Because in a road car you want emissions, economy to be good and a relatively slow throttle response. Therefore you use less lift, which tends to mean less duration, when tends to mean you will use less overlap - less overlap is good for emissions and economy.
But when you want the most performance (WOT at high rpm) you don't care so much about economy or emissions, so you can higher lift and more overlap to give more scavenging and theoretically greater volumetric efficiency.
Thus, vtec isn't great for racing becuase in racing you want the large cam profile (and the most performance) all the time, else you will lose out to somone who does everytime you revs drop below the vtec range.
On the flip side I suspect that 99% of people who like vtec do so for the wrong reason. They either like the sound (subjective, personally the thought of a car changing from 4 cylinder plodder to 4 cylinder awake plodder doesn't really thrill me), or they think (as stated above) that you engine goes from 100% to 110% performance without realising it's probably more like 80% to 100%. Thus, if you do a time average of the actual performance vs the theoretical maximum performance (i.e. normal driving vs WOT all the time) you will find you engine is running at about 85% of it's ability (but also 85% of the emissions, and using just 85% of the fuel [actually less because the ECU will attempt a lean burn mode depening on the catalyst state, position etc]).
In other words vtec is a fancy way of bypassing emissions and ecomoncy regulations rather than suddenly making engines 'better'.
Good points Tristan but don't forget the other methods like TVIS/VVT(l)i. These systems are basically the same but provide a lot more smoother torque band. TVIS is the older system and basically it's a set of butterflys in the inlet manifold which can be closed or open, depending on vacuüm in the inlet manifold. If closed, only 4 inlet ports are open and that creates higher air speed for more torque. At 4400rpm a vacuüm solenoid sends a signal to the ecu and then the butterflys will open the remaining 4 inlet ports. Cylinderhead will have to do it's work up from here. This systeem feels much like VTEC, but it operates very different.
VVT(Li) is much much more complicated and it uses way more signals from the ecu such as
- engine rpm
- TPS signal
- Inlet vacuüm
- Coolant temp.
Based on these signals it can operate from 0rpm upto the revlimiter and so it changes constantly. Toyota has mapped these ecu's in such way that it operates much like a VTEC, you also get that agressive switch @ 6000rpm but of course with a standalone ecu there is not much a man can't do
I have to say I really respect these engines and their systems. Let's not forget systems like the first VTEC and especially TVIS are very old (1984) and they developed both systems in a great way providing fun, high rpm's and torque at the same time.
I'd be interested to see a torque curve (or a power curve before you all start) of the engine using the different cam profiles and timings, because I expect the 'mid range torque boost' with the different timing won't be as great as some people think. The huge main reason of Variable Valve Timing (including or not variable lift) is emissions and economy. It's highly likely (but impossible to say without more data than the engine departments are going to divulge) that the racier cam profiles and timings are better throughout the rev range in terms of performance, but seriously lack in terms of economy and emissions, whereas the less racey profiles/lifts/timings sacrifice a bit of torque for cleaner and more complete burning.
As I say it's almost, if not totally impossible to say this with a great deal of accuracy without all the data, which we ain't likely to see. Ever.
Well, just to be fair, I drive a 1994 Civic V-Tec as well as the subaru(subie = my fun car, civic = my get to work car). I've opened up the civic, and I'll tell you, vtec or not, that thing is SO slow. i do like the handleing though, but none-the-less, I still think it's a slow car and nothing special. I've blown too many of them away on road coarses in the subie.
Have you driven other cars with small capacity engines tuned to produce peak power at high rpm? They're not real fun to drive around town etc, pretty grumpy down at low rpm. Much as I think vtec is a bit wrong and silly, (much better, smoother, ways of producing higher peak power imho) it's signifigantly better than the same peak engine tune without it...
if you look at a vtec engines torque plot, it's a bunch of fairly flat steps, (the steps are one of the main reasons I don't like vtec) as opposed to a 'normal' high rpm tuned small capacity engine, which usually rises pretty steeply.
Emissions - save the whales
Economy - make the arabs poor
Drivability - allow grannies to cope with it (not actual grannies, just people who don't want a high powered car, but want the high powered badge)
Thus, anyone who claimes to like vtecs and driving probably can't drive
That'll stir the conversation up a bit
well the engine uses less fuel at low revs and has ok torque b4 the cam switch, then at the cam switch over it uses LOTS of fuel and lots of air and for non forced induction its a very clever system that has had very little "f*ck ups" in the whole time honda have used VTEC in production cars!
any ways, all this is available to ppl if they wanna read it on the net....
and every one wants somat differnt from an engine... for me, Honda is the future!!!
in honda engines, when the cam profile changes over in the girlies civic type r, you can ALWAYS hear it, and even in my mums 1.8 SOHC accord you can hear and feel it, just has less of a kick
Well, you are still driving a fourbanger, doesnt change that, what have you done with your impreza?, over 600bhp is not that common to get out of their boxer
I don't need to prove anything - it's a well known fact that America can't make good cars, just that America doesn't know it yet. Keep trying though, it's nice to see the amusing attempts
lol...tristan, i always look forward to your comments....they always make me laugh. i agree with you, american sports cars still leave something to be desired. I think we have everything we need, it's just the fact that no one can figure out how to put it all in one vehicle and make it all work together.
yeah if you compare stats of z06 to other cars or lap times you'll see it does corner well. But its cool to hate america so whatever bash the Z06 and be ignorant if you want.
Well, having driven a ZO6, I'd have to say that it isn't as bad as some think with the cornering... but at the same time, it also isn't as good as GM said it was. Try to outhandle a 911 Turbo S with that thing. I did, and it didn't work. Went wide on the turn at the end and half into the grass just trying to keep up with it in the turn. Oh, and both cars were completely factory. I do enjoy the feel of a good German/Japanese/British/Italian sports car. Now, before I'm called part of the problem about the bashing of American cars, I'd like to say that I do recognize that they have a lot of power and straight-line know-how. Later this fall, I'll have a Silvia shipped over and I'll be able to indulge in one of my favorite sports. *Gets ready for insta-hating*
Drift. Before people start hating, think of how many of you like Rally racing, then tell me that they don't drift at all, and that drifting never helped anyone. (I guess that was a little too pre-defensive ) Anyways, back on track.
American cars: Straightline
Euro/Japanese cars: Handling with power :revs: :rally_dri
no they don't! There are not many countries that make nice cars, many don't make any I believe. Taking the PC 'all countries make ok cars' line is just a cop out
Hmm, a lot of the design and testing on the C6 was done by some German engineers in ... er.. GERMANY. :P The C6 Z06 ran a lap at Nurburgring in 7:42.99. That's pretty damn fast. If a car cant handle, there is no way it can do a lap at the 'ring that quick.
I'll be the first to admit that most American cars are crap- I've owned two of them. My 20 year old Scirocco with blown shocks and Wal-Mart tires could out-handle my 00 Camaro with ease. There are always some exceptions to the rule though, the new Solstice and C6 being two of them.
I've seen topgear, where the female instructor Sabrina i think her name is, takes a Ford Transit around the ring in about 10 minutes. Don't tell me that gaining only 2 minutes and 18 seconds on somewhat 20+ km's from a DIESEL van is a good thing.
at least spell it right. now i am not saying there is a replacement for displacement. most of the time there isnt. but you have to compare a car to another car in its own class. you cant bring a honda up to a Z28 and expect it to keep up with it.. it's not going to happen. the power to weight ratio among other things is so drasticly different that well of course the Z28 is going to smoke that cars arse.
what you compare is a honda to a Neon or a Z28 to a mustang. something with the same displacement.
The whole tuner scene started with 20 sumthin adults wanting more power for there little 1.8-2.0 L engines. and the whole honda civic started up in canda not in so-cal btw. Iv'e met some Dodge neon srt-4's and they are not anything to laugh at. for under 20,000$ they are fast. and what does a z28 start at 28k? 30k? your saving money.
The only problem with tuners this day in age is everyone and there mom goes out buys a big oversized muffler and a wing then calls it a import.
sorry my friend. it takes alot more then a pep boys racing muffler and a 200$ fiberglass wing to call your self a tuner.
it takes alot of time and alot of pride to craft a nice tuner.
For ME.. not you this is IMO.. a tuner isnt how flashy or how loud or how freggin clear your headlights are... it's the clean nice job of what you have under the hood.
I dont have a carbon fiber hood... i dont have a Fiberglass body kit. there isn't a wing... there arn't rims,there arn't racing seats... except for the HID system you wouldnt know it's been modified. The exhaust tip even looks the same. (ya unless your pullin 600+ HP that 6" exhaust is just slowing you down)
) Anyways, back on track.