Was wondering if it's possible to tune the ecu to get better fuel economy and if so how much of an improvement it'd make. I'm currently doing city driving and getting 15/17 l per 100km.

Is it worth remapping the ecu to better fuel economy or should i just leave it as is?

Thanks guys

Have you look at the other options to improve fuel economy such as making sure the maintenance is upto date (spark plugs, air filter etc)? Then there is a list of other things that can be checked including the oxygen sensor, dizzy cap & rotor, TPS, leads etc. Also consider your driving style.

Have you look at the other options to improve fuel economy? there is a list of other things that can be checked. Also consider your driving style.

I had it serviced about a month ago and i mentioned fuel economy and the mechanic didn't mention anything was at fault. My driving style is pretty sedate (grandma pace to get best fuel economy possible) could be that my mechanic isn't very good (only charged $150 for a general service! Prior to when i bought the car there was no service history from 90000 kms to around 110000, might take it to mitsfix as I want to do some safety upgrades (transmission cooler, 380 Brake upgrade) see if they find anything. Ive ruled out converting it to gas as the conversion is too expensive, can't afford it.
Thanks for the advice.

Edit: noticed today after using cruise control today I noticed that my throttle got stiffer and seemed to tighten up almost as if the accelerator cable had tightened. Is this normal or should I get it checked out?

I'm currently doing city driving and getting 15/17 l per 100km.

Seen all those start-stop modern cars in traffic? Probably the one in front of you at the green light where you have to wit for the stupid thing to fire up the engine and move off?

the reason you'd put up with that shit is maybe 2-3L/100Km of consumption is idling at the traffic lights.

Best option for you - put the auto into neutral at the lights (why fight the brake with the torque converter), and if you don't need the A/C turn the car off if you know the light cycle is a long one.

make sure the tyres are pumped up hard (a few PSI over the recommended) and take all the shit out of your car - weight = fuel

Best option for you - put the auto into neutral at the lights (why fight the brake with the torque converter), and if you don't need the A/C turn the car off if you know the light cycle is a long one.

make sure the tyres are pumped up hard (a few PSI over the recommended) and take all the shit out of your car - weight = fuel

Thanks for the advice man, I'll give that a shot next time I'm out on the road!

The best improvement to your economy is sensible driving. Every time you put your foot on the brake, that is destroying momentum of the car - and petrol was needed to gain that momentum. Look ahead. If you see the traffic lights are red, lift off and coast up to them. Saves brake pads too. Even if you have to slow to say 15 km/hr before the lights change, it still saves fuel. You don't get to the destination any slower, because yoiu have to wait at the lights anyway. Also, hard acceleration uses heaps more fuel that gentle.

Yes, hard acceleration, plus short trips really burn up the fuel.
To be brutal, a 14 year old 3.5L V6 doesn't have the technology to use fuel efficiently. Just look at the current Mitsu cars and their fuel consumption.
Then again, when the Magna was new fuel was about 65 cents/L, and all the cars of the same vintage had equally greedy consumption. It's just that the cost of filling the tank has doubled in the meantime.

when the Magna was new fuel was about 65 cents/L, and all the cars of the same vintage had equally greedy consumption. It's just that the cost of filling the tank has doubled in the meantime.

That's very true, i was out today for about a 2 hr drive (mostly city travelling at 50-70 km/h) and put the car in neutral at the lights which helped. I got an average of 10.7 L/100km which isnt too bad really.

Thanks for your advice guys it really helped!

Thats what I get driving around the suburbs of Melbourne with fuel economy in mind.

I got an average of 10.7 L/100km which isnt too bad really.!

10.7 is great for start stop traffic - what with G20 Holiday traffic from Brisbane yesterday and having fixed the A/C I got 16L/100 on my daily crawl to work - and that was with a whole heap of Neutral at the lights as apparently the lights are owned by 3 parties, Main Roads, Local Council and the Tram Operator - and none of them talk to each other....

10.7 is great for start stop traffic - what with G20 Holiday traffic from Brisbane yesterday and having fixed the A/C I got 16L/100 on my daily crawl to work - and that was with a whole heap of Neutral at the lights as apparently the lights are owned by 3 parties, Main Roads, Local Council and the Tram Operator - and none of them talk to each other....

That's not bad considering the G20 Summit, you would have thought at least 2 of the parties would talk to each other..... that's disgraceful!

I get 12L per 100kms, and I live in the suburbs of Adelaide, plus I do like taking my GTV our on nice roads in the hills, I had my Cat converter replaced a few months back which helped with my fuel consumption.

Also check out your O2 sensor, a friends Verada exactly like mine was getting 16L/100km when that was stuffed in his, now he gets around 10-11, driving on the same 80km/h roads here.

I agree with Max. Fuel consumption simply wasn't a priority back in the early 3rd gen era.

Yes, you could go down the path of an aftermarket ECU with a economy tune and a performance tune, but spending $1500-2000 on a tune on a car that's worth around $3,000 just to make a small improvement in fuel economy doesn't make a lot of sense to me.

As mentioned, O2 sensors and cat converters can possibly degrade your fuel consumption over time, so you could look at replacing them if desired.

As mentioned, O2 sensors and cat converters can possibly degrade your fuel consumption over time, so you could look at replacing them if desired.

When I work up the cash I may look at getting an aftermarket cat converter (which one would you recommend?) and replace the O2 sensor Just for piece of mind.

If I was replacing my cat on a 3rd gen I'd just go for a basic 200 cpsi high-flow cat. No need to go over the top.

I would definitely endorse the O2 sensor - on my old TJ it was on its way out at 100,000 km / 6 years.

For those interested in what can be achieved, with much time, effort and ingenuity, see this article (http://www.theregister.co.uk/2014/10/19/crawling_from_the_wreckage_essay_making_cars_more_ fuel_efficient/) (found in a rather unlikely of place too...).

Lean tunes can be accomplished with the stock ECU but the limit in just working at the ECU level (as distinct from the hypermiling effort outlined in the above article) is that it would appear (from a fair bit of research) that in most passenger car engines the operational fuel/air mixture can only be leaned out about 8-10% from the stoichiometric mixture of 14.7:1 (to about 16-16.2:1) before power losses become significant and other combustion issues become problematic, which places a fundamental limit on the economy gains. Even more limiting is that drivability concerns tend to require that the fully lean mixtures only be used under cruising conditions.

I gather that fuel economy regulations are pushing F1 engine manufactures to use more extreme lean mixtures than could be practically considered for current passenger car engines, but this technology could trickle down to future passenger cars...

I would definitely endorse the O2 sensor - on my old TJ it was on its way out at 100,000 km / 6 years.

I will be replacing the 02 sensor at some stage, i don't know whether it was replaced recently or not. Is there any way i would be able to tell whether it has been replaced?

Yes, you could go down the path of an aftermarket ECU with a economy tune and a performance tune, but spending $1500-2000 on a tune on a car that's worth around $3,000 just to make a small improvement in fuel economy doesn't make a lot of sense to me.

Whilst I agree, it would depend on if you would save more than the cost, over the period you plan to keep the car, on fuel. Pretty long time to hold the car I'd imagine.

Whilst I agree, it would depend on if you would save more than the cost, over the period you plan to keep the car, on fuel. Pretty long time to hold the car I'd imagine.
I know Knotched has the dual tune on his 380 and he said the fuel savings has paid off the tune. However I am under the impression that he has had the tune on the car for quite a while (i.e. at least 100,000 km). Not sure how many people who are buying 10-15 year old Magnas intend on having them for that length of time.

I know Knotched has the dual tune on his 380 and he said the fuel savings has paid off the tune. However I am under the impression that he has had the tune on the car for quite a while (i.e. at least 100,000 km). Not sure how many people who are buying 10-15 year old Magnas intend on having them for that length of time.

I intend on holding on to my current magna for at least the next 4 years when I get off my P's. A 3.8 is a possibility later this year so I'm considering doing a ralliart tune when I get it done.

Have qny of the magna 3.8 faithful noticed a difference in fuel economy after the swap? I'm keeping my car auto by the way, no manual conversion for 4 years for me :(

i found the fuel economy a little better with the 3.8 but not much

Improvements in the technology to improve fuel consumption have advanced so much since the Magnas were made that it isn't funny.

Best I can get out of my TJ auto is 7.7 L/100 km on a 300 km open road trip in summer, worst is 16.5 just driving short trips to the shops in winter.
Wife's Lancer is 2L manual with electric power steering and fly by wire throttle. It is 12 years younger than the TJ. Easy to get 8L/100 km around town in winter and better in summer, if I keep the revs down. Enough torque to keep up with traffic using 2,200 rpm as change points.

Has it really? I recently saw a thread comparing the economy of new Toyota Aurion's, and they were getting similar if not worse economy than the old Magna's
And my old Camry got similar/same economy to a new one

You can't directly compare a small capacity engine to one thats almost double the size

What seems to happen is they get a bit more power and economy out, then go and add weight so it evens out anyway