SWCDuke

For those of you who still consider pushrod engines to be "obsolete" or "old tech", consider the following brief history.

Certainly by the late eighties when the Corvette's L-98 engine produced a whopping 250 HP from 350 CID, the last nail in the coffin of pushrod technology had been pounded in, right?

I had given up years before (as exemplified by my purchase of a Cosworth Vega in 1976), and saw the elegance of the modern narrow valve angle reincarnation of the four valve DOHC head that was first laid out by Keith Duckworth in the late sixties. The centrally located spark plug and compact combustion chamber, with just modest quench zones compared to the wedge chamber in typical OHV V-8s, yielded both excellent thermal efficiency, detonation resistance, and low "engine out" emissions, and the cylinder head flow numbers are what guys only dream about.

The actual mechanical complexity of the layout was minimized with the single piece cam carrier with integral cam bearings and belt driven cams. In fact, there are considerably fewer moving parts per valve than on a pushrod design. In engineering, simplicity and elegance usually go hand in hand.

Then GM threw a fly in the ointment by developing the LT1 V-8 in the early nineties. In one fell swoop, power increased 20 percent, and the new LT1 had higher net specific output (HP/CID) than any previous small block V-8. Not resting on their laurels, they went on to develop the LT4, LS1, LS6, and now the LS2 to be followed in the not too distant future by the LS7, which will undoubtedly raise the bar for specific output while maintaining the pushrod V-8's low internal friction for miserly fuel consumption, light weight, small package volume, and high torque with outstanding torque bandwidth that flows from being able to package more displacement per unit mass and volume than DOHC designs.

In short, GM keeps REINVENTING the pushrod V-8, which keeps forcing me to redefine what "high tech" means. The LS7's peak output is expected to be DOUBLE the L-98 (with better EPA fuel economy), in a package that is lighter and shorter in length and height with only a slight increase in width, and given the expected increase in displacement this will represent a specific output increase of close to 80 percent!

If any of you out there are with GM Powertrain, I offer my hearty congratulations for the job you have done, and hope you keep up the great work in the future. :flag

Duke




[Modified by SWCDuke, 7:18 PM 1/17/2004]

Jimwood

The Corvette Engine is obsolete in light of Fords supercharged 4.6 and 5.4.
Ironic...

RGGregory

Jimwood,

How so?

DngrZne

I would very much disagree. Ford's use of a supercharger is an attempt to make up for their engines' shortcomings. Bolt a supercharger on an LS1, LS6 or LS2 and compare the numbers you get. When you have to resort to the use of forced induction to compete with cars that are N/A and still are at a performance disadvantage that tells me there is something seriously wrong with your design.

Jimwood

Simple, you are getting more HP out of less displacement WITHOUT sacraficing torque. To me thats more sophfisticated then raw displacement. Is the 6L cool yes. But a 5.8 supercharged engine would have been sweet.

Plus, with a couple dollars in mods the Supercharged 4.6 puts down 416 RWHP. Thats pretty damn amazing.

Im thinking real hard about getting an 03 or 04. Just more exciting that with a 3800 dollar check made out to Kenne Bell, I would be looking at 500+ RWHP.

500 RWHP from a 4.6 is advanced technology in my mind. With a c6 your looking at 350 from 6.0L. Not that impressive to me. The 454 Carb Mercruiser in my 84 boat puts out 330. So a 6.0L with EFI at 400. Not that impressive, not that advanced. Sorry.

Jimwood

The 03 Cobra is at a performance disadvantage??? I know you are not serious. The Cobra may be a fat pig, but it is not at a performance disadvantage.

DngrZne

If that's your argument then go out and buy a Civic and run 30 psi through it. Very high tech, until it explodes. GM could have quite easily thrown a blower on the Vette and called it a day, the difference is they didn't have to. The fuel economy is quite impressive for the displacement with an extremely flat torque curve and exceptional reliability. I would say that the N/A engine pushing 400+ HP is more technologically advanced to be able to make that kind of power without running at positive manifold pressure. It shows much more thought out airflow and comustion design then merely saying "ok, well...this is all we can get out of the engine...any ideas? yeah!...why don't we put a supercharger on it!" The supercharged engine is already that much closer to being maxed out, while the N/A engine could have a supercharger thrown on it and completely demolish that little Ford toy.

I just can't get around seeing throwing a blower on the engine as an easy way out, not better engineering.

Jimwood

DngrZne, Im not talking about a blown civic, with no torque. Im talking about a Ford 4.6 SC engine. Theres a difference. The engine is sweet, looks good, and beats corvettes on a regular basis around these parts. But maybe the airs a little more humid elsewhere. :lol:

DngrZne

First thing I wanna say, is I hope that you're not taking my giving you a hard time personally. Just debates like this are kind of fun :cheers:

From what I've been reading, the 4.6L Cobra engine puts out 390HP @ 8psi and the 5.4L Lightning engine 380HP @ 8psi. The 5.7L LS6 puts out 405HP while running at a manifold vacuum. Stock for stock the N/A engine wins. Now, granted, it's much cheaper to change a pully on the supercharged engine and bump up the boost, but at 8 psi already you can't increase the boost too much more without having to tear into the motor and do some serious upgrades. The N/A engine has many more options available and different paths that can be taken. It could be done with heads and cam and remain N/A or with forced induction. The initial costs of mods will be higher, but I believe they will yield a greater result.

LittleBoyBlu99

:iagree: :yesnod:

Jimwood

:cheers:

:cheers:

The ford actually puts out more HP: http://www.dynoperformance.com/artic...ails.php?ID=28

Now the corvette, body wise is definetly much better in ALL aspects then the mustang.

But engine wise, I think we will just have to agree to disagree. And I disagree that adding heads, headers, cam, exhaust, is ultimately more reliable then adding a different pulley.

My LT1 was a wreck. Not very happy with the electric gadgets reliability of that engine, or the leaking engine seals. But thats another story. But Z06 owners dont seem to happy with oil consumption, either. Im not sure GM has shown that it produces a better engine.
.
400HP and 6L is great, but its relative. Just like the 5.0

DngrZne

Fair enough :D :cheers:

LS1LT1

Way to go GM/Chevrolet! :hurray: :cheers:

With a blower on top of it a 4.6 is theoretically no longer a 4.6 (and the 5.4 is no longer 5.4 etc.), a blower actually adds displacement, at least that's how things are classified in any kind of sactioned racing where forced induction engines compete against naturally aspirated ones.
So while it appears in some cases to be making as much or more hp/torque per liter or cubic inch it is a bit misleading.
And of course the Cobra 4.6s 3 extra cams and 16 extra valves play a nice role as well. ;)

FAST LS1

Jimwood, your right, in terms of moddability the Cobra and Lightning engines are much easier to modify than any of the LS* engines.
In terms of technological advancements though they are much farther behind. The mod motor is physically a very large engine that's very heavy for it's cubic inch size. The technology of DOHC and SOHC actually came before push rods, so technically the pushrod design is more "modern" than DOHC. Also the mod motors don't use the inherent advantages they have of being able to rev high due to the DOHC design. The LS6 revs to 6800rpm while the old Cobra engine went to 7000-7200 while the new supercharged one is back down to 6500-6700rpm? which isn't putting the main thing it has going for it, the DOHC design, to work. The LS* engines, are more compact, lower weight for larger ci engines, lower center of gravity, more fuel efficient, and more reliable since they have fewer parts like a supercharger to go wrong. To me the LS* engines are much more advanced than Ford's mod motor. Ford's DOHC and SOHC engines are actually far behind other manufatures that use the SOHC and DOHC designs. They have no variable valve timing, no variable lift like V-tec. They no longer have variable intakes or many of the things that are very common in other current DOHC engines. While GM's constant advancement of the OHV design has pushed the LS* based engines far beyond what any other manufaturer has done with that design in recent years. Soon GM will release the 3 valve OHC engine that will again raise the bar even higher for OHC engines in terms of efficency, packaging, output, and emissions.
As an engineer you learn to do things the simplest way possible while maintaning the desired results to reduce costs and failures and that's what the LS* engines do. Simple designs executed to the highest technical degree to produce the highest output from any modern OHV engine.


[Modified by Formula, 5:28 AM 1/18/2004]

genemitc

Gentlemen: new member with some "piston head" experience. My question to our senior members is: with all the mods to the new C6 powerplant shouldn't we be realistically seeing more HP than 'just' 400? I know this is a delicate subject as MY 2004 closes but... BTW, I have one of these Pieces of Industrial Art on order here in southern Michigan and cant wait! Finally, can someone refer me to graphs of the HP/Torque curves for the old motor vs. the LS6? Duke,Hib? etc. :flag

WhiteDiamond

:iagree: Very well said.

I will throw this out there as well. I have owned a 5.4L Ford and I drive my Grandmother's 4.6L Ford across the country once and a while and the motors are unimpressive. The motor is HUGE and its specific output very small(without a SC). The gas milage is very poor on both the 4.6L and the 5.4L engine compared to any of my GM equipped vehicles. Our Escalade has a 6.0L LS based motor with 85 MORE horse/20ft/lb more torque than our 5.4L Expedition had and weighs within 200 lbs ot he Expedition. The Escalade gets 1.5mpg BETTER fuel economy and I drive it harder(since it has some ***** unlike the Ford did). My Grandmother has the 4.6L in a last of the big body Cougar. Ford should have left the old 302 in this vehicle, as the 4.6L is very disappointing in terms of everyday drivability and performance. It NEEDS a SC to make any power.

Todd

FAST LS1

Todd your experience shows that a broad power and torque range like the LS* based engines produces a much more user friendly powerband than that of the mod motors. When you have a broad power band with torque all over the place you can gear the car/truck wider for gas mileage while still maintaining the grunt needed to get you off the line and keeping performance.

Jimwood

I surrender. :D

Good Points.

SWCDuke

Looking at peak horsepower per cubic inch:

LS1- 350/346 = 1.01
LS6- 400/346 = 1.16
LS2- 400/364 = 1.10
LS7- (my estimate) 500/390 = 1.28

So the C6 base engine peak specific output is up almost ten percent from the C5 base engine and LS7 will see a similar 10 percent improvement over LS6, but LS2 makes more power below about 4500 than LS6 (due to the same peak torque that arrives 400 revs sooner), which is the rev range you will be in 99.99 percent of the time.

I don't think GM needs to offer any apologies for these improvements. They're significant, especially when you consider that fuel economy is as good if not marginally better, and the base price is only expected to increase about the same amount as in prior year C5s- just 2-3 percent to cover inflation. The product improvements, such as a higher output base engine, add value.

Go to http://www.gmpowertrain.com for a review current GM production engines. I doubt if LS2 is there yet, because it is not in production, and I'm not aware that GM has published full torque and power curves - just peak torque and power. Most listed engines include torque and power curves. Note the 80 percent torque bandwidths that you can eyeball off the torque curves.

I believe Dave Hill mentioned in the webcast that LS2 90 percent torque bandwidth is 2500 to about 6200. My estimate of LS2 torque bandwidth is 1200 to 6500 (if not beyond this limiting RPM) - same as LS1 on the bottom end, but the upper end is extended along with the redline.

Duke





[Modified by SWCDuke, 10:16 AM 1/18/2004]

SWEET LS1

That was well said and the truth. :lolg: :lolg: