New C6 article...
Race Director
Joined: Nov 2001
Posts: 17,527
Likes: 4
Re: New C6 article... (Mervz)
Two things that really excite me about the C6:
1. Electronic valve actuation
2. Weight reduction
Current Z06 = 7.7 lb/hp
Future Z06 with 500 lb lost and 500 hp = 5.3 lb/hp
That would be incredible. :)
1. Electronic valve actuation
2. Weight reduction
Current Z06 = 7.7 lb/hp
Future Z06 with 500 lb lost and 500 hp = 5.3 lb/hp
That would be incredible. :)
Racer
Joined: Sep 2001
Posts: 492
Likes: 6
From: Orange County CA
Re: New C6 article... (Watts'02MagRedVert)
Duke you are correct they are pneumatic Valve Springs, however, I heard that on the latest Wide Angle 112 degree Renault V10 they are not running camshafts. But in F1 everything is so secretive who knows. :eek:
Instructor
Joined: Dec 2000
Posts: 188
Likes: 0
From: Fresno California
Re: New C6 article... (SJ)
SJ
Keep in mind I'm far from an expert on this sub.
With that said, in F-1, this set up had been played with in the past. They even played with Air to open and close the valves. Even a couple years ago Ferrari played with the DESMO Valve set up, as used in the Ducati 748, 916, 996, 998, and I believe 999. But everything seemed to lead back to the DOHC set up. As for what they are using now, I believe it's back to the DOHC.
Keep in mind Tech has greatly improved since then, so it is possible for various elements in the Electric Valve operating system to be improved on. Thus making it lighter, more compact and more accurate. I guess you could call in New Tech, since it has never been used in a production car, but being that it has been toyed with in the past, in racing, I see it as being old Tech.
Justin C.
Keep in mind I'm far from an expert on this sub.
With that said, in F-1, this set up had been played with in the past. They even played with Air to open and close the valves. Even a couple years ago Ferrari played with the DESMO Valve set up, as used in the Ducati 748, 916, 996, 998, and I believe 999. But everything seemed to lead back to the DOHC set up. As for what they are using now, I believe it's back to the DOHC.
Keep in mind Tech has greatly improved since then, so it is possible for various elements in the Electric Valve operating system to be improved on. Thus making it lighter, more compact and more accurate. I guess you could call in New Tech, since it has never been used in a production car, but being that it has been toyed with in the past, in racing, I see it as being old Tech.
Justin C.
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,271
Re: New C6 article... (PJRACING57)
Variable valve timing won't do much good on F1 engines or any other racing engine because they only need to operate over a fairly narrow range. F1 gear spacing is about 10 percent and all they have to worry about is the top ten to twenty percent of the rev range.
The benefit of infinitely variable valve timing is a flatter WOT torque curve and more efficient (both in terms of fuel consumption and emissions) part throttle and idle operation. The concept has been around forever and is generally known in technical circles as "inlet valve throttling". If the valve lift and duration can be contolled through a wide range, no throttle valve is necessary. The problem has always been finding a reliable and reasonably inexpensive actuation system. They appear to be a lot closer, but I'm not holding my breathe, and I don't think I'd want to be the first guy on the block to try out this technology. There will be a lot of things to break and a lot of bugs to work out!
The image posted earlier illustrates one problem - space. That's one reason why the Corvette has a pushrod engine - it has a much lower height than a DOHC design. Add big, bulky valve actuators and the cowl height will have to go up, so you're back to sitting in a hole like a C4.
Duke
The benefit of infinitely variable valve timing is a flatter WOT torque curve and more efficient (both in terms of fuel consumption and emissions) part throttle and idle operation. The concept has been around forever and is generally known in technical circles as "inlet valve throttling". If the valve lift and duration can be contolled through a wide range, no throttle valve is necessary. The problem has always been finding a reliable and reasonably inexpensive actuation system. They appear to be a lot closer, but I'm not holding my breathe, and I don't think I'd want to be the first guy on the block to try out this technology. There will be a lot of things to break and a lot of bugs to work out!
The image posted earlier illustrates one problem - space. That's one reason why the Corvette has a pushrod engine - it has a much lower height than a DOHC design. Add big, bulky valve actuators and the cowl height will have to go up, so you're back to sitting in a hole like a C4.
Duke
Drifting
Joined: Feb 2002
Posts: 1,260
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From: Chapel Hill NC
Re: New C6 article... (SWCDuke)
Add to Duke's comments two other issues with electric valve mechanisms; weight and rpm range.
The last technical articles I saw on the electric mechanism speculated that the first applications would be on compresseion ignition engines because the current mechanisms don't have the RPM range for spark ignition engines. Also, the electric mechanism would have to show a considerable advantage over the mechanical ways of varying valve timing to make up for the cost and dependability issues with the electric mechanism.
The weight problem is self evident. Look where the weight is located. Very high in the block. In fact, high above the combustion chambers. Not a good location to add weight.
All in all, if you compare the two cam in block design with the electric valve design, there's an awful lot in favor of the two cam in block design. Most of the varible valve control advantages, a lot less weight and proven dependibility of design favors the two cam in block.
If GM goes to an advanced design, I'd bet on the two cam in block design over the electric valves. :cool:
The last technical articles I saw on the electric mechanism speculated that the first applications would be on compresseion ignition engines because the current mechanisms don't have the RPM range for spark ignition engines. Also, the electric mechanism would have to show a considerable advantage over the mechanical ways of varying valve timing to make up for the cost and dependability issues with the electric mechanism.
The weight problem is self evident. Look where the weight is located. Very high in the block. In fact, high above the combustion chambers. Not a good location to add weight.
All in all, if you compare the two cam in block design with the electric valve design, there's an awful lot in favor of the two cam in block design. Most of the varible valve control advantages, a lot less weight and proven dependibility of design favors the two cam in block.
If GM goes to an advanced design, I'd bet on the two cam in block design over the electric valves. :cool:
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,271
Re: New C6 article... (RandyB)
Current Corvette engines have a 90 percent torque bandwidth from about 1500 to the rev limit without variable valve timing or variable inlet geometry. That's very impressive! With the independently variable inlet and exhaust valve timing of the "twin cam" Gen IV we may have to start taking about the 95 percent torque bandwidth. Buy comparison, a good Special High Performance engine option from the sixties made an 80 percent torque bandwidth from about 2000 to 6000.
Theoretically, inlet valve throttling should yield a torque curve that is essentially flat across the entire operating range - from off idle to the rev limit, but I question whether the improvement is worth the cost/complexity and potential service problems of electronic controlled/electrically actuated valves.
Conventional cams have proven to be inexpensive and reliable for over 100 years and with current mechanical variable timing mechanisms it's a tough system to beat. Technology does have some practical limits. At some point it can become pie in the sky.
Duke
Theoretically, inlet valve throttling should yield a torque curve that is essentially flat across the entire operating range - from off idle to the rev limit, but I question whether the improvement is worth the cost/complexity and potential service problems of electronic controlled/electrically actuated valves.
Conventional cams have proven to be inexpensive and reliable for over 100 years and with current mechanical variable timing mechanisms it's a tough system to beat. Technology does have some practical limits. At some point it can become pie in the sky.
Duke
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Instructor
Joined: Oct 1999
Posts: 183
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From: North Bend WA
Re: New C6 article... (I Bin Therbefor)
So what's to stop someone from moving the electric valve actuators down and out and actuating them via a rocker? That would seem to deal with the engine height and higher c.g. issues..
Thread Starter
Race Director
Joined: Sep 2000
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From: Hillsborough NH
Cruise-In V Veteran
Cruise-In VI Veteran
Re: New C6 article... (smosier)
i think you guys are highly over exagerating the weight issues. The acuators and other components don't weigh more than the cam, pushrods, timeing chain, timing cover, etc... :)
Instructor
Joined: Feb 2000
Posts: 213
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From: Parkland FL
Re: New C6 article... (PJRACING57)
Thanks for the explanation, PJRACING57. It sounds like the electronics at the time were not up to the level of subsequent cam technology, so what ends up in the C6 is still anybody's guess.
