121–130 of 152 posts
This is all moot. Battery technology and charging infrastructure for EVs will improve so much over the next 5 to 10 years that engines running on dinosaur juice will no longer be worth the hassle for mainstream vehicles.
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Disesl engines have very fine control of ignition timing via injection timing which is now very complex. There are tiny pilot injections and multiple short injections over a carefully controlled length of time so I don't agree that needing to time a spark makes spark ignition a more complex and by implication worse solution.
First of all, timing by injection is still simpler than timing by spark: in gasoline engines, the computer must time both the injection and the ignition. Second, timing by spark means that spark plugs are necessary, so that is more parts, and more parts means higher probability of failure. Third, spark plugs are needed to start a chain reaction of igniting fuel, because gasoline fuel is volatile enough as not to be c…
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Realistically, how often is a petrol I4 engine rebuilt in consumer cars? I've seen 1980's Volvo redblock engines with 300k miles on them run as smooth as butter. Short of neglecting timing belt changes, running without oil, or incompetent modifications, nothing much kills a petrol engine before the rest of the car is scrap.
Depends on the brand. Nissan engine quality has gone down in the last 15 years. Their flagship engine the VQ3XDETT has been good but the rest of the lineup has suffered. Its not yet as cas as a chrysler9 engine, but its not what it was during the 80s and 90s.
Here is a simple explanation gathered from this image http://o.aolcdn.com/hss/storage/midas/de3e84cf46030cd7b3ea39... : The difference from a conventional engine is that the engine stroke is increased or decreased automatically. The stroke is the distance the piston travels up and down in order to turn the crankshaft. A shorter distance that is closer to the combustion chamber increases the compression ratio because…
Clever design but that looks like a lot of moving parts. I wonder about longevity of the engine.
Here is a simple explanation gathered from this image http://o.aolcdn.com/hss/storage/midas/de3e84cf46030cd7b3ea39... : The difference from a conventional engine is that the engine stroke is increased or decreased automatically. The stroke is the distance the piston travels up and down in order to turn the crankshaft. A shorter distance that is closer to the combustion chamber increases the compression ratio because…
- The added maintenance of turbos
- Added cost might not be worth it compared to a hybrid or electric, especially used
How are they preventing engine knock ? At 14:1 compression you'd have to be running premium gas, which would pretty much cancel the efficiency saving, in a $$ perspective.
I think direct injection allows engines to run higher compression ratios without knocking. I'm not sure exactly why, but I assume it's because the fuel sprays directly on top of the piston which could allow it to cool any hot spots which would have normally caused detonation.
This is speculation.
Edit: looking at the posted image, they change the stroke depth of the power linkage. That plus valve timings let them customize the entire combustion cycle.
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I figure these engines won't be rebuilt. Its simpler to swap one in since its a four cylinder. The engine should operate OK in case the actuator stops adjust the stroke. There really isn't anything new in terms of parts. They simply took proven implementations of each part and applied them in a new configuration. The biggest issue might be cylinder bore degradation due to the variable stroke. I need to learn more abo…
Realistically, how often is a petrol I4 engine rebuilt in consumer cars? I've seen 1980's Volvo redblock engines with 300k miles on them run as smooth as butter. Short of neglecting timing belt changes, running without oil, or incompetent modifications, nothing much kills a petrol engine before the rest of the car is scrap.
Take some random engine, now engineer a oiling system that depends on having three different jets at each cylinder to ensure reasonable longevity. Now make the operation of those jets highly dependent on a maximum oil viscosity (small jet, low volume, thick oil would just dribble) and spec'ing the rest of the system for thicker oil (using bigger jets and so on) would be a needless waste of fuel (pumping around lots of thick oil takes more energy than the same amount of thin oil). Now tack on a heat exchanger so you can use the coolant system to bring the oil up to temp ASAP. Wash rinse repeat until the entire system is designed to have every part working together. Now you've got really long chain where any screw up by any supplier results in the whole system breaking down and a bunch of crap engines (or whatever major system you're designing) that wind up getting replaced under warranty at 75k (costing money, damaging reputation, etc., etc.).
The Nissan engine in the article is very much subject to this. Unless they want to leave a lot of performance on the table they've basically got two rotating assemblies they have to get right. That should be easy but for awhile every Hyundai dealership had pallets stacked up with v6 short blocks indicating that it's not that easy.
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Engine control computers are even more fun . A friend of mine works for Audi's/VW's supplier, and honestly my biggest surprise about the emission scandal was that the code actually worked. (They had to write their own linter, because they need to ship slightly broken code written by code generators, and last I heard Windows XP is still part of the compilation chain…)
I'm guessing you refer to AutoSARL when you talk about the code generation. Its insane that its an industry standard.
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Realistically, how often is a petrol I4 engine rebuilt in consumer cars? I've seen 1980's Volvo redblock engines with 300k miles on them run as smooth as butter. Short of neglecting timing belt changes, running without oil, or incompetent modifications, nothing much kills a petrol engine before the rest of the car is scrap.
The sub 200hp 80s turd can leak out all it's coolant and overheat. Chances are it will be just fine after the leak is fixed and the system is refilled. The same can't be said for most more modern things. When one part of the system craps out there's likely to be more carnage elsewhere, it's just part of the nature of a more refined system. Take some random engine, now engineer a oiling system that depends on having t…
Oh, most definitely this. My first car, '86 Volvo 240 with the B230E engine, had a coolant leak about two years before we scrapped it (in 2012). When the engine started overheating, you'd turn the coupe heater to max (and open windows all the way), since that tapped into the lowest part of the cooling system, so you got the temp down and could keep going for ~10 miles before refilling with water. Then as winter approached I bought a bottle of radiator fixer (about $20) which fixed the leak, did a full coolant change to get proper antifreeze, no problems afterwards.