Adding 3:90 gears
Tech Contributor
Joined: Jul 2002
Posts: 14,949
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From: St. Louis, MO
St. Jude Donor '08
I can provide you with screen shots of the rev limiter if you need them, or you can search for my thread on the topic (I don't have it bookmarked on my iphone where I am posting from)
Thread Starter
Drifting
Joined: Feb 2006
Posts: 1,531
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From: Deerfield Beach FL
The reason I asked is that my mileage has taken a nosedive. Around town with a little interstate I average 14.6 mpg with the 3.90's and 6MZ. On a trip to Dallas and back I averaged just over 23 mpg. These numbers are far below what I expected. Tune by Chuck CoW should have helped by leaning it out some, but mileage s***s.
Race Director
Joined: Oct 2005
Posts: 14,999
Likes: 200
From: Bay Area Ca.
I thought about gears but I really love the mileage I get.
I have hot footed around with other vehicles, at this time I am happy with the tuned LS3.
For me the loss of mileage is a killer.
I have hot footed around with other vehicles, at this time I am happy with the tuned LS3.
For me the loss of mileage is a killer.
Team Owner
Joined: Mar 2005
Posts: 20,933
Likes: 905
From: salem OR
The reason I asked is that my mileage has taken a nosedive. Around town with a little interstate I average 14.6 mpg with the 3.90's and 6MZ. On a trip to Dallas and back I averaged just over 23 mpg. These numbers are far below what I expected. Tune by Chuck CoW should have helped by leaning it out some, but mileage s***s.
My mileage hits 30 straight hwy, with a little in town mix 25.8 ave last tank. I have 3.90's with the base tranny so my 6th is where yours was.1.95 vs 1.94 6th ratio's
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Pro
Joined: Jul 2006
Posts: 608
Likes: 1
From: LZ IL
speedo input comes from diff but from input shaft not output to wheels.
I have 3:90 and there was no negative change in gas mileage. I can use 6th gear more around town than before. On a resent 250 mile trip I averaged 32 mpg at 75 mph
I have 3:90 and there was no negative change in gas mileage. I can use 6th gear more around town than before. On a resent 250 mile trip I averaged 32 mpg at 75 mph
Tech Contributor
Joined: Jul 2002
Posts: 14,949
Likes: 263
From: St. Louis, MO
St. Jude Donor '08
I have a spreadsheet tracking every gallon of gas used in my car since I bought it 20+k miles ago.
The 3.90's and headers were put on at the same time and I lost 1.0 mpg. The cam was put in a year later and I lost 1.82 mpg from the cam.
I still get highway runs > 20mpg but if I drive in stop and go traffic I've had tanks go as low at 16 mpg.
Before mods average MPG was 19.95 overall
After gears & headers 18.94 mpg overall
After cam 17.12 mpg overall
Most of my daily drive is city with 6 miles highway. Hope that data helps.
The 3.90's and headers were put on at the same time and I lost 1.0 mpg. The cam was put in a year later and I lost 1.82 mpg from the cam.
I still get highway runs > 20mpg but if I drive in stop and go traffic I've had tanks go as low at 16 mpg.
Before mods average MPG was 19.95 overall
After gears & headers 18.94 mpg overall
After cam 17.12 mpg overall
Most of my daily drive is city with 6 miles highway. Hope that data helps.
Former Vendor
Joined: Nov 2005
Posts: 11,792
Likes: 255
From: Ossining New York
St. Jude Donor '07-'08-'09-'10-'12-'13-'14
Funny thing is.......
The reason I asked is that my mileage has taken a nosedive. Around town with a little interstate I average 14.6 mpg with the 3.90's and 6MZ. On a trip to Dallas and back I averaged just over 23 mpg. These numbers are far below what I expected. Tune by Chuck CoW should have helped by leaning it out some, but mileage s***s.
Chuck CoW
Thread Starter
Drifting
Joined: Feb 2006
Posts: 1,531
Likes: 0
From: Deerfield Beach FL
Must be the GT-11 cam then. I really don't get into it that often to knock down the around town mileage to < 15 mpg.
Thanks, Joe for letting me know others have seen the drop.
Thanks, Joe for letting me know others have seen the drop.
Tech Contributor
Joined: Jul 2002
Posts: 14,949
Likes: 263
From: St. Louis, MO
St. Jude Donor '08
Mike, pm my buddy Rwsjr. He has your exact cam, and I don't think he has any mpg issues. I am concerned that you have something else going in. Do you have hp tuners and thus can you scan your car?
Burning Brakes
Joined: Nov 2004
Posts: 848
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From: St. Louis Mo.
Pro
Joined: Oct 2004
Posts: 546
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From: CA
2nd Gear
Joined: Dec 2005
Posts: 2
Likes: 0
Someone needs to help me to I have the GT-11 and mine is around 16 as well. FAST intake,Kooks 1 3/4 with cats,Borlas, LPE cold air, Dart 225heads, 6-speed, some minor tuning. I had to have alot of fuel down low (650-2000 rpm)to even out fuel trims. The car would set mil light almost instantly with a lean right and left bank. Car gets same mileage before and after needs something else changed.
Thread Starter
Drifting
Joined: Feb 2006
Posts: 1,531
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From: Deerfield Beach FL