Why do they still make car alarms? (2015) • Hacker News Board

Re: Why do they still make car alarms? (2015)

#531

Post by culopatin » Thu, Jan 21, 2021, 8:02 PM UTC

mrfusion wrote: post #369

spiritplumber wrote: post #100

I have an older RV that people sometimes try to steal (it's usually meth heads wanting to live on it; I've taken to leaving a plaque on the dash saying that if they want a hot meal instead, just knock on my door). The alarm is aftermarket, and silent. All it does is make the fuel pump go in reverse. (The fuel pump is also aftermarket) It's been hilarious a couple times.

I never understood why we need a fuel pump and a fuel injector .. and a valve that opens to let fuel in the cylinder.

Tank is in the back. The injector only works properly at elevated fuel pressure otherwise it would just drip out. Like a shower head with no pressure, it would just dribble out.

Valve lets in a mixture of air and fuel, not just fuel, and allows compression to happen. If that wasn’t the case you’d have to have a mixture injector that closes during compression and explosion. Without it, the explosion would expand in the intake runner instead of pushing down the piston.

Re: Why do they still make car alarms? (2015)

#532

Post by mrfusion » Thu, Jan 21, 2021, 9:04 PM UTC

culopatin wrote: post #531

mrfusion wrote: post #369

Earlier quoted context omitted.

I never understood why we need a fuel pump and a fuel injector .. and a valve that opens to let fuel in the cylinder.

Tank is in the back. The injector only works properly at elevated fuel pressure otherwise it would just drip out. Like a shower head with no pressure, it would just dribble out. Valve lets in a mixture of air and fuel, not just fuel, and allows compression to happen. If that wasn’t the case you’d have to have a mixture injector that closes during compression and explosion. Without it, the explosion would expand in th…

Thanks. So does the injector get fuel on the back of the valve when it sprays?

Re: Why do they still make car alarms? (2015)

#533

Post by earthboundkid » Fri, Jan 22, 2021, 1:27 AM UTC

ineedasername wrote: post #515

earthboundkid wrote: post #513

Earlier quoted context omitted.

The “fall on hard times” crowd hasn’t always lost their homes. For instance, it doesn’t matter how bad the famine was in feudal times, the lord wasn’t going to kick you off the land. Losing your home to foreclosure requires a modern economy.

That isn't quite true. It was not uncommon for the British lords to kick Irish off their lands. I have a hard time believing that was a unique circumstance throughout the history of various forms of feudalism. See also the practice of "Enclosure" for an additional example. In addition, being a peasant often had some properties of slavery: no freedom of mobility or choice and sometimes lack of pay, with the express ap…

1. “Enclosure” is the defining act of modernization, so it doesn’t really say anything about feudal times.

2. I’m not arguing that feudalism was good. I’m arguing that homelessness is a historically embedded phenomenon, and was essentially non-existent in pre-modern times and then it became markedly more prevalent in the last 40 years. I’m not sure about all the causes of or solutions to homelessness, but I do think if it were the priority, homelessness could be resolved at the price of imposing some other trade off problems (which might be worse on net).

Re: Why do they still make car alarms? (2015)

#534

Post by bhandziuk » Fri, Jan 22, 2021, 5:07 AM UTC

yason wrote: post #476

bhandziuk wrote: post #220

Earlier quoted context omitted.

This drives me crazy about my Acura. I want it to honk so I know the car is locked or so I can find it in a parking lot. Instead it does a tiny muffled whimper that is functionally useless.

If the car honks or flashes its indicator lights doesn't mean the car is locked. If one door is slightly open the locks will generally unlock immediately, regardless of the sounds/lights. A more reliable way is to listen to the lock motors click once in unison but not twice. I often push the lock button and just try one door myself before leaving the car.

That's nice if your within hearing of the subtle lock sounds

Re: Why do they still make car alarms? (2015)

#535

Post by culopatin » Fri, Jan 22, 2021, 1:56 PM UTC

mrfusion wrote: post #532

culopatin wrote: post #531

Earlier quoted context omitted.

Tank is in the back. The injector only works properly at elevated fuel pressure otherwise it would just drip out. Like a shower head with no pressure, it would just dribble out. Valve lets in a mixture of air and fuel, not just fuel, and allows compression to happen. If that wasn’t the case you’d have to have a mixture injector that closes during compression and explosion. Without it, the explosion would expand in th…

Thanks. So does the injector get fuel on the back of the valve when it sprays?

Unless it’s direct injection, yes. It sits there for a little bit mixing up with the air. Also the hot valve vaporizes the fuel a bit more.

In direct injected engines, the injector shoots on the piston.