Some of the newest DI engines use a hybrid DI and port injection design to clean the intake valves.
Also some engines like the Mercedes M276 doesn't seem to suffer from DI intake valve deposits. I haven't seen a single thread about it even though it is DFI. A 3.5L V6 making 306hp.
Some interesting info:
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Okay here we go...... !!!!!!!!!!!!
I did a little poking around and found this... and it looks good... maybe! The new DI engines are designated M276 and M278, (V6 - V8). Both utilize the same head design although the V8 is turbocharged. But for our discussion, we are more interested in the set up of the injectors, which are piezo-electric direct petrol injection and the location of the intake valves relative to the injector. The new engine has a reduced V-angle between the cylinder banks, 60 now vs. 90, making the engine naturally balanced, enabling the designers to eliminate the friction hogging balancer shaft. The fuel efficiency numbers are truly astonishing for this engine, more than 24% more economical than the previous engine!
Let's look at the pix...
M276 V6
^ See where they placed the direct injected fuel injector?.... TDC! Now look at this picture...
M278 V8 but same head design.
^ You can better see in this picture that because of where the piezo electric injector is located, (not to the side but above the intake valves) Kevibk2 may have hit the nail on the head! The intake valves (the larger ones) are perfectly located to take full advantage of the injectors spray pattern cleansing properties.
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The following is taken from Autoholics:
"In contrast to the V8, the new V6 engine is naturally aspirated, and has the potential for future use of a turbocharger thanks to the modular design concept.
A completely new intake and exhaust gas system with a variable-resonance intake manifold and optimised airflows was also developed for the new V6. This enabled the output of the 3499 cc engine to be increased to 225 kW (306 hp) (Previous engine of the same displacement in the S-Class: 200 kW/272 hp). Torque has increased from 350 Nm to 370 Nm, and is available between 3500 and 5250 rpm.
Key figures for the new V6 engine
No. of cylinders
V6
Displacement (cc)
3499
Bore (mm)
92.9
Stroke (mm)
86
Compression ratio:
12.2:1
Output (kW at rpm)
225 at 6500
Torque (Nm at rpm)
370 from 3500-5250
Both the new V6 and the new V8 from Mercedes-Benz have aluminium crankcases, pistons and cylinder heads. The crankshaft, connecting rods and valves are of special forged steel.
Mercedes-Benz has achieved this considerable leap in efficiency with the use of innovative technology - including newly developed, third-generation direct petrol injection with spray-guided combustion, multiple injection and multi-spark ignition. With this new generation of V-engines, Mercedes-Benz is clearly demonstrating that with concerted further development, internal combustion engines still have a great deal of potential, and that V6 and V8 engines with their great running refinement are fit for the future.
The technology package in the new engine generation includes a number of new developments that are unique in this combination:
• In combination with multi-spark ignition, a further developed, third generation direct fuel injection system with spray-guided combustion and piezo-electric injectors offers further possibilities for fuel savings - in the V8 by means of an improved, homogeneous combustion process, and in the V6 by a new, stratified combustion process with a considerably extended characteristic map and fuel-efficient lean-burn technology.
• In conjunction with start/stop technology, shift point adjustment and specific friction-reducing measures, improvements in day-to-day fuel consumption by more than 20 percent are possible.
• Power consumption by ancillary units has been reduced. These include an optimised water pump with second generation thermal management, a demand-controlled oil pump, a volume-controlled high-pressure fuel pump and an intelligent generator management system.
Lightweight construction techniques and detailed improvements have also reduced in-engine friction considerably compared to the previous engine.
Third generation direct petrol injection
Direct petrol injection with spray-guided combustion, which Mercedes-Benz was the first car manufacturer to introduce in series production, has been developed further as a third generation. The system pressure is up to 200 bar, the pressure being variably optimised according to the engine's characteristic map. Completely newly developed piezo-electric injectors allow up to five injections per intake stroke for the best possible mixture formation.
The crystalline structure of the piezo-ceramic changes in microseconds under an electric voltage, and with a precision of just a few thousandths of a millimetre. The central component of a piezo-electric injector is the piezo-stack, which directly controls the metering needle. With a response time of just 0.1 milli-seconds, the fuel injection can be very sensitively and precisely adjusted to the current load and engine speed, with a beneficial effect on emissions, fuel consumption and combustion noise.
The multiple injections even in tiny quantities made possible with piezo-electric injection technology were used by Mercedes-Benz engineers to control a wider characteristic map with the efficient lean-burn process, and to provide the conditions for further functions:
• As the first new operating mode, Mercedes-Benz engineers have developed "Homogeneous stratified combustion" (HOS). As the name implies, HOS is a combination of homogeneous lean-burn and classic stratified combustion. The first injection is sprayed into the intake stroke, forming a homogeneous basic mixture. Actual "stratified" injection takes place during the compression stroke before ignition, and is a single or double injection depending on the characteristic map.
(Please Note: This may be the answer I've been looking for! HOS can be programmed to spray multiple times during the power stroke, and at any rpm! (Amazing but so does my GT-R) This means that Mercedes engineers quite possibly took advantage of this technology to spray off the intake valves during those milliseconds! See next point below.)
• Another new operating mode is known as "Homogeneous Split" (HSP). In this homogeneous combustion process, more than 95 percent of the fuel is singly or multiply injected, followed a very small "ignition" injection to stabilise combustion. This is used when combustion conditions are difficult.
The characteristic map of the new Mercedes-Benz V6 engine is therefore basically divided into up to four areas:
− idling range (homogeneous)
− low partial load up to 4 bar and 3800 rpm (stratified)
− medium partial load 4 to 8 bar and up to 4000 rpm (HOS)
− high load and entire engine speed range (homogeneous or HSP)
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Well there you have it! This is the best possible proof I can find to date that the boys over in the new sub-plant of the Untertürkheim engine werks, lies the new V-engine factory at Bad Cannstatt, knew what they were doing!
M276 V6
^ This picture doesn't help our discussion at all but I thought is was very cool so I included it.
