Injectors And Fuel Consumption

[Italiazr1]

I have 660cc denso injectors im pushing out 220rwkw

but on normal driving im only getting just under 300km per tank

i know i went over kill on my injectors but do you think if i went the gtr injectors

it would be worth it Would i save more fuel or will it be the same still?

Im running a wolf ver 5

[extreme turbo manifolds]

im no expert with the wolf but id say your fuel consumption has to do with the fuel mapping rather than the actual injectors

[Dale FZ1]

The injectors are way overkill for the power you are developing. What is your power target?

Obviously it would be easier to achieve fine control at light load with smaller injectors, but I'd suggest two main culprits:

Your light load AFR

Your driving style. Use lots of throttle and a bit of rpm, and you will use fuel; it's that simple.

Injector sizing may be a small part of the issue, but I'd look at the other two as the main cause of fuel use.

I have similar max power to you, but consistently deliver 400-440km per tank (50-52 litres to fill).

cheers.

[Italiazr1]

What do you mean by light load air fuel Ratio

is that a tunning thing?

[Italiazr1]

im targeting 250rwkw

[Dale FZ1]

660cc injectors are overkill for that power requirement. Most guys on SAU have had good results with 550cc which will more than feed what you want. However, run what you have, and aim on good consistent tuning.

Here's a development log I made in the past week:

Pretty self explanatory, with the numbers being average AFR:1 logged during a run, with O2 feedback turned off. My target from P3 - P9 load is 14.7 but I tolerate a variance of between 14.6 - 14.8. Extensive data logging has shown that you do get variance from run to run, but multiple variance analysis shows that over the long run it is fairly tightly controlled. There is a bit (lot) of mucking around to achieve the consistency though.

I'll pull up a shot of injector duty cycle too, just to demonstrate how much increase you get with load.

[Dale FZ1]

Check out how fast the flow requirements ramp once you load the engine in any rpm range, and if you keep sticking the revs into it. And if you've got more power, then you're going to use more fuel.

If you want economy then you need to keep it in that light load zone.

So the answer remains the same:

mechanical spec (this includes injector flow rating) will play a part, but not as big as you might think

tightly controlled AFR is important (yep, tuning)

controlled use of the throttle is the major factor

Hope this helps.

cheers

Dale

[Italiazr1]

ok i will tell my tuner to look at it

[tek_01]

i get about 300km per tank (55-60L to fill up)

afr are at about 12 on the dyno. standard ecu with a fuel cut defender

new spark plugs, all filters and oils.

crap isnt it?

[Dale FZ1]

Not really, given the design and intended application - and how it's driven. It's just what they do.

[scarface]

i got 800cc injectors an 250kw at wheels, and on normal driving boosting every now and then i can still get 360kk's on a tank

[Guilt-Toy]

I got 430rwhp with PFC & AFM with Nismo 740cc injectors and on my last RTA Emissions test it recorded 11.8 litres per hundred which is over 500ks to a tank (60 litres) it did fail the emissions test because i tuned it to run good on fuel.. now after i retuned it it uses more fuel then before (keen to pass this test)

So yeah you can have big injectors and get good fuel economy. maybe its the computer that cant handle the injectors properly i do keep hearing that apexi power fc's handle big injectors well so that may be why mine is the way it is.

[Italiazr1]

im getting my tuner to have a look at my cam timing cause he thinks its reterded a fair bit

im not making good power for what i have in my car and its all possibly related i will let you all know how it goes

its going in next monday