16 2010, 09:41 AM) index.php?act=findpost&pid=356611
While not near a direct comparison, I am driving a Dodge Caliber as a rental. WHAT a POS! It is the TRUE definition of a DOG. Makes the Sonata an animal! :laughing:
I drive these almost on a daily basis, dodgy cars for sure, biggest pos ever made, and I drive a lot of cars, even a chevy cobalt is waaay better than any dodge pos. What makes me laugh even harder was a dodge advertisement on tv talking about quality built cars! HA! It's like driving a boat on wheels.
 

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I must agree with being impressed with this 4cyl. engine. All the cars I have owned prior to this one have always been 6cyl. and I thought I was gonna miss that oomph. I really wanted to go down to a 4 cyl. for the MPG which at the moment is OK for me. After reading this and the next time you're driving your car on the highway doing about 50 MPH....STOMP the gas pedal and just feel how fast this car can get up to 75 MPH (make sure it's safe to do this). Passing power galore. Now when I see a turbo I will feel a little jealous of all the power at their disposal but I can live with what I bought. Still a happy camper. :)
 

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Traditional "modern" fuel injection sprays the atomized fuel into the airstream right behind the intake valve. The piston moves down, creating a vacuum, the valve opens (not necessarily in that order by the way), the fuel is injected and drawn in by the downward-moving piston, the injector shuts off, the valve closes, and the piston comes up compressing the air/fuel mixture. Normally static compression ratio is limited in this arrangement because as the air/fuel mixture is compressed by the now-upward-moving piston, it is heated. The more it is compressed, the more it is heated. heat it too much, and it ignites. Ignite it too early and you get (pre)detonation and potential for catastrophic damage.

Direct Injection waits until the piston is at the top of its stroke, when the air (and the air alone) is fully compressed, and then sprays fuel in under extreme pressure (as much as 40-50times higher pressure than "normal" fuel injection), at which point the spark plug ignites it. As someone mentioned, this allows for higher static compression ratios (and therefore more power) because you cant pre-detonate something that is not there. It is injected at the absolute ideal moment for proper combustion at much more "perfect" atomization levels due to the extreme pressures involved which creates much higher efficiency levels (power and gas mileage).
 

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QUOTE (robspeedGLS @ Sep 16 2010, 08:16 PM) index.php?act=findpost&pid=356735
Traditional "modern" fuel injection sprays the atomized fuel into the airstream right behind the intake valve. The piston moves down, creating a vacuum, the valve opens (not necessarily in that order by the way), the fuel is injected and drawn in by the downward-moving piston, the injector shuts off, the valve closes, and the piston comes up compressing the air/fuel mixture. Normally static compression ratio is limited in this arrangement because as the air/fuel mixture is compressed by the now-upward-moving piston, it is heated. The more it is compressed, the more it is heated. heat it too much, and it ignites. Ignite it too early and you get (pre)detonation and potential for catastrophic damage.

Direct Injection waits until the piston is at the top of its stroke, when the air (and the air alone) is fully compressed, and then sprays fuel in under extreme pressure (as much as 40-50times higher pressure than "normal" fuel injection), at which point the spark plug ignites it. As someone mentioned, this allows for higher static compression ratios (and therefore more power) because you cant pre-detonate something that is not there. It is injected at the absolute ideal moment for proper combustion at much more "perfect" atomization levels due to the extreme pressures involved which creates much higher efficiency levels (power and gas mileage).
One of big advantages of GDI is that the computer has tremendous flexibility with regard to when it injects the fuel.

According to Wiki, (http://en.wikipedia.org/wiki/Gasoline_direct_injection)

" Ultra lean burn mode is used for light-load running conditions, at constant or reducing road speeds, where no acceleration is required. The fuel is not injected at the intake stroke but rather at the latter stages of the compression stroke, so that the small amount of air-fuel mixture is optimally placed near the spark plug.
• Stoichiometric mode is used for moderate load conditions. Fuel is injected during the intake stroke.
• Full power mode is used for rapid acceleration and heavy loads (as when climbing a hill). The air-fuel mixture is homogenous and the ratio is slightly richer than stoichiometric, which helps prevent knock (pinging). The fuel is injected during the intake stroke."


So, GDI can inject the fuel anywhere from early in the intake stroke to late in the compression stroke. GDI can also vary the air-fuel ratio from 14.7:1 all the way up to 65:1.

On the subject of pinging, to the best of my knowledge a gasoline engine cannot compress the fuel enough to cause pre-detonation. It doesn't happen like in a diesel engine that uses a 22:1 compression ratio and super fast burning 45 octane fuel.

In a gasoline engine, pinging only occurs AFTER the spark plug ignites the fuel. As the combustion's wave front moves across the cylinder, it causes a huge spike in cylinder pressure. This pressure is enough to raise the temperature of the unburned fuel in the cylinder above it's flash point. That is the pre-detonation related to pinging. It relates to some of the fuel in the cylinder. It creates a secondary explosion inside the cylinder. That secondary explosion then spikes the pressure in the cylinder that much more. There can be so much pressure after that secondary explosion that it literally pushes the valves sideways and they rattle inside the engine. Metal hits metal, and that is what we hear as a ping. This is very bad for the engine.

With regard to the cause of a ping in a gasoline engine, it is all about that wave front. The heat created by a 13:1 compression ratio is not enough to cause 87 octane fuel to self ignite. The activation energy for 87 octane fuel is too great. It is the extra high pressure created by the wave front that causes the pre-detonation.

Lastly, burning embers can sometimes cause pinging too. A burning ember is often a carbon deposit inside the cylinder that glows red-hot. It acts like a spark plug. It can cause the combustion process to start too soon, creating unwanted spikes in cylinder pressure. In old carbureted engines, a glowing ember could also cause after-run.
 

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QUOTE (Blue07 @ Sep 17 2010, 10:04 AM) index.php?act=findpost&pid=356842
On the subject of pinging, to the best of my knowledge a gasoline engine cannot compress the fuel enough to cause pre-detonation. It doesn't happen like in a diesel engine that uses a 22:1 compression ratio and super fast burning 45 octane fuel.

In a gasoline engine, pinging only occurs AFTER the spark plug ignites the fuel. As the combustion's wave front moves across the cylinder, it causes a huge spike in cylinder pressure. This pressure is enough to raise the temperature of the unburned fuel in the cylinder above it's flash point. That is the pre-detonation related to pinging. It relates to some of the fuel in the cylinder. It creates a secondary explosion inside the cylinder. That secondary explosion then spikes the pressure in the cylinder that much more. There can be so much pressure after that secondary explosion that it literally pushes the valves sideways and they rattle inside the engine. Metal hits metal, and that is what we hear as a ping. This is very bad for the engine.

With regard to the cause of a ping in a gasoline engine, it is all about that wave front. The heat created by a 13:1 compression ratio is not enough to cause 87 octane fuel to self ignite. The activation energy for 87 octane fuel is too great. It is the extra high pressure created by the wave front that causes the pre-detonation.

Lastly, burning embers can sometimes cause pinging too. A burning ember is often a carbon deposit inside the cylinder that glows red-hot. It acts like a spark plug. It can cause the combustion process to start too soon, creating unwanted spikes in cylinder pressure. In old carbureted engines, a glowing ember could also cause after-run.
Rob was referring to compression stroke injection that DI engines spend most of their time in. Some DI engines don't even have timing for intake stroke injection due to the angle and shape of the injection nozzle.

Gas engines cannot compress fuel enough to cause pre-detonation alone but other elements in the engine can cause pre-ignition. Pre-ignition is different beast from knocking. Pre-ignition is usually caused by out of spec plugs or carbon deposit that get too hot. During the compression stroke, the heat from these elements ignite the fuel prior to the spark plug lighting. I don't like low restriction air filters for this very reason, it messes up the MAF and promotes improper air-fuel mixture leading to carbon buildup in the engine.
 

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Only downside of DI is engines must have an ultra efficient PCV valve (the one that recirculates oily fumes inside the engine back to the intake) to eliminate carbon build-up. Yes, that's the problem many new cars with DI have reported, and has nothing to do with the technology itself. Since the air doesn't have any fuel on it, it also doesn't have the ability to 'wash down' any oily residues deposited around the valves, hence the carbon build-up. Hope Hyundai's system is good enough to avoid that. Many people who own Porsches and other DI engines prone to that are installing 'catch cans' to prevent that. GM engines are notorious to have the crappiest PCV valves. I installed such can on my last Vette, and always had a substantial amount of oil at only 1K miles. When those cars go DI on the next generation LS engines, they better correct that. Good day gang.
 

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Yea the point I was making is that non-GDI motors are limited in their compression ratio. Nobody is going to design one that exceeds those limits for obvious reasons. Carbon build up, aside from causing hot spots, also effectively raises the compression ratio (by taking up space) and can in fact raise the ratio past the static limits, leading to pre-ignition knock. The Theta II does exceed those traditional static limits (11.3:1 is **** high for a street motor that can take 87 octane gas), but not really simply because it is not a "traditional" engine...

The fuel/ignition dance is highly complex. Among the variables are the speed of the engine, the valve overlap, the valve sizes and angles, port size and shape, ram effect and runner length upstream of the valves, backpressure out the exhaust, combustion chamber shape (which itself is a horrorshow to go with port shaping), spark plug design and placement, ambient temperature, quality of the fuel, static compression ratio, shape of the piston crown, the precision of the piston-to-head interface at the top of the stroke (at redline), the timing of the spark itself, etc, etc, etc...

I dont really buy the "wash down" idea. Carbon buildup is caused by failing to fully warm up the car and/or taking lots of short trips. A complete warmup cycle takes a minimum of 20 minutes, so if your commute to work is only 10 minutes, you should expect to have problems. Taking the "scenic route" or a long weekend drive should help to blow out the buildup. During the warm-up fuel does not atomize completely and therefore the engine must be made to run rich. This excess fuel doesnt burn completely, and causes the carbonizing. When the engine is allowed to warm up and lean itself out, the carbon gets burned off and blown out. I suppose this is another way in which GDI technology is a win because the fuel is shot right into the combustion chamber right at the moment of truth so to speak and thus isolated from the rest of the engine which may in fact be ice cold. The traditional design relies partially on the fact that the back of the intake valve will be very very hot, thus when the fuel hits it, it vaporizes which aids the atomization process. Shooting fuel at the back of a cold valve will just cause it to condense on it and not burn very well, which is why you have to shoot a ton more at it during warm-up. Directly-injecting the fuel avoids this problem, and the extremely high pressures involved provide very adequate atomizing...
 
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