ZR1 BOMBSHELL PROOF!!! TT 5.5L LT7 it is!!!
10-31-2023, 01:03 PM
#41
GS or RedLS6 can someone get a picture of said "shoes"... never heard of this concept before. What are we talking about?
10-31-2023, 01:44 PM
#42
10-31-2023, 01:45 PM
#43
Pro
SC Turbos ?!?!
https://www.garrettmotion.com/turboc...argers/sc-vnt/
Split Compression VNT (SC-VNT) Turbo
https://www.garrettmotion.com/turboc...argers/sc-vnt/
10-31-2023, 01:46 PM
#44
SC Turbos ?!?!
https://www.garrettmotion.com/turboc...argers/sc-vnt/
Split Compression VNT (SC-VNT) Turbo
https://www.garrettmotion.com/turboc...argers/sc-vnt/
10-31-2023, 01:54 PM
#45
Le Mans Master
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That would be Dynamic Skip Fire, I'm surprised they haven't adapted it to the Vette yet. It also solves a number of vibration issues by spreading the vibration power away from one frequency and around the rpm spectrum. But we'll see. Shoes are a great concept if they can implement.
Am I missing something?
10-31-2023, 01:57 PM
#46
Go watch the video in the other thread... that's exactly what it is.
10-31-2023, 02:27 PM
#47
Race Director
What could go wrong with that setup?
Last edited by 23/C8Z; 10-31-2023 at 03:22 PM.
10-31-2023, 04:07 PM
#48
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The one about why it sounds different? The Eaton thing?
Below is a picture of the valvetrain of the LT6 from this article https://www.enginelabs.com/news/gm-a...t-plane-crank/
There is no part between the cam lobe and the valve stem that has enough height to collapse so the cam will not move the valve. While there is a fulcrum for the follower, detaching the arm from the fulcrum would not stop the valve from moving. I understand the theory in other configurations, I don't understand it in this configuration without significantly changing the head configuration. Maybe that is their plan.
Below is a picture of the valvetrain of the LT6 from this article https://www.enginelabs.com/news/gm-a...t-plane-crank/
There is no part between the cam lobe and the valve stem that has enough height to collapse so the cam will not move the valve. While there is a fulcrum for the follower, detaching the arm from the fulcrum would not stop the valve from moving. I understand the theory in other configurations, I don't understand it in this configuration without significantly changing the head configuration. Maybe that is their plan.
10-31-2023, 04:26 PM
#49
Glad all the BS engine rumors regarding the ZR1 motor have been dismissed.
Everyone who's been paying attention has knows this info since the CAD was leaked 5 years ago.
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10-31-2023, 04:50 PM
#50
Pro
The Gen6 heads coming out shortly are significantly different in several ways from the LT6 heads, even thou the LT6 is technically a Gen6 engine.
The biggest difference is the valve actuation, mainly the fulcrum point and how it operates.
All new GM V8 engines coming out from now on are going to be Gen6 with tumble not swirl. ALL swirl engines are going to be gone.
The gas trucks are getting one hell of an engine. Very few will need the Dirtymax anymore.
Id expect an info dump in the truck mags soon. Cant wait to see what Banks will do to this engine. Cant imagine an 600HP gas truck with a warranty!!!
The biggest difference is the valve actuation, mainly the fulcrum point and how it operates.
All new GM V8 engines coming out from now on are going to be Gen6 with tumble not swirl. ALL swirl engines are going to be gone.
The gas trucks are getting one hell of an engine. Very few will need the Dirtymax anymore.
Id expect an info dump in the truck mags soon. Cant wait to see what Banks will do to this engine. Cant imagine an 600HP gas truck with a warranty!!!
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10-31-2023, 04:55 PM
#51
The benefit of a FPC is diminished with forced induction. FI does not rely on scavenging to increase the volumetric efficiency. Increasing the turbo count decreases lag by utilizing smaller turbos which also decreases the max engine speed. A CPC is stronger and smoother then a FPC.
When Ford developed the GT500 they used a CPC instead of the FPC from the GT350. It makes sense to use a CPC in the LT7 if it is utilizing turbo's.
I believe there could be a slight bore reduction with an increased stroke to make the 5.5L displacement relative to the LT6. There are many benefits to making these changes.
When Ford developed the GT500 they used a CPC instead of the FPC from the GT350. It makes sense to use a CPC in the LT7 if it is utilizing turbo's.
I believe there could be a slight bore reduction with an increased stroke to make the 5.5L displacement relative to the LT6. There are many benefits to making these changes.
Last edited by Drew888; 10-31-2023 at 05:06 PM.
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10-31-2023, 05:26 PM
#52
The one about why it sounds different? The Eaton thing?
Below is a picture of the valvetrain of the LT6 from this article https://www.enginelabs.com/news/gm-a...t-plane-crank/
There is no part between the cam lobe and the valve stem that has enough height to collapse so the cam will not move the valve. While there is a fulcrum for the follower, detaching the arm from the fulcrum would not stop the valve from moving. I understand the theory in other configurations, I don't understand it in this configuration without significantly changing the head configuration. Maybe that is their plan.
Below is a picture of the valvetrain of the LT6 from this article https://www.enginelabs.com/news/gm-a...t-plane-crank/
There is no part between the cam lobe and the valve stem that has enough height to collapse so the cam will not move the valve. While there is a fulcrum for the follower, detaching the arm from the fulcrum would not stop the valve from moving. I understand the theory in other configurations, I don't understand it in this configuration without significantly changing the head configuration. Maybe that is their plan.
https://videos.eaton.com/detail/vide...autoStart=true
10-31-2023, 05:39 PM
#53
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That would be Dynamic Skip Fire, I'm surprised they haven't adapted it to the Vette yet. It also solves a number of vibration issues by spreading the vibration power away from one frequency and around the rpm spectrum. But we'll see. Shoes are a great concept if they can implement.
Interesting… apparently this DFM is the replacement for AFM and what we are talking about in this LT7 application?
https://gmauthority.com/blog/gm/gene...on-technology/
10-31-2023, 05:43 PM
#54
Drifting
Speaking to the Gen 6; they would need a slight redesign of the follower/head with a dual pivot. They can pivot in the middle as Eaton does or pivot around the valve tip with a head modification (low mass), as Mazda does, during deactivation. I've also seen a slider incorporated into the valve tip (non production). These systems do add a bit of mass.
The real magic in dynamic skip fire is the ability to reduce noise, vibration, and spread cylinder loading around. Let's say in testing, they need 4 cylinders active at a certain spot for the torque demand, but determine that in V4 mode, there's a bad vibration from the driveline/dct. In my overly simplified example to fix this issue, dynamic skip fire (in two crank revolutions) would fire 1 cylinder (instead of 8), then the next 2 crank revolutions would fire 2 cylinders (instead of 8), then 3 (instead of 8), then 5 (instead of 8), then 6, then 7. The average torque output (1+2+3+5+6+7)/6 is equal to 4 cylinders, but the vibration frequencies and noise are spread away from 4-cylinder mode and no longer excite the driveline resonance. If anyone's familiar with a fractional-N divider, that's how it works. It was brought to AFM in combustion engines use by a guy with a signal processing EE background, and the concept has been used in electrical dividers for a long time.
10-31-2023, 05:50 PM
#55
Melting Slicks
Thread Starter
The one about why it sounds different? The Eaton thing?
Below is a picture of the valvetrain of the LT6 from this article https://www.enginelabs.com/news/gm-a...t-plane-crank/
There is no part between the cam lobe and the valve stem that has enough height to collapse so the cam will not move the valve. While there is a fulcrum for the follower, detaching the arm from the fulcrum would not stop the valve from moving. I understand the theory in other configurations, I don't understand it in this configuration without significantly changing the head configuration. Maybe that is their plan.
Below is a picture of the valvetrain of the LT6 from this article https://www.enginelabs.com/news/gm-a...t-plane-crank/
There is no part between the cam lobe and the valve stem that has enough height to collapse so the cam will not move the valve. While there is a fulcrum for the follower, detaching the arm from the fulcrum would not stop the valve from moving. I understand the theory in other configurations, I don't understand it in this configuration without significantly changing the head configuration. Maybe that is their plan.
10-31-2023, 05:56 PM
#56
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I wonder how this will change the dimensions of the Gen VI versus LT2. Will it be wider? taller? heavier? Will the truck version have a taller deck?
10-31-2023, 05:58 PM
#57
Melting Slicks
Thread Starter
Interesting… apparently this DFM is the replacement for AFM and what we are talking about in this LT7 application?
https://gmauthority.com/blog/gm/gene...on-technology/
https://gmauthority.com/blog/gm/gene...on-technology/
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10-31-2023, 06:03 PM
#58
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I'm not convinced this system is going to be present on the ZR1, but I do think that it will be implemented on the Gen6 elsewhere.
Speaking to the Gen 6; they would need a slight redesign of the follower/head with a dual pivot. They can pivot in the middle as Eaton does or pivot around the valve tip with a head modification (low mass), as Mazda does, during deactivation. I've also seen a slider incorporated into the valve tip (non production). These systems do add a bit of mass.
The real magic in dynamic skip fire is the ability to reduce noise, vibration, and spread cylinder loading around. Let's say in testing, they need 4 cylinders active at a certain spot for the torque demand, but determine that in V4 mode, there's a bad vibration from the driveline/dct. In my overly simplified example to fix this issue, dynamic skip fire (in two crank revolutions) would fire 1 cylinder (instead of 8), then the next 2 crank revolutions would fire 2 cylinders (instead of 8), then 3 (instead of 8), then 5 (instead of 8), then 6, then 7. The average torque output (1+2+3+5+6+7)/6 is equal to 4 cylinders, but the vibration frequencies and noise are spread away from 4-cylinder mode and no longer excite the driveline resonance. If anyone's familiar with a fractional-N divider, that's how it works. It was brought to AFM in combustion engines use by a guy with a signal processing EE background, and the concept has been used in electrical dividers for a long time.
Speaking to the Gen 6; they would need a slight redesign of the follower/head with a dual pivot. They can pivot in the middle as Eaton does or pivot around the valve tip with a head modification (low mass), as Mazda does, during deactivation. I've also seen a slider incorporated into the valve tip (non production). These systems do add a bit of mass.
The real magic in dynamic skip fire is the ability to reduce noise, vibration, and spread cylinder loading around. Let's say in testing, they need 4 cylinders active at a certain spot for the torque demand, but determine that in V4 mode, there's a bad vibration from the driveline/dct. In my overly simplified example to fix this issue, dynamic skip fire (in two crank revolutions) would fire 1 cylinder (instead of 8), then the next 2 crank revolutions would fire 2 cylinders (instead of 8), then 3 (instead of 8), then 5 (instead of 8), then 6, then 7. The average torque output (1+2+3+5+6+7)/6 is equal to 4 cylinders, but the vibration frequencies and noise are spread away from 4-cylinder mode and no longer excite the driveline resonance. If anyone's familiar with a fractional-N divider, that's how it works. It was brought to AFM in combustion engines use by a guy with a signal processing EE background, and the concept has been used in electrical dividers for a long time.
10-31-2023, 06:08 PM
#59
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Great find and you're absolutely right, given the LT6 valvetrain (compared to the LMA 4.2L TT motor) the collapable follower is out of the question! That's why when I first posted this, John Elegant shortly thereafter on the MECF, confirmed that "from a reliable confidential source" that the AFM on the Engine Nomenclature in the Parts Catalog is an error and now I know why after seeing this! John is a straight shooter, not a YouTube "influencer" so when he says no AFM, believe it!
10-31-2023, 07:13 PM
#60
The benefit of a FPC is diminished with forced induction. FI does not rely on scavenging to increase the volumetric efficiency. Increasing the turbo count decreases lag by utilizing smaller turbos which also decreases the max engine speed. A CPC is stronger and smoother then a FPC.
When Ford developed the GT500 they used a CPC instead of the FPC from the GT350. It makes sense to use a CPC in the LT7 if it is utilizing turbo's.
I believe there could be a slight bore reduction with an increased stroke to make the 5.5L displacement relative to the LT6. There are many benefits to making these changes.
When Ford developed the GT500 they used a CPC instead of the FPC from the GT350. It makes sense to use a CPC in the LT7 if it is utilizing turbo's.
I believe there could be a slight bore reduction with an increased stroke to make the 5.5L displacement relative to the LT6. There are many benefits to making these changes.
Since the exhaust has more to do with engine note than anything else (which is how they got the Voodoo to sound like a CPC, even though it's an odd-firing-order FPC)...so why wouldn't it make sense to just lean into that and work FPC sound out of a FI or CPC application?
P.S.
With the advent of twin-scroll turbos, you don't need to compromise on performance/lag. And small turbos have never caused a reduction in max engine speed; rather they simply are tapped out on MFR and power drops off at the same red-line.
That's why I'm curious about something more exotic than a seemingly simple twin-scroll, twin-turbo setup. No sequential turbos, no compound turbos, no variable geometry turbos. Just a vane that use the venturi effect to spool the impeller at lower rpm.