Gomez

Most people mistakenly say that VTEC "kicks in" at high RPM. In fact, VTEC merely has two different cam profiles: one that works at low revs for better throttle response and MPG at low RPM, and the other to improve power at higher RPM. It's the best of both worlds, really, and it's always doing it's job.

When they talk about VTEC "kicking in" they are referring to when the engine switches to high-performance mode, more or less.

You ever sit next to an old muscle car that's all hot-rodded out at a traffic light and notice that it idles all rough? That's B/C the engine is tuned to operate best while running hard, and not when idling. Well, VTEC is tuned to run well at low RPM and also well at high RPM, kinda like being an econo car while cruising and a sports car while gunning it.

In fact, that's where the term "hot rod" began: from those muscle cars that had high-performance camshafts installed to run better when being driven hard. VTEC gives the best of both worlds, and is always "engaged" no matter what anyone says otherwise.

The onle better solution is continously-variable camshaft mapping, which is more or less like having an infinite number of possible valving permutations. I believe that the nicer Lexuses and BMWs use this now?

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'01 White Diamond Pearl 3.2TL
-Wing, tint, burlwood shift, Whistler 6-band
'88 White RX-7 Convertible (SOLD)
-Permanent tinitus courtesy of Rockford-Fosgate

Guest

Thanks.

AC

I still think we have a half-A$$ VTEC.

Eskimo

I pretty sure our TLs have a 3 stage VTEC (low, medium, high speed). Can anyone confirm? In any case it is still is one of the few system that can vary the duration of the cam lift. BMW's Double Vanos and Toyota's VVTi use phase shifting to move the cam shaft but they do not have a second or third cam profile like Honda's VTEC. From a manufacturing cost perspective VTEC cost more to make due to complexity.

Wonder how many more hp can be squeezed out if Honda adds VTEC to the exhaust values as well?

LegendC

VTEC already effects the exhaust valves and there is no such thing as a three stage VTEC, that would require Three lobes per valve. Vtec is still superior to the other offerings out there becuase it changes both lift and duration. The latest revision of VTEC in the RSX and S2K (I think) is VTEC-i. This allows the engineers to change advance/retard timing along with the lift and duration. This is how they are extracting more and more power out of typicaly "puny" engines.

Eskimo

LegendC, check out the Japanese Honda Inspire web site you'll see a picture of a 3piece rocker arm. (http://www.honda.co.jp/INSPIRE/factbook/engine.html) One for each set of cams. But I don't know if the 3.2 engine has this or not since in Japan they also offer a 2.5 for Inspire/TL and I can't read Japanese.

I also heard that Honda will completely revamp their whole engine line by 2005 to i-VTEC or was it VTECi. Think this will use a combination of cam phasing (like VVTi) and cam changing (VTEC). Toyota's new VVTL-i already uses this.

Cars are just like computers. Technology changes so fast!

RAdams

In reply to several of you (I forget how to quote!):

VTEC does, in fact, "kick in". When below the VTEC threshhold, the center (VTEC) cam lobe's movement is "absorbed" by the LMA (lost motion assembly). It's basically a little spring-loaded assembly that mimics the valve spring's role before the VTEC rocker is engaged.

I also felt more of a difference when the IAB on my GS-R opened, versus the VTEC transition. The sound was also much more pronounced.

3-stage VTEC does exist and it doesn't mean that it has 3 cam lobes for each valve. It's a standard VTEC camshaft (this is a SOHC VTEC application where the intake valves are the only ones that VTEC acts upon). The magic of 3-stage VTEC lies in the rockers themselves (the cams are like any other SOHC VTEC cam). During the first stage, only one intake valve opens (the secondary and VTEC lobes' movement are again "absorbed" by the LMA's). This single intake valve opening provides a great amount of swirl, leading to very efficient combustion and low emissions. During the second stage, the secondary rocker comes back into play and it operates like any other VTEC motor in non-VTEC mode. (As an aside, all VTEC cams I've seen have a little less lift on the secondary non-VTEC lobe and therefore opens the second intake valve just a little less than the first, producing a mild swirl effect for the same reasons as stated above). The third stage would be when all the rockers are locked together and follow the larger VTEC lobe.

As for variable valve timing: it's true that this system adjusts constantly dependant on engine load, etc. but the range in which it operates is much smaller than VTEC. Think of VTEC as an on/off switch and VVTi (and Variocam, and VANOS, et al) as dimmer switches, although they never get quite as "bright" as VTEC. Toyota recently introduced VVTL-i which is basically a VTEC-like cam with a multi-piece computer-controlled cam sprocket. Honda has countered with i-VTEC... similar concept. The two systems working together theoretically allow great power at all parts of the rev range.

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2000 WDP 3.2TL non-NAV

<FONT COLOR="#800080" SIZE="1" FACE="Verdana, Arial">[This message has been edited by RAdams on February 12, 2001 @ ]</font>

Eskimo

Thanks for the detailed explanation RAdams. I am glad to hear we have the better 3-stage VTEC.

Gomez

Whew, I knew my starting of this thread would create controversy!

I guess I was being a little too specific for some when I said that VTEC does not "kick in" in that y'all are arguing what I already said: VTEC kicks the high-performance cam in at high revs. We all know that...

However, VTEC more correctly is a system that is always there, whether or not it is in haull-butt mode at any given time.

By saying it "kicks in" one implies that at low revs it was not doing anything, when in fact the converse is true: at low revs we get greater torque and power than a normally tuned and valved engine of similar size would enjoy.

Those that say it only "kicks in" at high revs make a false argument akin to saying that your transmission only kicks in when it shifts to second or higher gear, and that in first gear the tranny is useless. Obviously, the idea of the tranny is to best use the torque at any given combo of vehicle speed and engine RPM, and that essentially is what VTEC does for engine output.

I'm personally glad that I have VTEC, as it allows not only for me to get off the line quickly at low revs, but also to pull hard at high revs. You guys act like it's an embarrasment to the engine that VTEC only swithes to the 'hot' profile at high revs, and y'all are missing the whole point! If y'all still don't believe me, then get a ten-speed bike and put it into the highest gear and try to drag race me while I just use the "lowly first gear"!

Come to think of it, that's the same principle behind overdrive pulleys that all y'all gear heads seem to want!!! :P

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'01 White Diamond Pearl 3.2TL
-Wing, tint, burlwood shift, Whistler 6-band
'88 White RX-7 Convertible (SOLD)
-Permanent tinitus courtesy of Rockford-Fosgate

LegendC

RAdams- Thanks for correcting me about the three stage system. The first two stages are what were found in the Vtec-E (E for Economy) found in the Civic. Basically running the car in 8 valve mode until the VTEC crossover to 16. I was not aware that the newer Hondas incorporated this into the design. Technology is great. The next big thing could be the Variable Compression engines that Saab is designing. The whole head is able to tilt, thus changing the volume in the cylindar, thus the compression. Very nice with thier turbo applications.

Guest

Exactly. VTEC does not kick in, but the accompany of various audible elements and the range of the engines revolutions which accompany a sudden exponential increase in power together form the myth that VTEC kicks in when switching to its hotter camshaft. (How's that for a run on sentence)

VTEC is not Gods message to the car industry, it is a clever idea to improve low end performance and fuel economy, while adding an extra "ummph" to the high end.

VTEC is just a placebo, a marketing gimmick which has helped Honda recieve the high level of recognition it has over the last 10 years. If Honda claims VTEC kicks, whos to doubt them, and thats exactly my point.

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Guest

Two comments:

Nazi: nice to see you sig back !!!

Doesn't the VTEC affect the INTAKE valves, not the exhaust? I think the reason for this is that the car has an easier time exhaling (because the exhaust fumes are HOT) than inhaling. So inhaling is where it needs the help?

Good discussion!



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2000 3.2 TL, Paper maps.
Comptech axle-back exhaust--REMOVED AND FOR SALE $400 (e-mail me)
225/55ZR-16 RE730s on OEM alloys.
205/55QR-16 Alpins on steel wheels w/covers (winter).

Pictures

1999 CR-V EX 4WD Auto White
NEW! 1992 MR-2 5-Speed T-Tops 2.2L, Greddy SP S/S Exhaust

Eskimo

VTEC works only on the intake valves. BMW's Double Vanos on the other hand works on both intake and exhaust.

I found this super site on all kinds of techno gizmos. I think you guys will enjoy it:

http://www.fortunecity.com/silversto...tech_index.htm

LegendC

I could have sworn the DOHC VTEC on the NSX, Civic SI and the likes had it on the exhaust, could be wrong though.

Eskimo

LegendC, I only know the VTEC on the North American Accord, TL have VTEC on the intake only. VTEC could be function on both intake and exhaust on other Hondas but I don't know.

Eskimo

Evolution of VTEC. This came out in November 3, 2000:

TOKYO - Honda Motor Co has introduced an all-new DOHC i-VTEC - or Intelligent VTEC - engine that combines optimum fuel economy, cleaner emissions and higher performance.

The new compact, lightweight, high-performance 2.0-litre engine is part of Honda's new generation i-Series line-up, and makes its debut in the new Honda Stream in Japan.

The new DOHC i-VTEC engine fuses world-class fuel economy, low emissions with high power and torque at all speeds, thanks to Honda's unique VTEC system that varies valve timing and lift. Variable Time Control (VTC) continuously adjusts the intake valve timing to match engine load.

It also features a variable length intake manifold, a rear exhaust system and a new lean-burn NOx-absorbing catalyser. When combined with the valve technology, these features help the engine deliver 113kW @ 6500 rpm and 7 litres/100km to meet 2010 fuel economy standards. The engine's clean exhaust emissions has earned Low Emission Excellence certification from the Japanese Ministry of Transport.

The engine is 10 per cent lighter and more compact than conventional 2.0-litre engines due to a new engine structure.

Honda will continue development of its i-Series engines, and renew its entire engine line-up by 2005. All domestic Honda vehicles will earn Low Emissions Excellence certification by 2002 and meet 2010 fuel economy standards by 2005.

The i-Series engines will be built using Honda's new manufacturing technology within the Sayama Plant. Honda will manufacture the engines in sequence with vehicle production to reduce the amount of in-process floating stock and production lead times.

Designed for efficiency and flexibility, the new line at Sayama will halve investment for new model introduction and is capable of producing eight different engines. The plant will cover aluminium processing of cylinder blocks, machining and engine assembly.

Honda will invest AUD $631 million in updating its domestic automobile manufacturing system by March 31, 2001. Honda will also complete the AUD $263 million refurbishment of its domestic engine manufacturing system by 2003, bringing it in line with its Green Factory concept. The new production process targets reduced waste, energy use and emissions.

Honda is the largest engine manufacturer in the world, producing 11 million engines annually. Honda also builds products in more than 100 manufacturing plants in 33 countries and employs more than 125,000 associates globally.

AC

There is a 3 stage VTEC, the new RS-X will be equiped with 3 stage.

Gomez

Thx for the article, Eskimo!

My question now is what's next in the evolution of variable this-and-thats in engine engineering? If length of intake runners, valve timing and duration can be controlled to the end of better efficiency and power, then why not adaptive exhaust systems? Perhaps an adaptive catalytic converter, and also variable-length manifolds or headers. I'm sure such a system is already being evaluated in some R&D department as we speak...

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'01 White Diamond Pearl 3.2TL
-Wing, tint, burlwood shift, Whistler 6-band
'88 White RX-7 Convertible (SOLD)
-Permanent tinitus courtesy of Rockford-Fosgate

Gomez

See my earlier follow-up for a possible future direction of VTEC.

Either way, exhaust does in fact benefit from help, too, and the aftermarket has the answer of headers and porting/polishing thus far. As far as the valving and mapping goes, well, maybe it just costs too much right now to justify the potential gains. I can only assume that if uneven-length exhaust manifolds (OEM in 99% of cars) work best in 'normal' operation such as part-throttle and well under redline, and if headers are used conversely to address the more heavy-footed drivers, then some sort of variable approach might be warranted for the future. Maybe a butterfly valve that shunts exhaust through the optimum tubing given the situation, or perhaps variable venturis to hustle the spent gasses along?

Surely there is someone on the board versed in both fluid dynamics and thermodynamics who could offer some insight!

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'01 White Diamond Pearl 3.2TL
-Wing, tint, burlwood shift, Whistler 6-band
'88 White RX-7 Convertible (SOLD)
-Permanent tinitus courtesy of Rockford-Fosgate

<FONT COLOR="#800080" SIZE="1" FACE="Verdana, Arial">[This message has been edited by Gomez on February 12, 2001 @ ]</font>

Gomez

Speaking of porting and polishing, has anyone here tried it on their car's intake and/or exhaust? The concept is simple, although the operation would involve quite a few hours of labor.

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'01 White Diamond Pearl 3.2TL
-Wing, tint, burlwood shift, Whistler 6-band
'88 White RX-7 Convertible (SOLD)
-Permanent tinitus courtesy of Rockford-Fosgate

Eskimo

Gomez, if you are into all this engineering stuff goto the link I posted earlier. It talks about some of the new stuff manufactures are working on. Its the best site I have found on the internet on technical advancements in the auto biz.

Guest

A great debate could be started on whether or not VTEC "kicks-in".

On one hand, a person could argue that two separate cam profiles are designed from the start with VTEC in mind. Therefore, it's simply a means to widen the torque band, and happens to have a crossover point where the two torque-curves of the cams overlap.

On the other hand, another person could argue that the "street" cam profile is similar to most car's only camshaft, and therefore the "hot" cam profile is a racing cam that is engaged at high RPM. This theory is further backed up by the fact that VTEC is "inactive" at lower RPM, then is activated by hydraulic pressure at higher RPM (at the command of an electric soleniod).

VTEC's high-RPM engagement is frequently accompanied by a louder intake note, especially for those who have removed the stock intake resonators. With DOHC VTEC, the louder note is also audible with the exhaust. This makes it seem that something is "kicking it".

I experienced a "kick" with my modded Integra GS-R. Was it just the NASCAR-like noise, or was it a kick of power, too? I think the mod's helped make the VTEC transision more of a spike of power. Perhaps someone has a dyno to confirm that VTEC has more of an effect on a modded system over a stock system.

Then again, the GS-R had dual-stage intake. At a certain RPM, butterfly valves open and let the engine gulp more air (like the Type-S does). This is where I felt the most power gain was, not the VTEC transision.

OK... enough babbling. Anyone else agree with my perspective?

------------------
2000 3.2 TL, Paper maps.
Comptech axle-back exhaust--REMOVED AND FOR SALE $400 (e-mail me)
225/55ZR-16 RE730s on OEM alloys.
205/55QR-16 Alpins on steel wheels w/covers (winter).

Pictures

1999 CR-V EX 4WD Auto White
NEW! 1992 MR-2 5-Speed T-Tops 2.2L, Greddy SP S/S Exhaust

Guest

I'd like to offer up my opinion and a few "facts". In North America there are basically two types of VTEC engines in the Honda/Acura family (let's not count VTEC-E cuz who here cars about saving gas?). Your SOHC VTEC operates only on the intake valves and is two stage only. There are three lobes over each cylinder but the outer two are your "low-lift" lobes and directly actuate the valves. The center lobe is the "high-life" lobe and this is what engages when the computer tells engine oil to lock a pin and force everything to run on the high lift profile. Don't forget this also advances timing as it increases lift and duration. This system is installed on Civic EXs, Accord EXs (4 cylinder), Accord V-6, Odyssey, TLs, CLs, and MDX.

DOHC VTEC operates intake and exhaust and is installed in Civic Sis, S2000s, Preludes,GS-Rs, Type-Rs, and the NSX. The NSX is the only example of DOHC VTEC in a V-6 from Honda.

In some cases a variable intake is used to spread out the available torque (GS-R and new RSX come to mind) In some cases short straight runners are used (Type-R and S2000) and in still others the intake plenum is divided in two for a ram air effect (CL-
S and MDX).

With the introduction of the RSX and i-VTEC Honda will incorporate the continuously variable timing sprocket like the BMW Vanos or Porsche Variocam systems with the DOHC VTEC system that has served so well over the last 10 years (yes 10, the NSX introduced VTEC, variable volume intake, and titanium con rod to the world in '91).

FWIW, in my S2000, the VTEC "kicks in" at 6000. On a dyno plot I saw (not my car), the car is puting our around 150 hp at the wheels at 5500 rpm, by the time you get to 6500, hp has jumped to almost 170, and peaked at about 195 at 8200 rpm. IMO, 20 hp in 1000 rpm give you a nice "kick"

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Aloha,
Colin
Internet Sales Manager,
www.hondahawaii.com
www.satoauto.com (my homepage)

Tann@808

The man has spoken wassup Colin!!

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tann@808-'00 TL
non-Navi(Doesn't work in Hawaii)

Factory body kit & Wing, 19" Racing Hart C-5's,
Nitto 555's, CompTech Springs, CompTech Exhaust,
CompTech Headers, Inspire Taillights, NOS(70 shot),
AEM CAI, Alpine 8080, TL rear door handles in front,
Apexi v-afc, 5% + 30% tints,30% front windshield.
tann@pixi.com

RAdams

Eskimo: Sorry, I guess I wasn't clear. We (TL owners) don't have the 3-stage VTEC. It's used for economy purposes on Civics in Japan.

Colin: GREAT post. Thanks for the input!

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2000 WDP 3.2TL non-NAV

Shoofin

Well, the TL's cam is pretty mild, IMO.. It's not a sports car in any way.. My '66 Mustang has a mild cam( that I installed, it's not factory) for good low end and mid range punch.. If I went with a heavier cam, the idle would be very lumpy and loud, and I would lose low end power, also you would have to have a high stall torque converter(thats what engages your(auto) transmission, the little push you feel when u shift into gear and the tranny is engaged) that must rev to at least 2500-3000 rpm before starting to move..
'Ed

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Acura-TL.com - Forum Moderator

'99 TL Satin Silver/Ebony, Non/Nav, Comptech lowered, Comptech Air Filter Element, Inspire Tails, AEM Brake Pads all around, Comptech Axle Back Exhaust, "Guy Smiley" doll on the dash as my Co-driver...

Pics of my TL
Pics of my Miata! Wadya think?

Guest

Just knockin' this over into a "flaming hot" thread... (25 replies)

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2001 3.2 TL w/Nav
White Diamond Pearl
Alpine 6-Disc CD Changer
Burlwood Shift Knob
Valentine One
15 Year Financing at 22%

Guest

Eskimo,

Thats a good question. I wonder myself if it has something to do with the death of Mr. Honda. He was an engineer and believed that great engineering was marketing. It may be because Rich Thomas (former head of Acura) is a "gearhead", and Dick Culliver (the current head) came from the "Honda side of the family" where perception is very important.

I have a bit of concern that we seem to be moving away from wishbones in the Civic/RSX chassis because their market research showed only a small percentage really cared about the type of suspension or could tell the difference. IMO, that is probably true, but I believe in the halo effect that comes from using the best choice.


------------------
Aloha,
Colin
Internet Sales Manager,
www.hondahawaii.com
www.satoauto.com (my homepage)

TLinBama

Some math for my fellow Americans:

113kW = 151.54 hp
7L/100km = 33.6 mpg

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John

2000 TL WDP Nav

Eskimo

Thanks for the great post Colin. BTW do you know why Honda America seems to have de-emphasize the technical aspects of their products in their sales material? I remember in the early 90s there were alot of emphasis on explaining Honda's engineering achievements in their products. ie. VTEC, double wishbone, engine dyno charts, etc. Looking at Honda's current Inspire web site the marketing approach in Japan seems to focus much more on the technicals information.