I've been reading a lot about the new 48 volt engines coming with mild hybrid systems. they say one of the advantages is the lack of accessories belts for the AC, water pump and such. Basically it has no accessory belt.

I thought however that our hybrid engines already achieved that. didn't we do away with accessory belt for the most part? How big of a deal is this 48 volt engine thing? just curious.....

 

Hybrid engines have only water pump belt, aka accessory belt.
Personally, I do not bother much with any gasoline engine "advancements" They are marked for slaughter in the next 5-10 years, I simply sit and wait for a decent mileage electric SUV to come out. Toyota plans on offering full electric by 2018 and about RX sized SUVs doing over 300km range are already produced and, by no means, am I referring to Tesla.

 

full hybrids are a lot better than 48v... they are comparing them to non-hybrids with start stop systems, and 48v are improvement there since they give engine shut-off during slowdown as well when you are nearing the stop, not just at the stop... they also offer some extra power, in general about 1/3 of normal hybrids.

I think it is quite questionable if these will be worth the extra cost and weight, but lets see, first mild hybrid systems were completely useless.

There are few good articles about it like here:
https://jalopnik.com/everything-you-...olt-1790364465

 

I don't see the internal combustion engine going away anytime soon, but it looks like the 48v system is trying to milk some of the significant gains offered by pure hybrids. Same basic ideas are applied--shut off the engine when not needed, run accessories off of electricity.

But to show that these systems are still small steps, keep in mind that a Toyota hybrid battery is about 300 volts, not 48. Also, the battery chemistry is Ni-MH, not Lithium, so it will last forever. And the electronics in a Toyota hybrid can double the 300 volts when driving the electric motors, so there is a major boost in horsepower compared to the 48v systems.

And then there's the beauty of the stone-cold simple "transmission" of a Toyota hybrid.

 

 

A 48 volt hybrid system replaces both the starter and alternator with one single, more robust motor-generator. It is a very simple, mild-hybrid system when compared to Toyota's full-hybrid system, which has been beltless for some time now.

When fed with electricity, the motor can start the engine and provide a little bit of electric drive assist when starting out (when the internal combustion engine uses the most fuel). And with this more robust, powerful motor acting as starter, the engine can be shut off when the car is stopped (in traffic or at stoplights) and re-start much smoother than with a normal starter.

Once the engine is running, the starter switches over to generator mode, being turned by the engine to generate electricity to recharge the battery. When the battery is fully charged (or when full power from the engine is required), the generator can switch off so that it does not provide a full-time drag on the engine, as an alternator would. There are no engine-dragging hydraulic accessories, only electrical accessories, which run off the battery rather than the alternator.

The 48 volt hybrid vehicle will be more fuel efficient than a normal internal combustion engine car (mainly due to the fact that the engine can shut off when stopped and because all accessories are electrical) but will not be as fuel efficient as a full hybrid.

Another electrical accessory that can be used in a 48 volt electrical system is an electrically-driven compressor, giving you an electric-supercharger (more commonly known as an electric turbocharger).

What the 48 volt hybrid system gives you is a simpler electrical system. Rather than the Toyota hybrid system's dual, parallel 12 volt system for electrical accessories and very high voltage for the hybrid system, the 48 volt hybrid runs both accessories and hybrid drive on the 48 volt electrical system. This allows for more powerful accessories (including the electric compressor) but a weaker electric (hybrid) drive system.

 

I think I read somewhere that the Toyota hybrid system runs accessories off the 12v system with the exception of the A/C compressor and power steering. The A/C compressor is fed directly from the 300v traction battery, while the system inverter circuitry converts 300v down to about 40v dc to run the power steering.

So the 12v battery is used to power the computers, lights, radio, and miscellaneous items, while the high-voltage battery does traction, A/C, and power steering.

This is what I understand is done in the Highlander (and thus Lexus RX) hybrids. Other vendors I'm sure do different things. In any event, even the 48 volt systems also employ a separate 12v battery that powers the 12v devices, just as in a Toyota hybrid.

One odd statement from the article linked above: 48v cars start the engine at a traffic light via the beefy 48v starter-generator, but a conventional 12v starter motor is used when the engine is cold. Why?

 

I am guessing that Delphi developed their 48 volt hybrid system as a cheap and easy, plug-and-play add-on to an already existing internal combustion engine (look at how all the extras -- lithium-ion battery, etc. -- are very small in size). But I don't know what automakers would be in the market to buy such a system. Larger automakers would have developed their own systems and I cannot think of many smaller, independent automakers left out there that would buy an "aftermarket" system.

 

Interesting discussion, learning all the time. Thanks for posting the link, spwolf.

 

The R&D money spent on developing hybrid/BEV technology is staggering. I truly believe that if those dollars were spent, instead, on R&D of ICE efficiency, we'd have V6's and V8's that get 50/40 mpg with near 0 emissions by now. We'd certainly be better off and consumers would be happier.

 

There is work being done on improving the internal combustion engine.

Mazda is working on a compression-ignition engine, adopting and adapting the concepts behind the diesel engine -- and what makes it more efficient than traditional the gasoline engine -- to a new gasoline engine design.

Mazda also believes that it can improve gasoline internal combustion engine thermal efficiency up to greater than 50% (half of the thermal energy available in gasoline fuel actually converted to mechanical energy), which it says would make its ICE-powered cars as efficient as electric cars (that are powered by electricity generated at large fossil-fuel fired generating stations).

The newest diesel engines in cars now run at about 45% efficiency but diesel emissions (nitrogen oxides and diesel particulates) are still high, and very difficult and expensive to reduce.

Compare that with Toyota's newest Dynamic Force engines (the new 2.5 litre engine in the 2018 Camry is a Dynamic Force engine and among the most efficient in the world) run at about 40% efficiency, which is getting close to diesel engine efficiency; I believe that we will soon see new Toyota gasoline engines as efficient as diesel engines. Hybrid electric engines run more efficiently than normal gasoline ICE engines.

In the race to replace diesel-powered cars, electrification is the top priority right now because it is relatively easy (and inexpensive) to add an electric motor to an ICE or a transmission (the concepts are not new even though some technologies are new).

We need research into all of these solutions -- and others, such as hydrogen fuel cells and hydrogen-fired internal combustion engines -- because we know that it is not prudent to put all of our eggs into one (gasoline-fired ICE) basket. Due to the design of the piston-powered, reciprocating engine that has to turn linear (straight-line, back-and-forth) force to a rotational (circular) force, there are great limitations in the piston engine.

Mazda believes that it can get up to 50% efficiency or greater in an ICE but I am somewhat sceptical.

 

 

The ICE is very well understood. The diesel high-compression process represents about as good as things are going to get, and the Holy Grail for gasoline engines is to approach similar efficiencies. This is what "Atkinson Cycle" is all about, and I think all the fanciful names for carmaker's newfangled engines are marketing fluff. They are all trying to get a very high expansion ratio.

So that said, there isn't much more that can be done. It takes a certain amount of energy to push a 4,000 lb car at 70 mph on the freeway. There's air drag, there's moving-part friction, there's tire energy losses (sidewall flex takes energy). Certainly going up and down hills can become more efficient as regeneration becomes more commonplace; hybrids do this already. And certainly shutting off the ICE when it would otherwise be operating in an inefficient zone (high manifold vacuum) can be done, and hybrids also do this. But you won't find a 60mpg RX based on some breakthrough ICE technology. There's only so much energy that can be extracted from the fuel.

Anyway, that's my two cents.

 

Quoted today, that makes sense. However, people/engineers have been saying those exact words for 50 plus years, yet, look where we are today.
Multi valve technology, variable valve timing, direct injection, cylinder deactivation. The list goes on and on. Heck, a new Altima driving in downtown LA will have cleaner air coming out the exhaust than the air the engine takes in. Imagine how it would be in 50 more years. Seriously, it's been hundreds and hundreds of billions of dollars spent on hybrid/electric technology. I think that money could have been better spent and the outcome, much, much better.