Amazing, Chevy builds a 330 HP engine with 28mpg Options

[jniemeier]

First, Eric- I agree completely. We could cut the oil consumption of cars and light trucks in half with today's technology. i.e. Double fuel economy. No sweat. But we can't do it while driving Tahoe's, Durango, Expeditions, and Land Bruisers... For me, step one is diesel. Instant 30% improvement with no sacrifice or downside for Joe American. Europe is now 50%+, US is <1%. I can tell you diesels are finally coming to the States. The fuel will be 30ppm sulfer I think in '06 or was it '07. That allows the diesel catalysts to live. Get ready for a gradual 20 year roll-in to reach 40 or 50% penetration. I don't know anything special about fuel cells, but I'm optimistic they will eventually make them economical. They've only scratched the surface compared to the millions and millions of man-hours invested in getting IC engines to work well.

Andrew- good guestion. You're making think, which has it's pro's and con's most days. Wish I could draw you a P-V Diagram. (Pressure vs Volume as a four stroke completes one cycle) Pulling the connectors on four injectors would certainly make things worse. The throttle blade would be open a bit more, as on a deac engine, but the non-firing cylinders would be wasting more energy pulling air in against the manifold vacuum and then pushing it out against the exhaust back pressure. It's a loser in both directions. These losses would be worse than the slight gain in the firing cylinders.

If you've heard it said that an engine is just a big air pump- well, that may be true but it's sure an inefficient one cuz the first thing you come to is a nearly closed off throttle valve. At highway cruise it's only open 10%. 90% blocked off, which is proven by the huge vacuum in the manifold. My 914 pulled 14.5psi vacuum at idle when I tested it this fall. That's a measure of how inefficient a motor is, not the opposite. One of the reasons diesels are more efficient is because they don't need a throttle valve, so there's no vacuum in the manifold. i.e., it's very easy for the pistions to suck in the next gulp of air. So, controlling a gas engine by throttling the air (both at the throttle valve and at the intake valves- don't forget) is inherently worse than controlling a diesel by the amount of fuel injected.

Charge density helps but it's not more efficient, it just has more air and fuel cuz it's denser. That's why intercoolers help. Cool air is denser (more) air, to which it's easy to add a smidge of extra fuel, and so get more power. Remember, you need to stay very close to the optimal 14.7:1 ratio. Burn rate and burn completion is mostly due to fuel atomization (droplet size), and local air/fuel ratio (how homogenious is it in there really?) and the degree of turbulence created by the intake velocity and direction and the shape of the upwardly rushing piston against the chamber shape.

Time to put the cookie-munchers to bed.
(IMG:http://www.914world.com/bbs2/html/emoticons/driving.gif) Jim N.
'73 2.0

[phantom914]

Jim,

Makes sense. If an engine had individual drive-by-wire throttles, would it be simpler to switch those out (closed) rather than the valves? And what if there were similar butterfly or other type of valves on the exhaust side. Wouldn't it be less complex than deactivating the valvetrain? Or if not less complex, would it work? I think it wouldn't work as well since the butterfly valves woudn't seal as well as a closed cylinder-head valve. I am just curious whether you think it would work at all since that would seem to address the pumping loss issues you mention. Don't think that I was thinking of trying it.....(IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif) .....this year... (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif) ... (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

I do still think (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif) that (maybe?) a fuller cylinder will burn more efficiently. It is harder to ignite and sustain ignition in a partially filled cylinder compared to a more fully filled one. I don't know the exact mechanism(s), but the pressure developed before and after ignition, heat generated by combustion and heat rate lost to cylinder walls etc affect ease of starting/sustaining combustion and also energy output/efficiency. (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif) Some of these factors would be affected by the amount of cylinder filling, wouldn't they?

Also, a car will get better mileage with higher gearing. Which of these factors are significant: 1) less frictional loss due to engine turning fewer revs over a given distance2) less pumping loss due to higher throttle opening 3) increased efficiency due to greater cylinder filling 4) any thing I didn't mention.

Is that too many questions? (oops, that was another one)


(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

Andrew

[jniemeier]

We call them ETC's: Electronic Throttle Control, and no, that won't work. For one, you can't put an ETC into a 500deg C exhaust stream. Well, you could, but it wouldn't live long. Why do you think this would work better? Doing it in the valvetrain is the closest to the combustion chamber we're trying to control and by far the most mechanically simple (engineers would say, "elegant") solution. There's no need to think up anything else.
Individual throttles implies you're using individual intake runners. Very expensive and won't fit for a V type engine. V engines like plenum's and a single throttle cuz it helps even out the flow balance to the cylinders, fits better, and of course is lots cheaper. Racing engines may have seperate runners, but keep in mind they are optimized around a very narrow rpm band.

Cylinder filling: I don't think you caught what I wrote before. You need to seperate the idea of quality of combustion from the amount of mixture in there. To have acceptable emissions, you need to keep the mixture at 14.7 to 1 air/fuel ratio. Period. After that, the AMOUNT of 14.7:1 mixture we get in there is the thing that directly controls the torque that cylinder makes. At Wide Open Throttle (WOT), less restriction to air flowing in, more mixture in the cylinder, max torque. At idle, tons of restriction past the throttle, little mixture inside, low torque. In both cases, the mixture is always 14.7 to 1. It takes a while to digest that fact. So, things like the ease of initiating the burn, and the combustion 'efficiency' are the same in both cases. The power generated is drastically different of course, so the heat loss to the wall is different, sure, but the efficiency is the same. Engines are most efficient at WOT not because they burn better, but because they don't waste work pulling air past the nearly closed throttle at low loads.
Answer to paragraph #3: Number 1 and 2 are both good, although I think number 1 is the easiest and likely the larger improvement, at least for big V8's. With a 914 engine pushing the car at 70 mph, you can't be lowering the revs too much can you? But, when Chevy was trying to avoid the gas guzzler tax on the Vette inspite of increasing hp to 400 (and now 500!), they went to gearing that left it turning what, 1600 at 70? Something like that. IF you have the torque, that's the easiest way to go. By now, I hope you agree that Number 3, increased filling, is simply a method to increase torque, not improve efficiency, BUT, you can use your increased torque to drive taller gearing, and THAT is option Number 1, the best option. So, 3 is just an enabler for 1. Got it?

Now, since you're such an inquisitive guy, here's my advice I hope you take on board: Go to a used book store (or probably Amazon) and buy a copy of "Internal Combustion Engines and Air Pollution" by Obert. That's the one used in most engineering schools and is the all time classic. Every engine designer in the country has a copy in his office. Read the whole thing. It's actually not that hard to read. I'm sure you will get a ton out of it.
(IMG:http://www.914world.com/bbs2/html/emoticons/driving.gif) Jim N.

[stock93]

Jim N,
Check out BMW's N73 6.0L V 12. They are the only gas engine I have seen that has direct injection in the actual cylinder like a diesel. This engine also has Valvetronic which is something else to check out.

John

[jniemeier]

Yes, it's an amazing engine. Not the first though.
DIG was intro'd by Mitsubishi about 10 years ago, although it wasn't new then. The '55 Mercedes SLR had mechanical DIG.
The Valvetronic system came out on BMW's European 318 in about '99. They have been gradually increased the volume of manufacture.

Jim N.

[snflupigus]

Thinking of the whole torque = good for economy with the right gearing.

so why did my near 4k lb 92 camaro camaro rev at only something like 14-1500 at 60mph and idled at 5-600rpm. with 170hp and 255lb/ft, an auto and 2.73 rear end it got fairly! good gas mileage even with a terribly slow ecm and not so accurate throttle body injection system.... I also am told it has the lowest lift cam ever put into a gm engine. wouldnt that cause more restriction and worse economy that a larger cam tuned betted at the ecm..

ahhhh. the LO3 never ceased to confuse me.. LOL

then thinking of an ex's neon idling at what 2k rpm and cruising the 60mph at 3500rpm! i hated that car but it did get better mileage than my camaro. lighter and smaller engine is the answer there i guess. I need to start reading up on all of this.

Jim, you've obviously studdied and worked in the field for years and years - what schools etc would you recomend to pursue your career? I hear Colorado has an advanced engine theory program...

[Carl]

Very interesting information, Jim.

For a long time I've wondered when we'll have the technology to build an electronically controlled valve train so that cams would be eliminated. To do this would require a strong, lightweight, temperature resistant gating device that would control cylinder intake and exhaust. The engine controller then could choose the most efficient timing for opening and duration for the engine loads. I imagine conventional solenoids are too slow to activate conventional valves this way but is there anything in the pipeline for this concept?

Thanks,
Carl

[snflupigus]

The selenoids would also have to operate at certain rates of opening and closing too.... can they do that? Arent most selenoids essentially on or off, open or closed. Wouldnt it be tough to have one selenoid open really fast and then really slow wouldnt it? Or would it be easy with varying electrical signal to them.

[J P Stein]

QUOTE (jniemeier @ Sep 24 2005, 07:03 AM)

The '55 Mercedes SLR had mechanical DIG.

As did the 1938 DB601 series engines. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) That Foker was in a Messerschmitt..

[Katmanken]

There has been a lot of work beign done on solenoid actuated valve trains and quite a few patents filed. Back when I did patent work, I would review the Official Gazette from the patent office and would take a side jaunt into the auto engine section (200-250?).

Having done work with solenoids, there are a lot of problems. One, the more you use one, the hotter it gets. The hotter it gets, the less efficient it becomes. You lose force big time when hot (80%?).

Next problem is the way they work. Solenoids create magnetism and magnetic strength depends on distance. If it is a linear solenoid, the force produced is weakest at the start and gets stronger and stronger as the armature approaches the end of the stroke. Not what you really need for overcoming a valve spring so you would tend to use a really big solenoid to get the force you need initially. Big solenoids need big power and produce big heat which reduces the force and then you need a bigger solenoid and.... round and round you go.


I was hoping that some of the room temperature superconductors could be made cost effective and they would possibly be the solution.

Ken

[snflupigus]

so how do fuel injectors continue working? The fuel cools them off right? I know with the large throttle body injection type injectors the throttle body itself would get cold to the touch on a hot motor sometimes so i guess the injectors themselves would have been cool from the whole fuel atomizing etc..

[jniemeier]

Someone asked about schools. I have no special advice about that. Find a school that has a solid Mechanical Engineering program. Most state universities do. Specialization comes in your masters program, should you go that route, and most people advise going to a different school for your masters anyway. Getting a degree is to teach you to think, and what get's you in a company's door. Actual useful knowledge starts when you get to work. That said, it's a good idea to pay attention when they teach IC Engines by Obert. (See above) I took it from a German, ex-VW engine guy whom we were legitimately afraid of.

Electric Valve Trains: Now there's a subject we could all debate for weeks. Basic benefit: Changing the duration of the lift event on the fly. Think of the motion of today's cam and spring driven valves. Cam design programs calculate four derivatives: (you paid attention in math class, right?) displacement, velocity, acceleration, and jerk. Even the jerk has to be smooth, if that makes sense. There's a whole lot more to it than lift and duration. Ok, fine. Chances of replicating this motion with an electrical solenoid? Zero. But do we need this gradual start - fast lift - gradual stop type motion? Well, if you want to keep from fracturing valve stems, you sure need to gradually close the valve. The solenoid guys call this "soft landing", and I understand there are patents for that via reversing the current at just the right moment. How do you know when the right moment is? You now need a valve position sensor. And it better be a darn fast one considering how fast the valve is moving much less the extremely nasty environment (see earlier posts). If you can do the soft landing, how much juice will it take to run the solenoids? Last I read, a couple research firms said they could do it with 1.5 kilowatts for a 16v four cylinder. Not terrible, but still too much, and I don't think it's been demonstrated either, although EMVT cars have certainly been driven around. (I'm sorry I don't know right off how much power it takes to drive a 4 cylinder's cam- but keep in mind that when the follower is on the back side of the profile, the spring is returning energy to the system not consuming it.) After we figure out lift profile, soft landing, position feedback, and power consumption, we still must face reliability of elec connections, packaging it to fit, noise (very important), lubrication, cost of the solenoids, cost of the control electronics, packaging of the control electronics, manufacturability and of course durability. It's a huge challenge, but what's new? There are a lot of bright guys in research companies who thought they could do it. Notice I've switched to past tense. I think full electric valve train is a pretty cold trail. One caveat though: HCCI combustion (Homogeneous Charge Compression Ignition) could be a huge efficiency improvement, but may require VT control like electric valves. If you want to know about HCCI, you'll have to look it up. I can't explain it very well. Think of controlling a gas engine like a diesel. Extremely tough, although I think this one will ultimately succede.

The fully variable valvetrain that's in production of course is BMW's Valvetronic. It changes lift and duration at the same time. We designed a system that did this also, but we could never get it cheap enough to sell it. I guess BMW has a different view of the value equation for new technologies. Interesting question: how much valve lift does it take to idle a 4 cyl engine? 0.3mm or even a bit less. That's amazing. And you can do it at 500 rpm or so, which saves a bunch of fuel. Turns out cars spend a lot of time idling.

There are a bunch of systems that change lift in two and even three steps. Most famous is Honda's VTEC. They have at least 6 variations of it in production, including on the new 3 liter V6 that does high and low lift and cylinder deac in the same engine. That is fantastic, and no doubt comes close to the benefit of Valvetronic for a lot less money. The Mitsubishi MIVEC system can do three steps and has been around for a while. Porsche have a two step system on the Turbo which is made by INA of Germany. Then of course there's cam phasing. That's old news, and on most cars these days.

The system that I've just read that IS going to enter production is Fiat's Electro Hydraulic VT. They sometimes call it UniAir. Electric solenoids open a high pressure oil circuit which has an actuator to open the valve. This sounds like a good idea, but the hydraulic fluid was always a challenge. The viscosity change due to temperature was a killer. Evidently FIAT have solved that problem. They will use it on a diesel (lower redline) starting next year or so. UniAir can do variable duration and lift by basically truncating the lift profile when it's had enough by dumping the oil through a relief valve. Should be great if it works. I actually met Dr Petronio, the father of UniAir once. (I was selling, but he wasn't buying!) He had been working on it for years at that time, and you could just tell that by-God he was not going to give up. Sometimes, even in a corporation the size of FIAT-GM Powertrain (they've since split up) it boils down to one very tenacious guy. In fact, I think it almost always does. That's interesting, eh?

Oh, and don't bother trying to dream up other "gates" or types of valves besides poppet valves, like the spherical rotating ones you read about. Talk about patents- in valve types, everything has been tried before. Nothing will seal combustion pressure like an inward opening poppet valve. No matter what system creates the opening and closing motion, today's poppet valves will always be used in piston engines. And don't even get me started on ported two strokes.

Pop quiz: How does a Ferrari valve get a larger lift profile than the what's ground into their cam?

Now, if I write any more you guys are going to have to start passing the hat. I'm going to bed.
(IMG:http://www.914world.com/bbs2/html/emoticons/driving.gif) Jim N.
'73 2.0 with a nicely lashed, single return spring, pushrod and rocker arm mechanical valve train that I can fix and adjust in my garage.

[Carl]

Jim,
Thanks for such a thorough response to my question. I appreciate your explanation of these systems and I guess we won't be seeing camless engines anytime soon.

Carl

[914GT]

QUOTE (snflupigus @ Sep 25 2005, 01:48 AM)

The selenoids would also have to operate at certain rates of opening and closing too.... can they do that? Arent most selenoids essentially on or off, open or closed. Wouldnt it be tough to have one selenoid open really fast and then really slow wouldnt it? Or would it be easy with varying electrical signal to them.

In our robotics storage systems at my work we pulse-width-modulate (PWM) the current to various solenoids in order to control their actuation speed, as well as significantly lower their holding current. Whether or not these same methods would work in automotive valve actuators I do not know.

[brp914]

ok, you headed me off at the pass with rotating valves - always wondered about that. How about on the fly oxygen enrichment. Combine that on a turbo direct inj. diesel. O2 is paramagnetic...higher molecular wt. than N2...different ionization energy...something. Well, if it's a stupid idea, so be it. If it makes money, I get 0.000001% of profit (or 1 beer, whichever is less). If you try it and it doesn't work, its all your fault.

btw, you're not qualified to adjust your valves.

[Dr. Roger]

Hi Jim,

Nice to read a chat from someone who's got some alternative engine know how.

I built a Grubb/Pogue prototype on a mini bike engine a couple of years ago and now that gas prices are skyrocketing my thoughts are going back to Pogue's fuel system.
I've always been facinated with Pogue and Otto engines. What are your thoughts on them?

As far as i'm concerned, there is no contest as to the efficency and cleanliness of a fuel vapor (warm or cold) as opposed to fual atomization system (injected or not). Oh yes, and cooler running. =-) Oh, and less fuel oil dilution. Oh, and zero carbon build up...

Roger

[jniemeier]

This is the first thing Google found about Pogue, and it seems about right.
http://www.mikebrownsolutions.com/fish3.htm

Jim N.

[MattR]

QUOTE (jniemeier @ Sep 26 2005, 05:19 PM)

Cam design programs calculate four derivatives: (you paid attention in math class, right?) displacement, velocity, acceleration, and jerk.

Jim,

Your posts are very interesting. Ive read them all once and Im going to read through them again. Having just taken a quarter of thermodynamics, all this stuff is freash on my mind. My impression on the Fish carburator; its not based on science, because it obviously fails, but its based on skepticism of science.

I do have a question about this statement though. You say 4 derivatives, now what are these derivatives? My math skills are sufficient (6 quarters of college calc.) but not necessarily proficient, but I obviously dont have much experience with this knowledge being a 3rd year mech e student. Displacement is dVolume/dt, velocity is dDisplacement/dt, acceleration is dVelocity/dt. Does this mean jerk is dAcceleration/dt? If so, wont having a cam profile of x^5 mean jerk is always smooth? And any exponential value of 4 or less will have 0 jerk? Im not sure how Im communicating my ideas, but I dont have a piece of paper in front of me.

[phantom914]

Jim,

Thanks for answering my questions (and for shooting down my hair-brained ideas (IMG:http://www.914world.com/bbs2/html/emoticons/ar15.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif) ).

I will shut up about cylinder filling promoting a more efficient burn. I thought something I read sometime ago implied this and I thought it was a great opportunity to ask the question since we have somebody (you) with first-hand knowledge. (IMG:http://www.914world.com/bbs2/html/emoticons/pray.gif)

And I didn't mean to imply that butterfly valves would be better in the sense that a manufacturer should do it that way, else it would have been done that way. As a mental exercise, I wondered if it would work at all and if a crazy person wanted to try it on his own, I thought that it was more feasible to implement homebrew cylinder deactivation with butterfly valves. No sophisticated throttle position control would be needed. Since this is a fully open/fully closed situation, I envisioned solenoids and butterfly valves and only on the intake runners and exhaust primary tubes of the cylinders that would be deactivated. The intake runners would still be connected to a plenum and there would be only one throttle body, with the extra butterly valves only being used to deactivate the cylinders, not throttle control. Would it work? Again, just for fun. (IMG:http://www.914world.com/bbs2/html/emoticons/blink.gif)

It's great to have genuine expertise (you again (IMG:http://www.914world.com/bbs2/html/emoticons/pray.gif) ) here rather than the all too common speculation presented as fact.

Thanks for the book recommendation. I'll look for it.

Andrew

[phantom914]

QUOTE (MattR @ Sep 26 2005, 06:16 PM)

QUOTE (jniemeier @ Sep 26 2005, 05:19 PM) Cam design programs calculate four derivatives: (you paid attention in math class, right?) displacement, velocity, acceleration, and jerk. Jim, Your posts are very interesting. Ive read them all once and Im going to read through them again. Having just taken a quarter of thermodynamics, all this stuff is freash on my mind. My impression on the Fish carburator; its not based on science, because it obviously fails, but its based on skepticism of science. I do have a question about this statement though. You say 4 derivatives, now what are these derivatives? My math skills are sufficient (6 quarters of college calc.) but not necessarily proficient, but I obviously dont have much experience with this knowledge being a 3rd year mech e student. Displacement is dVolume/dt, velocity is dDisplacement/dt, acceleration is dVelocity/dt. Does this mean jerk is dAcceleration/dt? If so, wont having a cam profile of x^5 mean jerk is always smooth? And any exponential value of 4 or less will have 0 jerk? Im not sure how Im communicating my ideas, but I dont have a piece of paper in front of me.

Matt,

On the derivatives, you are on the right track. First, I'm not sure, but I think Jim may have meant third derivative? I will explain a little based on that assumption, but if he meant fourth derivative, you can carry this example just one step further. The third derivative is also called jounce (at least when referring to a vehicle's wheel motion). I believe you want to have the third derivative be zero in the case of suspension movement to have a perceived good ride. In other words, acceleration should be constant. If the third derivative is not zero, that means acceleration is changing wrt time and that is what supposedly is the most objectionable sensation in a car's ride. I hope Jim can clarify his statements regarding the number of derivatives.

Oh, just noticed. There is a slight mistake in your statement. Regarding motion, displacement has nothing to do with volume, it relates to motion (distance travelled). So displacement is 'x'. Velocity is dx/dt. Acceleration is dv/dt and jounce is da/dt. And to go back to your statement, if the diplacement as a function of time is third order, the third derivative (jounce) is constant. If it is second order, jounce is zero. If it is fourth order or higher, jounce would vary over time.

My interpretation of what defines good or bad jounce and how it affects ride quality is only based on something I was told, so it may not be completely correct, but the rest of my explanation should be accurate. (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif)


But I'm just guessing. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)


Andrew

This post has been edited by phantom914: Sep 27 2005, 08:55 AM