13 details to know about the Z06’s 670-hp LT6 V-8
11-11-2021, 10:21 AM
#61
E-Ray, 3LZ, ZER, LIFT
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Piston oil squirters are primarily for cooling, my guess is that it is only seeing 20" hg of crankcase vacuum at a certain rpm level as there is no dedicated crankcase vacuum pump like they run in Comp and Pri Stock
I would love to see a log trace of crankcase vacuum going up through the gears.
I would love to see a log trace of crankcase vacuum going up through the gears.
Most racing dry sump external pumps have many scavenge sections that create a vacuum in the crackcase. Some allow them to be added sections as pic below.
The 6 scavenge pumps in the LT6 when Tracking with the engine running from ~5000 to 8600 rpm obviously generate lot of vacuum.
.
Last edited by JerryU; 11-11-2021 at 10:23 AM.
11-13-2021, 05:19 AM
#62
Le Mans Master
All the old style DOHC engines used shim under bucket or shim over bucket when running solid valvetrains. The problem with the bucket lifter design is that ALL the lift comes from the cam lobe, there is no rocker multiplication. This is a finger follower combined with buckets which seems to be the best system thus far as you get some multiplication ratio from the follower while being more stable than a traditional rocker arm.
fastlane "the hard way" went solid and 9k rpms pretty cool stuff
11-13-2021, 05:55 AM
#63
Race Director
Great article and incredible engineering !!!
I can't wait to get mine but I'm perfectly fine with getting a second or third model year car....
I can't wait to get mine but I'm perfectly fine with getting a second or third model year car....
11-13-2021, 10:24 AM
#64
it will be different yes but you will feel the power more in the z06. You will still get a strong pull at lower rpms but there will be an incredible rush at mid and higher rpms. Those who have ridden dirt bikes know exactly what I am talking about. Equally powered 2 stroke vs 4 stroke feel completely different. 4 strokes pull moderately all the time but never super strong in comparison to a 2 stroke which will have light pull at low rpms then pull like a friggin rocket at high rpms. So much so that if you do not have a very tight grip it will eject you off the back. Don’t ask how I know. This effect is much more pronounced in a 2 stroke dirt bike but I suspect the z06 will have moderate to strong pull at lower rpms then crazy pull mid to high rpms. Should be a fun ride.
11-13-2021, 10:43 AM
#65
Pro
Just to point out a few things and dispel some incorrect statements in this thread and others I've read about this engine and engines in general.....
So... not to cast a shadow on this engine in anyway, this engine is a well engineered masterpiece, but there is no new technology that hasn't been done before in this engine.
The lower torque than the LT2 has nothing to do with the cylinder heads, intake or exhaust systems or crankshaft at all. The lower torque is because of the lower displacement and stroke of the engine.
A 2 valve head on this engine, that produced the same 672 hp, wouldn't make anymore torque in fact it would likely make less torque.
All modern production performance engines achieve VE numbers over 100%
They have for decades.
The LT2 is over 100% VE at peak torque. as was the LS7 and LS1 and LT1 from the 90's.... the list goes on and on.
Wave tuning is nothing new at all. Do you guys remember the 440 max wedge cross ram? 305 TPI? 91 LT1?
The difference is what order they were using to tune the torque peak. 1st order or 2nd, 3rd, 4th, etc. Each one of these engines used a different order by design.
As for dry sumps and pulling a vacuum... typically with very thin, low tension rings at high rpm they like (need) the early sealing assist of vacuum, the reduced ring weight reduces ring flutter.
They used a very thin low tension ring for several reasons but primarily to reduce ring weight to delay the onset of ring flutter at higher rpm's, The vacuum in the sump also helps with initial ring seal before the
higher cylinder pressures develop during initial combustion and also during the lower pressure intake stroke for oil control. Typically 15" hg is the sweet spot in most engines and a vacuum break is used
to control limit the vacuum while using an "oversized volume" scavenge pump so you can keep the 15" in the crank case at lower engine rpm's. The oversized scavenge volume also compensates for engine wear during the life cycle of the engine.
As an added bonus with the reduction of air in the crank case it reduces the windage and pumping losses but more importantly "oil wrap up" around the crank and rods much like crank scraper does. Also, dividing the crank case into 4 v twin engines
effectively keeps the crankcase volume constant in each bay and reducing pumping losses even further.
Piston squirters are primarily used to keep the piston crowns cool like in a diesel application, but they do assist in dry sump engine applications (that are pulling a crankcase vacuum and stripping oil) to prevent (reduce) the galling of the wrist pins in the piston pin bores. Typically you run an application like this with a slightly looser pin fitment in the rod and pistons to also help reduce galling along with DLC coating. In most engines the cooling oil from the rod bearings and is enough to do all this but this engine is stripping away all the oil from the crank as fast as it can.
There are a few 1st's for GM with this LT6 ill give you that.... but they didn't discover or execute anything that wasn't already known and put into production elsewhere in the industry.
Again in not trying to take anything away from this awesome engineering masterpiece.
So... not to cast a shadow on this engine in anyway, this engine is a well engineered masterpiece, but there is no new technology that hasn't been done before in this engine.
The lower torque than the LT2 has nothing to do with the cylinder heads, intake or exhaust systems or crankshaft at all. The lower torque is because of the lower displacement and stroke of the engine.
A 2 valve head on this engine, that produced the same 672 hp, wouldn't make anymore torque in fact it would likely make less torque.
All modern production performance engines achieve VE numbers over 100%
They have for decades.
The LT2 is over 100% VE at peak torque. as was the LS7 and LS1 and LT1 from the 90's.... the list goes on and on.
Wave tuning is nothing new at all. Do you guys remember the 440 max wedge cross ram? 305 TPI? 91 LT1?
The difference is what order they were using to tune the torque peak. 1st order or 2nd, 3rd, 4th, etc. Each one of these engines used a different order by design.
As for dry sumps and pulling a vacuum... typically with very thin, low tension rings at high rpm they like (need) the early sealing assist of vacuum, the reduced ring weight reduces ring flutter.
They used a very thin low tension ring for several reasons but primarily to reduce ring weight to delay the onset of ring flutter at higher rpm's, The vacuum in the sump also helps with initial ring seal before the
higher cylinder pressures develop during initial combustion and also during the lower pressure intake stroke for oil control. Typically 15" hg is the sweet spot in most engines and a vacuum break is used
to control limit the vacuum while using an "oversized volume" scavenge pump so you can keep the 15" in the crank case at lower engine rpm's. The oversized scavenge volume also compensates for engine wear during the life cycle of the engine.
As an added bonus with the reduction of air in the crank case it reduces the windage and pumping losses but more importantly "oil wrap up" around the crank and rods much like crank scraper does. Also, dividing the crank case into 4 v twin engines
effectively keeps the crankcase volume constant in each bay and reducing pumping losses even further.
Piston squirters are primarily used to keep the piston crowns cool like in a diesel application, but they do assist in dry sump engine applications (that are pulling a crankcase vacuum and stripping oil) to prevent (reduce) the galling of the wrist pins in the piston pin bores. Typically you run an application like this with a slightly looser pin fitment in the rod and pistons to also help reduce galling along with DLC coating. In most engines the cooling oil from the rod bearings and is enough to do all this but this engine is stripping away all the oil from the crank as fast as it can.
There are a few 1st's for GM with this LT6 ill give you that.... but they didn't discover or execute anything that wasn't already known and put into production elsewhere in the industry.
Again in not trying to take anything away from this awesome engineering masterpiece.
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Zaro Tundov (11-13-2021)
11-13-2021, 10:58 AM
#66
That was a great article. The LT6 is a mechanical masterpiece on paper and no doubt will have the performance to back it up. To me, one of the most amazing parts is the crankshaft working in a vacuum. It takes a well sealed (and well built) motor to do that especially for extended service,. Those scavenging pumps sure sound like vacuum pumps to me that are commonly used on race motors. I had one on a previous set up and it really makes a difference when used with low tension piston rings. The DLC is also a big plus. They have been used on engine internals for years in the race world and help more than you would think. Can't wait to see real world results when it finally comes out.
11-14-2021, 08:59 AM
#67
Melting Slicks
Member Since: Feb 2015
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I read an early review after the reveal that the LT6 was a 120* V vs 90* to reduce FPC vibration and for packaging benefits. Haven’t read that since. Is it? I’ve been telling folks 120* bragging about this engineering marvel… which it is regardless.
11-14-2021, 09:36 AM
#68
Le Mans Master
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Location: North Dallas 40 TX
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standard 90 degree V8. I don’t think a 120 would fit in the engine bay as designed.