nadir_s

hey guys, i remember reading a post a while ago on this forum about our VQ engines having "VTEC"... Variable Timing Electronic Camshaft... i think that's what it stands for from the last time i read about it. Anyways, i was only interested because my friend has the RSX type S and we were taking about VTEC and all. I just wanted to make sure if this was true or not. For the first time since i've had the car, i've been perfecting my manual transmission driving and i "opened" up the driving... after hitting 5k RPM the car hauld MAJOR *** till about 6.5k RPM!!!! BTW i searched for the post but couldnt find it. Just curious... thanks

NickStam

iTrader: (3)

VTEC=VTC I think

JetBlackMax

iTrader: (12)

Ok, what is VTC then? its not VTEC? Im tryna learn here

La Jolla Max

When VTC is activated, the intake and/or exhaust cams are rotated to advance or retard timing. VTEC engages a more radical cam profile by uing three cam lobes (as opposed to the normal two) for every set of intake valves. This is to the best of my knowledge: VTEC cams are hollow. Upon activation, oil flows through the cams and pushes against a metal pin which connects the three lobes together, and pushes out the high rpm lobe. This means the roller rocker arms on the low rpm lobes are essentially longer, and can hold the intake valves open farther and longer (whew!)

JetBlackMax

iTrader: (12)

ahh i see. sooooo does our maxes have VTEC? LOL

sx7r

iTrader: (15)

no.

syc

no, we don't have VTEC. that's why we all need to get ourself a variable intake to advance the intake valocity. I just know a little about variable intake but know more about VTEC. I think nissan doesn't have something similar to the VTEC technology so far, right? I think this is because nissan doesn't need to for now. variable intake works well.

mzmtg

iTrader: (11)

We dont have variable anything

Keh mon

The 5th gens have variable length intake runners, and the 2k2's have that and variable timing correct? That's one reason why the 5th gens have more hp.

tmkforever

Yeah maybe in your head....unless you have a VI, the opposite should be happening. Power drops off after 5K or so until redline.

Jepht20

iTrader: (10)

we have variable intermittent wipers... that's a start.

max7

nadir_s

hmmmm, perhaps you're right and it was lower than 5k rpm.


Anywho, thanks for the replies.... so we don't have vtec. oh well! VQ Power!

Jeff92se

iTrader: (82)

VTEC does not equal VTC
VTEC does not equal VI
VTC does not equal VI

mzmtg

iTrader: (11)

Not even all of us have that...

dwapenyi

iTrader: (3)

keep in mind that The Nissan VQ is a DOHC V6. The only DOHC in Honda/Acura's lineup is the top notch NSX.
TL-S, MDX, RL, Accord, etc, all have SOHC V6s. The VTEC makes up for the lack of DOHC, sort of, but not quite. Compare similar displacements between Honda and Nissan you'll see that Nissan engines tend to make more torque throughout the rev band than the honda version.

In other words, there's no substitute for cubic inches . . . .and DOHC

Oh yeah, and Honda DOHC 4 bangers don't count, b/c even with DOHC, their torque still doesn't even come close to Nissan motors.

DW

Jeff92se

iTrader: (82)

Hmm well..... dohc only means dual overhead cams. That in itself doesn't mean anything. And DOHC doesn't inherently have any HP bearing.

IMHO VTEC is a better way of obtaining hp than VI or VTC.

dwapenyi

iTrader: (3)

Only? DOHC design on a motor with 4 valves per cylinder is better than only.

DW

Jeff92se

iTrader: (82)

http://www.autonetwork.com/firstlook...iews/01mdx.htm
Whether or not it's DOHC or SOHC, it's 4 valve per cylinder

Bags

iTrader: (3)

speak for yourself

dwapenyi

iTrader: (3)

Where's that "head banging the computer desk" gif when I need it

I know they are both 4 valves per cylinder. That's why my initial remark mentioned the only difference between Honda and Nissan V6es: D O H C

The only DOHC V6 in Honda/Acura's entire lineup is the NSX. VTEC DOHC V6. Part of the reason it goes for $90K.

DW

Jeff92se

iTrader: (82)

Don't know what you are getting at. Explain EXACTLY what dohc has over sohc when both applications feature 4 valves per cylinder?

syc

DOHC has following advantage over SOHC:
1. could achieve higer engine speed because it has less valve train mass and simplifies the design of the cylinder head and better STIFNESS of the valvetrain,
2. for 4 valves, DOHC permits the valves to be to either side of the head and operated directly by the cams -> It allows the spark plug in the center of the combustion chamber, which gives efficient combustion

but all above just theory. efficient design of a SOHC can be as good as a low tech DOHC.

Jeff92se

iTrader: (82)

I thought a sohc has less drivetrian mass ie.. one less cam, one less sprocket, shorter chain etc. And I believe all the Honda motors are high reving so I don't believe they have any sort of valvetrain problems associated w/ high rpm running.



I believe Hondas have a 4 valve per cylinder configuration that allows the plug to be centered. I actually don't know of a 4 valve head that doesn't. But I believe Honda does use rockers to actuate the valves.

Considering Honda has one of the best head designs in the industry, their sohc seems be at least the same or better than most dohc designs.

syc

reason there is only one Honda DOHC V6 VTEC is the cost.
SOHC VTEC is already complicated (theory is simple, but actually not. Honda did a good job), consider DOHC VTEC. even for DOHC VTEC, there are different designs due to the cost (what different design, I forgot, but I know the one in Civic and the one in S2000 are totally different). then here comes the V6 DOHC VTEC. can you imagine the enigne is NSX is a 12 years old technology!

syc

you are right about most of the Honda part, but think about why there is a Honda DOHC V6 engine exist.

read the following articles that I just found, there are too many advantages in DOHC.
http://www.allpar.com/eek/cams.html
http://www.jag-lovers.org/e-type/perf.html

and this one is the best, talk about how DOHC design makes it easier to add variable valve timing.
http://www.datsuns.com/Tech/ohv_vs_ohc.htm

Jeff92se

iTrader: (82)

The first article deals mainly w/ dohc vs pushrod tech.
2nd article is interesting but doesn't really directly explain why Honda went to great lengths to use a sohc to actuate 4 valves vs just developing a dohc from the beginning.

3rd article. Well since Honda has elected to use varible cam lift tech vs varible cam phasing tech that kind of puts a damper on that theory. Of course it would be nearly impossible(if not outright impossible) to control cam timing on the exh/intake cams on a sohc 4 valve motor(since one cam is actuating both the exh and int cams)

I still don't quite see what you are getting at. Honda has 4 valves per cylinder, plug in the middle, their valvetrains are obvoiusly good enough to run as high or higher than most other dohc v6s and the issue of valvetrain stiffness is sort of moot as Honda uses TWO camshaft profiles on most of their intake cams(meaning that they don't need aggressive cam profiles for either the low or high end.

dwapenyi

iTrader: (3)

My observations come from empirical evidence, dynos etc. The DOHC variable nothing VQ30DE is better than the SOHC VTEC V6 in the Honda Accord, even though the Accord has 200 hp to the VQs 190. Why? the VQ has a fatter torque band. If you think the 3.2 liter V6 in the Acura TL/CL-s is a better comparison, that SOHC VTEC V6 displaces 200 cc more than the VQ30DE-K. It does make more hp as well, but its torque isn't as amazing as its hp. Drive one of them around and you'll see that the it displays the typical Honda characteristics, down low torque nothing to write home about, but bang bustin hi revvin top end that is un-beatable. VTEC SOHC motors are Jekyll and Hyde engines, pussycats down low, bahn runners up top. The Honda S2000 is a classic example. It's' very powerful, but you've got to put the engine in VTEC mode before you engage the clutch With a DOHC V6 the power delivery is more linear, and that is better, more livable. At least with the Nissan VQ.

If I had to choose SOHC VTEC V6 or DOHC V6, I'll take the DOHC

DW

Jeff92se

iTrader: (82)

But what part of the DOHC play in the hp or torque differences? None that I can see. How could it? Probably one of the most overiding reasons Hondas make more power in the high rpms is that is Honda's attitide toward how to make power. If they designed their cams to make more lowend(at the expense of high end), they probably could. But it would really go against the way they choose to design and run their engines?

S2000s have no torque? Name a 2 liter na engine that has significantly more torque. At the same time name 2 liter na engine that has more hp(that is obd-II compliant) Why give alot of torque anyway? The S2000 is not a heavy car. Honda could put one of their V6 engines in there but it would have upset the chassis balance and disturb the essense of what that car is about.

I guess I see your point about wanting a v6 w/ more low end punch than a high rever. It's good that now we can have both w/ the 3.5 vq w/ VI and VTC tech. I just wanted to let you know that DOHC and SOHC in itself doesn't have big determining factors in the hp/torque characteristics of a V6 engine.

Bam823

the vq engines have a variable valve timing called CVTC which stands for continuous variable timing control. The camshaft's timing is advanced or retarded to increase engine output. Unlike VTEC, CVTC doesn't have anything that varies the lift or duration of the valves, so it only varies the timing of the camshafts

syc

all I'm saying is that those are just theory. I'm not not an engineer or something. I just know from the book.
Honda use SOHC because it's cost effective and their design is good such that the engine is compatitive in the market. IT IS AN EFFICIENT HONDA!! Why does Honda wanna put a more expensive engine in a sedan to compete with others while the SOHC is just as good.
the SOHC VTEC V6 run higher than most other DOHC is true, but it doesn't run higher than the DOHC VTEC V6 in the NSX, even the one from the 1990. It's true that SOHC VTEC V6 could run higher (like the new Accord coming out to compete with the 3.5 altima), but so could the DOHC VTEC V6 (just that Honda doesn't need to because of the market).
I don't know about the honda plug, but many SOHC has the plug little off center with a certian angle to the chamber due to the blocking on top, from what I read.

ColgateU

Whoever said the CL-S/TL-S engines have no low end torque has no idea what they're talking about. It is very true, however, for the Accord V6, but NOT the TL-S/CL-S. Comments by Road and Track and Car and Driver on the CL-S/TL-S engine are "The engine is extra-ordinary" and "The engine is delicious," respectively. It makes 232 lb of low end torque across a wide band from 3500-5500 RPM's and at 6100 RPM's, 260 hp comes in to play. Heck, off of a light with the vehicle stability assist off , and my foot to the floor, I can leave a cloud of smoke that makes seeing anything impossible. And the roar from the engine bay in VTEC from 4800-7000 RPM's must be heard to be believed.

SteVTEC

Honda chooses SOHC VTEC for most of their designs because it is more cost efficient, you have less mass in the head, and their VTEC system allows the engine to make power about as efficiently as a DOHC non-VTEC head. Compared to a DOHC engine, you lose the ability to precisely tune intake and exhaust valve timing separately (all SOHC VTEC engines vary only intake valve timing), and the SOHC arrangement limits the flexibility engineers have to put valves, ports, and spark plugs exactly where they want.

The Accord V6's SOHC VTEC engine S U C K S, but it has nothing to do with the fact that it's a SOHC engine. Here's some crank dyno figures for the VQ30DE and the J30A1 that I put together based off of stock chassis dyno's (converted back to crank figures)





The reason the Accord V6 SOHC engine has so LITTLE low-end power is because Honda gave the non-VTEC cam lobe this crappy econo profile. It only lifts one intake valve below 3500rpm. This is good for better swirl, which helps fuel economy and emissions, but it also MURDERS low-end power. After VTEC, they put a more "normal" cam profile in, but even with VTEC the top end still isn't any better than a VQ30DE.

The Acura TL-P (J32A1) and TL-S engines (J32A2) are MUCH MUCH better as far as low-end power. Especially on the TL-S since it also has a variable intake manifold. On these cars, Honda actually put REAL camshafts in them that have profiles capable of generating good low-RPM thrust, unlike the Accord V6. I wish I had known that before buying the car, but live and learn.

The Honda/Acura engines are good, but still not as silky smooth as a Nissan VQ

iansw

iTrader: (7)

Actually, what everyone on this board calls the "MEVI" is really the VIAS system.

Variable Induction Air System.

I should know, I'm not only a member, I'm also the President.

IanS

iansw

iTrader: (7)

Ummmm.

here's the Dyno curves (at the wheel, with 18's on) of my car with and without the VI, then with the MEVI.

See how flat that is? I've never seen a honda do anything like that with a VTEC Engine....power just stays steady all the way to redline....



IanS

SkylineGTR

Nissan does have engines with VTEC type of systems in it, but only in japan. SR20VE, and SR16VE, both small, high revving high output motors, i think they both put out around 200hp.

BatKeith

Anyone hear about the 03 Accord? They got angry that Nissan not only made powerful sedans, but had the nerve to tell people about it!

Go read the preview on motortrend.com but basically...

- Exterior redesigned to be more "muscular" I think that it is still extreeeemely boring.

- Base Engine is the 4cyl i-VTEC that outs 160 horses. Isn't that the same engine in the RSX base?

- BUT the accord v6 will be 240 horsepower. I dunno if its DOHC or not, but it displaces 3.0l also. Seeing as it's vtec-power though, the torque curve probably looks something like half of a half-pipe.

- 5 spd auto / 5spd manual (their first in an accord) / 6spd (available only in a particular trim of the v6 coupe).

And you know what i say? who cares. It's boring and its slow. I'd rather have a Ford Focus zx3 than one of these cars.

Jeff92se

iTrader: (82)

Ian, I've driven a GSR w/ VTEC. There is no way any na Nissan 4 banger has anything close to the revability or hp holding power to that engine. Don't know about the Honda V6 VTEC engines though.

SteVTEC

If you want to see a completely FLAT VTEC dyno (except for the VTEC hump), look at an S2000 dyno. Seriously, that sucker is completely flat from 3000rpm up to 6000rpm, where there's about a 15 lb-ft hump from the x-over, and then it remains perfectly flat AGAIN almost all the way up to 9000rpm. Meanwhile the Horsepower curves just goes linearly up. Look at Kev's boosted dyno's and that's about what they look like.

JsL

iTrader: (5)

Since Honda is known to be econo-boxes with their ULEV and LEV, they have to live up to thier name and sacrafice low end and have only one intake valve below 3500rpm with ecomonmy in mind, thanx steVTEC. It makes a lot of sense. Those are interesting dyno charts also

So our engines have VTC right?