> The turbo-charged, 2-liter, four-cylinder [VC-T] engine averages 27 percent better fuel economy than the 3.5-liter V6 engine it replaces.
You don't say.
Nissan Motor Company has announced a new type of gasoline engine
101–110 of 152 posts
Re: Nissan Motor Company has announced a new type of gasoline engine
#102This is still using ignition timing and spark plugs. Additionally, the connecting shim and the timing advancer/retarder introduce not one, but two points of failure. Thanks, but no thanks: I'll just stick to my simple (by comparison) direct injected turbo diesel cars. When there is a gasoline engine which can ignite the fuel without spark plugs and ignition timing, that'll be the right solution. mazda experimented wi…
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.
Re: Nissan Motor Company has announced a new type of gasoline engine
#103Earlier quoted context omitted.
I think the point of the person you replied to is that any variation in octane is handled by the fuel injection system. This renders having two tanks unnecessary (unless you require more distance between fill ups).
It can adapt to lower octane fuel by adjusting the timing, it's far from optimal, and at high enough boost level you need higher octane regardless. At non boost levels, you need less octane rating to prevent knock, but under boost you need higher octane rating. So you run the higher octane fuel all the time, and that is less efficient.
Correct. This involves relying on feedback from knock sensors which literally "listen" for the specific tone that a detonation event produces (usually somewhere in the 6-7 kHz range depending on cylinder geometry). You will sometimes hear this phenomenon referred to as "pinging", and it’s actually audible to the driver if severe enough. There is also another method of knock detection which involves using the spark plugs to detect the resistance of the air inside the combustion chamber immediately after an ignition event, which I believe is an indirect way of measuring cylinder pressure. I’m not positive on this, but I think the idea is that you want peak cylinder pressure at the moment of time where the piston is like 20 degrees after top dead center. Earlier than that, and the majority of the force is wasted pressing directly down on the crank shaft. This is more advanced and is used only in specific cars such as the E90 BMW M3.
If the ECU detects knock, it will retard timing. This works to an extent, but you’re ultimately worse off than if you just ran premium fuel in the first place. The other issue is that (on systems with conventional knock sensors) this causes you to basically “bounce” off of the knock threshold. Knocking is terrible for the bearings inside of the engine and should generally be avoided, but running regular fuel in a car that calls for premium results in the ECU constantly trying to creep up timing (or switch to the high octane map), only to be confronted with knock again.
Re: Nissan Motor Company has announced a new type of gasoline engine
#104The way that makes most sense to think about this to me is in terms of dynamic compression.
At full throttle the turbo is shoving a large mass of air into the cylinder for every firing. The compression ratio has to be fixed lower to control detonation under these circumstances.
At light throttle / cruise there is now hardly any mass of air in the cylinder, so although mecanically nothing has changed (same / fixed compression ratio) we are hardly compressing the air at all and we're giving away a load of efficiency for that reason.
The ability to up the compression ratio at cruise / light throttle claims some of that basic efficiency back.
Re: Nissan Motor Company has announced a new type of gasoline engine
#105> The turbo-charged, 2-liter, four-cylinder [VC-T] engine averages 27 percent better fuel economy than the 3.5-liter V6 engine it replaces. You don't say.
... with comparable power and torque.
Re: Nissan Motor Company has announced a new type of gasoline engine
#106This is still using ignition timing and spark plugs. Additionally, the connecting shim and the timing advancer/retarder introduce not one, but two points of failure. Thanks, but no thanks: I'll just stick to my simple (by comparison) direct injected turbo diesel cars. When there is a gasoline engine which can ignite the fuel without spark plugs and ignition timing, that'll be the right solution. mazda experimented wi…
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 combustible. Gasoline fuel is not flammable, but the vapor is, did you know that? That's what makes it volatile as far as combustibility, otherwise we would have self igniting gasoline engines by now.
Re: Nissan Motor Company has announced a new type of gasoline engine
#107Earlier quoted context omitted.
The electric motor to be used would have to be a pretty unusual motor. IMO, supercharging is "better" because the PTO side of an engine is less ... trouble than the exhaust side. Superchargers are generally heavier.
Super chargers generally result in a fairly large parasitic loss to power it. Turbo more or less harvest free energy with only a minimal loss due to increased back pressure.
So they say. The story I always got is that turbo ( for aviation - where this all grew up ) was simply lighter.
The old rule of thumb "turbo costs 3x less than super" is true for a lot of cases. Supercharge provides a linear boost where turbo does not.
Re: Nissan Motor Company has announced a new type of gasoline engine
#108> The turbo-charged, 2-liter, four-cylinder [VC-T] engine averages 27 percent better fuel economy than the 3.5-liter V6 engine it replaces. You don't say.
I'd like to hear a bit more about their definition of "comparable power and torque".
Re: Nissan Motor Company has announced a new type of gasoline engine
#109I have a lot of respect for Nissan's engineers, but somewhat less respect for their lawyers, who hounded Uzi Nissan for a decade trying to get him to turn over his domain. http://www.nissan.com/Lawsuit/The_Story.php Cybersquatting is obnoxious, but once they found out it was the guy's actual name, and that he was using it to run his own business, they should have just accepted he had a right to the site and worked to…
Lawyers are tools. (Being one, I feel I can say so, with a humble degree of confidence.) Certainly there's a give-and-take between lawyers giving advice and clients taking it, but by the "big X" their lawyers essentially do what they are told - lest the big client move elsewhere. All to say: Lawyers doing a bad thing are often a symptom of an internal disease or conflict. Which is to summarize a whole host of conflic…
> lawyers essentially do what they are told
Well, people defending themselves about doing bad things by stating that they are just doing what they are told are rightfully criticized. Even more so when they are in a high end profession.
Re: Nissan Motor Company has announced a new type of gasoline engine
#110Earlier quoted context omitted.
Super chargers generally result in a fairly large parasitic loss to power it. Turbo more or less harvest free energy with only a minimal loss due to increased back pressure.
So they say. The story I always got is that turbo ( for aviation - where this all grew up ) was simply lighter. The old rule of thumb "turbo costs 3x less than super" is true for a lot of cases. Supercharge provides a linear boost where turbo does not.
Some superchargers provide linear boost, others behave much like a turbo. In any casem FI is used to increase efficiency, so it doesn't make sense to use a super charger with a must larger parasitic loss. Modern turbo can provide boost from 1500 rpm, and result in a flat torque curve - the only negative thing is the lag.