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Having owned three GM cars with a 6sp manual, it is reasonable to expect a similar experience with my CTS-V. The first five forward gears are power gears, and 6th is overdrive for good fuel mileage on the highway.

Much to my chagrin, I have learned that I have to go 51 MPH to get the same mileage as my (C5) Z06 going 75 MPH. This is really not good, as I expected I would use the -V for the long trips.

It looks like I'm going to have to swap the 3.73:1 in the 6M with the 3.23:1 in the 6A.

Anyone auto owners who like to drag race want to swap with me? [half kidding]
 

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09 Silver V 06 Silver Z06
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yeah that is sorta like the 6th gear in my 2004 audi s4, not really even what you could call an over drive gear they way they have it.
 

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Tis Gone :(
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The V weighs a hell of a lot more and doesnt have the aerodynamics of a C5.

4th gear should be your 1:1 and 5th and 6th both overdriven.
 

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Discussion Starter #4
The V weighs a hell of a lot more and doesnt have the aerodynamics of a C5.

4th gear should be your 1:1 and 5th and 6th both overdriven.
I know the drag coefficient is lower on the CTS, but the weight of the vehicle is irrelevant for highway mileage. 4th is certainly 1:1, but the 0.63:1 for 6th combined with the 3.73:1 makes for an unreasonable 2000 RPM at 68 MPH.

I believe the ratios in the 6M are the same as the ZR-1, supposedly to handle the torque output of the motor. If 6th were 0.55:1 or even lower, we could have all avoided the Gas Guzzler tax.
 

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2013 6MT V wagon, OBM, 2009 silver V sedan (traded)
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Having owned three GM cars with a 6sp manual, it is reasonable to expect a similar experience with my CTS-V. The first five forward gears are power gears, and 6th is overdrive for good fuel mileage on the highway.

Much to my chagrin, I have learned that I have to go 51 MPH to get the same mileage as my (C5) Z06 going 75 MPH. This is really not good, as I expected I would use the -V for the long trips.

It looks like I'm going to have to swap the 3.73:1 in the 6M with the 3.23:1 in the 6A.

Anyone auto owners who like to drag race want to swap with me? [half kidding]
We have the same problem in the autos. At 70 mph the engine is spinning in the neighborhood of 2k rpm (will look again while I'm driving today to be sure). I'm reconciled to driving the wife's Pilot for our long family trips, was really hoping to use the V occasionally for that (hate driving SUVs)...23 mpg freeway never looked so good.

Then again, I didn't buy this car for the mileage. :)
 

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2011 CTS-V Coupe (Auto)
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Ok, I am going to take a stab at this in four words.... Acceleration and Top Speed. I would guess that the ratios were chosen for the best mix of acceleration/top speed while still getting reasonable fuel economy. My 2006 V1 had a 0.56:1 6th gear and would top out at 163mph. at redline in 5th and maintain that speed in 6th. The gearing was too tall to allow the car to A) reach the majority of the power band, and B) the reduction of torque (function of HP) was too much for the car to accelerate past 163mph. With shorter gearing about 180 mph should have been reachable.

I would also assume that the ratios were selected based off the wide range of cars that it would be fitted to. From the Corvette ZR-1 to the CTS-V and even the Camaro SS if I recall correctly. All with different power bands, and power outputs.

Now I realize that few if any 6M owners will ever get to run their cars out to the 192+mph top speed that these cars can do. But I would guess that if the cars where limited to say 180mph because of taller gearing (0.55:1 or lower) they would be about as upset as not getting to cruise at 1600rpm at 70mph all day long. That is one of the big selling points of the 6M, one that I seriously had to think about before I went for the 6A. I am limited to 178mph at the top of 5th, but then again I have different ratios.

I hope this might shed some light on the subject. I am not sure why no one has mentioned it before, I guess its one of those things where you don't see the forest for the trees.

BTW: I don't mean to offend anyone with this post, and there is always the chance I could be dead wrong.
 

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2018 CT6E, old: 2014 XTS Vsport, 2005 CTS-V, 2004 CTS-V.
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Aside from getting a tune which might chance in voiding warranty, tire pressures and driving style are your only short term solutions.

I have a 3.42 in my V1 which is also lighter than stock and ProCharged. It's apples to oranges comparison to the V2 so I will not delve into the intricacies but the lower ratio differential does play a roll in economy to about 300 rpms difference in teh 3.73. The LS1/6 are most effcient around 1300-1400 rpms.

Norm
 

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2009 CTS-V
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What about the possibility that, in addition to gearing, the parasitic loss from the supercharger is contributing to the milieage (for both the ZR1 and the V2)?
 

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09 CTS-V, Radiant silver, Loaded, Auto
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crap, that's a difference. In my WS6 I do 80 at 2k. It gets pretty decent mileage too. Getting ready to take the drive to order my V.
 

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2009 CTS-V, 2009 535i
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The auto reportedly hits its top speed of 175 in 5th, so 6th could be taller and not affect top speed or acceleration. Another forum member that has connections mentioned it has something to do with the car's mass. This sounds reasonable to me because even at speed, the car's mass creates inertia that has to be overcome. I would guess that the auto would keep hunting in and out of a taller 6th at cruising speeds and irritate us in a different way. Okay, so why isn't the manual's 6th taller? I don't know...could it be that with the boost/mass/drag combo you might actually be "lugging" the engine at too low of an RPM? Drone?
 

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2011 CTS-V Coupe (Auto)
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What about the possibility that, in addition to gearing, the parasitic loss from the supercharger is contributing to the milieage (for both the ZR1 and the V2)?
Good point, I would think that would also be a contributing factor, perhaps wait4me could share any info he has on the efficiency of the supercharger, during cruise and accel.
 

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2014 AWD 2.0 Obsession Red --Black 2007 STS-V
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We have the same problem in the autos. At 70 mph the engine is spinning in the neighborhood of 2k rpm (will look again while I'm driving today to be sure). I'm reconciled to driving the wife's Pilot for our long family trips, was really hoping to use the V occasionally for that (hate driving SUVs)...23 mpg freeway never looked so good.

Then again, I didn't buy this car for the mileage. :)
:histeric:
Driving a $65,000 car , but can't bring yourself to pay an extra 5 cents a mile to drive it ?:thepan:
1700 mile trip would only cost you an extra $ 85 , based on 17 mpg of Premium vs 23 mpg low oct fuel.
You already lost $10,000 when you drove off the lot, go ahead ,drive it , enjoy the comfort and power .:bouncy:
 

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My God, I just don't get it.

You're whining about 2000RPM at 70mph? That's a very tall gear. Okay, not as tall as maybe some 'Vettes can pull, but that's still a very tall gear.

I just can't believe people are whining about this. At this point you have no evidence that spinning the engine 150RPM slower at that speed is going to result in better mileage.

GM had to meet certain competitive targets for top-gear acceleration and driveability and they picked a gear ratio that'd accomplish that. My guess is that if you swapped a taller gear you'd be whining about 60mph-in-sixth throttle response. What will you give up to gain 1mpg?
 

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2011 GTR
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Anyone auto owners who like to drag race want to swap with me? [half kidding]
I'd be all over it if you lived close...

Stock these cars run way too rich and waste a lot of fuel. Think about getting a tune, and not only will you get more power, but better gas mileage. In my C6 Z06, after a tune I could get close to 30mpg on the highway.... that was amazing.

Mark
 
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