GM 2.5L Receives Improved FE with Variable Intake Cam Lift

[xcel]

Consumers need everything they can to reduce expenditure at the pump and GM is clearly waking up to this fact.

Wayne Gerdes - CleanMPG - Sept. 17, 2012

2.5L Ecotec intake dual valve lift detail.

GM released an interesting PR this morning describing the upcoming 2.5L I4 Ecotec’s advances since our first drive with one in the standard Malibu earlier last year. The engine is said to provide better fuel economy thanks in aprt to a to a new valvetrain.

The engine uses a new Intake Valve Lift Control (IVLC) technology that enables variable intake valve lift, duration and timing over a wide range of engine operation. When the technology operates in low-lift mode, the engine pumps only the air it needs to meet the driver’s demand. Unfortunately it appears as if GM did not take advantage of any Atkinsonization possibility although I am speculating as GM said nothing to make us belive they added or did not add that fuel saving capability.

The system switches to high-lift mode at higher speeds or under heavy loads, providing the full output capability of the engine.

According to GM’s Global Ecotec engine Chief Engineer Mike Anderson, consumers will see upwards of a 1 mpg increase without sacrifice.

The engine achieves variable valve lift using an all-new for GM 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.

The D-segment Impala when equipped with the older 2.4L Ecotec and eAssist should see at least 35 mpg on the highway. This is a long way from the 40 mpgUS combined rating of the all-new D-segment Toyota Avalon Hybrid but should cost a few thousand $’s less. On the other side of the coin, the 2.4L w/ eAssist will be a vast improvement over the current 2013 Impala’s 3.6L whose owners a experiencing a very non-competitive and pump budget busting 18/30 mpgUS city/highway rating.

Other tidbits that lead to the upcoming 2014 Chevrolet Silverado V6 engine speculation earlier is that the 2014 Impala will be offered with an updated 3.6L V-6 providing an estimated at 303 horsepower. Anyone that purchases that engine for their upcoming Impala is simply out of touch but in a Silverado, that could finally turn some heads.

[PaleMelanesian]

Everyone likes to make fun of Honda's VTEC and its fans, but the concept is a winner. Everyone uses it now. Ford has Ti-VCT, Toyota has VVTI, GM has this IVLC, etc.

[RichXKU]

Originally Posted by PaleMelanesian

Everyone likes to make fun of Honda's VTEC and its fans, but the concept is a winner. Everyone uses it now. Ford has Ti-VCT, Toyota has VVTI, GM has this IVLC, etc.

I'm really surprised this is new to GM. Are they really that resistant to innovation?

[xcel]

Hi Rich:

It started with Mitsubishi and to see GM perform it with a solenoid operated roller arm is asking for problems. Honda shifts the follower from lobe to lobe with hydraulic pressure and that is it.

Something is wrong with this method to shift from a high load to a low load cam as it adds complexity beyond the hydraulic mechanism to move from position to position its competitors all use.

Wayne

[RichXKU]

Could there be patent issues preventing them from doing it another way?

[Topher]

Originally Posted by xcel

Hi Rich:

It started with Mitsubishi and to see GM perform it with a solenoid operated roller arm is asking for problems. Honda shifts the follower from lobe to lobe with hydraulic pressure and that is it.

Something is wrong with this method to shift from a high load to a low load cam as it adds complexity beyond the hydraulic mechanism to move from position to position its competitors all use.

Wayne

Wayne, it started much sooner than Mitsubishi...way back to the late 50's, through the 60's and into the 70's manufacturers were testing and patenting ways to vary valve timing and lift.

GM is doing the same thing here tons of other manufacturers are doing: using solenoids to control the application of the hydraulic pressure. It's the most common way to do so. The GM system shown does not move the arm directly with the solenoid, it uses the solenoid to control the hydraulic pressure available to the system. Which is the same thing Honda does with the VTEC.

The really neat thing will come once they can figure out how to create reliable fully electronic valves...imagine not having any other valvetrain than the valves themselves! No cam, no followers, no timing mechanisms....

Originally Posted by RichXKU

Could there be patent issues preventing them from doing it another way?

I'll bet there are patent issues to deal with.

[xcel]

Hi Topher:

The GM animation show a push rod mechanism to change the lift, Honda's slide over to a new cam profile with hydraulic pressure according to the schematics I have seen on the hybrids?

Was Mitsubishi the first to use variable valve time, lift and phasing in an OEM produced car?

TIA

Wayne

[RedylC94]

Originally Posted by Topher

The really neat thing will come once they can figure out how to create reliable fully electronic valves...imagine not having any other valvetrain than the valves themselves! No cam, no followers, no timing mechanisms ...

Yes, and probably no throttle, either. Imagine optimized timing and lift for every situation, all controlled by software. Such a system will require a lot of electrical power.

[Right Lane Cruiser]

Originally Posted by RedylC94

Yes, and probably no throttle, either. Imagine optimized timing and lift for every situation, all controlled by software. Such a system will require a lot of electrical power.

And some pretty awesomely bulletproof electronics/software!!

[PaleMelanesian]

Originally Posted by Right Lane Cruiser

And some pretty awesomely bulletproof electronics/software!!

Software is my day job. There's no such thing as bulletproof! I agree: