Uhg... why can't I edit my own posts on this forum????

 

Okay, so here's a few questions:

1- How did you determine the average dyno numbers for both cars? Where do the numbers come from? How many of each (coupe and sedan) did you use to make your "averages"?

2- How did you determine the drivetrain losses? I'm aware that between 15% and 20% are considered the norm. But are YOU aware that a dyno shop can do a coast-down test that will show the TRUE drivetrain losses? Do you have any of those numbers? In the interest of accuracy, we should have them before speculating any drivetrain losses. And consider this-- the heavier wheels/tires/brakes of a 6mt coupe will negatively affect the drivetrain losses. The sedan doesn't have this negative, regardless of transmission.

3- Where did your "observed" 1/4 mile times come from? Posts on this board? Road tests in magazines?

 

I think you misunderstood my post. I was just pointing out that the coupe is "listed" as a higher HP but it is also listed at that value at a higher RPM. drop it down to the same RPM and the HP "listing" on the coupe wont be as high.

I never said I was convinced or not... I was more trying to say that looking at the numbers reported by infinti really didnt mean anything (as i believe you agree on).

lastly, talking about the whole issue like this doesnt get us anywhere. Write a letter to the corporate engineers at nissan/infiniti and a few other competitors about the G35 sedan/coupe issue and see what they have to say.

playing with "averages" doesnt cut it.

lets use the values 217 for the sedan and 222 for the coupe. (5hp apart) take both constant values and look at them in the range of averages 20-22%.

217 / 0.8 = 271.25
217 / 0.78 = 278.2

222 / 0.8 = 277.5
222 / 0.78 = 284.6

within that average you coupe be comparing 271.25HP sedans against 284.6HP coupes. a 13.35HP difference.

now lets say nissan/infiniti calculated their horsepower values at the crank and took an average on several cars.... maybe the average values THEY came up with were the 260 and 280.

I am not trying to PROVE anything... just trying to point out that there is no reason in trying to justify the values they report UNLESS you know how they came to those figures.

I do understand the point you're trying to make so there is no point in trying to "prove me wrong".

I'm happy with my G and could care less whether a sedan or coupe pulled up next to me and had more horsepower or whatever... sedan/coupe both great cars.... I love both an always look to give a thumbs up.

Rock on!

 

Hitman brings up some good points.

man! this issue is almost as bad as the notorious MT/AT topic.

 

scobic, Good post... and I agree.

Truth of the matter is that the only possible way to resolve this question would be to yank engines out of a few coupes and sedans and run them on an engine dyno.

But we know that will never happen, right?

Until then, it's all speculation.

 

Peak HP and Torque is more for bragging rights then true performance. "Area Under the Curve" plays a significantly more important role.... the power throughout the power band gives you more of an accurate indicator. So comparing the cars solely on peak numbers is useless. While the cars are VERY similar, I'd be curious to see 2 dyno graphs done on stock cars on the same dyno for comparison.

My G is my daily driver. I play with my 1995 bolt-on Z28 which dynoed 280rwhp. I'm not much of a numbers guy... and the place where I got it dynoed is pretty conservative but the numbers are not too impressive... especially next to my LS1 brothers.... yet when I beat them down the track to get 13.2x's, nobodies thinking peak power.

I'd really like to see a show down b/w 5 Sedans and 5 Coupes...all stock... all Auto... all at the same track...to see a good comparison... This may be something that can be set up this summer.


2003.5 Silver G35 Sedan... my daily driver
1995 Camaro Z28 ... a few mods (13.27sec)

 

Hi,
As a mechanical engineer, the numbers from Nissan (HP and torque) are base on averages from some test and some calculations. They never write a number just considering tests if the number is not good and viceversa. Then, considering the average of phisical tests and calculation.

For Example:
Bore:84.14 mm
Stroke:80 mm
Displacement (D):3.56 l
Max. air/gas intake: m³/s
Air/gas ratio (stoichiometric): 1.1: 1.0
Max. gas intake: m³/s
The real gas intake is 0.0212 x f, in which
f = volumetric efficiency (%) of the engine and -is dependent on:
- rpm of the engine
- design of the air inlet manifold of the engine
- fouling of the air inlet manifold of the engine
At 1500 rpm, for a well designed and clean air inlet manifold f can be taken at 0.8 -
Therefore the real gas intake is: 0.0212 x 0.8 =30.017 m³/s
The heat value of the gas is taken at: 4800 kJ/m³
Therefore the thermal power in the gas is:

Pg = 0.017 x 4800 = 8-1.6 kJ/s = 81.6 kW

The engine efficiency depends partly on the engine's compression ratio. For a compression ratio of 9.5 : 1, the efficiency can be estimated at 28 percent.

Therefore the maximum mechanical output of this engine is:

PM max. = 81.6 x 0.28 = 22.85 kW

The maximum electrical output (cos phi generator = 0.8) is therefore:

PE max. = 22.85 x 0.8 = 18.3 kVA

A lot of numbers, taking from existing tables.
And the most important thing, if marketing likes the number... the better. For me, the sedan has about 270ponnies.

 

It's well known (heard many times on respected auto shows and in magazines) that many cars especially from the muscle car era were under reported to help sell them. They did so because it helped keep insurance rates lower and thus a fast car not as expensive.

Why not the same thing here, but from a marketing perspective. Is there a law about how hp is calculated and advertised? Do they have to calculate with all accessories (I believe in the past it was done without)? Certainly there can't be a law against under reporting, right?

As for "just the sedan people trying to justify". That logic can work both ways...Anyhow, it's also about knowing your vehicle the best you can. If the sedan is indeed under powered by 20hp, but shares the same engine and drivetrain then it should be easy with certain mods to get there. However, if they are VERY close stock, then why waste your money? Knowledge for the truth is all we are after.

Let's not make this a war. I think we all just want to know the facts here. Based on what I've seen it does seem to be odd that the sedan performs as well as it does on dyno and track.

If you still think sedan owners are trying to justify, maybe you should consider if you are the one trying to justify and keep thinking you are in some entire other class. We are all family here. Cheers! [img]/w3timages/icons/smile.gif[/img]

2003.5 Sedan Black/Black w/ sport, premium, aero, and winter packages. See my profile for updated mods list and pics.

 

I think that only those that have owned both and have a HIGHLY calibrated Butt dyno can truly tell.[img]/w3timages/icons/laugh.gif[/img]


Andrew, We Miss and Love You! Peace!

 

If the sedan really has more HP than what Infiniti suggests, and it weighs less than the coupe, and all else being equal, shouldn't we see the sedan consistently beat the coupe in straight line performance?

 

xswl: The short answer is no. That is because even if the sedans are underrated from the factory, and let's assume they are for arguments sake, their peak crank HP and TQ numbers would still not be higher than a coupes. It's probably closer to around 270+ than it is to 280. Also the weight difference is not that huge. In general it takes about 100 lbs. of lost weight to shave .1 seconds off the 1/4 mile time. You also have to consider other factors such as the coupes having wider wheels and tires for more grip. The basic message here in this thread is that the real world performance of stock coupes and sedans when compared in the same transmission and trim are closer than Infiniti would lead you to believe. How much closer would take a controlled scientific experiment to produce some results. Either way, both cars are great machines with great performance to back it up.

04' G35S 6MT Ivory Pearl, Willow, Premium

 

<blockquote><font class="small">In reply to:</font><hr>

If the sedan really has more HP than what Infiniti suggests, and it weighs less than the coupe, and all else being equal, shouldn't we see the sedan consistently beat the coupe in straight line performance?


<hr></blockquote>

There are a lot of variables that come into play. To really test both vehicles it has to be same tires/wheels, same track condition, both drivers should weigh the same, have to leave in auto mode w/ VDC Off, 60' time should be very close, ran 2-3 times then compare. What do you think the chances are to get both vehicles with the conditions I just listed?

True we cannot rely only on HP numbers, however, like I said in the beginning the above numbers came from members DYNOs and DYNO results come in combination of HP/TQ, power band and a/f ratio. As long as they SAE they pretty accurate, however temperature and humidity usually play major role in terms of getting higher or lower numbers (assuming the cars are stock).

Again, those 1/4 mile times came from members as well and they show that times are exact or close enough for both cars. Despite the fact ECU might be tuned differently plus exaust differences, sedan catches up in times probably due to weight advantage (kind of minimal) and actual engine specs are close enough regardless of original listing. In addition, the sedan comes with 17's vs the coupe with 18's. Larger wheels = heavier = more inertial losses = tougher to accelerate/brake so that works in favor of the sedan also.

I need dynos for coupe auto to analyze/compare, anyone please post it here?

Finally, guess what? Looks like the new 6th gen 04 Maxima cranking out a lot more power than it originally rated by Nissan at 265hp/255tq, and recent 1/4 mile times suggest more like the same 270+hp as the G35 sedan. Our member "specv" just got a new personal best of 14.4 @ 96 in his 04SE AUTO. Yes, auto and those magazines usually list 14.9-15.0. It's getting hurt just a tad on weight and the FWD launch, but otherwise it's right on the heels of the G35 autos both COUPE and SEDAN.

2004 G35s auto (bone stock)
-----------------------------------
2002 s/c Accord V6 auto
so far best 1/4 mile - 13.9@101.8
coming soon: custom internals, cams, performance auto tranny w/LSD

 

Also, it seems soon we will find out back to back DYNO results with 6mt sedan vs. 6mt coupe (both stock) here in Chicago. Then we go from there.

2004 G35s auto (bone stock)
-----------------------------------
2002 s/c Accord V6 auto
so far best 1/4 mile - 13.9@101.8
coming soon: custom internals, cams, performance auto tranny w/LSD

 

that back to back will involve me (if the other owner is into it, I'm still waiting on a responce.) I think we can overlap our dyno results to see more than just peak HP.

As to the purpose of this thread. I think it is only really valuble to three groups.
1. Coupe owners who are looking to stay ahead of the sedans by 'knowing thier enemy' so to speak.
2. Sedan owners trying to justify thier buy (the HP difference is the only reason i would possibly pick a coupe over the sedan*... this mindset was probably in the minds of the Infinity marketing division.)
3. Sedan owners trying to figure out how thier cars rate compared to the coupes, who can then theorize what the difference between the cars really is.

If the difference is 20+ crank HP, then the difference probably has to do with the ECU and timing. If its less, 5hp or so, then its probably just the exhaust. So this thread can have real value beyond bragging rights alone.

*-NOTE- this is not a slam on the coupe, i almost got one-for the same price as my sedan. But simply wanted 4 doors and a nice back seat.

 

Performance wise the sedan and the coupe are so close is it not even worth it to mention the 20 hp difference. I does seem like the Sedan owners are always trying to prove their car is as good or better, you don't see Coupe owners trying to do that. Both are great cars which is why MotoTrend made them both car of the year. The one thing the coupe has over the Sedan is that the coupe has the better looking body style.
Also if it were only about performance you could get a 12 second 1/4 mile SuperKart car for about $30k