Horrible Gas Millage
07-19-2010, 03:04 PM
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Horrible Gas Millage Well after I did the cam swap and all that good stuff. I dicided to see what millage I would get to a full tank since I never checked and I see most people get close to what GM says it should. So I fill up, reset trip milage and drive away. After driving both street and highway. Gauge light on. Its only at 178.xx . 
Thats not even close to what gm says just street. I'm thinking theirs something I can do. Any help would be apreciated.
Oh and the car was tuned about a month ago.
Thats not even close to what gm says just street. I'm thinking theirs something I can do. Any help would be apreciated.Oh and the car was tuned about a month ago.
07-19-2010, 03:23 PM
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Before I put my cam in, the best I got out of my car was 299.8. I wanted to see if I could get 300, but just missed it. But yeah, now it averages right at around 200. It sucks, but that's the price we must pay, my friend.
07-19-2010, 03:24 PM
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You are running the MS4, correct? Welcome to the world of crappy gas milage...
I have EFILive, and spent quite a bit of time getting the part throttle tune as close as I could when i had that cam. A/F ratio was always between 14.5-15.1:1 when cruising, usually dead on the nose at 14.7:1. I considered myself lucky if I baby footed highway miles and achieved 17mpg with an M6.
I truely believe those with huge cams and claim they are making 25+mpg simply don't calculate their milage correctly.
My only advice is if you have a 6 speed - don't assume that driving in 6th at 40mph will save you gas. Drive at an rpm where the engine feels responsive and not on the verge of bogging down
I have EFILive, and spent quite a bit of time getting the part throttle tune as close as I could when i had that cam. A/F ratio was always between 14.5-15.1:1 when cruising, usually dead on the nose at 14.7:1. I considered myself lucky if I baby footed highway miles and achieved 17mpg with an M6.
I truely believe those with huge cams and claim they are making 25+mpg simply don't calculate their milage correctly.
My only advice is if you have a 6 speed - don't assume that driving in 6th at 40mph will save you gas. Drive at an rpm where the engine feels responsive and not on the verge of bogging down
07-19-2010, 03:32 PM
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You are running the MS4, correct? Welcome to the world of crappy gas milage...
I have EFILive, and spent quite a bit of time getting the part throttle tune as close as I could when i had that cam. A/F ratio was always between 14.5-15.1:1 when cruising, usually dead on the nose at 14.7:1. I considered myself lucky if I baby footed highway miles and achieved 17mpg with an M6.
I truely believe those with huge cams and claim they are making 25+mpg simply don't calculate their milage correctly.
My only advice is if you have a 6 speed - don't assume that driving in 6th at 40mph will save you gas. Drive at an rpm where the engine feels responsive and not on the verge of bogging down
I have EFILive, and spent quite a bit of time getting the part throttle tune as close as I could when i had that cam. A/F ratio was always between 14.5-15.1:1 when cruising, usually dead on the nose at 14.7:1. I considered myself lucky if I baby footed highway miles and achieved 17mpg with an M6.
I truely believe those with huge cams and claim they are making 25+mpg simply don't calculate their milage correctly.
My only advice is if you have a 6 speed - don't assume that driving in 6th at 40mph will save you gas. Drive at an rpm where the engine feels responsive and not on the verge of bogging down
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08-09-2010, 05:51 PM
#9
You are running the MS4, correct? Welcome to the world of crappy gas milage...
I have EFILive, and spent quite a bit of time getting the part throttle tune as close as I could when i had that cam. A/F ratio was always between 14.5-15.1:1 when cruising, usually dead on the nose at 14.7:1. I considered myself lucky if I baby footed highway miles and achieved 17mpg with an M6.
I truely believe those with huge cams and claim they are making 25+mpg simply don't calculate their milage correctly.
My only advice is if you have a 6 speed - don't assume that driving in 6th at 40mph will save you gas. Drive at an rpm where the engine feels responsive and not on the verge of bogging down
I have EFILive, and spent quite a bit of time getting the part throttle tune as close as I could when i had that cam. A/F ratio was always between 14.5-15.1:1 when cruising, usually dead on the nose at 14.7:1. I considered myself lucky if I baby footed highway miles and achieved 17mpg with an M6.
I truely believe those with huge cams and claim they are making 25+mpg simply don't calculate their milage correctly.
My only advice is if you have a 6 speed - don't assume that driving in 6th at 40mph will save you gas. Drive at an rpm where the engine feels responsive and not on the verge of bogging down
08-09-2010, 06:27 PM
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I was able to get 24-27mpg highway nursing it with a t-rex in a 939ci motor (m6). I switched to a smaller cam (228-235) and my fuel mileage went down to 18-20. I believe that this is due to the volumetric efficiency of each cam. IE the smaller cam has a higher ve at lower rpm than the did the bigger cam. Higher ve means more airflow thus more fuel required to be stoich.
Many things go into fuel mileage, but to keep it simple (because I am not educated enough to go into depth), engine efficiency is the key. And that all goes into the combo. An MS4 might make better MPG with a set of TFS 235s and a Super Vic then a smaller cam. However, that same "smaller cam" could make much better MPG with a set of 243s and LS6 intake then the same set up with an MS4.
Generally speaking however, a smaller cam with less duration and wider LSA will be better for fuel economy.
08-23-2010, 06:21 PM
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From my calculations I wouldnt even get passed 20 on highway and maybe 13-14 on st. I think the tune might have to do something with it as well. Might have to retune on partial throttle.
09-11-2010, 04:54 PM
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That is incorrect. Airflow, from a normal driving perspective, is determined by the throttle body....that is how far open or closed it is.
Many things go into fuel mileage, but to keep it simple (because I am not educated enough to go into depth), engine efficiency is the key. And that all goes into the combo. An MS4 might make better MPG with a set of TFS 235s and a Super Vic then a smaller cam. However, that same "smaller cam" could make much better MPG with a set of 243s and LS6 intake then the same set up with an MS4.
Generally speaking however, a smaller cam with less duration and wider LSA will be better for fuel economy.
Many things go into fuel mileage, but to keep it simple (because I am not educated enough to go into depth), engine efficiency is the key. And that all goes into the combo. An MS4 might make better MPG with a set of TFS 235s and a Super Vic then a smaller cam. However, that same "smaller cam" could make much better MPG with a set of 243s and LS6 intake then the same set up with an MS4.
Generally speaking however, a smaller cam with less duration and wider LSA will be better for fuel economy.
