Poor Fuel Economy (rb25de) - Help!

[chicane]

Dear all,

I have done a search on the forums regarding poor fuel economy (R33 RB25DE Non-Turbo), however I am am at a bit of a loss on what I can do. After filling up on a full tank of Optimax last week, the needle was exactly at the 1/2 full mark at 200 km. Then the needle was at the 1/4 full mark at 240 km.

I drive daily across town (less than 10 km each way) from home to work and back, usually in peak hour traffic, lots of stop-start driving. Since the last fill, I have driven about 100 km on the freeway @ 100 km/h. I do accelerate hard usually - revving out to ~5K rpm..

Judging by the smell of the exhaust gases it smells like it’s running rich (I can smell the exhaust from the cabin) but there is no noticeable smoke at all. Plugs changed not that long ago, different AFM tried, put in a new battery 2 weeks ago (so ECU is reset). My car is stock apart from aftermarket exhaust and pod filter.

Usually I am getting approximately 350km off 50L of fuel.. (~15L/100km)

What are other RB25DE owners getting in the way of fuel economy? What else can I do?

cheers,

chicane

[JAMESW]

I get around 400-450 driving it hard.... and around 500-550 driving it like a granny.

James.

[Zombie]

Maybe just the fuel gauge tricking you??

Adam

[chicane]

Maybe just the fuel gauge tricking you??

Adam

Nah dude, the car is actually drinking a lot..

[SKY031]

You say that you were judging from 1/2 a tank to 1/4 of a tank.

It doesn't work that way.

If you fill the tank, you will get more K's between Full and half, than you will between half and empty.

When was the last time you changed your fuel filter?

Also take a look at the fuel you're using.

Optimax (in my opinion) isn't as good as some of the other available fuels, and you won't get the best economy on crappy fuel.

[SKYLINED]

Dont u have to stamp on the brake peddle a few times as well after disconnecting the battery to reset the ECU?

Just a thought....

[Guest RedLineGTR]

Your Best bet is to look at possibly replacing your oxygen sensor i know one or two people who replaced thiers with a new one $120 dollars later (this was about a year or so ago) they got an extra 120km out of a tank this was in a turbo as well and an r32 gtst

[Guest RedLineGTR]

Try the above mentioned first but i doubt it will help much

[SKYLINED]

http://www.skylinesaustralia.com/forums/sh...ead.php?t=43095

[NuGGeT]

when i first got my skyline i had rather shittie fuel economy, but i later figured it was because i was doing alot of small drives, 15min each time. after i started driving alot more/ longer drives it got better n better. also before i bought my car it sat around for a few months n only got driven every so often so that may have been why aswell

[Pva_Glue]

1. never trust guages... they trick you

2. try some octane booster to clear out some build up on spark or fuel lines

3. check oxygen sensors...

4. check for fule lines just incase its not leaking some where under pressure

5. check your right foot... may have some build up of LEAD!!!

cheers

Joe

[CroatianDlite]

got prices straight from nissan

- o2 sensor $209.75

-coolant sensor $93.85

can anyone do any better than that >?????

[chicane]

Thanks again for the replies people,

CroatianDlite: apparently U can use a Ford o2 sensor, not too sure on what the model is though.

I considered changing that but apparently the o2 sensor is only used by the car at idle? Can anyone confirm this?

[paulr33]

buy a ford el oxygen sensor its the same part. its made by bosch. i got mine for $117 brand new. just say u need an 02 sensor for a ford el faclon at like repco and woila! problem solved

the o2 sensor gives feedback to the ecu so it can run lean and save fuel. thats its only purpose and lasts about 40,000ks before it dies.

when it (the o2 sensor) dies it cant tell the ecu to run lean and therefore the ecu just defaults to "rich" mode and waste's fuel. i did this on my series II r33 about a month ago and got a massive fuel economy increase. the ford el part worked fine.

I wasnt able to swap the sensor over as i didnt have the right tools. its a bitch to get to on the rb25 with normal shitty spanners. but if you do it yourself you need to cut the wires and match them yourself as the ford el sensor wont come with plug, just bare wires. theres two common wires (heater wires) and one power. so you cant really **** it up.

its not used by the car at idle. its used all the time. it plugs into your exhaust manifold and gives feedback to the ECU on exhaust gases and then the ecu can lean out the mixture when you arent on full throttle. the o2 sensor is only used when arent on full throttle. on full throttle the ecu just runs rich anyway

[_turtle_]

interesting, sounds like i need a new 02 sensor too then. when i first bought the car i could get 500k's out of it with some to spare. these days wen i'm up to the last quarter its only around 300ks.

for some reason, after i changed rims to 16" with wider tyres my economy went worst.

good idea to check ur plugs and replace em if necessary

[CroatianDlite]

looks like the new o2 sensor from FORD is doin the trick. if anyone has seen my other post, i talk about the engine "Stutterig" .. well it seems it has definately stopped that.. also the car seems to drive a lot smoother now! so far im impressed. but i havent done enough k's yet to tell u about fuel economy.... actually tomorrow night im going to rooty hill and back and that a 88 km round trip with traffic and freeway conditions. so ill get back to you on that...i usually blow 1/4 to half a tank.. depends on how fast i go... sometimes i can get home in 25 min... lol...

[riggaP]

I do accelerate hard usually - revving out to ~5K rpm..  

Here is your problem...

[Cubes]

I remember some one posted this a while back.

For the R32/R33

O2 sensor:

NGK 205 JAPAN

#0A08

[White-R33]

Before I did the conversion I was going through about 350-400km for a full tank.

I drove it hard though.....

Doesn't sound too over the top to me, see how the o2 sensor goes, doubt it's the problem but worth a go !

good luck mate

[chicane]

Hmm last fill i got 20L/100KM.. im going to change the o2 sensor on the weekend and see how it goes.. :S