Originally Posted by chuck65
I agree, the automatic shouldn't get better milage than the stick because the stick is a direct drive system when it is cruising in 6th. gear. You can't get more efficient than that.
It has to be that the stick and automatic have different final drive ratio's. Does anyone have those numbers? It would be interesting to compare them.
The owners manual lists the stick in 6th. at 0.838 and the automatic in 5th. gear as 0.833.
I don't know what those numbers mean. I'm used to seeing rear end ratio like 4.11:1 and 3.80:1 etc. where the higher the number the higher the rpm will be at a given speed and the poorer the gas milage but it will give better acceleration performance.
What is the difference in RPM @ 60 MPH with the stick in 6th. , and @ 60MPH with the automatic in 5th? I think the automatic would be turning less RPM which would account for the higher mileage numbers.
I was trying to find this info, too, but I haven't come across a clear source. What I do know is that mileage dropped to 15/23 for the 2008 xFire manual, and you don't just lose MPG for no reason. It's likely to be a different axle ratio.
The numbers that you pulled are the top gear ratios. This isn't to be confused w/ the final drive ratio or axle ratio (rear end ratio). That's a ratio for the actual 5th/6th gear, not the rear end ratio we're used to seeing. IIRC, the rear end ratio for the SRT-6 is 3.08:1, I'm not sure what the N/A xFire's is, but I'm guessing it changed for 2008.
Also, I've heard that the xFire's torque converter never locks up completely, even when warm and in top gear. Is this true? It could be part of the reason for our ****-poor gas mileage.