Fuel consumption and How-to save fuel...

[CMF_Toma]

Hey all,
Im thinking I can get alot more out of my tank.
Im only getting 450-490kms from 1 tank on a standard Super S.
I do quite a bit of freeway driving i spose, but i was hoping 500kms could be an achieveable target.

Is there anyways (cheap) to get better fuel economy?

Heres a few ones i thought of.

1. Remove the spare tyre.

2. Thinner + newer engine oil?

3. Newer fuel filter?

Please add some other ideas, if you can think of any! Remember, cheap. No point spending $500 for a lightened flywheel only to save $0.10 a week

 

[CMF_Toma]

Oh also,
When i had my Mini, I read about someone lightening a mini by drilling 100's of holes thru the chassis that didnt need structural ridgidness... Is this madness?

The article said he lost 100kg on a Mini, bringing the weight down to something insane like 300-400kg. Imagine the power/tourque ratio on that! :O~

 

[CMF_squigbobble]

Reducing the weight won't make much difference when travelling on the level at high speed as aerodynamic drag dominates. I was going to suggest getting one of the factory spoilers but the Super S already has that, it's possible that one of the smaller ones might reduce the drag but, then again, it could increase it. One thing you can take advantage of is the fact that drag increases with the square (or the 4th power, can't remember) of the speed so at high speed any reduction in speed will give a proportionally larger decrease in drag. Try driving 10 or 15kmph slower (when you're going at a steady speed) and see what difference that makes.

P.S. You're on the right lines with engine oil and filters.

 

[CMF_Yom]

What fuel are you running it on? And how much fuel can you fit into the tank when you've travelled 450km or so?

With my first tank I did 400km on ~35L of BP Ultimate. I think that is around 11km per Litre. Which means I had probably another 100km left in the tank, if the tank was originally full with 42L of petrol (according the manual).

I think that is pretty good considering I was driving it quite spiritedly with alot of stopping and starting, with the aircon on!

Plus lets not forget my big heavy wheels and power steering using just that tad more petrol...

I have a suspicion the cold air intake will improve fuel economy a bit more as well.

Let us know how you go. I'm interested in seeing if I can achieve the advertised fuel consumption figures!

 

[CMF_Toma]

Yeh, wheels make a world of difference. I got new tyres last month and started saving fuel right away. I used to only get 430-470kms per tank with slightly bigger tyres!
Im guessing you need the original tyre size (oh so skinny) to get an awesome fuel saving car.

Nothing but BP Ultimate or my favorite, Caltex Vortex.

Saves money + pollution + engines + babies.

so,

4. Thinner/More standard tyres,

5. Better Fuel

 

[CMF_fred]

i have a lightened flywheel and cold air intake and my best fuel consumption is 53mpg (work it out the new figures, i'm to old)....
ways to improve fuel economiy....
use the narrowest tyres you can buy (less frontal drag and rolling resistance)

roll whenever you can (up to lights, down slopes)... sometimes you may get a nasty look if you roll to long towards lights.....

cheat... let some air out of your tyres (reducing effective tyre diameter) always check before you get into a cab to see if the tyres are up... the meter goes round quicker...

of course some of these ideas may not be practicable!

 

[CMF_Yom]

I've always found the better fuel economy from properly inflated tyres.

I think you'll find the drag from the increased surface area they take up negates any benifit from a smaller rolling diameter.

 

[CMF_micra-man]

Autospeed have a good set of articles. Do a search on "Savings on Fuel"

 

[CMF_queazocotal]

Other thoughts.
All else being equal, you get best fuel economy at the lowest engine RPM and highest gear that can cope with road conditions. Keep the gear as low as you can.
IC engines are most efficient at full throttle.
If you are accellerating once to get up to speed, then do it relatively hard, till you hit maybe 50MPH in 5th.
(what is the optimum speed?)
Of course,in stop-go traffic, accellerating hard does
not buy you anything.

 

[CMF_55bhp is more than enough]

practically all you can do is get rid of all the crap in your boot that you dont need. drive at around 55mph, never accelerate uphill(try building your speed up before the hill and keep a steady foot up it. try not to accelerate hard, build up speed gradually. clean your car and polish.

stuff like geting thinner tyres and cutting bits out from your car is a bit extreme, if you do any of the above you should notice a difference. the bes one is driving at bout 55mph in top gear, this is when your engine will be the best comprimise between fuel consumption and speed.

oh btw i drive about 2 hours on the motorway everday and i can average bout 50mpg

 

[CMF_nz_aj]

Around town Auckland (=hilly), short trips, 6.4L/100km = 44mpg on 95 octane fuel.
Lightweight, skinny biscuit tyres make a lot of difference. Over inflating tyres helps (maximum pressure written on tyre +10%) This usually comes out at 40psi or more, although I might be more cautious with road temperatures in Australia.
Gentle acceleration / braking, coasting in neutral if possible & large following distances.

 

[CMF_queazocotal]

Hope to have some hard numbers soon.
I've connected to the blue wire on the ECU output a wire, which tomorrow I'm going to connect to a laptop soundcard.

The injector timing, combined with GPS, will hopefully allow accurate moment by moment fuel consumption to be calculated.

 

[CMF_Yom]

Oh yeh,

use 30mls of Morey's Upper Cylinder Lubricant everytime you fill up.

It is good stuff from our friends in the fridge! Oh.. hang on.. no, New Zealand. yeh thats it. New Zealand.

Cheers

 

[CMF_Toma]

Giving this a bump.

Just filled up and ~35L cost me $53!!! Out-freaking-rageous.
Its from a pricy BP and still going the BP Ultimate at 147c/L
Just a taste of things to come!!! Doh.

Is that Upper Cylinder Lubricant any good Yom? Would the cost of a bottle outweigh the cost of the saving? Just read a little article about it, do you need to KEEP using it? Or is it a 1 time treatment thing?

Theres no way I'd spend a whole lot of money on lightening a flywheel just to save $0.50 a week.

On this $50 tank, ill be limiting myself to passing 3000rpm wherever possible and then see what kind of saving i can make. Do you think a cheap Shifter Light could help here? (Me thinks so!)

 

[CMF_Yom]

I keep using the Uppercylinder lubricant and I always make sure I use the correct amount for the fuel i put in. too much and you'll be driving around puffing thick white smoke. But yeh I use it because 1) it keeps the fuel system in good nick and 2) it reduces valve and cylinder bore wear. Its very cheap for what it is and how long it lasts so I'm not really complaining.

Keeping the fuel load under half a tank is good for your fuel economy and performance as well. Only time I fill up is when i see the 98ron very cheap (under 134c/L).

Shift light will just be a wank mate . When i had a laptop hooked up to my ECU I was reading the injector cycle voltage and I found there was stuff all different between 3000rpm and 4000rpm. Labouring the car under 2000rpm uses more fuel than changing gears at 3800rpm. Soft throttle movements also kept the injector cycle very low. Engine braking uses less fuel than idling (injector cycle goes to 0v). Also going down hills I lift off the throttle completely. If you start to slow down, shift into the next higher gear.

If I didn't care about holding up traffic by doing around 90km/hr on the highways or speed at 65km/hr through residential areas I would quite easily achieve 5L/100km. Possibly even lower if I put some original cheese cutter tyres back on.

 

[CMF_White Knight]

Well it all depends on how you drive.How you control the foot on the gas pedal is the key factor.Yes keep your tyres correctly if anything slightly over inflated, accelerate slowly and smoothly. Anything else you do will only be marginal.
Yeah Toma costs over $50 to fill up now when running BP Ultimate !!

 

[CMF_micrat]

I live in perth too so propably travel similar roads. I have a super s with 16" wheels and usually get just over 600km to a tank. (fuel light usually comes on after 510-530km) The best economy I have ever gotten was 700km from 1 tank. These km figures I have quoted are from the tripmeter/odometer which actually reads low due to the 16"s, the actual real distances travelled are approximately 6% more.

 

[CMF_Toma]

Wow! i get exactly the same with 13" stock wheels :/ Lots of freeway driving too.

 

[CMF_Toma]

Ok,
1 week after driving like a nanny and Im amazed at my fuel consumption! After getting a theoretical distance of ~650km per 42 litres, I can now get ~730km per 42 litres. Quite a hefty difference really. I can now comfortably go 600km from 1 tank without worrying at all about filling up.
'Fuel Prices Soar' for one day? Stuff it! Ill fill up next week instead

After telling my g/f and her friend about it they say "I hate you." Which is what I tend to get as I keep rubbing everyones noses in my fuel consumption. My boss even said to shutup after he told me about his 11L/100km Ford XR6. Oh how i love my Micra.

 

[CMF_nzallblacks1]

what premium fuels are the best?

i guess the main three options would be caltex vortex, shell optimax and bp ultimate. any difference, or are they all similar?

 

[CMF_Toma]

I always use caltex vortex because its usualy cheapest premium you can get. BP Ultimate seems a little better for overall distance but i only mean by maybe 10-20km.
So id recommend Caltex. Even tho they are rip-off merchants.

 

[CMF_Brendon]

why you bothering??
its a micra they run off a sniff of a rag.
gladly drive your micra hard and you can still laugh at everyone else filling up bigger cars.

 

[CMF_Sean]

Caltex and BP fuel comes out of the exact same depot...

The only difference is Vortex has one extra additive compared to Ultimate..

And that additive is to *try* reduce carbon build ups in the combustion chamber

There is no difference between the two fuels other than branding

Sean

 

[CMF_Toma]

Wow! Thats interesting Sean.. Maybe it was a just a psychological thing with the fuel saving i got, or drove a bit further.

Brendon: So you can rub it further into peoples faces about how super Micras are

I filled up the other day and noticed a big black Holden commodore filling up his tank... Was there before i started, and was there after i paid and was leaving. Poor bloke. His car really was 1/2 the size of a small house. (Probably cost the same too.)

 

[CMF_robo]

When does your fuel light come on? I have yet to see mine light up.
I normally get about 380-400 Km's out of a tank before I get paranoid since my fuel gauge is reading under empty, but when I fill up, I can only put 30-35 litres in, meaning I still have 10 or so litres left in the tank.
Anyone else get this behaviour?

 

[CMF_evade]

hrmm, i guess I do alright then on fuel considering the turbo and all that stuff.

my fuel light doesnt come on now till at least 450km and i end up filling up bout 35ltrs.

141c is a killer. its even worse when normal unleaded is 146c so ultimate is like 155c.

good ol deceleration fuel cut. as yom said its better to use the engine to brake, uses less fuel than idling

before i had my tune on the ecu fixed up it actually wasn't doing this..resulting in some really crappy figures. most i'd use to get is about 330km a tank. big difference..

the fuel debates always interesting to read though

 

[CMF_Yom]

Only trouble with ye old compression braking fuel cut etc is that it puts more wear on your clutch and engine. Is this wear worth it compared to the savings on fuel cost?

In the short term I think yes. In the long term... Mabye not.

Still I think we're more likely to wear things out with the way we accelerate haha.

 

[CMF_Toma]

Robo,
You bet! Fuel light comes on at ~500km and still have about 13L left in the tank. If you do some calculations based on that, youll see that you can get another ~150km out of the tank with 2L spare. I like to run it as close to 600km as possible, then whimp out.

Doesnt matter in the end, as you'll still be putting more fuel in.
Only benefit is if you know the fuel price is better 50km away or gonna be better the next day. (aka fuelwatch)

 

[CMF_nz_aj]

Duty cycle doesn't go to zero when off throttle or engine breaking, perhaps it might if 2nd was engaged at 100km/hr or similar but that's not really particularly nice.
Once warm, the duty cycle on my K11 at idle is about 1.5
"Normal" engine breaking down a steep hill drops it to about 1.2
I'd agree that less fuel would be used if instead of engine breaking you were breaking harder. Driving through city traffic it's better to roll in neutral for extended period rather than using fuel to maintain a higher speed & then having to slow down faster.

 

[CMF_Yom]

Mabye the UK tune ECU is different to the japanese ecu.

When I let off the throttle going down or hill or engine braking the injector cycle is 0v (viewed through consult computer)

 

[CMF_Snoopy]

Above 2000 rpm, throttle closed, the oz micra's turn off the injectors to increase engine braking to assits down hill control. Its a very common feature on many cars including gen3 commodores. You can actually see it on the commo because if you bring up instant fuel consuption on the dash a throttle off over 2k it reads 0.0

 

[CMF_Sean]

Errmmm we are all forgetting a simple principle here:

Injectors off = no fuel
No fuel = Stall!!

Sean

 

[CMF_Yom]

simply_mighty WROTE:

"Errmmm we are all forgetting a simple principle here:

Injectors off = no fuel

No fuel = Stall!!

Sean

Not when you've got 800kg of car pushing forward on it. I'm pretty certain the ECU is also aware of your speed. For example in mine revving up to 5 grand in 1st gear and then letting off the throttle it doesn't completely cut the injectors. Doing the same thing in second (being at around 60km/hr I do recall it was cutting the injectors until the revs came back down to around 4000rpm) I believe it was reading between 0.8v and 1.2v - but i didnt take much notice of that because such an abrupt throttle movement is hell one's engine mounts so its not a common thing to do. And I lost all the data I logged over a 3 week period when my HDD broke. Bugger it.

 

[CMF_Sean]

Ok Tom you keep telling yourself that

I can 100% garauntee you that the injectors will not completely shut off. The consult may read 0% but there will still be fuel entering the combustion chamber and being ignited

Try it for yourself... Run along in any gear you'd like then turn the engine off and see what happens... Whether or not theres 800kg pushing it

Sean

 

[CMF_Yom]

If there's 0v being sent to the injectors according to the ECU (the ecu is not going to lie) where is the extra fuel being delivered?

Turning the car off won't simulate this situation. Turning it off will cut power to the ECU - the ecu is what is performing this particular function.

I'm not doubting what you're saying sean as dad's navara and my old pulsars never do this. The micra is the first car I've had which i've actually seen do this.

 

[CMF_Sean]

How won't turning the car off affect this?

If there's no fuel entering into the combustion chamber then what else does the ECU have to monitor besides the timing (irrelevant seeings as there's no fuel going in)?

turning off the car will simulate what you're trying to say and at no point will the ECU simply stop fuel from entering the combustion chamber

C'mon lets think about it... Pre-school mechanics 101

No fuel = STALL!!

When the car stalls it will not restart smoothly once rolling and in gear... Which it does when you coast in gear without any accelerator input

Sean

 

[CMF_Yom]

THe ECU controls alot more than the injectors mate.

There's not much point me continuing the discussion. I'm out of my depth with how the ECU works when it does this. All i know is that the ECU reads 0v to the injectors under compression braking and that the ECU has to send this signal out - its not lying.

I might borrow a consult computer again to graph the results and show you sean. Its quite a complex little party which happens under compression braking. The IACV goes nuts, O2 goes into extreme lean, lots of other funky things happen too.

 

[CMF_Toma]

Doesnt say much on fuel consumption, but hey! Its an interesting read.

http://en.wikipedia.org/wiki/Engine_braking

 

[CMF_Yom]

Bahaha well I just tried it sean. I drove down my street in 3rd gear at around 2500rpm and turned off the ingition.

Guess what happened.

Everything turned off but the engine kept on running and the exhaust was still making the same noise! It didnt even show a hint of stalling. Simply turn the key back to on and the guages came straight back to life and away we went. No jerking or hesitation. BUT if you let the revs go too low with the wrong gear ratio you WILL compression lock and find yourself plasted on the windscreen and some stressed engine mounts.

Bahaha i never thought that would happen but sure enough it did. I dare not try it in the diesel patrol though. I'll end up plastered on its windscreen with 17:1 compression ratio (and thats low for a diesel).

 

[CMF_Snoopy]

simply_mighty WROTE:

"How won't turning the car off affect this?<BR><BR>If there's no fuel entering into the combustion chamber then what else does the ECU have to monitor besides the timing (irrelevant seeings as there's no fuel going in)?<BR><BR>turning off the car will simulate what you're trying to say and at no point will the ECU simply stop fuel from entering the combustion chamber<BR><BR>C'mon lets think about it... Pre-school mechanics 101<BR><BR>No fuel = STALL!!<BR><BR>When the car stalls it will not restart smoothly once rolling and in gear... Which it does when you coast in gear without any accelerator input<BR><BR>Sean

The car wont stall because the wheels are still turning which in turn, turns the g/box, which turns the engine over. The minute you touch the throttle, push the clutch in, let the revs drop the injector turn back on. You dont even notice.

when the ecu is in this mode, it is still monitering whats going on & waiting to go back into normal run mode, so the minute it drops below 2k, or any other parameter are met, the injectors come back on & it will be just like normal throttle lift off.

It pretty simple preschool mechanics 101. Car is still moving, moving parts are directly linked to engine, engine still turns. Easy.

Actually to clarify it not pre-schools mechanics. It third year ecu basics for which I topped my class

 

[CMF_Yom]

nz_aj WROTE:

"Duty cycle doesn't go to zero when off throttle or engine breaking, perhaps it might if 2nd was engaged at 100km/hr or similar but that's not really particularly nice.

Once warm, the duty cycle on my K11 at idle is about 1.5

"Normal" engine breaking down a steep hill drops it to about 1.2

I'd agree that less fuel would be used if instead of engine breaking you were breaking harder. Driving through city traffic it's better to roll in neutral for extended period rather than using fuel to maintain a higher speed &amp; then having to slow down faster.

Don't you have an auto? That would change a few things I think..

 

[CMF_Sean]

On my microtech on my old Micra, duty cycle never completely dropped regardless of driving conditions etc... This was before the turbo conversion and tuned to as close to factory specs as possible...

And I got more fuel per tank from the Microtech than I did with the standard ecu...

Sean

 

[CMF_Yom]

Considered the possibility of its TPS not being set correctly? This would mean the ecu would never really know the actual tb butterly position. This could very well cause a dominoe effect on everything else. Lots of ways this could happen.

Another possibilty is that ECU programs are constantly changing. There may not be many differences but over the lifetime of a car's production (and usually until they start putting resources into making a new model) the engineers will be fiddling with the ECU's programs and maps to just fine tune things. Make it a little smoother there, make it a little more efficient here, get rid of that flatspot there, etc.

So yes what you're saying sean is quite possible.

 

[CMF_nz_aj]

Look at my profile, it's 5spd.
Yes the ECU knows the vehicle speed.
As well as the TPS voltage, Nissan data scan software also shows wether the ECU considers the TPS to be closed.
Graph is km/hr, TPS voltage x 10, duty cycle x 10.
As you can see, the duty cycle goes nowhere near zero.

 

[CMF_Toma]

On a side note, unleaded does get less than Premium per tank. After filling up this week, ill balance the numbers and see what cost/km is between the 2 and see if its really worth it!

 

[CMF_Yom]

nz_aj WROTE:

"Look at my profile, it's 5spd.

Yes the ECU knows the vehicle speed.

As well as the TPS voltage, Nissan data scan software also shows wether the ECU considers the TPS to be closed.

Graph is km/hr, TPS voltage x 10, duty cycle x 10.

As you can see, the duty cycle goes nowhere near zero.

Interesting that the Japanese tune does that. Its a shame the ecu plugs for the UKDM and JDM K11's are totally different. It would be kinda cool to have the UK built CG running a Japanese created tune. Haha. Man I'm sad.

 

[CMF_Toma]

http://www.fuelwatch.wa.gov.au/

If youre in WA and dont know about this site, you really are missing out!

Its got a good little saying too.. "Buy When Petrol is Cheap not When Your Tank is Empty"
And heres what they say.

Stick to the speed limit - High speeds use more fuel

Avoid idling - You are wasting fuel

Avoid stopping and starting - You are using more fuel

Keep your vehicle in shape - Clean air filters keep impurities in the air from damaging the engine and can improve fuel economy

Maintain proper tyre pressure - Under-inflated tyres can reduce fuel efficiency

Don't turn on the air conditioner as a first response to heat - Air conditioners use up fuel

A warm engine is more efficient than a cold one - Reduce the number of short trips

Remove excess luggage - A heavy load increases fuel consumption

If you can, avoid hilly terrain - As you are using more fuel

When buying a car - Think fuel economy

 

[CMF_Alex_B]

i've switched from using BP Ultimate at stupendous prices too Elite 95 from Freedom. Car was abit gutless on first tank mixed with 15lt of Ultimate left in there, but now its back to the zippy norm that Ultimate gave it. I use a tiny bit less fuel per 100km with Elite 95. And the best part is it costs 2c less than std unleaded, whereas the Ultiamte i was previously using was 10c more than unleaded plus my local BP was always more expensive than everyone else.

my 2cents,

Alex

 

[CMF_Toma]

Premium:
33.5L gets me 540km at 137c = 11.77km/$

Regular:
35.8L gets me 548km at 128c = 11.96km/S

Winner: Regular! (not by much)

So it would seem my results are pretty darn close. Close enough to even say its a dead-heat. I tried to drive the same for both tanks (non-conservative) and really not much difference in power aswell. As for engine wear, Im pretty happy with my fuel filter and last i checked, the spark plugs were looking nice. Both results are with Caltex fuel. The only real way to get an exact number is by running an engine with the same amount of traction over the same distance without any resistance. But i think my results are fairly 'real world'. Besides, its a 1.6% saving. Whoop-dee Doo!

In short, Im going to stick to premium. It gets you the same distance per dollar and you look classier filling up with premium at the bowser.

 

[CMF_Yom]

You should get one of the other perth members to help you advance your timing to make proper use of the premium.