YellowJacket

OK, so I am puzzled. For the most part, I have been using auto and DS but not manual mode until today.

Today I noticed after switching from 6th to 7th there was no change in RPM. I was doing about 50mph at the time. Traffic was heavy so I wasn't able to go faster. So, tomorrow I'll get out and stretch its legs a bit more to see if it happens at higher speeds.

I'm curious now because my gas mileage has not been that great (I know... its a sports car and power comes before MPG...) But on a recent trip from Knoxville to Nashville I was only able to get 24mpg.

09 G37x with 7at

Thanks

David

Black Betty

iTrader: (60)

There is a difference in RPM, even if its only slight. The only possible way it could be the same is if 6th and 7th gear in the transmission were exactly the same ratio. They're very close, but not the same.

YellowJacket

Thanks BB, yeah, the tach needle didn't budge at all while switching back and forth several times between the two gears.

David

Black Betty

iTrader: (60)

6th gear ratio is .86, 7th is .77. Not a lot of difference at all, but set your cruise and drive a long distance and it will get better mileage. May not feel different, but it will be just a tiny bit different.

GoCougs

6th gear @ 50 mph = 1818 rpm
7th gear @ 50 mph = 1628 rpm

So, less than 200 rpm difference, and at only 50 mph I wouldn't be surprised if the torque converter isn't locking, effectively resulting in nullifying the slight RPM differential (I see this too - I would be surprised that if left in D that the tranny doesn't even bother to shift into 7th at 50 mph).

I have a '11 G37x sedan, and the best highway I've ever done on a long trip was also 24 mpg (albeit 75 - 80 mph). The x is rated at 25 mpg highway; the (gamed and bogus) EPA highway cycle varies from ~35 mph to ~60 mph with an average of ~50 mph over about 10 minutes so in regular highway driving 24-25 mpg is about best you should see.

YellowJacket

So, I shoehorned my clubs into the trunk today and took the long way to the golf course....

At 60mph on the interstate the difference between 6th and 7th is about 250rpm.

Thanks guys very much for the feedback.

David

TVPostSound

iTrader: (9)

This ^^^^^