FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: Leny Mason on February 25, 2018, 04:45:05 PM
-
I need some expertise on valve spring Pressure naturally aspirated versus super charged, my Cammer has stock cams and I need to know what spring pressure would work the best it is super charged and Bret said Jay may know or some one else, thanks Leny Mason
-
A cammer won't require as much valve spring as a pushrod engine, NA or supercharged. I'm sure Jay would have info, and also Mr. John Vermeersch. John would have knowledge of the original blown cammer set-ups.
-
On the SBFs with Vortec or Pro Chargers, we found that increasing the seat pressure ~ 20# seemed to work well to 14 psi increase. I can't speak to the SOHC specifically. Also, the exhaust duration was increased 4* on camshafts to compensate for more exhaust blow down time, but found that that was not really necessary because the blowers worked well with stock camshafts and more spring pressure on seats. Also, found that blowers did not really need a special grind because they worked well with typical high performance camshafts. Was more fun to install a blower on a dead stock shortblock and add high flowing heads. Idled smoothly, and sounded stock until you got on it. Joe-JDC
-
Never found increasing spring pressure on a blower deal necessary. Pressure differential between cylinder and int. port doesn't change with boost.
-
My take on this is when the valve is closed, pressure on the back side of the intake valve opposes the valve spring pressure. So, when the intake valve closes it can bounce off the seat due to the supercharger pressure detracting from the valve spring pressure that is trying to keep the valve closed. This effect will show up on the dyno graph just like a valve float condition. On the dyno with my supercharged FE running 17 psi of boost, I lost about 400 usable RPM going from naturally aspirated to supercharged, and I think it was due to that effect, although there's no way to prove that. But when I increased the intake valve spring pressure by 60 pounds, I got the RPM back.
The way I calculated how much additional pressure I needed was to figure out the area of the back side of the intake valve and multiply that by the peak boost pressure. I have 2.25" intake valves in my supercharged engine, so neglecting the area of the valve stem the area of the back of the valve is 1.125*1.125*3.1416, or 3.97 square inches. So, using about 4 square inches and 17 pounds of boost I figured I needed to add 68 pounds of seat pressure to the valve. I added 60, and that solved the problem.
I'm currently revamping that supercharged engine and will be running it on the dyno again sometime in the next few months. I'll see if I can repeat that experiment when I do so, and check to see that the results are the same.
-
My take on this is when the valve is closed, pressure on the back side of the intake valve opposes the valve spring pressure. So, when the intake valve closes it can bounce off the seat due to the supercharger pressure detracting from the valve spring pressure that is trying to keep the valve closed. This effect will show up on the dyno graph just like a valve float condition. On the dyno with my supercharged FE running 17 psi of boost, I lost about 400 usable RPM going from naturally aspirated to supercharged, and I think it was due to that effect, although there's no way to prove that. But when I increased the intake valve spring pressure by 60 pounds, I got the RPM back.
The way I calculated how much additional pressure I needed was to figure out the area of the back side of the intake valve and multiply that by the peak boost pressure. I have 2.25" intake valves in my supercharged engine, so neglecting the area of the valve stem the area of the back of the valve is 1.125*1.125*3.1416, or 3.97 square inches. So, using about 4 square inches and 17 pounds of boost I figured I needed to add 68 pounds of seat pressure to the valve. I added 60, and that solved the problem.
I'm currently revamping that supercharged engine and will be running it on the dyno again sometime in the next few months. I'll see if I can repeat that experiment when I do so, and check to see that the results are the same.
So how do you respond to my above comment? It's not a guess, it's physics...
-
Worked with a mustang shop exclusively for about 15 years during the late '80s and into 2004, and we built some of the quickest and fastest mustangs on the planet during that time. Many magazine articles written on them. Every one with blowers had to have more spring pressure with more boost. Those engines didn't take physics in development training. Not going to argue the point, but experience has proven the need for more spring pressure to keep the valve train from killing itself under boost. Joe-JDC
-
Also watch your carb return springs, if applicable. Watched a guy crunch a brand new car because he could not shut it down in the burnout. Blower draw held the blades open and he did freak and didn't go for the kill switch.
-
Worked with a mustang shop exclusively for about 15 years during the late '80s and into 2004, and we built some of the quickest and fastest mustangs on the planet during that time. Many magazine articles written on them. Every one with blowers had to have more spring pressure with more boost. Those engines didn't take physics in development training. Not going to argue the point, but experience has proven the need for more spring pressure to keep the valve train from killing itself under boost. Joe-JDC
lol...never mind.
But WHY did they need more pressure?
It wasn't boost.
More boost in the induction, more boost in the cylinder when the valve closes. The pressure differential never changes with more boost.
Think about it.
-
How do you know the differential pressure is the same? I'm not saying you're wrong, and I get that there's more pressure in the cylinder to counteract the higher pressure in the intake. But is it exactly the same as naturally aspirated?
paulie
-
How do you know the differential pressure is the same? I'm not saying you're wrong, and I get that there's more pressure in the cylinder to counteract the higher pressure in the intake. But is it exactly the same as naturally aspirated?
paulie
If your intake port is keeping your intake valve open because of pressure, are you not closing the valve too soon? Hopefully when you close tine intake valve, you've put as much air into the cylinder as you can, whether it's @ atmospheric or 45# of boost. Pressure delta should be zero or very close.
I think a lot of people "assume" the pressure behind the valve thing because it's somewhat intuitive but they fall short of thinking about the other side of the valve. If adding spring pressure to a boosted deal "makes more power", it's somewhere else.
-
Scott, I see your point, I'm just relaying my actual dyno results. Maybe at high RPM the boost pressure doesn't completely fill the cylinder, so that a pressure differential does exist? Things are happening pretty fast at 7000 RPM. I'm not sure on the actual cause, but I know that more spring pressure was needed on the intake valve to get my engine back to the NA redline.
-
If your intake port is keeping your intake valve open because of pressure, are you not closing the valve too soon? Hopefully when you close tine intake valve, you've put as much air into the cylinder as you can, whether it's @ atmospheric or 45# of boost. Pressure delta should be zero or very close.
I think a lot of people "assume" the pressure behind the valve thing because it's somewhat intuitive but they fall short of thinking about the other side of the valve. If adding spring pressure to a boosted deal "makes more power", it's somewhere else.
That makes a lot of sense. Here's another one for you that kind of makes you scratch your head at first.....
I was modeling some rods for an aluminum rod company in college. We did some studying on a supercharged motor rod, and an NA rod. We were trying to compare the two so they were for the same displacement, only parameter change was boost vs no boost. Before getting a hold of the rods, I was assuming that the supercharged motor rod would be much more substantial, wrong! The supercharged rod was lighter and had less beef to it. I was puzzled and I asked him about it. He explained that the added boost in the engine helps keep the rods in a compressed state, rather than rapidly swinging between compression and tension. So the supercharged motor made more power, but actually needed less rod.
-
If your intake port is keeping your intake valve open because of pressure, are you not closing the valve too soon? Hopefully when you close tine intake valve, you've put as much air into the cylinder as you can, whether it's @ atmospheric or 45# of boost. Pressure delta should be zero or very close.
I think a lot of people "assume" the pressure behind the valve thing because it's somewhat intuitive but they fall short of thinking about the other side of the valve. If adding spring pressure to a boosted deal "makes more power", it's somewhere else.
That makes a lot of sense. Here's another one for you that kind of makes you scratch your head at first.....
I was modeling some rods for an aluminum rod company in college. We did some studying on a supercharged motor rod, and an NA rod. We were trying to compare the two so they were for the same displacement, only parameter change was boost vs no boost. Before getting a hold of the rods, I was assuming that the supercharged motor rod would be much more substantial, wrong! The supercharged rod was lighter and had less beef to it. I was puzzled and I asked him about it. He explained that the added boost in the engine helps keep the rods in a compressed state, rather than rapidly swinging between compression and tension. So the supercharged motor made more power, but actually needed less rod.
This is very true, especially on turbo engines where there is constant pressure even @ overlap.
-
Over the years, I've discussed the use of aluminum rods with the manufacturers on several occasions. Another characteristic of the aluminum is that it's less rigid than steel. I've been told that the 'cushioning effect' of the aluminum is of benefit. Early aluminum rods were known to stretch whenever a car was 'motored' down---pulling the big end egg-shaped, to the detriment of the bearing shells. Putting more 'meat' in the rod cap and providing a 'pin' for the shell all helped. I've never seen an aluminum rod with less 'bulk' than its steel counterpart.
KS
-
On shutdown, I was told long ago the worst thing to do is to snap the throttle closed very quickly as that contributed to rod stretch. Instead, door slammer or injected dragster, we always motored down a tad (say 1/2 throttle closing) before closing the throttle all the way.
-
It's not a guess, it's physics...
Maybe someone just forgot to tell the engine about this? Sometimes they just don't listen very well ;D
Just a guess, but we've all seen the Kaase 'finger' video, where reversion has such a dramatic effect. Then there is the port velocity slamming into the valve as it closes. It may have a more pronounced effect when boost is added. Just because we don't understand why something happens, doesn't mean it isn't happening.
-
How do you know the differential pressure is the same? I'm not saying you're wrong, and I get that there's more pressure in the cylinder to counteract the higher pressure in the intake. But is it exactly the same as naturally aspirated?
paulie
If your intake port is keeping your intake valve open because of pressure, are you not closing the valve too soon? Hopefully when you close tine intake valve, you've put as much air into the cylinder as you can, whether it's @ atmospheric or 45# of boost. Pressure delta should be zero or very close.
I think a lot of people "assume" the pressure behind the valve thing because it's somewhat intuitive but they fall short of thinking about the other side of the valve. If adding spring pressure to a boosted deal "makes more power", it's somewhere else.
That is a good explanation and seems reasonable. Especially when you consider that the piston is on the way up at intake valve closing, creating more pressure to keep the valve closed Like Doug, I wonder if there is more going on though? An intake manifold is a chaotic place with all those valves opening and closing.
paulie
-
It's not a guess, it's physics...
Maybe someone just forgot to tell the engine about this? Sometimes they just don't listen very well ;D
Just a guess, but we've all seen the Kaase 'finger' video, where reversion has such a dramatic effect. Then there is the port velocity slamming into the valve as it closes. It may have a more pronounced effect when boost is added. Just because we don't understand why something happens, doesn't mean it isn't happening.
People mistake boost with an increase in airflow. While, yes, there is that, the more significant part of boost is increased air/fuel density. Remember...boost is a measurement of restriction, not an indicator of airflow. Airflow, as in CFM, does not increase like some may think it does.
I always thought the finger video wass showing the return pulse wave from the moving column of air hitting the closing valve, not reversion.
-
It's not a guess, it's physics...
Maybe someone just forgot to tell the engine about this? Sometimes they just don't listen very well ;D
Just a guess, but we've all seen the Kaase 'finger' video, where reversion has such a dramatic effect. Then there is the port velocity slamming into the valve as it closes. It may have a more pronounced effect when boost is added. Just because we don't understand why something happens, doesn't mean it isn't happening.
People mistake boost with an increase in airflow. While, yes, there is that, the more significant part of boost is increased air/fuel density. Remember...boost is a measurement of restriction, not an indicator of airflow. Airflow, as in CFM, does not increase like some may think it does.
I always thought the finger video wass showing the return pulse wave from the moving column of air hitting the closing valve, not reversion.
I agree with you Scott, I thought it was the valve movement too
I haven't wrapped my head around your comment that pressure is equal though on each side of the valve.
- Pressure differential has charge moving into cylinder as piston drops creating a depression. If pressure was equal, there would be no cylinder fill.
- Valve closes at somewhere after BDC where piston is starting upward, if pressure was rising near valve seat because of that change in the cylinder, there would be reversion, but boost still overcoming it, so still, pressure differential favoring manifold pressure (and in a NA motor, atmospheric pressure plus charge momentum
- Intake valve closes, pressure at valve should spike, although I'd say it's sort of like an damper as it will rise, the next one in firing order should reduce, so I would expect the valve to see some, but not all
Now, that is looking at one or two cylinders, what I have a hard time wrapping my head around is each cylinder doing that in order. However, physics (and atmospherics as an aviator) tells me, there is always a lower pressure on one side or the air would not move, regardless of it being atmospheric pressure or un-naturally aspirated
-
To move air you got to have a wavemotion of high and low
pressure areas i was thought by my old physic teacher.
Wavelength dependent of airspeed, tubelenght, etc.
Sound is nothing more than air moving at a specific wavelength
So if you get a low pressure area behind the valve and a high
pressure area i front of the valve maybe it forces the valve open
A blower i think would create high amplitude on the waves
If some one understand what I'm try to say in my bad English
-
The goal is to fill the cylinder. The only way that can happen is to create a pressure differential (delta). As soon as that pressure delta is equalized, cylinder filling is done. We need to close the valve, now. Any earlier and we cheat ourself out of some cylinder filling and any later, the pressure starts rising in the cylinder (because of piston movement) and we're giving up cylinder filling and going backwards. That's reversion. Intake valve closing is critical.
-
It's not a guess, it's physics...
Maybe someone just forgot to tell the engine about this? Sometimes they just don't listen very well ;D
Just a guess, but we've all seen the Kaase 'finger' video, where reversion has such a dramatic effect. Then there is the port velocity slamming into the valve as it closes. It may have a more pronounced effect when boost is added. Just because we don't understand why something happens, doesn't mean it isn't happening.
There are additional physics at work here besides just airflow. I've done work on shock waves and their effect on induction and exhaust systems. In a supercharged engine, the induction air is more dense. This will speed up and often amplify the shock waves.
The reason tuned intake runners work is that the opening of the intake valve generates a low-pressure (rarifaction) shock wave. This shock travels up to the plenum, where it reflected back towards the valve. The reflection changes the shock into a pressure wave. If everything is perfect, this shock hits the intake valve just as it's closing, forcing a bit more charge into the cylinder.
Long runners work at lower rpm because the time between opening and closing the valve is longer. You need a longer pipe for the wave to travel up and back at the speed of sound. As rpm goes up, you need less and less time so the ideal pipe gets shorter and shorter.
Now back to a supercharged engine. I haven't spent much time with them, but a more dense charge will tend to create more energetic and faster shock waves. It seems likely that at certain rpm the stronger shocks are hitting the backs of the intakes at the wrong time, potentially bouncing them. That would jibe with test results I've seen like Jay's.
Heo's got the right idea!
-
Wave motion does not move the air. Wave motion is a result of the valves opening and closing, and as you stated, return waves from the ends of the runners in the plenum. Air movement is from pressure differential.
A closed intake valve isn't going to get opened prematurely by a shock wave or boost pressure. Even mild engines have more seat pressure than that. An open valve isn't going to be held open longer than it's supposed to be or be kept off it's seat by a shock wave or boost pressure. Like I said, if adding spring pressure seems to solve a "boost" issue, it's something else, not boost and not shock waves or energy pulses.
Look at spin tron testing. Look at the valve train on a 11k rpm, 1400+hp Pro Stock engine. Imagine the wave energy in the runners in that engine with a 2.5+ intake valve (thinking area)!! It's tested with zero induction dynamics and they make zero compensation with spring pressure for that combination. I worked at (top fuel) Alan Johnsons for almost 5 years. Learned a little about boost and cylinder heads. Don't remember ever adding spring pressure for more boost.
Not trying to say I'm right, everyone else isn't. Just sharing thoughts and experience.
-
Am I allowed to agree and disagree at the same time?
A boosted engine certainly has a significant increase in cfm/airflow. Thats because all of the common cfm measurements are assuming a given amount of test pressure to generate comparative data. The chosen test pressure may well have absolutely nothing to do with the actual dynamics in a running engine - they just needed some sort of a "number" to commonize the data. Its always "cfm at xx.x".
That spinning thingamajig in the inlet tract is gonna increase the test pressure in the real engine by a bunch going from base atmospheric to some increment of that - or above. The cfm number gain might be modest on one package versus another, but the xx.x" will change. I will definitely agree on the boost comment - it is a measurement of restriction - not of airflow. Push harder against a given orifice and the boost measurement will go up even though the gain in airflow might be much less on a percentage basis.
Might want to approach Mr. Conley with a bit of caution. He has had access to some rather spendy test equipment over the years, and often screws up these threads by providing facts backed up by test data. Makes him really hard to argue with even when you want to....
-
+1 :)
KS
-
Not trying to stir anything up, and an engineer with a lot of test equipment does not become a Kaase. That said, to a Top Fuel engine with 450 lbs seat pressure, the effects of 60 psi boost is crumbs (shock or no shock). All of that spring pressure is needed to keep that valvetrain stable at 8,200 rpm.
For our "normal" engine builds, there's plenty of anecdotal evidence supporting the need for stiffer valve springs on supercharged engines. Here's one good example:
http://magnumpowers.com/valve-spring-data/
flame on!
-
Yes, to further what Barry stated.....we should treat Mr. Conley like E.F. Hutton. We he talked.....people listened. Mr. C opines with much knowledge and experience. When really smart people don't know, they are not afraid to admit it, and when they make a statement, it is often hard to debunk.
With all that said, we gotta get back to Leny's original question. He wants to know how much spring on a stock cammer with those 1.3 ratio rockers and stock cams, with a blower. I don't know that answer......I just threw out two things to consider......one, that it IS a cammer with low ratio rockers and no pushrods......and two, that it is boosted. Somebody with experience should give Leny an idea. I am not the right guy, but I'm gonna say 175# seat and 450# open if you turn it 7000+. I'd say 125/375 at 7000 or less. It is a mildly educated WAG based on what I have seen over 40 years of this, and knowledge of what was available when those cams were new and men with big balls put blowers on them. Somebody agree or disagree and tell us why.
Back to the discussion of it......with everything I do regarding the intake charge, I think of that whole "thing" as a freight train, that we have to convince to start rolling down a hill. We can pull it a little (maybe with a good header and some overlap, or we can push it a little (maybe with a big plenum and steep runner), or we can really load those freight cars, and more of them, and then make the wind blow to get the train moving. The last example being the blower.... wind and a heavy bunch of freight cars (Mr. C's comment on more dense). So the train gets moving....it is a heavy train with lots of cars....then we drive another bigger train into it, head on(intake valve closing). You see my analogy..... it takes a bigger train coming the other way to stop the first one in it's tracks. I'm just a Hillbilly (capital H), but I live at the foot of a mountain, and there is a train track out by the river here. It keeps me thinking about the fact that the charge has mass and we have to control it. We gotta do stuff to make it move, and then control it when we want it to stop.
-
It's hard to argue against data and experience, even when the physics dictate otherwise. It's not that the physics are wrong, it's just that the wrong formula/method/hypothesis is being used to correlate it.
In situations where the cam has not changed, the peak hp rpm has not changed, but boost has been added and the valve springs are giving up, it's hard to pull anything else away from that. There has to be *something* causing the loss of valve control and it could be that the guys who are not seeing it are possibly over-springing to begin with.
-
Don't remember ever adding spring pressure for more boost.
My guess is that the spring requirements necessary to turn 9000-10000 rpm would take care of whatever spring requirements needed by a boost increase.
The situations provided by Joe Craine and Jay Brown probably offer up a scenario where the spring requirements were marginal at best (certainly that's the case with factory 5.0 stuff, where the engine was done at 4500 rpm) and the addition of forced induction found the limits.
-
I always thought the finger video wass showing the return pulse wave from the moving column of air hitting the closing valve, not reversion.
My bad for using the wrong terminology. Mr. Conley and Mr. Patrick did a better job of putting into words, what I was trying to get across. That's a LOT of momentum for a valve to stop. And like Brent said, since we typically don't like to over-pressure on springs, for obvious reasons of wear and stress, I think you reach that point of "not enough" fairly quickly.
-
One of the things that tends to muddie the waters when talking about SOHC valve spring pressure is that the original factory valves were really, really light, hollow stem and less than 100 grams each. The factory spring pressure was about 110 on the seat and 300 over the nose, and with the big ramps on the factory cams the engines would go to 7500+ RPM with that package. When I was running the Manley custom valves that I used as SOHC replacements, the intake weighed almost 150 grams, and the exhaust was about 145 if I recall correctly. With an aggressive lobe from Comp I needed 240 on the seat and 600 over the nose to get to 7000 RPM; it needed more to go higher. Bill has some of the spintron data on the testing he did for me, which is pretty impressive actually.
Ferrea makes a lighter weight valve, around 120 grams if I recall correctly, and they won't need as much spring pressure to go to 7500 RPM, something like 175 on the seat and 450 over the nose. But those valves flow poorly compared to the Manleys, and cost a bunch of horsepower in a max effort application.
I think the springs Leny needs will depend on the cam profile, the weight of the valves, and how much boost he wants to run. Leny, can you give us that information?
-
If you think of the boost as time instead of psi, then the amount of air/fuel goes in much quicker under boost. On the SBF valves which are much lighter than FE valves, it is not uncommon to increase seat pressure 20-45# for boosted applications, as I stated earlier. Experience over theory. Joe-JDC
-
cam # is LH C5AE-6A274-A RH C5AE-6250-C Dennis sent me the specs a while ago 22-40-58-4 @.100" cam lift, 328/328 Dur112 O/L Theoretical .565" lift at zero lash and 10 # boost I will weigh the valves and let you know, thanks every one for the input some of it way over my head. Leny Mason
-
thanks every one for the input some of it way over my head. Leny Mason
Don't feel like the Lone Ranger Leny. But I must say I love stretching my little noggin like this.
-
cam # is LH C5AE-6A274-A RH C5AE-6250-C Dennis sent me the specs a while ago 22-40-58-4 @.100" cam lift, 328/328 Dur112 O/L Theoretical .565" lift at zero lash and 10 # boost I will weigh the valves and let you know, thanks every one for the input some of it way over my head. Leny Mason
Looks like the factory spec cam info.
-
Nice explanation Jay on the unique nature of the Cammer.
I'm still amazed, even with light valves, big ramps, etc. that at only 110 lbs. closed/330 open, the engine would turn 7,500 rpm! Amazing considering it was a near "90 day wonder" as a replacement head design to the existing straight valve FE 427 block. What a replacement!
quote author=jayb link=topic=5679.msg61453#msg61453 date=1519750613]
One of the things that tends to muddie the waters when talking about SOHC valve spring pressure is that the original factory valves were really, really light, hollow stem and less than 100 grams each. The factory spring pressure was about 110 on the seat and 300 over the nose, and with the big ramps on the factory cams the engines would go to 7500+ RPM with that package. When I was running the Manley custom valves that I used as SOHC replacements, the intake weighed almost 150 grams, and the exhaust was about 145 if I recall correctly. With an aggressive lobe from Comp I needed 240 on the seat and 600 over the nose to get to 7000 RPM; it needed more to go higher. Bill has some of the spintron data on the testing he did for me, which is pretty impressive actually.
Ferrea makes a lighter weight valve, around 120 grams if I recall correctly, and they won't need as much spring pressure to go to 7500 RPM, something like 175 on the seat and 450 over the nose. But those valves flow poorly compared to the Manleys, and cost a bunch of horsepower in a max effort application.
I think the springs Leny needs will depend on the cam profile, the weight of the valves, and how much boost he wants to run. Leny, can you give us that information?
[/quote]
-
When the piston starts down on the intake stroke, it creates a vacuum, and with the reduced timing, and stuffing more air into the cylinder, it takes more seat pressure to keep the intake valve closed until the camshaft opens it. Too much boost would slam the valve open too quickly and open up the clearance on the rocker arm to valve stem, causing a pushrod to be thrown. Increasing the seat pressure assures the lifters open the valve in a controlled manner. Joe-JDC
-
When the piston starts down on the intake stroke, it creates a vacuum, and with the reduced timing, and stuffing more air into the cylinder, it takes more seat pressure to keep the intake valve closed until the camshaft opens it. Too much boost would slam the valve open too quickly and open up the clearance on the rocker arm to valve stem, causing a pushrod to be thrown. Increasing the seat pressure assures the lifters open the valve in a controlled manner. Joe-JDC
Except for the fact that most intake valves start opening before the piston reaches TDC.
-
I'm guessing that Mr. Joe Craine is aware of overlap, and the fact that the intake valve is opening before TDC. He probably also knows that the exhaust port scavenges the system, and that after TDC, when the exhaust finishes closing, and the train is already moving, that the downstroke does pull on the intake port. So, his statement that boost can nudge on the intake valve is 100% correct. I like Jay's logic on valve area vs. boost pressure. Seems like a good way to estimate the need. I'd bump the number a little just to be safe.
-
I'm guessing that Mr. Joe Craine is aware of overlap, and the fact that the intake valve is opening before TDC. He probably also knows that the exhaust port scavenges the system, and that after TDC, when the exhaust finishes closing, and the train is already moving, that the downstroke does pull on the intake port. So, his statement that boost can nudge on the intake valve is 100% correct. I like Jay's logic on valve area vs. boost pressure. Seems like a good way to estimate the need. I'd bump the number a little just to be safe.
Not going to agree with that...not if the valve is open. And nothing "pulls" on the intake port, especially in a boosted app. If we're going to describe what's going on, lets at least be accurate about it. Atmospheric pressure, or boosted pressure does the work pushing the air from high to low pressure. Sorry...pet peeve of mine.
-
Well, I was writing figuratively about a natural aspirated situation, and then adding boost. If you don't think the exhaust port pulls a signal on the intake tract during overlap, there is just no point in my trying to convince you. I don't know you from Adam's house cat, Mr. Foxwell, but I do know that you are fairly new on this forum, and you seem to have a way of attempting to argue with some pretty accomplished guys (absolutely excluding my dumb ass) here, on a regular basis. I don't wish to argue with you, and I certainly don't care if you agree with anything I post, but there are some guys on here who know a heck of a lot about what they post, and I don't think you help yourself look smart by challenging some of those guys. Just my opinion.
-
It is getting really old having every thing I add to this forum torn apart as if I didn't know what I am talking about. I am tired of this. I have a degree in Automotive, Aircraft Maintenance, and Business, and was an Automotive instructor for a Junior College and Master Instructor while serving in the USAF at retirement. I don't have a habit of posting anything that is conjecture, but from experience. I have been building and racing Fords since 1962, and bought my first new Ford in 1966. I respect Jay and his forum members and have always tried to add in a positive way to the folks here, but I will not respond any more to anything you say, Scott. Joe-JDC
-
Well, I was writing figuratively about a natural aspirated situation, and then adding boost. If you don't think the exhaust port pulls a signal on the intake tract during overlap, there is just no point in my trying to convince you. ...
Blair is absolutely correct. During the overlap phase, the exhaust flow momentum will create a pressure differential that the intake port sees. This is especially strong if you have a tuned exhaust primary tube.
Two-stroke engines wouldn't work very well if it wasn't for this...
-
LOL...OK, Joe. ::)
-
Well, I was writing figuratively about a natural aspirated situation, and then adding boost. If you don't think the exhaust port pulls a signal on the intake tract during overlap, there is just no point in my trying to convince you. ...
Blair is absolutely correct. During the overlap phase, the exhaust flow momentum will create a pressure differential that the intake port sees. This is especially strong if you have a tuned exhaust primary tube.
Two-stroke engines wouldn't work very well if it wasn't for this...
That's not what Blair said, and I have more respect for him than I do anyone else here. I understand exactly what happens during overlap. It's semantics, but it's also true; nothing is being pulled. A pressure differential is created and high pressure moves to low pressure. Learning this and understanding it helped my understanding of the ICE in a lot of ways.
I'm really sorry so many of you are so thin skinned. Nothing I say is personal yet it sure seems to be taken that way. Lol...you think THAT doesn't get old?
-
Hey Leny, is this engine stroked?
-
cam # is LH C5AE-6A274-A RH C5AE-6250-C Dennis sent me the specs a while ago 22-40-58-4 @.100" cam lift, 328/328 Dur112 O/L Theoretical .565" lift at zero lash and 10 # boost I will weigh the valves and let you know, thanks every one for the input some of it way over my head. Leny Mason
My exhaust valves weigh 148.7 the intake weigh 165.9 just like Jay's Thanks. Leny Mason
-
Hey Leny, is this engine stroked?
it is 4.125 stroke Leny Mason
-
I agree with Scott that "push" or "pull" is semantics. Molecules move from higher pressure to lower pressure. It doesn't matter if you call it push or pull. That's because the higher pressure molecules are closer together and hitting each other with more energy. It's like a "break" in a pool game. Molecules that are close together (before the break) are given energy from the cue ball then they move further apart and lose energy. It's all about increasing entropy in the universe and our inevitable death and dissolution. We can harness the process to go fast and have fun with our FE's , but we are all going to end up lying in the dirt in the end. Sorry guys. :)
JMO,
paulie
edit: I didn't meant to leave inertia and kinetic energy out of the picture. Some of you have mentioned it and it's a player, too.
-
Sorry again guys, but Inertia......it's analogous to our lives, too. Inertia is like the decisions we made in the past. We may realize that they weren't correct and we want to change them, but once we realize they weren't correct, it takes time to change them. So we try, but it's too late. physics doesn't let us change incorrect decisions. The repercussions live with us and we can't go back and fix it. Same thing with valve events. There's one perfect set of events and we are not likely to get it right. Really smart guys can get it close. No, I'm not drunk or stoned. Crawling back under my rock.
JMO,
paulie
-
Hey Leny, is this engine stroked?
it is 4.125 stroke Leny Mason
Those are heavy valves, Leny. The cam sounds like it is a copy of the stock cam, which has pretty gentle ramps, but you will need some spring to make those valves follow the lobes. I think I'd be looking at spring pressures of around 220-240 on the seat, and about 500 open.
-
I have an issue with this whole discussion prior to the shiny object of overlap and believe you need a little more closed spring pressure for a blower
- Pressure is acting on the closed valve, period, and that is pounds per square inch, normally atmospheric, but with 14 lbs of boost that's closer to 28 lbs per square inch pushing every direction, including down on the valve which is greater surface area than 1 square inch
- As the valve opens, the differential pushes the air in (same with naturally aspirated and of course a negative exhaust pulse also causes more of a depression causing even more movement)
- The charge continues to move through the valve events, if it equalized, before that, it would slow and likely drop fuel out of suspension, if nothing else it would just stop moving.
- Even if you COULD time the valve to close at exactly pressure equilibrium, move the throttle and it would no longer be there, it would only be for a specific RPM, load and exhaust harmonic
- The issue is, the valve closes before compression builds to a significant amount, and why we need a slight increase in closed pressure, once the piston comes up, it isn't needed, compression is there, but not at the beginning of the event (this IS what DCR considers as the start of the stroke, now this is not a DCR discussion, but important to understand that you need a closed valve to make compression).
- The increased closed pressure to prevent bounce, not sealing it shut during peak compression
- Now you could say that the increased cylinder pressure due to the huffer offsets it, but a valve with 3 square inches of surface area, that would be 28 *3 or 64 lbs, and pre-combustion, I would expect cylinder pressures to be lower than that when the valve initially bounces
- Now, if you already have excess closed spring pressure, OK, but IMO, the minimum closed spring pressure for a blown engine is slightly higher than the closed spring pressure for the same naturally aspirated engine
I'll duck back out, but IMHO, add some closed pressure over an equally spec'd naturally aspirated combo
-
I remember one time I was having an oil consumption issue with my 428 FE. It ended up that one of the locating pins we had in the intake manifold and heads was too close to the intake port and had broken through. It acted like a straw, pulling oil in from the head to the intake port. The crazy thing is it was just in one port, but the oil moved all over the place. There was oil from this leak over in the other bank of the engine and the other side of the intake manifold. This really opened my eyes to how crazy the flow in an intake manifold can be. It's not a linear and smooth flow from the air cleaner, through the carburetor, and down through the intake ports. There's a whole lot back and forth chaotic action going on. I'm not sure, but I think adding boost may change things. It may make it more chaotic or less, but I bet it changes things. It'd be amazing if it changed nothing.
JMO,
paulie
-
I think everybody would agree that experience trumps theory every time. If our experience (test data) doesn't match our theory, then the theory has to change, not the data. That's assuming the data is good. I'm guessing it is in this case.
JMO,
paulie
-
Hey Leny, is this engine stroked?
it is 4.125 stroke Leny Mason
Those are heavy valves, Leny. The cam sounds like it is a copy of the stock cam, which has pretty gentle ramps, but you will need some spring to make those valves follow the lobes. I think I'd be looking at spring pressures of around 220-240 on the seat, and about 500 open.
Thanks everyone, if my valves are to heavy should I find some lighter ones, if that spring pressure may cause other problems it's not the first time I got the wrong parts. Leny Mason
-
Those spring pressures shouldn't cause you any trouble.
-
Thank that will save some money. Leny Mason
-
I think everybody would agree that experience trumps theory every time. If our experience (test data) doesn't match our theory, then the theory has to change, not the data. That's assuming the data is good. I'm guessing it is in this case.
JMO,
paulie
True, but Physics and math don't lie. If our "experience" doesn't match the math and physics, then we're not looking at the experience correctly and need to go back and re-evaluate. I've had to do this many times. Sometimes the changes we make aren't changing what we think they're changing.
-
So I wonder what we're missing. Or did somebody say it already and I just missed it?
paulie
-
True, but Physics and math don't lie. If our "experience" doesn't match the math and physics, then we're not looking at the experience correctly
[/quote]
Or the math and physics are not refined enough to allow for the variables of a running engine.
-
True, but Physics and math don't lie. If our "experience" doesn't match the math and physics, then we're not looking at the experience correctly
Or the math and physics are not refined enough to allow for the variables of a running engine.
I'd say some of the guys I work with -who are WAY above my pay grade- and the engineers at the Big 3 might not agree with that statement.
The physics and math that applied to some of the very first steam engines a hundred years ago are still the same today. Before anything, an engine is just an air pump.
-
I've been watching everyone go back and forth and it's been a pretty interesting conversation, one that I have no idea the answer to. I got a call this morning from a friend about something unrelated and figured he was the perfect person to ask what the deal is here. He builds elite level tractor pull engines. Which means, he'll build 600-700 cube Hemi-headed NA motors, and at the same time build inline 6 tractor motors with 3 turbos that build 100-140 pounds of boost.
I asked him about this and I got kind of a chuckle. He said yes this is a familiar conversation. If you think through the cycles theoretically, boost won't have an effect on valvetrain control. HOWEVER, this is only for one particular point in the RPM range where everything is performing exactly as expected and the cylinder is filing just as you want it. If you're setting the cam up for a street driven engine, you're likely compromising away from that optimal point as well.
There's no quantitative answer here, but I think what this means is the answer is not zero added spring pressure, but it's not boost pressure multiplied by valve surface area added spring pressure either. There's a point somewhere in between that needs to be found, which can take care of those shoulder situations where things aren't perfect. The generic answer I got was "we don't go crazy with spring pressure".
And in an attempt to make things more kumbaya..... I will say that I've had the chance to talk with quite a few people from this forum, outside of this forum, and there are some real good guys floating around here. Even though Scott may have the keyboard personality of Niki Lauda sometimes, I don't think Niki Lauda is a bad guy.
-
I've been watching everyone go back and forth and it's been a pretty interesting conversation, one that I have no idea the answer to. I got a call this morning from a friend about something unrelated and figured he was the perfect person to ask what the deal is here. He builds elite level tractor pull engines. Which means, he'll build 600-700 cube Hemi-headed NA motors, and at the same time build inline 6 tractor motors with 3 turbos that build 100-140 pounds of boost.
I asked him about this and I got kind of a chuckle. He said yes this is a familiar conversation. If you think through the cycles theoretically, boost won't have an effect on valvetrain control. HOWEVER, this is only for one particular point in the RPM range where everything is performing exactly as expected and the cylinder is filing just as you want it. If you're setting the cam up for a street driven engine, you're likely compromising away from that optimal point as well.
There's no quantitative answer here, but I think what this means is the answer is not zero added spring pressure, but it's not boost pressure multiplied by valve surface area added spring pressure either. There's a point somewhere in between that needs to be found, which can take care of those shoulder situations where things aren't perfect. The generic answer I got was "we don't go crazy with spring pressure".
And in an attempt to make things more kumbaya..... I will say that I've had the chance to talk with quite a few people from this forum, outside of this forum, and there are some real good guys floating around here. Even though Scott may have the keyboard personality of Niki Lauda sometimes, I don't think Niki Lauda is a bad guy.
IMO that was a real good answer from your friend.
LOL...I don't mind being compared to Niki Lauda. I'll almost take that as a compliment. ;)
Sometimes "we" respond harshly to those who don't respond objectively to us. I'm a work in progress. Always will be.
-
My opinion is that the better analogy to use is billiard balls, or marbles, rather than a freight train. A freight train starts and stops VERY slowly. What's happening in an intake manifold is lightning quick and very chaotic. That's what I think anyway. I don't have any real empirical evidence to back that up. It's still think it better describes what is going on. Okay, maybe a long line of billiard balls which is kind of like a train. :)
JMO,
paulie
-
OK most of you are way above my knowledge of valve events so does the weight of my valves matter a lot thanks Leny Mason
-
Lol, Leny I'd love to have a beer with you.
-
OK most of you are way above my knowledge of valve events so does the weight of my valves matter a lot thanks Leny Mason
Valve weight always matters....however, you're not breaking new ground here. Unless you're planning on turning some crazy rpm where very gram counts, I'd just stick with teh recommendations of the guys who have worked with these heads and know what to expect. If this was a pushrod engine with rocker arms, I could give you a recommendation but I have zero experience with overhead cam valve train like this. I deal with big (2.35"), heavy, stainless valves, big 7/16 to 1/2" pushrods and rockerarms with >.800" lift and run that setup past 7500rpm with all the right parts. THAT is a heavy valve train.
-
So, let me summarize pages and pages of high-falootin' monkey talk thusly. I should rebuild a 360 with stock crank, rods, and pistons. Add a GT/CJ cam with 120 pounds on the seat just for giggles. Streetmaster, turbo at 10 lbs. Finished. Go out and beat on it profusely while you rich guys with Cammers discuss physics. I got that right?
-
My monkey can beat up your monkey. Just sayin...
paulie
-
Speaking of how stuff moves around in an intake manifold, we pulled the head off an intake valve years ago in the TP, during a pass at Milan. Part of the valve head beat up #6 cylinder, and part of it was jammed through the top of the piston in #2. Yet #6 fires AFTER #2 and it was #6 that lost the valve. ???
KS
-
How true! It is somewhat amazing when losing a valve where all the parts and pieces end up. Often, the wasted intake pieces end up in another cylinder or two, proving just how turbulent the intake tract can be. I've wondered if it's also more a ricochet
effect than air moving the broken pieces.
Speaking of how stuff moves around in an intake manifold, we pulled the head off an intake valve years ago in the TP, during a pass at Milan. Part of the valve head beat up #6 cylinder, and part of it was jammed through the top of the piston in #2. Yet #6 fires AFTER #2 and it was #6 that lost the valve. ???
KS
-
So, let me summarize pages and pages of high-falootin' monkey talk thusly. I should rebuild a 360 with stock crank, rods, and pistons. Add a GT/CJ cam with 120 pounds on the seat just for giggles. Streetmaster, turbo at 10 lbs. Finished. Go out and beat on it profusely while you rich guys with Cammers discuss physics. I got that right?
FElony, I am not a rich guy it has taken a good part of my life to get the parts to do this that is why I would like to get it right, I know little of what is being argued here I just want it to hold up, sorry you think I am some sort of a rich snob I am far from that, I think most of us are in the same boat, I have a small auto-Machine shop in East Helena Montana that should tell you something. Leny Mason
-
Lol, Leny I'd love to have a beer with you.
Cool, it is a little early here but I guess that would be fine, let me know when and where. Leny Mason
-
Next time I make it to Montana which I do every so often.
-
My monkey can beat up your monkey. Just sayin...
paulie
It's a given considering my monkey is always drunk, and spends his afternoons in the front yard tossing his poop at cars driving by. He's a flinger not a fighter.
-
:o ;D ;D ;D ;D
-
So, let me summarize pages and pages of high-falootin' monkey talk thusly. I should rebuild a 360 with stock crank, rods, and pistons. Add a GT/CJ cam with 120 pounds on the seat just for giggles. Streetmaster, turbo at 10 lbs. Finished. Go out and beat on it profusely while you rich guys with Cammers discuss physics. I got that right?
FElony, I am not a rich guy it has taken a good part of my life to get the parts to do this that is why I would like to get it right, I know little of what is being argued here I just want it to hold up, sorry you think I am some sort of a rich snob I am far from that, I think most of us are in the same boat, I have a small auto-Machine shop in East Helena Montana that should tell you something. Leny Mason
I was being facetious, of course. I think realizing a long-term goal is great, indeed. My intent was to "translate" some of what was being said into a scenario that a grassroots person (I know, very few of them here) might envision as plausible. BTW, I didn't use the word "snob"; you did.
Perhaps my mention of a 360 was a bit of a hijack, but I was actually serious about the combo. Perhaps I'll start another thread. Perhaps. Hard to get people to take me seriously. I wonder why. Perhaps.
-
FElony Once in a while i need to rent your poopslinging monkey. IF he aim where i tell him to ;D ;D
-
FElony Once in a while i need to rent your poopslinging monkey. IF he aim where i tell him to ;D ;D
As my monkey somehow manages to keep up with current events, he just told me he'd be glad to do some battle in Malmo. Just keep him supplied with Jack Daniels, whisper "Globalist liberals" in his ear, and he'll be ready to toss it up. Oh, don't forget to feed him high fiber foods. Ammo in, ammo out, you know.
-
Greate minds thinks alike 8)
-
So, let me summarize pages and pages of high-falootin' monkey talk thusly. I should rebuild a 360 with stock crank, rods, and pistons. Add a GT/CJ cam with 120 pounds on the seat just for giggles. Streetmaster, turbo at 10 lbs. Finished. Go out and beat on it profusely while you rich guys with Cammers discuss physics. I got that right?
FElony, I am not a rich guy it has taken a good part of my life to get the parts to do this that is why I would like to get it right, I know little of what is being argued here I just want it to hold up, sorry you think I am some sort of a rich snob I am far from that, I think most of us are in the same boat, I have a small auto-Machine shop in East Helena Montana that should tell you something. Leny Mason
I was being facetious, of course. I think realizing a long-term goal is great, indeed. My intent was to "translate" some of what was being said into a scenario that a grassroots person (I know, very few of them here) might envision as plausible. BTW, I didn't use the word "snob"; you did.
Perhaps my mention of a 360 was a bit of a hijack, but I was actually serious about the combo. Perhaps I'll start another thread. Perhaps. Hard to get people to take me seriously. I wonder why. Perhaps.
OK that is all right I just wanted you to know I am a long way from rich and I can take a joke. Leny Mason
-
Okay, I just want y'all to know that I like talking about monkeys. Anytime.
paulie
-
(I'm Not Your) Steppin' Stone.
-
(I'm Not Your) Steppin' Stone.
Then why'd you take the last train to Clarksville?
-
(I'm Not Your) Steppin' Stone.
Then why'd you take the last train to Clarksville?
'cuz I'm a Believer
-
(I'm Not Your) Steppin' Stone.
Then why'd you take the last train to Clarksville?
'cuz I'm a Believer
And people say we monkey around?