Whats more reliable? V6 or IL6 E320cdi

[bullyboy112]

Just wondering, what's more reliable?

E320 CdI in-line 6, or the E320 CdI V6???





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[grober]

Inherently the straight 6 is better balanced. However the V6 has become more popular possibly due its better "packaging capability" to fit under/into the bonnet of today's impact resisting engine compartments/crumple zones? The OM642 is a 72 degree V which is inherently unbalanced without a balancer shaft and requires 48 degree offset crank pins to achieve 120 firing intervals so mechanically more complex. All that pales into significance however compared to all the emission gubbins hung on the basic engine inlets and exhausts. These are almost certainly going to be the source of any reliability problems rather than the engine itself .

 

[Martin 1]

V engines have always sounded better, mostly due to them being inherently unbalanced (like me) didn't do the Buick / Rover V8 any harm, or the Essex / Cologne V6.

 

[MancMike]

The inline 6 is undoubtedly a cleaner design, but the V6 is a V... As soon as you go to a V, the sound gets a huge boost.

As for reliability, I don't know, but I've been hammering mine for 40,000 miles and it's still going strong.

 

[Alex225]

I’m aware of many inline diesels soldiering on for hundreds of thousands of miles. That said a chap popped up on a Merc group I’m on with a CLS350 with the V6 diesel and it had 300k!!

I’m hoping they both are as I have an E320 and the other half has a CLS350! Haha

 

[estate-agent]

I have a V6 CDI Merc and to be fair has so far been no trouble at all. As mentioned above, the engine's ancillaries are more likely to give you problems rather than the engine itself. Sooting up of inlet components is inherent on a higher mileage engine these days but nothing that can't be repaired /solved.

I can't vouch for the straight 6 motor but I did have a straight 5 270 CDI and I have to say it was a great engine, noisier that the V6 once up in the higher rev range but strong as an ox for sure. Engine sound is a personal taste, 5 pot engines remind me of 80's Audi Quartros, Straight 6's remind me of late 80's BMW 325i's. I'm sure the V6 CDI would sound great with a set of pipes, mine has a stock exhaust system and it still sounds good when I fire it up in the mornings

I think a good amount of service history and sensible mileage will likely lead you to a good reliable motor.


.

 

[grober]

MERCEDES new family of modular engines includes straight sixes. I believe they all share the same basic bore stroke dimensions differing only in the number of cylinders=3,4,6 and state of forced induction. Needless to say the engine builder would benefit from economies of scale in manufacture. V formation engines to be found perhaps only in Mercedes more powerful AMG models
2017 Mercedes-Benz S-Class to front new engine line-up | Autocar

The new generation of engines from Mercedes-Benz: The highlights | marsMediaSite

New six-cylinder petrol engine (M 256): Fascinating 48 V drive | marsMediaSite

New six-cylinder diesel engine (OM 656): Majestic long-distance athlete | marsMediaSite

 

[merc85]

I6 all day long, although not as refined as the v6 or as powerful, I’d still stick with the I6 better mpg too.

 

[grober]

New Merc inline six basics---- skip the first 50 second filler

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and more in depth article
Why Mercedes’ new inline six matters, even if no one is sure when we’ll see it

in deference to the diesel enthusiasts here's the new OM656 straight 6 diesel but despite more conventional technology surely even diesel enthusiasts will be scared by the Medusa-like plethora of pipework and electrical connections? skip to 1min 20seconds in

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[Londonscottish]

The bore and stroke are interesting. My V8 is underquare (98mm bore and 90mm stroke) whereas the I6 goes totally the other way (bore 83mm and stroke 93mm).

I wonder why?

Where's Machtech?

 

[Larkone]

Reliability is also determined by how it has been driven and serviced.

 

[GordonTarling]

All that technology, yet they can't even get the steering wheel on the right side!

 

[MancMike]

The bore and stroke are interesting. My V8 is underquare (98mm bore and 90mm stroke) whereas the I6 goes totally the other way (bore 83mm and stroke 93mm).

I wonder why?

Where's Machtech?

Your petrol needs a bigger bore to get good torque from the stroke as it's much lower compression than a diesel. The higher compression of a diesel means it can have massive torque from a smaller bore, and the longer stroke all lends itself to efficiency.

 

[grober]

The bore and stroke are interesting. My V8 is "oversquare" (98mm bore and 90mm stroke) whereas the I6 goes totally the other way (bore 83mm and stroke 93mm).

I wonder why?

Where's Machtech?

I can only speculate. Quite a few straight sixes in the past were slightly undersquare so its not unusual for this configuration of cylinders*. It may be to do with "packaging" again narrower cylinders shorter /narrower block, or better low down torque characteristics at low revs may suit the electric starter /generator transmission package or it may be the emissions can be controlled better don't know.
the basics discussed here
Longstroke vs. shortstroke - CARmag.co.za
and another video

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* the Jaguar XK 3.4 LITRE engine that powered the D type Jaguar was originally 83mm bore x 106mm stroke and the more recent straight six that powered the S80 VOLVO the B6294S is 2,922 cc straight-six. Bore is 83 mm and stroke is 90 mm

 

[Londonscottish]

Your petrol needs a bigger bore to get good torque from the stroke as it's much lower compression than a diesel. The higher compression of a diesel means it can have massive torque from a smaller bore, and the longer stroke all lends itself to efficiency.

Yeah but I thought I was reading about the new I6 petrol.

 

[190]

The return to under square engines must have something to do with the adoption of forced induction. One limiting factor with under square engines was the linear piston speed and hence maximum revs. Now that almost all engines are forced induction, high revs are no longer needed as maximum power revs are relatively low. The advantage of under square engines was always said to be at lower revs due to the longer duration of cylinder pressure on each power stroke.

Packaging may also be an issue with smaller bores allowing for a more compact if taller engine.

 

[Auto-mobile]

Straight 6 (211/later w220) is the better of the two as is the 5 speed gearbox attached to it, sbc would let it down though in the 211.

V6 (642) has a few common issues that are not cheap to fix and comes with the 7g tronic gearbox.

 

[Londonscottish]

The return to under square engines must have something to do with the adoption of forced induction. One limiting factor with under square engines was the linear piston speed and hence maximum revs. Now that almost all engines are forced induction, high revs are no longer needed as maximum power revs are relatively low. The advantage of under square engines was always said to be at lower revs due to the longer duration of cylinder pressure on each power stroke.

Yeah this makes sense - I was wondering if the turbo(s) had a bearing in it.

I wonder, though, if the new I6 will rev like my 5.5. Mine really does like to rip up to the red line. Or maybe that's academic as you have an Ayers Rock torque curve in the I6 and a very wide power band anyway (and therefore less need for revs and hence increased efficiency.....)

 

[grober]

A new petrol M256 i6 and old M276 v6 comparison ----interesting that despite a longer stroke the i6 has shorter conrods ----extra [stroke] travel being longer crank throws presumably ?

 

[KeithJG]

One thing not mentioned in the Carmag link is the fact that oversquare or shorter stroke engines are more suitable for smaller capacity motors hence the change possibly as most manufacturers are going down on cubic capacity and they have to get the extra power from somewhere which is turbo and a shorter stroke.
As the reciprocating mass has less distance to travel therefore it revs higher and is quicker getting there so good acceleration.
Me being old school one good example of the beginning of the shorter stroke was the 1959 Ford Anglia with a 997cc engine as all the BMC motors were a lazier long stroke engine.
The shorter stroke engine is quieter than the longer stroke models as a wear factor (more strokes per mile) the longer stroke being more reliable with more low down torque hence lesser maintenance (less strokes per mile).
The physical size of the engine plays an important place in the design of the car and so some long stroke engines lay at an angle to suit a better lower bonnet line.
IMO going to shorter strokes merely means using less metal smaller engine sizes eg. Noisy 4 cylinder and more profit for the maker.
As regards i6 or v6 .......i prefer the more modern v6 it has more advantages overall than the i6.