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Discussion Starter #1
where would 6 cylinders have the most advantage over a vvtl-i or dohc vtec 4 cylinder engine? would the 6 cylinders pull away at high speeds like at 60-100, or would it pull away at 0-60. for example, lets use these cars: toyota celica gts, lexus is300, honda prelude sh, non-turbo nissan 300zx. the magazines have shown that the prelude for example can beat the is300 in 0-60. what i wanna know is, with better 0-60 times, does that mean they can either keep up with or pass an is300 or 300zx, in 60-100 times? i guess pretty much the question is.. does the 6 cylinder have greater advantage at higher speeds, even if the 4cylinder can outrun it in 0-60?
 

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More Cubic inches and more cylinders help at higher speeds as far as I've experienced...
Eric...
 

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Discussion Starter #3
okay... but how would u explain a GTS taking out the is300 in the quarter mile? the speeds may not reach 100 but it's well over 60. do u think a gts could take out a non-turbo 300zx in the quarter mile? i doubt it. but so shouldn't it be like this: the more sportified the engine or its parts are, the better performance it will get? im talking about 3.0 liter 6 cylinder engines, versus 1.8 to 2.2 liter 4 cylinder engines with VVTL-i or DOHC VTEC.
 

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The 6 cylinder has better torque so it'll pull away from stoplights better than the VTEC 4 or VVTi 4. The VTEC doesn't really start pulling strongly until 4800RPM so if you want to win any drag races, you better be ready to fry the clutch. The Celica's VVTi has a very narrow powerband and so you have keep the engine within this powerband in order to get maximum power. Below 4000RPM, the Celica GTS doesn't feel any stronger than the Celica GT. I've had a chance to drive all these cars and I'll take the IS300's smooth and torquey engine over the other two any day.
 

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Discussion Starter #5
thanks for ur input erick although it didn't tell me much, based on the fact that the gts outperforms the is300.

question for viggen: so where is that powerband on the gt-s?

[This message has been edited by Juggaknot (edited October 07, 2000).]

[This message has been edited by Juggaknot (edited October 07, 2000).]
 

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The powerband on the GTS is about 6000-7000RPM. Yeah sure, a GTS may beat an IS in the quarter mile when it is driven by a professional driver under controlled conditions. However, if you or I were to drive a GTS and an IS, we would both get faster times in the IS. When car magazines run acceleration tests, they do several runs and post the best time. Sure, the GTS's best time may be better than the IS. However, the IS's best time can be repeated very easily whereas the GTS's cannot.


Originally posted by Juggaknot:
thanks for ur input erick although it didn't tell me much, based on the fact that the gts outperforms the is300.

question for viggen: so where is that powerband on the gt-s?

[This message has been edited by Juggaknot (edited October 07, 2000).]

[This message has been edited by Juggaknot (edited October 07, 2000).]
 

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Well let me give you an example....... When I had my GS400 I used to race with my friend with his tiptronic S4. From 0-60 we were pretty close, although I was about a car length ahead. However, at higher speeds, there was no contest. I easily out accelerated my friend in his S4... I didn't know torque until I traded in my GS400 for the E55 which has 5.5 liters and has an exorbitant amount of torque. Acceleration on the highway is a breeze....
Eric...

[This message has been edited by EricK (edited October 07, 2000).]
 

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my take...

traditionally, larger displacement engines had much better low end torque and power deliverly (just look at their torque curves), and could move a heavy car from a standstill faster than a smaller engine, simply due to quicker power application. as multivalve engines made their way into the mainstream, horsepower figures rose, but not proportionally to torque -- torque seemed to get only minor boosts. as a result, a lot of cars with the new multivalve engines saw dramatic increases in speed when the engine was allowed to breathe, but again, only marginal increases were evident off the line. the larger, lower-tech engines still held this domain.

as multivalve design became more prevalent, larger displacement engines began using it (a good early example is the taurus SHO), and they -- due to a good cubic displacement AND better intake technology -- exhibited a flat torque curve not normally associated with a multivalve, high-revving engine. still, big v8's coupled with powerful and intelligently-engineered trannys would beat the smaller, though multivalved, engine in shorter sprints. if the engines were allowed to stretch out a bit, the delta between the two diminshed.

today, we have intake/timing refinements to simple multivalve technology that can drastically change the performance of the engine. variable valve timings that respond to throttle demand help the engine tailor power delivery to the situation at hand -- low-speed, high-throttle situations had one set of valve timing/fuel delivery parameters; open road, higher-speed situations another set. torque curves are flatter than they every have been with multivalve engines due to this accessory technology, and their performance will surpass most reasonably-sized pushrod v8 engines.

of course, most v8s today have the same multi-cam/multivalve heads, so we don't have a smaller-displacement revolution here, we have an industry-wide engine EVolution. it's iterative.

for your particular question, well, it depends on the cars, the transmissions, the drivers, etc. a car making a ton of power and good torque can be crippled by an inefficient tranny or (even worse) a bad driver. i don't believe there is one magic rpm point where a vtec or similar engine will begin to overtake a lower-tech, larger engine, as each multivalve engine has it's intake tech tuned to different flashpoints. my cl-s opens its second intake plenum at ~3800 rpm, and the vtec kicks in around 4400 rpm (i don't know exact numbers...embarrassing), but that's not true for all engines with similar enhancements.

anyhoo, hope this helps.
 

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Discussion Starter #9
wow, thanks guys and geoff for that detailed explanation.

are almost all engines nowadays multivalved?

erick, didn't u JUST get that GS400?
 

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Originally posted by Juggaknot:
wow, thanks guys and geoff for that detailed explanation.

are almost all engines nowadays multivalved?

erick, didn't u JUST get that GS400?
most engines are, yes, and most certainly those that are tuned for high-performance. there may be a holdout or two leftover, but not many.
 

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Originally posted by Juggaknot:
wow, thanks guys and geoff for that detailed explanation.

are almost all engines nowadays multivalved?

erick, didn't u JUST get that GS400?
Juggaknot,
Check the old posts... I bought the GS400 in 1998....
Eric....
 

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Two current non-multivalve performance engines: Chevy LS1 and the Viper V10.

As for less-powerful cars (vehicles) beating more powerful cars in acceleration...power to weight ratio is very important. An extreme case would be any sport bike vs. a Corvette.
 

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For 0-60 times, power to weight ratio and traction are probably the most important factors. Low end torque helps too, but you can use clutch "feathering" in a manual trans to launch at higher RPMs.

As you go faster, max HP and coefficient of drag start to become more important (as wind drag starts to limit acceleration).

Since the IS300 has a good "C.D.", and 215hp max (more than most of the other cars you mentioned), then - YES - I would expect that (as speeds increase) the IS300 would start to overtake some of the lighter smaller cars which have less HP.

The number of cylinders is not really much of a factor here. Looking at vehicle weight, engine output curves, coefficient of drag, tire traction and transmission characteristics are the main things you need to know.

The main benefit to having 6 cylinders (instead of 4) is in engine smoothness.

One benefit to have a broad, flat torque curve is that gear selection is less important when requesting passing power. With the IS300, you should be able to hit the gas at 50 mph and get to 70mph (for passing) without much concern. In a car like the Integra Type R, you better hope that you are in the right gear (say 3rd) to have the engine revving high otherwise you won't be getting alot of response when you hit the gas.


[This message has been edited by TEG (edited October 08, 2000).]
 

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Discussion Starter #14
isn't one of the advantages of having vtec, or vvtli (one of those), is that u get a have a flatter torque curve? or does a flat torque curve not matter? and what does the IS300's or even the 98 Supra's VVT-i do for the output of their engines?

[From TEG: Well, it depends on what sort of different CAM profiles they design in, but VTEC and VVTL-i vary lift and tend to be done to increase high end HP. VVT-i and the BEAMS system used in the IS300 is done more to move the torque peak lower in the RPM range. ]

[This message has been edited by TEG (edited October 09, 2000).]
 
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