How Dynamic Skip Fire Works - Variable Displacement Engines
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- čas přidán 27. 02. 2018
- How Dynamic Skip Fire Works - The Ultimate Cylinder Deactivation
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Dynamic Skip Fire is a new Tula/Delphi technology that aims to be the ultimate form of cylinder deactivation. It allows for fully variable cylinder deactivation, meaning if you have a V8 engine, it can run on one cylinder, two cylinders, or any number of cylinders up to all eight cylinders.
This video will explain how the cylinder deactivation works, what the advantages are, pumping losses, and what real world efficiency benefits can be expected. The majority of the benefit of this system comes from reducing pumping losses. That is to say, it's more efficient to run one cylinder at high load for a certain amount of power, versus running four cylinders at low load for that same amount of power.
Dynamic Skip Fire technology will make it's debut in the 2019 Chevrolet Silverado with 5.3L and 6.2L V8 engines, called "Dynamic Fuel Management."
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Hello everyone! Lots of questions in the comments about what's going on with the deactivated cylinders, since they're compressing air or pulling a vacuum. Regardless of the quantity of air that's in the cylinder, it acts like an air spring (stores energy, doesn't lose much). So if there's a bunch of air in there, it compresses the air, then the air pushes the piston back down - not much energy lost. If there's not much air inside, then it pulls a vacuum on the way down, but is pulled upward on the way back up. Ideal would likely be to have not much air in the cylinders that are deactivated, so there is not additional energy lost from the pressure on the piston rings against the cylinder bore. Hope everyone's having a great day!
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Engineering Explained if the valve is closed using this switch it may lead to breaking of switch. Why not use a cut off for fuel injection because if the valve don't open it create vaccumn n pressure inside the chamber lead to engine stopping. As per my opinion fuel injection should be cut off of smooth operation. correct me if I m wrong. Thanks for knowledge
And keep making videos
So does this technology require a throttle that is electronically controlled? Or can it be configured with a cable somehow? I know Tesla is not ICE but their models have a capability to remotely control the throttle, brakes, among other things. I hope this is unhackable, if it is electronically controlled
It is more efficient to keep the valves closed while cutting fuel injection since that turns the deactivated cylinder into an air spring with very little loses. That is the whole reason for this switch mechanism and it is also done in current cylinder deactivation methods. Just cutting fuel ignition while keeping normal valve operation will lead to pumping loses (both on intake and exhaust cycles) negating much of the gain.
Fuel injection will ALSO be cut. As it indeed is under some circumstances in any EFI system. Such as when decelerating or being pulled down a steep hill by gravity. If the engine speed is above a certain threshold point, just above idle, say around 1300 1400 rpm and the ECU receives a throttle position sensor signal indicating it is at idle or no throttle. There will be no fuel delivery. The injection duration will in effect be zero seconds. This stops wasted fue and unburned hydrocarbons being spewed from the exhaust.
But this does not help with the other aspects that were well covered in the video such as efficiency and pumping losses.
Very interesting. For the sake of running culture you can only shut of an even number of cylinders and you can only do it on engines with an even number of cylinders, because else you couldn't realize second engine balance.
My 87 civic been doing this all week!
Hahahaaaa
so has my lawnmower.
You have a multicylinder lawn mower? 😁
no.. i have four lawnmowers, only one works. ha ha.
nice
You do a better job of explaining this stuff than most of professors in college did.
Happy to hear it, thanks for watching! :)
Setting the car a little low aren't you? My experience with college says this isn't much of a compliment. Lol
Which would be unfortunate.
The labels over the whiteboard added in post were a great call. Awesome video as usual.
I had lots of questions on this subject. I read the comments and answers and got them all answered! Thanks for making such great videos and explaining things in detail. Keep up the good work. :)
I never even knew this was a thing!! EE teaching me things every weekish.
I always wondered how those old fully mechanical autotrans work. I have a vague memory of a maze of passages that I think act like a bunch of hydraulic valves turning thingsvon and off.
Hey Jason! Thanks for your comment about the air spring thing, that was my first question but you answered it before I could even ask the question!
My other question is this: how does the balancing of the engine work in this situation? How can a 4-6-8 cyl engine be balanced with only one cylinder firing?
Another great video! You do such a good job explaining things. You're not too technical, not too simple. You really get the point across! I'll agree, cylinder deactivation somewhat complicated, more parts. I think reliability will be very good. It's not totally new technology. Probably one of the best ways to improve fuel efficiency, while having plenty of power available. Again, great job, please continue making videos, they're all great!
Jason, I love your videos man. I'm an electrical engineer myself and always like to learn the mechanical sides of things. These types of videos are my favorite, I am really happy to see your channel continuing to grow. Been with you since the beginning back when you where in college. Keep up the hard work! P.S. It would be sweet if you could do a video about the Lexus 2UR-GSE with the 16 injectors. Im curious to know how those work. 8 intake injectors and 8 port injectors seems interesting.
Excellent video and I agree with everything you said. I'd like to mention a little more about effficiency. The most efficient internal combustion engines made are the huge diesel engines used in powering ships across the oceans. Some of these engines have cylinder bores on the order 10 to 15 feet. This results in a drastic increase of cylinder volume to cylinder wall area ratio, which also results in far less heat being conducted out of the gasses through the cylinder walls. By cylinder walls I mean the total area exposed to the gasses with consists of the piston crown, cylinder head and valve head areas plus the actual cylinder walls. Cylinder deactivation in these engines is typically not used because these ships' engines are typically designed to operate over relatively narrow power requirements, which is typical for ships.
Yet another amazing explanation of new technology! Thank you Jason!
Not sure if it's a great idea but you did a great job illustrating it.
Thank you!
Great explanation on a subject I have wanted to understand better but no one seems to want to attempt to explain and thanks for adding the info in comments about the push pull action of air on the dead cylinders answering that question.
But PLEASE add more info about the main reason the fuel economy is increased when you talk about the engine pumping being more efficient with less cylinders when vehicle is under a light load. I mean it seems this part is not explained enough to comprehend as vehicle's are fuel injected and more exhaust would seem better not worse. I do understand the hotter cylinder when turning off others.
Also I'm a bit surprised that the friction of the dead cylinders still spinning isn't a concern on economy, that we didn't find a way to disconnect the piston movement altogether.
Also a discussion of the old method of turning off cylinders history would be a great discussion. I had a friend with a Cadillac from I think the 1980's that had the 4-6-8 engine and he I believe had to have major work done on it because of failure and he lived in an apartment, seems that engine emptied his wallet and was one of the reasons he never could get out of monthly rent and buy a house poor guy.
Thanks
hey man can you please do a video on why inline 4 cylinder engines in cars are different to moterbikes? things like the different rev limits possible, compression ratio, bore to stroke ratios all that jazz. love your vids hope you keep up the good work.
I know for a fact that my 200cc motorcycle already does that by igniting a single cylinder hehehe. Keep up the good content (Mechanical engineering student from Brazil here)
Hey good video. Just wanted to note that the intake valve can in fact act like the trottle plate. In fact gas motors can due away with the throttle plate. You just have change the cam for timeing duration.
Hi! My name is Michael and I am a huge fan of your videos. I've been watching these videos for fun in highschool, and then more seriously in college as I pursue my ME degree. I am part of an FSAE club in school, and we might make an air intake manifold for our senior design project. I was wondering if you have any videos about ram intake videos, I cannot seem to find any, I may just be really bad at searching things up haha. Anyways, thanks!
Very cool. I like when you do videos on new emissions and fuel economy technology. It really helps show where the industry is going. With fast acting modern engine controls this kind of tech is becoming reality.
If something as complex as vtec worked in the 90s. I imagine this could work perfectly its a similar mechanism.
Great video as always!
Hey Mr. Engineering Explained, you're doing very interesting videos! Keep that way! And now the question: could you recommend me a book to learn a bit more about exhaust gases? Thanks!
Got my mind blown again after a whole damn day of work. Thx dude!
Thanks Jason, I really wanted to know more about this!
Hey Jason, great video as always. Can you do a video on how muffler lengths affect performance? The word going around is that longer and smaller diameter mufflers produce more low RPM torque, while shorter, larger diameter ones produce more top end.
There are others who say it's exactly the other way around.
I saw your video about how header lengths affect performance, now we'd love to see you debunk the muffler issue once and for all :)
Cheers.
I've a Dodge V8 (Hemi 5.7), Chevy V8 (LS4 5.3) and a Chevy V6 (3.9) that all had cylinder deactivation - and those are all at least 10+ year old engines at this point. Worked very seamlessly in each one of those. This is not a new technology at all, but the concept of varying the deactivate-able cylinders is. Will be interesting to see how this is implemented.
I absolutely LOVE LOVE LOVE all the new valve and ignition tech coming out lately, like Freevalve, Sky-Activ X and this Skip Fire. It's so god damn cool seeing people finally doing really clever new things with the ICE to breathe new life into it before we lose it to electric and hybrid vehicles.
Surprised the locking pin is oil pressure operated, not an electromagnet.
Well explained. It’s a brilliant idea whichever method is used. Not much use for me however, my car uses a relatively small diesel engine. Regards
Hi Jason, amazing video (like always)! This technology is so great for performance cars in the daily driving.
If you can, try the Giulia Quadrifoglio which has cylinder desactivation - test it and tell us what you see, fell and how the fuel economy changes! :)
Thanks Jason
Cheers
I liked what you did there with the text magically appearing/disappearing on the whiteboard.
Would u please talk about 1NZ-FE,2AZ-FE, and 2AR-FE? And I love to hear from ur best explanation skills. And can u talk about why Toyota stop producing factory turbocharger on Supra,Celica,and other Toyota models and japans favorite TRD turbocharger as well?
Thanks a lot for what u do.👊🏼 keep making more awesome car parts vids.
Finally back to hit n' miss style of combustion on all cylinders.
I like it.
Not that the way to get there is the same as on a hit n miss system, but it delivers the same style of fuel economy, in the same way. Keep tabs on engine RPM, and only fire a cylinder when needed.
Neat.
Hi EE, i like your videos a lot, especially the white board part, it would be much more usefull for a lot of ppl if you can branch out of automobiles. Some interesting topics are gas turbine engines, power plants, mri machines, boilers, quantum computing etc etc. Big fan of your presentation would love to see you explore beyond automobiles.
Looks interesting. I wonder how it compares to solenoid actuated valvetrain?
I'm interested in the relationship between this and engine balance. Does engine balance play a noticeable part in determining which cylinders (and how many) fire? Is engine load also a factor? Does the 'air spring' of the deactivated cylinder's mitigate this issue somewhat?
Ooh! A great idea. Also, we can build in a special "straight line" mode. Here's my idea. We monitor the steering input of the car in the ecu. If there isn't any, we detune the engine. You know. Because you don't need as much power if your not in twisty roads. Has this been done yet!
My car (2017 Accord Coupe V6) has VCM, and idk if I wanna turn it off once I get my Ktuner. Concerned about oil consumption and other issues later in the engine's life. But that 33mpg on the highway is nice...
I am a class 8 truck owner operator and a 31 year veteran commercial truck driver and we desperately need this dynamic skip fire / dynamic fuel management technology in the commercial truck industry along with a lightweight electric engine somewhere in the drive line that exists solely to allow us to creep along at low speed in traffic in purely electric mode during traffic jams.
Given that both corporations and individual business owners like myself have taken a severe financial beating to the tune of $25,000.00 to $30,000 per year in maintenance costs since about 2007 on new and especially on post warranty used commercial truck maintenance, such fuel efficiency technology would still be widely embraced after a few years given the financial disaster that Regen, DPF and DOC Filter and other emissions technologies mercilessly rained down on the trucking industry since 2005.
For those of you who do not know, I have learned through very costly personal experience that one practical way around about 15% of high tech engine maintenance costs is to have, for example, A Cummins Gold Store "Only" work on your high tech commercial diesel engine because I have found through $60,000.00 in cold hard cash experience on a 2013 Freightliner Cascadia with a 450 horse power Cummins ISX Engine with a straight 10 speed manual and 4.42 rears that modern commercial truck maintenance has become so highly complex that your truck dealership, not to mention a shade tree mechanic, cannot properly work on your engine and neither can an ordinary store of the engine manufacturer... Your engine has to go to a Gold Rated Store where the maintenance people actually know what they're doing... This will save you thousands in un-needed parts, downtime and anxiety.
This is very interesting, would be good to see the longevity of one of these systems before something breaks!
I have a 2012 chevy Tahoe with 130,000 miles on it, and it runs perfect 👌
Cool video!
Would another way to put it be that by shutting down individual cylinders when the power need decreases, the engine operates more like a smaller one designed for the lower load and performs better due to the lesser inefficiencies of a smaller engine?
Anyway, love your work.
Awesome video and awesome improvement! But ... I asume you explained it for the perspective of an NA motor, what about turbos etc? 🤔
Wow 1.6M subs! I have subs when u were 200k maybe? It's good to see that more people are valuing your work :)
I am not sure if it is because I'm tired or if it is because I fell asleep in most of my math classes, but I just fell asleep for 43 minutes while watching this video. Thank you
LOL.
That is cool tech. I'm wondering though, if the throttle body is open so much with just one cylinder firing, how does the ecu know to adjust when you want to accelerate. I'm guessing the throttle is flyby wire. So the ecu is probably controlling the throttle body independent from the pedal, based on engine loads. And so based on the pedal position the ecu knows when you want +/-acceleration. Is that a close approximation of how the system functions?
If I am understanding this correctly and the point of closing the valves is to create some sort of "vacuum spring", the moment your rings start to wear (which they will) where a normal engine would have started smoking slightly, (a normal N/A engine for example only has to suck in atmospheric pressure which will be positive and if the rings leak on the compression stroke it leaks into the crack case) where as this system will put unnecessary strain on the rings and essentially start sucking in crank case air through the rings bringing oil with it. Then when the cylinder comes back online there will be oil in the combustion chamber, thus creating a engine that will randomly puff out smoke or suddenly stop. Almost like smoke vtec.
A few weeks ago you explained the petrol (gasoline)engine using the Diesel high compression ignition system. would be interesting to see this "variable cylinder" system combined with the "compression firing system"
A very interesting concept and it certainly sounds convincing from the scientific point of view but if an engine of this type I think were to be actually put into production it would probably exceed the skill levels of most dealership mechanics who would have to work on them. Great presentation how ever! Keep 'em coming! I enjoy each one!
they've been in production for at least 17 years already.
I love this theory. And on paper it's a wonderful idea!. As a master Ase tech that's been at a chevy dealer since 07 I can tell you for a fact that I never put pistons in a ls style engine until the 07 active fuel management engine That deactivates cylinders 1,4,6,7 using a different lifter that collapses inside of itself when unlocked. (Valves stay closed) Same idea AIR SPRING concept will take care of engine as it's running. Real world situation.... the vacuum inside the cylinder that is created is so large it actually sucks oil past the piston rings eventually causing a build up of deposits on the rings expecially on the bottom (oil seal rings), thus turning the engine into a big money pit of warranty repairs for the company by 50,000 miles and customer satisfaction numbers to plummet because their " brand new truck" now needs and engine overhaul. (Piston and ring replacement) Let me say again this all started in 07 and still to this day in 2018 I myself ( 1 out of 14 techs) put at least one set of pistons in a week ! 11 years later UNDER WARRANTY! So if we're running with this. I sincerely think the "air spring" idea needs more evaluation. Would love this to come together and not cost my favorite brand millions in warranty dollars. Or to hear alot of very brand loyal customers say " this will be the last one I buy" ...
How does this compare to the efficiency savings you get with a system like BMW's valvetronic? Both cylinder deactivation and valvetronic reduce pumping losses at light engine loads.
Some guy in Ukraine made an experiment with deactivation of cylinders, and running 60kmph (~37mph) he had consumption 5.5 liters per 100km (68.8mpg on highway) with all cylinders and 7.7 liters per 100km (49.3mpg on highway) with 2 cylinders.
Also Fiat had made 2-cylinder version of 500 model, which had 2 liters more consumption per 100km, then basic 4-cylinder version.
Hey, could you do a video on how much (if any) MPG you gain when you switch to alloy wheels? I know alloy wheels are lighter but are they light enough to impact mileage?
Great video and thanks for posting.
This sounds awesome, Surly this is a huge thing.
I'm not sure that pumping losses are reduced as when the intake and exhaust valves are closed, as the piston moves down, it is effectively pulling a vacuum which is very hard to do, or the other way is it is compressing the air on the up stroke. Maybe they can time the closing of the valves somewhere in between. The main economy advantage is that fewer cylinders running the same power can get higher cylinder compressing pressures and there for a more efficient burn. Lower intake pressures results in a lower compression pressure and a less efficient burn. I own a Chev L77 6.0L V8 with Cylinder deactivation. It is done through special hydralic lifters that stop the pushrods.
I think it is a great concept to save on fuel and lower co2. Could this concept be add older vehicles as after market product ? Some comment talked about engine air breaking and if non fireing cylinders could help the vehicle braking system ?? Like adding air brakes to a passenger vehicle
Hello everyone!
Best opening line. I'm curious as to what gains in fuel economy Infiniti's VC tech will provide in conjunction with this.
I'm assuming the gain won't be as much when operating on one cylinder, but would allow a lot of flexibility to obtain optimal efficiency
I saw your explanation about what happens during the compression and exhaust cycle so that answers one of my questions but it still leaves another is the plan to rotate which are the firing cylinders, or will for any given number of functioning cylinders the pattern remain constant for example if when ever one cylinder is required we fire cylinder 1, will it always be 1 or will different combinations be used to insure even where on bearings, rings valves etc. If the pattern is fixed I can see an issue with the engine failing sooner than normal as some combinations will be used more than others and stick with cylinder 1 it may have functionally gone thousands of miles more in active service than others.
When the dynamic valve is in (example 3) and both valves are closed, isn't the cylinder going to create drag by the piston still in motion and creating compression and/or a vacuum?
Question-In a specific (1,2,...,x) cylinder configuration, do they always run the same cylinders deactivated for that configuration? I'm curious if this will lead to extra wear on cylinders that were deactivated less often. Maybe it's a moot point.
How would you handle the vibrations from the engine running at 1 (or any low value) cylinder?
This is a good idea for trucks with v8s - v12s. When towing they can use all cylinders but when not they can use only 1 or 2
On the topic of pumping losses, Honda tried something a little neat (IMO) with the first R18s. Recall they used VTAK!! to have the low RPM lobes barely open the valves so they could run the throttle body at much larger openings (DBW) at low engine speeds / low power. They abandoned it for the following generation. I don't recall it having made any significant impact on fuel economy. Having driven both, the later engine felt a lot more lively (for as little power as it made). It'd be fun to watch the throttle plate reactions to this skip fire in action. Also curious what it would be like in terms of drive-ability. I'd imagine it would have to constantly rotate cylinders to keep them up to temperature.
Greatly explained as usual, but,,, will it always use the same cylinder when it limits usage or choose them at random? I guess being oil pressure activated there's not too much to go wrong and diagnosis should be quite easy by measuring oil pressure to each of the valves. I guess this also can not operate quickly like in ms on and off, but the engine would have to prepare it's self for the change over, I guess it would feel like a automatic changing gear??
Very informative video. I like the idea of skip fire
I was watching this video and i wonder how effective it would be to put a fan downpipe from the exhaust manifold to help pull out exhaust backpressure. Could this help improve the pumping losses?
how do they get around with vacuum buildup inside the bore , if the intake and exhaust is blocked wouldn't it suck the oil from the pan below ? and burn oil
Thanks for the great consistent videos.
Too many interconnected moving parts still (friction).
Yes you will see an improvement in efficiency but not by half (for shutting down 2 cylinders in a 4 cylinder engine).
The thing is, usage of gas for propulsion is very inefficient.
Appreciate you spending the time to educate all of us on how engines function.
He said the bigger the engine the more of a gain it is, why did you act like you were informing him of this?
Aggressive Pizza
I credited him for educating us through his videos.
I literally learn from these videos.
I never criticized him or the info he is sharing with us.
SDD525
Yep, I am a Chevy volt owner.
Might get the i3rex or a bolt as my 3rd car next year.
Happy to hear you are getting the model 3.
Why is it so expensive in Canada though ?
I'm guessing you will get the highest configuration model 3 ?
The price of the well equipped model 3 here in the U.S. is expected to hover around $55k.
Which options are you going for with your order ?
I almost got a Volt, I was cheap in the end and got a Spark lol. Close enough right? (volt/spark)
Aggressive Pizza
Lol @ spark and volt. Good one.
Yeah good choice on the spark. It is a great compact car.
The spark ev is also a spectacular car.
Hope you enjoy it buddy.
But would this be most efficent on like a 6 cylinder with itb:s and a sohc or dohc head?
If you could cut the Power to 5 sparkplugs when you dont need all of the Power and you could also have a itb system that would close 5 throttlebodies when Power isn't needed or maybe a 2 piece camshaft that would hydraulically put them together when Power is needed
What about having 4 one-cyl engines with clutches inbetween them, do the engine(s) that aren't needed cause 0 loss?
Would the system require overhead camshafts? And would it work with dual overhead camshafts? Also, what would this mean for the valvetrain in high load, high RPM situations?
What about the turbo ? Will it spin faster on 4 throttled cylinders or on 1 full ?
Plus if the disabled pistons pull vacum could it force a valve to open ?
I have the AFM on my truck on the speedometer it lets me know if I'm running on a V8 or v4 does the DFM let you know on the thermometer if it's running on one cylinder v1or or v8anything in between
I have always wondered with my 2013 Dodge Challenger R/T if the 4 cylinders it deactivates very occasionally are the same 4 cylinders or if it varies to reduce wear history on all cylinders equally?
one question tho, the purple part, it gets pushed down by the cam right? So is it on a spring like the valve?
hey multi air has worked out pretty well for fiat, personally have about 130k miles on a jeep with a multi air with zero engine issues, considering the concept (hydraulic valve deactivation) is very similar I can't imagine this being too much more failure prone in the right hands.
I use my SRT 392 Charger as my daily driver. V8 6.4 liter. I drive it in Eco mode where it makes use of the 4 cyl mode while its coasting on the highway. I think your numbers are correct. I get 13 in town with it off and 26 on the highway with it on. It does have a bit more hum or exhaust note when it switches to 4 cyl mode. Would that be worse if it could go to 2 or even 1?
Great video!
Hi Jason, i dont know how elso to reach you so i m using your last video. Do you have a way of calculating the added power needed to accelerate the wheels of a car when then the tire/wheel package is is made bigger and /or heavier. Then this laking power can be translated to estimate the difference in trap speed in the 1/4mile. (My concerne is with the new 2018 subaru STI ''slower'' car with same or better power) thanks
can this work on F.I. engines and 2 unrelated questions: can a supercharged FRS take 300 WHP reliably on stock internals is the Fiesta ST done for after 2018?
Would this contribute to higher amounts of blowback in later life engines, when the piston rings and cylinders are worn?
I wonder if theres any significant losses due to the work needed to still move the pistons in the deactivated cylinders and if there can be a system that can totally shut down the cycle per cylinder.
Great video, but it is the cylinder efficiency that is responsible for most of the improvement. If cylinder efficiency is the same running 1 vs 4 (which it is not), then it takes the same amount of fuel and air to produce 25 HP and pumping losses are the same.
Since we are on the topic of engines, a while ago you did a video on supporting mods if you want to install a turbocharger, would you do the same for supercharging anytime soon? Also when you are going from NA to forced induction, your torque increases, doesn't that affect the reliability of engine internals, by putting more stress on them at high RPM, which brings me to a question which has been bothering me for a while. When you go forced induction on on stock internals should you re-tune the ECU for a lower RPM-limit/fuel cut-off to retain reliability? I'd be glad if you do videos on those topics.
It basically all depends on the exact engine - some can withstand much more, some are nearly on their limit straight from the factory.
would this cause piston to slow down ? if intakes valve remains closed when piston goes down it will crate a vacuum and cause piston to lose speed. This can lead to unstable engine speed. Please correct me if im wrong. thanks
I have been wanting this!!
I have a question I have wondered about for a long time.
When traveling up a long, steep hill is it more fuel efficient to be in a high gear with large throttle input or a low gear with lower throttle input?
I'm just curious how this affects cylinder glazing and other problems usually associated with extended idle. It's explained as a lack of pressure and heat that leads to the problems, so how would removing the pressure and heat from the cylinders over extended periods, like cruising on a highway or actual idling, be avoided using this system? Sounds like there's a few problems left to address.
Would switching or rotating out your cylinders like rotating your tires ever help relieve pressure in case one cylinder is under more pressure than others?
How about explaining the waste fire distributorless ignition system?( my experience is with the GM system)It is a bit older (from the early 90's). I still do not understand the "why" with waste fire systems even if I know the technical features.
Ironically I have a 2008 Silverado that I deactivated the cylinder deactivation and a 2012 Odyssey where I deactivated the cylinder deactivation. GM has had some oil consumption problems with there line for a couple. Of years and Honda similar problems. I hope GM fixes this cause I Like the idea.
how will the change the longivity of the engine? Is running cylinders at high RPM's with no combustion bad?
Koenigsegg’s free valve system could make these even better I think. Great explanation!
Will you cover anything about the Rimac's Conecept Two now that it's been revealed? I am quite interested to hear if you have something to say about it.
Jason, is there an upper limit to the fuel economy an internal combustion engine can achieve? Is there some sort of mathematical tail end to fuel economy or is it only limited by how good the technology gets?
@Engineering Explained With direct injection these days, isn't simply shutting off the injector for that cylinder good enough? What are the complications if we allow air to pass through cylinders un-combusted? By drawing more air with more cylinders pumping, the throttle will be opened wider too
Isn't there a loss associated with closing a cylinder(s) and compressing/decompressing the air inside? Is that less work than what is required to leave the valves open and push draw air into and push it out while keeping the injector and spark plug turned off?
Is the throttle valve computer controlled and does it have to change it's position every time a different number of cylinders are active? If so it will need to be able to react VERY fast.
So it works by opening and closing the intake valve right (putting it simply)?
I didn't get why the throttle opening was smaller when running on 4 cylinders? Wouldn't it need less or at least the same amount of air (ie. the same amount of air needed to create 25hp in one cylinder would be roughly equal to dividing that air four ways and sending into all 4 cylinders) and consequently have a similar throttle opening? That confused me a bit - seems counter intuitive.
MrSlash00r The problem is that four cylinders want to "pull" four times the amount of air at a constant throttle position (in comparison to just one active cylinder) So you have to limit those four cylinders with an even stricter throttle.
How can 4 cylinders pull 4 times more air? They don't pull air at the same time.
On average they do. At, let's say, 3000 rpm, one working cylinder would pull air in 25 times per second. With all 4 cylinders working they would also pull air 25 times per second... each. So there would be some cylinder pulling air 100 times in one second, and with the same amount per one pull per cylinder it means 4 times more air pulled in each second.
szafirowy01 Ok, I got it.
The airflow with DSF is slightly smaller, since it only goes down because the efficiency improves. The pressure differential between the intake manifold and the atmosphere also goes down. One requires a smaller throttle opening, while the other requires a larger opening. So the change(size and direction) in the throttle opening will depend on the operating condition.
I know little about this. If the engine tends to favor using certain cylinders, won't that wear them quicker than they otherwise would since they are under more load? This is cool as hell, but as someone that focuses on rebuild work, I'm interested to know how it effects the life of the engine
Would there be significant knocking (I mean forces that don't cancel out)? Could that reduce the lifespan of a straight 6?