Carguy8888

iTrader: (1)

I am about to send my pcm back to my tuner for a few separate updates. My car runs great but abnormally drinks gas. I have not checked it out due to a forever Winter in the Northeast. I am guessing it is probably my oe o2s w/ 100k I hope. My question is do I bother listing this question when I send in my pcm for my tuner to take a look or does the tune not affect gas mileage? I hope this is not a stupid question. Thanks guys.

redtan

iTrader: (5)

If it's running rich, then yes a tune can help restore the mileage you used to have.

However if the fueling is fine, then a tune will not help much if at all with that unless you go with some sort of open loop tune and run the car much leaner than stoich.

Carguy8888

iTrader: (1)

Thanks for your reply. Do I need hp tuners to tell if it is running rich? I currently have Frost's basic bolt on off the shelf tune which runs great to me as a novice. I am sending it back to raise the shift points and reduce the values for the t/c. I was not sure if I should have asked him to look for an issue?

gagliano7

Probably the ethanol in the winter gas. My commuter car lost almost 4 mpg this winter and the car is only a year old. Plus the car idles more in the winter.

Carguy8888

iTrader: (1)

Good point but I have not used the car since October. It was this way all thru the Summer.

rpturbo

iTrader: (47)

There are tons of places in a tune where you can pick up or reduce mpg's in a tune. It's not just a one afr and that's it deal. The cold start enrichment, DFCO, and A/F ratio during part throttle/cruising just name a few, but can make a big difference. Sure, winter fuel is garbage also, and of course with that also comes low tires unless you check them a lot or have C02 in them.

Carguy8888

iTrader: (1)

Ding, that is the answer I needed. I will ask my tuner to take a look. No co2 and tire levels are ok. New rims and tires about to go on too. No winter fuel b/c the car has been sitting since the first snow in October. I can almost see the needle move w/ a basically stock a4 in mixed driving. I also did a tune up over the Winter wires, fuel filter, potz tb and maf is clean. I also will check & change the front o2s. Ty.

danieloneil01

The only difference in winter gas is the RVP. Gas year round has ethanol in it if you go to a station that sells E10.

Carguy8888

iTrader: (1)

No E10 here.

67SS509

iTrader: (25)

You really need to log your car and feed that info back to your tuner.

Other things more likely to hurt fuel mileage:
-bad knock sensor(s) causing low spark timing
-bad O2 sensor(s) causing excessive fueling
-vacuum leak or exhaust leak causing excessive fueling
-misfires causing the converter to unlock

Carguy8888

iTrader: (1)

Is the only way to log with Hp tuners or Ls1 edit? Will a Snapon scan tool tell me anything?
No vacuum leak or exhaust leak and no codes. I am going to buy new 02s. You are the first to tell me about the knock sensors.

rel3rd

iTrader: (43)

Quick story...

My local so-called "LS1 expert" dynotuned the car and although it ran well at WOT, ran like crap anywhere less than that. He was no help in getting it the driveability it should have had.

Back in 2008, I was able to locate a used HPTuners setup and had no clue what to do with it, lol. Steve, aka Frost, was able to help me straighten out the "tune" my car had, noting that there were a multitude of hacks, shortcuts, and downright cluelessness left by the original "tuner"...

Anyway, simply using datalogs emailed back and forth, Steve was able to get me MUCH closer to a perfect tune, and also could not have been anymore helpful in explaining what he changed and why. He also coached me part-time for a while so I could learn to tune my own car, and also helped me straighten out a donkey-dick cammed Z06 that my buddy had dynotuned at the same place here locally...

so as a suggestion...

Find someone locally with HPTuners who's willing to help you datalog, OR find a used setup, and datalog the car in any situation that Frost asks you to. Email him the logs, and he'll be able to help you get to the bottom of any problems you may have, while also getting an even better tune than he already is able to give you.

This also eliminates having to mail away your PCM.

That is what I were do if I were in your exact situation.

AnotherWs6

iTrader: (17)

I live very close to Carguy8888 and I also get absolute dick mileage for no apparent reason. It has been brought up to me before that gas is very different than it was 12 years ago.

Carguy8888

iTrader: (1)

Do you go to any cruisenights?

Carguy8888

iTrader: (1)

I got my pcm back, this is what Frost said;

"Yeah it doesn't really work that way (in regards to mileage). To the extent that the MAF curve is corrected for the intake tract changes, it's covered. The front O2s control ALL fueling except for first startup and WOT. If the tune is 5% rich at cruise, through feedback from the O2s, the PCM first corrects the error and then learns it, so it's automatically applied next time it's in that 'area'. If you have ANY even tiny leaks at the heads or at the collectors, it's hurting fuel mileage."

I guess I know what I have to look at.

AnotherWs6

iTrader: (17)

I don't go to any cruise nights typically. Know of any good ones?

I am going to do this though. They did it for the first time last year and said they got about thirty cars. Cruise around for an hour or so in a big cavalcade around Westchester, then meet up and have food and a car show. The guy who organized is one of my company's vendors. I spoke to him about it after he saw my car on one of my monitors in my office. He said that they did it at a restaurant parking lot last year, but that the response he got afterwards was so overwhelming that this year they are doing it at a high-school because they need the room. And of course it's for a good cause. My buddy with a 69 Camaro is also going. Hope to see you there.





is now officially over, please resume.

Carguy8888

iTrader: (1)

Sounds good, pm me where you are in Westchester.

The Silver Goat

At the end of the day (in my opinion and we all know what opinions are worth...) if you're concerned about mpg, tune your LTFT's to as close to 0% as current conditions will allow. You can log data with with a slew of different products and putz around your self or work with a tuner... I have used Diablo's hand held for 9 years. I dicked around with the seat of pants this feels good and that feels good. Did that for 4 years. I went to a local tuner who works with Diablo, had him use my hand held and dyno tune my goat. Now I have two settings. A mpg tune which runs my LTFT's as close to 0% when cruising up north or long trips on the e-way drives. If I'm going out to rape the gear box I flash the dyno tune. What ever your method of madness, HPT, EFI or Diablo, enjoy

redtan

iTrader: (5)

Why wouldn't your power tune also have LTFTs as close to 0 as possible?

And regardless if your LTFTs are between -1 and 1 or between -7 and 7 you will still get the same ~14.7 AFR and thus the same kind of mileage.

Carguy8888

iTrader: (1)

You two guys are much more technical w/ this then I.