Undertuning A T To Run Less Fuel?

[Guest]

  mickq said:

Optimax gets MORE through the injector as it has a higher specific gravity and is more dense.

dw.... more dense = more thick

You fit MORE weight of fuel in a given space. As far as I know injectors inject a certain volume of fuel per pulse (and vary the rate of pulsing to vary the fuel amount they deliver), so with Optimax you will get slightly more bang in that squirt.

dw....thicker = less flow

that's why for a given driving style you will get slightly more kilomtres per tank on optimax.

dw....less flow = more k's per tank

Because we pay for fuel by volume, that means you get more bang in your tank as the weight of the fuel is higher with Optimax

dw....

- you get more combustible fuel "value" per litre (you could sort of talk in terms of more BTU's for those that know what that means).

dw.... btu's = heat produced and density is not directly related to btu's

The car can use very slightly less fuel per cylinder ignition cycle and still have the same fuel:air ratio. Modern engines will detect this, adjust their injector timing to suit (and possibly other parameters too like ignition timing due to the higher octane) and the injectors wont have to pulse as fast which means less fuel despite the same or better performance.

dw .... pls show me a car with a fuel density and or octane sensor!!!! the t does have a knock sensor to retard timing and a O2 to adjust fuel but not what your sugesting

Theoretically because of this you can slightly delay getting bigger injectors if you use a more dense fuel as it will get more power from them before they reach 100% duty cycle. Although I imagine in practice the difference would be quite small.

dw .... actually as I have shown it is the oposite the thinner the fuel the more you can flow!!!!

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mickq just setting things straight don't want people to be misinformed!

no offence intended

[BLK6T]

I think a T is not for you then...if your main concern is the $$$ of petrol and if its really burns a hole in pocket. By the looks of it petrol wont drop and just keeps going up and up. Maybe a more economical vehicle. Although it would be hard to not drive a T.

[benmwhite]

As an engineer, there are two things I appreciate; power and efficiency. The phase II has delivered 280rwkw on tap – sensational! But the increased fuel economy has been a side benefit that I wasn’t really expecting.

On a recent trip down South, the ute delivered 7.3litres / 100km. With a plane to catch and not much time up my sleeve, let me assure you I wasn’t sparing the ponies either!!! An identical trip under similar conditions pre-phase II saw the ute slurp away 13.1 litres per 100km.

I should add that this has also helped justify the outlay particularly if you ask my wife...

...just dont mention the additional rear tyre wear!

[Cro]

  benmwhite said:

As an engineer, there are two things I appreciate; power and efficiency. The phase II has delivered 280rwkw on tap – sensational! But the increased fuel economy has been a side benefit that I wasn’t really expecting.

On a recent trip down South, the ute delivered 7.3litres / 100km. With a plane to catch and not much time up my sleeve, let me assure you I wasn’t sparing the ponies either!!! An identical trip under similar conditions pre-phase II saw the ute slurp away 13.1 litres per 100km.

I should add that this has also helped justify the outlay particularly if you ask my wife...

...just dont mention the additional rear tyre wear! 

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Being a PhaseII you will have different larger capacity injectors.

In this case the ECU driven Litres per 100kms and Range will be totally unreliable.

[Bain]

  BLK6T said:

I think a T is not for you then...if your main concern is the $$$ of petrol and if its really burns a hole in pocket.  By the looks of it petrol wont drop and just keeps going up and up.  Maybe a more economical vehicle.  Although it would be hard to not drive a T.

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How is a T not for me? Just because I dont feel like wasting 16 - 18litres a fuel per 100km's on work doesnt mean I dont want to use the same amount on a weekend putting other vehicles in my rear view mirror..

If I can use the EDIT to save a few bucks every week, it then allows me to do more mods to the car down the track from those savings..

[F6 UTE]

When I travel 66,000 k's a year, a 20% saving on fuel bill is more than enough to pay for the edit alone.. especially at 450k's from $80

even if I don't pay for fuel........ someones saving money..

[Lawsy]

People should look at it this way.

He wants an edit; he requires more power for the weekends.

He also wants, as a side benefit, seeing as there are no other engine modifications being made at this time, better economy during the week. Seeing as the engine itself is standard, it should be able to produce better economic figures than the factory state of tune, if the ECU is programmed specifically for that engines character.

I think that sums up what he is trying to get at.... He wants to save money during the week in order for him to use it up on the weekends.... Or even have a net saving (in the long term) if hes lucky...

Either way, what street tuner said sounds interesting and you guys should probably look into it....

[LightningXR6T]

  Eugene said:

  Geeseman said:

In city driving the XT falcon uses 400-450km per tank.

Get used to the fact that the XR6T uses fuel. Fuel=power.

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It all depends, my auto ute, not much crap in the back too often, around town 595-610km per 70 lts

on the highway, say a run to coffs and back from newcastle 740-780 km per tank.

on my xede I have amap that runs the car reasonably lean between the revs of 1800 and 2600 and 10-30% throttle opening, lower boost to, still 7 psi but not 11psi like the rest.

this allows the car to have a AFR of around 13.9:1 when cruising, factory it was 10.2:1, so I save about 35% fuel, if I put my foot down to overtake, the tune is set to add fuel allong with boost as revs rise, its AFR return to 12:1 nice and safe.

Tthis works a treat with the xede causer I can flick the switch and have 290rwkw or run my in town tune(also my wet weather and wife tune) and have 245 rwkw and great economy.

I am sure you could do it with the flasher, just a pain to upload a high output tune if you want to show a Expensive Daewoo driver a clean set of heals.

Have fun.

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Ive just moved from a AUII XR8, to a XR6T MKII. From the above figures they seem fine as even the AU would not get these and certainly wasn't as much fun as turb!