Poor Fuel Economy...please Help!

[frozenwaffles]

Hi guys, so i drive an R33 gtst 1995 Series 1.5.

my engine mods are as follows:

Apexi Power Intake

Apexi PowerFC

Apexi PowerFC Boost control kit

Z32 AFM

Cooling Pro Intercooler Kit

Cooling Pro Oil Cooler Kit

HKS GT-RS Turbo Kit

HKS Exhaust Cam Gear (set to 4deg retard)

HKS Timing Belt

Splitfire Coilpacks

HPI Exhaust Manifold

Xforce 3.5" turboback exh, with bell mouth dump

Datalogit

PLX wideband AFR Kit

ok so here is the go:

i do all my own tuning, i tune to the following:

14.7-15 afr on light load (basically rows P8 and less)

then as boost comes on we go to 13.5 and head down to 12 afr when we hit full boost at 1bar...

city driving i get 300kms to around 50 litres, thats 16l per 100kms...shithouse if you ask me.

i wanna see 400kms to a city tank!

110km/h i see around 500kms to 55litres roughly and around 400kms if its 80-110km/h long distance work...

i have cleaned everything, AFM, plenum, aac valve and associated parts....checked base timing (19deg indicated - 4deg retard on the cam gear = 15deg base timing) etc

where do i look now??? engine rebuild...lol

[Guilt-Toy]

your economy seems about right mate.. mine gets 300 - 350 with city driving max... add highway i get 400 - 450

what timing are you running on cruise? have you locked the timing to the ecu correctly?

[MBS206]

Guilt Toy, can you post up some info on how you tune your car, like target AFRs, some advise on timing advance etc.

I'll be tuning my skyline in the new year (25/30 with an alright sized turbo) and want to know how lean you take them on cruise (Say sitting on 100km/h in 5th etc) and what sort of timing you have dialled in.

[rev210]

make sure your O2 sensor isn't shagged if you are using closed loop, it helps.

[Moodles2]

Does your oil cooler has an inline thermostat? Might be causing to make your engine warm up slowly

[frozenwaffles]

a couple of updates guys (cant see the 'edit post' option)

I also have NISMO 555cc injectors (pfc correction: 66.6% and +0.19ms)

oxy sensor (NB) is working fine and only 20,000kms old.

oil cooler has no thermostat but car warms up in 5min average plus i have almost no light load correction from 50deg up water temp and i have also reduced the 50deg up on the high load but not as much as the low load.

timing is locked so that power fc sees 15deg or displays that and indicated on the crack is 19deg (but you have to minus the 4 deg on the exh cam gear, so we end up with 15deg)

timing on cruise is around 40-48 deg, onc e we hit P8 and up it drops to the 30-39 range and from P12 down we go into 20s and drop down to 10s

[R31Nismoid]

Its the way you drive, simple as that. If you hit boost, you'll hurt economy. If you use a lot of throttle (even off boost), you'll hurt economy.

I kid you not, drive around off boost, partial and steady throttle application upto the speed limit, you'll see 400km to a tank without even realising.

I can do 400km to a tank city driving no problem with 250rwkw, i expect that to be the same with 330rwkw or whatever other figure i end up with as the driving style is the main dictator.

However if i can just as easily make 200-300km to a tank city driving in a blink of an eye. Simply coming up onto boost from each take off will do it over the course of a tank.

I see 550 easily on the freeway, im sure i could get 600 if i really wanted too... however if i mash the pedal that goes out the window in the same manner as city driving

[zebra]

Have you had a play with the Throttle enrichment (where it squirts more fuel in on throttle opening) and decrease that till the car coughs a little on throttle opening then increase it ever so slightly until it runs fine again.

There a gains to be made by doing this especially in city driving.

[frozenwaffles]

yeah playing a bit more with that now.....

[frozenwaffles]

ok so another thing guys.... whn on idle i have an afr of around 14.7-15 and i can smell fuel....but only on idle...any ideas?

fuel lines have all been replaced in the last year...

[paulr33]

there is no problem

if you were getting sub 200kms to a tank, then 02 sensor or fuel mapping is toast

over 300kms to a tank is fine. stop loading the engine up and stop bringing it on boost, problem solved

if you dont believe me (or others who have said the same) give your car to your girlfriend or mum to drive for a week

i bet they get over 400kms to tank

also what do you classify as "to a tank" are you measuring the same way each time

do you run it empty? do you fill it up to the top? how many litres do you fit in when you "think" its empty

the gtst fuel gauge goes past E before you are empty and then the idiot light comes on

the difference between near E and past E is around 40kms (at least) of light cruise

[Turbotonic]

im getting 350km city driving in a single tank, 450km highway driving, well fuel is still going cheaper so its all good

[frozenwaffles]

ok just for everyones reference...300-350km to 55 litres. thats between 15 and 18L/100kms... pretty shit if you ask me.