axhoaxho

Greetings,

Sorry if I am not up-to-date about the 2012 C-Class sedan. My wife is going to replacing her W204 C350 in a few months, and we are thinking of the new 2012 C-Class.

I read from the recent Autoweek (1-10-2011 issue) that there will be a 302hp 3.5L DFI engine in the lineup. There will also be a 1.8L biturbo I4 engine and another 3.5L V6 with 228hp, but the magazine didn't say if they are DFI as well.

Does anyone know if all these engines will be using DFI or traditional EFI?

Thanks for any insights,

With best regards,

(Edit: Thanks folks for the inputs. I think Autoweek had an error on its article about the 3.5L V6 228hp engine, it should be '3.0L' instead as you folks mentioned. Thanks.)

Carsy

For My Information !

http://webcache.googleusercontent.co...&ct=clnk&gl=au

mr inkredibul

228hp engine is the c300 engine...that will not be dfi

zankok

i dont get what the difference between DFI and the modern day EFI as oppose to carbies
edit* after bit of research i now know
its where the fuel air mixture took place in combustion chamber and allow super lean a/f ratio and therefore better eco and higher hp

jctevere

To my knowledge nothing has been "confirmed" yet as far as if Mercedes will use the new engines, and not much foretold about the engine specs. My guess, the c63 will use the new 5.5L engine, and the c300 will use the same engine, but the new 4 cyl will use a great engine that will offer nearly the same speed with much better fuel sipping efficiency. I think the c300 will be upgraded in the 2013 or possibly even the 2014 model year but I am pretty sure the c350 will get a new engine in this 2012 revision.

nyca

In a DFI, there is no fuel in the intake rail - just air. Fuel is directly injected into the cylinder.

These DFI engines are not without problems (read: Audi). Because there is no fuel in the intake rail, the carbon deposits that come off the PCV system can deposit in the intake rail as there is no fuel to cleanse them like an EFI engine has. Either the engine has to have a very good PCV oil separation unit, or in some cases the car must carry a cleaner solution to inject into the intake rail. The other alternative of course, is that the intake fouls, especially if you make alot of short trips, and you take it to the dealer every 30K miles to have a special cleaner run through it (read: Audi).

Does anyone know what kind of system Mercedes is using for their DFI engines?

zankok

thank you for the fruitful input
are those CGI anything close to DFI?

axhoaxho

Thanks folks for the feedback. I guess I would have to wait a little more to hearing from Mercedes about the exact 2012 C-Class specifications.

With best regards,

930Pilot

The DFI problems listed in the earlier post is all but gone in the newer technology engines. DFI is far superior to traditional EFI in that it injects fuel directly into the combustion chamber at very high pressure and is typically directed to the center of the chamber (or center of the piston). Ideally, the spark plug will be very nearby (also center of the combustion chamber) for a very clean and complete burn. This means that fuel will not be hanging on to the sides of the intake manifold (better economy and efficiency) and will be atomized much better (more power per unit of fuel and again, better economy). DFI also allows you to introduce fuel into the chamber at a very specific point in the combustion cycle - say, 120 degrees before TDC. EFI allows this, but its not as precise because of air flow, turbulence and the volume of air going through manifold (too many variables to be precise - I typically set the injectors to fire 360 - 420 degrees before top dead center on EFI). Also, because of DFI, you can bump the compression for better power too. Overall, DFI is superior to traditional EFI. If you need further proof, look at diesel power technology over the past 10 years - all DFI with huge gains in torque, HP, drivability and economy.

jctevere

Now don't quote me on this, but I am 90% sure that GDI and DFI are the same thing with different lingo involved. I found a pretty good writeup about the differences here:
http://www.carblogindia.com/what-is-gdi/

I never heard of CGI? Besides the mockup computer graphics.

930Pilot

GDI and DFI are virtually the same (same principle). When tuning fuel injected cars, I like using ECU's that have high throughput computers (150mhz for example) because of the number of sensors feeding engine data, the sensor's sensitivity and the depth of the tables (440 cells). Couple that with the engine RPM's, you need a computer that can take data from the sensors, look at the applicable tables, compute the values, then issue the signals to the spark and injectors, all while the engine is accelerating past 5000 rpm.

As our cars get more sophisticated electronically (and more efficient, powerful and fun to drive), it becomes more important to manage the life-blood - electricity. Batteries that are old or batteries that are poorly made will make big differences in the way a car runs. For example, fuel injectors that are built and set up to run on 12.5 volts will deliver the exact amount of fuel for the application. Let's say 11.3 milliseconds of fuel. If the electric power to the injector is 11.8 volts or 13.8 volts, the volume through the injector will be different. Poor performance. So, the alternator and battery become more important as the technology improves.

I know, I rambled - sorry.

nyca

Yes, DFI is a better technology then EFI.

But just google "audi dfi engine carbon buildup" and you will see what comes up, its not anecdotal. BMWs have issues too, notably gas that appears in the crankcase because the fuel pressure in the cylinder is so high.

I want to see what MB does on their DFI engine applications regarding technology to address these issues. A better oil separation unit for crankcase vapors is key.

noka

I could be wrong but I believe not only Audi but BMW is still having problems (intake valve issues and early high-pressure fuel pump failures). I do not believe these problems have all been solved yet.

nyca

The BMW fuel pumps was a part defect, a Nightline expose forced their hand on a recall. The other area BMW ran into trouble with was their very long oil change intervals, since they give free maintenance, combined with the fouling issue and the "gas in the crankcase issue" - is a mess for them. I would never buy a preowned BMW DFI car that only had oil changes on their free schedule timeline (at least twice the recommended interval is needed).

noka

Thanks, I haven't been keeping up on the BMW HPFP high failure rate issue since I sold my last bimmer. I Googled and found the BMW press release and related video. The carbon buildup problem may still be an issue that MB needs to handle.

930Pilot

The problem is far from being an epidemic. For example, Porsche has DFI and so far does not suffer the same problems. Before you state that Porsche's motor is a boxer motor, the principles are the same and they have to deal with burning crankcase oil for emissions and high intake valve temps too.

Other companies are looking at these options:

1. higher combustion chamber temps to burn the coking from the intake valves
2. using sodium filled intake valves that run cooler and will not get coked
3. advancing the ignition to create higher combustion temps and pressures to burn the coke material
4. introduction of another injector in the intake manifold to spray water or methanol or mixture
5. shielding material for the intake valve
6. and so on.

As for gas in the oil (crankcase oil), OMG, change the oil sooner than 10,000 miles. The best way to combat this and get a definitive answer is to do an oil analysis when you change the oil. The analysis can tell you how much gas is in the oil. You "should" be able to get 7500 miles out of an oil change. However, I still change mine in the C300 at 5000 - regardless of what MB or anyone else tells me. My oil has next to no gas in it within 5000 miles. If I start to get elevated levels, then its time to sell the car as the piston rings are toast.

However, I completely agree that I want to see what MB does to combat it, even though we are only talking about coking of oil on the intake valves on very few cars.

Good discussion.

Carsy

Interesting & informative.

NickCats

Another thread full of great information - thanks !

For those of you that were cross shopping with the BMW 335i, we made the right choice :

http://abcnews.go.com/TheLaw/bmw-adm...ry?id=11968495

Nick

kevink2

The Mazdaspeed 6 Turbo also has problems with DFI. Basically what nyca said. PVC and closed crankcase, and EGR combine to foul the manifold ports, and really coke out the cylinder ports and valve backsides. I can grab some ugly pics.

Unless fixed ( I like the 4th concept listed by 930pilot ((I was just a 931 pilot)) ), a DFI gas engined car would be a good lease.
.

930Pilot

The BMW story sucks. Some diesel pick ups had this problem early in their development in the past 15 years. If you run a fuel injector without diesel fuel, you'll permanently damage the injector. They'll get it right as the technology is available and reliable. And, the 335 is a great car.

I did some more digging on the intake valve fouling and what is being done to help. It seems that most valve fouling problems happen at more than 25,000 miles (time to build up). A local shop in ATL taps a small nipple just after the butterfly where they introduce a can of BG or Seafoam while the engine is running between 2 - 4000 rpm. It cleans the valves quickly and safely. It's not ideal but if you have to do it every 20,000 miles, that's not catastrophic and probably good for the valve seats anyway. The older the engine gets, the more it fouls. Again, its not ideal, but your engine is not toast either. Emissions laws state this is the way crankcase venting will be handled, so there is no more venting to a charcoal canister (something I would personally install if I had a problem DFI car).

No flames please....

nyca

I had read a detailed technical article (which I cannot find now) on the new 4.7L MB biturbo V8 going into the CL and the next S class - I don't recall it mentioning how MB was going to address this problem. Getting that DFI fuel rail cleaning work done is going to get old fast, especially at dealer prices.

220S

Sorry to bring up an old thread, but I've been curious about latest DFI technology in gasoline motors.

As a Porsche owner and PCA member, some bad news is that the newer DFI 997.2 models are experiencing HPFP failures now like BMW. Same slow start symptoms and dealers are replacing them. And some owners have had multiple replacements already.

It's still early to know if they designed effective enough oil separators for other issues to appear (and most P-car owners don't rack on a lot of miles.) But the flat engines have always been prone to intake oil contamination. The dealers still sell and recommend using BG44K. We'll have to see, as time will tell. But hopefully Porsche got it right; DFI does have a lot of positive features. And of course as DFI is more universally applied, the technology to avoid potential issues will improve.

whiteongrey

Probably why MB waited so long to introduce direct injection. There are a whole slew of DI 4 cyl coming out from various mfgs now. The power and economy gains are very impressive.

I would guess any issues the early adopters like Audi and BMW had are fixed. Besides, if under warranty does not matter.

noka

I haven't checked the BMW boards that I am a member of, but I wouldn't be so sure the problems are solved. Also, warranty is OK if you don't keep a car beyond that, or otherwise have no extension, and trade instead of selling privately.