GQ TB42E Fuel Economy

[nutloose]

So here goes, My first thread! and its gonna be a Looooonnnngggg one... Skip to the bottom for the bullet points.

I have been struggling with the terrible fuel economy of my Patrol when running on Petrol. Here is what my current setup is
1993 GQ TI LWB Wagon
TB42E Duel fuel with IMPCO 200 mixer and model L converter.
eBay snorkel into standard EFI air box
Modified Cyl head at some stage for extra cooling inc spacer plate on thermostat housing
Timing set so 20Degrees BTDC
2 Inch lift
33 inch Bighorns
3/4 ARB Roofrack
ARB Deluxe Bullbar with winch, Driving lights and LED Light bar.
91 unleaded from the Same fuel station and the Same pump.


I was having issues with the gas system not running properly when coasting (It would miss and carry on) and the car would never run at operating temperature.

I gave up rather quickly LPG system after changing leads and plugs with no real change I decided to remove it and refit the standard air intake piping back in. While I had the engine bay in bits I took the petrol injectors out and have them bench tested and cleaned and they came back all good. (For anyone who doesn't know and is interested, The TB42E injectors are 360cc according to the bloke at the injector shop) while at it I purchased some MAF sensor cleaner and cleaned out the MAF sensor.

So with my LPG system removed, my injectors back in and my timing reset to 10 Degrees BTDC (Factory) I went for an initial drive to get my first economy reading. 48.89L/100!!!

With that reading I began thinking about everything that could be affecting it. and without a second to think, I purchased an "ECUtalk" cable to get some information from the ECU.

With the ECUtalk cable plugged in and the ECUtalk ap up I could see the cars coolant temp sensor was showing only 61Degrees, The Oxygen sensor reading 0.02V and the ECU stuck in open loop mode. With that information in hand I used the Nissan scantech software to emulate the engine coolant temp to 82 degrees(The opening temp of the standard thermostat) and bingo the ECU instantly tried to go into closed loop. but it couldn't do much because the Oxygen sensor was still only reading 0.02V So to the shops again for an oxygen sensor. Once I fitted the oxygen sensor I found the loom was in crap condition so I repaired that while I was there. now that was working. I drove it to and from work for a week returned 24L/100. (Daily commute conststs of 1 Left hand turn, 60 ks through the town, the 100 to the next town a left hand turn and im there in 22K’s)

Next on my hit list was the fact the car wouldn't warm up. So out came the old thermostat for a new one. Still no change. Next step was to block off the extra cooling lines put in by whoever molested this car before I bought it. and bingo. the car came straight to operating temp and into closed loop mode and with that all working correctly I was able to achive some better fuel economy.

With some 4wding I got to 22L/100 just around the local stuff. (5 mins drive from home, 1-2Hrs 4WDing, few tight tracks few steep hill climbs and rut navigating then back home 3 times a week)

After that I reset the timing again to 12Degrees BTDC and reset my idle back down to 650RPM.

On the Highway today (Pricess Fwy from Morwell to Noble park, stop start from noble park to Ringwood and then Stop start Ringwood back to the Freeway back to morwell I was able to get an amazing 17.88L/100! Now that's where I would love to be every day!


So for those who don't wanna read everything and just want bullet points, Here they are.

• Changed plugs and Leads
• Starting economy 48.89L/100
• Purchased ECUTALK
• Removed LPG system
• Serviced injectors
• Cleaned MAF Sensor
• Replaced thermostat
• Replaced Oxygen sensor
• Reset timing to 10Deg
• got 22-25L/100 on 2 tanks driving to and from work
• Reset timing to 12deg
• Replaced Rotor cap and button
• Removed old cracked ebay snorkel and fitted new Safari snorkel
• Blocked off extra cooling to Cyl head
• drove to and from Melb with Ac on in stages and lots of stop, start traffic. Returned 17.88L/100

smiles all round! I hope someone else can use this as a rough idea of where to look for issues and hopefully save some money! All my mates think im crazy because i have invested time and money into this project. Do you?

Also for the record, I'm not a crazy go fast everywhere and make everyone look at how cool my 4WD is person in my patrol but I'm also not a grandpa.

Cheers for the read and I’d love to hear your responces!

Nutloose.

[Touses]

I know naff all about gas but welcome Nutloose!

[nutloose]

Hey Touses, i know enough to be dangerous its great stuff for daily use but my my weekend rig it didnt cut the mustard without a turbo! Now that would be fun!

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[UncleFrosty]

Thanks for the extensive thread Nutloose! Well worth it. (@dom14 would be interested too I reckon...)
I use around 33/100 on gas (dual fuel), so will be interested in trying some of the things you've already done.
Cheers!

[billyj]

when you say you set the timing to 12deg did you just turn the dissy or follow the procedure outlined in a gregorys/nissan manual? if you followed the procedure it should be good but if you just set it without following the procedure then your probly about 3deg retarded form ideal

the best i ever got was 13l per 100km on a long fwy run, avg was about 18-20l per 100km, these days i get 20-22l but pushing about twice the power of a stocker

also a set of etractors and 2.5" exhaust will give the tb42e a little extra grunt and slight improvement in economy

[nutloose]

I turned the advance off using nissan data scan and adjusted it that way. Then rechecked with it back on seems good never actually check total advance was late at night and didnt wanna annoy the neighborhood

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[nutloose]

@UncleFrosty i suggest first looking at your oxygen sensor and get some readings. You might find its out of tune. I got a jaycar kit for about 20 bucks that goes inline with the o2 sensor. Works well for inital diagnosis. Multimeter will work too.

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[nutloose]

@billyj i forgot to mention i have a set of castle extractors into a std exhaust. Im not i terested in listening to a drove for days on end travelling to cape or the kimberley or the likes.

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[billyj]

if the timing is set correctly per the nissan procedure you should get a reading of 15 deg on your ecu talk at idle once warmed up

[nutloose]

Havnt look on ecutalk again. When the weather clears up ill have a squizz

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