N/a Fuel Economy Thread

[r34_25GT]

Before i get flamed, yes i have gone through various fuel economy threads and that is exactly why im posting up here.

Ive come across a wide range of people who claim they are getting 400-500km's per 50L (how much it typicaly takes to refill when the yellow light comes on)

Now this is quite interesting, seeing as the best ive gotten out of my tank was around 370ish and that was with granny driving and not going over 3,500 once during the whole tank. Driving rather spiritly, i get somewhere around 340ish at best..

My car is a rb25de neo r34 2door; basicly lowered, 255's at the rear, 2.5" cat-back exaust so its pretty stock, its even running a standard air box.

I am puzzled what could be causing this. Everything else in the car is working beautifully and the car is in very good nick. Idles normally at around 650-680 RPM.. Any ideas ??

Edited March 7, 2009 by r34_25GT

[lachlanw]

have you checked the o2 sensor ? and what state it your air filter in /get a new/less restrictive one

[lachlanw]

also tire pressures ,wheel alignment , how much crap are you haulling around, get a vacume gauge and use that to drive nicely

[r34_25GT]

What tyre pressure would you guys reccomend for 255/35/18 at the rear and 225/40/18 for the front ??

Basicly, i am carrying absolutely nothing in the boot, no subs, no amps, so in general nothing that weighs the car down further. As for the checking the O2 sensor i havnt gone into doing that yet. Btw how many K's do you guys get around per tank ??

cheers

[_bobo_]

i got a 33 rb25de i get around 400km if i push it to yellow light and drive around with it on for a bit..

i use to have air panel filter than changed to a pod and actually got slightly better fuel economy =]

[Aggroman]

my car must be busted haha this is all my k's going down to approx quarter tank, never let it get much less

Idle is 900rpm when warm.

norm drivin to and from work with the occasional once every few days rev out to 5grand sees me roughly 370-390 to a tank depending if i go to penrith alot or not ie traffic.

when i was on holidays i didnt care about economy and saw close to 450 down to a quarter tank..

Highway driving to canberra got me 650 roughly using 3 quarters of a tank.

If i have the silencer in my exhaust it eats petrol on the highways.

R34 Neo 2 door manual

Mods: 3 inch kakimoto exhaust

really stiff bilsteins

Also have Sub and work boots/clothes in boot

Tyres and pressure: 225/40 R18 at 38psi.

My gauge definately isnt broken before you say anything.. Best jap tune in the world perhaps??

[Chang]

I've got a R34 sedan, stock standard. 35 PSI tyres.

Do quite alot of highway driving and get very close to 600 km's a tank quite frequently. NO thrashing.

If I have a heavy foot that week, I get approx 450-500 km's.

I use to get quite low milage as well. About 400-450 km's. I just gave the car a oil change, air filter and spark plugs and could see a difference immediately.

Edited March 7, 2009 by Chang

[_bobo_]

yeah good service should improve fuel eco. usually oil, oil filter, fuel filter, plugs n air filter which i guess is reccomended every 5k-10k km i guess

[MissR34]

i get about 400kms per tank...............if i do hwy driving maybe another 80 or so kms.

thats with 3" exhaust, extractors, pod + a few other things aswell.....

R34 manual

idle bout 800-900rpm when reached temp

tyre pressures.........this is for 19x8 with 235's and 19x9.5 with 275's i normally do about 40psi

[r34_25GT]

hmm ive noticed alot of you guys are idling alot higher than me =/ .. generally id look at that as a bad thing lol yet it seems you are all getting better fuel economy regardles... hmm strange =(

[Silver_GT]

R34 N/A

ive set my idle at 650 when warm

I get 12.8L per 100km (bout 400km till the light comes on)

Not great for a daily but seems like a good number for a skyline?

[TokyoTaxi]

I WAS getting good fuel economy until I had a fualty coil pack and changed the set to some new Splitfires. Fuel economy dropped by about 80-100 km per tank

When these coils die, I'm putting genuine ones back in.

edit: was getting ~500km per tank around town & 600km on hwy.

[LUME]

im happy i can get 350 my fuel gauge stays on full then goes down in roughly an hour :S:S

[Reggi34dr]

Gee Scott, thats very strange about the Splitfires. I have them also and am glad they've been good to me.

I'm struggling to understand though why cold or operating temp idle rpm has any effect on overall fuel usage. the car is stationary at idle, yeah, not working/revving to propel the vehicle forwards.

Ive been noting my fuel numbers since i've had my full exhaust installed and slight timing change. I'm still averaging 500-510K's when the fuel light comes on, still averaging over 620K's to a tank and my best out of a tank is 680K's. the reason i manage such no's is because my travels is 95% highway.

[TokyoTaxi]

Gee Scott, thats very strange about the Splitfires. I have them also and am glad they've been good to me.

I'm struggling to understand though why cold or operating temp idle rpm has any effect on overall fuel usage. the car is stationary at idle, yeah, not working/revving to propel the vehicle forwards.

Ive been noting my fuel numbers since i've had my full exhaust installed and slight timing change. I'm still averaging 500-510K's when the fuel light comes on, still averaging over 620K's to a tank and my best out of a tank is 680K's. the reason i manage such no's is because my travels is 95% highway.

1. I only found out about genuine vs. a/market coil packs "after" I installed mine. It seems there are quite a number of people who have found out that genuine coil packs are superior in every way to other direct replacements ( including Splitfire ).

2. If your cars not running right at idle ( let alone everywhere else ) you can chew up a large amount of fuel sitting there doing nothing. Usually, the indication that this is a problem is a sluggish take-off or miss-fire. Also, pronounced popping in the exhaust on low speed decel can indicate an idle fuel problem.

3. I would LOVE to see fuel consumption figures like yours ! BTW, how much did you advance your timing ?

[cosmic starz]

the only real way to get a reasonably true estimate of fuel consumption is to fill up your car at a level bowser until the pump first clicks off and note the odometer reading , you can also re-set your trip meter - then drive the car till about 3/4 to near empty go back to the same bowser fill again till first click-off and record how much fuel used - this shows up on your docket usually at most petrol stations - and note the new odometer reading (which should your trip meter reading should match - then do the math using a calculator

none of this, "I drive 500k till light comes on nonsense"

my experience with a R34 GT 5 spd man NA with 4.3 diff is a best of around 9.5l/100 mixed suburban and highway/freeway when there is easy flowing traffic and no long delays with speeds up to 90 kph or so and with only occasional big bursts of acceleration

the normal result is 9.7/100k for about the same conditions -

very sadly no better result with higher speed cruising even though mostly in top gear - say Sydney to Wollongong and back - this is probably because the 4.3 ratio means you are using higher revs than are really necessary when hi speed cruising (e.g. VY Commodore cruises at 110kph at under 2000 revs whereas a R34 (4.3 ratio) uses around 3000 revs - a really stupid diff ratio only good for acceleration and crawling at idle in very heavy traffic - maybe ideal for Tokyo lol)

and there was no variation between when I had the OEM Nissan coils in or after I put in Splitfires - did I emphasise that enough????? lol again and more lol

doing the usual things like new plugs good air filter etc will help economy so will having the air con off when not essential

also you can regularly re-set your ECU (by disconnecting battery for at least 10 seconds) and this may help in certain cases

and quality of fuel may effect mileage also (no e10 pls)

9.7 l/100k is about as good as it gets for a sporty 6 cylinder car from 1998 or so weighing about 1500kg

if your only getting 13-15 l/100k average or worse then you should be concerned

[ewhs]

I drive a R34 NA auto sedan, I tried in vain to accurately measure my fuel consumption but based on my estimates, i get around 430-450 to a tank in Melb city area...best consumption i got was 530ks when i did some highway driving

I noticed that the fuel gage is not very accurate so I noted the KMS when the fuel gage reads half full (approx 30litres).. My reading varies between 220-270 kms.

[TokyoTaxi]

the only real way to get a reasonably true estimate of fuel consumption is to fill up your car at a level bowser until the pump first clicks off and note the odometer reading , you can also re-set your trip meter - then drive the car till about 3/4 to near empty go back to the same bowser fill again till first click-off and record how much fuel used - this shows up on your docket usually at most petrol stations - and note the new odometer reading (which should your trip meter reading should match - then do the math using a calculator

none of this, "I drive 500k till light comes on nonsense"

my experience with a R34 GT 5 spd man NA with 4.3 diff is a best of around 9.5l/100 mixed suburban and highway/freeway when there is easy flowing traffic and no long delays with speeds up to 90 kph or so and with only occasional big bursts of acceleration

the normal result is 9.7/100k for about the same conditions -

very sadly no better result with higher speed cruising even though mostly in top gear - say Sydney to Wollongong and back - this is probably because the 4.3 ratio means you are using higher revs than are really necessary when hi speed cruising (e.g. VY Commodore cruises at 110kph at under 2000 revs whereas a R34 (4.3 ratio) uses around 3000 revs - a really stupid diff ratio only good for acceleration and crawling at idle in very heavy traffic - maybe ideal for Tokyo lol)

and there was no variation between when I had the OEM Nissan coils in or after I put in Splitfires - did I emphasise that enough????? lol again and more lol

doing the usual things like new plugs good air filter etc will help economy so will having the air con off when not essential

also you can regularly re-set your ECU (by disconnecting battery for at least 10 seconds) and this may help in certain cases

and quality of fuel may effect mileage also (no e10 pls)

9.7 l/100k is about as good as it gets for a sporty 6 cylinder car from 1998 or so weighing about 1500kg

if your only getting 13-15 l/100k average or worse then you should be concerned

PMS ?? did I emphasise that enough????? lol again and more lol

But seriously, I'm glad you've had no ill effects from "your" Splitfire coilpacks, but others have ( including myself ), and have documented it. Some big HP applications have replaced their Splitfires with new OEM coilpacks and have "gained" power.

Anyway, I can live with the fuel economy I have so long as petrol doesn't get too much more expensive.

[R33 Ribby]

i can get 400 out of a tank without light on and on the weekend i drove to airport and back trip is 475 km thats what i got reading at no light 1/4 of a 1/4 left highway driving u get alot more

[paulr33]

mythbusters ahoy!

this thread is full of myths and assumptions with no facts

there is no logical way that upgrading the coils to splitfires would affect fuel econonmy that drastically

i suggest there is something fundamentally wrong, for it to go from 500kms a tank to 100kms a tank

go see a mechanic - it doesnt add up