Vitara fuel economy?

Post by **Andrew81** » Sat Jun 21, 2008 3:25 pm

What kind of fuel figures are you getting on your Vitaras?

In my 92 model swb g16a carb i'm getting 11L/100 on the highway doing just over 100km/h. Running standard tyres etc. I read somewhere it should be 8.5L/100 city driving, the best mine will do is 11 and is usually worse.

I'd like to get a bit more out of a tank to improve range for long trips and save some $$$

Post by **bugden23** » Sat Jun 21, 2008 5:37 pm

I have a 94 vitara with the 1.6 fuel injected. I have slightly bigger wheels a two inch lift bull bar, dual battery lots of other heavy bits and mine sits around 10.5 in the city and around 8- 9 litres per hundred on the highway.

There are a few different reason for varying fuel consumption,

Fuel filters, air filters and other regular maintenence are a start. Pumping ur tyres up correctly, and making sure u have ur wheels aligned and balanced. Wheel and diff bearings etc.

ALso keep in mind that fuel consumption in a 15 year old car is not going to be what hte guide book states unless you've had the entire car rebuilt

Post by **scooby_74** » Sat Jun 21, 2008 5:43 pm

Thats a little high
Does the vehicle still have the original exhaust manifold on it, some of the carby vitaras had an engine pipe that collapsed on itself restricting exhaust flow then cracking manifold and clogging air filter, all creating poor power and economy.
Suzuki did a service campain replacing them when the vehicles were new but to my knowledge only 40 to 50 percent got done.
Most vitaras get 9-10 ltr per hung on the highway sitting on 110kph

Post by **islandvitara** » Sun Jun 22, 2008 10:00 am

well im only getting 280km from a 42L tank..(is that how big they are?) mines a 97 SWB 1.6 efi. 280km city and highway on a full tank

used to get 350km - 390km when i first bought it - 2yrs ago...
am changing the fuel filter, gearbox oil ect and will update the changes to economy i hope lol

cheers islandvit

Post by **wardy1** » Sun Jun 22, 2008 1:09 pm

im getting round 100km's per 20 litres lol thats a 1.6 carby vit 91 model with 30's

Post by **Gwagensteve** » Sun Jun 22, 2008 9:03 pm

I don't think 11 is far off the mark. You won't see 8.5 IMHO.

Steve.

Post by cj » Sun Jun 22, 2008 9:22 pm

I used to do 8.5 as the norm when I had a new carby Vit back in the day but I have genarally had 10 from a both a carby and efi 1.6 that have had years of use.

Post by **Andrew81** » Mon Jun 23, 2008 11:07 am

Thanks for all the replies.

It receives all the regular maintenence stuff.

I checked the exhaust manifold and it has a small crack. It's a fine crack about 3 or 4 cm long. I'll look into getting another manifold or extractors for it.

I't would be great to get it down to 9L/100 that'd give me about an extra 100km range. At the moment i don't sit on 110 because seems to chew more fuel.

It's a good point that being older and everything a bit worn it wont be as economical as new but i'd be happy with even 10L/100 doing 110 on the highway.

Do larger tyres affect fuel consumption much? I'm looking at going 235 70 or 75

Post by **Gwagensteve** » Mon Jun 23, 2008 11:19 am

In a word, yes they will worsen your economy.

Steve.

Post by **zookieboi** » Mon Jun 23, 2008 2:04 pm

i have a 1990 swb G16A( needs a service thatd help abit.) just drove to ballina and back and it does around 330 highway k's a tank at 110-120
it revs 3.5k @ 110 km/h and 4k @ 120km/h
im thinking of upgrading my tyre size so i do less revs on the highway cause thats where almost all my k's are.

Post by **lay80n** » Mon Jun 23, 2008 2:23 pm

zookieboi wrote:i have a 1990 swb G16A( needs a service thatd help abit.) just drove to ballina and back and it does around 330 highway k's a tank at 110-120
it revs 3.5k @ 110 km/h and 4k @ 120km/h
im thinking of upgrading my tyre size so i do less revs on the highway cause thats where almost all my k's are.

But the increase in rolling resistance from the tyres, as well as the extra weight and hight, combined with the fact that lowering your revs may make the engine labour to maintain the required speed, will probably eat up any potential savings.

Layto....

Post by **zookieboi** » Mon Jun 23, 2008 2:35 pm

hmm what about some perfomance upgrades to counter the strain on the engine.. say extractors etc.. lol

Post by **Gwagensteve** » Mon Jun 23, 2008 3:07 pm

Nope, sorry.

Engines (at stoichiometry) consume about 0.5lb of fuel/hp/hr. (Mightymouse will have the metric version of this - it's 5 grams of fuel per KW per minute, or something)

If you fit larger tyres, it will take more power to push the car down the road at a given speed, due to rolling resistance, weight, gearing and aerodynamic profile.

If you need more HP to push the car down the road, you will consume more fuel.

However, if your car is currently running rich or is outside of it's efficient working zone, (shouldn't be the case with a well serviced, stock car) then gains in economy can be achieved though tuning, but generally they will be very slight.

I reckon a sierra needs about 40hp to push it down the road at 100km/h. Peak HP is 67. 40hp constant = about 10l/100km. A vitara will be much the same. It's hard to imagine it needing much less fuel to do the same job.

Steve.

Post by **zookieboi** » Mon Jun 23, 2008 4:44 pm

ah thanks for the info. i would never have known that.

Post by **jimbo jones** » Mon Jun 23, 2008 7:22 pm

I got 330km out of a full tank in mine

Post by **Gwagensteve** » Mon Jun 23, 2008 8:50 pm

Oh, as an aside, manufacturers will always try and build the most efficient cars possible (for the $$$) and still have acceptable performance. At a constant speed, the power demand is mostly down to rolling resistance and aerodynamics. People don't want to drive cars with deliberately bad economy unless they buy a rotary.

A couple of examples:

206KW Sti Impreza - 1575Kg, lots of driveline drag, sticky tyres - about 9l/100km cruise.

190kw 330i BMW - similar weight, 2WD, auto, excellent engine technology, 6.5L/100km cruise

121Kw Renaultsport Clio, 1075Kg, Manual, abour 6.5l/100km cruise

Once up to speed, aerodynamics and rolling resistance play a major role.

It will be very hard to significantly improve the cruising economy of a car without addressing aerodynamics and rolling resistance.

I've seen some interesting figures- a Bugatti veyron, with 1000hp, only needs about 150 hp to push along its 2000kg at about 130 km/hr.... and 1000hp to push it at 406km/hr (from memory, wind resistance is a square law)

Steve.

Unless you subscribe to the Zagan school of physics. (check the HHO kit thread in General Tech)

Post by **zookieboi** » Mon Jun 23, 2008 8:56 pm

lol you know your shit
i dont think ill be lowered my car and getting a body kit to reduce drag any time soon lol

Post by **Gwagensteve** » Mon Jun 23, 2008 9:07 pm

That'd be the biggest way to make a difference. That's one of the reasons Land Rover made the first Range Rover suspension squat 1" over 80km/hr. (it also increases caster which helps high speed handling, but that's an aside)

Steve.

Post by **bugden23** » Tue Jun 24, 2008 7:18 am

on the question of aero dynamics,

when i lifted my vitara i put spacers under the front springs to make the car dead level,

do u think having the frontward tilt would actually improve the fuel usage ?

Post by **Gwagensteve** » Tue Jun 24, 2008 7:35 am

In all honesty, I doubt it would make enough difference to measure.

Steve.

Post by **zookieboi** » Tue Jun 24, 2008 9:27 pm

i would say that it would be more aerodynamic on the body rather than under it, but yeah i agree with steve it would hardly be measureable

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