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Jerry and Joe - by now we know that the Corvette guys don't do ANYTHING by accident and they love Easter Eggs. That snapshot of the cutaway engine in the teaser video was meant to tip us off to something new in an OHV / cam-in-block engine....question is what is it. My guess is we will find out for sure on 7.18.19, but if they went to the trouble of re-inventing the OHV engine, it may just be epic. The rumored 530 HP may be just a starting point.
I also doubt this is the case, but it is possible so I will mention it... the center sprocket that is omitted from the top of the photo, that sprocket may be a center sprocket attached to a 2nd cam, and is between yet 2 more sprockets and cams, one on top of each head, and that center sprocket could have another chain or 2 chains attached to sprockets on its same camshaft.
This would effectively give each head 3camshafts, but keep the top-heavy weight and crowded complexities to a minimum, as well as reduce overall weight by eliminating 2 of 6 camshafts, sprockets and chains, and accomplishing the same outcome of 6 camshafts with only 4 total camshafts.
Such a setup would allow them to change lobe durations, valve open duration times as 2 lobes could be assigned to a single valve, and then those cam lobes phased out of sync from each other to give a longer open duration... or do it the conventional way that cams currently do it, but do it down at the cam in the engine block instead...
They could accomplish this with 2 cams as well, but it may start to get crowded with pushrods if there are indeed 2 intake or exhaust valves per cylinder, so a 3rd cam would perhaps become useful.
The OHC on each side could be above the rocker tips, and the rocker tips could have a special add on that goes up to the OHC lobe. Again, probably not doable, but figure I would throw it out.
I'm also not sure if they could somehow get the rpm's up with having a single OHC on each head and the 2 in the middle of the block.... probably not, but perhaps there is something profound we are missing....
Perhaps eliminating the valvespring has a serious advantage, after all, it will eliminate the potential valve float, and can allow pushrod engine to then soar in RPM beyond what we understand currently. There would be no reason one could not then go to 10,000 rpm .
The pushrods would still open the valves, the cam on the head would force them closed again.
By no means would this be GM's exact geometry on the concept, but here is the crude idea using pushrods and a cam to close the valves instead of springs....
Again, the Single OHC would be chain driven off the top middle chain driven cam's second sprocket, which is omitted from GM's teaser photo.
Again, I don't believe they used 3 per head, it's probably only the 2 in the middle and still using springs, but I'm simply giving us something to chat about.
If they wanted to get fancy, they could put 2 valve-closing cams, one above the intake valves and one above the exhaust valves, and then they could tie each of their timings to the 2 separate middle cams, and then they could still do independent phasing of both the intake and exhaust valves, and still rev to the moon.
The other option is to have a single cam run both the up and down of the valve, without the spring, just using 2 rockers and 2 lobes, one to control each direction of movement, as seen in the image below...
Quick, Someone file a patent with the center overhead cam in the head closing the valves while the 2 pushrod cams in the V of the block open the intake and exhaustvalves... if GM has not already
Last edited by bbbvettes.com; 05-26-2019 at 01:18 PM.
Quick, Someone file a patent with the center overhead cam in the head closing the valves while the 2 pushrod cams in the V of the block open the intake and exhaustvalves... if GM has not already
Probability someone already has it or something similar patented!
Desmodromic valve systems are first mentioned in patents in 1896 by Gustav Mees! No valve springs, just use a cam follower to close as well as open valves. Motorcycle folks, who operate at very high rpm, have used it effectively! In any case the US patent examiner will download every valve patent since the 1800reds and say, "it's not new!" Easy 1st step taking little time on their part! Then you have to go through each one and show why your idea is different (politely!)
SIDEBAR
Had an old Prof who when working for a chemical company did that. They would look at a chemical manufacturing process patent, see ways to improve it and get patents on the improvement without every doing more than filing words and figures. There is no need to have a working model or device, just need to convince the examiner it's unique. He said they occasionally would sell that patent to the original company!
There is so much information in this thread, I don’t know if this idea has been thrown out there but here’s what I think.
I think this will be a hybrid type motor in which the exhaust valves or actuated by the in-block cam,
The intake valves for each cylinder head will have a dedicated camshaft.
My prediction is these motors will be three cam motors single cam exhaust valve motor with two intake valve cams one for each cylinder head.
The second timing chain is for the intake cams in the cylinder Head. This will allow for a single overhead cam motor in which the cylinder heads are narrow not like a double overhead cam motor. With the intake cams and a single exhaust cam separately cam phasing on the intake and exhaust can still be done just like the cutaway shows.
The exhaust portion of the cylinder head really does not need overhead cam as anybody who is done cylinder head development knows that the exhaust valves are aided by combustion. That’s why they are always smaller and much lighter than intake valves. The intake valves are what always give engine builders the toughest time with motion control. The combination of weight and valve spring pressure along with seat pressure is always a challenge.
Excited to see and if that’s what it is. If not, somebody needs to develop a three cam motor.
There is so much information in this thread, I don’t know if this idea has been thrown out there but here’s what I think.
I think this will be a hybrid type motor in which the exhaust valves or actuated by the in-block cam,
The intake valves for each cylinder head will have a dedicated camshaft.
My prediction is these motors will be three cam motors single cam exhaust valve motor with two intake valve cams one for each cylinder head.
The second timing chain is for the intake cams in the cylinder Head. This will allow for a single overhead cam motor in which the cylinder heads are narrow not like a double overhead cam motor. With the intake cams and a single exhaust cam separately cam phasing on the intake and exhaust can still be done just like the cutaway shows.
The exhaust portion of the cylinder head really does not need overhead cam as anybody who is done cylinder head development knows that the exhaust valves are aided by combustion. That’s why they are always smaller and much lighter than intake valves. The intake valves are what always give engine builders the toughest time with motion control. The combination of weight and valve spring pressure along with seat pressure is always a challenge.
Excited to see and if that’s what it is. If not, somebody needs to develop a three cam motor.
Thank you for the post,
So that I have what you are saying straight, you believe all the valves will have springs, both intake and exhaust, and the SOHC on each head is to open the intake valves, and since there will be 2 intake valves per cylinder, their weight and valvetrain mass is greatly reduced, which will allow for higher rpm, is this correct?
Do you believe it is a cam on top of the head and the cam up in the middle which is not shown, or do you believe it is 2 cams up in the middle not shown?
The 2 lower cams in the center of the block, (I'm trying to wrap my mind around where the center cams are used, since their pushrods will still be long and heavy, relatively speaking, and thus cause valve float at higher rpm...
unless we are throwing in the towel that rpm is not going to be increased much, and instead, they are using only the 3 center cams to be able to adjust opening durations and phasings only.
Do you anticipate that cams up high in the V would be able to allow for much higher rpm of the intake valves?
To put it bluntly, I'm trying to understand the purpose for the 3rd cam in your description, if it is only to run half the intake valves, which the other cam is doing on the first half of the intake valves. To me, that setup would only require 1 cam for all of the intake valves, and I do believe that will be the setup, just 2 cams total.
Last edited by bbbvettes.com; 05-26-2019 at 12:23 PM.
If you look closely at the cutaway picture I could be wrong it shows three what appeared to be roller lobes on that cam. I think there are actually four lobes as I think one is hidden behind the camp sprocket and you just can’t see it. looking closely at the lifter bore I believe there are two lifter bores per cylinder, however I think those will be for two exhaust valves per cylinder you will have a 16 lobe camshaft actuating 16 exhaust valves one cam only in the motor you will have two intake valves per cylinder actuated by two Individual camshaft one per each cylinder head this will be a four valve head operated by three camshaft I’m convinced.
This will accomplish everything in a modern V8 engine a narrow cylinder head, Camp phasing with independent operated intake and exhaust valves, hi rpm allowed by overhead cam intake valves.
If that’s not what it is I will be making phone calls to some of my cylinder head friends to develop a motor like this
okay, so when you say "high rpm allowed by overhead cam intake valves."
... are you saying the 2 cams will be high in the V, and those will be referred to as OHC, or are you saying you believe there will be an actual cam (or 2 per side) just above the valves up under the valve covers?
I agree that the bottom most cam should be for exhaust valves, and have 2 per chamber, and put the most mass/material on the exhaust valve pushrods because them floating is not the concern as much as the intake valves.
I believe the intake valve rockers could be 50 degree angle arms, instead of straight rockers... and the cam basically pushes the rockers from the side basically.
This could make for shorter pushrods, and reduce the weight enough of the system to prevent valve float.
The thing I don't understand well is how the oiling would work, as the V of the engine would now have to be enclosed, across to the top of each head, because of the lateral pushrods which interact with the angled rockers.
Last edited by bbbvettes.com; 05-26-2019 at 01:29 PM.
Just to be clear what I am saying is the intake cams are located one per each on the cylinder head the motor will have three cams total. one in each cylinder head and one came in the block for the exhaust valves
Bingo!
That picture says it all 16 lobe camshaft with two timing chains I bet you!
the part I am confused about is if there is a camshaft at each head, wouldn't the chain go up at an angle, and there need to be 2 chains in essentially a V configuration, going up to each SOHC?
Instead, it appears to me the chain goes straight up from the center cam, so that leads me to believe there is at least 1 more center cam up higher in the V, no?
This is why I believe there are only 2 total, it does no good to run the 3rd and 4th cam as an OHV cam on each head, as it would make the top center cam useless and cumbersome.
unless, you are implying the top center cam does not exist, and it is only a pulley/sprocket there, and it then has a chain that goes across like the top of a T and chain drives or gear drives the 2 OHC, 1 on each side, for a total of 3 cams.
The only way I believe the top center cam could be used with a SOHC on each side is if there is a cam being used to "close" the intake valves instead of springs, which is the post I put up last night.
What is interesting is, if a cam has the responsibility to close the valves, and you put it out of phase with the opening cam, then technically speaking you could change the duration. There would have to be "intentional floating" that would occur, and I am not sure how that would "wear" on parts in the valve train, (the lobes themselves and the rods or rockers impacting against them as they come back from their "float state" when the closing cam then reconnects with them and forces them back shut.
Last edited by bbbvettes.com; 05-26-2019 at 01:05 PM.
I'll come back to reality after this post, but wanted to post it...
(from my above post) "What is interesting is, if a cam has the responsibility to close the valves, and you put it out of phase with the opening cam, then technically speaking you could change the duration. There would have to be "intentional floating" that would occur, and I am not sure how that would "wear" on parts in the valve train, (the lobes themselves and the rods or rockers impacting against them as they come back from their "float state" when the closing cam then reconnects with them and forces them back shut."
on second thought, I'm not sure there would be an impact with intentional float... you see, you could set it up where the valve itself can only travel so far into the chamber, due to the valves actual shape of its stem (something keeps it from going any further than the opening cam lobe opens it (some sort of high tech oil pressure catch system, similar to what they already have to control valve stems).
so, The cam that opens the valve, does its job, and then gets out of the way, there is no spring to bring the valve back, gravity and/or the oil lock keeps the valve open and downward, as well as the incoming intake air keeps the valve downward and open.
The closing cam lobe, smoothly intercepts the rocker as the rocker is always going to be in the same place, so no harsh impact, and then the closing cam lobe can bring the valve closed. The explosion in the chamber is going to also keep the valve closed and so could the high tech oil locking mechanism on the valve stem in this 2nd location as well, so if the closing cam then came away from the rocker, the valve would still remain closed until the opening cam lobe then smoothly re-intercepts the rocker and forces the valve open again.
What I'm getting at is the open and close cam lobes would not need to be inverse mirrors of each other. Instead, they could be shorter durations each, but then the phasing of them changes the actual duration of the valve open and closing cycles.
... and now you could also rev to the moon.
Last edited by bbbvettes.com; 05-26-2019 at 01:16 PM.
I think you are confusing Duration with valve timing overlap. Motors with one cam have their respective lobe for intakes and exhaust cut in different center lines. This is over lap. This can change the characteristics of the motor. RPM, TQ, Vacum etc.
Motors with separate intake and exhaust cams allow for infinite changes in over lap.
I'm not sure what you are talking about when you say "Intentionally Floating". The only term I know is valve float. This is when a motor has a lack of valve spring pressure at high RPM in which the valve train components no longer can follow the lobes of the cam. The valves stop correct opening and closing causing lack of compression and timing and sometimes the valves bouncing off the seats and hitting the piston heads due to lack of timing. Sometimes ending in engine failure due to broken valves, bent push rods. etc.
I think you are confusing Duration with valve timing overlap.
I don't believe so. I'm back on this silly idea in the picture above, and I'm saying the lobe that opens the valve, would not have to be the perfect inverse of the lobe that closes the valve.
Instead, if there was an "oil lock" mechanism on the valve stem, kind of on the same road as koenigsegg is doing with their "freevalve" stuff, then the valve could be kept locked into a single position until the other lobe smoothly intercepts the rocker (since the point of interception will be exact and calculated for, so there would be no harsh impact, the valve is not springing back against the cam lobe, the valve is stationary awaiting smooth interception), and the inverse cam brings the valve to its opposite location.
Then the actual physical durations of the lobes for open and closed could be made very steep and very small durations... but the duration of the valve itself being open would actually be determined by the phasing between the opening and the closing cams.
4 cams total, 2 in middle, and 1 SOHC on each side which does all the closing or all the opening.
The 2 other inverse cams in the center of the block are independently phased. Now durations of both intake and exhaust can be changed to infinite variances and the duration could literally be computer controlled, and have a curve as the car goes up through its rpm's,
and since we have eliminated springs and unwanted valve float, everything can also rev to the moon.
I don't believe GM is here yet. 1 step at a time.
Last edited by bbbvettes.com; 05-26-2019 at 02:48 PM.
This pictures shows clearly a 16 lobe single cam and spacing for 2 lifter bores per cylinder. So that leave these combinations:
1. Two cams in Block with 32 lobes and pushrods. That would be a nightmare.
2. 1 cam with 16 conventional intake and exhaust valves and who knows what that second chain is for?
3. 1 in block cam(exhaust), two SOHC heads(intake) with a total of three cams. ONLY LOGICAL from the picture.
And to the fairy tale's defense, the pushrods from the center cams would not need to cross. I drew them that way to match up with where ther rockers were in that image.
In real life, they would be almost parallel to each other and not interfere with each other at all.
So the top middle V cam would have the same count of lobes and pushrods as the bottom cam does.
And then the single or double cam up top, closing the valve, is just in line with the already existent rocker arms, 32 valves total.
5th possibility is there is there are still a total of 8 intake and 8 exhaust valves total between both sides, and the lower center cam opens both the intake and exhaust valves, and the top center cam closes them, and no OHC's. 16v total.
This would still allow the engine to rev to the moon, and is a more realistic "step" I could see GM making for this new engine, but unfortunately, we know this is not the case, at least on the base car, as the base car still only revs to 6500 rpm according to the dash photo leaked.
Last edited by bbbvettes.com; 05-26-2019 at 02:33 PM.
I looked closely and it is hard to tell because with idlers the direction of the chain could in a wide variety of directions.
They showed just enough to get us going.
What we know from picture.
16 Lifter bores
16 Lobe cam
two timing chains
what appears to be cam phasing
I do not see any other possibility as a two cam in block configuration would require 48(3 valves) or 64(4 valves) pushrods. 16 is already too many.
I followed your initial entry and the hypothetical use of a combination of an exhaust cam-in- block and two intake cam-in-head(s). I'm not sure if you are suggesting it is 3 valve/cyl, in the XV8 concept, or a 4 valve/cyl. If I understand you, I think that would require an inboard exhaust configuration. I can't envision the cylinder head real estate to have a pushrod cross over/under an inboard intake system. It does not seem to be near as clean as the original XV8.
Your calculation for required lobes/pushrods also lost me. It is either 24 valve or 32 valve
Let me try a simpler (my opinion) interpretation of what we see. Envision the XV8 (3 valve/cyl) configuration with a separate cam-in-block for intake and exhaust. Each would have independent phase advance/retard actuators. It is also almost certain that the lifters allow for cylinder deactivation strategies. The XV8 shows a twin rocker arm actuating 2 intakes per pushrod. However, we think we see two lobes per cylinder in the front bay.
If so, I hypothesize that we have a 3 valve/cyl with separate lobes/lifters/pushrods/rockers for each intake valve. With individual lifter deactivation, the possible strategies go nuts. It is also possible to throw in the old Mechadyne multi piece cam for to provide phase control between the 2 intake valves lobes. Keep in mind that intake valve sizes (small and large?) injector location, plug location, and chamber shape are all design variables too.
The other discussion about tossing valves and closing mechanisms is beyond practical (and therefore not desirable) from my perspective.
05-25-2019, 11:37 PM
