poor fuel economy. j-spac vr4, 3" tbe, bov only mods

[milkandoj]

Hey just bought an 87 jap spec vr4, and i love it.

only prob is it loves a drink, i got 320ks from first tank of 60L of 98 premium and now looks like second tank will get around 350.

I assume it needs a tune of some sort of engine management.
I want to keep mods at the level of exhaust and bov which i have and add....intake mods (how good is the stock intake, is it good enough to just replace the air filter i read on here k&n do 1, as intake doesnt look like has many narrow kinks), and computer for now.
And i want it to be better on fuel as its my daily driver!

From my engine management i want to have good fuel and prob low boost for dialy driving and be able to switch to a more fun setting when i wanna have a squirt.


What works for ppl?

Addmitidly i have been sinking the boot in a bit as just bought it but still that equates to 18l/100k which is a fair bit.



Heres some of what ive observed and what i assume.........

Its only got a 3" turbo back exhaust, and an adjustable bov (adjusts from plumb back to venting into atmophere). Ive put the bov to plumb back most the time as form what i know it should stop the dumping of excess fuel when i back off to change gears.

When i have bov set to full venting externally and bive it a rev in the drive way it spits a fair bit of black liquid from the exhaust.

From what i know when the bov vents into ouside air- (correct me if im wrong) i assume the black liquid is part of unburtn fuel as the computer is over fueling the car briefly as the air's been measured then dumped ourside the intake. so there's less air in the intake system than the computer thinks) doesnt smell like fuel tho and washed off my white pavers pretty easily so assume not oil.

When i have bov set to plumbing back into intake its doesnt spit much or any black liquid, so i assume its fuel. And its still using heaps when its set to plumb back most the time.

 

[to4garret]

the black liquid you are talking should be just water vapour and soot spitting out. nothing to worry about its quite normal with turbo cars.

320-350kms i would say i quite normal too, if you do a lot of start stop driving its more so, if you are doing a nice open road drive then it should be around 450kms on a tank.

you cant tune these when they're stock as such, the ecu tries to adapt as best as it can, but the O2 sensor would probably be stuffed as thats one of the least replaced parts of the car that affect fuel economy.

as far as tuning goes, new leads, plugs (gapped properly), oil/air filter and a change is about is far as you can go.

performance comes at a price

 

[milkandoj]

soz about the long question...
Basicley where should i start with improving fuel economy and what ecu's are the go, i been looking as posts and wolf seems to some up a bit

 

[to4garret]

where should i start with improving fuel economy

after doing what i mentioned before...

with your right foot, or buy a 1300cc daily, sorry but its true.

to make power, you need to burn two things, fuel and air, more fuel and air equals power. the stock ecu however does run fairly rich on WOT (wide open throttle) this is by design, aimed at protecting the engine.

to me it sounds like your car is fine.

just be a little lighter on the pedal, its not a CC Lancer with a 1.5 carby that needs full throttle to get to 50kms

that will net you better kms

 

[milkandoj]

Cheers for the reply.
just seemed lik alot of fuel for a reasonably stock car :? compared to mates turbo cars (maily skylines).

The iridium spark plugs are apparently pretty new. the cars only done 64K and i believe this is true as its a plumb, air flow metere could be stuffed through age tho.


Im my budget of around 1.5k but keeping below say 2k on engine modds on top of what i have ( bov, exhaust) what am i best doing?
I read a tuning guide on the 4g63 in "speed" mag and all 4 companies tuning packages under 5k, all they have on top of what ive got is some type of piggy back computer and boost control.
(crydon uses uni chip and boost control, avo use SMT smart tuner and dont touch boost, morpowa use uni chip and boost control)

The articles is aimed at the 4g63 as a whole but the prob talking more about later models so im wondering what appickable to my jap spec vr4 motor

 

[to4garret]

are you worried about fuel economy or performance thats the next question?

if you just want better economy then thats a different ball game, after market ecu and a lot of tuning time (1k+) or a $300 shitter out the quokka.

if your after performance, its a pretty tried and true recipe, 16G or 20G turbo, reasonable size intercooler, 2" or 2.5" off the turbo through to the throttle body and as much boost (probably 15-17psi) as the stock ecu will take, combined with a nice exhaust will net you some decent'ish power.

you should come over for a beer sometime

you NOR or SOR?

 

[milkandoj]

Cheers heaps for ya reply, i learnt alot about liberty rs's on forums a yr ago when i was looking at them, im kinda in the dark on vr4's atm.

ive already got an exedy clutch and g4 adjustable coul overs also (which i've gotta serch for the owners manual for, so i can understand better how to play around with them properly). so now im just looking at the engine

Want a bit more squirt but when cruising to be easy on fuel, i do understand more power equals more air and fuel.
Thats why i was thinking boost control.

Also my number plate covers almost all of the stock intercooler, i was thinking of moving it but dont wanna drill holes. is it worth the hassle

 

[to4garret]

i just brought a set of G4's, they should arrive tomorrow actually

from what i have seen, moving the number plate to the side is the best bet for additional cooling without cutting stuff up.

this is a good forum, for mild mods you can get a lot out of a VR4.

why were you thinking boost control?

you cant go lower than the wastegate actuator setting (8-12psi) unless you disconnect it completely :?

 

[milkandoj]

The basic ideoligy of what i want is;
I know more power = more fuel when ya boot it, but with the modds i do, i like same or better fuel consumption for cruising around, but do deffinitely want more squirt when i give it some.

If i went a bigger version turbo, if it didnt chew more juice cruising (tho i like to give it stick coz i just got it), and i could do it under 2k with supportin mods id do that. But if suing stock computer still without piggy bank, tuning wont be great will it?

Other wise work on what i have, its runnin stock boost so surely theres some head room and maybe invest more in engine management.

Also k&n filters, they use filter oil to trap dust, correct? Apparenly this kills the AFM on wrx's pretty quick, prob sam for my car?
if so whats the best bet as i read on another thread ppl sayin k&n is only mob who make one to fit.

I could always make my own air boz but looks lik id have to move battery to boot and would AFM be arrurate if i used diff size pipe and flow charicteristics form say a pob in air box.

 

[milkandoj]

soz im a post behind, wanter boost control so have low/stock boost and hi boost when its fun time

 

[to4garret]

you should come over for a beer sometime

you NOR or SOR?

thats probably the easiest answer

shoot me a PM.

 

[milkandoj]

lol ya ok pm senr cheers, i got tooo many q's

 

[jdm-vr4]

look into getting dsm link from us, they awsome for our cars and very easy to tune

 

[rob323]

A couple typical culprits for bad fuel economy:
A dud O2 sensor,
A dud water temp sensor.
Bad economy when "on boost" is usually due to intake leaks (and slightly due to the overly rich fuel mixtures programmed in the ecu).

 

[tUfRiCe]

sorry to rain on parade but buying a performance car with a view for more power is insanely naive to also want fuel economy you need 2 cars... daily and weekender

 

[milkandoj]

What i was saying about fuel is, when im driving around just to get from a to b i dont want it to chew more fuel as i modify it slightly or maybe use less fuel as i derestrict the motor like doing the intake ect and tune it better, coz mow its modifyed, if only slightly, the stock computer is tuned for stock and wont be tuned the best.

I know when driven hard its going to love a drink!

And the first 2 tanks when ive given it stick im getting worst than a mates 350hp skyling thats a bigger motor and 2 extra cylinders and makes more power when driven hard so i was questioning why mine uses a fair amount of fuel when im not making much power.
i thought mine mould use a bit less fuel than his even when giving it stick.

I wasnt comparing apples with apples i know, thats why i asked here

 

[tUfRiCe]

i have an evo1 with relatively minor mods an im pretty happy when 350 ticks over

 

[rob323]

A stock to mildly modified vr4 (exhaust, 16G, chip, walbro, 15+psi) should get close to 10 litres per 100 km when highway cruising.
I can easily get over 400 km per tank when doing Touring Road events (which is mainly "spirited driving" and full noise during the performance tests).

If you are getting less, and it bothers you, then you have to start looking at the possible reasons why the ecu is dumping fuel in.

Oh, and work out your fuel consumption in l/km, its alot better an indication than km/tank.

 

[iluszn]

this is a good trick.

Go to bunnings.. Buy some wood.
Place behind petrol pedal..

DONE!!

Well i couldnt tell you how much juice these things drink near factory.. my previous cars have not been near stock.. But 400km should be average i would say.

 

[Entaran]

I haven't read the thread to check but the answer to this is simple.

A J-spec (prefacelift) vr4 running 11psi of boost with very minor mods should return around 460km/tank with average amount of leadfoot. You can drop it to as low as 260 if you are HEAVY on the pedal.

Your O2 sensor is probably shot = rich all the time = fail on fuel economy. Get a mate to drive behind you and see how much black shit is shot out on boost. Should only be a puff as you HIT boost, not constant. O2 sensors are always the culprits.


---

My jspec prefacelift used to return consistent 10.2L/100km city, 7.1L/100km country with exhaust and 11psi boost. No other mods. Anyone who's seen me drive or been in a car with me knows I don't drive like a grandma.