Crap Fuel Economey...

[Cubes]

TommyK,

Sards are generally known as squirters, are they the new 2 and 4 pintles?

Big injectors will always have issues with atomization at low rpm.

[Tommyk]

nope these are the single squirters ?

Makes sense as the injectors are probably a tad too big for the car in its current form

[Josh]

Is the fuel light on the fuel gauge? maybe mine isn't functioning...

Sorry to hijack..

Do you reckon I should check my injectors? maybe as part of my 100thou service.. I get about 350km to a tank

Also I have noticed that the car runs pretty rich - apart from the obvious poor fuel economy - after having my zorst modified, the car will occasionally let out quite a big backfire... and it will pop quite a lot... what do you guys reckon?

[Josh]

On the subject of the light - maybe I have never been empty enough for it to come on..

[justin911]

how do you guys know when the closed loop thing is in operation ?

[Tommyk]

shows as 0% injector duty cycle on the hand controller for the power fc

[justin911]

ooh cool thanks, i'll look out for it 2nite

[Cubes]

To see closed loop mode operating head to the etc menu then sensor check.

Look at the o2 value. It will cycle up and down from roughly .2v to .8v.

The injector duty on my pfc h/c stays at low values while in closed loop mode, it only ever reads 0% when the car is off or when deceleration fuel cut is active. i.e using gears to slow down with rev's greater than approx 1500rpm.

[Tommyk]

cubes - youve confused th e hell out of me

i thought closed loop was when "i.e using gears to slow down with rev's greater than approx 1500rpm"

tell me more please

[justin911]

so basicaly if the o2 sensor is going up/down.. and the injector duty is quite low then its in closed loop ?

To see closed loop mode operating head to the etc menu then sensor check.

Look at the o2 value. It will cycle up and down from roughly .2v to .8v.

The injector duty on my pfc h/c stays at low values while in closed loop mode, it only ever reads 0% when the car is off or when deceleration fuel cut is active. i.e using gears to slow down with rev's greater than approx 1500rpm.

<{POST_SNAPBACK}>

[RB30-POWER]

Closed loop is when the ecu is using the Oxygen Sensor Output to control fuel mixtures to a ratio of 14.7:1 or stoich. This increases economy and allows the cat to give the cleanest output from the exhaust.

It is only used under light load and throttle driving conditions.

Should be in closed loop on a standard RB up to 0 Vacuum.

Modified engines it may be different.

[justin911]

hmm i think i get it.. why do people play with there light load settings in there ecu's though if the closed loop thing takes over ??

Closed loop is when the ecu is using the Oxygen Sensor Output to control fuel mixtures to a ratio of 14.7:1 or stoich. This increases economy and allows the cat to give the cleanest output from the exhaust.

It is only used under light load and throttle driving conditions.

Should be in closed loop on a standard RB up to 0 Vacuum.

Modified engines it may be different.

<{POST_SNAPBACK}>

[Cubes]

cubes - youve confused th e hell out of me

i thought closed loop was when "i.e using gears to slow down with rev's greater than approx 1500rpm"

tell me more please

<{POST_SNAPBACK}>

Sorry Buddy, I was refering to the 0% injector duty cycle, the only time mine reads that is when decelerating, when decelerating the ecu cuts fuel, its a little feature new cars have to save fuel and apparently wear and tear.

Closed loop generally is used up to around 30-40rwkw's. Then it drops out and uses the map.

To furthur aid fuel economy you can play with that area of the map and tune to stoich (14.7:1) until the ecu see's 0 vacuum.

Edited October 11, 2005 by Cubes

[RB30-POWER]

The reason is, because,

The ecu can only add like + or - 5% of injector pulse width or "on duration" from the base pulse width which is programmed into the light load map points, when the unit is tuned.

Like if the base map figure was 2msec duration, but to acheive a stoich ratio of 14.7:1 it actually really required 1.2msec, the ecu can't adjust add or subtract that much from the base value.

The reason it can't is because, if for instance the O2 sensor was faulty and gave incorrect readings, the ecu could adjust the injector pulse width to whatever gave the output, it thinks is correct. But really it isn't because the O2 sensor is faulty.

Even if you tune your base map settings to exactly 14.7:1 mixtures, when you get different fuel, different temperature days etc, it will never be exactly 14.7:1. But closed loop allows small adjustments to keep it at that output for economy and emmisions.

[benl1981]

What I'm curious about is why there is much difference between cars...

Assume you don't gun it much at all, it should be in closed loop say 80% of the time..

Now the the 02 sensor should be doing most of the work and the ECU adjust fuelling to get to 14.7 AFR. So a slighlty misreading AFM shouldnt affect fuel economy. It is then down to throttle application (If engine is worn takes more throttle to maintain same speed), wheel alignment, tyres but thats about it.

I used stuff all throttle and on the highway still only got 11L/100k!!! What is the go!!

[RB30-POWER]

Possibly, dirty air filters, filters sucking hot air from underbonnet (typically applies to pod users), retarted ignition timing, spark plug condition, viscosity of the engine oil, engine temperature, age of 02 sensor, restricted exhaust.

All those types of thing can and will effect economy.

So best check that its all up to scratch, before you really worry to much.

[benl1981]

Yeah done most of those. I have new high flow panel in stock box, Ignition timing is 17 deg BTDC (15 is in manual), spark plugs new about 3000km ago, oil 2000kms old (10w 40 I think), 02 sensor is old I think, exhaust full turbo back 3", engine temp always in middle gets up there quik enough to not warrant repalcing thermostat. Fuel filter about 20 000km old.

If a fuel filter is partially blocked though I would think it may hesitate or lean out on boost. At stock boost it was going to 10:1 AFR. Also a blocked fuel filter would mean that there would be less flow through injectors right if causes pressure to drop?

[Cubes]

Injector condition? Vacuum leaks?

How does it start first thing in the morning? Splutter at all?

[RB30-POWER]

Are you still running standard ecu or the powerfc?

You drive with aircon off?

[benl1981]

Can't hear any vacuum leaks. I have ran some injector cleaner through (Redex). Starts easily in the morning, no splutter at all. I dont sthink it warrants ripping out injectors to clean at the moment - I am hardly using any throttle application to go anywhere so it's not as if they are a problem I think, no hesitation or missing. If they are flowing a little less than they shoul this would = less fuel - better consumption..unless leaky injector which I don't think I have.

This fuel econmy was on stock ecu and boost but I now have PFC and getting it tuned Saturday. I think it is using a bit more with PFC but I am running 10psi and tested it a little more lately (Not reving past 5500rpm though - still on base map)..Knock is below 32.

My fuel economy isn't as bad as what some report but still I reckon should be 10-20% better. On the highway I had aircon on for quite a bit - most of the time I have it off though.

I drive to work for about 15km - half of which is no traffic lights constant 80km/h and I get about 12L/100km. On a highway trip it is about 11L/100km

Thanks for the ideas.. Any others??

Edited October 12, 2005 by benl1981