Fuel Consumption

[tridentt150v]

Sorry if this has been covered before, but when I did a search I got all the ones from the FI section and not just the RB30 section. Link it if you know of it.

When you went from an RB25 to an RB25/30 did your fuel consumption increase at all?

Interested in litres/100km, not your tank etc, and highway miles not around town.

I've done and seen increase in capacity actually lower fuel consumption [good] but also increase it [not so good].

I ask this because I mainly use my skyline for long trips and I like the power - and an RB25/30 is my next step - but I don't really want to majorly adversely affect my economy.

If you could list your consumption and rwkw as a comparo that would be good.

I presently get 10.8/100km at 300rwkw out of my RB25 [not a thirty yet].

Thanks

[-_-StRyDeR-_-]

500hp 25/30 drove from the Gold coast to melbourne and back, not all light driving, every single tank of fuel i refilled at 420-440km's and i hadnt hit the fuel light yet, try not to drive it if its just short trips so i wouldnt know a figure around town... however... same motor... 630hp on E85...dont ask.

[tridentt150v]

500hp 25/30 drove from the Gold coast to melbourne and back, not all light driving, every single tank of fuel i refilled at 420-440km's and i hadnt hit the fuel light yet, try not to drive it if its just short trips so i wouldnt know a figure around town... however... same motor... 630hp on E85...dont ask.

Thanks, yeah, not interested in E85, nonobtainium in country. On a drive from Melbourne to Brissy you'd have to fill your boot as well, you'll not find it in 3/4 of the country towns up the Newell etc.

Would have been good if you'd done a total fuel vs mileage and had an average....but its a start.

[R31Nismoid]

500hp 25/30 drove from the Gold coast to melbourne and back, not all light driving, every single tank of fuel i refilled at 420-440km's and i hadnt hit the fuel light yet, try not to drive it if its just short trips so i wouldnt know a figure around town... however... same motor... 630hp on E85...dont ask.

Holy fark... Only 420-440 on the freeway?

When i did Melb/Syd over xmas in the GTR (full weight) - 130km/h the whole way, so i think 3300rpm.

Stock gearing, 2.65L

600km 1st tank. Fuel light on

650km 2nd tank. No Fuel light

I'm sure i could do 700km based upon the 2nd tank (which i stayed off boost for 95% of it)

So under 10L/100km, could be as low as 9L.

I'll repeat the trip later in the year too and try for 700-750. I feel power is laregly an irrelevant factor when you are on the FWY and not using boost.

I'd expect a RB30 to use more fuel though for the same distance. Larger motor - same RPM = more fuel.

[tridentt150v]

I'd expect a RB30 to use more fuel though for the same distance. Larger motor - same RPM = more fuel.

Yeah, true...but more torque so doing it a bit easier.....so I'm not sure and wanted to get some real world feedback.

And 650km to a tank is very very good. I'm happy at 550km [and thought I was doing OK till now].

[Piggaz]

You have stock cams though Ash. That would have alot to do with it!

[JonnoHR31]

Yeah, true...but more torque so doing it a bit easier.....so I'm not sure and wanted to get some real world feedback.

fuel economy wise the extra torque doesnt help at all, it makes more torque because its a bigger motor and draws in more air at low revs than a 25, more air means more fuel on the same tune.

all else being equal the 30 will use a bit more fuel but not enough to put you off the conversion. if it bothers you that much buy a corrolla for daily duties and enjoy 6-7L/100km no matter how much you thrash it

[rockabilly]

32 tank holds more than 33 and 34..

[TiTAN]

on the highway Canberra > Sydney 9.5L/100km (GT35 cruising at highway speed you rarely ever hit boost)

[MBS206]

fuel economy wise the extra torque doesnt help at all, it makes more torque because its a bigger motor and draws in more air at low revs than a 25, more air means more fuel on the same tune.

all else being equal the 30 will use a bit more fuel but not enough to put you off the conversion. if it bothers you that much buy a corrolla for daily duties and enjoy 6-7L/100km no matter how much you thrash it

Not quite.

If it's tuned properly you should see better fuel economy.

The RB30 runs the same bore, and a longer stroke. For the same amount of fuel/air being burnt, the RB30 will make more torque, as the stroke is longer. Remember torque = force*distance. Therefore you can close the throttle a bit more, to make the same torque.

For example if it only needs 50nm (FOR EXAMPLE) to hold 100KM/H, and that's with your motor burning 100ml / min of fuel with a stroke length of 1. If you now double this stroke length, and keep burning the 100ml of fuel, the force on the end of the crank is the same, but the distance is double, therefore you've double your torque. So now for ever 100ml / min of fuel being burnt, you're making 100nm... But you only need 50nm, so you can close the throttle off, and use half the amount of fuel. Obviously volumetric efficiency etc comes into play, but going from a RB25 to an RB25/30 the VE shouldn't change at all...

If it's not tuned right though, the same as the smaller motor, it can loose all sorts of cruisability and economy too...

A perfect example of this was my old 25/30 as it was never tuned for under 2000RPM properly, so around town it used to get 25L/100KM and I had to cruise every where in 3rd.

[Dale FZ1]

When you went from an RB25 to an RB25/30 did your fuel consumption increase at all?

Significant increase observed, from 9km/l to 7km/l. I'm sure both figures could have been improved, but under broadly similar conditions and driving patterns.

That is not 100% highway cruise, involves about 5km of lower speed running either end to get in and out of town. Camshaft spec changed, and I believe the propensity for vastly improved turbocharger response via increased swept capacity means it swallows a lot more air down low, and needs to be fuelled accordingly. Both factors work against fuel economy, but I got the torque increase from off idle to 3000rpm that was being aimed for.

HP generally costs fuel.

[dorifticon]

r32 GTR, Rb26/30, 380rwkw (dyno'd in rwd mode), 272 deg cams, HKS 2530's, Vortex 98 pump fuel.

About 15 litres per 100km normal driving, about 20 litres/100km if I'm abusing.

Not really highway but canberra driving is kind of like highway driving, I avoid stop-start traffic wherever at all possible.

Definite increase in consumption from rb26, but other factors like cams would have affected it (esp. low rpm cruising efficiency).

[tridentt150v]

fuel economy wise the extra torque doesnt help at all, it makes more torque because its a bigger motor and draws in more air at low revs than a 25, more air means more fuel on the same tune.

all else being equal the 30 will use a bit more fuel but not enough to put you off the conversion. if it bothers you that much buy a corrolla for daily duties and enjoy 6-7L/100km no matter how much you thrash it

Logic [not always so logical sometimes] made me think that you would hold your cruise speed = energy better esp. going up hills or into headwind. And for the sort of average usage I'm asking everyone to quote on [say on a +500km trip] you will at some stage experience both cross/head wind and hills. And I'm not sure about flats/plain driving either. I know that some big bore conversions can actually see fuel efficiency eg 253 to 308, and many motorbike ones as well [i have a 750/1000 and my fuel economy has marginally increased with it.

And no I'm not wanting Corolla efficiency - just not a 350 Chev Hotrod guzzler either. As long as you get acceptable economy then its all good. The ability to be able to drive for 4-5 hours before you fill up is a damn good thing when towns [and good fuel] are spaced out in our sunburnt land.

Just my thoughts anyway.....

[sucram]

Its a massive compromise to have one tune for everything and doing so is time consuming. It nearly works out easier to have a totally different MAP for highway/economy driving

you cant always have cake and eat it too

[R31Nismoid]

HP generally costs fuel.

To a certain extend yes, but IMO the tune is far more important and you can have the HP without the fuel consumption on an RB that’s for sure.

Different if you have say a XR5 turbo or something that is on boost virtually all the time no matter what you do as boost is the killer.

Its a massive compromise to have one tune for everything and doing so is time consuming. It nearly works out easier to have a totally different MAP for highway/economy driving

you cant always have cake and eat it too

How so?

A tune for the areas you are on cruise have anything to do with those on load and WOT etc.

It is most certainly possible. Look @ my figures – I’m making 350rwkw and almost made it from Melb to Syd on a tank!

And this was not even using a O2 sensors either. They are turned off so its 100% in the tune and nothing else.

I mean if I am up it, I can see 250km to a tank – it comes down to use of the right foot.

[jarrod83]

HP only costs you more fuel when you do mods like cams that causes you to lose effeciency down low.. i think its because they have a larger overlap they have more unburnt air/fuel mixture go out the exhaust valve before it shuts, i dont think i have ever had a shop thats tuned my economy driving or least done it very well as it usually comes out with afrs in the light cruise region of the map from 13.7s-14.3s.

I have read that 16:1 is the afr that gives you the best fuel mileage but i wouldnt know if its safe to run, i went for a long country drive a while ago with my rb30 and wasnt going to make it home so i dragged out the laptop and adjusted the afrs out to mid 15s, got home easily and barely moved the fuel gauge

[R31Nismoid]

And that's the difference a lot of the time between a good tune and a great one.

WOT/high load is only one part. People wonder why tunecosts vary from place to place. not saying that paying more will always get a full/excellent job... but when some people charge 250, and have the car for half a day... How good is it going to be?

[sucram]

How so?

A tune for the areas you are on cruise have anything to do with those on load and WOT etc.

It is most certainly possible. Look @ my figures – I'm making 350rwkw and almost made it from Melb to Syd on a tank!

And this was not even using a O2 sensors either. They are turned off so its 100% in the tune and nothing else.

I mean if I am up it, I can see 250km to a tank – it comes down to use of the right foot.

say at 3K rpm which is about where 110klm is on the highway

Best economy might be around 16:1 with light acceleration enrichment

Best off boost power might be around 14:1 with more enrichment then the above

Or it could be around 13:1 with a bit more timing then above

The Map area you cruise in isnt usually where you run on full load, (but can be) but it is in a zone where you go through

and near a lot in normal every day to day driving when you are going through other gears. Constant Rpm and Load is

only 1-2 load zones. Slight up hills are another 2, bigger hills are another 2. So you might only use say 6 load zones on

a PFC (for E.g) if your REALLY trying to be econimocal. The ECU interpolates so you need to compromise the zones around

it for a total of 18 load zones. For simplicity reasons I wont bother interpolating any more. So you now have this big hole in

your map and it runs leaner in the lower gears. Not so bad if you have extra capacity but annoying if you have stock capacity

and bigger turbo/s. This is one compromise.

Most aftermarket ECU's have 1 enrichemnt at 3k RPM. Running f**k all is good for economy, but if you come to a big long

hill, switch to 4th as you start to loose speed, still in the lean part of the map, switch back to 3rd and nail it just to get to a

different part of the map where its actually mapped for power. This is a compromise

Because your running f**k all fuel in these 18 load zones your forced to run Less timing. Less fuel is better for economy

but as your railing through gears in suburbia just to keep up with all the auto commo's etc you now wish you had more

fuel so you could run more timing and overall have more power. This is a compromise too.

On top end ecu's with a lot of time spent on the tune you can get a better compromise, even with a shit ecu like the pfc im using atm an

acceptable compromise can be made.

You can dam near double your mileage if you specifically tune for it. It involves really lean mixtures, realy shit timing and hardly any enrichment to

the point where you can feel the car surging for fuel when you go up a hill with an incline of more then 3*

[R31Nismoid]

I can have 250km to a tank or i can have 650km+. Seems like a pretty good compromise to me.

Economy is as much about the right foot/driving style as it is about the tune, ECU and anything else really.

Infact as a end user scenario all i see is economy thats almost double the stock ECUs capability, whilst making more power everywhere on the loud pedal. This is without any detonation, in any gear, at any RPM etc etc. Even with the "shit" ECU.

I think we can all understand and appreciate you can't get the absolute best economy, but you can get some pretty damn good economy and still have the power/midrange to boot without the need for dual maps.

[sucram]

You would probably easily see 900klms if soley tuned for economy for highway use

Dont know about you but I used to get 480klm on a stock ecu in suburbia driving like a normal person

Dont get me wrong, back in the day PFC's were OK.....8 years ago lol.

Would I change mine? well less is more at the moment.