There is so much talk about engine hp and weight. In ACAR they said that a decrease in engine weight of 1lb would correspond to the ability to lower the vehicle weight an additional lb. I think they can decrease the weight of the engine and put in better components at the same time.

Will the C6 get titanium springs, forged internals, headers that are not made out of cast iron?

 

Titanium springs would be a waste, if you're talking about valve springs. Forged internals would be too expensive. Headers could, and possibly likely, be either titanium or magnesium. :cool:

I think the killer is the weight of the body, frame, and suspension. I know they're using plastic on the current C5, and that's good, but carbonfiber panels weigh half as much as their plastic counterparts. Although it's too expensive at the moment, one day, it will be commonplace.

The frame is steel, and that's inherently heavy, no matter what you do. You can lighten it up with VTH, but that only goes so far. Engine mounts will be magnesium, exhaust most likely titanium, wheels magnesium, manifolds magnesium, hood carbonfiber, frame VTH...

I think they can drop about 100-150 lbs with that stuff. But at what cost?


EDIT: VTH = Variable Thickness Hydroforming


[Modified by GDP, 7:00 PM 10/2/2003]

 

What is VTH?

 

Variable Thickness Hydroforming?

 

I am not an internal combustion engine expert but I think
I can safely say a few things here. While the absolute
weight of the engine would be nice to keep down, it goes
beyond that. Things like the crank-connecting rod-piston
assembly are undergoing continued accelerations as are
the members of the valvetrain. Dropping the mass of these
critters is really useful. If you can keep the weight
of the connecting rods and pistons down, the crank
counterweights can be made smaller. Now the block doesn't
need quite so much metal to hold on to the crank. There's
also a lot of power required to accelerate these high-
inertia parts. If you can drop the weight of the valve-
valve spring-retainer assembly you can either drop valve
spring pressure and reduce internal friction or make
the cam more aggressive or increase the RPM limit. Next,
titanium springs can be made shorter so that the valve
can be shorter which reduces engine height and valvetrain
mass.

While the age-old debate goes on about 2V versus 4V engines,
and the hp/liter of these engines, one rarely hears about
two other relevant quality measures of the engine. What is
the hp/weight or hp/volume? Ideally, an engine puts out
400hp but weighs nothing and takes up no space. The heavier
it is, the more the rest of the vehicle must be designed to
cope with that weight. If it's big, then space must be made
for it and that usually implies more metal. While the LS2
may get to only 75-80hp/liter, I think the place where it will
really shine is in its relatively low weight and compactness.

Forged? I think all connecting rods for GenIII V8's are made
from compressed powders - PF1159. These are very strong rods
and I don't worry about them other than that they are steel
and not titanium. Titanium powdered rods are apparently not
ready for prime time yet. We'll see if the crank is forged.
Since they are going with a titanium valvetrain, I expect part
of that mass savings will go the increasing RPM limits. The pistons
better be pretty strong to make it to at least 7000RPM. Forging
sounds like a good idea.



[Modified by Runge_Kutta, 2:40 PM 10/1/2003]

 

I have read that and it is used as an agrument against DOHC engines. The OHV can be made smaller and lighter than any OHC engine with the same displacement. Thus weight can be saved in the car.

tom...

 

Variable Thickness Hydroforming

 

:iagree: But the mass of a spring is, ideally, mass-less (Physics theory). It doesn't matter what material it's made from, what matters is its springiness and ability to return energy put in. Everything else, by all means, make it out of Ti!

I read somewhere that Ti is more flexible than steel, or it might have been that it expands more. I don't remember. Either way, that's one of its limits. Now, Chromoly... :cool:

 

No. If you do the physics correctly, a fraction of the spring weight is effectively added to the main mass (valve). I think the fraction is 1/3 under usual assumptions. So it is important for very high rpm.