ok i know this will get moved to the newbie forum but anyways i figured i could get enough responses first..when a car runs lean does that mean more air for each unit of fuel or less air per unit of fuel..analyzing i would assume lean means less fuel more air..but I wasn't sure..I installed an mbc and have my car running at 20 psi till redline..and i'm getting WAYYY worse fuel mileage..i'm not even driving my car hard that much..but I went from like 22 mpg to like 18 mpg by just raising the boost to 20 psi to redline from 19 psi tapering to 16 psi...and I'm driving exactly the same..it has been at like 17 or 18 mpg for a good few tanks now so I know that it has lowered my fuel economy? any reason for this? is there anyway I can fix this? 18 mpg is really crappy since I do like half city and half highway driving...by the way my only other mods are the adapter/cone filter and a forge recirculation valve..thanks guys

 

your got it as far as the lean situation. As far as the gas mileage you probably changed your driving habits a little. I have never got much more then 200miles to a tank personally but i have a serious problem with lead foot. Now that i did all this work i think i will be lucky to even get to 200miles.

Chris

 

Yeah I usually get about 200-210 at the 12 gallon mark. I usually try to shift at 3k all the time but ya know how it goes, sometimes you just gotta have some fun.

 

ya i usually see between 200 and 220 for the 12 gallon tank..is there anyway to make the mileage better? i would think if i got al to tune it it would run even more lean..would that make my car have better gas mileage? i'd like to get 240-250 out of a 12 gallon tank of driving the way i do now....is this too much to ask realistically? thanks guys for ur input too..very helpful

 

Well hmm let me think. I dont think you will pick up much better gas mileage. Try a different gas company. I use Shell but i buddy of mine said to try Exxon i think he said or somthing else and he said he picked up some mpg. I dont know how true that is though. All i can say is if you wanted a high mpg car should have got a prius or echo or somthing...lol... no offense im not trying to be rude or anything but you can only expect so much out of a turbo car.

Chris

 

Newb question, but does raising boost automatically lean your AFR? (It seems that's what redevo8driver is explaining in post #1. But maybe I'm just connecting two unrelated topics.)

 

The stock ECU will make the changes that have to be made normally. But there are certain things that confuse the ECU like a intake. This is only becouse it gives weird reading from the MAF and the ECU doesnt know what to do.

Chris

 

any other ideas on fuel economy? i know that the evo is not the best or ever gonna be..but i want to make the most out of it..i drive ALOT..like i mean a lot..so i've been spending WAY to much on gas..like i said all i have is a bov, intake, and mbc..i'm not tuned yet...making about 17/18 mpg average..(thats with highway and city about 50/50) i thought maybe because of the extra flow from the intake maybe it required more fuel to stay at the same AFR..is that true?

 

Honestly i would try and take off your intake and go back to stock. Your not gaining much except the sound of the BOV. And i would be willing to bet that you pick up some mileage off that IMO.

Chris

 

piggyback or reflash would help.. i hear a lot of people getting better gas mileage from slight tuning

 

ya i'm gonna try that actually..thanks man i'll let u know how it works

 

Isn't our tanks 14 gallons? I thought I read that on the manual. Try shifting before boost hits at around 3300-3400 rpms. Max torque happens at 3500, so shifting before that, on regular driving, might help with your gas mileage. I already refueled 3 times and I just got my car last thursday and have about 600miles on it.

 

ya we have 14 gallon tanks..but for some reason our fuel lights come on after 12 gallons..i've gone to like 12.4 gallons down..but i dont know I always refuel before that because I feel like when that light goes on and has been on for like 20 minutes it's time to refuel lol..i was told the 03's had a 12 gallon and the 04's had a 14 gallon but my manual says 14 gallon on mine and i have an 03..so who the fu*k knows lol..

 

The most gas I have ever put in my tank is 12.3 gallons. The fuel light had just come on and the fuel gauge still showed almost 1/8 of a tank. I'm pretty sure the 03's have a 14 gallon tank.

As for getting good gas mileage, just keep the car from boosting. With about 22-25% throttle you can accelerate up to 3000-3500 RPM without using much fuel. If you have a boost gauge, just keep it in vaccuum while accelerating. The car uses ridiculous amounts of fuel under boost.

 

I have an xede piggy back and I average 20 miles to the gallon with city and highway. I get on the car a few times a day.