Fuel economy, what you can do about it.

[AlexCim]

Well, in my quest for improving my fuel economy (current i do 150km/half tank) i am pooling all the previous threads into one for anyone searching on how to improve the fuel economy.

First, i would like to note my car is standard, high flow panel filter, cold air intake and jaycar EBC set 7/10psi. I normally drive on 7psi. I am a normal driver, not a hoon. City driving.

Tips to improve economy:

* Change the O2 sensor if its really old (60,000+)

* Check spark plugs, gapped to 0.8mm

* Jaycar digital fuel adjuster (getting mine tuned this weekend, will let you know results)

* Fuel filter, replace it

* If you have a Jaycar EBC, set it to 100% the WHOLE rpm range, meaning boost comes on later

* "On the highway you can drive for miles without the converter locked up unless you do the following: establish the cruise speed - say 100 - 110 km/h, then throttle back until you get 12-14 inches of vacuum , then gently press on the accelerator until your boost gauge reads 5-8 inches of vaccum, and then you should feel the converter lock up, after which if you modulate the throttle smoothly, you can drive it like a manual unless you go into boost, whereby the converter drops back off the lock up and your fuel economy suffers again."

* An exhaust should imrove things also

* "An interesting fact my Brother in law told me (mechanic) that driving with AC on is more efficient than with the windows down on long, highspeed trips. so just keep that in mind when testing to see if better fuel economy without AC, don't wind the window down"

* Make sure you tune your car after any modifcations. Pod/Filter/Exhaust etc all make the RB's richer...odd i know.

* Keep car off boost, however this may result in really slow driving.

Anyone else got anything i can add?

Cheers

[ian]

* "An interesting fact my Brother in law told me (mechanic) that driving with AC on is more efficient than with the windows down on long, highspeed trips. so just keep that in mind when testing to see if better fuel economy without AC, don't wind the window down"

Actually, this is technically know as wrong :-) It's an 'urban myth', that anyone who has done a lot of driving OR understands the theory knows is wrong, and was even on 'mythbusters' a while ago (shown to be completely busted).

Ian

[YNOTSX]

OMG!

are they really that bad on fuel?

damn!

that's something i didn't know, and that i should look into fixing once mine arrives

Tony B

YNOTSX?!

[AlexCim]

They are not THAT bad... its just mine i reckon

Ill keep everyone posted on what happends after new spark plugs/o2 and dfa...im sure it will get HEAPS better

Tony, you bought a stagea?

Would an old timing belt cause bad fuel economy too?

[GoldZilla]

* "An interesting fact my Brother in law told me (mechanic) that driving with AC on is more efficient than with the windows down on long, highspeed trips. so just keep that in mind when testing to see if better fuel economy without AC, don't wind the window down"

Actually, this is technically know as wrong :-) It's an 'urban myth', that anyone who has done a lot of driving OR understands the theory knows is wrong, and was even on 'mythbusters' a while ago (shown to be completely busted).

Ian

<{POST_SNAPBACK}>

Actually, my theory (and it is only a theory) says that the aerodynamics of the car would be a large factor in this.

I think it would depend on how much turbulence you get when the windows are down - if the air flows over the car and past the side windows cleanly, then it is less likely to have an adverse effect on your fuel economy. If you get a lot of turbulence with the windows open, then obviously there is more air being diverted into the car as opposed to over and around it, and the economy would suffer accordingly... I think if someone were to properly research it in a wind-tunnel (or similar), under controlled conditions, then we'd have some more conclusive results. Whether they'd want to test each and every car available on the market might be a different story!

There was a discussion somewhere about that Myth-Busters episode, and apparently they used a typical American SUV, with crap economy nd aerodynamics anyway, so that's probably another reason why the results came out that way. I'll see if I can find and post the link here later.

Seriously, how can they justify driving such ridiculously large 4WDs when most of them live in the cities and suburbs?

[GoldZilla]

They are not THAT bad... its just mine i reckon

Ill keep everyone posted on what happends after new spark plugs/o2 and dfa...im sure it will get HEAPS better

Tony, you bought a stagea?

Would an old timing belt cause bad fuel economy too?

<{POST_SNAPBACK}>

Don't think the timing belt would be a major factor, unless it was REALLY badly stretched. Then again, if that were the case you'd most probably be replacing pistons and valves, or about to be up for similar major spending.

Ouch!

[AlexCim]

Well, when i bought my car, the mechanic who inspected it told me he could hear the timing belt "flapping around against the cover" when he was revving the engine from the engine bay.

That makes me presume mines pretty bad (as far as timing belts go)

I dont understand why im the only person with a stagea doing 20L city and 16L hwy...Im getting my timing belt done early next week, it should hold until then

[Sydneykid]

Well, when i bought my car, the mechanic who inspected it told me he could hear the timing belt "flapping around against the cover" when he was revving the engine from the engine bay.

That makes me presume mines pretty bad (as far as timing belts go)

I dont understand why im the only person with a stagea doing 20L city and 16L hwy...Im getting my timing belt done early next week, it should hold until then

<{POST_SNAPBACK}>

You are not the only one. Ours was 16.5 l/100k combined conditions before I leaned it out with the DFA. Even after that I can get it to 15l/100k if I hustle it along, that's not thrashing, more like driving briskly. If I really pushed it, 20l/100k would be easy.

Unlike most cars it doesn't get much better on the freeway. For comparison, the R34GTT gets 10's on the freeway and 14's around town, so it improves 4l/100k. The Stagea improves only 2 to 2.5 l/100k and that's being careful. The aero dynamics of the waggon at work, plus it's an auto and 4wd.

I am hoping that the exhaust upgrade will make a difference, that and the cat upgrade should remove the cork that it currently has stopping it from breathing. I am going to throw a new lambda sensor in there as well, just to be sure I have picked up everything I can.

So YOU ARE NOT ALONE

cheers

[AlexCim]

Well,

Im just about to buy the 440$ cat and 450$ split dump and front pipe from bos importing. Couple that with my fujisubo catback on the way (84dB at 4800rpm!!) and that makes 2g worth of exhaust...but i expect major improvments in fuel economy and about 35-45awkw more

[surfstagea]

hello, just a random piece of information for those interested in fuel economy...

with 10 psi, plus 3" exhaust, i average 12 lt /100.

with exhaust plus intercooler & 12psi, i average 14 lt /100.

that is a combination of city and country driving.

so just incase anyone was wondering if a front mount cooler will assist in fuel economy, you are PROBABLY mistaken.

*it might have a bit to do with the increased power and driving variation (pre and post intercooler), but it is probably safe to say that a front mount definately will not improve the fuel economy.

[Cubes]

The fuel economy issues some Skylines have has always baffled me.

My little RB20DET used to consistently run 10.5-11L/100km's.

The Rb30DET is slightly heavier and returns a consistent 11.5-12L per 100km's.

Its always on boost as the poor little rb20det turbo doesn't allow the motor to breathe freely at low rpm.

I'm soon to replace injectors that have been cleaned and flowed. It should be interestering if I notice a drop or increase in fuel economy.

[ferni]

I still can't figure out why my gf's R33 GTS N/A gets the same fuel economy as my GTR, around 350k/tank...

[Cubes]

Clagged injectors?

[ian]

Unlike most cars it doesn't get much better on the freeway.  For comparison, the R34GTT gets 10's on the freeway and 14's around town, so it improves 4l/100k.  The Stagea improves only 2 to 2.5 l/100k and that's being careful.  The aero dynamics of the waggon at work, plus it's an auto and 4wd...

Yep I get those types of numbers from my R34GTT - but mine is M-AT and is often in full auto (wife driving) and is the 4 door sedan.

But the series 1 stagea is 200KG heaver, with the not as good (ie non NEO) engine - and one of the benefits that Nissan claimed for the NEO was that it was better on fuel usage even though it had more power..

So I'm not sure where that puts the stagea... I'll do a lot more posting in a couple of weeks, as my stagea arrived yesterday :-) I'll be able to directly compare that to my R34 as I've got a series 2 (ie NEO) - in fact, they look absolutely identical under the hood.. :-)

Ian

[Red Sky II]

Following the replacement of a faulty wiring loom and coil packs in my Series II Stagea, I average around 11.5 l/100K with a combination of peak hour morning driving and flowing freeway driving at night.

Usually always use full auto with the occasional tiptronic for fun

Totally stock Stagea that has better economy than my former Series II Skyline did

[CerealKiller]

I can't understand why my fuel economy is crap. I've cleaned the injectors ultrasonically, change fuel filter and O2 sensor, and had the S-AFC tuned...400 per tank on the highway driving relatively conservatively...

[sy300]

My Stagea is factory standard. It gets about 14-15l/100km around town. On the open road it improves to about 10-11l/100km (at 100-115km/h).

This is pretty much the same economy as my '92 NA 300ZX got, which suprised me, as it was a manual, non-turbo, not 4WD, a couple of hundred kg's lighter and a bit more slippery through the air. The Z went further on a tank though, it had a 72l tank as oppsed to the Stagea with 65l.

I actually managed to drive the Z from Palmerston North to Auckland (about 500km) on just over 3/4 of a tank. Not done this in the Stagea yet, petrol prices are through the roof here in NZ.

[AlexCim]

So, maybe i should look into some new coilpacks for my stagea? i want to cover everything to improve fuel economy...

Currently about to be put in:

-bos front/dump 3 inch split

-4inch stainless cat

-spark plugs

-DFA

-o2

Now, should i consider getting

-coilpacks

-injectors unsonically cleaned?

As a reference, i do about 800 or so km a week (meaning, 150$ petrol bill)

Edited August 16, 2005 by AlexCim

[Sydneykid]

I must be having a dumb day...........how does cleaning the injectors improve the fuel economy? Surely a dirty injector flows less, so the fuel economy should be worse when it is cleaned and flows more.

The ECU doesn't know that the injector is dirty, it still opens and closes it according to the mapping. In closed loop running, the ECU aims for 14.7, so it doesn't matter if the injector is dirty, 14.7 is still 14.7.

If the engine runs rough because the injectors are very dirty, then I can see a case for cleaning them improving the efficiency of the engine. But if the engine is running nice and making good power then the injectors aren't that dirty. Even slightly dirty injectors aren't good for power or engine life, but I can't rationalise fuel economy improvements from cleaning them.

As I said, I must be just having a dumb day........

cheers

Edited August 17, 2005 by Sydneykid

[CSV Imports]

My Stagea is damn good on fuel I'd say averaging around 11.5-12 combined. Its relitivly close to my FTO 10.75-11.5