Production of a Flat Plane Crank Engine
09-05-2015, 01:19 PM
#41
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St. Jude Donor '15
This is a good point, too. My friend has an '09 base Corvette 6M coupe with one option (paint color). So, 430hp and fairly low weight. Car be peppy. When he floors the loud peddle in first gear, his traction control just pulls its hair out. There's no way it can cope, and the car just slithers around while that poor yellow light on the dash strobes away. He would need a lot more tire to make proper use of his bone-stock LS3. On the other hand, my C4 GS coupe (less power, more tire) has no such problem. Floor it whenever/wherever in any gear and it just goes...with no drama.
My point is, that somewhere between '96 and '09, Corvettes crossed the line of diminishing returns that you alluded to. As you say, it's all about bragging rights now. Of course today's car is faster than my GS, but at what cost? Just look at what GM had to do to the car to try to make it work with the new LT4. It's so plastered with traction-generating aerodynamic "aids" that it's actually 20 mph slower than the now "obsolete" ZR1 (which was also a total handful). Even allowing for a little lunacy, the C6 ZO6 was probably as far as they should ever have gone with overdoing things, and it would have been a better balanced (performance/handling-wise) car with an LS3 rather than an LS7. Again, JMO...
My point is, that somewhere between '96 and '09, Corvettes crossed the line of diminishing returns that you alluded to. As you say, it's all about bragging rights now. Of course today's car is faster than my GS, but at what cost? Just look at what GM had to do to the car to try to make it work with the new LT4. It's so plastered with traction-generating aerodynamic "aids" that it's actually 20 mph slower than the now "obsolete" ZR1 (which was also a total handful). Even allowing for a little lunacy, the C6 ZO6 was probably as far as they should ever have gone with overdoing things, and it would have been a better balanced (performance/handling-wise) car with an LS3 rather than an LS7. Again, JMO...
I think Prius' are pretty competitive with that now. I understand 300hp is all YOU could ever want while driving to and from the car show, but please don't make that a blanket statement for the rest of us.
Further- the 'traction generating aerodynamic aids' have nothing to do with improving 0-60 times... they're about harnessing the inertia where the cars are most fun- somewhere that includes turning and braking. Magazine bench racing top speeds of the c7z06 to the c6zr1 is also silly as there are multiple factors in comparatively low top speeds of these great new cars- downforce, gearing, etc.
The 1970s and 80s were the single worst decades of car performance, think about that before bench marking it as the upper limits of tolerable performance.
09-07-2015, 08:29 PM
#42
Pro
Could not disagree more. In 1996 your C4 ran 0-60 in 4.7 and 1/4 mile in 13.3. Could you imagine how boring the performance market would be if we didn't evolve more?
I think Prius' are pretty competitive with that now. I understand 300hp is all YOU could ever want while driving to and from the car show, but please don't make that a blanket statement for the rest of us.
Further- the 'traction generating aerodynamic aids' have nothing to do with improving 0-60 times... they're about harnessing the inertia where the cars are most fun- somewhere that includes turning and braking. Magazine bench racing top speeds of the c7z06 to the c6zr1 is also silly as there are multiple factors in comparatively low top speeds of these great new cars- downforce, gearing, etc.
The 1970s and 80s were the single worst decades of car performance, think about that before bench marking it as the upper limits of tolerable performance.
I think Prius' are pretty competitive with that now. I understand 300hp is all YOU could ever want while driving to and from the car show, but please don't make that a blanket statement for the rest of us.
Further- the 'traction generating aerodynamic aids' have nothing to do with improving 0-60 times... they're about harnessing the inertia where the cars are most fun- somewhere that includes turning and braking. Magazine bench racing top speeds of the c7z06 to the c6zr1 is also silly as there are multiple factors in comparatively low top speeds of these great new cars- downforce, gearing, etc.
The 1970s and 80s were the single worst decades of car performance, think about that before bench marking it as the upper limits of tolerable performance.
"The 1970s and 80s were the single worst decades..." Those were two decades...and you missed my point. I realize that the performance envelope has expanded in the interim, but I stand by my original premise: my C4 GS is more enjoyable to drive than a C4 ZR-1, and is just a tick slower (on most road courses) because it's lighter and handles better. The current base C7/Z51, is a better-balanced, more enjoyable proposition than the C7 Z06 is...just as the C6 GS, and even the C6 Z06, are both better balanced, more enjoyable cars to drive fast than the ZR1 is. I never said development should've stopped in the eighties (where did that even come from?)...just that over-powered cars are for barroom braggarts, not true aficionados of well balanced dynamics. At the risk of committing sacrilege, just look at how 991 Porsches always seem to out perform their horsepower ratings on a road course, or even a drag strip. The reason is that they're not over-powered and they have excellent traction. More is not always better...unless more is an end in itself.
Last edited by 1analguy; 09-08-2015 at 01:47 AM.
09-08-2015, 02:00 AM
#44
Pro
Again, missing the point. The example of my '96 GS vs the C4 ZR-1 was just that...an example. Are we capable of moving on to a more modern example? Forget the C4. Forget the C6. Look at the C7...Z51 = better than Z06. Look at the Dodge Hellcat...SRT 392 = better than Hellcat. Get my point now? Balance beats excess...for me. Do whatever you feel you need to do to impress your friends, but at some point you're going to find that a truly balanced car will impress you more than the simple excess of too much power.
Last edited by 1analguy; 11-17-2015 at 01:25 PM.
09-14-2015, 11:14 PM
#45
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Production of a Flat Plane Crank Engine
Rumor is they are working on one code named LT7.
I think GM Powertrain is keeping options open between this and a Twin Turbo V8. No doubt the GT350 will be benchmarked as soon as GM can acquire one to test.
I think GM Powertrain is keeping options open between this and a Twin Turbo V8. No doubt the GT350 will be benchmarked as soon as GM can acquire one to test.
09-15-2015, 12:06 AM
#46
Safety Car
GM doesn't need to benchmark the GT350, there is nothing to learn in order to apply to the Corvette, except perhaps the cylinder liner technology. The Ford GT might give GM some thinking, but never the Mustang. A 2005 Ford Mondeo has more up to date technology that a 2015 Mustang. GM most definitely pulled apart a Mondeo, but I doubt they ever needed to pull apart a Mustang.
09-21-2015, 12:31 AM
#47
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Flat plane is best suited for high revving DOHC V8's. The pushrod design fits better in the Corvette as the heads don't need to be nearly as large.
Since pushrods and 2 valve per cylinder designs have their own issues with very high RPM operation it doesn't make much sense to go flat plane and add a bunch of vibration without benefit.
Since pushrods and 2 valve per cylinder designs have their own issues with very high RPM operation it doesn't make much sense to go flat plane and add a bunch of vibration without benefit.
09-21-2015, 04:29 AM
#48
Dohc engine, when made with belt instead chain, for who is not an home mechanic...is a big deal for the dealer...belt replacement every 100000 or less...
Chain in pushrod engine form is most reliable....
Also considering that
'91 alfa romeo 75 that was 2.0L and 150 hp and she made 24mpg highway a little bit better
Vs
'95 corvette that is 5,7L and 300 hp and she make 24 mpg
There's something that's sound strange
Chain in pushrod engine form is most reliable....
Also considering that
'91 alfa romeo 75 that was 2.0L and 150 hp and she made 24mpg highway a little bit better
Vs
'95 corvette that is 5,7L and 300 hp and she make 24 mpg
There's something that's sound strange
Last edited by Christi@n; 09-21-2015 at 04:45 AM.
09-21-2015, 07:26 PM
#49
Pro
It gets even stranger. I used to work in an O.E.M. engine factory. We made two different V6s. One was a 250hp 3.5L SOHC with belt-driven cams while the other was a 200hp 2.7L DOHC with chain-driven cams. They both had four valves per cylinder. Because the 2.7L had four cams and chain drive, it was larger, heavier, and 40% more expensive to make than the more powerful 3.5L with only two cams...yet due to marketing pressures, they had to sell the more-expensive-to-make 2.7L for less money than they charged for the optional 3.5L. That engine factory is now an empty field.
I was trying to make the point here that all that sexy complexity comes at a very high cost in bulk and mass...a cost almost always so high that the whole exercise isn't even worth the trouble, and that's leaving money out of it altogether!
I was trying to make the point here that all that sexy complexity comes at a very high cost in bulk and mass...a cost almost always so high that the whole exercise isn't even worth the trouble, and that's leaving money out of it altogether!
09-22-2015, 04:26 AM
#50
It gets even stranger. I used to work in an O.E.M. engine factory. We made two different V6s. One was a 250hp 3.5L SOHC with belt-driven cams while the other was a 200hp 2.7L DOHC with chain-driven cams. They both had four valves per cylinder. Because the 2.7L had four cams and chain drive, it was larger, heavier, and 40% more expensive to make than the more powerful 3.5L with only two cams...yet due to marketing pressures, they had to sell the more-expensive-to-make 2.7L for less money than they charged for the optional 3.5L. That engine factory is now an empty field.
I was trying to make the point here that all that sexy complexity comes at a very high cost in bulk and mass...a cost almost always so high that the whole exercise isn't even worth the trouble, and that's leaving money out of it altogether!
I was trying to make the point here that all that sexy complexity comes at a very high cost in bulk and mass...a cost almost always so high that the whole exercise isn't even worth the trouble, and that's leaving money out of it altogether!
Imo cars is U.S. are most realiable and maintenance is cheaper than european cars....
09-22-2015, 10:51 AM
#51
Pro
Compare that to the maintenance schedules/costs for 600+ hp European engines, and it just makes you laugh...
09-22-2015, 03:55 PM
#52
Absolutely! With GM's pushrod V8s, including their supercharged LS9s and LT4s, there is no internal engine maintenance...for the first 100,000 miles all you do is change the oil and filters! At 100,000 miles, you have to change the spark plugs...but then you just start changing the oil and filters again. At some point you'll have to change a water pump or timing chain, but those are reliable enough that they're not even on the maintenance schedule.
Compare that to the maintenance schedules/costs for 600+ hp European engines, and it just makes you laugh...
Compare that to the maintenance schedules/costs for 600+ hp European engines, and it just makes you laugh...
Yes i know i live in italy
Let me say: a fiat 500 some special version, but not so much can reach 25000€. Its ridicolous
09-25-2015, 10:47 AM
#53
Drifting
Of course it's a flat plane!
I just found out that I actually own a small displacement engine with a flat plane crank. It's the 2.0L Diesel in my DD '11 Golf! I was cruising through the tech papers for the engine and saw a photo of the flat crank. WTH? This engine's hp peak is 4000rpm, and it feels like it's done pulling somewhere between 3000-3500rpm. What was their logic? My guess would have been added stiffness, but no, their claim was weight savings ("only four counter weights"). The problem with that is that they then were forced to add two gear-driven balance shafts (that run in the sump under the crank) in order to compensate for the lack of crank balance. And those added gears/shafts/etc. are still rotating torsional mass, so in the end, where are all the net mass savings? They cannot be substantial, and now the engine is quite a bit more complex and expensive to manufacture.
I think sometimes design engineers may be out-clevering themselves when they adopt theoretically-tantalizing "technologies" without fully taking into account all of the long-range consequences of their actions. But hey, what do I know?
I think sometimes design engineers may be out-clevering themselves when they adopt theoretically-tantalizing "technologies" without fully taking into account all of the long-range consequences of their actions. But hey, what do I know?
Regards from Down Under.
aussiejohn
09-26-2015, 09:12 AM
#55
Melting Slicks
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To replace the TVS supercharger with turbos in that tight engine bay there is only one way to go, UP. Turbos of the size needed to increase output past 650 hp will be so enormous in the vee of the engine that you won't be able to see where you are driving. With TVS, GM can raise the hood an inch or two to fit larger blowers. Perhaps they'll go the Callaway route and screw the European pedestrian safety laws. After all, how many LT7s would Europe buy? 2?
GM doesn't need to benchmark the GT350, there is nothing to learn in order to apply to the Corvette, except perhaps the cylinder liner technology. The Ford GT might give GM some thinking, but never the Mustang. A 2005 Ford Mondeo has more up to date technology that a 2015 Mustang. GM most definitely pulled apart a Mondeo, but I doubt they ever needed to pull apart a Mustang.
GM doesn't need to benchmark the GT350, there is nothing to learn in order to apply to the Corvette, except perhaps the cylinder liner technology. The Ford GT might give GM some thinking, but never the Mustang. A 2005 Ford Mondeo has more up to date technology that a 2015 Mustang. GM most definitely pulled apart a Mondeo, but I doubt they ever needed to pull apart a Mustang.
10-16-2015, 07:29 PM
#56
Neat question. The Ford engine has equal output compared to the base Audi V10 which is also a 5.2L. The cost is likely only half of what it costs Audi to make one. In a pushrod design it's probably even cheaper than the DOHC V8.
It would also keep up the compactness of the pushrod orientation while increasing output. This is typically the small block ideology, a good packaging job.
It would also keep up the compactness of the pushrod orientation while increasing output. This is typically the small block ideology, a good packaging job.
10-17-2015, 08:27 AM
#58
10-19-2015, 02:15 PM
#59
Team Owner
Pro Mechanic
By the way, cross-plane cranks "rob power" only to the extent that they limit ultimate rpm. The even firing pattern that they provide actually makes power tuning much easier. The uneven firing order of a flat-plane crank can induce all manner of air flow weirdness in a single-plenum-based intake system.
Last edited by Tom400CFI; 10-19-2015 at 02:25 PM.
10-19-2015, 02:16 PM
#60
Team Owner
Pro Mechanic
That is correct.The 4 cylinder can not benefit from a cross plane design. The V8 can, b/c the counterweight for one piston can and does weigh about equal to the weight of the piston and rod. THIS mass, when 90* to the motion of the piston (1/2 way up or down the stroke) is cancelled by the adjacent piston that is attached to the same crank pin. This very feature is what makes the "cross plane" V8 so smooth and desireable.
On any inline engine, a crank weight equal to the weight of the piston/rod would cancel vibrations in the vertical plane, but introduce vibrations laterally with equal magnitude as those vibrations created vertically, that we are trying to cancel. It would shake and introduce as much crank stress, as the same engine w/NO counterweights! SO, typically, the counter weights of an inline are ~1/2 the weight of the piston and rod -it cuts vertical vibration in 1/2, and only adds 1/2 laterally (some of which is cancelled by other cylinders' throws, depending on the number of cylinders.
Last edited by Tom400CFI; 10-19-2015 at 02:24 PM.