Runge_Kutta

I just wanted to ramble a bit here in regard to the upcoming
LS2 and LS7 - speculated (Mervz) to be the C6 engines. From
Mervz's post, the LS2 is 6.0 liters while the LS7 is a 6.4
liter engine.
http://forums.corvetteforum.com/zerothread?id=502610

As to power, the LS2 will have between 425HP and 435HP
depending on who you believe. Ernie says 435HP
http://www.lovecars.com/corvettecorner/c6.htm

while the April 2003 Motor Trend says 425HP. I suspect
that Motor Trend is lowballing to allow for a last
minute surprise. Motor Trend also speaks of a titanium
valvetrain which I assume to mean valves, valve springs,
and retainers. This may explain the comments about
a 7800RPM redline for the Cadillac CTSv.
http://forums.corvetteforum.com/zerothread?id=483562

The connecting rods may also be made of titanium.
http://forums.corvetteforum.com/zerothread?id=450510

Motor Trend made the comment that the new C6 engine(s)
will have considerably higher specific output but will
not depart significantly from the current GenIII architecture.

_____LS1___LS2___LS6___LS7___XV16
HP___350___435___405___500___1000
LT____5.7____6.0___5.7___6.4___13.6
Eta__61_4___72_5__71_1__78_1___73.5

If you look at the numbers, its not a dramatic improvement. In
any event, it's interesting to ask how this is going to be accomplished.

At the exhibition of the Cadillac Sixteen, Thomas Stephens
http://www.gm.com/company/investor_i...s/stephens.htm

said that the XV16 was a showcase for the future direction of the
small-block architecture. That engine has titanium valves, valve
springs, and two valves per cylinder. I guess this means that the
LS2 and LS7 are not three valve per cylinder engines!!
http://katechengines.com/
http://media.gm.com/events/productse...s/stephens.pdf

Check out his slideshow. So much for the 3V OHV engines going into
C6 (slide 17). I would, however expect to see the exhaust manifold integrated
into the cylinder head (slide 18). Also look at
http://media.gm.com/events/productse...t_manifold.htm

Back to the original slideshow. Look at slide 27. The specific
output (which is reputed to increase with C6) doesn't go over 70HP/L
for the 2V OHV engines. Maybe the LS7 will approach 80HP/L.
http://media.gm.com/events/detroit03...en_engine.html

It's amazing that the XV16 is only 695 pounds or 315 kilograms! That's
only 50% heavier than an LS1!!!

"The XV16's valves are titanium alloy, an extremely lightweight material.
The engine also employs titanium alloy valve springs, which are 40 percent
lighter than comparable steel designs. The titanium helps increase the
springs' natural frequency by 28 percent to allow for higher engine speeds."

"The GM XV16 also uses a dry-sump scavenge pump system integrated with the
main oil pressure pump. The dry-sump helps reduce overall height for
improved packaging while making the vehicle capable of more aggressive
cornering. The system has eight individual scavenge pumps to evacuate oil
from the sump for improved performance and fuel efficiency."

Well, I'd love to see more details on these babies. We can only hope
that C6 will use titanium as liberally as it is used in the XV16.





[Modified by Runge_Kutta, 7:05 PM 3/3/2003]

Senna1994

Great Article, nice job. :cheers:

Rocketblock

:iagree: It's time for GM to step to the plate and do what we know they can do!!! :yesnod:

Jinx

Do we expect LS2/LS7 to be dry sump? Even shorter/lower engine than LS1/LS6? Or does height saved down below simply become available to use up top (taller/longer/larger runners, a second camshaft)?

Do we expect cylinder deactivation with C6 debut, or a year or two later? I believe fleet trucks are getting this in 2003, yes?

Two-cams-in-block still makes sense for a two-valve head design, yes? Do we still think this is in the cards for LS2/LS7?

.Jinx
P.S. How do you find these presentation files?


[Modified by Jinx, 6:32 PM 3/3/2003]

Patrick96LT4

Cool post. Thanks for the consolidation! :thumbs:

GDP

:cool:

scorp508

And kill the aftermarket exhaust business? I doubt it.

snide

Very interesting...

peccles

Assuming no DoD for the LS2/LS7 at first, will the C6 be able still avoid the gas guzzler
tax? I would think the base C6 could but it would be a real engineering feat for C6-Z06
to avoid it.

DSTJ99

Great Info and summary. Keep up the good work :thumbs:

Scissors

The C6 will be lighter and, hopefully, have a better coefficient of drag; both of which contribute to improved gas milage as well as superior performance.

Jinx

Now why would General Motors, in the business of making new vehicles, care one iota about the aftermarket exhaust business?

In any event, it only tweaks the aftermarket header business. Catbacks would continue to provide the fat pipes and farting sounds the kids demand today.

.Jinx

Curtis A. Franz

The connecting rods may also be made of titanium. http://forums.corvetteforum.com/zerothread?id=450510

I remember when all that came up. For the record, I have a Porsche lover friend (aka Porsche nut) that attended a Porsche bash in MA last weekend where he was told that titanium connecting rods stretch. For their racing applications they change them after a race. Doesn't sound like something for the street to me.
:chevy

Curtis A. Franz

Do we expect LS2/LS7 to be dry sump? Even shorter/lower engine than LS1/LS6? Or does height saved down below simply become available to use up top (taller/longer/larger runners, a second camshaft)?
Do we expect cylinder deactivation with C6 debut, or a year or two later? I believe fleet trucks are getting this in 2003, yes?

Two-cams-in-block still makes sense for a two-valve head design, yes? Do we still think this is in the cards for LS2/LS7?



I see no reason why the C6 couldn't be dry sump. It might just be the Z06 replacemeant tho. Cylinder deactivation is not going into the C6 at least not at first. That has been stated by perhaps Phil Hill. I believe the LS2 will still be one cam in the block and the next year we may see two for the Z06 (LS7).
I think we could see the LS2 for the 2004 model year.

:chevy


[Modified by Curtis A. Franz, 12:42 PM 3/4/2003]

SWCDuke

Any metal will "stretch" when loaded in tension, but a high cyclic loaded part will never see sufficient load to stretch inelastically i.e. permanently. High cyclic loading requires peak unit stress to be within the fatigue "endurance limit", which is always much lower than the yeild limit.

Changing connecting rods on a regular basis is common practice on very high revving engines as they may be loaded greater than the generally accepted endurance limit for infinite fatigue life. The Ferrari F355/360 and NSX are two examples of production cars that have titanium rods, and there is not recommended change interval for normal driving. Since connecting rod loading is primarily inertial, a light weight material is very advantageous, but aluminum is a poor choice because it has much poorer fatigue life than steel or titanium. Some drag racing engines use aluminum rods, but they are changed as often as every run in Top Fuel and Funny Cars.

Changing connecting rods to preclude fatigure failure is common in racing engines, but the "stretch" story is bunk!

Duke

Runge_Kutta

>> Do we expect LS2/LS7 to be dry sump?

If you take Tom Stephens at his word then yes.

>> Even shorter/lower engine than LS1/LS6?

The dry sump system might lower it an inch or so (wild guess). I see no
reason why length and width might decrease. The titanium valves ought
to be shorter than the LS1/LS6 valves because the springs don't need to
be as tall.

>> Or does height saved down below simply become available
>> to use up top (taller/longer/larger runners, a second camshaft)?

The dual camshaft idea appears not to be the selected layout for the Gen IV
engine. Who knows what will become of it??

>> Do we expect cylinder deactivation with C6 debut, or a year or two later?

Again, if you believe Tom Stephens, cylinder deactivation will be on all C6's.
That's why Motor Trend states that the milage is going up. Motor Trend is
pretty clear about DoD on C6.

>> Two-cams-in-block still makes sense for a two-valve head design, yes?

That's not the way I read all of this. I'm really curious how the variable
valve timing will be done. Sounds like its just on the intakes but I
may be wrong.

>> How do you find these presentation files?

Google. Google knows all!!

>>>> I would, however expect to see the exhaust manifold integrated
>>>> into the cylinder head (slide 18).
>> And kill the aftermarket exhaust business? I doubt it.

The biggest source of engine emissions is the startup phase.
These manifolds are an engineering approach to minimize this
startup emission problem. So, does GM reduce emissions with
the modified heads thus allowing them to use less downstream
treatment and potentially save money, space, and net an overall
emissions reduction or do they worry about the aftermarket
header business??

>> Assuming no DoD for the LS2/LS7 at first, will the C6 be able
>> still avoid the gas guzzler tax?

Motor Trend suggested mileage on the order of 20/30+. I think the
manual C5s are 18/28 or so. C6 will have the DoD plus be lighter.
I have heard the loose comment that 60% of mileage is the vehicle
mass.

>> I remember when all that came up. For the record, I have a Porsche
>> lover friend (aka Porsche nut) that attended a Porsche bash in MA
>> last weekend where he was told that titanium connecting rods stretch.
>> For their racing applications they change them after a race. Doesn't
>> sound like something for the street to me.

While I am no material scientist, I think that worry is baseless. I
couldn't image a reason that a well-designed Ti con-rod would
have a mechanical problem in this application. The NSX and Maranello
seem to be doing quite well. The one issue is on wear surfaces but
if your willing to pony up some bucks, that can be dealt with.

>> I think we could see the LS2 for the 2004 model year.

That thought had crossed my mind too. We'll see!!

One thing that hasn't been addressed is how these 2V engines are
going to get enough airflow to put out such big HP. I don't think
that it's a huge leap of faith to say that the head will have to
flow better and that the valves will have to be bigger.

Alex1217

Thanks for putting it all in perspective. If these figures are correct, the C6 should truly be awesome no matter what it looks like.

Curtis A. Franz

One thing that hasn't been addressed is how these 2V engines are
going to get enough airflow to put out such big HP. I don't think
that it's a huge leap of faith to say that the head will have to
flow better and that the valves will have to be bigger.

Exactly. I can't see lots of more cam overlap to get the HP. There have to be some other tricks going on here. I could see varying the advance/retard of a single cam like is done on the Trailblazer as part of it. There is not much there tho. I could also see using the bore of the C5R (427 cu in) to change the bore to stroke relationship to get somewhat bigger valves. Still not enough. Darn interesting isn't it.

Hey that bit of changing titanium connecting rods came from Porsche racing experience. Belittle it all you want but that was no hick get together. I am only the messenger here and it was a factory related speaker.
:chevy

Scissors

If we're really lucky, the LS2 and LS7 will have a manual choke. :lol:

Runge_Kutta

Curtis,

Let's distinguish between elastic and plastic ``stretch.''
If the stretch is elastic then when the stress is removed, the
rod will return to its unloaded state. If the accelerations
of the rod induce an elastic stretching then the designer
must make allowances for it. However, if you're talking about
plastic deformation, or permanent stretch then I think the
rod was likely designed badly. Another issue that might arise
is if th rods are made from titanium powder and there are
nonnegligible impurities in the powder. Then, I would imagine,
the rod just breaks.

Again, I am not a material scientist ...