Engine technology thread.

[serialk11r]

Yea that's kinda what I was getting at, an electrically assisted turbo probably needs to be geared in some way but then the electric motor would still be useless under some circumstances since a turbo operates at such a wide rpm range.

The thing with the valvetrain revolution is that companies have all been talking about it for a long long time but now that fuel efficiency regulations are getting quite strict they will probably NEED to push R/D for the first time. So hope is there! I believe the limit for cam actuated systems would be something like Fiat Multiair on both exhaust and intake, with a Ferrari style moving intake cam. That would be very close to ideal operation. The way a cam lobe is shaped is pretty good, the lift is lower when the piston is moving more slowly, and hits maximum lift when the piston is moving the quickest, although of course the lobe shape can't be perfectly optimized for all conditions. I think the next step would be moving away from traditional 4 stroke engines as they have rather high frictional loss. You could eek out a little more with a fully hydraulic system but then such a system would have greater energy consumption (the only losses in cam actuated systems is friction, and a little bit of inertial; the compressed springs return their energy to the cams).

I imagine someone will attempt to implement fully hydraulic valves though, Fiat Multiair shows it's quite possible to control flow of an actuating fluid at very high speeds. Replacing the cams and followers with a small piston and variable pressure hydraulic system would give us nearly full control over valve timing. But then response time might be not as good. I can't really see anything giving much benefit over a plain old cam with all the previously described optimizations tacked on.

Oh and yes, I believe F1 mandates cam actuated poppet valves. They use compressed air canisters in place of springs though, since there's no mandate on that.

[Dimman]

Advances can be a loooong time coming.

Take the recent eVVT-i. VVT-i with electronic control instead of hydraulic.

Now I can't find the date on this scan, but they mention that the first edition of this document was in 1981, and this is the second, plus there is a graph of the 'current' cars that ends in 1985.

So assume this is from 1985:

http://www.3sgte.com/page_20.htm

http://www.3sgte.com/page_21.htm (diagram of it on this page)

Variable Valve timing using a stepper motor. Concept in 1985ish... Just got here a year or two ago???

[serialk11r]

Yea but that sort of thing leads me to wonder how actively they were pursuing it. All of variable valve timing is pretty simple in concept, companies just probably didn't feel the need to bring it to the market, which takes time to test and refine.

[Dimman]

A question that pesters me when I start looking into 'outside the box' Toyota swaps for another Supra: WTF is the reasoning behind a slave-cam DOHC setup?




Why not just go SOHC with rockers to save manufacturing costs? Plug placement? Some other reason?

[Snaps]

Just taking stabs here.... Simplicity? It would mean you don't have to set the timing for both cam gears when you change the cam belt, just have to set it for one?

What about the valve setup? To use 4 valves (rather than 3 or 5 and offsetting the cam lobes)? That said, are there any engines that use SOHC with 4 valves (I asssume so). Would it not be harder to have a single camshaft moving all 4 vavles and still have the correct (different) duration/lift for both the intake and exhaust valves, even when using rockers?

[PuGZoR]

I heard that BMW are developing a V6 with three turbochargers. There's 2 conventional ones (one per bank of cylinders) as well as an electric turbocharger... which I think is actually a supercharger.

Electric turbo/supercharging CAN work, but traditionally people have made very poor efforts at it. Where it's mostly gone wrong is that they've use really low powered electric motors with inefficient fan designs.

What you'd want to do is get something equivalent to a modern supercharger (any type), but instead of driving it from a belt you'd want to hook it up to a 10kw electric motor. It could be hooked up to the same kind of regenerative charging system used on hybrid vehicles too, and only engage when the engine is under significant load and sit at a low idle the rest of the time.

[serialk11r]

Originally Posted by PuGZoR

I heard that BMW are developing a V6 with three turbochargers. There's 2 conventional ones (one per bank of cylinders) as well as an electric turbocharger... which I think is actually a supercharger.

Electric turbo/supercharging CAN work, but traditionally people have made very poor efforts at it. Where it's mostly gone wrong is that they've use really low powered electric motors with inefficient fan designs.

What you'd want to do is get something equivalent to a modern supercharger (any type), but instead of driving it from a belt you'd want to hook it up to a 10kw electric motor. It could be hooked up to the same kind of regenerative charging system used on hybrid vehicles too, and only engage when the engine is under significant load and sit at a low idle the rest of the time.

So this is like the point of an electrically coupled turbo. It is in fact an independent turbine for electricity generation and compressor for boost. If you have just the supercharger, you lose a crapton of efficiency because you have a lot of energy going out the exhaust for nothing. Someday cars might have a small turbine in the exhaust for power generation, and an alternator that is geared so that it is optimized for power production at idle, and decoupled at higher speed. Under acceleration and cruise, there is always leftover pressure in the exhaust which can be used. To minimize backpressure a volume-maximized exhaust manifold can be used.

[serialk11r]

Originally Posted by Driftster

any word on the ring lands, oil and coolant gasket paths and whether it'll have dual AVCS?

lol there's no news on the engine obviously, we're still waiting.
But being a brand new engine in 2012 suggests it will have some kind of sophisticated variable valve control. Phasing on exhaust for sure, I'd think intake would have more than just phasing.

[serialk11r]

I mean I'm still speculating, but it's going to be pretty hard to hit performance targets without exhaust phasing and a pretty advanced intake system. Not to mention exhaust phasing can help with low load fuel efficiency.

[serialk11r]

The FB does have dual AVCS, most current engines do have a similar system or better. AVCS isn't that hard to implement, it's just one piece that replaces the cam gear with one that can move within it, and the relevant hydraulic controls. Subaru said they were even planning to add direct injection to the FB series I think.

[serialk11r]

What about it?

[Dimman]

The FB has separate cam carriers (ie think modular) in its design. They have options on what they can do with it.

Remember the EJ is like a million years old and it's gone back and forth from SOHC to DOHC over the years with various combinations of AVCS/AVLS, as well as open, closed and semi-closed deck block variants.

What the first peak at the FB in the Forester means to the FT86 is basically nothing.

Edit: Missed the ring lands comment. Heh... Hopefully they sort that out for this one.

[MrVito]

timing chain guides turn into noisemakers in a hurry.

[serialk11r]

So you guys being really bored I found myself reading about positive displacement vs. centrifugal pumps today and I realized something about turbos: at a high pressure ratio the compressor operates at high efficiency for only a short amount of time. For high boost applications (like over 14psi average), theoretically it would be better to have twin sequential turbos but with the compressors hooked up in SERIES and of course sized properly. Jet engines use this to get its compressors and turbines operating closer to their best speed.