That's a variable timing system, not variable lift. Variable timing is easy because it only requires a cam phaser. Variable lift requires a separate cam profile and a mechanism to switch the follower from one profile to the other. I'd imagine on a pushrod V8 there's simply not enough room for that many profiles and related hardware ... I've never heard of it on a pushrod motor either. And AFAIK GM doesn't have any variable lift systems on any of their motors.

 

Cant forget better plug placement (on the DOHC stuff at least), and better port design - no pushrods to work around, but along with the high speed valve control issue - airflow requirements dont really seem to be an issue at the engine speeds most people tend to operate thier vehicles at. Multivalve heads also mitigate the need for agressive cam profiles in alot of cases.

 

Variable lift can be accomplished via a rocker arm and a lost-motion system:



With some imagination, you could see how such a system could also be applied to a pushrod engine. However, by the time you're putting that much complexity and packaging volume into the cylinder head, it's probably time to think about OHC.

 

I knew someone was going to mention Valvetronic

I kinda put it into a different category, since it doesn't use a different cam profile and therefore can't give you the best-of-both-worlds situation where you have a mild economical profile and a performance profile. All you get is one profile, and then varying degrees of lift of that profile.

On that topic, one of the benefits claimed for Valvetronic in just about every article I read is that it eliminates the main throttle body throttle blade, and therefore reduces pumping losses to increase efficiency. Instead, throttling is done by barely allowing the intake valve to open. This seems wrong to me: it doesn't matter where the throttling is happening, restricting the airflow is a pumping loss either way so I don't see where Valvetronic is an advantage in this respect. Any insights into this?

 

I think (but I don't know for sure) that the pumping losses are reduced not so much by the change in location of the restriction, but rather because the effective valve opening time is decreased as the lift decreases. If the valve isn't open, then any force put into rarifying the charge in the cylinder will be returned on the piston upstroke (the ultimate example of this is a cylinder where the valves aren't opening at all, such as in the deactivated cylinder of a DOD/MDS engine).

 

anybody remeber the hotrocker variable ratio rocker arms?



Not very elegant I suppose but it altered lift and duration by changing the rocker ratio from 1.1 to 1.7

 

That's variable timing. As others have clarified, I said variable lift.

Sorry, that's what I really meant -- aside from the Viper, I haven't seen a pushrod engine that varies intake and exhaust timing separately. Simply phasing the cam is relatively easy.

 

Because:

1. I'll backing them up in that statement.

2. GM's turbo 4 isn't a Ford EcoBoost engine.

3. Ford's Euro turbo 4 is not an EcoBoost engine.

4. When a knowledgeable person said wait and see on anything regarding Camaro, you waited to see.... same goes here regarding Ford.

Keep in mind, it's General Motors that's taking a chainsaw to engine programs and new vehicle development programs. Ford's not only funding everything, they're going to return to bi or tri-yearly facelifts on cars. Ford's actually making money on cars.

Ford is ahead of GM in quite a few areas. Reaction speed to a changing market, cash reserves to weather the next few years, labor reduction, cost management, and unless GM has a "Black Book" engine development operation that doesn't contain the word "Volt", engines as well (not to mention the 6F transmission which was developed jointly with GM which Ford got right).

This EcoBoost is actually everything it's cracked up to be. The 4s will put out V6 power, the V6 will put out upper V8 power. All this while not only retaining their fuel economy, but putting out far more power than the larger engine they are replacing, run far cleaner (for any potential new emission standards regarding CO2) and actually weigh less than the larger engine they will replace.

To put this into perspective, the EcoBoost V6 that's going to soon be in quite a few Fords, including the new performance Taurus is "rated" a mere 50 horsepower and torque less than the supercharged Cobra Mustang. Yet the engine weighs less than the n/a 4.6 in the Mustang and gets fuel economy ratings comparable to a V6 Mustang.

But then, Ford would NEVER be able to come up with such a engine... right?

 

Don't take this the wrong way Guy, I am your biggest fan after all , but what makes Ford's Ecoboost all that much different than the 2.0 DI Turbo Ecotec? Seriously it puts out V6 power while getting better economy, is lighter, and has better emissions. The point of my questioning is to ask how Ford's Ecoboost is so much better and so much further ahead even though so little is known about it at this time. Especially when GM's version is already on the market.

Sure for all we know GM has no answer to the Ecotec V6s (save the LSx engine series that is already top of the game) but what makes the Ecoboost 4 cylinders so much better?