I do agree with you with the torque and powerband statement. While the 298-300hp G/Z 6MT is making more power than the 03/04 varients, that extra power is found above 6000rpms and there is less power from 2000-5000rpms. Very little time is spent accelerating from 6000-7000rpms in gear 1, 2, and 3. Not until speeds reach 90mph+ will the new motor start to stretch it's legs. The problem is, the 298hp-300hp motor might actually be slower from 0-60 which could impact it's overall 1/4 performance, ultimately whipping out it's power advantage up top. When you look at the dyno numbers, the 298-300hp motors don't seem to be making any more average power thru the powerband than the 03/04 motors. Power under the curve wins races, peak HP wins buyers.

As for the 260tq in the 298-300hp motor, I think that's a legit number, however I think most of us agree that the 260hp/260tq 03/04 G sedans are actually making closer to 270-275hp/270tq (ie underrated). Look at the dynos and 1/4 miles and the data suggests that the supposed 260hp motor is actually the same motor used in the 03/04 280hp coupe. 1/4 mile times seem to favor to the G sedans too. How can that be when it's supposedly 20hp and 10tq down on the 60lb heaveir coupe? I find it interesting that the 05 G sedan auto got a bump up in power, but the coupe's power held the same. To me it sounds like the G sedan auto just got rerated to more accurately reflect it's true power and to give buyers an incentitive that they're buying a more powerful car. I'm a firm believer that the 03/04 G sedan 6MT was making 280hp/270tq and that the new model is making an honest 10tq less.

This is just my opinion based on some data aquired thru this website, the mags, and what my 03 sedan auto runs at the track.

 

"The 05 automatic sedan gained 20hp and 10 ft lbs of torque- don't be surprised if the auto is faster in 0 to 60 and 1/4 mile than the 6MT car."

this may true, except that auto lose alot more power to the wheels compare to MT's (crank vs. wheel HP)

 

The auto seems to loose about 10-15whp and 10wtq compared to the 6MT. However, the auto has quite a bit more torque multiplication (torque converter) from 1000-3000rpms than the 6MT could ever hope to have.

 

When you are in a hurry the car doesn't spend any time in the 1000-3000 rpm range so the extra torque there isn't going to make much of a difference. M3s, Ferrari 360s and Acura NSXs all make disproportionately more horsepower than torque but none suffer in the accelleration department.
As far as the auto being faster 0-60 it was 3/10 or so slower when it had the same hp as the manual so that is pretty optimistic for 10 ft lbs of torque. I would expect maybe a 14.30 1/4 mile for the auto based on the previous incarnation.

 

I agree. The point is if you're barely rolling (1-5mph) in first in an auto and a 6MT and go WOT, the auto will flat out move and the 6MT won't move nearly as quickly until the rpms reach 4000rpms. This is because the torque converter slips and multiplys the engine torque A LOT. The 6MT on the otherhand has direct connection to the engine therefore there is a rather long bogging effect until the car gets near the start of the powerband. Launch a 6MT at 1500rpms and an auto at 1500rpms and the auto will jump out quite easily. Obviously the major advantage of the 6 speed is that you can launch at any rpm. This is why M3s, NSXs, etc do so well with their rather peaky powerbands. Keep in mind it requires a healthly higher rpm launch to get these cars to post good times. Launch an NSX at 2500rpms and it's not going to run nearly as well as it would launching at 5000rpms.

 

Personally I love it rip it up to 7200rpm shifts it sounds so sweet and does pull hard in the higher rpms. I wonder what rpm the variable intake kicks in at on the 2005 6spd?

 

You know... you always like to talk about "torque multiplication" (which is really a misnomer, but anyway...) of an auto tranny and it's torque converter.

What do you think slipping/feathering a clutch does on a manual tranny??? Same effect.

 

At the expense of the clutch! You can say a manual car has a variable torque converter called "the driver".

 

Taken from How Stuff Works (http://auto.howstuffworks.com/torque-converter.htm)

"......the torque converter actually gives your car more torque when you accelerate out of a stop. Modern torque converters can multiply the torque of the engine by two to three times. This effect only happens when the engine is turning much faster than the transmission."

Slipping your clutch is nothing similiar to what a torque converter is doing.

BTW, a transmission is also a torque multplying device. Auto or manual. If these devices didn't multiply the torque, these cars wouldn't be able to accelerate efficently.

 

"Modern torque converters can multiply the torque of the engine by two to three times."

The quote is definitely there Dave but I am fuzzy on what they are saying. Surely not that the a/t car temporarily has 5 or 6 hundred foot pounds of torque over and above what is done by the transmission gear multiplication? With a set of slicks the car should pull the front wheels off the ground. Or at least a 3 second 0-60 time rather than the 6.2 the car actually does. Whatever effect they are describing does seem to not translate into what cars actually do, as factory stock manual cars are pretty much always quicker than the a/t cars. Some of the magazines like Car and Driver also add 5-60 "Street Start" to their accelleration times and the a/t cars are almost always behind the same m/t cars that beat them 0-60 although admitedly not always to the same degree. This is true even with pretty sophisticated manuals like in the new Beemers. I will give you the 1 or 2mph roll because the manual would probably be stalling but any multiplication by the torque converter is probably only the engine rpms getting ahead of the output speed right before the torque converter locks up at 12 or 15 hundred rpm so it is only there for a split second. This last is just my theory to explain the How Stuff Works statement. I will ask the question of someone more knowledgable than I before I swear by it.

 

A 38hp increase through the whole powerband wouldn't be expected. Every improvement in this engine since the early Maxima variants hasn't led to a uniform power increase across the board. Just tweaks. The Anniversary and Track versions of the Z have 300hp and 260 tq compared to 287 and 274 in the base model. I don't think it was their intention to make the premium models slower. What would be the purpose? Presumably the cars were designed to be quicker rather than slower, and Nissan would have tested them at some point to see the actual results. When you race the car spends no time below 3000 rpm except for the launch so bottom range power isn't a big loss.
Having said all that, Dave's observation that the less impressive trap speeds of the 05 Z and m/t G might mean something if the further tests bear this out. I know Road and track tested the 287hp Z with trap speeds of 100.9 and 102.3 and the 03 a/t G with speeds of 93.4 and 97.1 so there is quite a bit of a range. The quickest mag time I have seen for the 287hp car was a 13.8 so this is kind of the number to beat. I expect the 05 will, reduced torque aside. but 13 hp is only good for maybe a tenth so any advantage won't show itself very often. I guess it will take 13.7 at 103 mph for the new Z to really prove itself, and a sub 14 time for the m/t G.

 

Slipping your clutch is EXTREMELY similiar to what a torque converter is doing. One uses friction and flywheel mass to transfer energy, one uses tranny fluid flow dynamics.

The only time a torque converter mutiplies torque is in a stall condition, when the engine is turning much faster than the transmission, basically at a standstill. The deceleration of the flywheel and engine as a clutch is engaged creates the same effect.

To quote "How Stuff Works" about the 2 to 3 times multiplication: "This effect only happens when the engine is turning much faster than the transmission." By much faster, meaning when the car is going 1 MPH and the engine is turning 2000 RPMs in first gear - which should equate to 10MPH or so...

If the torque converter really was mutiplying torque by that much all the time... the dyno graphs would show it. Right? But they're not...

If you want to say "torque multiplication"... then fine. But don't make it sound like auto trannies come with some magical torque fairy that aren't included with manual transmissions. Both trannies use this effect, either by a torque converter or friction clutch and flywheel.

Yes - technically, a torque converter CAN actually deliver more torque than is being input by the engine during certain situations, but this ONLY happens during stall conditions - such as launching from a standstill. And at a standstill, for most performance vehicles, more torque is not needed - the traction is the limiting factor.

 

yeah I agree with all of your points. Most things in life have to be a compromise of some kind and it's no different for wheels/tires. The 18's on mine are definitely as big as I would want to go knowing even they are sucking performance away from the car.

 

I'm 46 and couldn't have said it better myself. I'm also enjoying the threads and posts over here on the sedan side much more than some of the foolishness on the coupe forum.

 

I would have to agree with what you've stated above. Either way they're both allowing the engine to rev higher and then capturing a portion of that energy to the transmission utilizing the torque multiplication factor through gearing.