i hardly ever use a/c because of that. and if i do its only on the freeway, and i cruise at 65-70. which setting is better, max or regular? i heard max was more efficient, but which one uses more gas? what kind of tune would you recomend with the different settings? and are they switch on the fly? thanks for everyones help.
bad gas milage, please help
- Thread starter gotchopsticks
- Start date
forpit2000gt
Founding Member
max setting just doesn't pull air from outside, once ac is on the max setting doesn't matter. Defrost setting tuses the compressor the sam as ac max or regular.gotchopsticks said:
jstreet0204
Active Member
gotchopsticks said:
First of all, the tune you have likely only has changes for WOT parameters. Meaning the tune has all of the stock settings except for when you floor it. If you keep your foot out of it the tune should not make a difference. This is the way probably 95% of the people out there with a tune are set up. Now, you can have tune set up that can improve gas mileage by adding timing in the lower load rows of the timing tables. As far as "it takes more fuel to make more power" that someone said, this is true but if you aren't dirving it hard all the time, the most of your gas mileage is going to come from closed loop operation, where the car is always shooting for an a/f ratio of 14.64 to 1. Most tuners would never change that, so I would look somewhere other than the tune. Tire pressure, air filter, o2 sensors etc.
jstreet0204
Active Member
gotchopsticks said:
Because I know what tables, scalars and functions are changes in most performace tunes. if you are only getting close to 20 you increase a whopping 2 mpg increase, could have been bad gas before. 20 still insnt that high. I generally get between 240 and 260 gallons per tank with mods in my sig. Just depends on where I get gas, and how I drive that week. If you want to get a gas mileage tune you can have one burned that has mid-load level timing added in but other than that nobody is going to change your 14.7 commanded a/f in open loop. If all else is good, I'd change the o2 sensors. They can start to go bad long before they ever throw a code.
when i had the tune installed, i dont think i was getting 14.7:1 ratio. when just standing by the rear of the car while i twas running, the exhaust would sting my nose, and you could clearly tell it was running WAY too rich. now that the tune is off, the exhaust smells normal. i still am wondering about the misfire...it is easily heard, from idle all the way through 2,500rpm. maybe bad plug? thanks for the help.
forpit2000gt
Founding Member
jstreet0204
Active Member
forpit2000gt said:
Where are you getting this from? Do you have any knowledge about tuning to back this up?
I'm going to say this one more time. First most tunes out there have no changes as far as fuel goes except under WOT. And even then, The stock tune commands 12.0 in under in the last few cells of the stablized open loop fuel table. Now in order to make more power, do you think they would add fuel? No, they take it away and change it to around 13:1. If your tune is realy causing you bad mileage, then you may have a bad tune, BUT in general, this is not the norm and anyone saying other wise does not understand how the eec works.
jstreet0204
Active Member
forpit2000gt
Founding Member
I have no doubt that you know a great deal about tuning . I think you don't understand or I worded it incorrectly. There are obviously still problems. I do not tune cars. I take it to someone, but know a little about what is changed. If a plug is not firing and you reduce the amout of fuel , there is less raw fuel going in.If the tune adds more fuel , even at WOT and the plug is not firing correctly, there will be more even more raw fuel dumped. Is this not correct. I don't know if this guy can look at a plug and tell if it looks like that plug is not firing or if he knows how to check for fire. $8.00 and change for a set of Autolites is pretty cheap and easy to do. It deff. won't hurt. I don't even know if most people can really calculate MPG. He removed the tune and things got better. Why isn't this possible? O2s very well may be a problem, hell, the tune with to much fuel and plugs fouled may have damaged the o2s. I I don't work on cars for a living but have worked on cars for 25 years. I get to see a lot of problems in a friends shopjstreet0204 said:
( a lot of Mustangs, no EEC tuning) and help with many friends cars. That is where I get it from.
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