Had my "G" machine for 1.5 mos. (2400 miles) now, and I'm bothered by the (relatively) high RPMs we are spinning in top gear. Seems like gas mileage is an issue with our cars, so why the low gearing?

04/2004 Motor Trend shows the '04 Acura TL 5AT spinning 1750 RPM @ 60 MPH (with 3.2 liters) and even the '04 Saab g3 Aero 5AT spinning 2000 R's @ 60 MPH (with a MUCH smaller, though turbocharged, 2.0 liters!), while the '04 5AT G35 Sedan is revving 2250 RPMs @ 60 MPH - Why ?? We have larger engines with more torque in cars weighing within 100 lbs. of the competitors - surely we can pull the taller gearing in the final drive that will allow us the gas mileage we'd like on long (or cross country) runs??

Don't get me wrong - I love this car and will be keeping it for 6-8 years and 150,000 miles (if past history is my guide), it just seems we could get noticeably better mileage with a taller final drive ratio without sacrificing much acceleration, if any at all, and get the added bonus of less wear and tear of the engine, too! In my 6MT (which also spins 2250 RPM @ 60 MPH), 1st gear is nearly a granny gear anyway, so a taller final drive ratio couldn't hurt acceleration (or "launch") much. The car is such a torque monster that I normally start in 2nd and go 4th to 6th in everyday (suburban) driving - why row through all the gears when traffic won't let me accelerate any faster, anyway? - and I think an extra 500 RPM dropoff at shifts in the upper gears would not be noticed much under WOT, as you're still in the fat part of the torque band - but would result in much better mileage, especially on freeways and long trips, plus less wear.

I read the thread about the killer posi unit Quaife is considering developing for our "G" Machines - maybe that, stuffed with taller gears (say, a 2.30-2.40 final drive instead of the 2.80 we have) would make my RPM/Gas Mileage/Unnecessary Wear concerns disappear (and some of my gas money reappear!).

This is just IMHO - what's yours ??

Sport Sedan Fan
2004 6MT Sedan/Sport/Navigation/Premium/Aero

 

You might have a point, but too much gearing will really kill the passing acceleration. Id hate to have to drop from 6 to 5 everytime I wanted to overtake. However now that my car has about 10k on it the gas consumption is much improved - the first few months were brutal, I was sucking more gas then my friends Explorer SUV.

 

Thanks, Colin - maybe I'll feel better if/when she stops sucking the fuel like she is now. It's early in the game, and the VQ is supposed to be a "bullet proof" engine, so maybe the extra revs aren't so important in the long run, as long as the mileage is at least decent after awhile (22-24 @ 80-85 MPH on road trips would be nice).

Sport Sedan Fan
2004 6MT Sedan/Sport/Navigation/Premium/Aero

 

What mileage are you getting? I went from DC to NYC a couple of weeks back (NY Auto Show) and got 23.5 on the drive home, running 80-85 all the way. Even local highway driving (with some local traffic) gets me about 21-22. And this is with an auto.

My daily commute, which is pretty bad out here, get around 19

G35S AT / Ivory Pearl and Black

 

Mileage I'm getting right now is about 15 in city/suburban stoplight traffic and about 20 on the open road - and I'm babying this car! I'm encouraged by the prior post that says the mileage improves after 10,000 miles or so - I'm banking on that. But either way, even if the car got 25 MPG @ 80-85 MPH, that just means it would be getting 27-28 MPG @ 80-85 MPH with more taller/more appropriate gearing. Again, I'm not knocking the car - which I love - but there are almost NO cars out there that are revving 2250 RPM in top gear @ 60 MPH - regardless of size or class - so why are we? (and wasting gas $ and adding wear, etc., etc.).

Sport Sedan Fan
2004 6MT Sedan/Sport/Navigation/Premium/Aero

 

last week, i filled up, drove about a 100 miles 90 percent highway and got 27.5 MPG. grrreat huh! but usually on a full tank measured by dividing miles driven by gallons filled, i max out at 20 mpg and average 19.5 mpg. (btw, this is with babying it and driving like a grandma). MPG fr me used to be average 16-17 mpg with semi-lead foot.

G35S 6MT / ts ecu / 350z springs & struts / jwt popcharger + z-tube / stillen dual exhaust / 6-wire ground kit / soon: kinetix high flow / ssr intake manifold

 

I just took a trip from Virginia to Dallas and back averaging about 27 mpg. My car was fully loaded with my wife and 2 kids and the trunk full of luggage and stuff. I maintained about 70 mph the whole way. I was very impressed considering that my car is not front wheel drive and weighed down with stuff. One leg of the trip I went 505 miles nonstop and put in just over 17 gal. Yes, fuel light came on. With a 20 gallon gas tank, I probably could have gone another 50 miles.

 

SixgearSedan,

WOW! I've never heard of anyone getting 29+ mpg! Most people are getting 24-25, at best.

For the rest of you, please be aware that if you are getting your mpg numbers from a nav system, you should be aware that the nav system reports mpg that is ~8% higher than actual. I don't know why they can't fix this, but it is a well known bug. All it would take is to change a multiplier. GAK!

Scott

 

Daoes anyone know the sedan rear end gear ratio automatic versus sedan?

 

I should look at my post before I submit it. What I meant to say is automatic vs. manual

 

I got 23-24 during my long trip at 80-85 mph and in city with lot of stop and go i get 16-16.5. My car has 1750 miles now

 

What RPM's @ 60 mph are people with the automatic '05s seeing? I'm wondering if it's been lowered from 2,250rpm's with the revised tranny.

 

what RPM does ppl shift in 6MT?
i find out that shifting at 4000 is the best

 

I'm around 2200-2500 unless I need a little more acceleration.

 

I would say we have pretty well set up ratios. It could be slightly taller gearing for better fuel economy but it could also have gone the other way. I'm not sure I would agree with your statement almost no other cars revving 2250 @60. In fact my experience is most are revving higher unless they are larger displacement. Even my V8 Grand Cherokee is 2200 at 60.
The Mazda MX6 V6 I came from was revving 3000 @ 60mph so this seems low to me. Our Sunfire is at 2400 at 60 and a friends outback is at 2800.
If it was up to me I would have changed 6th in our cars to more of an overdrive revving about 2000 at 60 but I still like it the way it is.