Fuel Consumption Through The Roof - Related To Fmic?

[colossus]

Hi all,

I have a BF2 XR6T - I keep a log book for tax purposes so I know exactly liters used/kms traveled ect. My fuel consumption has gone from a regular 13.5L/100 to 15.5L/100km and is climbing week by week (average speed of 39km/h and driving habits have not changed). Last tank I babied it around, not on boost at all and only got 15.5L/100 (I was getting 11 when babying at beginning of this year).

Car is up to date with services, have performed solenoid maintenance and tightened exhaust manifold bolts to spec myself. These had no effect.

Car is stock except about a month ago I installed a larger aftermarket FMIC. Could this be the cause? (I still have the stock cooler that I could swap over but its a bit*^&% of a job to be avoided if possible).

Only other option I can think of is to buy two new O2 sensors ($120ish).

What do you think next move should be?

Edited 15/06/10 07:28 AM by colossus

[PHANTMXR6]

Did you get it retuned after you fitted the cooler?

[colossus]

Don't have any type of tune - car is stock bar the FMIC.

Don't really want a tune - I am more than happy with the stock performance and so can't justify the $1000 or so on a tune. Only reason I put the FMIC on is that I picked it up for $50 off a mate (its just a monza).

Edited 15/06/10 08:39 AM by Buf-Phoon

[Panda Eyes]

if you change air or fuel dramatically then you need a tune to suit. that's the reason your economy is up the creek..

[PHANTMXR6]

Best to do some homework first colossus. Untuned you run the risk of leaning out the engine and that could lead to expensive engine repair. I wouldn't be boosting anywhere if I was you.

[Stazza_Brendan]

I changed all the piping and cooler on my stock tune BF2 and the A/F ratio's were fine, on the rich side.

[colossus]

  On 15/06/2010 at 8:03 AM, PHANTMXR6 said:

Best to do some homework first colossus. Untuned you run the risk of leaning out the engine and that could lead to expensive engine repair. I wouldn't be boosting anywhere if I was you.

Hmm I mean I knew I wouldn't be getting any sort of giant performance gain out of it without a tune but I thought for $50 why not? It might keep the charge cooler on those hot days...How can it affect engine longevity/fuel consumption?

[Buf-Phoon]

IMO , spend $50 on a dyno run just to check things are all ok AFRs, boost etc

Cheap insurance

[Panda Eyes]

  On 15/06/2010 at 8:32 AM, colossus said:

How can it affect engine longevity/fuel consumption?

massive increase in airflow. colder air too, which is more dense (engine thinks it is getting more air than it is, the colder that air is) same ammount of fuel= leaning out= massive heat in chamber= detonation (pinging)= piston rod through engine block.

but its just a little bolt on change, so dont worry about it.

Edited 15/06/10 09:19 AM by fordriver1

[colossus]

  On 15/06/2010 at 9:18 AM, fordriver1 said:

massive increase in airflow. colder air too, which is more dense (engine thinks it is getting more air than it is, the colder that air is) same ammount of fuel= leaning out= massive heat in chamber= detonation (pinging)= piston rod through engine block.

This makes sense - but if its using more fuel this would mean the ECU is compensating by running richer? unless my consumption problem is unrelated to this change.