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horrible gas mileage help: open loop

13K views 38 replies 17 participants last post by  siscoa36 
#1 ·
hey my teg has just a basic ihce and my gas goes down like crazy i only get about 200 miles for a full tank and i have been driving real slow and in high gears my spark plus are brand new air filter clean tire pressures right have no clue. does it need to be tuned
what could be causeing this problem?
 
#2 ·
teggsr22 on May/25/06 said:
does it need to be tuned
what could be causeing this problem?

yes.
begin by reading the articles on tuning. it'll help out in power, emissions, and fuel economy.
 
#6 ·
more specifically you need to part throttle tune or street tune,since gas mileage is about "closed loop" ecu operation at part throttle and occasionally some "open loop" ecu operation at part throttle.

dyno tuning is full throttle tuning.

we have a Common Topic in Gen 3 forum on gas mileage which is the thread where I discuss what factors contribute to better gas mileage.


there's a kazillion threads here on gas mileage already if you enter "gas mileage" in the advanced search. Please look at those.

Secondly, it is NOT just about tuning either . Poor maintenance is also responsible for poorer gas mileage on top of tuning. wrong tire pressures, dirty air filter , improper spark plug gap and heat range, improper ignition timing also contribute as well.

As we said in those other gas mileage threads here before, MODIFYING DOES NOT NECESSARILY GUARANTEE WORST GAS MILEAGE either. The people who think the ecu overfuelsto the change in increased breathing misundertands how an ecu works.

they don't know what these mean or the issues around them:


part throttle vs full throttle

closed loop ecu vs open loop ecu operation means

I explained them in another thread today as well to another member with the same misconceptions.



They should learn those to help them understand things better.
 
#10 ·
PLEASE FOLKS:

look at this

and this


this topic is so beaten to death here and to drag it back out again and say the same things is the height of laziness. Is there any info on here that wasn't said before that this person could not have read? (rhetorical question)




we beg you folks to search first before you post and read for a reason.

to make better use of the forum space and discussion topics.


PLEASE. I EMPLORE THE NEW MEMBERS TO USE THE COMMoN TOPICS AND SEARCH FIRST.

I can't believe people don't do the simple search entries first still even after the long ass registration sign up process.
 
#13 ·
shore96teg on May/25/06 said:
try cleaning your O2 sensors (or getting new ones) a lot of times that will improve gas mileage.
O2 sensors? as in both? don't you mean the front sensor only ?

the front O2 sensor before the cat is the only one that controls fueling by the ecu (closed loop ecu operation).


don't you mean for him to check the front O2 sensor connections or whether it is working (by checking the wiring voltage and resistance) instead ?

how did you clean your O2 sensor ?

A lot of the times the sensor is seized in the bung and removing it can accidently damage it. So be careful if you are taking it out of the bung. You may need liquid wrench.

when installing a new O2 semsor I always brush on anti-seize into the bung's threads in case I have to take it out in the future (with less hassle).
 
#14 ·
if he's saying that his temp gauge only goes a little past "C". then buddy, looks like you need a new thermostat. that might be one of the biggest reasons contributing to your bad gas mileage. cold engine needs more fuel. it could be a bad temp gauge, but there is a good chance its your thermostat.
 
#17 ·
i have stock 95Ls 2dr MT with only catback exhaust. get around 27mpg in summer and 22s in winter.

theres many little things that gives you bad gas mileage. when i added some lacas or locas(whatever it is) fuel system cleaner, it saved me 1mpg...lol yea 1 on average. cuz i used to get 26.

but thers many more, like new/better air filter, fuel filter, spark plugs and wires, and a whole lot more(i wish someone would make a list) that i dont' even know(i hope) but i do want to know cuz im trying to get up to 30s.
 
#18 ·
MichaelDelaney on May/25/06 said:
PLEASE FOLKS:

look at this

and this


this topic is so beaten to death here and to drag it back out again and say the same things is the height of laziness. Is there any info on here that wasn't said before that this person could not have read? (rhetorical question)




we beg you folks to search first before you post and read for a reason.

to make better use of the forum space and discussion topics.


PLEASE. I EMPLORE THE NEW MEMBERS TO USE THE COMMoN TOPICS AND SEARCH FIRST.






example: 7 page thread that covered checking fuel filter, lines, plugs, wires, etc


it's the same old skipping CD....

Quote: MichaelDelaney on Nov/25/05
there are several gas mileage threads here.


it's not one thing that results in poor mileage. there are several causes.

we talked about them in the old threads.

the biggest ones that beginners don't understand is the difference between part throttle performance and full throttle performance.

ECU or chip programs work in 2 modes: closed loop and open loop.

closed loop is mostly for part throttle performance and relies on the front (ahead of the cat) O2 sensor feedback to correct the tuning for the car. This is what mostly affects gas mileage from a programming point of view.

open loop is mostly full throttle performance and does not rely on the front O2 sensor to guide the chip. It relies on fixed commands from programs in 2 maps. It does not affect your gas mileage as much when you daily drive because you don't spend a lot of time with the foot planted to the floor. 95% of your daily driving is part throttle tuning and performance and closed loop.

simple maintenance things like cleaning you air filter, checking your tire pressure (using the high end of the recommended range to get more mileage because the tire contact patch becomes smaller and has less rolling resistance to the road and remembering air contracts when it's cold and expands when it's hot), using the right plug heat range and gap, adding fuel injector cleaner once a year, doing the oil change at recommended intervals.....

these all improve mileage...

there's more...

look at the old gas mileage threads in the search....
 
#21 ·
Kendra on May/26/06 said:
can we please once and for all do away with miles per tank?

I agree. That is not a precise indicator and can lead to false impressions.

actually the most accurate way believe it or not is to weigh the car and use the change in weight and the known density of fuel and ambient temp. to calculate gallons or litres consumed and then divide that into your change in mileage.

that's how the race teams do it. they don't guesstimate how far the fuel needle went down by to a given mark on a gauge.
 
#23 ·
Kendra on May/25/06 said:
Quote: 98BlackTeg on May/25/06Don't use xxx many miles to a tank - but give us miles per gallon.

can we please once and for all do away with miles per tank?
I think most people realize that this way is not very accurate, but I also think they see it as an easy way to get an estimate. Fill the car up, reset the trip odometer, check again when fuel is nearly gone, compare with previous readings, get rough idea of mpg performance. In other words, no, it's probably not going to go away.
 
#24 ·
In addition to the articles Michael suggests, review Common G3 coolant problems in the G3 forum.

Toledo64fx (midway down on page 1) didn't mention any performance mods. His profile doesn't show that he has any. He just said his temp gauge was low. Would you agree that his symptoms indicate a bad thermostat?

I brought this up to teggsr22 because I was curious if it could be a contributing factor for him. His car is 9 years old and may have the original thermostat.
 
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