Honda D Series Forum banner

Status
Not open for further replies.
1 - 20 of 39 Posts

·
Registered
Joined
·
3,804 Posts
Approximately 4300
 

·
Registered
Joined
·
3,804 Posts
Yep! I got it off 7thgencivic.com....so I'm assuming it's pretty accurate! :)
 
C

·
Guest
Joined
·
0 Posts
Discussion Starter #6
Jspek_Inspired said:
wrong vtec kicks in anywhere from 2500-3200rpm.. You may wanna check 7thgen again. Cause they finally found out it does kick in from 25xx-32xx.
doubting mel's word ?????you shall die fo this!!jk.damn,don't ya think its a lil ridiculous for vtec to kick that early?I don't know why,but i've heard that early detanation <---[i can't spell lol] harms something in a motor.
 

·
Registered
Joined
·
3,804 Posts
Jspek_Inspired said:
wrong vtec kicks in anywhere from 2500-3200rpm.. You may wanna check 7thgen again. Cause they finally found out it does kick in from 25xx-32xx.
I'm not saying your wrong...but that does seem a little early for vtec to kick in! Where are you getting your info? Post up a site if you got it!
 

·
Registered
Joined
·
3,804 Posts

·
Registered
Joined
·
4,363 Posts
If you look at the torque curve in this dyno of the d17, it looks like it starts to dip from 3000-4000 rpm.... then it goes back up. Well, this could be just tuning (but I doubt honda wouldn't even it out)... if it's not tuning, it's the vtec transition because you can see it start to increase again after 4000 rpm. I dunno just a guess... i've never even driven one of these :)
 
B

·
Guest
Joined
·
0 Posts
mrnicolas said:
it is i-vtec so that may be correct. vtec is actually an emissions system.
it is not an emissions system. vtec on the the sohc's opens up the intake valves more letting in more air/fuel which results in more power. and anything that lets in more air/fuel is not an emissions control system. and yes the i-vtec engages earlier than our d17's. I agree with the approx. 4300. cause I can hear and feel it around 4500. it is before 5k for sure. :cockbloc:
 

·
Registered
Joined
·
3,804 Posts
bradmanuwf said:
you're an idiot. it is not an emissions system. vtec on the the sohc's opens up the intake valves more letting in more air/fuel which results in more power. and anything that lets in more air/fuel is not an emissions control system. and yes the i-vtec engages earlier than our d17's. I agree with the approx. 4300. cause I can hear and feel it around 4500. it is before 5k for sure. and again, you're an idiot. :cockbloc:
Everyone's here to help...so if somethings wrong or misstated then correct it! Don't go around insulting other members...if you want to do that then go to HT...cuz that kind of attitude is not welcome here!

Good info btw!
 

·
CR-Vtakin
Joined
·
11,459 Posts
Here is vtec explained.

http://auto.howstuffworks.com/question229.htm
or
http://auto.howstuffworks.com/framed.htm?parent=question229.htm&url=http://www.leecao.com/honda/vtec/whatsvtec.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.



http://auto.howstuffworks.com/framed.htm?parent=question229.htm&url=http://www.leecao.com/honda/vtec/index.html

After the sucess of DOHC VTEC engines, Honda became increasingly confident with the use of VTEC technology. It has proven to be a reliable and economical alternative to increasing displacement or using forced induction. Honda decided to apply VTEC technology to a larger segment of the market with the introduction of the SOHC VTEC system. Like its DOHC counterpart, SOHC VTEC optimizes the flow of fuel/air mixture for high RPM operation while maintaining smooth and economical low RPM operation. But due to its simpler design and humbler performance intentions, its specific output is not as high DOHC VTEC engines.

In a SOHC engine, there is a single camshaft per bank of cylinders. So both the exhaust and intake cam lobes are on the same camshaft. The figure to the right illustrates this design. The three cam lobes in the middle are the intake cam lobes. The two low RPM lobes actuate two valve rockers, which in turn pushes the intake valves open. The high RPM lobe actuates a follower, which is shaped like a valve rocker, but doesn't actuate any valves. While there are different intake cam lobes for high and low RPM operation, the same two exhaust cam lobes are used for all RPMs. The lack of cam profile changing for exhaust valves is the primary difference between DOHC VTEC and SOHC VTEC engines. Since the exhaust valves in a SOHC VTEC engine behaves just like a non VTEC engine, only the intake valves will be discussed below.

During low RPM operations, the two outer intake cam lobes directly actuates the two valve rockers. These low PRM intake lobes are optimized for smooth operation and low fuel consumption. The high RPM intake lobe actuates the follower. But since the follower isn't connected to anything, it doesn't cause anything to happen. This procss is illustrated by the figure to the right.

At high RPMs, oil pressure pushes a metal pin through the valve rockers and the follower, effectively binding the three pieces into one. And since the high RPM lobe pushes out further than the low RPM lobes, the two valve rockers now follow the the profile of the high RPM lobe. The high RPM lobe's profile is designed to open the valves open wider, and for a longer duration of time, thus allowing more fuel/air mixture to enter the cylinder. The improved breathing allows the engine to sustain its torque output as RPM rises, thus resulting in higher power output

The SOHC VTEC is a system that achieves mild power gains. Usually, SOHC VTEC engines gives about as much power as DOHC non-VTEC engines of similar displacement. Whether or not the added complexity of the VTEC mechanism off-sets the simplicity of SOHC (versus DOHC) is up for debate. SOHC VTEC is currently found on the Civic EX, Accord LX/EX/V6, Odyssey LX/EX, Acura TL, CL, and CL Type-S.
 
B

·
Guest
Joined
·
0 Posts
EJ1 Freak said:
Everyone's here to help...so if somethings wrong or misstated then correct it! Don't go around insulting other members...if you want to do that then go to HT...cuz that kind of attitude is not welcome here!

Good info btw!
I don't know how to participate on web boards!

Give me bad rep
 

·
Administrator
Joined
·
16,376 Posts
I don't think its a good idea to be insulting members that have been here for a lot longer than you. And if he was wrong then i am sure he could live with that. And that attitude sin't going to get you very far here. Go to honda tech. People like you are why i wouldn't even post there.
 

·
CR-Vtakin
Joined
·
11,459 Posts
I deserved to be flamed? haha, you are ignorant. Go back and look up more about vtec. I think you will learn more about it if you dig deeper. You probably will not do it though.
 
B

·
Guest
Joined
·
0 Posts
Discussion Starter #18
mrnicolas said:
I deserved to be flamed? haha, you are ignorant. Go back and look up more about vtec. I think you will learn more about it if you dig deeper. You probably will not do it though.
HAHAHAHAH your ignorant.
Next you'll be telling us that Catalytic convertors give you horsepower....
VTEC is an emissions control system....hahahahaha.....
VTEC is a gas saver......it gives you the gas mileage of the economy car a civic is, with the "power" you need every once in a while to get through traffic.
 

·
Registered
Joined
·
3,804 Posts
bradmanuwf said:
he deserved to be flamed, c'mon. a civic owner posting in a forum about vtec and doesn't even know what it is..... I have a question for you though. is that your car in your avatar? if so, its ugly & slow and what are you doing in the 7thgen section?.....j/k
Ok first of all...no one deserves to be flamed...esp if they're trying to help! Last time I checked forums are all about learning...so if someone says something incorrect..then correct them...but don't be an ass about it! The reason I'm in the 7th gen section is to try and HELP out other members!

Yes that's my car in my avitar...and I could care less what you think of it...regardless of whether you're joking or not!
 
B

·
Guest
Joined
·
0 Posts
. you need to go and learn more about vtec. its not an emission system. its valve train management you retard. a smog pump is an emissions system. the Cat. is an emission system. emissions is the amount of hydrocarbon content in the exhaust. it has nothing to do with vtec. vtec just opens the valves more you ignorant bastard.
 
1 - 20 of 39 Posts
Status
Not open for further replies.
Top