Jump to content
SAU Community

Recommended Posts

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

Link to comment
https://www.sau.com.au/forums/topic/44103-poor-fuel-economy-rb25de-help/
Share on other sites

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.

Guest RedLineGTR

Your Best bet is to look at possibly replacing your oxygen sensor :rant: 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 :rofl:

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

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!!! :D

cheers

Joe

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?

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

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

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...

  • 3 weeks later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • I got back to Japan in January and was keen to get back on track as quickly as possible. Europe is god-awful for track accessibility (by comparison), so I picked up a first-gen GT86 in December just to have something I could jump into right away. The Skyline came over in a container this time and landed in early January. It was a bit battered after Europe, though—I refused to do anything beyond essential upkeep while it was over there. The clutch master cylinder gave out, and so did the power steering. I didn’t even bother changing the oil; it was the same stuff that went in just before I left Japan the first time. Naughty. Power steering parts would’ve cost double with shipping and taxes, so knowing I’d be heading back to Japan, I just postponed it and powered through the arm workout. It took a solid three months to get the car back on the road. Registration was a nightmare this time around. There were a bunch of BS fees to navigate, and sourcing parts was a headache. I needed stock seats for shaken, mistakenly blew 34k JPY on some ENR34 seats—which, of course, didn’t fit—then ended up having the car’s technical sheet amended to register it as a two-seater with the Brides. Then there’s the GT86. Amazing car. Does everything I want it to do. Parts are cheap, easy to find, and I don’t care what anyone says—it’s super rewarding to drive. I’ve done a few basic mods: diff ratio, coilovers, discs, pads, seat, etc. It already had a new exhaust manifold and the 180kph limiter removed, so I assume it’s running some kind of map. I’ve just been thrashing it at the track non-stop—mostly Fuji Speedway now, since I need something with higher speed after all that autobahn time. The wheels on the R34 always pissed me off—too big, and it was a nightmare getting tires to fit properly under the arches. So I threw in the towel and bought something that fits better. Looks way cleaner too (at least to me)—less hotboy, less attention-seeking. Still an R34, though. Now for future plans. There are a few things still outstanding with the car. First up, the rear subframe needs an overhaul—that’s priority one. Next, I need to figure out an engine rebuild plan. No timeline yet, but I want to keep it economical—not cutting corners, just not throwing tens of thousands at a mechanic I can barely communicate with. And finally, paint. Plus a bit of tidying up here and there.  
    • Nope, needed to clearance under the bar a little with a heat gun, a 1/2" extension as the "clearancer", and big hammer, I was aware of this from the onset, they fit a 2.0 with this intake no problems, but, the 2.5 is around 15mm taller than a 2.0, so "clearancing" was required  It "just" touched when test fitting, now, I have about 10mm of clearance  You cannot see where it was done, and so far, there's no contact when giving it the beans Happy days
    • It's been a while since I've updated this thread. The last year (and some) has been very hectic. In the second-half of 2024 I took the R34 on a trip through Germany, Italy, France and Switzerland - it was f*cking great. I got a little annoyed with the attention the car was getting around Europe and really didn't drive it that much. I could barely work on the car since I was living in an inner-city apartment (with underground parking). During the trip, the car lost power steering in France - split hose - and I ended up driving around 4,000kms with no power steering.  There were a few Nurburgring trips here and there, but in total the R34 amassed just shy of 7,000kms on European roads. Long story short, I broke up with the reason I was transferred to Europe for and requested to be moved back to Japan. The E90, loved it. It was a sunk cost of around EUR 10,000 and I sold it to a friend for EUR 1,500 just to get rid of it quickly. Trust me, moving countries f*cking sucks and I could not be bothered to be as methodical as I was the first time around.
    • I assume clearances were all a-okay?
    • Shock tower brace is in +5Kw....LOL  
×
×
  • Create New...