11ish mpg ?

[Trile]

only city driving.

car has 80.000 miles
-borla
-remap
-darintake
-dv's replaced
-all belts replaced
-new sparks
-no cels
-ocassional o2 sensor error (once a month) on vag-com
-idles fine
-boost peaks 18 or so, holds 14/15

Is it possible to get such horrible mpg if I live in a town so small that I can drive from one end to the other in under 10 minutes ?
No highways, a lot of traffic, traffic lights, speed bumps etc. Imagine a typical eastern-european city (but smaller and uglier)
I never boost in the first 10 minutes, and 90% of the time I drive like a granny (mostly to check whats the best mpg I can get).
Can it be that the mpg is so lousy because the car is not even warmed-up and I'm already ..wherever I wanna be ?

And yes, I didn't buy the car expecting great mpg, but I think it's gotten progressively worse over the half year I've owned it.

[Monty23]

Have you logged egts?

[Trile]

Nope. I was guessing that an EGT related error would pop up with vag-com if they're shot.

I'll search how to log them (I only know how to log boost lol) unless someone is kind enough to give a quick explanation :)

[wheel366]

My MPG is horrible with the city. Right now I am sitting at around 130 miles to half a tank. Highway was always great. This has been the worst though for city. However, this is also the first time I have used Total Energy 9000 0W-30 in this car so maybe this has something to do with it but I figured I would get better MPG than with the 5W-40 Amsoil I have been running. Maybe it is because of the oxygenated gas. Who knows.

[Thizz_S4]

In a study we did for the ARB in Cali found that fuel sources around the world all differ and changes all the time no matter how consistent the processing procedures are and can have a big factor on vehicle fuel mileage and especially during the times of seasonal fuel changes due to the fuels being mixed so when everything is looking ok on my car i usually relate it to the fuel and i always use top tier fuel. . . just thought id share

[csosnowski]

what rpm are you shifting at?

I found that if I shift ~2250-2500 (in town) that I get better mileage. I can squeeze ~20-21 mpg in town this way. I also did some timing and fueling tweaks with lemmi though, so ~17-19 without tweaks.

[Trile]

2000 to 2500 rpms shift.
and yes, our fuel is no match for yours, or for that mather, almost any other fuel in the world, but I always use what's considered premium here.

I forgot about lemmi. Do you have any suggestions what to tweak or maybe tell me what and how much you tweaked? And consider the above-mentioned terrible fuel :)

edit: forgot to add - I think I've heard popping/backfiring when I lift off in 2nd gear (moderate throttle). I guess lemmi fuel tweak (decreasing load) could help iron that out ?

[csosnowski]

I have an apr tune and it runs a little rich so I removed like .8% from primary, 4% from secondary and added 3deg timing. Also I increased lambda regulation to 3.

If youre popping on decreasing load (shifts) then yes, I would try pulling some fuel from decreasing load. small bits like 2%.

it is good to log after these changes, here is some logging info: http://s4wiki.com/wiki/VCDS

[RedB5S4]

EGTs don't always throw codes. 11mpg sounds horrible, even for city driving.

[Trile]

I have an apr tune and it runs a little rich so I removed like .8% from primary, 4% from secondary and added 3deg timing. Also I increased lambda regulation to 3.

If youre popping on decreasing load (shifts) then yes, I would try pulling some fuel from decreasing load. small bits like 2%.

it is good to log after these changes, here is some logging info: http://s4wiki.com/wiki/VCDS

So what you did is set: -0.8 (or 8?)on channel 10,
-4 on channel 8
+3 on channel 9 ?

Thanks.
I'll first log Egts (and what else?) , and then set about tweaking if necessary !

btw, hope you understand that the need for further help is not only because I'm not really good with tweaking/maps/etc and of course, english is my second language, and google translate doesn't work when you type - timing offset, retarding?, and other technical terms :)

[csosnowski]

no worries, here are some settings:

channel 6 = +3
channel 8 = 96.1%
channel 9 = +3 deg
channel 10 = -0.781%

for channel 3 (decreasing loads) 97.7% would be a good start to try and get rid of the backfiring

these are very small tweaks and very conservative because I dont want to damage my car (or anyone elses) but I do know that some engines are different and like slightly different things.

log 02 voltages and see what they are in addition to your egt's.

I wouldnt start making any changes until you figure out if there is a hardware issue. EGT's wont necessarily throw a code if they are aging (iirc).

Fuel blend (winter) may be playing a part in this as well.

More lemmi info: http://s4wiki.com/wiki/Lemmiwinks

[mrandersons4man]

I would replace your o2 sensor. A bad one can deffinitely have an effect on gas mileage. Sounds like the code it's throwing is intermittent. Also a new fuel filter wouldn't be a bad idea if it hasn't been replaced. Check tire pressure, alignment, balance, and wear.

[Trile]

I've read that o2's an't really affect mileage that much !?
anyway, I'm planing on getting catless downpipes and coding them out. If you can run on coded out o2's, I guess they can't be doing that much 'damage'..

Fuel filter replaced 2 months ago. Alignment done a month ago. New tires.

[mrandersons4man]

It depends on which o2 sensor is throwing the code. The rear o2 sensors which you plan to code out are strictly for emissions. However, the front o2 sensors are used to adjust fueling and such. So potentially they could be causing the problem. If you remember you could tell us the code next time it shows up.

[Trile]

Oxygen (lambda) Sensor, B1 S1: internal Resistance too high.

Googling tells me that is the passenger front o2 :/ Damn.
Altough, if they only come up every few hundred miles, can it be related to the quality of fuel (lack of it actually) ?

Where can I find the cheapest front o2?

[RedB5S4]

Are your secondary sensors coded out? If they are just swap them.

[Trile]

not yet. But good idea.
Can I just swap them now and live with a CEL for a while? Or do they have to be coded out ?

[dubzackvr6]

I'd say your primary passenger 02 is toast.

[davenew]

I'd say something is wrong. My last S4 was stage 3 and my average never dropped below around 15-16mpg mostly driving hard from stoplights in town.

Maybe check vagcom and see if you're getting misfires. My current yellow S4 was and it ended up being sluggish primary O2 sensor. That was after we ruled out plugs and coil packs.

[mrandersons4man]

Usually when the code comes up like that then it means that the sensor is on it's way out. I would replace it. The passenger side is fairly easy. Just make sure you get the correct o2 sensor socket. I have used the universal bosch o2 sensor from autozone (Bosch 15733) with good results. Some say that the splicing kit will change the resistance reading but they have worked fine for me. I know jhm also sells the sensor.

[Trile]

Maybe check vagcom and see if you're getting misfires. .

I plug vag-com, and check something like 'misfires-total' or smth like that, not for individual cylinders/
And there sure are some, maybe 5 or 6 misfires in like 2 minutes. And that's when the car is cold. It bucks and jerks a bit but all of that goes away when it's warmed up.
Is that OK or should there be ZERO misfires?

[ezfour]

Well if you are getting an internal resistance too high DTC then the O2s will still work they just wont heat up the same and they are likely on their way out. You can verify this by logging the O2 voltages at idle, part throttle, and WOT.

Whats interesting is that I was getting IRTH for both primary O2s and my mileage has actually gone down since replacing as well as not solving the misfire problems I was having. Have you checked for any kid of vacuum leaks?

[Trile]

boost gauge shows vacum at -20 on idle and steady, doesn't fluctuate at all.
at wot hits 18 holds 15

also just installed the silicone hose kit.

[RedB5S4]

Yeah, the primary and secondary sensors are interchangeable. It's the cheapest way to go about replacing an o2 that's on it's way out. Obviously, if you pull the secondary o2 harness out, it's going to throw a CEL, so you'll need to get it coded out.

My passenger side o2 is throwing the same code as you with an intermittent CEL. My secondary sensors are already coded out, I just don't have the motivation to go out and swap them, haha. Unfortunately, you're going to have to pay either way (for a new sensor or for the code-out).

[bigdo26]

I've been down to about 7 mpg.



At the local road course ;)

[Trile]

update on this:
I ordered new front o2 sensors, but seeing how crazy slow the mail is these days, I'll be lucky if I get them in the next 30 days.
So tommorow I'll be swapping the rear o2 (that don't have errors) with the fronts (that get intermitent errors for both banks). Btw those are the only cels I'm getting. B1 S1 and B2 S1 internal Resistance too high.

I tried playing with lemiwinks, and though I got rid of the backfire by lowering fueling on decreasing loads, I still get 10/11 mpg

Last time I filled up half a tank, and drove it for 5 days ALWAYS shifting at 2000ish rpm, NEVER flooring it = 11 mpg.

Who thinks that the new o2s will solve my problem?

I'm always a pessimist so I think the problem will be somewhere else :/

[bigdo26]

fuel leak?

[pjhock5]

It does sound like you have a fuel leak somewhere...but another area to check is do all of your wheels turn freely? Could be starting to get bad wheel bearings or sticking calipers. My rear calipers have started to stick fairly bad and my mpg around town has decreased from 17-18 to 15-16. Not saying by any means that this is your entire problem but something to check.

[Trile]

fuel leak?

wouldn't I get the... fuel smell ?
I also did the vag-com readiness test, or smth like that, and the first thing it checks is fuel lines/leak etc

[smashed s4]

yes something is wrong... i drive my b5 like a racecar and i get 14-16 mpg city

[Trile]

another question, could be related.
I check my mpg with the on-line calculator cause my lcd isn't repaired (yet).

When the fuel level is low, gauge in the red, I put let's say 6 galons (about 25 liters) and the fuel gage goes to the middle or a bit over it. It shouldn't be in the middle if the tank capacity is 60 liters (16 gallons)
Could it also be that if it the gaugereads a bit too high, it can also read a bit too low?
Cause that's how I calculate average, by filling up and waiting for the low fuel beep.

[smashed s4]

When your gas light comes on you usually have 2 gallons or more left in the tank

[Trile]

so in totall 7 to 8 gallons of fuel.
That's still not more than half of the tank imho.

[airjawed]

Basing your mileage on only half a tank of gas is not accurate at all. Do a few full tanks and then you would get a better idea. The fuel gauge may not be reading a half tank accurately and it is too small a number to work with.

[Trile]

anyone who had 'busted' primary o2's feel free to chime in and say how bad was your mpg :")

[ThirdStrike]

Id bet you have a leaking injector.
Do this with vag-com
log your fuel trims at idle -> group 032 -> read this to figure out what youre looking at http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info
log idle misfires -> group 015 & 016
log your EGT sensors if you havent already. they should read 1035 with the car off and 945 with the car on at idle. Make sure its not causing your car to run super rich. **> group 112 in vag-com
e
p.s. I get ~15mpg city and ~7-10 when WOT on corn

[S4 00 2.7]

+1 on checking your injectors.

[70 eliminator]

fill the tank all the way and instead of working the last half work the first half....

it will still be a half a tank to fill up.. aND YOUR FUEL PUMP WILL LIVE UNDER FUEL ALL THE TIME SO IT WILL LAST LONGER.

also the fuel guage is non linear in 90 % of cars it gives you a relative reading when you are at 1/2 tank fill up and i bet it is not exactly half of tank capicity -2 for the reserve

[killerkali]

Empty to half is around 4 gallons then the second half to full is 10. Took me a while to understand haha

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[AudiMat]

anyone who had 'busted' primary o2's feel free to chime in and say how bad was your mpg :")

I just found out both my primary's were bad when I got my VAST ecu installed early this week, and my gas mileage is horrible. I burned through a half tank in about 70 miles driving around Chicago. I don't have any precise numbers for you to go by, but if your sensor is bad it is absolutely going to affect your mileage. It will eventually throw you into limp mode as well.

I'm really curious to hear your thoughts when you take it out. I am going to try and save the labor and do mine myself, but I can't order them until after I recover a couple weeks from all my xmas shopping. Please let me know any trouble you run into taking it out and if you have any pointers for me when I do mine in a few weeks. TIA!