gavriil

I am not sure if this has been discussed here but I found some cool pics of BMW's new Valevetronic. THe main thing here is that the system makes the engine more reposonsive because the engine needs no THROTTLE body any more. BMW states: "BMW developed this feature to replace the throttle plate: the engine can now breathe more freely thanks to fully variable control over the valves and valve lift. This reduces fuel consumption by ten per cent and more."

Here is a cool photo...look at the top of the head where the electric motor shows clearly. That motor moves accordingly to change the cotnrol of the valves (lift, duration).



Funny thing is that currently only the 3 Compact is getting this technology. There are 2 engines available, the 1,6 liter making 115hp and the 2,5 liter making 192hp. These engines are made in England only right now.

I wonder what this system could do to the M3's engine. Even more responsive would be fantastic :-)

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Gabriel
CL Type S

frederix

I thought BMW's steplessly variable VANOS system already contolled valve timing. That looks like a standard DOHC I4 with an extra camshaft like device in the middle that possibly just adjusts valve lift. Notice the devices on the end of the camshafts. Those are computer controlled adjustable cams gears. VANOS is far superior to VTEC as it can infinitely adjust valve timing on the fly.

EricL

Vanos does adjust the valve timing as you say.

This missing piece is the variable lift..

1. Just adjust the intake and exhaust with the equivalent of a "degree" wheel under computer control

2. Now make rocker arms with variable pivots (or whatever) and now the lift is controlled.

I am not sure what efficiency is gained vis-a-vis closing down the valves vs the throttle plate. There will still be pumping losses as the pistons pull against the partially closed valve, in lieu of the partially closed butterfly.

However, it does allow for a ton of power potential, since the complexity of the single throttle per cylinder goes away (like the new M3 engine).

This is great stuff -- I have a feeling that this is going to last a few years (like analog flight controls) and be replaced with a truly electronic/pneumatic/hydraulic digital controlled valve system.

Why -- less moving parts than regular POS vehicles (no rockers, no springs, no lash adjustments). Just some valve actuators and a few more connections to the ECU.

This would be a tuner's dream, super high RPMs, and tons of fuel economy. Finally, the user could have a "real" economy/auto/sport/race rocker/control on their console.



------------------
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DtEW

VANOS and VVT-i varies timing but does nothing for lift or duration. They act primarily to bolster torque throughout the midrange in conventional tunes.

VTEC varies all three, but are limited to two set configurations. It allows a high-specific-output tune to be streetable by eliminating the lumpy idle and bolster low and midrange torque, although somewhat less so than the continuously varible systems.

VVTL-i and iVTEC are the combination of the two-step VTEC and the variable timing of VANOS/VVT-i. Again, there are two configurations of timing, lift, and duration, but it also continuously varies timing, presumably giving the best benefits of both.

Valvetronic is basically VANOS with the addition of a system that continuously varies the leverage of the rocker arms, which allows it to continuously vary lift and duration, but not quite independently.

As you can see, the actuator motor turns a worm screw that turns a 3rd camshaft. The follower to this 3rd camshaft are those strange Y-arms, which at their base move the fulcrum of the rocker arms back and forth, varying its leverage.

I can't tell in this picture if the center camshaft is designed for high-speed operation, but if it is, it can conceivably follow the rpm of the main camshafts, but by varying its "clocking", can produce variable duration effects. If it's for slow speed, then it can only vary the leverage by rpm, and only control lift.

It's an interesting system, but I think it will soon be overshadowed by fruition of electromagnetic/pneumo-electromagnetic valve actuation technology.

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051/LP/SR/LD/HH

DtEW

LOL, I gotta work on writing faster.

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051/LP/SR/LD/HH

gavriil

This system in my opinion is quite a few years away still. F1 cars only have implemented this successfully for about 3-4 years now. Plus we need more ubiquity in the new 42 Volt standard cos pneumatic anything needs electric power which is not so apparent currently with the 12Volt systems.

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Gabriel
CL Type S

gavriil

Here is more photos of the system:



[img]


This is a good one. This is the main mechanism that makes the difference:

And a little more about how it works:

Its most important feature is that it is able to save at least 10 per cent fuel throughout the entire operating range relevant to the customer, with a corresponding reduction in exhaust emissions, regardless of fuel quality. And a further important point is that the efficient operation of VALVETRONIC does not require any unusual types and grades of oil possibly difficult to obtain.

As a result of these particular features the 85 kW/115bhp BMW 316ti compact with its top speed of 210 km/h or 125 mph consumes a mere 6.9 litres of premium fuel on 100 kilometres in the European test cycle, equivalent to 40.9 mpg Imp. This is a significant 0.7 litres less than the former 77 kW/105 bhp compact and well over a litre less than all competitors in this class.

The VALVETRONIC system is based consistently on BMW’s proven double-VANOS (VANOS = variable adjustment of the camshafts), with infinite camshaft adjustment to meet specific requirements. The additional, variable valve lift adjusts the effective cam action and, accordingly, the opening cross-section of the valves.

This is done by a lever positioned between the camshaft and the intake valves, its distance from the camshaft being adjusted infinitely by an additional eccentric shaft operated by an electric motor. Depending on the position of the VALVETRONIC control system, the lever converts the cam contour into a larger or smaller valve lift, whatever may be required.

Taking nature as the role model: human beings also apply the VALVETRONIC principle

A comparison with the human being clearly explains how VALVETRONIC works: Whenever we are required to make a great effort, we human beings breathe in a deep and long process of ventilation. Whenever we need less air, we do not throttle the supply of air by, say, closing our nose or our mouth, but simply breathe in a shorter, flatter process of ventilation. In a conventional combustion engine the throttle butterfly is basically comparable to a human being keeping his nose or mouth at least partially closed. With its large valve lift (= deep, long ventilation) and short valve lift (= flat, short process of ventilation), VALVETRONIC, on the other hand, is able to breathe in the same way as nature – always in line with current requirements, without any kind of throttling effect and therefore with maximum efficiency.

Fuel economy up by at least 10 per cent: as economical as only a diesel was in former times

VALVETRONIC offers the customer direct, immediate benefits, with fuel consumption and exhaust emissions decreasing, but dynamic performance and the spontaneous response of the engine improving accordingly. Added to this there is the even higher standard of running smoothness, since the valves move only slightly in a precisely controlled process.

The improvement in fuel economy ensured by this concept of throttle-free engine load management is approximately 10 per cent in the EU cycle and at least 10 per cent under the typical driving conditions encountered by a customer. The basic rule is that fuel economy versus other concepts increases with the driver running the vehicle at lower loads and engine speeds. The consumption figures the motorist is able to achieve in this way are comparable to the fuel economy only a diesel engine was able to offer just a few years ago.

At the same time the new four-cylinder is even more dynamic than its predecessor, the 316ti now accelerating well over a second faster to 100 km/h, achieving this important mark from a standstill in 10.9 seconds. The standing-start kilometre, in turn, comes after 31.6 seconds, 1.8 seconds faster than before, and the top speed of the 316ti is now 201 km/h or 125 mph, 11 km/h faster than the top speed of the former model.

Another advantage is the unusually spontaneous response of the 316ti to the gas pedal. This is attributable to the simple fact that load control, to use the technical term for "giving gas", now takes place "right there where the action is", that is directly in the combustion chamber. This eliminates the usual time lag between the process of "giving gas" and the actual acceleration of the car, which used to be inevitable due to the need to fill the intake manifold between the throttle butterfly and the combustion chamber. In this respect, VALVETRONIC even outperforms the most advanced concepts using individual throttle butterflies, thus offering an unprecedented combination of spontaneous engine response and ultra-fine dosage of power and performance under low loads.

Perfectly suited for all fuel grades, contrary to a direct-injection (DI) petrol engine

Another significant advantage of VALVETRONIC highly beneficial to the customer is that a VALVETRONIC engine offers at least the same fuel economy as the most advanced direct-injection petrol engines without the same compromises in terms of emissions. Accordingly, the 316ti is able to do without the elaborate and so far hardly reliable emission management technologies still required today on a direct-injection petrol engine. And it does not require sulphure-free fuel like a direct-injection petrol engine, achieving its superior fuel economy with proven l =1 technology, which allows the VALVETRONIC engine to run on all commercially available grades of regular petrol. In other words, the customer enjoys all the consumption-related advantages of VALVETRONIC also when driving in countries without a nationwide supply of sulphure-free fuel. The consumption figures for the 316ti nevertheless relate to the use of premium fuel with an octane rating of 95 RON. Together with its 63-litre (13.9 Imp gal) fuel tank, the 316ti offers a much longer range than its predecessor, with extra-urban fuel consumption in the European EU test cycle of just 5.3 litres for 100 kilometres (53.3 Imp gals). This means that the driver would only have to refuel after a very significant 1,188 kilometres or 737 miles.

Basic engine design completely revised

Not only the cylinder head with BMW’s new VALVETRONIC technology, but also the complete four-cylinder power unit featured in the BMW 316ti is an all-new development from the ground up. The new crossflow cooling concept with its open deck crankcase reduces coolant flow resistance and therefore allows use of a smaller water pump with just 60 per cent of the usual power uptake.

Made of aluminium, the engine block ends exactly on the centreline of the crankshaft bearings. A ladder frame between the crankcase and the oil sump connects the lower halves of the bearing bridges to form one complete unit also accommodating the balance shaft housing and the two-stage oil pump. This makes the entire drive unit very stiff and robust, minimising any vibration of other vehicle components the driver would otherwise feel on the steering wheel, gearshift lever and pedals, and also perceive as a kind of consistent humming noise.

All ancillaries are bolted directly to the crankcase without the rather elaborate supports and attachments otherwise required – again an important contribution to running smoothness with vibrations reduced to a minimum.

BMW’s new four-cylinder furthermore comes with all modern engine technologies such as:

Anti-knock control for running on all fuel grades between 87 and 99 octane.

Maintenance-free ignition system with individual coils.
Maintenance-free valve drive with hydraulic valve play compensation.
A Service Interval Indicator to keep the cost of service to a minimum
A two-mass flywheel for maximum running smoothness
Valve drive with roller bearings throughout in the interest of minimum friction and fuel consumption.
Advanced catalysts near the engine in special manifold design for minimum emissions.


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Gabriel
CL Type S

[This message has been edited by gavriil (edited 04-12-2001).]

DtEW

I just noticed that the worm-and-gear of the 3rd camshaft is not a whole gear cut-away to reveal the rear, but that it is indeed half-a-gear. This means that the 3rd camshaft can't complete an entire rotation, limiting this system to varying timing and lift. It can't vary the duration of the lift. The roller bearings should have clued me in to the fact the speed of the 3rd camshaft is too low to sustain an oil film.

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051/LP/SR/LD/HH

Buffalo

WTF? Is this automachanics 501?

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'01 Naples Gold CL-P

... Just don't be the slowest wildebeast when the cheetas are chasing you...

gavriil

Hey DTEW,

In the first photo I posted in the first message, what is that chain at the bottom? The one that LOOKS like it is connected to the crankshaft gear. Does it have anything have to do with the oil pump?

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Gabriel
CL Type S

EricL

You are correct to some degree about the switch to higher voltage systems. However, a small switching power supply could easily perform the required voltage boost, without going to a different battery.

Perhaps some people will even consider the use of multiple "busses". And use them to keep noisy power electronics off the quite busses. Also, the current set of semi switching devices are very cheap. A one dollar part (MOSFET or IGBT) will switch about 20-100 amps @ 70-100 volts.

So, if someone figures out how to build a linear stepper motor (linear actuated valve) or other device to fling the valve up and down, you know they are going to do it.

The latest gossip is about the F1 guys finally sorting out some electromagnetic valve stuff for upcoming cars. The F1 engine RPM will rise again.

I love the idea of ANY form of variable duration/variable lift valve operation, and appreciate this most informative information you have provided.

So, with all that aside. In lieu of a bunch of "rube goldberg" contraptions that is coming soon. Wouldn't it be nice to just have (as an imaginary example):

1. A intake/exhaust valve with a very small retainer spring (just in case).
2. A set of magnetized domains ala stepper motor.
3. A simple coil assembly that sits over the valve.
4. And a few wires going to this assembly.
5. Computer sends: move pulse + fwd or reverse signal.

Change all of my dreams above to your choice of futuristic actuator *and* you have no longer have the valves as the speed limiter in the engine. You could go to 30,000 rpm if the engine would hold together.

(-- ok, I like futuristic and simple solutions.)



------------------
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EricL

Yep -- every body hates tech stuff....



Sorry, I actualy like to read this stuff...



------------------
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gavriil

Looking at the first photo, no wonder why 4 cylinder engines vibrate a lot. Look where the pistons are. It is like 2 are either up or down. Of course it will virbate like crazy.

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Gabriel
CL Type S

gavriil

Currently F1 engines are rumored to go to 20,000 rpm and this year they make close to 900 HP. A lot more than 1 and a half years ago when it was close to 700HP. The main reason for this is of course the pneumatic head...or I like to say better...no spring POS limiter. It is really the valve springs being the problem, not the valves.

I was thinking the other day about these numbers and came to this series of assumptions:

If our engine makes 260HP at 6100 how much would it make if it continued at the same rate (or better, if it continued the flat torque curve) all the way to 20,000 RPM?

Well simple math:

260 times 20,000 divided by 6100 = 852.46 !!!

Wow, could it really make sense (the above)?

It does come very close to the rumors. Any super mechanic/engineer here commenting about this thought?


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Gabriel
CL Type S

Buffalo

Hey I'm learning stuff here... that's why its a 500 (graduate) level course.



------------------
'01 Naples Gold CL-P

... Just don't be the slowest wildebeast when the cheetas are chasing you...

EricL

OK, so excuse the worst designed page in all of web history -- here is a page with info on an:

"electromagnetic valve actuation(EVA)" by a company called Aura:

http://user.chollian.net/~vdocom/eva.htm

Here is Audi's page (about using Aura's system) with a picture of the engine (external view):

http://popularmechanics.com/popmech/...604TUMEPM.html

Finally, there are a number of electronic device makers with notes on how they need to get ready to supply the demand of these valves!

So, it is coming very soon...




------------------
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gavriil

Wow, I just realized that if F1 cars make about 900 HP at 20,000 then that means that their peak torque is about 235 lb-ft (close to what ours is). Provided of course that the peak HP and Torque appear at the same 20,000 rpm which is unlikely. If the torque peak appears in a more probable 18500 rpm then the max torque is 255 lb-ft which a little more than the M3's engine (252 lb-ft in the US)

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Gabriel
CL Type S

[This message has been edited by gavriil (edited 04-12-2001).]

frederix

The F1 engines may be able to rev that high with the new valves but they don't operate at those rpms now. Redline on those engines is under 15K rpm.

gavriil

Eric,

This might surprise you but I think that the following will come sooner than the EVA.



This is an electromagnetic system by Siemens (Siemens is Europe's GE to give you some reference). As you see the valve springs are still there only to do without the CAM here. So no cam with this system. Renault and DaimlerChry have already being buying this system for tests and soon will announce what they have found.

Siemens says that 42 Volts is imperative and actually recmmends a step further which is something called KSG which is an alternator that is part of the flywheel.

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Gabriel
CL Type S

gavriil

I do not know where you are getting this info but I am 99.9% sure that you are wrong. The only way for F1 engines to make more power is to raise the max rpm that engine operates since the discplecement is fixed at 3 liters.

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Gabriel
CL Type S

gavriil

Acutally F1 engines last year were operating at 18,000 rpm.

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Gabriel
CL Type S

EricL

Gavrill:

Here is a PDF file from Delphi automotive that spells out the need for a dual buss system 12v/42v.

www.delphiauto.com/pdf/DE99E100.pdf

I looked an there are a number of patents out there for various systems.

There is also a point where the differences between how you get the 42 Volts becomes somewhat academic... For example do you put in a dual wound alternator. Put in a 42 volt and down convert to 12 when needed. Or put in a 12 and up convert as needed.

Switching power supplies are very efficient and don't waste a lot of power (90-95% efficiencies are typical).

So, the race is on...


------------------
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EricL

Finally, speaking about voltage... That's why Edison lost out on wide spread power distribution. He wanted DC. Westinghouse/Tesla wanted AC -- it was easy to distribute high voltage with minimal current loss.

That is the point -- when you need to get a lot of electrical energy somewhere without using cables as thick as fingers, up the voltage some more (in whatever fashion is best).




------------------
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gto2050

Good stuff here but now I have a headache. I shoulda had another screwdriver before reading this tech stuff.

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01 CL-S NightHawk Black/Ebony Bowling Ball Interior

frederix

I agree with what you're saying but I don't think it's possible for those engines to rev that high yet. There is a point at which every engine will start to produce diminishing returns. I found this on a website about F1.

F1 engines are designed to rev much higher than road units. These extreme high revs make it impossible for this kind of engine to work as long as a normal car engine. An increase of 50% on revs does not necessarely mean an increase of power with 50%. From a certain point, e.g. 16500 revs/min, the internal friction is that high that engine power doesn't increase with a higher rev and even maybe decreases.

DtEW

No, that chain drives a counterrotating (relative to the crank) balance shaft, which in turn drives another balance shaft by gear.

Twin counterbalancers like this are fairly common in large-displacement I4's. Twin counterrotating to produce an up-and-down force and cancel out each others' moments. Usually they'd be turning about twice as fast as the crank to counter 2nd order forces, but this setup looks more like 4 times or so.

Look at the crankshaft at cyl #4 (the back one). Notice that on one side which you would expect to find a counterbalance, there is actually a large straight-cut sprocket in the midst of the crankshaft. Looks like a timing rotor, like the kind you see in ABS implementations. Any ideas?

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051/LP/SR/LD/HH

gavriil

THe one that looks like a smaller flywheel? I wonder what that is too. Anyone?

What could that be...hmmm...

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Gabriel
CL Type S

gavriil

I am bringing the photo in this second page so that it is easier to look at it and read the text and questions we state here...



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Gabriel
CL Type S

DtEW

Duh. I just re-read the company spiel. It's one of the two masses that make up the two-mass flywheel.

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051/LP/SR/LD/HH

[This message has been edited by DtEW (edited 04-14-2001).]

EricL

I think the one larger mass is for low speeds where a need for a larger mass is needed to dampen out the slower engine speed pulses.

I this the smaller one is for the higher speed, where the higher frequency would not require as big of a "mass" damper.

The gear teeth on the gears could be sensor pick-offs. As one stops or free-wheels, the other is connected, so if there is an engine managment pick-off, it would need to get a reading of cylinder postition from one or the other.

(my best guess)

But, it falls in with vibration and resonance:

Big flywheel for slow speeds (smooth)
Small flywheel for higher speeds (less-mass is needed, so why have high inertial mass to slow the accelerating engine.

Smooth at low speed, smooth at high speeds, with good pick up.

(guess, guess, ...)


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syncivic

You guys are missing one of the key limiting factors of RPM. The Shockwave produced by a piston in motion that reflects off the bottom of the sump can actually shatter a piston. This is called the limiting speed. I think that unless the stroke is reducted to just an inch or so, to get 20,000-30,000RPM is unlikely. If the stroke is that short, what is the driveability of such a powerplant in the absence of torque???

EricL

Good point, unless the transmission was a CVT designed for that power band, it would be a mess. If the car was really light, then perhaps it would be fine (as are the F1 cars, they are so light, that they get past the low HP/torque band so quick, that it doesn't matter. Our cars weigh about 3500lbs vs the 1400lb pound average of a F1 car. (The figures are approximations before anybody gets fussy -- ok.)

I don't know if Torque goes away -- your right the torque is generally higher with the long stroke. If your asking me do I want a street car that I have to run at 20,000 rpm with a Auto transmission:

NO

(but this is just my opinion)



------------------
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EricL

Part II:

Doug,

I'm more interested in the electromechanical valves from a plug-n-play perspective. By being able to program every parameter of a cam with a computer (as todays fuel-air and timing are) it would make mods, such as yours, a real treat to do.

Wouldn't it be nice, if you could just change some software and get the exact cam timing you wanted for your mods. And then add a really cool (Comfort/Auto/Sport/Race) rocker switch?

As I mentioned I don't want to have to get to 20,000 rpms to enjoy the car (similar to the high piston speed S2000). It is a nice car, but I'm passed my shift to 9000 rpm to get some real power days. I bet that thing would be a lousy car with a 4 or 5 speed conventional automatic (just my opinion).

BTW -- your right about the piston over-square ratios, but if they really think hard enough, I think it is like the sound speed barrier or other limits, people figure out ways to beat them (it is just my opinion).

(you can tell that I dislike limits...)


------------------
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[This message has been edited by EricL (edited 04-16-2001).]