I was hoping someone could tell me the major differences in the engines between 260 and 298 horsepower with the 04 and 05 respectively. What are we talking about? hotter cams, ECU, and is there something we can do to raise the 04 motor to this level?

 

IMO, they just rated the sedan auto 03-04 260hp motor at what it's really putting out, 280hp. Nissan did this years when the 02 Maxima and 02 Altima were introduced. The Maxima was rated at 255hp and the Altima was rated 240hp though the motors looked identical. On the dyno they put out exactly the same power. It's the same thing we're seeing with the 03/04 sedans and 03/04 coupes......same power on the dyno. The 298hp motors are different. I believe they have a slightly different cam and a stronger valve train because I believe these motor redline at 7000rpms. HOWEVER, these motors sacrafice torque for HP. When you do that you take one step forward and one step back so you're bascially where you started. IMO, the 298hp motor is simply for bragging rights and these cars won't be much quicker, if at all, than the 280-287hp motors.

 

If you look at hte RPM redline figures, you'll see the '05 slightly higher than the '04. Since hp is derived from torque and RPMs, that little bit of RPM increase in the '05 will yield higher hp figures. The other upgrade is changing some of the internal components (not design, but materials) as well as a updated fuel map. Same engine, just more refinements.

 

So what you are saying is the 03-04 at really producing 280 instead of the listed 260?

 

I am certain that the sedan and coupe produce the same horspower. A coupe auto will produce the same rwhp as the sedan auto and the same for the 6MT's. As many dynos on the threads here and at my350z.com have shown. I'm curious if my 05 sedan 6mt will actually produce more than an 04 6mt (sedan or coupe). Supposedly the hp has been increased and torque lowered. We will see.

 

Its all marketing.... Look at the anniversary 350z, 300 hp, but produces less torque and has higher RPM, hmm just like the G35's new cars.... My conspiercy therory is the annivesary 350z, G35 coupe and Sedan with 6MT all produce the same HP, they just want it to look like the 350z puts out a few more HP to make it look like the sports car of the line up.... Nissan is just playing mind tricks...

 

I doubt there's much difference at all......just fuel mapping, maybe timing, minor stuff.
You may see some extra ponies at a narrow rpm band prolly up high.
You might also see a sacrifice of torque too in the new engines to get the extra hp.
I don't think there's much difference in any of the VQ engines whether it's the Altima, Maxima, or the G's. JMHO

 

Horsepower is derrived from RPM and torque but increasing RPMs doesn't necessarily raise the HP. That is only true if the HP peak and redline occur at the same engine speed. If you look at a dyno chart you can see that HP tends to peak before redline. Therefore increasing the redline alone will not increase HP.

 

So what are the 04s putting out at the crank?

 

04's = Variable intake cam phasing

05's = Variable intake cam phasing PLUS Variable exhaust cam phasing

 

At first I thought it was BS, but now that I've been driving my car a bit more, I notice a difference between the 260sedan and my 298 sedan. I guess in 500 more miles, I'll race my cousins AT coupe and see how much these cars improved.

 

"04's = Variable intake cam phasing
05's = Variable intake cam phasing PLUS Variable exhaust cam phasing"

This is my understanding as well.....this and the additional RPMs.

Note that Technosquare (ecu guys) ups the redline to 7100 RPM (stock 6600 RPM) in order to take advantage of top end horsepower.

 

So what are the real horse power numbers for the 04s?

 

I shoud have been more clear with my statement about sacrificing torque for HP. Yes, HP is derived from torque at a given rpm. What is happening with the 298hp motors is that the cam profile is different. This increases upper rpm power, but it sacrifices low rpm power. A higher torque number is made in the upper rpms hence you get a higher HP number, however in the lower rpms torque is lost therefore you get a motor with a softer lowend punch, more prone to bogging, and needs to be driven harder to the get the most performance out of it.

*Longwinded, but interesting*
Loosing power in the midrange to gain power in the topend isn't always a good thing. A prime example was my Maxima. Back in 2001 we discovered there was an intake manifold used in Japan/Middleast that had a variable intake runner design acutated by butterlfy valves. The stock intake manifold made peak HP at 5600rpms and then power dropped like an anvil. This new variable intake manifold (VIM) made peak power at 6200rpms and held the power straight to fuel cut (6500rpms). There was price to running this VIM though. The way it was designed sacrificed some midrange power and I had no idea how significant that was. With the stock intake manifold, my car made 183fwhp@5600rpms and 193fwtq@4400rpms. With the VIM my car made 189fwhp@6200rpms and 184fwtq@4800rpms. With the VIM, from 5800rpms to 6500rpms my car anywhere from 10 to 45whp/wtq more than the stock intake manifold. I thought it was a total win situation. My car lacked the lowend punch it had, but it pulled hard all the way to fuel cut. However when I got to the track, the truth was revealed. Under the same conditions, I was getting 14.6s@96mph just like I did with the stock intake manifold. Other guys were reporting the same results. How could this be? My car was making significantly more power now with just a small drop in low/mid range power. The problem was the lower midrange power, the lack of proper gearing, and the 6500rpms limiter. On every gear change, my car was entering into a powerband that was a bit lower and not until the upper rpms did the car equal out what it lost down low. The addition of topend equaled out the loose of power down low basically making it a wash. We soon realized that a 7000rpm limiter was needed for ideal shiftpoints and JWT had it. We ordered out JWT ECUs with 7000rpms limiters. The ECUs also had better programming which increased midrange power by about 8-10whp/wtq which means it cam close to restoring our lost midrange power. With just the addition of the JWT ECU, my car went from 14.6-14.7@96mph to 14.3-14.4@99mph+. WHP/WTQ went to 200whp@6200rpms and 195wtq@4800rpms.

That right there shows you how significant midrange power is, proper gearing, and the right rev limiter is. I learned that most of your accelerating is spent in the midrange and very little of it is spent in the higher rpms.

With all that said, this is why I don't think the 298hp motors are going to be much or any quicker than the 280hp motors. The gain isn't that significant and they've traded approximately 10tq for 11-18hp spread over 600rpms in the topend. Maybe above 110mph the power could be put to use because of the gearing, but below that the gains will be questionable.

 

the new engines may have less total torque but they have more usually torque... so it works out to about the same i suppose... they arent going to up the cost of a car and do a bunch of unnessesary changes to make a car slower...