04-12-2011, 12:52 PM | #29 | ||||
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04-12-2011, 01:31 PM | #30 | |
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04-12-2011, 01:38 PM | #31 | |
I am the internets.
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04-12-2011, 02:04 PM | #32 |
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Doing some research says we dont see a C7 until 2013 model year so still 2014 model year for Camaro wich most likely means alpha platform to help meet Cafe standards
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04-12-2011, 03:00 PM | #33 |
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Your "theory" here is based on all-out rpm/racing...which ISN'T the stated purpose, day-in and day-out of ANY regular production engine...especially with design features and technology necessary for TRUCKS, the overwhelming volume-required use for this architecture.
Cylinder head tech. will be slanted, generally, to TORQUE as opposed to HP...where velocity is most important. Think "small port" vs. "large port"... Small for trucks and "regular" passenger requirements with low- and mid-range usage (generally), large(r) for performance applications. Emissions and fuel economy will be at least as important as all-out rpm/power. And at lower speeds, TORQUE moves the "load". More torque, less pedal...less emissions...less fuel consumption. And THAT'S where VVT (regardless of methods used) will have its every-day applications. Performance applications? Time the VVT, and design the cylinder heads, accordingly. With 7- and 8-speed trannies for both emissions and CAFE compliance at part-throttle. BTW, contact LPE or Katech and request 3.8" worth of valves in your 3.98" bore LS1...ain't gonna happen... ...and all other things being equal, which they never are, an over-square engine (bigger bore than stroke) will out-rev an under square one (stroke bigger than bore) every time. Compare the characteristics of a 302 (Z/28) to a 307 long-stroke... Bore makes rpm, stroke makes torque. |
04-12-2011, 03:13 PM | #34 |
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A huge factor here would be the valve sizes, what would be the point of increasing the RPM's of an OHV pushrod engine if the valve sized limited the airflow beyond 7000rpm's. I had a square bore and stroke 5.739 liter (350.17 cubic inch) engine laid out for fun and nostalgia. I went with a 3.81 bore and a 3.84 stroke but that would greatly reduce the size of the valves. The old Chevy 350 had a 4.0 inch bore and a 3.48 inch stroke, it is becoming more obvious that GM will maintain a 4.00 inch bore just to accommodate larger valves. So, for nostalgia’s sake, a Gen V 5.7 liter V8, using the LS7's 4.125 bore (which is likely and would be a good move if you asked me). We could make a 5.7/350 with a 4.125 bore and a 3.27 stroke (5.728 liter/349.53 ci), and could go up to a 3.279 stroke for a maximum 5.744 liter/350.49 liter). That would allow for HUGE valves 2.20i and 1.61e and would be more than enough valve area to allow deep breathing at high RPM. They will probably share the 12 degree valve angle and would help with the valve shrouding. Valve shrouding is usually a problem for OHC's and OHV's that use huge valves. Angling the valves provides more room between the valve and the cylinder wall, angling too much is not good either but most engineers have found a happy medium between cylinder wall shrouding and maintaining a flat valve area.
But... a 5.7 might defeat the whole purpose of having a global block design. GM would typically like to cover a wide range of applications with a global block. I heard before that a 5.3 and a 6.2 would be offered. That would be a very nice range of applications. The 5.3 would be for entry level sports coupes/cars, lightweight trucks and light-medium sedans. The 6.2 would cover the remaining high level sport coupe/cars, medium-heavy trucks and large sedans. Using a 5.7 would be right in the middle of that range. Think about the GT500's 5.4 in the middle of the 5.0 and 6.2. The only thing different about that situation is that the 5.0, 5.4 and 6.2 are two completely different engines, therefore... one of them are about to "terminated" (pun). GM could cover a 5.3, 5.7 and 6.2 and a fraction of the cost in which Ford does it, the DOHC 6.2 is just way to big to be a sports car engine and a 5.4 replacement will be coming very shortly. So, a 6.2 carries a 4.065 bore and 3.622 stroke (375.98 ci/6.1623 liter) although it would be even closer as far as valve size though. If we could use the LS7's 4.125 bore to achieve a 6.2, we could use a 3.513 (375.51ci/6.154 liters) to 3.522 (376.47ci/6.170 liter). That would give us enough room for the large valves that would be optimal for high RPM deep breathing. Just some free writing here... |
04-12-2011, 04:14 PM | #35 |
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You're confusing valve size with port size...
You can have a 2.20" intake valve, oversized in a small-port head, where a 2.00" was (theoretically), but it may not flow much more and/or make much more usable power. Made of the same materials, the 2.20 may not rev to the same limits as the 2.00. In fact, a 2.00's revability may allow the engine to make MORE power than the 2.20 might achieve. Taken in the other direction, if you increase port size to flow more (to accommodate the bigger valve), you may in fact decrease port velocity at part-throttle, thereby disturbing the intake mixture to a less-than-ideal combustible state and dropping power while increasing emissions...less efficiency can be the result, caused by lower port velocity. What works great at 7,000 rpm may be terrible at 2,500...even with VVT... Ford learned this many years' back with their street-version Cleveland heads...the smaller-port 2V heads were preferred for the street over 4V or BOSS versions..."port velocity"... The same lessons learned by Chev with "peanut port" Big Block heads vs. large-port versions in less-than all-out, steetable set-ups. Again, what works at the track does NOT necessarily translate "inch-for-inch" on non-track engines that you'll see coming out of Oshawa or Bowling Green on production line-built engines/vehicles... The Gen-V version will ultimately have several head-port, valve-size configurations available (just as LS-versions have now), but extreme port-valve combos will not likely be assembly-line available. As with the LS and other SBC versions, the Aftermarket will provide many answers GM can't/won't offer. Remember, CAFE '16 approaches... |
04-12-2011, 04:16 PM | #36 | |||||
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Very good conversation by the way.... |
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04-12-2011, 04:19 PM | #37 | |
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04-12-2011, 04:34 PM | #38 |
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You can change valve timing with VVT. But you have to "optimize" valve SIZE to "port dimensions"...which are predicated by overall volumetric efficiency and port velocity at a given rpm. What, therefore, is our intended rpm range? Knowing, of course, that what's ideal at off-idle and low/mid-range will NOT be "ideal" at high(er) rpm...and the REVERSE is true, too.
Unless/until someone finds a relatively inexpensive way of varying engine displacement and/or port size (length AND cross-section) while the engine operates, all the pertinent factors required to make a streetable engine efficient at ALL engine speeds is a compromise... |
04-12-2011, 04:45 PM | #39 | |
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As for a Z/28 coming from Oshawa with a "race engine" in it, "I don't think so, Tim..." Emissions-compliant, and CAFE-friendly, my friend. |
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04-12-2011, 05:40 PM | #40 |
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Sorry for the late reply, I was locked into a technical discussion but, I think the time frame that most insist on is correct. I believe GM said that the C7 would be out in model year 2013, so calendar year 2012 is when we will see both the C7 and the Gen V engine at shows. Camaro fans should be praying for GM to break the usual route, as in Corvette/Camaro leap frog. A simultaneous C7/Z28 release would really draw some attention in the summer of 2012. Will GM break tradition? This would be the first time (that I know of) that GM played both aces.
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04-12-2011, 05:54 PM | #41 | |
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1. At what point in the year those changes were made? Was it a mid-model update? 2. How long was the Corvette offered with the engine prior to the Camaro receiving the sudden change. 3. What was the sales and performance situation compared to the competition before the updates? 4. The engine offering before the change and the performance gained after the fact. 5. What were the physical changes to the engine, were the changes improvement to the current design? (LS1>LS2>LS3) or was it a new engine altogether (LT5) 6. Where was the Camaro at in its model life when this/these mid-model year drivetrain upgrade(s) occurred? Just trying to see if there are any circumstantial coincidences that maybe could indicate an action like that in the future. Sorry for the late reply by the way and thanks for reading man... |
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04-12-2011, 06:32 PM | #42 | |
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First let me get these Boss 302 measurements up (nearly square) Bore: 3.629 inches Stroke: 3.649 inches Our 350 has a 3.27 to 3.279 stroke and that's where our RPM's are coming from. I need to figure out a way to paper calculate peak horsepower and torque. I would have to guesstimate a compression ratio (going to go with 11:1) and cylinder head volume (the LS7's 70cc and work down from there)... I would actually need quite a few measurements to be honest. Isn't there a guy on here that has a computer program that can run performance simulations with some of those measurements? The Hot Rod PC guy. Edit: A quick calculation based on a 4.125x3.27 and 70cc heads gives me a 10.22:1 compression ratio. Using the max stroke of 3.279 gives me a 10.25:1 compression ratio. I need to look into head gaskets and pistons/rings now. LOL!!! I'm working with a paper thin gasket at the moment, I will need to make up the lost compression with a thicker gasket with the piston/ring setup. Last edited by thePill; 04-13-2011 at 01:38 AM. |
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