2.5L engine for 2014 Chevy Impala features new Intake Valve Lift Control (IVLC)
24 May 2013
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| IVLC uses an all-new rocker arm that switches between low- and high-lift intake cam profiles. The mechanism is actuated by an oil control valve through a dual-feed stationary hydraulic lash adjuster. Click to enlarge. |
The new 2014 Chevrolet Impala offers as one of its three engine options a four-cylinder Ecotec 2.5L engine, featuring the debut of a new advanced variable valvetrain technology—Intake Valve Lift Control (IVLC, earlier post)—and improved fuel economy. The EPA estimated fuel economy for the 2014 Impala with the new 2.5L engine is 21 mpg city and 31 mpg highway (11.2 and 7.6 l/100 km, respectively).
The 2.5L engine, which delivers SAE-certified 196 horsepower (146 kW) and 186 lb-ft of torque (252 N·m), achieves variable valve lift using an all-new rocker arm that switches between low and high lift intake cam profiles.
The mechanism is actuated by an oil control valve through a dual-feed stationary hydraulic lash adjuster. It is the first of its kind for low friction roller-type finger-follower valvetrains in gasoline engines, GM says. The engine’s computer continuously selects the optimal lift profile based on conditions such as engine speed and load.
When the technology operates in low-lift mode, the engine pumps only the air it needs to meet the driver’s demand. The system switches to high-lift mode at higher engine speeds or under heavy loads, providing the full output capability of the engine.
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| Low-lift profile. Click to enlarge. | High-lift profile. Click to enlarge. |
Intake Valve Lift Control works so seamlessly drivers aren’t likely to notice it at all. What they will notice is a fuel economy improvement of up to one mile per gallon.
—Mike Anderson, General Motors’ global chief engineer for Ecotec engines
Quiet. The redesigned large sedan’s 2.5L engine with direct injection is engineered to be one of the quietest and most refined in the segment. The development team reduced engine noise intensity by 40% by specifically targeting the 2.5L’s noise frequency signature. They pushed radiated noises into a higher frequency range well above 2,000 hertz, which is more pleasing to the ear—particularly in the high-load operating ranges where engine sound is most intense.
The refinement-enhancing changes and improvements over previous Ecotec engines ranged from the comparatively simple—such as integrating a sound-absorbing cover into the intake manifold and specifying quieter drive chains—to more fundamental architecture items, such as relocating the balance shafts from the cylinder block to a cassette within the oil pan.
Impala’s passengers get a quieter driving experience due in part to active noise-canceling technology and a more refined sound as the engine revs to its 7,000-rpm peak.
Chevrolet expects the 2.5L model to be a popular choice among Impala buyers. The other engine options are a 3.6L V-6 and the Ecotec 2.4L with eAssist. More than two-thirds of Chevrolet cars sold in the first quarter of 2013 had a four-cylinder engine.
Hasn't this been standard on all Hondas (VTEC) for many years?
Posted by: Nick Lyons | 24 May 2013 at 07:31 AM
"Hasn't this been standard on all Hondas (VTEC) for many years?"
No, VTEC is variable valve timing which a number of manufacturers have had for some time. This is variable valve lift which is added to variable valve timing. There are some other variable valve lift techniques such as Fiat's MultiAir and BMW's ValveTronic.
Posted by: sd | 24 May 2013 at 08:44 AM
Wow + a new chrome bar on the trunk lid?
Posted by: HarveyD | 24 May 2013 at 08:49 AM
@sd: From Wikipedia:
VTEC (Variable Valve Timing and Lift Electronic Control) is a valvetrain system developed by Honda to improve the volumetric efficiency of a four-stroke internal combustion engine. The VTEC system uses two camshaft profiles and hydraulically selects between profiles. It was invented by Honda engineer Ikuo Kajitani,[1][2] and was the first system of its kind.
Note "...valve timing and lift.
Honda has been refining this system since the 1980s. Use of dual cam profiles, hydraulic activation, etc. were all developed by Honda years ago.
Posted by: Nick Lyons | 24 May 2013 at 09:50 AM
AS nearly as I can determine, the new Chevy has a two position lift program.
The Honda VTEC is primarily a variable valve timing system with a little bit of valve lift control.
BMW's Valvetronic system is concerned with valve lift and use a different system to control valve timing.
All three use a cam to set the same valve lif tor valve timing for an entire bank of cylinders.
Fiat's MultiAir fully variable valve control allows both completely variable valve lift, and valve timeing for each cylinder, independent of other cylinders in the cam bank. So it is the most flexible. However as currently implemented, it works only on the intake valve side of the cylinder.
For HCCI opersation the Multiair setup would seem to offer the best prospects for use.
Posted by: D | 24 May 2013 at 02:26 PM
1) This system is not at all like Honda's (more like Fiat's); and
2) Honda makes a neat engine, but they were hardly the first. See, Variator, among others.
I suppose you can argue that "lift" as used by that Wiki article to describe Honda's system encompasses all lift, but most folks would not agree that it does.
Posted by: Mprater | 24 May 2013 at 02:44 PM
*does not.
Posted by: Mprater | 24 May 2013 at 02:44 PM
Forget about Honda. Why not compare to state-of-the-art technology instead? This GM system is not even near the continuously variable systems from BMW and Fiat.
Posted by: Peter_XX | 25 May 2013 at 01:10 AM
The GM mechanism is the only variable lift using the roller finger follower valve actuation arrangement. This is the lowest friction valve actuation mechanism, and GM uses it on all of their OHC engines.It has lower friction than Honda's or BMW's and is smaller and cheaper as well.
Posted by: frankbank | 26 May 2013 at 11:20 AM
Perhaps you mean less expensive, in marketing words count :)
Posted by: SJC | 26 May 2013 at 06:07 PM
what is new about this system, is the roller cam follower, as the press release says. As one might expect from GM, it is less expensive and more efficient. Other than that, it uses 2 different cam profiles and it electrohydraulically switches from one to the other. There is also a cam phase advance/retard mechanism that is probably at the end of the cam near the chain drive (not shown above). So, from what I understand, this is rather like the VTEC in that it changes from one cam lobe to another to change lift, duration etc. So, does GM do this for each intake valve? I assume so as I imagine they are all 4 valve cylinders and have the same for both intake valves. Other than the roller cam follower, is this really cheaper than the VTEC, is it more compact? It has 3 cam faces, one low lift, and 2 high lift per valve.
Multiair is a hydraulically controlled intake valve that on an individual or group basis can have it`s lift reduced. That seems more capable than the VTEC or GM for lower speed engines.
Posted by: Sotaro | 26 May 2013 at 09:33 PM
ECOTEC, ECOBOOST is it not great that all cars are marketed for their environmental attributes? Plus they are quite even at 7000 rpm while all are fun to drive.
On the way home from work Friday saw a '64 shiny red Impala. The concept of bench seats and no seat belts was lost on the young couple.
Posted by: Kit P | 27 May 2013 at 08:35 AM
Honda has many kinds of VTEC systems so it is very difficult to generalize.
For instance:
In the Honda SOHC "VTEC-E" implementation, there is virtually only one intake cam-lobe is implemented on the camshaft. Where the same generation SOHC "VTEC" has two cam profiles, VTEC-E has One profile and one essentially flat "ring". In operation this means the relevant rocker arm will not be activated causing the engine to effectively work in 12-valve mode. This promotes a swirl action during the intake cycle. In more demanding and higher rpm conditions the valves get locked together and follow the cam, making the engine work in 16-valve mode.
VTEC-E was the first generation to use roller rocker arms.
Essentially the same engine with normal VTEC uses two different cam profiles for the Intake valves only (three lobes, two outside lobes are low lift, center lobe is high lift). It does this with three rocker arm followers per two intake valves. When valves get locked together they follow the high lift cam in the center.
There is also a 3-stage VTEC application on a SOHC engine utilizing three different lift profiles. Stage 1: essentially 12 valve operation Swirl mode, Stage 2: 16 valve low lift operation, Stage 3: 16 valve high lift operation.
These three applications of VTEC were all used on the same basic engine block called the "D-series".
Since the mid-nineties there have been newer updated blocks and VTEC implementation strategies.
I think it's great GM is getting on the variable lift and timing control bandwagon, and even better that they're using roller followers and Direct injection. I just wish they would also use these technologies with the eAssist also. I wonder how resale will be affected of the 2.4L eAssist vs the GDI 2.5L with IVLC.
Posted by: Trevor Carlson | 29 May 2013 at 09:03 AM