If 2015 is to be considered Atkinson then so should 11-14 based on the valve events....but you say IVC makes Atkinson not IVO, so Ford is just saying that the cams either don't have enough duration or they still don't open late enough to make them get the effects of Atkinson cycle.
Besides, gaining control of the valve events means we should be more worried about advancing the intake rather than retarding it at part throttle!
All I really want to know is can I use, if it is even there, the atkinson timing to sacrifice some on demand power to increase my gas mileage. For a daily driver that to me is more important. As jfk said we choose to go to the moon and do other things not because they are easy but because they are hard. That's why I got a performance car and am trying to see exactly what kinda mileage I can squeeze out of it. The easy thing to do would be get a prius. Next project get a prius in the ten second 1/4. LOL.
Whether it is Atkinson or not, just retard the intake and increase overlap (retard exhaust even more) in your cruise cells to get the EGR effect. This is what Ford is already doing, you can test if increasing the effect is worthwhile or not and if the car even runs good like that. Even GM has lots of cam retard at cruise, which I normally remove in favor of throttle response. ;-)Originally Posted by murfie
They replied saying for more technical info they refer people to the dealer network. They will have information about the latest technologies. My dealership was telling me to learn it and come back and teach them. They couldn't answer a single question about the simplest thing. Why is my radio in Spanish? how do I change it to English? "Sorry we don't know anything about your new car come back and teach us when you figure it all out."
Any time the intake valve is held open ABDC what you are doing is changing the effective compression ratio. So whether it is with a mild part of the cam or a more aggressive part of the cam you can tune it for more or less effective compression ratio. You could have multiple tunes for different purposes utilizing the new technology that Ford has put in their engines. If it is there it is absolutely genius. Why they wouldn't want their public relations to know this information to brag about it I don't understand. Chevy found a way to disable half the engine for fuel economy and they brag about it. Maybe they stole an idea.
Last edited by murfie; 02-03-2016 at 12:18 PM.
All cams always close the intake ABDC on every car with or without VVT.....
Closing it early by advancing the cam (or just the intake) still closes it ABDC. Look at the 11-14 specs: IVC at full retard is 64.5 ABDC and full advance is 14.5 ABDC @ .050....
The 11-14 is not Atkinson, right? I mean, the valve events are ATDC / ABDC all the time except for heavy load (and only IVO moves to BTDC a little bit), just like the 2015.
That's not all it takes to be Atkinson. The more I read about Atkinson, the more I keep seeing varying lengths of stroke or lengthening of cam duration, both temporarily during the atkinson part of the cycle. We know that neither the stroke length nor the cam duration are variable on our engines. The simple act of moving IVC back and forth doesn't seem to make it Atkinson....
It is there, but it doesn't make the engine an Atkinson Cycle motor "technically" which is why they won't tell you it's an Atkinson motor. It does however utilize effects that could be called Atkinson like.
A lot of manufacturers are moving to VCT doing the exact same thing. They probably don't brag about it because its not anything super new.
I'll use numbers from the Ecoboost Mustang for example, as its what I'm most familiar with
IVO is 371* ATDC (TDC being top of power cycle). This puts it into the intake cycle. Default IVC is 607* ATDC, and this is solidly in the compression stroke (which starts at 540*).
The intake cam can be advanced up to 50*, changing IVO to 321* and IVC to 557*.
557* is still in the compression stroke. You still have a slight amount of reversion that occurs. This is normal, and pretty much every car out there has an IVC into the compression stroke. This strategy is common, and is called the LIVC Strategy "Late Intake Valve Closing". Its common in part load situations for efficiency. The goal is to reduce pumping losses as much as you can, and to do this you want less manifold vacuum. To see why, you need to look at the PV Diagram for an engine. You can read about this stuff here: http://www.mechadyne-int.com/vva-ref...sses-si-engine
This means you always have some air "pushing back" or reverting into the intake manifold.
Via this patent: http://www.google.com/patents/US20130111900 you can see Ford actually tracks this with their VE system.
LIVC has been a common trend for quite a while because of the efficiency benefits. On the Ecoboost Mustang, you actually see the intake cam park at 0* during normal driving part load, and you'll actually see the exhaust cam retard instead of the intake cam moving. This increases part throttle overlap, which helps lower pumping losses as you're manifold doesn't have as much vacuum to perform work against, as well as increase in-cylinder EGR for better emissions. You will be hard pressed to find a single motor that doesn't have LIVC. Pretty much every motor ever uses it because an idealist motor with perfect closing right at the start of Compression has quite high pumping losses.
And yes, this means you change the effective compression ratio, and yes, that means the net effect on the motor is just like an Atkinson motor, having a larger expansion ratio than it does a compression ratio. However, this doesn't make the engine an "Atkinson Cycle" motor. The true Atkinson cycle motor has a shorter intake stroke than it does power stroke. To complicate things, if you add "boost" to this like a supercharger or turbocharger, now you technically have a "Miller Cycle" motor. So while the Coyote would be "Atkinson", the Ecoboost would be "Miller". However, this doesn't necessarily make the motor a set Atkinson/Miller cycle motor. Typically, you only call a motor that if they're actually of that design. Atkinson/Miller motors have variable intake stroke vs exhaust stroke. Technically, we don't have that, we just have variable compression ratios. This is the "Modern Atkinson Cycle".
The nomenclature however is unimportant. Your goal is to reduce pumping losses. To that effect, you will find it difficult. The whole reason for these systems on vehicles in the first place is efficiency. The "Optimum Power" mode is just a benefit they can take advantage of, but the tighter CAFE standards is why even a base model Fiesta has Ti-VCT.
Second, on IMRC, IMRC isn't about reducing this effect. IMRC is to address a different problem. At low RPM and airflow, you have lower flow velocities, which is actually detrimental to combustion efficiency. You need tumble and swirl, and you're lacking this at low velocities. Similar to the "TGV" in Subaru land, you have the IMRC which is designed to increase tumble in the airflow. You actually create a restriction in the intake runner, which causes the velocity to be higher in that local area, and when it diffuses out at the other end you get a nice turbulent tumble pattern. This means more efficiency, which can bump your part throttle response and power in these conditions.
Last edited by Bugasu; 02-03-2016 at 02:05 PM.
If you start analyzing all the details atkinsons original patent then yes no modern engine is an atkinson engine. If you look at it as he did all that just to get his idea of holding the intake valve open longer ABDC patented to change the effective compression ratio and had to get around other patents you can see why they call modern day timing atkinson timing.
Thank you. I think we agree on the timing. I call it Atkinson because that's what they call the timing in hybrid cars and many other cars. The new Tacoma and Lexus cars for examples.
Closing the intake valve at BDC would not be ideal. air is still rushing in and has some compression of itself before it starting being pushed back out into the manifold. so a little late IVC is normal and actually better. 557-540= 17* ABDC thats pretty normal to take advantage of the air rushing in still compressing to fill the cylinder as much as possible. 607-540= 67* ADBC. Your car if its anything like the GT will be cruising at 607 not 557. 67* ABDC is 2/3 of the compression stroke. That's a lot of volume pushed back into the intake manifold. The numbers for the GT are 370-380* IVO and 609-619* IVC. That's at a cruising speed and RPM.
The patent you posted is for blow-through air(reversion) not so much air returning to the intake manifold but actually flowing through the combustion chamber and out the exhaust. blow-through air can be quite extreme in supercharged or turbo charged engines. blow-through air happens during valve overlap as the piston transitions between exhaust stroke and intake stroke. While also impotant it has nothing to do with Atkinson valve timing. IF you want to follow how ford tracks what the IMRC does to air flow you need to follow The ECU programming in this patent http://www.google.com/patents/US20040144166 and the speed density tables in a GT tune. While doing this remember you cant get more air to go through a smaller hole with out FI.
quote from the first paragraph of the patent you posted. Did you even read it?
"However, during periods of valve overlap where both intake and exhaust valves of a cylinder are simultaneously open, it is possible for air to pass directly from the engine intake manifold to the engine exhaust manifold without participating in combustion within a cylinder.Air passing directly from the intake manifold to the exhaust manifold without participating in combustion may be referred to as blow-through."
I understand tumble/swirl in the air flow helps with combustion. They can be created by the valves. Block one off you get swirl. use a butterfly valve as a ramp at both valve you get tumble. If your injectors arent doing a good enough job at misting the fuel then i could see benifits. I don't see how you get more power from less fuel and air unless you change physical things like compression ratio or stroke length. Once the fuel has been sufficiently atomized by the injector turbulence in the airflow just leads to a air pressure drop and causes the engine to make less power. Do the stock injectors not do a good enough job atomizing the fuel? They seemed to be aimed right at the valve or even right into the combustion chamber. That's why GT has OVI open valve injection. IF the injector is doing its job of creating a cloud of fuel then having the air tumble and swirl could actually cause fuel droplets to form which would decrease the the distribution of the fuel in the combustion chamber. You say you need tumble and swirl in low vacuum/rpm situations, The IMRC is open in low vacuum/rpm situations. A low vacuum/ RPM situation is when the air is moving the slowest through the engine. High vacuum/ low RPM you can hear the air making a high pitched noise as it is moving very fast through the manifold. Not a large volume of air but its moving very fast. The key to more power is more air volume not speed that's why you want cold, dense, and if possible compressed slightly air.
Another thing is the VCT is hydralic. Hydralics are not the fastest moving thing ford could have used. Pneumatic VCT would move the cams quicker but would be much more expensive. Since on demand torque while cruising is important in making a car feel "peppy" you cant just rely on the cams to move when you need the power they would be to slow. You would feel a slight lag between pedal and acceleration. A flap in the intake though could be a very quick way to increase the effective compression ratio giving that on demand torque people want. The other thing you could do to see this is look at the open / close tables in a GT tune and see how in fuel economy mode they are open more and drivability they are closed a bit more. Both modes open them after a quick change in load and only close them at very brief small load spikes.
Last edited by murfie; 02-04-2016 at 03:23 AM.
It doesn't have to do with injector atomisation, that's actually a separate issue. It has to do with cylinder filling evenly with an even AFR throughout. You'll see them in lots of places. IMRC, TGV, Swirl Valve, Swirl Flap, etc. Basically, without one, you get insufficient fuel mixing and you get spots that are rich, spots that are lean, etc and you don't have a consistent AFR throughout the cylinder which means combustion changes throughout the cylinder as the flame wave travels.
And you're right, this turbulence is only used to give this kind of benefit to swirl and tumble at low airflow velocities. At higher velocities, the airflow naturally swirls and tumbles off the valves themselves and fills the cylinder itself. Its part of most good head designs. Problem is these valves get in the way under high flows, which is why people used to delete IMRCs, TGVs etc, and is why Fords latest IMRC on the 15+ folds flat.
Fuel atomization and even afr are the same thing. Atomization means better fuel distribution by separating the molecules as much as possible. I guess molecularization would be a more appropriate term. Good injectors spray in a very fine mist that is in a cone shape. Unless our injectors are just squirt gunning the fuel I don't see the air swirling giving much more benefit. Fractions of a second better mixing time? Does that really benefit you more than the amount of air you are restricting?
You can have carbonated water or co2 diffused in water. You cant have waterated carbon dioxide. You can have humid CO2. humidity is just water vapor. fuel injectors are designed to atomize or get as close to vaporizing with out adding heat so that the fuel distributes through out the air charge with out needing the air charge to have a lot of turbulence.
Last edited by murfie; 02-04-2016 at 03:18 AM.
No it doesn't. Atomization is about how fine the particles of fuel are in the air, not about how evenly spread those particles are. For example, if I take a really good atomizing injector and spray it into the room I'm sitting in, does that guarantee the AFR is the same throughout the room? No, it doesn't.
Same idea here. The purpose of the swirl and tumble is to cause the air fuel mixture to actually better mix together.
Man, Bugasu post sounds familiar.... ;-)
And yes, minor improvements are what carry us forward step by step from the loose control of the carburetor.
The air you are restricting still leaves you with the right amount of air to make the power needed for the current demand: idle, light cruise, etc.
They open when you punch it. The cams move when you punch it. Every cam event/movement and every IMRC position/movement is temporary based on demand and need. You seem to be looking at each position combination as static or permanent when it's all dynamic.
Ok if you want to think about it as a room. I would say the injector is more like a fire sprinkler. They shoot water out in a 360 cone to cover as much area of the room as possible. Fans are not required to spread the water more because the sprinkler does a good enough job.
A room has stagnant air and maybe 10 sprinklers, a cylinder has one injector and is designed to accommodate fast moving air but when the air is moving very slowly it doesn't behave the same way so it needs a GT350R spoiler in the intake runner.
^lol^
There is a difference between air tumbling and air swirling in the cylinder. There are studies done in both. Some say tumble is better others say swirl is better. Which do you think is better? I personally think if the injector is doing its job of atomization and distribution well enough you don't want the air doing either, but instead have the smoothest least restrictive path possible.
Looking at the imrc flap and the two intake valve positions I would say Ford was trying to swirl the air at low rpms. I would say tumble if the flap targeted both valves to one side, but that isn't the case.
swirl_and_tumble.jpg
Last edited by murfie; 02-03-2016 at 07:26 PM.
So I have some unfortunate news, I went through VCT with my long tubes now installed and the car doesn't like any different VCT, which I find VERY VERY odd. Something is really going on here. No way it's the stock manifold demanding these VCT settings on it's own...
Kris
Have you disabled your desired air mass logic? Also increase your cylair multipliers.
Last edited by murfie; 02-03-2016 at 10:51 PM.
I am thinking best OP cam events are going to be determined by the weakest link, not the strongest. Whatever flows the worst, intake manifold, heads, or exhaust....
What is the weak link if it wasn't the exhaust?
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