I hope the C7Z isn't turdboed
09-07-2013, 11:41 PM
#41
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To all the guys talking about heatsoaking being a problem... do you have any real life examples with datalogs showing increasing temperature? Thats what CAIs and intercoolers are for.
I have datalogs of my Evo X not showing any increase in temperature at all during track time ( the difference between IAT and MAT stayed the same all along)
About lag... you just keep your car in the right RPM range and you wont have any issues specially with V8s and small factory turbos.
Also a turb'ed Vette would mean a car with HUGE potential for crazy whp numbers. Why do you think AMS only works with turbo'ed cars?
I have datalogs of my Evo X not showing any increase in temperature at all during track time ( the difference between IAT and MAT stayed the same all along)
About lag... you just keep your car in the right RPM range and you wont have any issues specially with V8s and small factory turbos.
Also a turb'ed Vette would mean a car with HUGE potential for crazy whp numbers. Why do you think AMS only works with turbo'ed cars?
Last edited by EvoXvette; 09-07-2013 at 11:45 PM.
09-07-2013, 11:42 PM
#42
Drifting
They are apples to Orange engine designs no doubt. I'm an engineer, I understand that very well.
The biggest factor here is a 2.5 liter displacement difference. The LS7 technology is 9 years old.
But with MORE displacement, its still under the 4.5's power? Much more displacement, but less tech, should average out shouldn't it? The ls7 is simplistic, but uses high end parts to do what it does, parts that wont even fit on most lsX based motors.
We have crate motors that are NA and make over 600 horsepower that use a carburetor and are OHV designs.
And would not meet mass, production car standards. The high output lsX454 makes an estimated 580hp/600lb-ft via fuel injection. The ls series are very fuel efficient, but none the less, the bigger is it, the more gas it eats, as demonstrated by z06 mpg vs base mpg. A 454 would lower the mpg another point or two.
You can't tell me that 600hp is a hard goal to reach with technology in a 7 liter engine and do it reliably.
The ls2 made 400hp. It didn't just take simply 1.0 more liter to make 500hp. It took a unique port design, unique intake, serious valvetrain/rotating assembly parts, and(sort of) more rpms.
Here's how you do it:
Compression goes to 12:1, direct injection, better head and valve flow, slightly more aggressive cam profile with vvt for proper idle characteristics and high end power, 7500rpm.
I personally think the lt1's compression ratio is rather low, even for a "mass production" engine. 11-1 ratio isn't uncommon anymore, and they only made it 11.5-1 with direct injection. Granted they are more extreme engines, but the Carrera S is 12.5, 458 is 12.5, and upcoming GT3 is 12.9. So I do agree 12-1 MINIMUM should be incredibly easy to maintain on a specialty motor.
Agreed cam/timing should also be top end/hp biased, it would be 7.0L, it doesn't need help making low-end torque.
Better air flow... that's increasingly tough. The ls7 used ***** to the wall production 2v heads. It's not that they cant be increased, but when do you reach a(production motor) limit that 1 intake valve can support NA while still being able to rev past 6000. 2 valves, 3/4 the size of one big valve, are just better. Orrrrrr, as the CAD drawing showed, maybe they realize they hit that limit, and with forced induction it doesn't matter nearly as much. Think about it, when's the last time you saw a 03/04 cobra, GT500, zr1, GTR, or ZL1 with modified heads. You do everything in the book first, THEN if you are going for extreme numbers, you touch the heads on forced induction cars.
7500rpms? The ls7 makes peak power at 6300, and look at what they had to do to get the highest revving production pushrod motor. Supposedly testing including revving it to 8000rpms. So while the rpm limit isn't insurmountable, carrying power that high in the rev's probably is. The only pushrod motor with peak power higher then the ls7? ls9, there's that forced induction again.
That's not even a hard thing to conceptualize or execute for the level of engineering that GM has.
I dunno, look how much work the ls7 was vs the lsA which surpasses it at most rpms, but costs the same, or maybe even less, and that's only because of the additional supercharger. Lutz even said before, had it not been for the introduction of the TVS, they probably wouldn't have even attempted a ZR1. The first test mule was turbo, then super. They hit there limits then, and due to the government(outrageously) increased EPA restrictions they may still be on the fence
The biggest factor here is a 2.5 liter displacement difference. The LS7 technology is 9 years old.
But with MORE displacement, its still under the 4.5's power? Much more displacement, but less tech, should average out shouldn't it? The ls7 is simplistic, but uses high end parts to do what it does, parts that wont even fit on most lsX based motors.
We have crate motors that are NA and make over 600 horsepower that use a carburetor and are OHV designs.
And would not meet mass, production car standards. The high output lsX454 makes an estimated 580hp/600lb-ft via fuel injection. The ls series are very fuel efficient, but none the less, the bigger is it, the more gas it eats, as demonstrated by z06 mpg vs base mpg. A 454 would lower the mpg another point or two.
You can't tell me that 600hp is a hard goal to reach with technology in a 7 liter engine and do it reliably.
The ls2 made 400hp. It didn't just take simply 1.0 more liter to make 500hp. It took a unique port design, unique intake, serious valvetrain/rotating assembly parts, and(sort of) more rpms.
Here's how you do it:
Compression goes to 12:1, direct injection, better head and valve flow, slightly more aggressive cam profile with vvt for proper idle characteristics and high end power, 7500rpm.
I personally think the lt1's compression ratio is rather low, even for a "mass production" engine. 11-1 ratio isn't uncommon anymore, and they only made it 11.5-1 with direct injection. Granted they are more extreme engines, but the Carrera S is 12.5, 458 is 12.5, and upcoming GT3 is 12.9. So I do agree 12-1 MINIMUM should be incredibly easy to maintain on a specialty motor.
Agreed cam/timing should also be top end/hp biased, it would be 7.0L, it doesn't need help making low-end torque.
Better air flow... that's increasingly tough. The ls7 used ***** to the wall production 2v heads. It's not that they cant be increased, but when do you reach a(production motor) limit that 1 intake valve can support NA while still being able to rev past 6000. 2 valves, 3/4 the size of one big valve, are just better. Orrrrrr, as the CAD drawing showed, maybe they realize they hit that limit, and with forced induction it doesn't matter nearly as much. Think about it, when's the last time you saw a 03/04 cobra, GT500, zr1, GTR, or ZL1 with modified heads. You do everything in the book first, THEN if you are going for extreme numbers, you touch the heads on forced induction cars.
7500rpms? The ls7 makes peak power at 6300, and look at what they had to do to get the highest revving production pushrod motor. Supposedly testing including revving it to 8000rpms. So while the rpm limit isn't insurmountable, carrying power that high in the rev's probably is. The only pushrod motor with peak power higher then the ls7? ls9, there's that forced induction again.
That's not even a hard thing to conceptualize or execute for the level of engineering that GM has.
I dunno, look how much work the ls7 was vs the lsA which surpasses it at most rpms, but costs the same, or maybe even less, and that's only because of the additional supercharger. Lutz even said before, had it not been for the introduction of the TVS, they probably wouldn't have even attempted a ZR1. The first test mule was turbo, then super. They hit there limits then, and due to the government(outrageously) increased EPA restrictions they may still be on the fence
09-07-2013, 11:54 PM
#43
Like I said earlier in the thread, it's a 100% guarantee we will have a forced induction car.
People doubting that a 7 liter LS couldn't make 600hp naturally aspirated in a production vehicle with cutting edge technology is just naysaying and ignorant.
I know a flat plane V8, dohc Ferrari engine is completely different, but if Ferrari built a 7 liter V8 it would make close to 800 horsepower with equivalent tuning to the Speciale.
GM can get 75% of that easily.
I also didn't mean to imply that 7500rpm would be it's peak power, but its redline.
People doubting that a 7 liter LS couldn't make 600hp naturally aspirated in a production vehicle with cutting edge technology is just naysaying and ignorant.
I know a flat plane V8, dohc Ferrari engine is completely different, but if Ferrari built a 7 liter V8 it would make close to 800 horsepower with equivalent tuning to the Speciale.
GM can get 75% of that easily.
I also didn't mean to imply that 7500rpm would be it's peak power, but its redline.
09-07-2013, 11:55 PM
#44
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FI engines always need to be running rich and run low compression because of detonation concerns. They suck a lot of fuel compared to equivalent hp NA engines.
The ZR1 is an example of this common occurrence. Even off boost they get worse mpg than a high compression LS7. On boost, well it's going to get a lot worse but then in this case of course your also making more power.
The ZR1 is an example of this common occurrence. Even off boost they get worse mpg than a high compression LS7. On boost, well it's going to get a lot worse but then in this case of course your also making more power.
09-08-2013, 12:37 AM
#45
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That said, to add my vote: supercharged. Keep the turbos elsewhere. I want my torque RIGHT FRICKEN NOW!
09-08-2013, 12:38 AM
#46
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09-08-2013, 02:41 AM
#47
Burning Brakes
The method you do FI is the issue - roots blowers are just not very efficient. If you use a centrifugal compressor you pick up efficiency, BUT getting 100,000 rpm from the driveshaft throws a lot of that efficiency gain away in the supercharger gearbox. Hence a turbo - use waste heat and you get the efficiency back.
The other approach is to use a twin-screw Whipple blower, but that would concede that Ford had a better idea....not gonna happen in a production Vette.
Since BOTH power and fuel economy are big drivers - Like C&D reported, I think GM may very well do a twin turbo set-up on a smaller motor (5.5L from the C7.R ??) to maintain or reduce weight, reduce the fuel burn penalty, and make loads of power. They are already working on one for the Cadillac CTS-VSport using their DOHC DI 3.6L V-6 which will make 420+HP. Let's see: 5.5/3.6 * 420HP = 672 HP......
Based on Reuss's comments on the "lightness" of the Camaro Z28 which he prefers over the "heavy metal thunder" of the ZL-1, I think this is where HE wants to go.
The only downside I see is, it ain't gonna be cheap. But look at the competition......a comparably equipped 911S is $125-140K, a 911 Turbo is $180K, and a Ferrari, McLaren, Aston-Martin or Lamborghini of comparable performance are well over $ 200K....hence a $100K Z-version of the Stingray sounds pretty competitive.
What all this means, (I think) is that a C6 Z06 is a unique Corvette, (not unlike the 1970's L88), an everyman's supercar that may well become a collector's car in the not too distant future. You Z06 owners may want to take real good care of your babies.....they could become investments.
09-08-2013, 04:22 AM
#48
Drifting
Like I said earlier in the thread, it's a 100% guarantee we will have a forced induction car.
People doubting that a 7 liter LS couldn't make 600hp naturally aspirated in a production vehicle with cutting edge technology is just naysaying and ignorant.
I know a flat plane V8, dohc Ferrari engine is completely different, but if Ferrari built a 7 liter V8 it would make close to 800 horsepower with equivalent tuning to the Speciale.
GM can get 75% of that easily.
I also didn't mean to imply that 7500rpm would be it's peak power, but its redline.
People doubting that a 7 liter LS couldn't make 600hp naturally aspirated in a production vehicle with cutting edge technology is just naysaying and ignorant.
I know a flat plane V8, dohc Ferrari engine is completely different, but if Ferrari built a 7 liter V8 it would make close to 800 horsepower with equivalent tuning to the Speciale.
GM can get 75% of that easily.
I also didn't mean to imply that 7500rpm would be it's peak power, but its redline.
The 4.5 isn't anything like the ls7 though. Sure the ls7 revs to 7000, but it doesn't need to. It makes peak power at 6300rpms. It could redline at 6800 just as easy if they wanted, they just didn't want to mess with gearing and needed to keep it in its power band. The 4.5 makes peak power at its 9000rpm redline. It may be small, but that shows those heads are flowing plenty of air, and keeps pulling harder and harder to redline.
You cant just say "if it was bigger, think of the power it would make." The law of diminishing returns applies, something's got to give. Bore it out and stroke it, now you have heavier pistons, and a longer throw, both of which might contribute to less possible rpms. That engine is optimized at its displacement, with heads and intake to match. Just as the new 6.3L v12 in the F12. It was bored out .3 liters more(in part) to achieve its power level, but it spreads that .3 liters out over 12 cylinders, minimizing the impact.
DOHC is just more capable of flowing air through the valves better, despite displacement. In fact it arguably avoids displacement, to avoid the added weight/size of the internals and instead keeps the rpms crazy high.
I understood you meant a 7500rpm redline, but even so. If it can be revved to 7500, wouldn't it need to make peak power at about 6900rpms? That has nothing to do with DI, and everything to do with airflow. It'd be almost impossible to get a 7.0 pushrod to peak that high, be streetable, and pass all the EPA standards.
It's just not realistic to envision a 600hp, naturally aspirated, pushrod 7.0 with the new EPA standards coming up.
09-08-2013, 06:39 AM
#49
Drifting
09-08-2013, 07:42 AM
#50
Team Owner
They are apples to Orange engine designs no doubt. I'm an engineer, I understand that very well.
The biggest factor here is a 2.5 liter displacement difference. The LS7 technology is 9 years old.
We have crate motors that are NA and make over 600 horsepower that use a carburetor and are OHV designs.
You can't tell me that 600hp is a hard goal to reach with technology in a 7 liter engine and do it reliably.
Here's how you do it:
Compression goes to 12:1, direct injection, better head and valve flow, slightly more aggressive cam profile with vvt for proper idle characteristics and high end power, 7500rpm.
That's not even a hard thing to conceptualize or execute for the level of engineering that GM has.
The biggest factor here is a 2.5 liter displacement difference. The LS7 technology is 9 years old.
We have crate motors that are NA and make over 600 horsepower that use a carburetor and are OHV designs.
You can't tell me that 600hp is a hard goal to reach with technology in a 7 liter engine and do it reliably.
Here's how you do it:
Compression goes to 12:1, direct injection, better head and valve flow, slightly more aggressive cam profile with vvt for proper idle characteristics and high end power, 7500rpm.
That's not even a hard thing to conceptualize or execute for the level of engineering that GM has.
09-08-2013, 08:56 AM
#51
Le Mans Master
But the detonation concern still applies as it's boosted and it still needs lowered compression and rich jetting.
The heat that is generated is all around. The oil heats up, the compressor runs hot and it's a big heater in the engine bay, radiator flow is restricted by an intercooler, and the intake air has more heat in it.
That Evo that was mentioned is an example of what I'm talking about in regards to FE. Boosted it might make as much power as an LS7, but it gets way less mpg in day to day operation I absolutely guarantee it.
Last edited by Suns_PSD; 09-08-2013 at 08:58 AM.
09-08-2013, 09:10 AM
#52
Le Mans Master
The light boost on a gen 5 v8 will along with packaging advantages have supercharged 6.2 liter engines being the order of the day for higher performance level production corvettes..
Probably have production not in Wixom but rather Bowling Green as discussed in the latest video of Mark Reuss and the motor trend round table discussion video (WOT)..
I'm sure the c7 z06 will be insanely fast and track worthy beyond most drivers capabilities.....
I wouldn't worry about heat or weight ....
This is not some "tuner" package....this is GM engineering and they don't mess around and do anything except deliver excellence in execution...
GM engineering is insane with their level of perfection in implementation of high performance...
The cost of materials will go up exponentially for sure ..but if you want to play....you have to pay....
I don't see me dropping the extra 30 grand or almost double over the standard z51 stingray but I will enjoy the testing etc...and for those who do buy them......they will have the best of the best ..
Probably have production not in Wixom but rather Bowling Green as discussed in the latest video of Mark Reuss and the motor trend round table discussion video (WOT)..
I'm sure the c7 z06 will be insanely fast and track worthy beyond most drivers capabilities.....
I wouldn't worry about heat or weight ....
This is not some "tuner" package....this is GM engineering and they don't mess around and do anything except deliver excellence in execution...
GM engineering is insane with their level of perfection in implementation of high performance...
The cost of materials will go up exponentially for sure ..but if you want to play....you have to pay....
I don't see me dropping the extra 30 grand or almost double over the standard z51 stingray but I will enjoy the testing etc...and for those who do buy them......they will have the best of the best ..
09-08-2013, 10:53 AM
#53
I would love a na 7liter that is makes big power but I believe we will get the sc engine because of cost and simplicity for the factory.
09-08-2013, 11:09 AM
#54
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I would surely hope so, but I'm not tall enough in the DI tech to know for sure. It does make sense, though. Hopefully they figure out something that can help with their present FI'd V8s and the (lack of) fuel economy. Nineteen miles per gallon on the highway sorta sucks.
09-08-2013, 11:39 AM
#55
Race Director
Exactly! 
And, that high RPM peak HP comes at the expense of low and mid range torque. Look at the torque curve for the LT1. How are you going to keep that with a high rpm turbp motor?
Last edited by tuxnharley; 09-08-2013 at 11:46 AM.
09-08-2013, 11:55 AM
#56
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If I had to go FI on the C7, I'd put a Procharger and air/air intercooler on the stock intake manifold/TB before I'd want to put a positive displacement blower up there.
Too much weight increase, right at the worst possible place on an engine: all at the top. Also requires liquid charge cooling. Yes, it works, but it weighs more and has another pump, as compared to air/air intercooling.
With a centri, the plumbing for air/air will be straight forward and not too long, so no problem.
The biggest thing I like about the C7 design is that everywhere you look, you get to have your cake and eat it, too. I think it would be a crying shame to alter the fundamental design recipe and move away from that philosophy, such as sharply reducing off-power fuel economy due to on-power design considerations, etc.
Too much weight increase, right at the worst possible place on an engine: all at the top. Also requires liquid charge cooling. Yes, it works, but it weighs more and has another pump, as compared to air/air intercooling.
With a centri, the plumbing for air/air will be straight forward and not too long, so no problem.
The biggest thing I like about the C7 design is that everywhere you look, you get to have your cake and eat it, too. I think it would be a crying shame to alter the fundamental design recipe and move away from that philosophy, such as sharply reducing off-power fuel economy due to on-power design considerations, etc.
09-08-2013, 12:00 PM
#57
Le Mans Master
If they can't meet their goals with a NA engine, I'm hoping they go the turbo route. Turbos are mounted low, giving the engine a lower center of gravity. You can run a simpler and more thermally efficient air-to-air intercooler. The turbo compressors are more efficient, giving lower charge temperatures. You can put in a much better intake manifold with tuned runners. Turbos have lower parasitic losses. The upper horsepower potential is much higher. Porsche's upcoming 2014 911 Turbo has getting 560 horsepower out of 3.8L.
Michael
Michael
09-08-2013, 12:47 PM
#58
Safety Car
I don't see the new Z being 600hp all motor. With the right CAM and 7 liters of dispalcement 600hp can be met. That is, the LT platform could in principle reach those numbers but...
The problem with a 600hp pushrod is variable valve timing. GM did not develop the VVT enough to get the power and emissions and reliability at the same time. The engine head barely flows more than the old generation so the only way to make 600hp NA is to have a very extreme cam. With a proper VVTL(i) the LT1 could meet emissions, power, NVH, and reliability targets but GM did NOT develop such a thing. The improvements in VVT are pretty much negligible from the previous generation. GM's solution for squeezing in more air in a pushrod is the TVS.
Why TVS and not turbo:
*leaked CAD showing the damn thing
*leaked cluster TVS symbol
*pulley assembly design. Look at the way every accessory runs on one belt. The crank pulley itself is only used 40% with all accessories painfully forced to run on only one belt. Why do you think there is room for a 11-rib belt on the crank pulley? A turbo does not need it, and a dry sump is already integrated.
It's going to be TVS for the Z. No doubt about it.
The problem with a 600hp pushrod is variable valve timing. GM did not develop the VVT enough to get the power and emissions and reliability at the same time. The engine head barely flows more than the old generation so the only way to make 600hp NA is to have a very extreme cam. With a proper VVTL(i) the LT1 could meet emissions, power, NVH, and reliability targets but GM did NOT develop such a thing. The improvements in VVT are pretty much negligible from the previous generation. GM's solution for squeezing in more air in a pushrod is the TVS.
Why TVS and not turbo:
*leaked CAD showing the damn thing
*leaked cluster TVS symbol
*pulley assembly design. Look at the way every accessory runs on one belt. The crank pulley itself is only used 40% with all accessories painfully forced to run on only one belt. Why do you think there is room for a 11-rib belt on the crank pulley? A turbo does not need it, and a dry sump is already integrated.
It's going to be TVS for the Z. No doubt about it.
09-08-2013, 12:53 PM
#59
Race Director
I don't see the new Z being 600hp all motor. With the right CAM and 7 liters of dispalcement 600hp can be met. That is, the LT platform could in principle reach those numbers but...
The problem with a 600hp pushrod is variable valve timing. GM did not develop the VVT enough to get the power and emissions and reliability at the same time. The engine head barely flows more than the old generation so the only way to make 600hp NA is to have a very extreme cam. With a proper VVTL(i) the LT1 could meet emissions, power, NVH, and reliability targets but GM did NOT develop such a thing. The improvements in VVT are pretty much negligible from the previous generation. GM's solution for squeezing in more air in a pushrod is the TVS.
Why TVS and not turbo:
*leaked CAD showing the damn thing
*leaked cluster TVS symbol
*pulley assembly design. Look at the way every accessory runs on one belt. The crank pulley itself is only used 40% with all accessories painfully forced to run on only one belt. Why do you think there is room for a 11-rib belt on the crank pulley? A turbo does not need it, and a dry sump is already integrated.
It's going to be TVS for the Z. No doubt about it.
The problem with a 600hp pushrod is variable valve timing. GM did not develop the VVT enough to get the power and emissions and reliability at the same time. The engine head barely flows more than the old generation so the only way to make 600hp NA is to have a very extreme cam. With a proper VVTL(i) the LT1 could meet emissions, power, NVH, and reliability targets but GM did NOT develop such a thing. The improvements in VVT are pretty much negligible from the previous generation. GM's solution for squeezing in more air in a pushrod is the TVS.
Why TVS and not turbo:
*leaked CAD showing the damn thing
*leaked cluster TVS symbol
*pulley assembly design. Look at the way every accessory runs on one belt. The crank pulley itself is only used 40% with all accessories painfully forced to run on only one belt. Why do you think there is room for a 11-rib belt on the crank pulley? A turbo does not need it, and a dry sump is already integrated.
It's going to be TVS for the Z. No doubt about it.
Last edited by Chicago1; 09-08-2013 at 02:20 PM.
09-08-2013, 12:55 PM
#60
Safety Car
If they can't meet their goals with a NA engine, I'm hoping they go the turbo route. Turbos are mounted low, giving the engine a lower center of gravity. You can run a simpler and more thermally efficient air-to-air intercooler. The turbo compressors are more efficient, giving lower charge temperatures. You can put in a much better intake manifold with tuned runners. Turbos have lower parasitic losses. The upper horsepower potential is much higher. Porsche's upcoming 2014 911 Turbo has getting 560 horsepower out of 3.8L.
Michael
Michael
If the turbines were to go low on the sides, is there even enough room in the Vette for that?