Change your V-8 to a 4 banger

[johnmyster]

Originally Posted by Formula413

Great post.

That BMW concept of essentially letting the intake valve serve as the throttle plate is fascinating, I had never heard of that before. I've learned all kinds of neat stuff on here.

It's been a few years since I've been in touch with BMW's experimental works. Some of their stuff has made it into current vehicles, some hasn't. I know they sold a car that had constantly variable lift on the intake valves as well as timing, that could accomplish most of this. Timing is pretty common on cars, but they varied lift by mounting the rocker arms on an eccentric that varied the rocker arm ratio. This engine also used a throttle plate, but I think the throttle plate (throttle by wire) didn't do much - and was more of a backup in case the lift deal broke down. The end goal was fully electronic actuation of the valves (get rid of the camshaft) and do anything and everything with a computer.

The idea is that if you can hold the intake valve open during part of the compression stroke, you can spit out some air and operate at "part throttle" even without a throttle plate. Simply throttling at the valve through low lift or low duration doesn't rid you of pumping work losses since the piston (the pump) still sees vacuum during the intake stroke.

Thanks for the compliment. If you want to learn more, check my recent posts where ohm's law is explored. Aparently it can mean different things when you try to change it to prove poor theory.

[dcb]

Originally Posted by aerohead

At 80-mph ( not uncommon and actually legal in parts of Texas ) the SAE discovered that any benefit of small displacement is virtually lost.

Given the current state of aerodynamics and rolling resistance, yes. Make cars slipperier and smoother and smaller in frontal profile and you get more benefit from a smaller engine at higher speeds.

[Formula413]

Originally Posted by johnmyster

The idea is that if you can hold the intake valve open during part of the compression stroke, you can spit out some air and operate at "part throttle" even without a throttle plate. Simply throttling at the valve through low lift or low duration doesn't rid you of pumping work losses since the piston (the pump) still sees vacuum during the intake stroke.

Oh I get it now, so the idea is to not "throttle" the incoming air at all, thus eliminating vacuum. This would get very complicated, the injectors would have to be in on the act too, because you wouldn't want the injector to pulse while the intake valve is still open and bleeding off excess air. Not that it can't be done of course.

I have been in love with the idea of the camless valvetrain ever since I learned of the concept. The potential for maximum efficiency across the entire RPM range with absolutely no compromises, no tradeoffs of low end VS top end, power VS economy etc. It makes the camshaft seem as sophisticated as a horse and buggy.

[johnmyster]

Right. I dunno if direct injection was a part of the plan as well.

I think some of BMW's prototypes involved electric actuators. Somone out there was using hydraulic actuation as well, forget who, but I knew some of the engineers who were making the servo-hydraulic valves - similar to the control valving on some modern servo-hydraulic diesel injectors. INTENSE machining operations there. I assisted in drafting up patent applications for some of that stuff at the time and was floored. Patent sketches are one thing, but they actually planned to produce this stuff.

Problem is that the electrics use a ton of electricity. While it's a fun experiment for laboratory exploration, packaging those into a car had issues. Imagine, MetroMPG could remove his alternator belt, his PS belt, his A/C, AND his timing chain/belt.

I worked tangent to a university research group that was working to fit piezo-electric stacks onto a briggs motor for lab research - as the piezo stacks react very quickly and with a smaller electrical requirement. If the days of the ICE weren't limited, we may see more of this going on.

[Formula413]

What I read about solenoid actuated valves was that cars will have to be converted to 42 volt electrical systems to provide the necessary power to operate them. As for hydraulic valve actuators, I believe these may actually already be in use on Formula 1 engines.

As you pointed out, the question now becomes will the ICE be around long enough to warrant making the investment of time and funds to develop this technology?

[roflwaffle]

Originally Posted by RH77

First welcome...

Next -- I tried this 3 years ago by running my 4-cyl as two, by switched injector deactivation. Forget it if you're running an oxygen sensor, it will not work. An engine swap would be easier...

RH77

It should be a bit easier w/ 6s/8s when they shut off a bank since they tend to have a oxygen sensor for each bank and maybe something post cat. Unhooking the post cat and deactivated bank sensors would probably result in thrown codes but it should still run at ~stoich via the feedback from the activated sensor/bank. I think knock sensors may also hurt efficiency by retarding timing but I'm not sure about that one. The best way to figure this out would be a test I suppose.

[mwpiper]

Simply throttling at the valve through low lift or low duration doesn't rid you of pumping work losses since the piston (the pump) still sees vacuum during the intake stroke.

You get some of that energy in pulling against the vacuum back during the compression stroke when the vacuum pulls the piston up. Throttle plates cause significant internal energy loss due to the turbulence they produce. It's not isentropic. Changing volumes by moving a piston can theoretically be isentropic. It's not because of the friction involved, but the friction is there anyway. So the wider you open the valve, the more efficient it will be since limiting the intake valve motion simply turns it into a throttle.