Mods for Fuel Economy ?

[cyber_scriber]

Brad, I think you'll be pushing it uphill on this. Twin turbo, V6, 1,500kgs and good fuel economy rarely go in the same sentence

Having said that, you generally improve mileage by increasing engine efficiency, reducing weight or improving aerodynamics.

As others have mentioned, you can remove the sound deadening, roof racks etc.

Other options include using low rolling resistance tyres and appropriately sized rims, "thin" and fresh oil (which makes quite a bit of difference to economy), removing the rear spoiler if you have one, so as to lower drag, and keeping the motor in a good state of tune.

As a side thought, have you considered the mod cost vs benefit analysis? I.e. Sure, you might get slighter better economy through mods but the savings from the economy gains could easily be outweighed by the cost of the mods themselves!

I recall a situation where a Honda Prelude owner wanted to buy a new Jazz for the better fuel economy. The Prelude was worth about $10k and the new Jazz was nearly $21k. He gave up the idea when it was pointed out to him that it would take him nearly a decade in fuel savings in order to recoup the additional $11k purchase cost!

 

[bradc]

The ralliart one can just be cleaned. I recommend an air compressor from about 30.48cm away (1 foot )

The intercooler alone will give reasonable gains as the ecu sees the air temp being lower. An SAFC can also be setup to keep things a bit leaner at the lower end of the rpm scale for better economy.

Stay with 0w30 oil as Bruce recommended, it is the right spec for a VR-4 anyway and keep the tyres up at around 40 psi.

 

[king_panther]

As a side thought, have you considered the mod cost vs benefit analysis? I.e. Sure, you might get slighter better economy through mods but the savings from the economy gains could easily be outweighed by the cost of the mods themselves!

Already posed in an earlier post there Bruce. With the mods that are being suggested, it'll take some driving to recoup the cost in fuel savings (if there are indeed any). All it takes is a few moments of spirited driving & your tank drops by half.

I"ll accept it's probably a lost cause. The cost is far outweighing the benefits.

The Hyundai i30 CW Wagon Diesel is looking more worthy. But again that's a large cost. I might just run the Grandpa into the ground.....

Those mods are destined for the Super.

 

[king_panther]

The ralliart one can just be cleaned. I recommend an air compressor from about 30.48cm away (1 foot )

The intercooler alone will give reasonable gains as the ecu sees the air temp being lower. An SAFC can also be setup to keep things a bit leaner at the lower end of the rpm scale for better economy.

Stay with 0w30 oil as Bruce recommended, it is the right spec for a VR-4 anyway and keep the tyres up at around 40 psi.

Thanks Brad. What's your opinion on the 'lowering boost' question ? Tyres are always monitored for their pressure & are refilled with nitrogen at each tyre service.

MEEK use 10w50 oil. Should I be therefore changing to 0w30 ?

 

[bradc]

I would change to something w30, either 0w30, 5w30 or 10w30. The 6A13 engine is designed to run on w30 oil as per mitsi original specs.

What pressure do you run in your tyres?

You can't lower boost easily, so don't bother. Accelerating slowly and smoothly will see you off boost anyway, and you should always change up into a higher gear as soon as possible. The one exception is 5th, stay out of 5th around town. The auto box wants to change into 5th at 60kmh which is too early and it just sits there slipping the torque converter tons. Not only is it great for super heating your transmission fluid but it is also great for using fuel. Mitsi should have made the change point about 70kmh instead.

 

[king_panther]

I would change to something w30, either 0w30, 5w30 or 10w30. The 6A13 engine is designed to run on w30 oil as per mitsi original specs.

Those original specs though would relate to the conditions in Japan ? Should exactly the same rating oil be used for Oz where our conditions are much different ?

What pressure do you run in your tyres?

I run 42psi in mine. I have BF Goodrich G-Sport tyres.

You can't lower boost easily, so don't bother. Accelerating slowly and smoothly will see you off boost anyway, and you should always change up into a higher gear as soon as possible. The one exception is 5th, stay out of 5th around town. The auto box wants to change into 5th at 60kmh which is too early and it just sits there slipping the torque converter tons. Not only is it great for super heating your transmission fluid but it is also great for using fuel. Mitsi should have made the change point about 70kmh instead.

I'm normally a slow accelerator anyways so the boost doesn't come on, but our turbos kick in so low that sometimes it's hard not to get on boost. Thanks for the tip about gearing, even though I do have an auto. Got a tranny cooler in there too. A lot of my driving is done sitting at the 110km/h limit on freeways & I'm sitting on 2500rpm.

Would hard piping give any increase in efficiency to go with the intercooler ? How about the rear wing on these things ? Is it for any purpose or just for styling ?

 

[bradc]

Rear wings on wagons are complicated. I'd leave it on, but I'm not sure how much it helps.

I don't think hard piping will help much for economy at all.

I would use w30 oil no matter what. The thermostat will keep the water and therefore oil at virtually the same temp unless you are trashing the car and the system is overwhelmed.

 

[cyber_scriber]

How about the rear wing on these things ? Is it for any purpose or just for styling ?

The principle behind a rear wing is to increase down force. However, on street cars, rear wings are pretty much redundant for this purpose.

You need to be doing some silly speeds before the wing provides any meaningful downforce and doing those speeds on the street will mean bye bye licence. On the street, rear wings tend to slow you down and increase fuel use as they tend to create more drag.

On street cars at street speeds, rear wings are primarily for show and tell and aesthetics. As Bradc has alluded to, it's not clear how easy it is to remove the rear wing from the Legnum. Before doing anything, you might want to firstly check out how the rear wing is attached and whether it will leave any unsightly bolt holes, if removed.

From everything you've said (i.e. I want better fuel economy, I drive so boost doesn't come on etc), it sounds like you're in the wrong car! Lol!

 

[bogan bob]

Legnum would weird without rear wing, esp the series 1s

Good thread Brad, i had been wondering how to improve fuel economy too as job prospects are suggesting i may go from 300ks/week - 6-700/week (to get to work only, so no tax benefits )

Ive got the panel filter and exhaust covered, but now for the dam intercooler........

 

[king_panther]

From everything you've said (i.e. I want better fuel economy, I drive so boost doesn't come on etc), it sounds like you're in the wrong car! Lol!

As I have posted earlier Bruce, the car wasn't bought for performance, but for the safety.

The combo of constant 4WD, AYC, Traction Control, ABS etc in a wagon that WASN'T a Subaru & for under $14,000 was hard to turn down. When your wife has been disabled from being hit by a car, that really means something. I've driven through the shittest of conditions & this thing has never let me down in terms of stability & road-holding characteristics.

The guy I bought it from was a workshop & had a non-turbo Legnum. If that could have been registered, I'd be driving that instead of the turbo.

 

[king_panther]

Legnum would weird without rear wing, esp the series 1s

Good thread Brad, i had been wondering how to improve fuel economy too as job prospects are suggesting i may go from 300ks/week - 6-700/week (to get to work only, so no tax benefits )

Ive got the panel filter and exhaust covered, but now for the dam intercooler........

I've seen a few S1 Legnums without the rear wing on them. I think Kitty's VR4 doesn't have a wing & that's a 96 model. I'd be willing to remove it if it meant something in return. The S1 rear wings are attached to the car by the side arms. The top wing doesn't touch the car itself, rather it's attached to the side arms of the rear wing-piece. The S2's rear wing does attach itself directly to the car, as does the rear wing on the Supers too I believe.

Hehe gee man you're nearly doubling your k's ! I pretty much am averaging 1000kms a week

 

[montgomery]

As said earlier , an aftermarket ECU does wonders for fuel economy.

I see why you have the car , and it is a good choice , but i also see where your coming from with the fuel side of things.


There isnt really anything practical that can make a BIG difference your your
L / 100km

 

[Guest]

hi dont no if anyone has said about nitrogen instead of air in your tyres. and the good old fashioned way dont drive short journeys, bus it

 

[qball]

Legnum would weird without rear wing, esp the series 1s

.

There's a series 2 for sale on carsales with the rear wing removed, It looks poo

 

[Kenneth]

Don't remove the spoiler. It is NOT a wing. A wing is for down force, a spoiler is an aerodynamic aid which is usually there to reduce drag.

On a wagon, there tends to be a large area behind the car which is in vacuum due to the air displaces when the car is traveling (like a truck). The purpose of the spoiler is to direct air down the rear of the car to fill this area and reduce the vacuum.

Please don't call it a wing, it isn't.

 

[king_panther]

hi dont no if anyone has said about nitrogen instead of air in your tyres. and the good old fashioned way dont drive short journeys, bus it

Yep I've had nitrogen in my tyres for years now.

 

[king_panther]

Don't remove the spoiler. It is NOT a wing. A wing is for down force, a spoiler is an aerodynamic aid which is usually there to reduce drag.

On a wagon, there tends to be a large area behind the car which is in vacuum due to the air displaces when the car is traveling (like a truck). The purpose of the spoiler is to direct air down the rear of the car to fill this area and reduce the vacuum.

Please don't call it a wing, it isn't.

Thanks for the tip Kenneth. Spoiler it is then. So how about things like vortex generators & rear diffusers ? Will they make much of a difference to the air flow ?

 

[godzilla]

So how about things like vortex generators & rear diffusers ? Will they make much of a difference to the air flow ?

By the time you finish with all these mods to your car you should have better fuel economy than an Toyota Yaris!!

 

[king_panther]

By the time you finish with all these mods to your car you should have better fuel economy than an Toyota Yaris!!

Haha good one !

We should setup a 'Hyper-Miling' thread. See who can get their fuel economy down to the lowest !

(Keeping it in the garage doesn't count !)

 

[bradc]

I win then, 640km from 53 litres