A few noobish questions

[bdanisi]

OK eff it I'm spilling my purse on the table haha. Seriously can someone help me understand how vtech works? How does it kick in, yo? Seriously I don't get it. I also was wondering why more performance vehicles aren't diesel from my minimal Wikipedia knowledge it seems to be pretty efficient but slightly more dirty? I also was wondering if going forced induction not only increases acceleration but also top speed? I had one more I can't remember, I'll add it later if it comes back.
Thanks

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[vividracing]

[sklimo]

[Luis_GT]

That's why you get a car with a push button... that way you don't have to waste time searching.

[luuser75]

Did somebody say vtech?

[bdanisi]

Ah can always count on the off topic section to turn into meme fodder haha

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[King Tut]

VTEC cam shafts have two different lobe profiles. When VTEC kicks in a solenoid and oil pressure change the valves from opening on one set of lobes to the other set of lobes. Diesel is worse for the enviornment and the only reason more diesels are finally making it over here are their high compression, direct injection, and great MPGs. Advancements such as diesel exhaust fluid injection have helped clean them up. Forced induction increases horsepower which also increases acceleration. Top speed is infuenced by both horsepower, gear ratios, and the coefiecient of drag for the vehicle.

[bdanisi]

Originally Posted by King Tut

VTEC cam shafts have two different lobe profiles. When VTEC kicks in a solenoid and oil pressure change the valves from opening on one set of lobes to the other set of lobes. Diesel is worse for the enviornment and the only reason more diesels are finally making it over here are their high compression, direct injection, and great MPGs. Advancements such as diesel exhaust fluid injection have helped clean them up. Forced induction increases horsepower which also increases acceleration. Top speed is infuenced by both horsepower and the coefiecient of drag for the vehicle.

That is the most boss response I've ever recieved on the forum

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[strat61caster]

1. [ame="http://en.wikipedia.org/wiki/VTEC"]VTEC - Wikipedia, the free encyclopedia[/ame]

Read the article. Ok so basically, nope go read it.

2. Basically what you said, they were unsuccessful historically (due to development costs and legislation) so they didn't receive as much attention as Otto engines (kind of like the rotary). Due to advances over the last 20 years I would not be surprised at all to see a competitive diesel sports car come to market in the next 10 years. VW/Audi have competitive diesel cars on the market right now, they tried an R8 TDI but didn't think they could recoup the costs, too expensive. That's really all it is, the costs are high and the demand isn't there yet. When the demand arrives so will the cool stuff.

Hell give me the seed money and I'd love to start a company that uses VW diesels in a roadster chassis, similar performance to the Miata and Toyobaru while delivering 30+ mpg and the option of alternative fuels. Diesel will outlast Otto.

3. What does forced induction do to an engine? Think about it for a bit. Basically it increases the amount of air and fuel you're combusting, more powah. Extremely simply speaking top speed is limited by the amount of power the engine outputs, the aerodynamics, and the gear ratios. It's all a balance of equations F=ma. The faster you go the more wind resistance increases which requires more power to overcome it, so assuming the two cars have the same aerodynamics and are not limited by the gearing, the car with more power (forced induction) will be able to achieve a higher top speed.

Looking up the BRZ top speed videos, there's still another 900 rpm left on the tach at 146 mph, the engine doesn't have the power to overcome the wind resistance. With a turbo tuned for power (and the requisite mods to beef everything up, maybe the full Crawford kit) I would not be surprised to see the car hit redline in 6th gear hitting a speed of ~168 mph.

Ok fine I'll give you a tl;dr for the Vtec.
So if you understand the basics of how camshafts work you understand that a larger cam profile will result in more valve lift which gives you more air/fuel in the chamber which gives you more power at the sacrifice of economy. Vtec is two camshafts in one, an economical camshaft and a performance camshaft. This means you can get all your eco box 30 mpg at normal driving speeds at low rpms and with a stomp of a foot get screaming 200 horses out of the same 4 banger. Once upon a time a manufacturer had to choose one mode of operation, usually somewhere in the middle for the average consumer, that's why old school tuners will go for a camshaft that offers more lift. Nowadays things are so optimized and with variable valve timing the benefits have shrunk as oems can offer better performance without sacrificing economy