2014 C7 Chevrolet Corvette

[P@ul]

Originally Posted by serialk11r

That's interesting, I wonder if hydraulic valve control will ever really take off (like Fiat multiair, though you can just vary lift ala Valvetronic for low power consumption and simplicity). Seems like you should be able to get some significant amount of lift variation through the lash adjuster with a high rocker arm ratio or whatever it's called. Thanks for the info.

My understanding is that Chrysler will integrate Multiair, eventually, into all of its overhead cam motors. Two of the three Dodge Dart engines have Multiair.

[ame="http://www.youtube.com/watch?v=0uiDmcPEekc"]MAHLE CamInCamâ„¢ camshaft - YouTube[/ame]

Cam in Cam, a cool video from Mahle. Chrysler teamed up with Mechadyne International and Mahle to launch cam in cam on the 2008 viper. I hope it shows up in the Corvette!

[ame="http://www.youtube.com/watch?v=W4JDi0K8htY"]HEMI 5.7L DODGE RAM MDS - YouTube[/ame]

MDS off the Hemi

[serialk11r]

Originally Posted by P@ul

My understanding is that Chrysler will integrate Multiair, eventually, into all of its overhead cam motors. Two of the three Dodge Dart engines have Multiair.

The issue I see with Multiair is that if you try to fully use its capabilities, the power consumption is crazy in some situations as the valve spring is not able to return its energy back to the cam. For limiting lift and duration together, there's no reason to have a solenoid anymore as you could devise a system that just moves the rockers, perhaps electronically would be a good solution.

i.e. it's great but a bit complicated. With a rocker adjuster thingy you'd have limited lift control but you could just use massive cam grinds so the low lift position is like your economy torque grind, the high lift high duration position can be used for bleeding off intake volume at low load (would want to optimize the fuel delivery and combustion chamber for the high lift though) and high rpm operation.

[ZionsWrath]

I really like what I have seen so far. Can't wait to see people track them and see how well those factory cooling devices work and how the brakes hold up with proper pads.

Also very curious to see the automatic as I think they said it is 6 speed vs the manual 7, which I find strange...

Will probably consider one in the future when I have a home and can afford it as a second car. Provided I haven't sunk too much money in my BRZ

[strat61caster]

Originally Posted by serialk11r

The issue I see with Multiair is that if you try to fully use its capabilities, the power consumption is crazy in some situations as the valve spring is not able to return its energy back to the cam. For limiting lift and duration together, there's no reason to have a solenoid anymore as you could devise a system that just moves the rockers, perhaps electronically would be a good solution.

[ame="http://www.youtube.com/watch?feature=player_embedded&v=Bch5B23_pu0"]The Future of the Internal Combustion Engine - /Inside Koenigsegg - YouTube[/ame]

MultiAir is decidedely Italian in my mind, very complex but an elegant contained system. And if it helps them make engines sound like the Abarth it'll work out well for them and Chrysler. Koenigsegg is playing with air instead of fluid, I think the fluid system would have better control under duress, more reliability but fewer long term evolutions.

Corvettes are cool.

[Admiral Ballsy]

FWIW, GM said that they considered cam-in-cam and decided that it wasn't worth the complexity. Seems like they said you got ~85% of the benefits from just varying the clocking of the entire cam (something they've done for over a decade), and the last 15% wasn't worth the trouble.

[Admiral Ballsy]

Originally Posted by LSxJunkie

you have to pull the heads to get to the lifters.

Huh?

I guess I've been doing it wrong.

[serialk11r]

Originally Posted by strat61caster

MultiAir is decidedely Italian in my mind, very complex but an elegant contained system. And if it helps them make engines sound like the Abarth it'll work out well for them and Chrysler. Koenigsegg is playing with air instead of fluid, I think the fluid system would have better control under duress, more reliability but fewer long term evolutions.

Corvettes are cool.

Yup. Ferrari could actually get pretty close to MultiAir performance efficiency-wise if they were willing to change the torque curve a bit; Extend the duration on the low rpm part and use that to cut pumping losses.

I'm quite surprised that MultiAir is a fully functional production system; actively controlling all those valves is one of those things that seems like it could get very complicated, and they had to figure out how to damp the valves in the case that they release oil pressure when the spring is loaded.

The problem I see with fully camless actuation is that you have no limp feature; any malfunction in an actuator and that cylinder is done. Additionally, at low power levels the power consumption of the valves will destroy the efficiency. It would be cool if an automaker tried lift adjustment via a modified hydraulic lash adjuster of some sort, that would be a robust solution that gets you a significant portion of the way there.

[arghx7]

Originally Posted by serialk11r

Yup. Ferrari could actually get pretty close to MultiAir performance efficiency-wise if they were willing to change the torque curve a bit; Extend the duration on the low rpm part and use that to cut pumping losses.

I'm quite surprised that MultiAir is a fully functional production system; actively controlling all those valves is one of those things that seems like it could get very complicated, and they had to figure out how to damp the valves in the case that they release oil pressure when the spring is loaded.

If you think MultiAir is complicated, you should study other continuously variable valve lift systems. The beauty of MultiAir is the simplicity of the hardware. There's no cam phaser and there's only one cam shaft. There's no electric motor, no worm gear set, no crazy moving links and extra shafts. It's just a few solenoids with hydraulics, some followers, and conventional exhaust valve actuation. Look at complexity of Nissan and Hyundai's systems and you'll see what I'm saying about how simple MultiAir really is.

Also, MultiAir is actually UniAir by the Schaeffler group. It's a German technology. See this paper by them: https://docs.google.com/file/d/0B_jE...it?usp=sharing . It explains how the braking function of the valve and how energy is transferred through the system.

[P@ul]

Originally Posted by Admiral Ballsy

FWIW, GM said that they considered cam-in-cam and decided that it wasn't worth the complexity. Seems like they said you got ~85% of the benefits from just varying the clocking of the entire cam (something they've done for over a decade), and the last 15% wasn't worth the trouble.

I'm guessing the limited amount of independent phasing (limited angle adjustment or speed of phaser adjustment) isn't worth the cost. Everything is a juggling game. I'm still curious if that was the general opinion of cam-in-cam or just for the base Corvette. I still have a techno boner for it, so where's the Z06 cam in cam?? Hahaha!

One of the curious comments I just read while looking up those comments was that the Viper's uses cam in cam mainly for emissions / idle quality /fuel economy. They said they could gain quite a bit of low end torque playing with the intake cam phasing, but that would only destroy the tires. Haha, #displacementproblems

... I wish I had displacement problems.

[P@ul]

Originally Posted by arghx7

If you think MultiAir is complicated, you should study other continuously variable valve lift systems. The beauty of MultiAir is the simplicity of the hardware. There's no cam phaser and there's only one cam shaft. There's no electric motor, no worm gear set, no crazy moving links and extra shafts. It's just a few solenoids with hydraulics, some followers, and conventional exhaust valve actuation. Look at complexity of Nissan and Hyundai's systems and you'll see what I'm saying about how simple MultiAir really is.

That was my understanding. It's much simpler than Nissan and BMW's equivalent systems, variable valve systems that can run without throttle bodies.

[P@ul]

In more relevant news, The C7 just threw down 411 hp and 407 lbft on a dynojet in a test by Edmunds. http://www.edmunds.com/car-reviews/t...dyno-test.html

[serialk11r]

Originally Posted by arghx7

If you think MultiAir is complicated, you should study other continuously variable valve lift systems. The beauty of MultiAir is the simplicity of the hardware. There's no cam phaser and there's only one cam shaft. There's no electric motor, no worm gear set, no crazy moving links and extra shafts. It's just a few solenoids with hydraulics, some followers, and conventional exhaust valve actuation. Look at complexity of Nissan and Hyundai's systems and you'll see what I'm saying about how simple MultiAir really is.

Whoa wait, Hyundai has one now?

I know what you mean, the extra shafts and rockers and stuff are crazy compared to MultiAir's simple valve system, but MultiAir has to be more clever and it's awesome that they got it working.

[arghx7]

Originally Posted by serialk11r

Whoa wait, Hyundai has one now?

http://www.google.com/patents/US8079333 yes and it's going into production. I saw a display engine a few months ago at a conference.

I know what you mean, the extra shafts and rockers and stuff are crazy compared to MultiAir's simple valve system, but MultiAir has to be more clever and it's awesome that they got it working.

MultiAir runs off oil. That's the tricky part. The system is hydraulic, and like any hydraulic system it's subject to the characteristics of the fluid (temperature, viscosity, etc).

[Admiral Ballsy]

Originally Posted by LSxJunkie

You're kidding, right?

There is no possible way to get the lifters out of an LSx/LTx without pulling the heads.

Yeah, you're right, I misread (or misunderstood) - for some reason I read 'lifter' and was thinking 'pushrod'. Mea culpa.