Help Needed With Fuel Consumption...

[frozenwaffles]

Hi guys, just wanted to pick your brians and get some advice.

my 1995 R33 Gtst runs great. my mods are 3.5" xforce turbo back exhaust, gfb stealth fx bov, apexi power intake, just jap FMIC, power fc.

i just had the O2 sensor replaced and also had the injectors cleaned a little while ago.

but im still only getting 250 to 350 kms per 60litres of BP ultimate. i went for a highway drive to noosa and the best i got on a tank was 500kms. i would expect more than that.

on average its about 15L/100kms. not very good imho.

i am running 205rwkws and 13psi of boost.

given the new o2 sensor and supposedly cleaned injectors, where should i be looking to solve this issue???

any specialists you recomend?

thanks

[Dale FZ1]

Keep off the throttle.

Use the power, and you'll use the fuel. Simple as that.

There's lots of previous threads (hint: try the search function) about fuel economy/usage. I have logged an arithmetic average over 15000km of 7.4km/l

Gentle highway running, rolling on/off throttle and keeping out of boost I can sneak up to 9.5, and extended fast running with hard acceleration and big throttle opening + boost runs it down to under 6.0

Most likely nothing inherently wrong with your car, but that's what they do.

[32vspecII]

get an aftermarket ecu and have it tuned

then you know your afr's are right and your not getting anything funny from the stock ecu running at its limit

[SS8_Gohan]

^ I think he's got a power fc....

so about 13.5L/100km's Dale? interesting way of quoting economy figures... most people will understand litres per 100km's..

If you're not giving it a lot of stick, 15L/100km is quite high...

[Taso84]

Trust me man, thats pretty normal, especially if ur in the inner suburbs, where its very stop start.

If u wanted to conserve fuel, i would suggest that u keep ur car in the 2 - 3000 rpm range and off boost so the engine is not under load, and use 5th gear on highways and freeways

[Guilt-Toy]

off boost my 300rwkw rb30det does 11.7 litres per hundred (meassured by the RTA at an emissions test) but as soon as i go into boost it will go up to around 20 litres per hundred or more.

But i tuned the power fc myself to get that

Edited February 13, 2007 by Guilt-Toy

[Spook's_Skyline]

dude, i dont think you can do much better than that

i have exactly the same specs, and i get about 350k/s a tank around town

and about 550 on the highway

doesnt matter whether i baby it off boost the whole tank or not

any money says when you reverse, you can smell fuel also

ive replaced my o2 sensor, had the car retuned by matty spry (he said the original tune wasnt that bad anyway)

made a tiny difference (went from 300ks a tank to 350)

i think r33s are just thirsty cars

oh i have a 80ml throttle body as well on a forward facing plenum

[frozenwaffles]

Guys i appreciate the replays...thanks for that.

for the record so you guys know...

i do have a power fc and it was tuned by Tunehouse in marrickville.

i live in marrickville and work in botany with plenty of city driving, so i guess thats not helping at all.

i still would have thought for a 2.5l engine that it would/could have better fuel economy than that even with a tune and some power mods.

i guess my goal would be 400kms per tank around the city and 600kms per tank on the open road...

[MotoMan]

i still would have thought for a 2.5l engine that it would/could have better fuel economy than that

Heres your mistake.. its a 2.5l TURBOCHARGED engine

Check your tune... special attention to the AFRs

[Gazee]

I agree with Taso84, if you have a heavy foot and always coming on boost etc you'll get shit fuel economy.. i had 300km per full tank when my car was tuned with my safc... but that was cos i was always trying to come on full boost every gear lol when i cruise and change at around 3-4k i get 400km a full tank and my car is running so rich at the moment and i'm really suprised i get 400k's..

Just depends on setup, ecu tune and the way you drive is most important.. besides rb25's are known to drink a bit of fuel aswell... its a 6 cyl turbo after all..

[paulr33]

1) check 02 sensor on SENSOR SW / CHECK - see if its working - if not replace it

2) check cruise AFRS (not max load on the dyno, cruise afts) - if they are about right then its ok, if they are rich, lean them out a bit

3) make sure 02 feedback is on

4) drive normally, dont keep going on and off the throttle or boosting up the engine

[frozenwaffles]

1) has just been replaced and is working according to sensor check

2) what is rich and how do i lean them out?

3) feedback is on

4) i have a mixed driving habit at this point in time...

[32vspecII]

sorry didnt see you had power fc , has it been tuned ? check the cruzing afrs as paul suggested

i used to get 450-500km out of my r33 sedan , it was basically the same mods as you and pulling about the same rwhp

[frozenwaffles]

yeah it has been tuned, but maybe needs a leaner tune. i'd love those figures!

[JustinP]

I have the same problem in an R34 GTT, I get about 280-330km per tank highway (and I live inner city), and about 480km max ont he highway.

I replaced my o2 sensor with zero improvement. I brought a PFC which is on its way to me (mostly to hopefully improve fuel economy).

I really hope the PFC helps considerably with a good tune. It seems some other people are getting 400-450km's per tank when driving around the city with their RB25DET's.

I have *tried* driving off boost and more carefully which does improve consumption slightly, but the difference is not that great so I would rather just drive it to have more fun

It is obvioulsy running a bit rich as the rear ends up covered in a fine layer of sooty crap, although its not as bad as many of the cars out there (ie I don't really notice black smoke pouring out the back under hard throttle).

I just find it hard to beleive that a car made in 98 (and its the Neo which is supposed to be even more fuel efficient) would use so much fuel for the level of performance it puts out. When compared to some V8's with comparable power mine uses way more!

[tek_01]

i got 300kms out of 60litres last time i filled up

pretty shit!

afr are good, o2 is good..... just bloody waste too much petrol lol

[Dale FZ1]

^ so about 13.5L/100km's Dale? interesting way of quoting economy figures... most people will understand litres per 100km's..

If you're not giving it a lot of stick, 15L/100km is quite high...

Had to go check my spreadsheet. It's actually 7.6km/l which equates to 13.1 l/100km. That is the arithmetic average (mean) rather than the median.

I use km/l which is a measure of consumption, whereas l/100km is a measure of economy. Splitting hairs really because they just represent the same thing differently. FWIW, I also use the same spreadsheet to calculate the cost/km.

For a 1400kg car with somewhere in excess of 200rwkW, and self tuned light load AFR of a consistent 14.6 - 14.8:1 I'd still consider the figures pretty damn good. We are using a machine with basic mechanical and electronic engineering well over 15 years old. Not good to try and compare with what is currently on the new car market, but interesting. Remember we are driving a car that is a grand tourer, not an economy box; the figures are consistent, and still pretty good.

Edited February 14, 2007 by Dale FZ1