Whats so special about VTEC engines???
- Thread starter PhatBimmer
- Start date
All it does is adjust the valve clearance/timing on the fly. It gives the engine higher horses at higher rpm's. Thing is, it might have a decent amount of power when the VTEC adjusts the timing -- which is over a certain rpm, but other than that, it is just a regular economy 4 banger. It gives the cars a torque curve that looks like a mountain, instead of a flatter torque curve.
A 190 hp vtec engine revving from 1000 - 7000 rpm cant touch a 190 hp BMW or Audi engine doing the same, becuase the european engines have a very flat torque band. BMW is now using the same basic system on their engines, except they are using the system on an already "torquey" engine.
So, why the pride? It makes them feel special if their 1.6l engine has VTEC and is maybe 30 hp more powerful than their buddy's 1.6l engine without vtec.
A 190 hp vtec engine revving from 1000 - 7000 rpm cant touch a 190 hp BMW or Audi engine doing the same, becuase the european engines have a very flat torque band. BMW is now using the same basic system on their engines, except they are using the system on an already "torquey" engine.
So, why the pride? It makes them feel special if their 1.6l engine has VTEC and is maybe 30 hp more powerful than their buddy's 1.6l engine without vtec.
good link; last paragraph explains what bmw, porsche, etc. and some higher end japanese car companies are doing.
http://auto.howstuffworks.com/question229.htm
http://auto.howstuffworks.com/question229.htm
The main benefit of VTEC is that the resulting engine is very versatile. The torque curve is very flat: among the flatest of all the engines on the market. (Its not like a mountain)
VTEC is an acronym for Variable valve Timing and lift Electronic Control. It is a mechanism for optimizing air/fuel mixture flow through the engine.
An internal combustion engine converts the chemical energy stored in fuel into thermal energy. The increased thermal energy within a cylinder causes the pressure to build. This pressure acts on the pistons and the result is a mechanical force rotating the crankshaft. This mechanical force is measured as crank torque. The ability for the engine to sustain a certain level of crank torque at a certain RPM is measured as Power. Power is the rate at which the engine can do work. This conversion process is not 100% efficient. In fact, only about 30% of the energy stored in the fuel is actually converted into mechanical energy.
Physics says that for a given efficiency level, a higher rate of fuel consumption is needed for the engine to generate power. So it becomes obvious that if you want more power, you need to increase the rate of fuel combustion. One way to achive this goal is to have a bigger engine. A bigger engine with larger cylinders will be able to combust more fuel per rotation than a smaller engine. Another method is to pre-presurize the fuel/air mixture and cram it into an existing engine size. Thus even though the cylinder size stays the same, more fuel is combusted per rotation. This second method is referred to as forced induction.
Honda chose to explore another method: keep the engine size the same, but turn the engine faster to consume more fuel. Here is an analogy: You want to move foam peanuts from one bucket to another with a cup. You can increase the size of your cup, compress/cram as much peanuts as possible into the cup each time, or you can just move the cup faster. All three methods moves more peanuts. Honda uses the last method. And again, more fuel combusted equals more power generated by the engine.
As the engine speed is increased, more air/fuel mixture needs to be "inhaled" and "exhaled" by the engine. Thus to sustain high engine speeds, the intake and exhaust valves needs to open nice and wide. Otherwise you have what is akin to athsma: can't get enough air/fuel due to restrictions.
If high speed operation is all we have to worry about, Honda wouldn't need to implement VTEC. Indeed, race engines that operate mostly at high rpms do not utilize any mechanism like VTEC. But street cars used for daily driving spend most of their time with the engine at low RPMs. Valves that open wide for high RPM operation contributes to rough operation and poor fuel economy at low RPMs. These undesirable traits are directly against Honda's design goals.
The solution that Honda came up with is the VTEC mechanism: open the valves nice and wide at high RPMs, but open them not as much at low RPMs. So now you have a engine with smooth operation at low RPMs, and high power output at high RPMs.
And that is basically what VTEC is. It's nothing magical. The idea has been around for a long time. Honda's VTEC is just a very simple, elegant and efficient implementation that is extremely effective at achiving its design goal. Honda automobiles are the first among modern automobiles to utilize this mechanism in such a large scale of distribution.
If you want much much more information on the vtec engine and how it works, visit this link (where i got this information from)
http://www.leecao.com/honda/vtec/index.html
VTEC is an acronym for Variable valve Timing and lift Electronic Control. It is a mechanism for optimizing air/fuel mixture flow through the engine.
An internal combustion engine converts the chemical energy stored in fuel into thermal energy. The increased thermal energy within a cylinder causes the pressure to build. This pressure acts on the pistons and the result is a mechanical force rotating the crankshaft. This mechanical force is measured as crank torque. The ability for the engine to sustain a certain level of crank torque at a certain RPM is measured as Power. Power is the rate at which the engine can do work. This conversion process is not 100% efficient. In fact, only about 30% of the energy stored in the fuel is actually converted into mechanical energy.
Physics says that for a given efficiency level, a higher rate of fuel consumption is needed for the engine to generate power. So it becomes obvious that if you want more power, you need to increase the rate of fuel combustion. One way to achive this goal is to have a bigger engine. A bigger engine with larger cylinders will be able to combust more fuel per rotation than a smaller engine. Another method is to pre-presurize the fuel/air mixture and cram it into an existing engine size. Thus even though the cylinder size stays the same, more fuel is combusted per rotation. This second method is referred to as forced induction.
Honda chose to explore another method: keep the engine size the same, but turn the engine faster to consume more fuel. Here is an analogy: You want to move foam peanuts from one bucket to another with a cup. You can increase the size of your cup, compress/cram as much peanuts as possible into the cup each time, or you can just move the cup faster. All three methods moves more peanuts. Honda uses the last method. And again, more fuel combusted equals more power generated by the engine.
As the engine speed is increased, more air/fuel mixture needs to be "inhaled" and "exhaled" by the engine. Thus to sustain high engine speeds, the intake and exhaust valves needs to open nice and wide. Otherwise you have what is akin to athsma: can't get enough air/fuel due to restrictions.
If high speed operation is all we have to worry about, Honda wouldn't need to implement VTEC. Indeed, race engines that operate mostly at high rpms do not utilize any mechanism like VTEC. But street cars used for daily driving spend most of their time with the engine at low RPMs. Valves that open wide for high RPM operation contributes to rough operation and poor fuel economy at low RPMs. These undesirable traits are directly against Honda's design goals.
The solution that Honda came up with is the VTEC mechanism: open the valves nice and wide at high RPMs, but open them not as much at low RPMs. So now you have a engine with smooth operation at low RPMs, and high power output at high RPMs.
And that is basically what VTEC is. It's nothing magical. The idea has been around for a long time. Honda's VTEC is just a very simple, elegant and efficient implementation that is extremely effective at achiving its design goal. Honda automobiles are the first among modern automobiles to utilize this mechanism in such a large scale of distribution.
If you want much much more information on the vtec engine and how it works, visit this link (where i got this information from)
http://www.leecao.com/honda/vtec/index.html
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Yeah, Honda made it mainstream. It was a pretty revolutionary idea at first, but now other manufacturers have either copied it closely or even improved it (like BMW). But Honda is the most famous for it cuz it was marketed so well, kinda how BMW owners are so proud of their inline 6 engines. Basically, it used to be something to brag about, but now there's no reason to any more. Well, their engines still produce really impressive horsepower numbers for the size of the engine, but you only have a very narrow band of the engine to play with. Otherwise, it acts like an economy car with not much performance.
Rukus, if they have such a flat power band, then why must vtec type of engines be driven above 4000 rpm to have any useful power?? Given, they do rev to 8500 rpm (ie S2000, which is quite a cool car), but they do not have a flat torque curve. Honda's Vtec is just an on-off type of system, it turns on after a certain RPM. It's not like other manufacturers, where it changes depending on many different factors. If a vtec engine had such a flat torque curve, then why does my 167hp bmw out run a lighter 160 horsepower civic si?
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I just bought a new Dodge truck, love it when people ask,"That thing got a Hemi?" My standard repl? "You're about to find out". I never get tired of it, but then I'm pretty easily amused.
Hemi is short for hemispherical, as in hemispherical combustion chamber. The piston tops are traditionally arched to as well. The theory was that the shape of the combustion chamber provided beter fuel/air mixture and therefore more power. The arched piston head provided higher compression. Hemi's ruled the races for a while, then the Ford flat heads were all the rage.
Today, its' mostly just a marketing thing. I expect Ford will bring back the Flathead along with the Cobra and GT40.
Hemi is short for hemispherical, as in hemispherical combustion chamber. The piston tops are traditionally arched to as well. The theory was that the shape of the combustion chamber provided beter fuel/air mixture and therefore more power. The arched piston head provided higher compression. Hemi's ruled the races for a while, then the Ford flat heads were all the rage.
Today, its' mostly just a marketing thing. I expect Ford will bring back the Flathead along with the Cobra and GT40.
Getting back to the V-Tech,
I am a Valet in the denver area and ironicly enough one night I had two acura integras one with and one without vtech. I realy didnt notice any difference. I then got into my car and down the same strech of road my Bimmer was at 45 mph rather that the integra's 40.
My personal opinion is that if you want power dont buy a compromise motor!!! Like the great attage says; THERES NO REPLACEMENT FOR DISPLACEMENT!!!![bmwkick]
I am a Valet in the denver area and ironicly enough one night I had two acura integras one with and one without vtech. I realy didnt notice any difference. I then got into my car and down the same strech of road my Bimmer was at 45 mph rather that the integra's 40.
My personal opinion is that if you want power dont buy a compromise motor!!! Like the great attage says; THERES NO REPLACEMENT FOR DISPLACEMENT!!!![bmwkick]
epj3, i REALLY REALLY need to stress that you READ that article, and also do some research on Torque Vs. Horsepower, before you pull apart the fact that vtec's have a flat torque curve.
yes they DO have a flat torque curve, but inorder to obtain this FLAT torque curve, its also a very LOW flat torque curve. follow me? So thats why it has no bottom end "power". and thats why it has alot more "power" in higher RPM's.
here's an article to help you understand, quite lengthy as well, but also worth the READ.
http://www.yawpower.com/tqvshp.html
yes they DO have a flat torque curve, but inorder to obtain this FLAT torque curve, its also a very LOW flat torque curve. follow me? So thats why it has no bottom end "power". and thats why it has alot more "power" in higher RPM's.
here's an article to help you understand, quite lengthy as well, but also worth the READ.
http://www.yawpower.com/tqvshp.html
I'm not saying the vtec is gods gift to engines, i was jsut explaining what it is, and how it works. Its a very good engine for a civic because it gives you the power(or torque) you need in lower RPM's and the power(or torque) you need in higher RPM's for passing and the such. (although torque isn't that important (read this article before you flame me))
http://www.yawpower.com/tqvshp.html
epj3, one last thought, if you had to draw the torque curve vs horsepower on a dyno graph, what would it look like?
like this?
No torque on the bottom end, and lots of torque around 4000 rpm's? (Yes i know, the graph is VERY exaggerated)
http://www.yawpower.com/tqvshp.html
epj3, one last thought, if you had to draw the torque curve vs horsepower on a dyno graph, what would it look like?
like this?
No torque on the bottom end, and lots of torque around 4000 rpm's? (Yes i know, the graph is VERY exaggerated)
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Lets talk about some real torque...