Burning Rich

[laksman91]

would it be possible for my engine to be burning rich? I find it extremely hard to reach 400km/tank flat. This is with a calm driving style. I usually rev to about 3200 maximum. The thing is its all city driving.

On the side note: Dont ask why, but a few months ago i filled up the tank with 94Octane (2x in a row):loco would that have thrown off my ratio settings (?)

So what can i do about this problem?

[mazdas3sporte]

yes

[laksman91]

So what can i do.

[dentinger]

im in the same boat...
i cant get better than 450/tank
however, i have an intake, and full exhaust, but i dont race the car too often, and i shift 1st at 3000, 2nd at 3000, and usualy 3rd, 4th around 2,000-2,500.

[laksman91]

im at 370km right now and the light turned on :o
I got a mazdaspeed CBE installed

[dentinger]

shit.
thats really bad.
my record was around 300, but that was back when i first got the car, and was learning to drive stick....

[laksman91]

is there a way to reset "ratios/timings"?

[rcd001]

If you disconnect the battery for 5 minutes the PC will reset. Maybe this will help. I've been running high octane for some time. I stay away from sunaco, because even though the car is more responsive with 94% octane, the gas milage is poor. Try Esso premium or Petro Canada.

Maybe it's the high ethenol content in sunaco gas.

[laksman91]

how do you disconnect the battery terminal do you have to screw it off? :blush i got the cover off atleast:bana2

[dentinger]

haha

10 mm wrench, if i remember correctly. it might be an 8mm.
and jsut turn in counter clockwise until the terminal is loose, and then pull it off.

note: sparks when reattaching the terminal is normal.

[x_o_k_x]

if that doesnt help.. I noticed myself that it takes time to adjust for a proper fuel economy. So let say if you got 400 out of a tank driving calm, you need to fill up at least twice more to get best results. Its just the way it works.
I remember when I drove pure 100% city and my milage was like 550 after fill up. So next time I would fill up it would take the whole tank to adjust to normal driving conditions..and will improve your milage for an extra 100km

[mazda lover]

If you disconnect the battery for 5 minutes the PC will reset. Maybe this will help. I've been running high octane for some time. I stay away from sunaco, because even though the car is more responsive with 94% octane, the gas milage is poor. Try Esso premium or Petro Canada.

Maybe it's the high ethenol content in sunaco gas.

NO need to run high octane gas, just wasting your money. Why are you using high octane? Manual says to use regular...I am sure this has been talked about before..

[kaval]

Only reason to use higher octane is if you are boosted, tuned to run on it, or compression ratio is high. Other than that, if the manual says regular, use it!

Have you had your car tuned to match the mods?

Are you up to date on your maintenance?

[theurgy]

If you use any Ethanol you will lose gas mileage. It's why i no longer tank up with Sunoco Ultra 94 as it uses 10% Ethanol in order to up the octane level.
Ethanol as an additive is stupid really.. I mean it's there so it cleans up the air and for corn companies to profit, however it burns much faster than regular petrol.
With regards to octane rating.. if you are driving a regular Mazda3, there is absolutely no reason to run on any higher octane fuel as your timing and tuning is not set for it, so really you're just paying the extra with no benefit.
Same goes for you Speed3 guys who are stock (not using the Cobb or CP-e tunes).. 94 octane is useless. I usually buy the Ultramar Premium (91 octane) no ethanol in non-urban areas and it's 3 cents cheaper on Thursdays.

Also the best way to calculate your fuel economy as I've found the average on the computer is inaccurate is to do the following.

Go to your regular gas station and pick a pump.
Fill all the way up until the pump clicks.
Reset your trip meter.
Then drive until your car is near empty.
Go back to the same pump and station and fill up until it clicks again.
Now take note of the value on your trip, and the litres on the pump.
This will give you a km's / L value.
Multiply the KM by 100 and then divide by the number of Liters.. and there you have you L/100KM rating.

[laksman91]

Well I only used the 94 octane twice in a row. No longer do it. But I fear it has effected my fuel economy

[laksman91]

for kavals point I haven't tuned it for my new catback but what kind of tuning would I require. And also I am up to date with the maintenance

[condor888000]

K, disconnect your battery, wait about 5 minutes then reattach it. Fire up the car and let it idle for a couple minutes. Fill up on 87 and see how long it lasts.

There is no easy tuning for this car.

[rcd001]

We all run the fuel we use for different reasons; sometimes it may be a waste.

I run high test because the engine timing is advanced, I think it is better for the environment and I think it will keep the engine cleaner.

Even before I had the timing advanced I have always done this practice. Is it a waste of money, perhaps, but it makes me feel better.

Ethanol based gas has effected me on al 3 cars. My honda accord, imprezza and 3. When I travel to the US I find I have to high test because the regular gas makes the engine idle rough on these cars.

I stay away from Citco because I had to clean my injectors when I came back to Canada.

Just my two cents.

[FLIPDADY]

What's your driving style like? City or highway? Do you drive the car hard? Is regular maintenance done on your car?

[Zoom Zoom Boy]

Same goes for you Speed3 guys who are stock (not using the Cobb or CP-e tunes).. 94 octane is useless.

Can you elaborate on why you believe the 94 octane is "useless" in a stock MS3? Not questioning you to be confrontational, I am just really curious as to the reasoning and maybe I will learn something. The MS3 compression ratio is quite high, even for a turbo engine due to the direct injection and on the surface at least, I would have belived that 94 octane would actually be somewhat beneficial to this engine, COBB tuned or not. I would be more than happy to understand if this is indeed not the case and have an explanation as to why.

[theurgy]

Well... it's like this. The gas companies like to make you believe that high octane gas is cleaner and more efficient, when in reality an octane rating is there solely as a guideline to tell you that it is less at risk of pre-ignition.
A regular engine is tuned and timed to run, expecting that the gas will not ignite before it's supposed to.
When you get into forced air induction, you start getting into higher risk of pre-ignition as you have much more volume of air in the cylinder.. so to compensate you use a higher octane gas, which reduces that risk of pre-ignition.
However.. just as much as running 91 octane in an 87 octane tuned engine... is useless as you're paying for a product that will do exactly the same thing in the end.
Running 94 octane in a 91 octane vehicle will do the exact same thing.
My main gripe is that most 94 octane gas in 10% ethanol (Sunoco Ultra 94) and I've already explained my views on 94 octane.
Now getting gas that is unclean as opposed to getting what is perceived as a regular octane gas is a different matter. Some gas retailers use very dirty gas. They cycle through 87 octane gas quick as it's the cheapest and those pumps and lines are used and abused.
89 octane is just 87 octane with ethanol (like Macewan).
The 91 octane is more strictly regulated because of it's applications (higher compression, engines.) This is not to say you may not get bad gas with High test.. it's just a lower risk.
That's just my views.

[rcd001]

My driving style is not really relevant because I drive my 3 maybe 2-3 days per month.

On straight hwy at an average speed of 138km/h I can do 600-625 Km range. I prefer to fill at 600 so I have room just in case I can't find a service exit.

On mixed (city 80% and hwy 20%) I can do 500 - 550.

So in regards to high test being cleaner gas, for a small cost each fill up you get better peice of mind. If you drive a lot I can see it not being worth the cost, but if you are like me and drive less then 20K per year, it is not really going to affect my bottom line.

I have always been more comfortable paying a little extra for peice of mind. Like insurance, you don't really need it (except for legal issues) but in case of an accident the $200 per month is nothing compared to the $10K= for the repair cost. The $200 per month is a constant expence so you can easilly budget for.

[laksman91]

What's your driving style like? City or highway? Do you drive the car hard? Is regular maintenance done on your car?

Driving style relatively calm (up to 3200RPM) with a few spirited moments in a tank.
100% City
I wouldnt say I drive the car hard.
Regular maintenance is done.

[laksman91]

okay so resetting the battery did not help, do I have to wait a few tanks for this?

[chinsterr]

the 3 has terrible gas mileage .... its not your driving style

[kevcol74]

Resetting the battery requires a disconnect of 10 minutes or more. Then, when you reconnect, you need to take the car for a drive at highways speeds for a good 10 minutes. (80km/h or higher) The ecm will recalibrate everything then. Resetting then letting it idel will not work, and driving stop and go won't help either. It needs a steady higher rpm cruise to recalibrate everything.
Hihger octane, as mentioned here many times, is useless in a car not designed for it. Good example would be my brother and his choice. He was running a 97 Mustang Cobra, 305 HP on premium. He traded it in on a 05 Mustang GT, 300 HP on regular!
Me on the other hand, with my 66 Mustang, need as high an octane level as I can get! My car was designed to run on leaded gasoline (look in the archives kids, its old school!)
So 94 octane is good for me!
Regular leaded in my 3 GT and I average 600-650 kms to low fuel light in a 40%city/60% highway drive. Thats pretty good gas mileage in my opinion.

[RX9]

wooo...dude, even my car got better mileage than yours. lol..... i got 450-500 every tank and 100% local driving, you need to reset the ecu for sure, my cousin's GT got 600-700 every tank 40 local, 60 hiwy.

[KPao]

This may not be the most appropriate thread to be posting on for this but since I've had my car I've driven it about 13000km. I kept all my gas reciepts and using them I've calculated my gas mileage to be 6.4L/100km which I think is pretty good considering I do 60%city and 40% highway driving. So contrary to what chinster said I think the 3 has good gas mileage. Tell me if I'm wrong ... since this is my first car and I have nothing to compare it to.

[ravin13]

Depending on how I drive and where... I can either get 450 a tank or less or close to 700 to a tank. Each tank is different how and where I drive, but its mainly city. The 2.0L is good on gas, the 2.3L on the other hand just knocks it down

[whiteomega]

This may not be the most appropriate thread to be posting on for this but since I've had my car I've driven it about 13000km. I kept all my gas reciepts and using them I've calculated my gas mileage to be 6.4L/100km which I think is pretty good considering I do 60%city and 40% highway driving. So contrary to what chinster said I think the 3 has good gas mileage. Tell me if I'm wrong ... since this is my first car and I have nothing to compare it to.

That's about right for the combined cycle you do (city/highway).

Fuel consumption is affected by a large number of things; the weather, traffic, whether it's city/highway, terrain, etc. The only way to objectively compare them is with a dyno, which is what the government does when it tests cars for fuel efficiency.

Your driving style also affects your fuel efficiency. If you speed up to the speed limit and maintain that speed all the way to a stop light, you might be hurting your fuel efficiency vs looking ahead and knowing the stop light is there, and purposefully coasting up to it. Basically if you plan your trip between lights so that you have to speed up as little as possible, you can save a fair amount of fuel (though probably honking off a number of people behind you...)

Back on topic though...when it comes to burning rich, resetting the ECU might help, but if the ECU thinks it needs a higher AFR, there isn't much you can do. The dealer might have a revised mapping (ask for a PCM software ugprade if necessary) that might help fix the problem of running rich. I had a lot of soot on my exhaust tip from running a bit rich, after a pcm reflash, some injector and throttle body service, it seems to be better (still have some soot, but that's expected). After the service, my fuel efficiency got a bit better (down to 9.8 from 10.2 in 100% city)

[kevcol74]

It can also be your MAF Sensor.... If its dirty, then it may not be reading right. It may send the signal to the ECU that more air is passing by it that actually is. So the computer compensates by allowing more fuel to be mixed with the air, thus creating a "rich" burn. Reset the ECU with a battery disconnect for 10 minutes or more, clean your MAF Sensor with some Throttle Body Cleaner, and run it up to highway speed for a good 10 minutes...
That or take it to your nearest dealer and let them fix it! :P

[laksman91]

What is the MAF Sensor exactly?

[kevcol74]

Mass Air Flow Sensor... its between the throttle body and air cleaner, middle of the intake tube (wires going to it) Its in an aluminum housing, just a small sensor sticking through into the air tube inside, meters the air flow, tells the computer, and it adjusts the gas to match....

[stormin84]

you can buy the cleaner for it at NAPA auto parts ( mass air flow cleaner by CRC)

[notoriousb]

u can be burning extremely lean too and still have bad gas mileage...