Terrible Fuel Economy, All Usual Suspects Checked

[stolen_s15]

dam you all i get 350km around town in tassie, no matter how i drive, and not much better on the high way.

That suggests that the parts of your fuel map you use during light cruise are too rich. Get rid of that central20 ecu and get something adjustable.

[stolen_s15]

Changed over the fuel filter today, and it was filthy. As I shook out the excess, the fuel that came out was a really dark brown, yuck! Also changed the spark plugs and gave the air filer (pod) a bit of a clean.

Car seems to be running a fair bit smoother now, particularly on idle. Cant really tell if its drinking less yet, but will report back.

(Also changed windscreen wipers, easy another 10-20rw/kw now. )

[_Ryan_]

i get 25-35% more KM's from a tank on the fwy, with a 10yo O2 sensor... What oil are you using(my 25 loves Fuch's 10w30)? All filters done? Plugs gapped right? TIRE PRESSURES? i have mine at 40psi after a 2km drive then lower them for spirited driving to help tire wear/economey, that is on 225/50/16's.

[stolen_s15]

Just got 16L/100km exactly with 100% city driving and a fair bit of thrashing.

Should be able to crask 370km out of the next tank, *fingers crossed*

[r_palac]

I get about 400km's on my r34 before the fuel light comes on. Then when i fill up to the top i only seem to be puttin in around 50litres. I believe 34's have a 65litre tank? therefore when my fuel lights turns on i should still have around 15litres left.

Most driving is done in the city and i always seem to give it a bit here and there

I changed my 02 sensor recently.

Will be doing an oil change soon.

How much to replace fuel filter?

[LBR33]

I get about 400km's on my r34 before the fuel light comes on. Then when i fill up to the top i only seem to be puttin in around 50litres. I believe 34's have a 65litre tank? therefore when my fuel lights turns on i should still have around 15litres left.

Most driving is done in the city and i always seem to give it a bit here and there

I changed my 02 sensor recently.

Will be doing an oil change soon.

How much to replace fuel filter?

less then $10 from supercheap

[stolen_s15]

My tires are at 34psi all around, will pump them up to 38-40 and see how the fuel goes, not expecting much but you never know.

Also in the new year I plan to get an full road tune with a wideband, which I have been told will make a big difference in economy.

[frozenwaffles]

hmmm be intertested how you go with the wideband road tune. i am still only getting 350Kms to 55litres... not very happy...mainly city driving.

[Cubes]

My RB30DET is making a shade under 270rwkw and still gets 450km's to a tank (50L) with the odd squirt; no free way driving; all local 60-80km/h shortish (30km one way max) drives. Every time I accelerate off at the lights I'm always ahead of the traffic but not pushing it; only just slightly on to boost with light throttle and changing up at around 2500-3000rpm.

I had mine tuned for the o2 sensor on and now with it disabled; absolutely no difference to economy.

Maybe its the R33's VCT thing as R33's tend to suffer from bad fuel economy a hell of a lot.

Must suck to own an R33/RB25DET. Sorry gotta rub it in.

[J_Red33]

Not mine Joel .

I get 400 - 450 km's to about 50 litres around town (400ish if I use the aircon a lot & drive it really hard). Fuel economy was terrible before I changed my O2 sensor which appeared to die from being removed from the stock dump & into the new one when I had my exhaust fitted. Was alright for a couple of weeks & then economy went out the window & the car was using about 15L/100km, after I changed the sensor it went down to under 12.

Another thing I've had cause my economy to drop was the thermostat, which when I pulled it out had a broken seal (standard 33 thermostats have a rubber seal to prevent any flow when cold). Never got up to temperature in winter & was chewing probably at least an extra 1 to 1.5 litres per 100 km from running too cold.

Cleaning the injectors I can personally vouch can make a big improvement if they are dirty. I used to do injector testing & sometimes when they'd come in they could be spraying a solid jet of fuel, which is no good for vapourisation. This would be an especially good idea if your fuel was rather dirty.

Pleanty of things to check.

Edited January 6, 2008 by J_Red33

[stolen_s15]

^^ Yeah I was thinking the same thing about dirty injectors, and I've already purchased some S15 injectors which I'll install once cleaned and flowed.

I was going to get it all done this week, but after a light tap with a brick wall I have another thing to fix first.

[Jmaac]

coolant temperature sensor will also cause bad fuel economy

[_Sawyer_]

I really like this thread because of stolen s15's avarter lol.

Seriously, does any 1 know what nissan's fuel economy claim was for the r33?? when you think about it tho, a turbo charged sports car with 4.11 diff ratios etc etc, having fuel economy around 12-13ltrs/100km isnt toooooooo bad.

then again if people are getting 500-550km out of a tank, i want to eat my left arm

[stolen_s15]

How would I know if that is playing up?

[Cubes]

I really like this thread because of stolen s15's avarter lol.

Seriously, does any 1 know what nissan's fuel economy claim was for the r33?? when you think about it tho, a turbo charged sports car with 4.11 diff ratios etc etc, having fuel economy around 12-13ltrs/100km isnt toooooooo bad.

then again if people are getting 500-550km out of a tank, i want to eat my left arm

I remember seeing specs a while back; it supposed to be around 10.5ltres per 100. My old rb20det used to get exactly that.

[J_Red33]

Yeah you just have to remember with that rating that's on a combined fuel cycle of city & highway driving.

Around town I chew no more than 12L per 100km as previously stated (got 11.73 on my fill today, & that was with the use of aircon), but if I do long country drives it'll hit the low 9's. Half way in between is about 10.5, so sounds about right

Edited January 15, 2008 by J_Red33

[stolen_s15]

Well I dont think my coolant temp sensor is playing up because I can see the temp on my PFC controller, sits around 72deg after taking about 5 mins to warm up.

This weekend I'm going to get the car on a hoist and do an inspection of all the fuel tank/line area, even though RE customs has already checked this I'm almost at my wits end!

[Cubes]

72degree's is too low.

It should be up over 80degree's.

If I start the car and instantly drive it; within 2-3minutes the engine temp is sitting on 80degree's.

[grigor]

You still haven't had the road tune, and is your 72degrees correct????

Presuming your tuners haven't altered the PFc's settings, that means you'll be running between 5% and 10% rich on fuel.

Perhaps it needs a temp. sensor but the tuner should have picked that.

Useless "tuning" an ecu with incorrect inputs.

Edited January 16, 2008 by grigor

[stolen_s15]

Cubes 72 degrees is too low? Damn! I do have a very large aftermarket aluminium radiator and breather tank setup, would that explain the lower temp?

Grigor just got back from holidays mate, trying to get the road tune sorted but I'm going to be installing bigger turbo/inj/afm soon so I dont want to do another tune (unless I can get it for free) just before I get the goodies in. Why would the 72deg be incorrect? Will have a check of the coolant sensor and give my tuner a call again.

Thanks for the help fellas, and keep the ideas coming.

Nick