Improving fuel economy

[JimX]

(cross-posted on OCAU forums)

From a usual city cycle economy run of 14L/100km (very sedate driving, ie hardly ever) to 16L/100km (hooning around) I just turned in a result of 13.3L/100km with my usual heavy-footed driving after doing some routine maintenance on my R33 GTS-t. The power has also increased noticably down low, though it's not noticably different when floored. Idling is also smoother and throttle response improved.

Ok, so what did I do to get this fairly hefty improvement in fuel economy? Here's a brief list:

1. Changed spark plugs.

2. Replaced fuel filter.

3. Put some Spitfire injector cleaner in fuel tank.

4. Installed a fuel catalyst in the fuel line (this is the controversial one).

I'm not going to focus on the last point because I'm not convinced they work either - after I go through a few tanks of fuel I'm going to remove it and see if my economy worsens again. Because of my lack of focus on it I won't even mention what brand/type it is.

But the first three things I did certainly helped. I don't know which of the them improved power and economy the most, but if you've just bought a car and don't know for sure when those things were done you should do them asap. I wish I'd done them a lot sooner now.

I was going to pull the injectors out and get them ultrasonically cleaned, but I think I've achieved most of the economy gains already so it's probably not worth the extra $200 or so to pull them out and get them dnoe.

The plugs I used were NGK Iridiums to replace the standard platinums that were in there. The old plugs were in pretty good condition so I still think the Iridiums have something going for them.

I cut open the old fuel filter to see what it was like inside and it was SCUMMY! The filament was all black and clogged up, and there was black SLUDGE in it! I couldn't believe my eyes. Does anyone know how long it takes a fuel filter to get in that condition? They cost about $20, I might just start doing it every 10000km.

Just a hint to anyone wanting to change the fuel filter on their Skyline - make sure you have some spare fuel hose on standby (or at least access to some at short notice) because it was an utter BITCH to get off. In the end I had to cut the hose and replace it. If the old filter has been there for a long time most likely you will damage the metal connectors if you attempt to pull the rubber hose off.

[benm]

Onya Jimah !

I have no idea how long my fuel filter and spark plugs have travelled but i know at minimum 12,000km.

I would say my average fuel economy would be about:

17.2L/100km (350km from 60L) if i drive hard.

15.0L/100km (400km from 60L) for an average week

11.7L/100km (513km from 60L) best ever while still hitting the speed limiter about 4 times.

Im quite confident that if i drove the car like a normal human being with light freeway driving i could get around 10.8L/100km whilst driving on stock boost.

If i knew how to change the fuel filter i'd probably do it. (Easy on my old Pulsar i'll have to take a look on the 'Line).

[JimX]

Ok, fuel filter is dead easy, unless you're a stubborn pighead on me and try for about an hour to remove the hoses which refuse to come off If I had cut my losses after trying and failing to pull the hoses off after 5 minutes I could have done the whole job in about another 15 minutes.

Here's a rundown on what to do to change the fuel filter.

1. Buy a Z200 filter from GP Auto1 and about a meter of fuel hose (1/4 or 5/8 inch I think? Check what's written on the old one).

2. Leave the engine off for maybe 15 minutes to allow the fuel pressure to drain back into the tank. Some people would say you should bleed the fuel line properly though the a valve somewhere but in my experience I find it fine to just put a lot of rags underneath where the fuel will squirt out of the hose when you pull it off or cut it. When I cut my hose after an hour it just dribbled out, so if you want to play it really safe then wait an hour

3. Put some rags underneath the whole area where the fuel filter and line is. I used an old bathroom towel which is nice and big and soaks things up nicely. It didn't need to be that big by a long shot but it's best to go over what you need than under.

4. Take all the clamps off (be sure not to lose the small nut which holds the screw in) and try for A COUPLE OF MINUTES AT MOST to pull the hoses off carefully. If they don't come off within that time you'll probably never get them off in which case you should proceed to step 4a. Otherwise go to step 5.

4a. Cut the fuel hoses as close as possible to the metal line connectors on the car, rather than near the ones on the filter. I just used a sharp pair of small scissors. If you use big sidecutters then be VERY careful as if you misjudge where the metal connector starts you might end up pinching it shut or cutting it off. Err on the side of caution and do it a few cm above where you think it ends.

5. Pull the fuel filter out, then if needed do a vertical cut along the remaining bits of fuel line still in the car so you can pull them out.

6. If you need to replace the fuel lines, measure up the old lengths to the new hose you bought and cut them accordingly. Don't forget to add on the sections that were left in the car to the line length. If your old lines are still in one piece and in good condition, remove them from the old filter.

7. Put the hoses onto the new filter and re-attach them to the car.

8. Put the clamps back on and tighten them up reasonably tight, but not too tightly. They go just behind the bulge in the metal on each connector, on the METAL side obviously.

9. Switch the ignition to the ON position and then OFF again a couple of times to get the fuel up and through the filter.

10. Go back to the engine bay and check for leaks.

11. If all's good, start her up!

Please note that I take no responsibility if you blow your car up during any of this, but if someone can point out a glaring error or omission please tell me and I'll fix it up.

[benm]

1 thing i forgot to mention was that i have my C/C set to 22c +1 Fan set on for everytime i drive my car. So im quite confident that i could avg out at around 450km/60L everytime i drove the thing.

[JimX]

My climate control is rarely off too

[MM2death]

Do R33s tell you how much petrol you're using? like a digital display?

[skyline33]

Originally posted by MM2death

Do R33s tell you how much petrol you're using?  like a digital display?

nuh, only the fuel guage

[benm]

I wish....

[benm]

Just changed my Fuel filter. Took me about 15mins and i didnt even spill that much fuel. (Left car sit for 2hrs)

I've got some Wynn's Injector Cleaner which i'll add tonight before my next tank of petrol and then see how we go.

I have some pictures of the dirty Fuel Filter.