11-12 mpgs mixed w/ 2 different cams and heads..why?
03-06-2006, 08:23 AM
#1
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11-12 mpgs mixed w/ 2 different cams and heads..why? My car has been getting shitty mpg's for quite some time. I expected to lose some, but not this much. I used to have a full-bolt on cam only (f10 114) and stock injectors (26#) and stock 853 casting heads. Now I have stock ls6 heads, svo 42# injectors and the f13 112 and am still getting the same mpg's, not to mention now i have an oil comsumption issues that ive never had. could it be that my motor is going or is bad? The tune is a little lean, but not enough to cause that. any thoughts on what it could be?
03-06-2006, 06:54 PM
#4
What kind of driving do you do (hwy/city mix)?
I don't have a cam but I do have LTs and 4.10s behind an M6. My daily commute is 80% city, 20% hwy and sometimes the hwy portion is <40 mph due to traffic. When I first installed the headers I was averaging 13-14 mpg. I track my mileage on an excel spreadsheet and after 4 months I noticed my mpg was getting worse, averaging 11-12 mpg. I noticed on my hpt logs that my O2s were starting to look "sleepy" and extended idling in traffic would cause my fuel trims to skew positive. Keep in mind that I didn't have any dtcs set yet. I just finished off my first full tank of gas after installing some C5 rear O2s (Bosch 13111s) and I averaged 15 mpg.
I would go back and take a look at your O2s and see if they are still oscillating well.
I don't have a cam but I do have LTs and 4.10s behind an M6. My daily commute is 80% city, 20% hwy and sometimes the hwy portion is <40 mph due to traffic. When I first installed the headers I was averaging 13-14 mpg. I track my mileage on an excel spreadsheet and after 4 months I noticed my mpg was getting worse, averaging 11-12 mpg. I noticed on my hpt logs that my O2s were starting to look "sleepy" and extended idling in traffic would cause my fuel trims to skew positive. Keep in mind that I didn't have any dtcs set yet. I just finished off my first full tank of gas after installing some C5 rear O2s (Bosch 13111s) and I averaged 15 mpg.
I would go back and take a look at your O2s and see if they are still oscillating well.
03-06-2006, 07:16 PM
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Too much injector??
My M6 stock geared car is getting 15.5 MPG as of today. 402ci, 42# inj, 248/254 TSP, stage III LS6 heads, FAST 90/90. Decently hard driving and a base break-in tune. Around town.
My M6 stock geared car is getting 15.5 MPG as of today. 402ci, 42# inj, 248/254 TSP, stage III LS6 heads, FAST 90/90. Decently hard driving and a base break-in tune. Around town.
03-06-2006, 07:56 PM
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if you did not get the injectors rescaled then you are running rich as hell. For me I would make sure they are scaled correctly and then after that have someone data log the motor in traffic. If things are running rich enough plugs are prob shot.
03-07-2006, 12:48 AM
#7
Originally Posted by ninobrn99
The tune is a little lean
Ninobrn99, are you tuning with a wb or off of fuel trims? If you are using a wb, you could go open loop and see if your mpg improves w/o any fuel trimming....
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03-07-2006, 03:33 AM
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i did scale the injectors. i could accept the injectors as the reason if i did not have the same issue with the stock 26# ones. i just replaced the o2s and still the same thing. i have been tuning via trims and i do have a lc1, but was waiting for tuners to come out with the usb eio so i could upgrade, but i wont be able to do that till august anyways. Its more city than anything, but when i try out more hwy, i avg about 2-3 mpgs better...maybe. i also have 3.90 gears since i just installed a 9" but i dont see them being an issue at the moment. I dont know if its the motor itself or something else. i havent changed the fuel filter, but would that cause that big of a drop?
03-07-2006, 03:49 AM
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i guess i should also mention that the car feels very weak down low. even when im in the cams powerband, it feels like it takes forever for the rpms to climb.
03-07-2006, 04:55 AM
#10
Originally Posted by Mr. Luos
Too much injector??
My M6 stock geared car is getting 15.5 MPG as of today. 402ci, 42# inj, 248/254 TSP, stage III LS6 heads, FAST 90/90. Decently hard driving and a base break-in tune. Around town.
My M6 stock geared car is getting 15.5 MPG as of today. 402ci, 42# inj, 248/254 TSP, stage III LS6 heads, FAST 90/90. Decently hard driving and a base break-in tune. Around town.
03-07-2006, 07:30 AM
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I'm having the same issue as you are. I'm getting about 10mpg in the city and about 17mpg on the highway. 
I however am still on 28# injectors which may be some are sticking open. I won't know until this weekend. If I find out that they are ok, that will lead me to believe that it has to be a tuning issue.
I however am still on 28# injectors which may be some are sticking open. I won't know until this weekend. If I find out that they are ok, that will lead me to believe that it has to be a tuning issue.