LexFather

http://www.autocar.co.uk/News/NewsAr...llCars/241722/

Mercedes-Benz and BMW are both working on three-cylinder petrol engines that will be launched within five years.

All Mercedes up to and including the C-class will be available with a three-cylinder turbocharged unit, while BMW is developing cars to suit the quirky noise, vibration and harshness characteristics of three-pot engines.

“A three-cylinder engine in the C-class is quite conceivable,” said Daimler’s board member in charge of R&D, Dr Thomas Weber.

Daimler strategist Johannes Reisenrath went further. “Logically, if we go from eight to six cylinders with the same output to help economy, and we go from six to four cylinders, then four has to go somewhere too,” he said.

“Now we can do a 1.2-litre three-cylinder, so we can have 168bhp with a turbo, plus 150-185lb ft, which is enough to drive a mid-sized car like the C-class very well. It also has a six per cent fuel consumption benefit, and with 95g/km of CO2 fleet fuel consumption as a target, that’s an option we have to consider.

“We will have one on sale in the next four to five years.”

Mercedes is working on making the three-cylinder cars as fast as the four-cylinder counterparts, too. Its research shows that customers want economical vehicles such as the three-cylinder model to be as quick as their current cars.

“From driving some of the earlier three-cylinder cars, they have a nice torque punch. We are much more advanced in turbocharging and gearboxes, so they will be even better next time,” said Reisenrath.

BMW sources have told Autocar that the next 1-series has been engineered to cope with the unique noise and vibration of a three-cylinder engine. BMW has had experience with three-cylinder units in its motorcycles, where reducing NVH is crucial.

mmarshall

Three-cylinder engines are not that unusual in the American market. Chevy/Geo used them a number of years ago in the Metro/Sprint, a small, high-mileage buzz-box of Suzuki design. Subaru used them, along with an early CVT, in its FWD Justy model (before they dropped FWD models cars from the U.S. market). And, today, Mercedes itself uses one in the Smart-for-Two, a tiny vehicle of Mercedes design.

mmarshall

Gee, Mike.........maybe Acura will put a three cylinder in the new TL. Then you'll have a REAL reason to b***h about it.

(Just Kidding)

IS-SV

The time horizon noted is long. 3 bangers in time will gradually move up the ladder a bit with improvements in refinement.

mmarshall

The traditional problem with 3-cylinder powerplants, even more so than power, has been engine smoothness. In general, the fewer the cylinders, the rougher-firing the engine is, and the more you tend to feel the power-pulses and vibrations. That is complicated by the fact that, in traditional four-cycle engines (which, except for Mazda rotary powerplants and hybrid electric motors, describe almost all the automotive engines in use today), an odd number of cylinders (usually 3 or 5, as in the older 5-cylinder Volvos and Audis) also makes it harder for engineers to sync the cylinder motion with the four-cycle firing order. A heavy flywheel sometimes helps by damping out some of the crankshaft vibrations. So does modern computer-timing of the exact firing sequence and valve actuation.

IS-SV

Yes agreed and most of us know (above) in these general non-tech terms. Maybe we can get some of the members with mechanical engineering backgrounds to chime in, with specifics about different configurations, crankshaft offsets, balance shaft suitability, etc.

LexFather

lol. honestly after the last annoucment I could care less. If you haven't noticed I haven't posted Acura news the past few months b/c its just lame. I will comment if someone posts though.

As for a 3 cylinder, well I hope the car doesn't weigh much.

I8ABMR

I want to see the B class benz sold in the US. Thats a small car that is a looker and has cool features and is powerful enough to keep most city drivers content.

mmarshall

Believe it or not, the most likely B-Class to come here might (?) be the hydrogen fuel-cell version, if Mercedes can get its costs under control and we get a decent network of compressed-hydrogen filling stations here (those stations will also be needed, of course, for the fuel-cell Honda FCX). Mercedes had some literature on the fuel-cell B-Class at the D.C. Auto Show in February (they've done extensive developmental work in Europe), but no actual B-Class on display. However, the word from the Mercedes people was that the A-Class was out; it is not coming here. That leaves only the B-Class as a possibility.

bitkahuna

iTrader: (20)

i'm no mechanical engineer, but just had a thought.

on a 4 cyl engine, as i understand it, generally 2 cylinders fire (say 1 and 3) and then as they're exhausting and getting the next air/fuel mix the other 2 cylinders fire (2 and 4). this alternating pairs keeps things 'even' in firing pattern, and in theory the least noise.

but i was wondering, what if they fired sequentially? offset 1/4 turn apart on the crankshaft, if the engine fired 1-2-3-4-1-2-3-4, or any order for that matter...

i bring this up because on a 3 cylinder, i imagined the nvh problems might be from firing 2 cylinders then 1 then 2, etc., whereas if they were fired seqentially in 120 degree offsets, maybe it would be smoother?

i freely admit i don't know what i'm talking about here... someone help?

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iTrader: (1)

I am a Mech engineer major however this is just my hypotheses. I believe firing sequential would make the engine run like a bucking bronco.

When it come to 3 cylinder engines, why don't they just develop less temper mental rotaries?

IS-SV

Yes, we will see what the ME types with automotive backgrounds have to say.

On the rotary topic, poor emissions, poor fuel economy, short-lived seals and low torque all contribute to making rotaries not very viable.

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iTrader: (1)

True, however I believe most of those problems could be fixed if somebody other than Mazda tried.

IS-SV

Maybe NASA could do it if cost was no object.

mmarshall

On a rotary, you also have the problem of high oil consumption. That's partly because of the generally weak rotor-apex seals, but also because, in a rotary engine, there's no way to isolate the lubricating oil film on the seal tips from the combustion process in the firing chambers. The traveling motion of the seal tips themselves open and close the chambers as the rotor(s) spin around the central shaft. The amount of oil used (after break-in), of course, usually increases as the engine ages.