The original question was not "11(13) more HP or 6 more lb-ft of torque?" Lets not change the parameters simply to suit your argument.

You're whole argument is predicated around looking at specific speeds of the motor. However, you MUST look at the big picture. The 05 VQ will have a 500 RPM higher redline. This is also coupled with more power. This results in one of two effects. With the same gearbox, the New VQ will be able to stay in the lower gears slightly longer and enjoy more torque multiplication. Or they can take advantage of the higher redline and use slightly lower gear ratios and get more torque multiplication.

The car that will accelerate fastest will be the one that has the most area under the curve measured at the wheels. Whether you measure it in HP or torque, it must be done at the wheels. And you must measure the actual torque output. HP will stay the same relative ton Engine RPM regardless of wheel speed so HP tends to be much easier to use on paper. Torque on the other hand, varies because of the different torque multiplication factors of each gear. Looking at simply the peak torque or peak HP alone doesn't tell you all you need to know to properly assess this. Short of a dyno, it is a good representation of an engine's characteristics, but with currently advancing technology, it's becoming harder to make good assessments before all these variable cams, intakes, and lift came into the picture with simply peak numbers.

 

"The increase in HP for the new motor happens way up in the rpm range where you will get more acceleration, but perhaps not enough to make up the lost power from 0-4800 rpm "

If we are simply talking in terms of fastest acceleration possibly, how long do you actually stay in that range of RPM's? 1st gear typically lasts only the 1st part of any standing start acceleration contaest and it should be the only gear that will see almost all of those RPM's. The top end is where you'll be the rest of the race. So what is really most important? This is subjective. Those that drive hard will probably enjoy the extra HP. Those that don't might enjoy having more low-end torque, but we still don't know what the HP/Torque curve of the 05 VQ looks like at those RPM's. And btw, we are talking levels of torque that can hardly be felt...

 

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However, if we want to bring weight into the picture, a simplified way to look at this is to compare the HP to weight ratios.

03/04 - 3435/280 = 12.26
05 - 3512/298 = 11.78

Almost a 4% increase. And while this is a siomplified way of looking at things, you'll find it will be a pretty good representation of how quick a car will be.


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That is exactly correct -- and you should expect the maximum acceleration to improve by approximately 4%.

 

See my previous post. For a mere $80 and literally ten minutes of your time, you can jack a 2003-4 G35 up to 287 HP and 274 torque--just add a 350Z intake tube. Now, the 2005 would only gain 2% HP/weight ratio and that only at redline. At 4800 RPM, the 2005 loses 7-10% HP/weight compared to the mod-ed 2003.

 

CKwik,

I agree with you about being in the upper rpm range once you shift out of 1st, but you are assuming that the new model makes it's extra power from 4500 rpm or so on. My point is that the old motor had a rather sharp drop in torque above 6000 rpm (we've all seen the curves). So improving the torque slightly above that point (flattening it out) will give you the extra 20 HP. That gain in power might possible last for only 500 rpm for all we know. The old motor may make more power up to 6000 rpm. Each shift brings you back down to 4000-5000 rpm or so depending on which gear you're shifting into. We already know for sure that in the first 800 rpm (to 4800 rpm) the old motor has the advantage. I suspect that the old motor may even have the advantage to a slightly higher rpm.

Basically, the question of 20 hp vs. 10 lb-ft of torque cannot be answered until we see some curves.

 

But the question then is, for how long? Under speculation, you can plot the points on a graph, and simply drawing a line through the points will show that the torque curve of the new VQ will drop off less than the old one. And to top that off, it does rev slightly higher so after the shift it will start the next gear slightly higher as well(assuming the gear ratios are the same). While I agree we do need to see the actual dynos as I have already bees saying, it's much easier to speculate about what is going between the torque peak and the HP peak than what happens at low RPM's. The factory ratings at least give us 2 reference points to work with at the higher RPM's. Outside of that, it is difficult to know what is happening.

 

CKwik,
OK. I agree that the gain will be due to the higher rpm (7000 vs. 6600). The original question, as I was warned of earlier, is what do you prefer 20 more HP or 10 lb-ft of torque. I brought up weight, and was told that had nothing to do with the question.

 

Actually, the gain is due to higher RPM and higher torque at that RPM. And as far as weight, it really doesn't have anything to do with with the characteristics of the motor. The new G35 will likely have gained most of the additional weight regardless of which motor they used.

Discussing RPM in relationship to torque and HP is relevant however, as it is directly related to the relationship between torque and HP.

 

Alan P .The rate in which you can apply this 600 ft/lb torque is minimal thus your hp would also be minimal. Without numbers your statement about a low torque operating at a high rpm can out accelerate a car with high torque at a low rpm is meaningless. Please explain.

 

acceleration is a mixture of torque and hp. You need the torque to help accel but once your car gets up into the high rpm's, torque drops and hp is what ends up pulling you car. If the 10 ft/lb torque was from 3000rpm to redline, then sure i'd take the torque, but the 20 hp difference was also from 3000rpm to redline...i'd take the hp. It all depends on where the gains are the the topic was too generic to explain.

'03 G35c DG/G 6mt, full options
clear corners, tint, z-tube/popcharger,
nismo titanium shift ****

 

Mathematically speaking, it would always be better to take the 20 Hp over 10 ft lbs torque (T). At 5,252 rpm, Hp = T. So you would be getting 20 T for the 20 Hp, instead of only 10 Hp for the 10 T.

At 2000 rpm 10T = 4.8 Hp, but 20 Hp = 52 T!!
At 6000 rpm 10T = 11.4 Hp, but 20 Hp = 17.5T!!

Things are different in the real world because it would be impossible to achieve a consistent increase of one or the other over the whole rpm range.

I don’t want a 300 Hp car with 100 T and I don’t want a 100 Hp car with 300 T.

I like 280 HP and 270 T.

Balance is key - so I'll still take the extra 10 ft lbs.

2004 G35C 6MT Black. Killer.

370759-Dyno2small.jpg

 

Well before anyone makes any real judgements, we really need to see what the dyno looks like. I speculate the new VQ will enjoy a somewhat flatter and broader torque curve but who knows.

As far as torque vs HP, when the goal is going fast, it's HP that will generally be the most important number. HP is derived from torque(not the other way around as HP is not any kind of real physics measurement). HP is a calulated number to show the work done by torque. This number takes into account the RPM at which torque is made. Peak torque is almost always made before peak HP. In a given gear, the car will accelerate fastes at peak torque.

But then why is HP more important you ask? To understand this, you have to look at the amount of torque measurements at the wheels. I'm not talking about what a dyno chart says as it compensates for gearing, but the actually torque. The lowest gear provides the most torque multiplication therefore you will experience the most torque in 1st gear. Most of you probably already know this or have figured it out. But why is this important? Higher RPMs allow you to stay in a lower gear longer. As long as you are making a sufficient amount of torque, then you will accelerate faster by staying in the lower gear longer before shifting. 270 lb-ft of torque at 4800 RPM is 246 HP. If you made 246 HP at 6200 RPM you would be have 208 lb-ft of torque there. And while the torque numbers are different, they actually are performing the same output. Lets aim to produce that HP at the same car speed. For ease of calculation, we will use thransmission output shaft speed and assume the rest of the drivetrain is the same. Well use a target shaft speed of 3000 RPM. To cut down 4800 RPM to 3000 RPM you would have a gear ratio of 1.6:1. Multiply this by the 270 lb-ft of torque the torque at the shaft would be 432 lb-ft. To get 3000 RPM from 6200, you would nead a gear ratio of 2.067. Multiply the 208 by this and you get 429. While the number is off, it is purely as a result of rounding off the numbers. If I did the calculation straight, it would be exactly the same. In either case, the torque and HP output at a 3000 RPM output chaft measurement is the same.

Now throw in the actual 280 HP we make at 6200 RPM. This is 237 lb-ft of torque. Through the same 2.067 gear ratio as above, you get 490 lb-ft of torque at 3000 shaft RPM. What this means is at the wheels, even though there is more torque at 4800 RPM, given the same wheel speed, the torque at the peak HP can produce more torque at the wheels. Putting the most torque to the ground the entire time you are accelerating will give you the fastest acceleration. This is why HP is generally a much better representation of acceleration.

As far as what is actually better in the real world is rather subjective. Having more low-end torque can make driving around town a bit more comfortable for most. But for those that drive like they are trying to get the checkered flag, HP will be what is really important. The new VQ may perhaps even be more flexible. I really speculatethat the low to mid RPM torque will have increased through cam profiles and timing that are better suited, while the variable cam timing allows the motor to maintain more torque overall through the higher redline. I believe the new Z is on the showrooms and dyno results of these will probably shed a lot of light as to what to expect and what the actuall results will be.

"acceleration is a mixture of torque and hp. You need the torque to help accel but once your car gets up into the high rpm's, torque drops and hp is what ends up pulling you car."

A lot of people have this school of thought, but it is wrong. HP does not keep a car going anymore than torque does. Where there is torque there is HP(with an internal combustion motor). The torque is actually always the force causing a car to accelerate forward. HP is just a numerical representation of how well the available torque is used when coupled with RPM. Think of HP like a measurement of efficiency for Torque(not in the fuel consumption sense). It takes into account the fact that we have transmissions to better use the available torque. In a way, forgetting the fact that these two numbers exists would simplify things quite a bit. Using only one set would tell you all you really need to know. And I would like to kick the VW marketting department's asses for spreading this same incorrect belief in one of their commercials...

 

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Alan P .The rate in which you can apply this 600 ft/lb torque is minimal thus your hp would also be minimal. Without numbers your statement about a low torque operating at a high rpm can out accelerate a car with high torque at a low rpm is meaningless. Please explain.


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It's amazing to me how poorly torque and horsepower are understood on this and other car forums. Power is equal to torque multiplied by angular frequency. This is not a "simplification" only applicable to other engines; it's as fundamental as any physical law. If power P is given in units of horsepower and if angular frequency is converted to RPM then

P = torque*(RPM/5252).

A car's acceleration is proportional to its horsepower-to-weight ratio. Thus torque ALONE does NOT tell you how well a car will accelerate.

For example, I own both a G35C and an S2K. These cars have very similar acceleration specs -- but the G35C has vastly more torque. However, the S2K compensates for a lack of torque by operating at much higher RPMs. The S2K can be loud and unpleasant to drive at such high RPMs. Keeping up with the G may mean downshifting all the time and burning up a clutch. But the fact remains that the S2K has slightly better acceleration despite having inferior torque.

It's quite easy for an adult male to exert a torque of 1000 ft-lbs with a steel bar that is 5 ft long (200 lb*5ft). That's more than twice the torque of a Z06. But that does NOT mean that a single adult male can generate 400 HP. Do you see why quoting only the torque is meaningless?

There is no right or wrong way to design an engine; every design has different design considerations. To get a lot of horsepower you can:
(1) Have huge displacement, like American muscle cars -- and suffer the consequences of adding a lot of weight, or,
(2) Design a small displacement engine and add forced induction (e.g, Evo, STi), or
(3) Design a small displacement engine to operate at high RPM (e.g. S2K).

 

or you can have a mid-sized engine and have it running very efficiently with good quality build and quality engine pieces i.e. m3. =)...or a highly modded vq35. heh

'03 G35c DG/G 6mt, full options
clear corners, tint, z-tube/popcharger,
nismo titanium shift ****