why does VCT and VTEC sound so different?

[blackers10]

i was out in maroochydore (sunshine coast QLD) last nite and heard a honda being given a boot full and the Vtec kicked in at what ever RPM and it just came alivethe sound)(im sure most of you have heard it before)

and i was wondering if our VCT and the honda VTEC is of such similar mechanical design.. why our cars dont make such a noticeable change in noise or performance etc ??

any ideas ??

[needfordspeed]

: : : :

[FPVWEPN]

why do turbo 6's and v8's sound so different?????

stupid questions deserve stupid answers

[blackers10]

how is it a stupid question??

1 is a 4 and 1 is a 6 YES..

but dont both share a cam that moves under acceleration to improve performance..
so how does 1 change performance and sound so much compared to the other??

[SpoolMan]

we are all here for some info, some have a better knowledge than others...
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Back to topic:

Is the VCT stock?
Stock VCT have a shocking Factory exhaust, it just choker....

[blackers10]

yes my VCT exhaust is a stocker
but once my hydraulics sell.. she will be booked in for a full 2.5" system with extractors

i know 1 thing tho..
the VCT engine DOES scream at high RPM...dunno if its the same in the standard 6?

[MNM96]

Altering the camshaft timing of a single cam in the AU VCT engine is fairly limited in what it can achieve, compared to a twin cam four. The other thing is that the VTEC Honda probably spins to 8500/ 9000 revs, bit different to your VCT @5800ish.

PS. In life, there are no stupid Questions, Just stupid answers! FPVWEPN, What, of quality, have you added to this thread?

[Mechan1k]

The sounds in the Honda also relies on the sound of the 4-cylinder (a harsher sound than the 6) ... the intake type on the Honda makes a huge difference ... firing order as well.

There's a guy that I work with that has a mint early-mid-90s Integra with a Jap-import Civic Type R engine in it ... and man ... that intake bark sounds mean ... but his intake is custom made and he has an off-the-shelf Mugen exhaust on it.

The good thing about this Integra is it has not kit on it ... just rims/lowered/awesome paint condition ... made 120kw at the front wheels (aftermarket cams and ECU as well) ... ran a flat 14 for the 1/4 mile.

I am not usually a Honda fan .. but when you see a clean example like this ... it goes to show some people do have some taste modifying their cars.

There is so much aftermarket support for the Hondas as they are huge in the US (bigger than Japan really)... so parts are prolific and cheap too.

The Ford I6 VCT doesn't even have much in the way of aftermarket support ... probably about 1% compared to Honda's aftermarket support.

[Mechan1k]

Originally Posted by blackers10

the VCT engine DOES scream at high RPM...dunno if its the same in the standard 6?

Mine screams as well (stock Intech I6) ... but I think that's the motor and gearbox screaming at you to stop killing it.

The I6 is a torquey engine ... where the Honda 4-cyls are a revvy motor.

I think you will find the kW rating on the Honda's is higher than their Nm torque rating .. opposite way around for the Ford.

[Casper]

Originally Posted by FPVWEPN

why do turbo 6's and v8's sound so different?????

stupid questions deserve stupid answers

and rude people deserve rude answers... pull your head in.

One significant difference is that VTEC and VCT actually are totally difference systems.
In summary, the VCT system simply advances or retards the cam at different RPMs. The VTEC system doesnt, it changes the cam profile at different RPMS (effectively giving the honda 2 entirely different profile cams for the inlet at different rpms).

VTEC (which stands for Variable Valve Timing and Lift Electronic Control) is an electronic and mechanical system in some Honda engines that allows the engine to effectively have multiple camshafts. As the engine moves into different rpm ranges, the engine's computer can activate alternate lobes on the camshaft and change the cam's timing. In this way, the engine gets the best features of low-speed and high-speed camshafts in the same engine.

[stiddy]

ok going by changing cam profiles at different rpms..

could you do something simliar with a BA dohc?
change a cam so it comes on song at a higher rpm??
so its in like 2 stages..

[xr8ute]

Originally Posted by stiddy

ok going by changing cam profiles at different rpms..

could you do something simliar with a BA dohc?
change a cam so it comes on song at a higher rpm??
so its in like 2 stages..

I believe the code existed in the BA, but they have only started doing this with the BF i6, but I am not sure if it was across the board or just the BF turbos.

The VTEC actually has 2 lobes on each cam. So not only can the cam timing be changed (relative to the crank as well as each other), but the actual lobe can be changed from one to the other.

[xr8ute]

A good VTEC resource here, http://www.leecao.com/honda/vtec/index.html

[Mechan1k]

VTEC systems works on oil pressure change as well ... hence why VTEC doesn't like changing over the best when running cold as well.

[blackers10]

thanks guys

at least SOME people have some brains to respond like an adult to a genuine question

[stiddy]

Originally Posted by Mechan1k

VTEC systems works on oil pressure change as well ... hence why VTEC doesn't like changing over the best when running cold as well.

ive noticed that with my mates integra, wont hit vtec when the engine is cold..
but a vct falcon will go straight to revlimit :P

[outback_ute]

Yep the change in sound has more to do with the more aggressive cam profile (together with the timing). The BA/BF is still only doing cam timing, the BF change now controls the intake and exhaust cams separately whereas the BA had them moving together like a single cam.

[blackers10]

but does a BF head fit on an AU?? that could be quite interesting once people figure out how to control the VCT a lil more aye..

[Casper]

Originally Posted by blackers10

but does a BF head fit on an AU?? that could be quite interesting once people figure out how to control the VCT a lil more aye..

Nope.

[SpoolMan]

Originally Posted by blackers10

but does a BF head fit on an AU?? that could be quite interesting once people figure out how to control the VCT a lil more aye..

The AU 6 engines are completely different from the BA & BF 6 cylinder..

[blackers10]

aa ok

bummer eh

[parawolf]

I still noticed a few posts on this that didn't get it after Caspers spot on response so let me be concise.

VCT = Variable Cam Timing

VTEC = Variable Valve Timing and lift Electronic Control

VCT adjusts the TIMING of the camshafts to produce either optimium torque/power/fuel consumption based on taught, expressed throttle conditions and load.

VTEC improves on VCT by improving the LIFT of the camshaft so the valves open higher to improve airflow at high RPM thus improving power. This is usually only a high rpm thing as the improved lift is not as great a benefit at low engine speeds vs improved timing as you want greater torque down low.

VTEC on an I6 wouldn't be that useful as the engine really does not rev hard enough. If it could rev out to 7500+ rpm then it could be useful.

[Bucknaked]

VCT is a 6 and the VTEC is a 4? If so, then I imagine trying to get a 4cyl to sound like a 6 is as difficult as getting a 6 to sound like an 8

[FPVWEPN]

: : : meh

[Karnage]

Originally Posted by stiddy

ive noticed that with my mates integra, wont hit vtec when the engine is cold..
but a vct falcon will go straight to revlimit :P

the Vtec system does rely on oil pressure, but this is to physically move the cam accross in the engine, it uses a common set of rockers and moves the cam to change profiles, the ECU has many....and I mean F^%&ing HEAPS of protections modes, if anything isn't right it will not engage vtec, ie engine temp, all sensors, air temp...everything.

The other thing is..does the VCT engine use multi valves? as Mechan1k said, induction has a huge impact on the sound of the Vtec engines......they also run 11.5 : 1 compression

[parawolf]

Originally Posted by rrpilot

The other thing is..does the VCT engine use multi valves? as Mechan1k said, induction has a huge impact on the sound of the Vtec engines......they also run 11.5 : 1 compression

VCT just does Variable Cam Timing. It uses the same camshaft, same lobe profiles, same lobe seperation at all times, however it adjusts the advance and retardation of the opening and closing of the intake/exhaust valves.

It does this by affecting the gearing (not quite but a simplistic enough description) similar to the way that gears work on a push-bike. By affecting the gearing intake or exhaust valves can be open at different times to improve all manner of performance.

All it does is adjust the Cam Timing, not lift, or anything else. The cam's have one set of lobes, not staged like Honda VTEC or Toyota VVTi-L (Variable Valve Timing and Lift).