MercPlease

I didn't say diesels DID hog gas, I was saying.. AMG CDI would get less mpg than just a CDI essentially.

240D 3.0T

Why would it? It gets less MPG than a C270CDI and better MPG than a C320CDI.

DslBnz

I'm just still trying to understand how the latest CDI's with only 208 hp which weigh 500 lbs more than the C30 CDI accelerate to 60 mph in the same amount of time as the AMG with 20 + less hp, and 500 lbs more mass. That just doesn't compute in the slightest.

THE 197 hp W210 E320 CDI was rated by Mercedes for 0-100 km/h in 8.3 seconds, for example. But the W211 with 204 hp does 0-60 mph in 6.6 seconds with the same transmission and another 100 lbs or so of weight.

I mean, MB claims the diesel essentially clocks even with the E350, an engine with 268 hp and a 7-speed. THAT'S A 60 HP DIFFERENCE! Not to mention that the diesel is heavier by 100 lbs, or so.

Anybody that understands the relation between horsepower and torque is baffled. Either the CDI's are significantly lighter than specified, or Mercedes is underrating their diesel engines by 30% +. 200 hp cannot keep pace with 260 hp, no way in Hell.

prometheus

Torque is your friend.

240D 3.0T

HP is a function of torque over time. The only reasons the CDI's can't develop high HP numbers is because the torque occurs so soon and they can't revv as high as the gassers because diesel expands/burns slower.

Gassers don't produce torque until up high because gas burns so quickly. The number of explosions per second has to be high in the RPM range that it favors HP numbers (torque over time). Thats why gassers have HP and torque numbers almost equal or less torque than HP. Think about an F1 engine. It can revv to 21,000rpm and have 900hp but it only has about 400ft'lbs of torque.

That's why the 320CDI can keep up with the 350. It's got so much torque down low in the RPMs that it will launch off the line much faster but the 350 will start to catch up once its revvs climb high enough.

MercPlease

What is your point exactly? Im confused..

240D 3.0T

Bigger diesel engines use more fuel. Economy is directly related to engine size, design and the application of your right foot.

Since their technology is the same, size and right foot are what makes MPG.

DslBnz

So does an E350. 258 lb/ft of torque is available at only 2K rpm. Using the gearing of an E320 CDI, that would equate to 292 lb/ft at 2K(2.65 vs 3.07 final drive). Plus, that 258 lb/ft occurs as high as 5K rpm. The CDI can only maintain its peak torque to a maximum of 2800 rpm. That's barely more than half the E350's max torque peak rpm. Since an E320 Bluetec's horsepower peak is considerably lower, that torque drops by 26% to 287.4 lb / ft by 3800 rpm. Remember, an E350 would be pushing, with equivalent gearing, 292 lb/ft of thrust.

At this point is where the E350 will feel more powerful, and it will exponentially become so as the E320 CDI drops to the next gear at a considerably earlier engine speed than the E350.
The shift point in an E350 occurs 16% later using the 292 lb/ft figure, but during that 16% the E350 will gain considerable ground. By this time the Bluetec is climbing from its next gear which provides considerably less torque output, by ~ 30%. So 201 lb/ft is felt maximum (the 7GTronic 2nd gear puts the engine back at the hp peak), while the E350 is pulling 292 lb/ft for 16% longer than the E320 Bluetec's first gear.

But, launch is everything I suppose. In second gear, an E350 shifts into 3rd at ~ 60 mph while the CDI hits 50 mph. This pattern is how the Bluetec would lose ground to the E350. Of course from seat of the pants, the Bluetec would feel considerably quicker (by about 25%) than the E350. Its a much more responsive engine thanks to its power curve. But its no screamer.

DslBnz

FWIW, there should be ~ 0.5 second difference between the two to 60 mph. Unless the Bluetec really does have 221 hp, like the non-Bluetec V6.

DslBnz

So does an E350. 258 lb/ft of torque is available at only 2K rpm. Using the gearing of an E320 CDI, that would equate to 292 lb/ft at 2K(2.65 vs 3.07 final drive). Plus, that 258 lb/ft occurs as high as 5K rpm. The CDI can only maintain its peak torque to a maximum of 2800 rpm. That's barely more than half the E350's max torque peak rpm. Since an E320 Bluetec's horsepower peak is considerably lower, that torque drops by 26% to 287.4 lb / ft by 3800 rpm. Remember, an E350 would be pushing, with equivalent gearing, 292 lb/ft of thrust.

At this point is where the E350 will feel more powerful, and it will exponentially become so as the E320 CDI drops to the next gear at a considerably earlier engine speed than the E350.
The shift point in an E350 occurs 16% later using the 292 lb/ft figure, but during that 16% the E350 will gain considerable ground. By this time the Bluetec is climbing from its next gear which provides considerably less torque output, by ~ 30%. So 201 lb/ft is felt maximum (the 7GTronic 2nd gear puts the engine back at the hp peak), while the E350 is pulling 292 lb/ft for 16% longer than the E320 Bluetec's first gear.

harkgar

Dear All,

All this talk about torque and horsepower without reference to the 5 speed E320 CDi transmission is pointless. The transmission has to be able to take the torque.

There are 2 types of 5 speed transmissions for the W211. One is the common gardener type fitted to the lowly E320 V6, which is now only used in the Chryler 300C and Dodge Charger.

The other is the heavy duty 5 speed used intially in the V12 engines, later in the E55 and other AMG products. In fact it still resides in the latest SL55. This transmission is capable of taking a lot of punishment.

Does anyone know which 5 speed is fitted to the 2005-2006 E320 CDIs? Any Mercedes Benz technicians on this board?