80 Series running LPG

Submitted: Wednesday, Aug 28, 2013 at 12:52
ThreadID: 104084 Views:1583 Replies:7 FollowUps:1
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I was wondering if any one can give me some advice
i have an 80 series (97 4.5 litre petrol) so it is EFI
the system is approx 15 years old
i used to get approx 17 k's to the litre
i upgraded to a 2" lift as well as 2" larger and wider tyres
i now get approx 23 k's to the litre :(
i was wondering if anybody else has had this issue and if this is a coincidence or my car needs a good tune or LPG system upgrade
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Reply By: pop2jocem - Wednesday, Aug 28, 2013 at 13:43

Wednesday, Aug 28, 2013 at 13:43
While a good tune wouldn't hurt I suspect that 2" lift and the bigger tyres might be playing some part in your diminished fuel economy numbers.

AnswerID: 517212

Follow Up By: steve f6 - Wednesday, Aug 28, 2013 at 14:25

Wednesday, Aug 28, 2013 at 14:25
Thanks pop , your feedback is greatly appreciated
Was hoping it was not that :(
Well i will just have to live with it

FollowupID: 796803

Reply By: K Croft - NSW - Wednesday, Aug 28, 2013 at 15:36

Wednesday, Aug 28, 2013 at 15:36
Hi Steve, that seems like a massive improvement to me, my 80s on gas uses about 21lt +100k
I doubt that you get 23k /l. that's over 2000k/90l.
Regards Keith
AnswerID: 517221

Reply By: Member - Rob S (NSW) - Wednesday, Aug 28, 2013 at 20:34

Wednesday, Aug 28, 2013 at 20:34
Hi Steve
Check your figures again your getting more klm with the lift and wheels??

I have 2" lift, 285 /75/16 BFG AT tyers.
And Manual transmission.impco gas vapor system,

Unloaded,no roof rack, on a steady highway run, usually get 430klm from 90 litres used
About 21 liters per 100klm on lpg,

Around town 350klm from 90 liters used
About 25.5 liters per 100klm

Varies all over the shop from there with roof rack, load on board, driving conditions etc

You probably have a 112 liter lpg tank 90 liter usable.
Fill it and run it till empty, and check the klm's traveled

Those figures i quoted are fairly average figures that i commonly see across quite a few forums, for 80 series 1fz 4500.and if you get some were between these figures

430klm for 90 liters,hwy,

350klm for 90 liters,city you are doing well.

I only ever made one mistake
and that's when I thought I was wrong!

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AnswerID: 517232

Reply By: Rod W - Wednesday, Aug 28, 2013 at 21:18

Wednesday, Aug 28, 2013 at 21:18
For gods sake don't touch it!! With 17 to 23 k's to the litre that's B fantastic SO DON'T TOUCH IT!
AnswerID: 517235

Reply By: steve f6 - Thursday, Aug 29, 2013 at 07:14

Thursday, Aug 29, 2013 at 07:14
Yeah sorry guys my maths is not very good (I blame old age)
I WAS getting approx 450 k's to my 90 litres "usable" gas tank but
with the lift and bigger tyres it has dropped to 350 k's
and it is 90% freeway use too
I was hoping that someone else had had the same experience and had found the cause, as I was planning on downsizing the tyres back to factory standard and hope the fuel economy would return

Once again i thank you for your generous feedback
AnswerID: 517241

Reply By: Geoff K4 - Saturday, Aug 31, 2013 at 18:57

Saturday, Aug 31, 2013 at 18:57
Can I suggest you go back to the original size tyres, that's your trouble. A lot more effort on the engine running gear to turn the larger wheels.
AnswerID: 517428

Reply By: Big Woody - Sunday, Sep 01, 2013 at 07:00

Sunday, Sep 01, 2013 at 07:00
There are a couple of other factors possibly at play here.

The first is how are you measuring your km travelled? If using your odometer, with the diameter increase of your tyres it is possible that your measurement is up to 10% out and you are travelling further than your odometer shows. Different brand tyres vary significantly even with the same size specifications so you really need to measure the difference to accurately determine the percentage increase of the rolling diameter.

Another factor is the age of you engine running on LPG. In our family we have have 3 x 80/100 series with that engine on LPG and all have suffered exactly your symptoms of loss of economy and eventually loss of performance due to the heads and in particular the valves wearing out due to running on LPG. $2K-$3K of rebuilding the heads for LPG saw them return to normal.

Your comments about suspension lift and tyre chanes are also very valid. I too have had similar increases in fuel consumption from these changes as well as adding bull bars, spotlights and roof racks etc. incredibly I also saw a significant increase in consumption changing my BFG All Terrains to BFG Mud Terrains both in the same size.

Just thought I would add a couple of other things for you to consider.

AnswerID: 517443

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