Japanese Engines

[iroc-z89]

Bleh in here, I want to learn. Please explain to me how how these engines work. Camshaft wise anyways. I understand that a standard v-tec has a single cam with the larger v-tec lobe whuch it switches to a a specified rpm. My question to you is, how does the engine switch to that lobe, or multiple cams, you have to remeber i work with very old engines, so the new block designs confuse the heck out of me. And how do they use the 4 valves per cylinder idea, do both valves work of the same lifter/rocker arm setup or are they all independent of each other. As far as my engine knowledge i am still in the late 70's. To me a superram, miniram and whatever else are just variations of the old ramjet. Yeah im that bad. But i wanna learn.

[wEstSide]

Check out this site: http://www.autozine.org/technical_school/engine/vvt_2.htm#Cam-changing

He explains everything (SOHC VTEC).

http://www.autozine.org/technical_school/engine/tech_engine_2.htm#3-to-5-valve

That explains 4-valve tech and also has an explanation of the variable intake manifold further down.

[iroc-z89]

May 1997...... Is this in the states yest?

MITSUBISHI'S NEW GDI SYSTEM. Mitsubishi now has a production direct injection gasoline engine that reportedly delivers 35 to 40 percent better fuel efficiency than an indirect multiport injected engine. The engine also puts out 10 percent more torque and meets all emission requirements, including the ones for oxides of nitrogen (NOX) which are especially tough to meet.

The Gasoline Direct Injection (GDI) engine, which is expected to be a forerunner of the next generation of high-efficiency, low- emission engines, is currently being produced in Japan and will be introduced in Europe later this year. The engine is slated to make its debut in the U.S market by the year 2000.

The GDI engine runs on an ultra lean (40:1) air/fuel ratio at idle by using special injectors that produce a "stratified" charge in the combustion chambers. Regular gasoline fuel injectors produce a fine cone-shaped mist that's necessary to create a homogeneous air/fuel mixture. The high pressure GDI injectors, by comparison, produce a very compact spray pattern that forms a swirling cloud of fuel particles. This, combined, with a "reverse tumble" air flow in the cylinders creates a layered effect (stratified charge) of air and fuel in the cylinder that is rich in the immediate vicinity of the spark plug but is progressively leaner further out.

One of the keys to making this work is the way air is directed into the cylinders. Most engines have horizontal intake and exhaust ports so air and fuel enter past the intake valve, blow past the spark plug and swirl back around the cylinder in a circular path before being ignited. In the GDI engine, the intake port is almost vertical. Air flows down from the top, enters past the intake valve and injector, flows down the side of the cylinder until it hits a cup shaped pocket in the piston dome that redirects it back up towards the spark plug. This "reverse flow" arrangement combined with relatively late injection timing in the compression stroke allows the engine to handle very lean mixtures at idle without misfiring. When more power is needed, injector timing is advanced earlier in the compression stroke and more fuel is injected into the cylinder to create a more conventional fuel mixture.

Lean burn engines that produce exceptionally low carbon monoxide and hydrocarbon emissions have usually had problems meeting NOX emission standards because elevated combustion temperatures increase the formation of NOX. But the GDI engine overcomes this problem by using more exhaust gas recirculation (up to 30 percent EGR flow rate) to dilute the incoming air, and a special blend of catalysts in the catalytic converter. The result is a 97 percent reduction in NOX emissions compared to a conventional engine says Mitsubishi.

The GDI engine is a dual overhead cam design that displaces 1.8 liters and has a compression ratio of 12 to 1. The injectors operate at pressures approximately 15 times higher than ordinary indirect gasoline injectors.

It's obviously going to be awhile before this technology starts turning up on cars here, but it is a preview of what's to come as the auto makers scramble to meet the next tier of low emission standards coming out of Washington D.C.

Like the all the fuel injection systems that have come before it, the new direct injection engines will still require replacement parts and will likely suffer from similar injector woes that plague today's engines. In fact, direct injection injectors may prove to be even more troublesome than today's indirect injectors because they're exposed directly to the heat of combustion. Time will tell.

[wEstSide]

I doubt it. I'm pretty sure lean burn engines aren't allowed here.

[bleh]

I doubt it. I'm pretty sure lean burn engines aren't allowed here.

not yet. polution problems. the civics hx and vx work on lean burn but not with a 40:1 ratio.

ok incase you didnt get it yet, normal vtec in a nutshell:

when the oil pressure reaches a certain point and the ecu read the correct rpm the cam(s) switch from the smaller econo/smooth idle lobes to the larger performance lobes. this works with both single and dual overhead cam engines.

i-vtecis similar with the 2 or more lobes but it also not only adjusts ignition and fuel timing but also cam timing, allowing it to optimize the power at any given airpressure/temp ,throttle position and rpm. this also allows for a higher compression ratio on a daily driven car due to the fine tuning and also making a much fatter torque curve, which is why hondas will have an average torque per displacement but above horsepower.

if you have any questions keep asking. but now there is a 3ft swell and im goin surfing.

[wEstSide]

I have a friend with a VX, I'll ask him about it.