Big Ped

I see many of you talking about their VTEC kicking in or using VTEC a lot. I want to get a clear understanding of what VTEC is, what it does to the car and how it is used. Thanks.

AzNTL

well VTEC is a presure that is built up during ur acceleration and is release when ur rmp goes up to like 4500 around that area and that is when you use ur full 225 hp. w/o VTEC your car is not using its full 225 hp.

AzNTL

what VTEC controller does is that it allows you to control the VTEC when it kicks in but by lowering it the presure that builds up is not as much as the stock setting therefore you would not go ur full potential unless you get an intake or something along that line

Big Ped

How do I know when VTEC has kicked in. Will I feel a difference. and to use VTEC, should I shift down to the lower gears. Will I consume significantly more gas if I'm constantly on the 4500 rpm range. Thanks for your help.

Big Ped

by the way I have a TL Type S. Is the VTEC in the Type S any different?

3.2 TL

Well if you want to feel vtec, just floor it

AzNTL

the type S VTEC should b the same. you know that the VTEC is on when your engine sounds like you have an exhaust but not so loud. its feels very nice. if you want it to work go around 80 downshift to 3 on Sports mode and floor it

Gomez

Not to be a yutz, but the description of VTEC operation above is misleading.

VTEC is variable camshaft profiling. What it does is rather like having two engine programs on call for use depending on use. At low engine RPM the camshaft operates for good low end grunt, smooth operation and MPG. At high RPM when the VTEC engages (5100 RPM?), the camshaft switches to a higher-performance mode allowing for better HP at speed.

Here's where the great debate comes in: if it only changes at 5100 RPM, then does your car operate in low-performance mode at low RPM? No, you have the best of both worlds. Torque (good for acceleration at low speeds, more or less) comes at the penalty of HP loss. So, you have a setting optimized for low RPM, and a different one for high RPM. This avoids the issue of no power at low speed, like on a superbike or turbo car that only really runs fast when you ream it.

Of course, it's not entirely that simple but this is the general concept...

You'll know when it "kicks in" by the sound of the engine. Your car broken in with over 1000 miles? Just floor it and listen to the change in the engine as it moves past 5000 RPM and you'll understand. However, your Type-S also has variable intake plumbing, but that's another story.

camshafts effect the opening and closing of intake and exhaust valves in the engine, while intake plumbing effects the air before it has gas mixed in.

consider a tuba: it's built with different plumbing than a trumpet 'cause they use air differently. your VTEC and vario intake plumbing both work to make your TL be a tuba when you're accelerating off the line, and turn it into a trumpet when you're really trying to hit those high notes. get it?

SSMAN66

"Here's where the great debate comes in: if it only changes at 5100 RPM, then does your car operate in low-performance mode at low RPM? No, you have the best of both worlds. Torque (good for acceleration at low speeds, more or less) comes at the penalty of HP loss. So, you have a setting optimized for low RPM, and a different one for high RPM. This avoids the issue of no power at low speed, like on a superbike or turbo car that only really runs fast when you ream it." Gomez


Increased torque does not mean decreased horsepower. The reason a turbo car experiences "lag" is because of the nature of turbocharging. A turbo is an induction air pump that is driven by exhaust gas. At lower RPM's, the turbine is spinning slow, so not much air is being moved. As RPM increases, so does turbine speed. That's when the engine goes negative intake manifold pressure to positive (boost).

The primary reason for VTEC was to enhance top end performance without adverse effects on fuel economy or emissions. VTEC is the primary reason why Acura has so many ULEV (ultra low emissions vehicle) and SULEV (super ultra low emissions vehicle) cars in their line up.

VTEC, or variable timing engine control, is 2 different camshaft profiles. Rocker arms ride on camshaft lobes to open and close intake and exhaust valves. There are 2 sets of rocker arms, and 2 camshaft profiles, standard and VTEC. The engine utilizes oil pressure to lock the 2 rocker arm sets together at high rpm, and only the VTEC camshaft profile is utilized at this time.

There is an oil pressure switch and a VTEC solenoid located above the oil filter. The oil filter switch will not allow power to the solenoid unless there is adequate oil pressure to lock the rocker arms. The solenoid sends a signal to the ECU, or electronic control unit, when there is adequate oil pressure. The ECU sends power to the VTEC solenoid at a predetermined RPM. The solenoid retracts and allows oil into the VTEC passages which flow to the valvetrain.

The VTEC camshaft profile has increased valve lift, duration, and overlap. It's a more aggressive profile that increases both torque and horsepower.

If you put your car in 2nd gear and hold it at half throttle, you will hear VTEC come to life shortly after 5000 rpm. It will sound like angry tigers in heat trying to break out of your engine compartment

Bitium

I very much agree with SSMAN66.

doopstr

I can't really feel when V-Tec kicks in on the TL. It's not like the cars jumps with power when it engages. You can sure here it though. I love the way the engine sounds when VTEC kicks in.

bioyuki

SSMAN66--
why did you delete your posts on the CL board?

Mike

Yeah, that's a bummer as the posts were very informative.

Gomez

SSMAN, I hear you but still don't completely agree. You're right about the turbo thing, but remember that I offered my explaination as a conceptual one and that it's not really that simple.

As for torque vs. HP, well, I stick to my guns that you can increase one at the expense of the other. I won't go into physics lessons here, but consider two points from "the experts" on my behalf:

1) Acura - they say in their literature that they engineered VTEC to increase top end power (HP) without sacrificing torque or drivability around town at low speeds. That's because the car essentially has two different engine personalities. Consider a 70s era musclecar: in fact, the term "hotrod" came from high-performance camshafts that increased HP and top end power at the expense of low end torque and mild manners at idle. If you've ever listened to a funny car dragster at idle you know how poorly the engine operates at low speed, and such is one reason why "stall converters" are used for drag racing with auto transmission cars.

2) BMW & Car and Driver - when the X5 was about to be released for production with the V8 from the 540/740, BMW and the car magazines said that the engine would be used but re-tuned to provide greater torque with a slight loss in HP. Do you think they would have done this if there was a better way to increase torque and not lose HP? Sure, there are ways, but not cheap ones.

Sure, you can increase both at the same time with engine mods (SC, TC, NOS, I/H/E, etc.), but given one certain setup if you play with valve timing you can only increase both to a point, after which increases of one will decrease the other.

Or in other words, "you can't get something for nothing" and the First Law of Thermodynamics is is true today as when it was conceived. It's a sliding scale, and for an engine of given "strength" work = force * distance. HP is more or less "work" in this equation, and torque is "force" so you see that one depends on another.

I'm sorry this is so long-winded, and I'm sure a physics expert cound explain it more succinctly and accurately. Bye.

Gomez

To answer your question, BigPed, VTEC is a magical little man who hangs out under the hood to make your car go "vroom" when you're hauling ass.

Two primers:
http://www.aj.com/main/metaAnswer.as...sus+Horsepower

http://www.howstuffworks.com/question229.htm

MahaRaja

Interesting! I never knew all about the VTEC, but now I do. Thanks!

SSMAN66

Bioyuki & Mike - I left the CL board because a few members made it more trouble than it was worth to post over there. I had hopes of learning from member experience with the CL, and helping them out with the results of my own trial and error. One CL member (Rwwlaw) has gone so far as to continually send me nasty emails stating that I must be "xephyr", who he has obviously had some poor business dealings with. His accusations are based on some witch hunt suspicion, and are entirely incorrect. I've emailed moderators, but there has been no reply. I'll come back to the board when the moderators are willing to deal with these acts of infantile acts.

I have met a few very good people from the CL forum, and we communicate by email or through the TL board.

Gomez - Trust me on my VTEC experience.....I work for Honda Motor Company As for my experience with torque/horsepower, I have been building competition engines for 12 years. In 1994-1997 I campaigned a 1990 Mustang GT that ran 9.20 @ 152 mph on 10.5" tires. My current toy is a 1964 Pontiac GTO powered by a 1100 horsepower Pontiac engine that displaces 480 cubic inches. This engine peaked just over 1100 hp at 6700 rpm, and the peak torque was 1085 lbs ft at 4600 rpm. From 2000 to 6000 rpm, the torque never falls below 900 lbs ft.

Where is the sacrifice of 1 for the other?

Gomez

Sounds brutal, can I drive it? My point is that simple tuning, not MAD MODS(!), can improve torque while lessening HP and the converse. Of course you can increase both at the same time.

Honda street cars sacrifice ultimate power for economy, streetability and emissions and therefore benefit from VTEC. Maybe someone should dyno a TL with VTEC engaged from idle to redline, and again with it disengaged from idle to redline. Then we could put this to bed.

Seriously, though, then why does the BMW 4.0 V8 show with less HP when torque is increased? Torque = twist, while HP = work. Work is just a mathematical expression, and something with a given ammount of power could either twist really hard or not as hard but faster. That's equal power with different results.

Big Ped

SSMAN and Gomez, you guys really know your stuff. Wow, I must now go back to my physics testbooks that I studied 6 years ago when I was an Engineering major (that only lasted two years, couldn't take the math and physics so I settled for an MIS degree in the field of Business). F that, I'm smart too.... Lets open up a financial services industry or back office operations forum and you'll see who the man is.

I got more information that I expected. Sh*t, you guys are crazy.

Hey, I would love to always use VTEC. I love the way the engine sounds and love the power. However, would that compromise fuel consumption? And if so how much fuel? If it isn't significat, I could afford and extra galon or so per tank. Thanks.

UTChE96

http://www.howstuffworks.com/question229.htm

SSMAN66

Gomez - I wish I could drive it The engine is sitting on a stand, and I'm still waiting to get the car back from the chassis shop. I'm anticipating low 8 second ET's at over 165mph

My point is that if you increase one, there will be some increase in the other. I agree that you can tune specifically for optimum torque, or optimum horsepower. When tuning like this, you will experience a small sacrifice in the other peak #. However, torque and horsepower are equal at 5250 rpm in a naturally aspirated engine. For that reason, if you increase torque across the entire operating range, you will increase hp as well.

Gomez

Otay, looks like we're in agreement. I'm not too mechanically inclined so I perhaps worded my explainations poorly.

As for your monster, even if you can't drive it you can run it on the stand and feel the rumble! I'm jealous!!!

Big Ped

That's great guys and thanks for your help.