"MasterMario - Keeper of the V8s" (mastermario)
02/04/2015 at 10:12 • Filed to: cafe, fuel economy, emissions | 0 | 32 |
I was reading an article about vehicle emissions and it made me think about all the manufacturers putting "Eco" modes into the engine software now. How do these different modes factor into emissions and fuel economy standards? As engines get more and more complex and variable what's to stop a manufacturer from having an eco mode that gets you 30mpg and 200hp available and then a "fuck it" mode that gets you 15mpg and 400hp (exaggerated and not based on science, but you get the idea)?
Have a picture of something that gets 10mpg on a good day for your time
Yossarian
> MasterMario - Keeper of the V8s
02/04/2015 at 10:19 | 0 |
That's sort of what turbo engines have already done. Usually they're tested with Eco mode on, and in simulated conditions get decent MPG.
But turn the Eco mode off and drive more spiritedly, and you're getting into more boost lowering your MPG.
Tinfoil Hat in a thunderstorm, now with added diecast
> MasterMario - Keeper of the V8s
02/04/2015 at 10:22 | 0 |
Will with a W8 races an E30
> MasterMario - Keeper of the V8s
02/04/2015 at 10:28 | 0 |
Vehicles are tested in their default mode. If eco is the default, then that is how it will be tested. Otherwise, the eco mode is purely for making up for the vehicle's inevitable inability to meet sticker fuel economy in the real world (only half joking).
With-a-G is back to not having anything written after his username
> MasterMario - Keeper of the V8s
02/04/2015 at 10:43 | 0 |
Manually changing modes would be vastly preferable to RPM-based VVT. I'd love to be able to switch cams with a dashboard button.
MasterMario - Keeper of the V8s
> Will with a W8 races an E30
02/04/2015 at 10:47 | 0 |
so as long as the eco mode meets fuel economy standards the manufacturers can go as crazy as they want with the HP figures, cool! but what about emissions...know if those are tested in the "default" mode as well?
MasterMario - Keeper of the V8s
> With-a-G is back to not having anything written after his username
02/04/2015 at 10:53 | 0 |
this is kind of what i was thinking about. with VVT, fuel injection, and electronically controlled ignition timing manufacturers can basically make one engine behave like 2 completely different ones. one that gets good MPG and on that doesn't...at all. Why don't they have it so you can really decide what you want to be driving like that day instead letting the computer guess when you want power and when you don't. i know that to some degree "sport" modes do this, but it seems it could be much more extreme than it is...or could be in the future. and then that got me thinking about the emissions and fuel economy stuff
Snuze: Needs another Swede
> MasterMario - Keeper of the V8s
02/04/2015 at 11:06 | 0 |
On a normally aspirated engine, this would be extremely difficult. An NA engine pumps a finite amount of air at any given condition based on factors such as displacement, RPM, volumetric efficiency, etc. You also have to consider that you need to keep your incoming air/fuel mixture in the stoichiometric range to prevent damage. There are some special cases, like Honda's stratified charge lean burn engines, which could safely cruise at 20:1 or higher ratios. But none of these techniques have never given drastic increases in fuel economy. Also, they are intended for small, efficient vehicles, so you're starting with a small, economical engine to begin with, like Honda's D15. So it's more like going from 150HP and 35MPG down to 75HP and 42MPG. Some NA engines do have Eco/Sport modes where in they change some factors like throttle response, variable cam timing, spark and fuel parameters, etc. But because of the above limitations your looking at relatively minor differences. Instead of 200/400HP and 30/15MPG, you're probably looking at more like a 10% gain/loss like 200/220HP and 30/27MPG.
A turbo car is a whole different animal. By controlling the airflow rate, you can control the volumetric efficiency of the engine, and the power production. So you can make a relatively small efficient engine that gets good MPG when it's out of the boost range. And then when you get on it, the turbos push way more air than the engine could ever pull under a natural vacuum and *VIOLA*, POWER! You also have a high degree of tunability, and if the turbo is sized correctly, a lot of flexibility.
Opposite Locksmith
> With-a-G is back to not having anything written after his username
02/04/2015 at 11:10 | 0 |
youuuuu don't understand vvvvvtttttt
MasterMario - Keeper of the V8s
> Snuze: Needs another Swede
02/04/2015 at 11:11 | 0 |
I thought one of the hug benefits of variable valve timing is that you can change the compression ratio
Will with a W8 races an E30
> MasterMario - Keeper of the V8s
02/04/2015 at 11:21 | 0 |
Yup. All EPA tests are done in normal driving mode.
MasterMario - Keeper of the V8s
> Opposite Locksmith
02/04/2015 at 11:28 | 0 |
enlighten me. My understanding of it is that you essentially change the compression ratio of an engine depending on when you open the valves. I know there are some limits to that, but those limits are always changing with new tech
MasterMario - Keeper of the V8s
> Snuze: Needs another Swede
02/04/2015 at 11:36 | 0 |
Kinja not working well for me...here's my full comment
I thought one of the big benefits of variable valve timing is that you can change the compression ratio. Also i know most (all?) vvt use separate cams so you have only have 2 settings to choose from but i was more thinking along the lines of future development where a cam may become non existent and valves are infinitely variable
Ferrero1911
> MasterMario - Keeper of the V8s
02/04/2015 at 11:38 | 0 |
This loophole is the reason why I have to push the "sport" button every time I start the car.
V8Demon - Prefers Autos for drag racing. Fite me!
> MasterMario - Keeper of the V8s
02/04/2015 at 11:54 | 0 |
Nope, it has NOTHING to do with engine compression ratio.
What VVT does is change your valve timing events and overlap.
What's that, you say? Look at the diagram below. It's basically the cyclic event for one intake and one exhaust lobe for a camshaft over the course of one full cylinder event (4 cycles) on an OHV engine. VVT can shift these valve events slightly to increase power/run more efficiently when needed.
And video with cheesy synthesized voice!!!!!
And another good link here: http://www.austincc.edu/wkibbe/vvt.htm
MasterMario - Keeper of the V8s
> V8Demon - Prefers Autos for drag racing. Fite me!
02/04/2015 at 12:11 | 0 |
yea, but doesn't that essentially change the compression. say you leave the intake valve open into the compression stroke...you aren't compressing as much air since your pushing some air back out the intake valve before closing it. then on your expansion stroke you can extract more energy because it is essentially longer than the compression stroke. by doing this aren't you basically changing the compression ratio?
V8Demon - Prefers Autos for drag racing. Fite me!
> MasterMario - Keeper of the V8s
02/04/2015 at 12:20 | 1 |
Now you're talking about volumetric efficiency. ;)
http://www.epi-eng.com/piston_engine_…
Snuze: Needs another Swede
> MasterMario - Keeper of the V8s
02/04/2015 at 12:28 | 2 |
VVT is pretty complicated and comes in a few forms. You have phasing systems and lift systems. Phasers are what GM uses in their pushrod V8s, it just adjusts the camshaft position relative to the crankshaft position. Some VVT systems on DOHC engines also only phase either the intake or exhaust cam(s), the other one is always fixed relative to crank position. Some of them phase both. But with all these systems you've always got fixed duration and lift, you're just adjust when the valve opening and closing events happen relative to crank position.
Fancier systems like Honda's VTEC can do both. The early VTEC has different lobes, a low end one and a high end one. At low rpms/part throttle the low lobes, which were designed for torque, operated the valves. At higher rpm/higher load the computer would lock slave the rockers to a free floating one that rode on the high performance lobe, it had more lift and duration to override the low end torque lobes. You could then add a VVT system to this so you can change both timing and lift, and you have a choice between two durations. Honda has some other clever forms of VTEC, and some subtle nuances in different versions, but they all work like this on the most basic level.
Ferrari had a very slick system (they may still use it, I'm not sure) where they ground multiple profiles across the cam, and the cam could slide back and forth to adjust lift and duration, and used phasers to adjust timing.
The problem with all these is they tie lift and duration together since all cams are cut in a lobe shape. The ideal profile would be more like a square wave - valve opens exactly when you want it, stays open at a specified height for as long as you want, and snaps shut exactly when you want it. Naturally this is impossible due to the inertia involved and infinite acceleration that's required, but with some of the solenoid systems, like Koenigsegg is working on, we may be able to get very close one day.
With a system like that, you wouldn't need Sport/Eco modes. The car would just always know; you'd have infinite cam timing, essentially, so a very well tuned ECU could always open the valves just enough and for just long enough to get in just enough air/fuel to make the minimum power required to maintain your speed if you're cruising. And as you open the throttle more, it constantly tweaks valve timing to deliver exactly the amount of performance your foot demands. You could also eliminate the throttle body completely, and eliminate a huge source of pumping loses (BMW fooled around with this with their VANOS system, it uses variable ratio lifters to control cam lift and duration, the car had a throttle body, but it was always 100% open, presenting almost no restriction, unless the VANOS system failed, then the engine was controlled by the throttle like a normal engine). And with that and direct injection, you can get very fancy, do things like open one valve more than the other or longer than the other, to vary the amount of swirl in the chamber, so you can have something like Honda's stratified charge lean burn system when you need it, to run very high stoichiometric ratios.
As to your comment about changing compression ratios, you can change the dynamic compression ratio of the engine with VVT, but not the static. Static is just the ratio of volumes of the cylinder with the piston all the way down and all the way up. Dynamic is much more complicated - static factors into it, but it's also based on the actual amount of air in the cylinder being compressed. Most modern cars have a static compression ratio of 9:1 or more, but dynamic compression ratios usually fall around 5:1 ~ 6:1. It varies with volumetric efficiency (which itself varies with RPM), cam timing (overlap and duration) and other factors. Overlap, though, has a large effect on this, and so with VVT is that you can adjust the amount of overlap (time the intake and exhaust valves are open simultaneously) to try and always maximize static compression. It helps, its one of the reasons why modern VVT engines are so much more efficient and have much broader usable power bands than older engines. But you are still limited by fixed duration and lift, the lobe shape of the cam profile, and mechanical issues like piston-to-valve interference.
MasterMario - Keeper of the V8s
> Snuze: Needs another Swede
02/04/2015 at 12:59 | 1 |
Do you do engine development or tuning? you seem very well versed in this sort of thing...or is it just a passion for you? i feel like I'm at that point in my knowledge of engines and cars where I know enough to do some damage, but not quite enough to completely know what i am doing...lol
Opposite Locksmith
> MasterMario - Keeper of the V8s
02/04/2015 at 13:22 | 0 |
Alot of times vvt like vtec have multiple camshaft profiles that are optimal for the rpm range youre coasting through. for example, at a designated high rpm, vtec switches camshaft to one with a profile optimized for high rpm breathing.
in order to have that power at the higher end of the range, you have to have vvt because otherwise running that high rpm cam profile at idling and low rpm nonsense would make for a terribly running engine until it got to its happy rpm
Snuze: Needs another Swede
> MasterMario - Keeper of the V8s
02/04/2015 at 14:19 | 0 |
I wish I did - I'm a marine engineer, but I do a little bit in marine propulsion, but its more integration, not really development. But engines in general are a huge passion for me, and when I was in college a couple years ago, I was on the school's Formula SAE team doing powertrain development, so I really learned a lot there.
It takes time, there's so much to know about the car world, you'll never know it all. You'll probably also find something you really like and get versed in that, which is powertrain for me. The benefit of doing Formula SAE is I have a bunch of friends now who are very well versed in chassis and suspension, so I'd never really learned that much about it.
Snuze: Needs another Swede
> V8Demon - Prefers Autos for drag racing. Fite me!
02/04/2015 at 14:20 | 0 |
Changes dynamic compression, which is a function of static compression and volumetric efficiency.
MasterMario - Keeper of the V8s
> Snuze: Needs another Swede
02/04/2015 at 14:52 | 0 |
Fellow engineer here too...I was on the Formula team at my school as well, but I never got to really dive into it so I didn't get to learn as much as I know I could have. I didn't join until my junior year (not sure why I never did before that) and then my senior year I was going crazy with 18 credit semesters and a part time job and did really have time to devote to it.
V8Demon - Prefers Autos for drag racing. Fite me!
> Snuze: Needs another Swede
02/04/2015 at 14:53 | 1 |
I was fixated on the static. It's not too often dynamic is spoken of by the average person. Thank you for the informed post ;)
Snuze: Needs another Swede
> MasterMario - Keeper of the V8s
02/04/2015 at 15:05 | 0 |
Yeah, FSAE is a huge commitment, but it's a great program and you can learn a lot if you have the time to dedicate to it. I was fortunate, going to school on the GI Bill, I didn't have to worry about holding down a job so I was able to spend a lot of time in the shop. But there are also lots of other great avenues to read and learn about car stuff. There's a ton of smart people here on Jalopnik, as well.
What kind of engineering do you?
Snuze: Needs another Swede
> V8Demon - Prefers Autos for drag racing. Fite me!
02/04/2015 at 15:06 | 0 |
It happens. I didn't even know dynamic compression ratio was a thing until a couple years ago. And you're welcome. Thank you for the pictures and animations.
MasterMario - Keeper of the V8s
> Snuze: Needs another Swede
02/04/2015 at 15:12 | 0 |
Was a test engineer for Caterpillar's mining trucks for a couple years, now I'm a design engineer in Eaton's power systems division (electrical stuff, not the automotive stuff unfortunately)
Snuze: Needs another Swede
> MasterMario - Keeper of the V8s
02/04/2015 at 15:50 | 0 |
That's awesome. I almost got an internship at Eaton a few years ago.
I work for Gibbs & Cox, a naval architecture firm. I do a lot of marine HVAC, but I'm starting to get into powertrain integration.
MasterMario - Keeper of the V8s
> Snuze: Needs another Swede
02/04/2015 at 16:13 | 0 |
Nice, sounds pretty interesting. I was actually close to taking a job in the marine industry as well. But it would have been with a defense company so with all the budget cuts in the last few years I'm kind of glad i didn't.
Snuze: Needs another Swede
> MasterMario - Keeper of the V8s
02/04/2015 at 16:31 | 0 |
Yeah, as the new guy you might have been on the chopping block, but it's getting better. I can't seem to stay out of the industry - I was active duty Navy for 6 years, then I went back to school on the GI Bill and ended up interning at Naval Surface Warfare Center Dahlgren and then Naval Research Labs. I had a job offer at Naval Surface Warfare Center Carderock when the sequester and shutdown and all that stuff happened. I spent a year working in construction before I got my current job.
The Navy has had some big misses in the last decade, so things are picking up as the industry tries to pick up the pieces. The DDG1000 program went nowhere, so they are ramping back up with DDG Flight III (one of my company's designs). Then there is the whole LCS debacle. We designed one of the variants - I think it's a cool ship but I think the pentagon was way out to lunch when they dreamed up the requirements for it. So we do life cycle support but we're also currently looking at SSC, which will be the successor to the LCS. Bulk of my work right now though is for the Coast Guard, we are bidding a new medium endurance cutter for them.
MasterMario - Keeper of the V8s
> Snuze: Needs another Swede
02/04/2015 at 19:00 | 0 |
that is quite the list of experience. I can't imagine ever being in any of the armed forces-thanks for your service. I bet those research jobs were really interesting though.
And LCS program is what i probably would have been working with that job I was close to getting. It would have been cool but i don't know that i would still have a job had i done that.
Snuze: Needs another Swede
> MasterMario - Keeper of the V8s
02/04/2015 at 21:56 | 0 |
Thank you, that means a lot. I'm happy I was able to serve. I got to do a lot of cool stuff while I was in the service - went in as a submarine reactor electrician, then worked as a small arms range safety officer, submarine ordnance inspector, and aircraft support logistician. All great experiences.
LCS is such a messed up program, it needs all the support it can get, so you may very well have kept the job. But given the way the economy has been, probably not worth chancing it if you got a sure thing going. I really hate working on it, all we do is study after study, trying to help the Pentagon make up their minds on what they want to do with the damn thing.
RamblinRover Luxury-Yacht
> MasterMario - Keeper of the V8s
02/20/2015 at 13:56 | 0 |
I was reading this post and replies, and saw this - what a small world! A brother of mine interned with Eaton power systems here in WNC last year and has kept in contact/working on some project stuff, and a guy in our church is at Eaton in power systems as well. I can't recall which voltage division, I think my brother's been mostly in low-voltage (yeah, "low"). I think he's trying to stay posted with what jobs may come up when he graduates this spring, though the hiring freeze they had here at the end of last year and some layoffs were a bit of a chill.