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Old 01-22-2013, 11:45 AM   #41
Kratos-TM
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If you had an exoskeleton like the ant does, maybe you could!
Click the image to open in full size.


Iron Man is baaaadaaaaaazzzzzz....
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Old 01-22-2013, 11:58 AM   #42
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Agree that HP/liter displacement is useless. 1) Europeans and Japanese are taxed based in part on their car's engine displacement, so for them, it is much more important to limit the displacement. It has nothing to do with performance - it's all about the taxes.

2) More complex does not equal mo' better. What it equals is weight. When I order an LS1 head from Summit or Jegs, the shipping weight is 22 lbs. Know what the shipping weight is on a Honda dohc head? Not counting the cams, it ships at 64 lbs.

This is a pretty ridiculous comment. Order a small block chevy block vs honda block. It's the nature of the design...comparing shipping weights is foolishness.



A much more pertinent measurement for us would be horsepower per pound of engine weight. GM pointed that out already. Or horsepower per volume. Not displacement, but the total volume the engine takes up.


This is an interesting way of looking at it. It's a different look at true "volumetric efficiency". An F20C is half the size though, so I don't think that changes much. Total engine volume still can only achieve a given displacement, as dictated by bore diameter and stroke. Those two factors still dictate the overall size of the block.

The only variation with the single cam LSx type engine versus dohc design comes down to the head size. Plus you say DOHC is "more complex" but I beg to differ. DOHC use direct cam actuated rockers, which act directly on the valve stem. The Corvette engine design uses cam>lifter>pushrod>rocker>valve...and redirects the energy in the process.

Honestly, I really don't think from an efficiency/reliability standpoint that you can debate DOHC multivalve arrangements vs the sbc design. If you look at racing, you just don't see pushrod motors, unless it's in traditional based, very rule restricted, american forms of racing.

Look at P1 classes or F1...places where there are no limitations in how you create you're power plant...there are no pushrods.

Let's also not forget about one of the most iconic Corvette engines ever to date...the LT5. Using outside consultation to break the barriers of hp in an EPA restricted era, you got DOHC's and variable induction technology...used by Japanese manufacturers and implemented by Lotus.
So that's that...
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Old 01-22-2013, 12:00 PM   #43
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Take the LT1, bore & stroke it; throw in some forged titanium connecting rods & titanium intake valves, bump up the cam a touch & mess with the ECU some; then we just might see that 552.8hp & GM might end up calling it a Z07…
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Old 01-22-2013, 12:01 PM   #44
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I need 600 for Z06/7
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Old 01-22-2013, 12:06 PM   #45
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I need 600 for Z06/7
Sorry, that is reserved for the LT4 (LT1 + supercharger…?) engine & the ZR1 designation…

But please, PLEASE…!!! GM, lose the Plexi window on the hood…!
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Old 01-22-2013, 12:07 PM   #46
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Take the LT1, bore & stroke it; throw in some forged titanium connecting rods & titanium intake valves, bump up the cam a touch & mess with the ECU some; then we just might see that 552.8hp & GM might end up calling it a Z07…
Did that to my lt1 and I got 614 hp out of 5.9L


To get 600 with variable valve timing and a much newer tech engine will be easy. Of course meeting all the strict regulations and fuel economy numbers too.
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Old 01-22-2013, 12:09 PM   #47
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That's making the assumption that LT4 is not Z07

LT4 in a ZR1 doesn't work...it has to be LT5. I say ZR1 is going to be twin turbo based on various info saying indirectly that GM is working on anti-lag with the new ecu. With all this throwback crap though...there's NO way ZR1 doesn't get an LT5 designation...it would be sacrilig...
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Old 01-22-2013, 12:34 PM   #48
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The only variation with the single cam LSx type engine versus dohc design comes down to the head size. Plus you say DOHC is "more complex" but I beg to differ. DOHC use direct cam actuated rockers, which act directly on the valve stem. The Corvette engine design uses cam>lifter>pushrod>rocker>valve...and redirects the energy in the process.
Have you ever taken apart a SOHC or DOHC engine? They are much more complex. You're only looking at the camshafts that actuate the valves. This excludes all of the gears, chains/belts, and tensioners that complete the system. I've worked on both. The OHV design is FAR simpler and easier to modify and maintain.

There are many reasons why one design is used over another. The truth is both OHC and OHV designs are fairly old. The future is NO cam and something like solenoids actuating the valves.
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Old 01-22-2013, 12:57 PM   #49
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Higher displacement engines with a single cam/two-valve configurations can never match the horsepower output when compared with smaller displacement multi-cammed/multi-valved engines. Look at motorcycle engines that develop more than two hundred horsepower with just over a liter of displacement.....their technology have alway be in the forefront of engine design. It is unfortunate that GM still holds on to old technology that has long been looked upon as flawed by the rest of the engineering world. The Corvette should have adopted a DOHC power plant mounted behind the passenger compartment, not to copy the rest of the high performance world, but to advance an American designed sports car that is truly on par with anything anywhere. The price would surely be more than $60,000....unfortunatley.
Your view is completely antiquated. Welcome to the 80s. Output/displacement is totally irrelevent unless you pay taxes on the latter. What matters is engine weight, physical packaging, and fuel efficiency. The fact is that the GM 2-valve engines blow the competition away in every respect. The engines are on average 100lb lighter, package physically as if they had 2 fewer cylinders, and have better fuel economy than any multivalve engine of similar output. That in turn is why a C6 Z06 can lap Laguna Seca faster than a Ferrari 458 Italia or any Porsche.

It is technologically a superior solution, period.

Last edited by TTRotary; 01-22-2013 at 01:00 PM.
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Old 01-22-2013, 01:30 PM   #50
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Originally Posted by Ford John View Post
Cadillac ATS:
naturally aspirated 3.6-liter V6 gasoline
engine that produces 321 horsepower
Direct Injection .... all same engine technology as LT1 C7

Thus
321 (hp)/3.6 (liters)
89.16 hp/liter

Corvette C7 LT1
450 hp/6.2 Liter
72.58 hp/Liter

sooo
6.2L x 89.16 hp= 552.8 HP May this be future???
without the supercharger???
I think your right, the car is massively underrated.
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Old 01-22-2013, 05:01 PM   #51
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Even though my 7100 RPM OHV pushrod V8 is a 2009 model, the exact same engine can be found in a 2013 model. Is that recent enough for you?
I been checking some things out about your car. Interesting it is capable of 1-2 tenths more then the ZR1 off the line, and 0-60 in 3.5s. Significant when you consider how close it is to the C7 in power. If you read this MT article they only made 3.8s because they ran the 1/4 mile and 0-60 together and didn't want to hit the rev limiter. With the goodyears and 7000RPM it should be good for 61.1MPH, MPSC 60.9 and new MPSS 60.2. The MPSCs at 7100 or 7099RPM would be good for 61.7. Too close still?

A caveat on that acceleration run: Our associate road test editor claims our time could have been as low as 3.5 seconds if it weren't for gearing that places 60 mph right at the top of first. Shifting at 60 mph often involved bumping the rev-limiter before the 1-2 upshift, resulting in lower quarter-mile acceleration times. We opted to optimize quarter-mile runs at the expense of a slightly slower 0-60-mph sprint.

Read more: http://www.motortrend.com/roadtests/...#ixzz2IkChg2eq


Last edited by johnglenntwo; 01-22-2013 at 05:03 PM.
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Old 01-22-2013, 05:39 PM   #52
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Originally Posted by johnglenntwo View Post

A caveat on that acceleration run: Our associate road test editor claims our time could have been as low as 3.5 seconds if it weren't for gearing that places 60 mph right at the top of first. Shifting at 60 mph often involved bumping the rev-limiter before the 1-2 upshift, resulting in lower quarter-mile acceleration times. We opted to optimize quarter-mile runs at the expense of a slightly slower 0-60-mph sprint.

Read more: http://www.motortrend.com/roadtests/...#ixzz2IkChg2eq

The perfect example of how companies need to cater to the dumbies. Gotta build a car that does 0-60 in a certain time...when 0-60 is a poor form of measurement for todays cars, just so the bandwagoners and simpletons can talk numbers.

That's all that matters anymore...0-60 and what hp number is on the fender badge....what really matters, doesn't matter to most.
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Old 01-22-2013, 05:44 PM   #53
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There are many reasons why one design is used over another. The truth is both OHC and OHV designs are fairly old. The future is NO cam and something like solenoids actuating the valves.
And this will lead to a whole different conversation of ramp rates/valve opening rates matching piston speeds. People from the sbc/pushrod world aren't opened to such conversation generally. I think we, as a pretty pioneering people, can always improve on anything, but there comes a question...when do you stop? Had we continued to develop piston powered prop driven fighter planes, imagine what we could have by now in comparison to WWII...but pursuing other technologies led to far greater things. If people can't let go...you can't go forward.

Pneumatic actuation of valves has been used for some time. Questionable if we'll ever see it on the street. If we did it would be from a Japanese automaker...guarantee it.
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Old 01-22-2013, 08:00 PM   #54
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The perfect example of how companies need to cater to the dumbies. Gotta build a car that does 0-60 in a certain time...when 0-60 is a poor form of measurement for todays cars, just so the bandwagoners and simpletons can talk numbers.

That's all that matters anymore...0-60 and what hp number is on the fender badge....what really matters, doesn't matter to most.
http://www.motortrend.com/roadtests/...son/specs.html

One can see these data side by side and make certain deductions. IE The 3.8L Porsche has a 0-60 4 tenths faster then the 6.2L Vette. Why?
Higher compression, rear engine.... Without direct comparison we are clueless!

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Old 01-22-2013, 09:45 PM   #55
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Originally Posted by Ford John View Post
Cadillac ATS:
naturally aspirated 3.6-liter V6 gasoline
engine that produces 321 horsepower
Direct Injection .... all same engine technology as LT1 C7

Thus
321 (hp)/3.6 (liters)
89.16 hp/liter

Corvette C7 LT1
450 hp/6.2 Liter
72.58 hp/Liter

sooo
6.2L x 89.16 hp= 552.8 HP May this be future???
without the supercharger???
552 hp is possible with a much more radical cam (assuming still N/A), but with that cam it probably would not meet mandated emissions requirements.

Four valves/cylinder vs. two valves/cylinder is an apples to oranges comparison, as someone else stated. Four valves/cylinder provides higher volumetic efficiency (VE). Given the same cam lift/duration, etc., a four valve cylinder head will provide greater VE, and thus more hp, assuming all other things being equal.

The beauty of the GM small block is that, by using an internal cam and push rods, they can keep the engine light weight and compact. But don't expect the same hp/displacement ratio as an equivalently high tech four valve/cyl. DOHC motor. Instead, what you get is a great hp/wieght and hp/volume motor, volume meaning the overall space the motor takes up under the hood.

With a DOHC motor, they certainly can achive 552 hp and meet emissions requirements, but then it would not fit under the C7 hood. It would be too tall. It might weigh more as well, but as someone else pointed out in another thread, Mercedes has a DOHC 6.2L V8 about the same weight as the LT1 and that outputs more hp. Still, that motor probably would be too tall for the C7 hoodline.

Last edited by C7ZR1forT; 01-22-2013 at 11:18 PM.
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Old 01-22-2013, 09:53 PM   #56
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Originally Posted by johnglenntwo View Post
http://www.motortrend.com/roadtests/...son/specs.html

One can see these data side by side and make certain deductions. IE The 3.8L Porsche has a 0-60 4 tenths faster then the 6.2L Vette. Why?
Higher compression, rear engine.... Without direct comparison we are clueless!

The 911 is rear engine. Much more of the overall vehicle weight is sitting over/aft of the rear tires. In other words, the 911 has much better rear wheel traction... The Corvette, being 50/50 weight balanced, is great for the road coarse, but absent drag tires, is traction limited for straight out accelleration. The GTR overcomes this using AWD, but mention AWD in this forum and you will be sure to stir up controversy.

Also, the 911 uses a much faster shifting transmission than the Corvette and shorter gear ratios. The Corvette (at least the C6) is designed to get the best 0-60 time in first gear alone to avoid the 1st to 2nd shift delay. So, first gear is very tall. If GM were to put shorter 1st and 2nd gears with an extremely fast shifting DCT transmission, that would help acceleration from a dead stop, assuming there was adequate rear wheel traction. The issue is cost. GM is trying to keep the price of the Corvette at a certain price point. I think a DCT transmission would be too expensive for their price target. Hopefully GM will provide a DCT option with shorter first and second gears (and much improved traction out of the hole) on future higher priced models, but I won't hold my breath.

For now, if you want the best straight line accelleration from a dead stop, get a GTR or 911 turbo, both of which have admirable road course performance, but are pricey. If you want an all around great vehicle and great road course performer, at a relatively low price, get a Corvette.

Last edited by C7ZR1forT; 01-22-2013 at 10:55 PM.
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Old 01-22-2013, 10:02 PM   #57
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First of all, comparing hp/liter of a v8 vs a v6 or any engine with a lesser number of cylinders is absurd. The additional reciprocating mass comes into the equation, and it is not a linear relationship.

Second, try fitting a DOHC v8 under the hood of a c7. It aint gonna happen without blocking half of your windshield.

Third, the in-block cam design lowers the CG of the car and provides a much lighter engine. It is also more reliable due to less moving parts. If DOHC was the way to go, then that's what they would have done.

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Old 01-22-2013, 10:53 PM   #58
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Bahh....debating engine dynamics with internet people who haven't developed/built engines beyond aftermarket head/cam/piston motors...wears me down.

I'm out...
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Old 01-24-2013, 02:52 PM   #59
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Bahh....debating engine dynamics with internet people who haven't developed/built engines beyond aftermarket head/cam/piston motors...wears me down. I'm out...
It may surprise you to hear that, as far as the rest of us on here are concerned (that being the whole universe of the Corvetteforum excepting you), you are also... just another internet guy. Too funny.
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Old 01-24-2013, 03:27 PM   #60
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The 911 is rear engine. Much more of the overall vehicle weight is sitting over/aft of the rear tires. In other words, the 911 has much better rear wheel traction... The Corvette, being 50/50 weight balanced, is great for the road coarse, but absent drag tires, is traction limited for straight out accelleration. The GTR overcomes this using AWD, but mention AWD in this forum and you will be sure to stir up controversy.

Also, the 911 uses a much faster shifting transmission than the Corvette and shorter gear ratios. The Corvette (at least the C6) is designed to get the best 0-60 time in first gear alone to avoid the 1st to 2nd shift delay. So, first gear is very tall. If GM were to put shorter 1st and 2nd gears with an extremely fast shifting DCT transmission, that would help acceleration from a dead stop, assuming there was adequate rear wheel traction. The issue is cost. GM is trying to keep the price of the Corvette at a certain price point. I think a DCT transmission would be too expensive for their price target. Hopefully GM will provide a DCT option with shorter first and second gears (and much improved traction out of the hole) on future higher priced models, but I won't hold my breath.

For now, if you want the best straight line accelleration from a dead stop, get a GTR or 911 turbo, both of which have admirable road course performance, but are pricey. If you want an all around great vehicle and great road course performer, at a relatively low price, get a Corvette.
Sorry, but you are wrong on your "facts". The C6 was not designed to hit 60 MPH without shifting, except in the $80,000 Z06 and the 427 Convertible and the $125,000 ZR1.

The LS3 in the base coupe will redline at 56 MPH and the LS3 in the Grand Sport will redline at 50 MPH. On both versions of the C6, the only way you will see 60 MPH is in second gear.

But you will notice, the base C6 does 0-60(and shifting gears at 56 MPH) in 4.2 seconds, whereas the GS LS3 does 0-60(and shifting gears at 50 MPH) in 3.95 seconds. It's because of the lower gearing in the GS, not because it doesn't have to shift gears before hitting 60 MPH.

For the LS7 cars, its the 7000 RPM redline that allows them to hit 60 MPH in 3.7 seconds without shifting and the LS9 gets to 60 MPH in 3.4 seconds without shifting because of it's tall 2.29 first gear. But the LS9 does not need the shorter gearing found in the base C6 and GS because of it's outrageous torque from the PD supercharger.
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