R33 Fuel Efficiency

[mid life crisis]

450 ks and still going fuel light hasent come on yet but needle is almost on the empty mark

[J_Red33]

Well there's been a bit happen on here since I last looked & I'm not sure where to start.

Busky2k's comments are pretty well spot on, O2 sensor is not the be all & end all of fuel enconomy, but it is definantely a big player & the most common cause of poor fuel economy on EFI vehicles. Yes it's nearly always working appart from nearly full throttle, & even if it didn't how long are you going to hold your foot down any more than half throttle anyway in the suburbs?? No more than a few seconds at a time I'd say, you have no choice but to cruise the rest of the time anyway.

Also checking the O2 with a multimeter can sometimes indicate an issue, but isn't always reliable. Your meter needs to be fairly accurate, but is a guide only when dealing with such a low voltage. Hooking up the meter itself can actually change the reading.

The only reason I can come up with for a fuel filter causing bad economy is if it was choking the system enough that rail pressure was dropping. This would then also mean that the injectors would not spray correctly & give poor atomisation, meaning you need more fuel to use up the oxygen in the combustion process. However under heavy throttle this would also result in a severely lean mixture as Busky2k has said.

As far as stalling issues is concerned, there are a range of things that it can be, though the O2 once again is a good place to start. Check this thread out for more info:

http://www.skylinesaustralia.com/forums/in...p;#entry2581556

Also AFM is very unlikely to cause poor fuel economy unless it is stuffed. Cleaning it will actually make the car run richer as a clean AFM measures more air flow & therefore will indicate to the ECU to give more fuel to maintain the right air fuel mix.

Some other things that can cause poor economy include a buggered coolant temp sensor, a stuffed thermostat that's always open, poor sprak, poor fuel atomisation (ie bad spray patterns from injectors) etc. Give me more time I'm sure I could come up with more.

Just as a general rule of thumb though if the O2 sensor hasn't been changed in quite a while & the car otherwise seems to run ok, try it first it should be done anyway & will save you dosh long term even if there are other problems to also fix.

Edited November 6, 2006 by JazzaR33

[PobodY]

OK - so I've tested it to the limit of fuel economy.

A tank full of Ultimate98 will get you almost 600km (I forgot to check the reading before I reset it - it was a long day) of Hwy driving.

I filled up in Hillarys, drove to Bussleton and around the area, then came back to Hillarys - the light came on around the CBD.

I realise only WA members will make any sense of that, but I thought it was damn good economy! That's not slow all the way... and it's not flat-out; average of 110km/h for ~6 hours (just under 3 each way).

[WogsRus]

your lucky, here in tas the longest stretch on higway is only 200kms so eaven on the highway, allthough much better, my fuel ecconomy still sux.

[LightAssassin]

400km for 50L if I do the odd bootful. 450km for 50L if I drive nicely.

I think it would be around 550km for a empty tank (I always leave the 15L in there and fill).

I've got Apexi Pod, Cat back exhuast, SAFCII (came with the car, bonus! Doesn't appear to be tuned though, the Correction scale never moves). Rest is stock... The fuel usage isn't that bad really, and it isn't running lean as it gives a bit of black smoke when I first boot it.

Too bad I do 80km of travel a day for work (40km there and 40km back), so Corolla on it's way

Check your O2 sensor... seems the common thing, otherwise take it to a tuner and get them to diagnose it. Sure it'll cost cash, but it'll save you bucket loads of cash in the long run.

[WogsRus]

I've done it all, tune with SAFC II, no probs there, new pump, new 02, new Temp sensor, new plugs, no errors, and i propably only get 350-400 out of 50 liters in town.

[MBS206]

I've done it all, tune with SAFC II, no probs there, new pump, new 02, new Temp sensor, new plugs, no errors, and i propably only get 350-400 out of 50 liters in town.

I'd be looking at driving style then.

[WogsRus]

yeah, a bit ON, OFF, Sidways, Stop. LOL.

But it only gets marginaly better when the missis drives it.

[mad082]

when i had the wideband o2 sensor on mine, at cruise i was getting about 14.5-1, which is about right. but my fuel economy still sucked. but i really do think it is all about driving style. you may not think you are driving it all that hard, but someone else may be using a lot less throttle at low rpm when accelerating.

as for the afm, i thought it would richen the mixture up a bit too, but then i thought about it. it works off a hot wire system, so with crap on the wire it takes a bit longer to heat up. so it is 1 of those things. a dirty afm may make it run richer, it may make it run leaner. really need to do tests to find out the correct answer.

[MBS206]

I've seen people drive "easily" in there R33s, and come up to neutral pressure/slight boost.

When I cruise, I'm at around 10mm hg when accelerating to a cruise speed.

I barely touch the throttle when cruising. Other people "cruise" just as "slow" and use alot more throttle.

[mad082]

well i filled up yesterday. got 242k's to 35.4L, thats 14.6L pre 100k's, which is alot better than the 17.x i was getting.

then i went down the coast for a drive. was all highway driving. used just under 1/4 of a tank for 150k's. and that was sitting on about 120kmh most of the way (110kmh zone), and my speedo reads a bit under.

something that also affects fuel economy is whether you use the aircon alot or not. i use it heaps, so that uses a bit more fuel.

[mad082]

there are other factorys that play a part too. like wheel/tyre size, tyre pressure, amount of stereo crap weighing the car down, etc.

[J_Red33]

Personally I find the best way to get good economy is chuck it in 5th gear by 60kph (). Used to drive it in 4th around town, but then found that using 5th saved me good half to 1 litre of fuel per 100km (R33's really should have been a 6 speed IMO). I do like giving it a fair bit whenever I can up to the speed limit, & have found that I don't use a real lot more fuel doing so because I short shift most of the time & use the torque.

If I rev the engine past 5 grand a lot then I start to suck the juice a bit more.

My latest fill with a roughly 180km round trip out of town on the weekend + about 370km around town (yes I did top it up a bit mid week & took note of the amount) brought back an economy figure of 10.7/100km. No doubt if I did just highway cruising I could get it down as low if not lower than 10's.

Edited November 8, 2006 by JazzaR33

[J_Red33]

there are other factorys that play a part too. like wheel/tyre size, tyre pressure, amount of stereo crap weighing the car down, etc.

I think these things do play a role, but very small apart from the tyre pressures if they're severely underinflated. Tyre compound would play a role too.

I've never heard of anyone complaining their fuel economy went out the window after fitting a beefy stereo or some nice fats on the back, nor a big improvement either for that matter!

[Munkyb0y]

(R33's really should have been a 6 speed IMO).

agreed

i've got 265's on the rear, and i've been told they reduce economy, i find it hard to believe, but it's possible.

i have to say driving style makes a huge difference. when i first got the car, was getting 250 to a tank, now i've eased up a bit, getting around 320.

my most recent result is 13.3L/100kms. (1200kms on 160Litres)

[HolyEvil]

factory fuel tanks take 65liters of juice

Hithere, is this true for all skylines? I drive a R34 and was wondering how many litres the tank hold. So it's 65 for R34s too>?

Thank you

[HolyEvil]

Hi there, just wondering what's a afm?

cheers

i changed my o2 sensor a few months back. economy didn't change. then i developed a slight miss at idle. finally got it sorted a few weeks back. in the process i changed back to my old o2 sensor, and put a new fuel filter in and cleaned my afm. my economy has improved. i have rather a heavy right foot and i do a lot of spirited driving. i can't remember exactly how many k's i've done this tank, but i think it is about 250k's to 3/4 of a tank. normally i would get about 200 to 3/4 of a tank, but i'll know for sure when i fill up. normally i was getting about 17L/100k's.

so it may be worth cleaning your afm as well. and if you don't want to buy a new o2 sensor, just try giving it a clean with carby cleaner first.

[mad082]

AFM = air flow meter

as for the tyre width, you'd be suprised how much extra drag wide tyres ad. if you think that the stock tyre size is about 205, so thats a total width across all 4 tyres of 820mm. (i know tread patterns vary)

if you run 235s on the fron and 265s on the rear your total width is 1000mm. thats nearly an extra tyre that you are pushing.

if you want to see how much difference rolling resistance makes, get 2 push bikes. 1 road bike, and a mountain bike and roll down a hill. the speed at the bottom of the hill will be much faster on the road bike due to the skinnier tyres.

or get a small 4 cylinder car like an echo, and go for a run adn see what speed you can get up to. then put big tyres on and see how much it drops. a girl i know with an echo has 17's on it. then she busted a wheel and put the stockers back on for a few weeks. she gained about 50k's a tank with the old wheels (195's vs 165's).

[MBS206]

I'm running 265 on the rear of mine, and 235 on the front.

I get 380km to 45L if I'm just cruising and not caining the living shit out of it.

I did 350km to 50L the other week when I was pushing the car for most of the tank.

I get very reasonable fuel economy I find, and I'm running fair size tyres.

Mind you, most people running tyres that are 17" end up having one of there single tyres, weighing as much as all 4 of mine (Light weight Rims FTW!)

[J_Red33]

AFM = air flow meter

as for the tyre width, you'd be suprised how much extra drag wide tyres ad. if you think that the stock tyre size is about 205, so thats a total width across all 4 tyres of 820mm. (i know tread patterns vary)

if you run 235s on the fron and 265s on the rear your total width is 1000mm. thats nearly an extra tyre that you are pushing.

if you want to see how much difference rolling resistance makes, get 2 push bikes. 1 road bike, and a mountain bike and roll down a hill. the speed at the bottom of the hill will be much faster on the road bike due to the skinnier tyres.

or get a small 4 cylinder car like an echo, and go for a run adn see what speed you can get up to. then put big tyres on and see how much it drops. a girl i know with an echo has 17's on it. then she busted a wheel and put the stockers back on for a few weeks. she gained about 50k's a tank with the old wheels (195's vs 165's).

I know where you are coming from with the mountain bike vs roadie, but there are a lot more differences between a mountain & road bike which makes it an extreme case. The other major factor (& I should know being a keen cyclist myself) is air resistance at high speed as the tyre has to cut through a lot more air due to the substantial extra width as well as the chunky tread patterns that they use.

Taking into account a larger frame with thicker tubing bearings with a bit more resistance due to them needing to be more robust & a more upright seating position & we're talking a lot more than just the friction of the tyres. The only extra air resistance a car is going to have is due mainly to what's exposed below the body line, which is bugger all.

An Echo would show up the difference a lot more since they weigh bugger all & have really skinny tyres. The extra weight of wheels in themselves if they increased the width by 30mm a corner, & I'm assuming the diameter of the rims by at least an inch or 2, would be relatively a lot greater on a little Echo. Also when they stuck the stockies back on I'll bet they checked the tyre pressures, something that may not have been done for a while with the other wheels. To cut a long story short there are a lot of factors & if other variables aren't kept consistent then there is going to be more noticeable varations.

Personally I went from the standard 205 size to 225's on the front & 265's on the back & have also fitted a deacent stereo with no noticeable effect on fuel economy. I also check my consumption every time I fill up, so I would have noticed a change. My economy now is better than it's ever been.