This thread is for those who are new to the world of Honda & the VTEC. Let's try to keep the threads Prelude oriented (as Preludes are some of the finest Honda cars made So first off, here is what VTEC means and how it works:


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.




Modified by philjuba at 1:34 PM 8/3/2004

 

i like it...

 

Know your Prelude. What Generation is it> 1st gen, 2nd gen, etc. Go to http://hondaprelude.sitemynet.com/hs.html for a very good history of the Honda Prelude. Get to know your car Here's a link for the specs on a 5th gen (in my humble opinion, the best gen of all... I have a 98): http://www.cg-car-reviews.com/...5.pdf


Modified by philjuba at 1:31 PM 8/3/2004

 

was very educating, but how and when do i know when the VTEC is kicking in?

I have heard only at high speeds but roughlt at what rev count on a 94 2.2 vtec prelude?

 

5200 rpms or so is when you hit vtec and all the way to cutoff, as FAR AS my ear is concerned.

You can check the stickies and see on that.

You'll feel that engine pulling more as it hits vtec. If you are not, do a search on oil pressure and check on the oil pressure and oil measurement.

 

good post. informative. we need more informative posts from the enlightened h-t members if they have the time

good analogy as well

 

what you mean to tell me that my engine's VTEC badge does not give me mystical powers of some sort. I'd swear by it !! at least one guy seems to think so id meet a couple weeks ago. long story short he owns a Grand Prix GTP (you know the supercharged ones). we have a mutual friend that doesnt know diddly about cars and was boasting about my car being fast (93 vtec lude) and this guy told my friend he would kill me. The news got back to me and i said his car is a fat overwieght pig and i doubt he would kill me. apparently this started some sort of huge debate between a group of about 20 people ???? crazy i know ... anyways, i turned down the race and was made fun of so i got pissed off and raced the damn GTP 3 times. outcome 3 wins prelude no wins GTP (ahahaha). out of the blue when we where standing around talking about it (him making excuses). someoned said "HEY, THERES A VTEC IN THERE" i was like .... uh, duh... theres a damn sticker on the back of the car that says it !! all of a sudden the GTP guy freaks out and starts claiming if he knew i had a VTEC he would of never raced me !!! I was like, dood ... you have 2 more cyclinders than me and a freaking supercharger !!! He then went on to claim that VTEC's are cheating and he knows for a fact that a VTEC'ed car can kill camaro SS and cobra mustangs !!! I laughed for a bit when he said this and decided to let him go on beliveing this !!! So, i told he yeah its true it wasnt a fair race. You might as well go race tercel or something they dont have VTEC. actually that story turned out to be long but my point was there are alot of people out there that think VTEC is a magical device that turns ones car into a JGTC race car. I didnt have the heart to tell him that they come in civics too .... also worth mentioning that no one else standing around seemed to dissagree with the guy. maybe they should read this thread... good info

 

vtec for beginners is called SEARCH!

 

good info philjuba, but VTEC was actually an inginuitive invention designed to make the car responsive and powerful in the low rpms and yet still powerfull in the high rpms.

The camshaft engine in general had the limitation of being cam'd for high rev power or low rev power, VTEC solved that issue, And now the new forms of vtec like e-VTEC etc have been patented by honda and offer various benefits, like fuel economy, responsivenes and efficiency (hp/liltre compared to all other manufacturers, honda comes top on allmotor engines)

 

Great post!
This gets a from me.
Hopefully this will be a good reference point for anyone wanting to learn more about VTEC and Honda's in general.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by flashmang &raquo;</TD></TR><TR><TD CLASS="quote">what you mean to tell me that my engine's VTEC badge does not give me mystical powers of some sort. I'd swear by it !! at least one guy seems to think so id meet a couple weeks ago. long story short he owns a Grand Prix GTP (you know the supercharged ones). we have a mutual friend that doesnt know diddly about cars and was boasting about my car being fast (93 vtec lude) and this guy told my friend he would kill me. The news got back to me and i said his car is a fat overwieght pig and i doubt he would kill me. apparently this started some sort of huge debate between a group of about 20 people ???? crazy i know ... anyways, i turned down the race and was made fun of so i got pissed off and raced the damn GTP 3 times. outcome 3 wins prelude no wins GTP (ahahaha). out of the blue when we where standing around talking about it (him making excuses). someoned said "HEY, THERES A VTEC IN THERE" i was like .... uh, duh... theres a damn sticker on the back of the car that says it !! all of a sudden the GTP guy freaks out and starts claiming if he knew i had a VTEC he would of never raced me !!! I was like, dood ... you have 2 more cyclinders than me and a freaking supercharger !!! He then went on to claim that VTEC's are cheating and he knows for a fact that a VTEC'ed car can kill camaro SS and cobra mustangs !!! I laughed for a bit when he said this and decided to let him go on beliveing this !!! So, i told he yeah its true it wasnt a fair race. You might as well go race tercel or something they dont have VTEC. actually that story turned out to be long but my point was there are alot of people out there that think VTEC is a magical device that turns ones car into a JGTC race car. I didnt have the heart to tell him that they come in civics too .... also worth mentioning that no one else standing around seemed to dissagree with the guy. maybe they should read this thread... good info</TD></TR></TABLE>

HAHAHAHA....thas hilarious.....I'd love to hear the long version.


Modified by Slipknt777 at 1:53 PM 8/4/2004

 

lol !!! flashmang, all of your posts are funny