Yeah your totally correct, but your taking all your petrol system components out which is alot of work and you ARE damaging the resale value of the car, you run out of fuel, you need a tow, gas system f**k up, no petrol as backup.

Lots of work : minimal gain (50km's extra a tank maybe?) : No backup : Less resale, lots of factors, not worth it overall imo

Careful with the tyre pressures up to 44-45, if you go onto a dirt road and start climbing you'll get wheelspin = dead tyre unless you stop and let it down.

Its not much extra, i didnt notice alot, maybe an extra 10-20km's a tank on the highway, i stick with 38 having tried 45.

well ... my BA has 1 kW difference between petrol and LPG, if that's crap it's pretty bloody good crap

lpg is the shiz, no question! f**k removing the petrol side of things, waste of time!

well ... my BA has 1 kW difference between petrol and LPG, if that's crap it's pretty bloody good crap [/quote]

Remove one or the other,re-dyno it, and watch the numbers jump.

Last edited by splatt on Tue Mar 11, 2008 5:44 am, edited 1 time in total.

that just means your petrol tune is lower than what it would be if it were dedicated petrol. dedicated lpg Bf's only put out 156 kw and a bit less torque than the petrol. I cant imagine your dual fuel system putting out more than that ford factory setup, so does this mean your petrol output could be somewhere around 160?

yeah i have the same problem i am lucky to get 350-400ks from a tank on a highway drive, gives me the s**t. I have replaced leads, plugs, coil, o2 sensor it has a nearly new ss induction air intake it runs perfect doesnt skip a beat even starts first crank on the coldest of mornings. It has me stumped as to why it is using so much gas do any of you guys have any ideas why? (Sorry to jack your thread luke )

True outta my manual (see below) I never get anything below 500k's per 70L of LPG. Its funny I'll drive the car and keep it under 2,500 rpm for the whole tank (very hard!!) and get around 520k's..then tried just normal driving (nothing over 4,500rpm- and only occasionly- and got 540k's work that out *lol*

I just did a mixed hwy and city run (mostly hwy) and used 40l of LPG for 365k's. That's just under 11l/100k. No too bad for a loaded up auto EF wagon. I did the tune myself and it seems to be working out OK. Because I don't have a petrol tank the LPG places always make the tune really rich to help make it start quicker.

cheers
Scott

tell me more MacGyver!
how exactly did you retune the gas system for such better economy?

This has been a bit of an evolution after some research and tinkering. The original method I used is listed in a sticky here. This method evolved through three stages. These methods work with OMVL r90, but should work with any system that has an idle bypass and sensitivity adjustment.

As always get a pen and paper and write down how many turns it takes on each screw (8mm idle bypass, 10mm sensitivity) to seat. This is your fallback. Reset and start car and run until nice and warm.

Stage 1: As listed in the sticky is turn the sensitivity screw way out (15-20mm). Turn the idle bypass all the way in. Now start car (it is warm right?!) and slowly turn the sensitivity in until the car feels like it is going to stall. Now turn out the idle bypass until you get the best idle speed.

I found this method to give great starting and idle, good economy, but poor responsiveness.

Stage 2: I read somewhere that OMVL changed their recommended tuneup to bypass the idle bypass screw. Basically fully seat the idle bypass and adjust the sensitivity for best idle.

I found this method to be pretty good overall. s**t starting but ok idle, good economy and fair responsiveness.

Stage 3: A mix of the first two. Turn out idle bypass 1 full turn from fully seated. Turn out sensitivity about 15-20mm. Start car. Turn in sensitivity for best idle. Now connect a multi to your O2 sensor and adjust the sensitivity very slowly in or out to get the O2 swinging around 400-700mV. Go for a drive and see how you like it. The next morning start her up (it'll be a bugger and idle rough). Now quickly adjust the idle bypass out until the idle smooths. Don't go too far, just far enough to smooth the idle. Now if you check with a multi you should be rich on idle but not go too lean for too long on acceleration.

This is perfect. Good starting, great economy and superb responsiveness. Just did another test and for 100k's highway and 165k's city I used 40l. That is 15l per 100k's combined cycle with a strong city bias.

One thought. If your car starts on petrol I would disconnect that for the first cold start to get that part of the tune right. My car is dedicated LPG so that would change things a little.

cheers
Scott

Im still amazed at that "impossible to tune both LPG and petrol" comment.

Most of it comes down to cost.

There are processors in the US which adjust a ford TFI curve to suit LPG while on LPG, and still run good petrol curves.

The Injected systems (lpg) - dont compromise petrol either. ANd they are the ones which are within kw's of petrol. On some cars with good programming LPG actually provides more torque at launch.

Time to modernise your thinking guys

Nigel

When starting on petrol with MPFI you leave the accelerator pedal alone. But when starting on LPG i find steady, very light throttle helpful.

A good LPG System is the same - no throttle.

If you open it too much you risk a nice backfire
especially if the ignition system is average

Nigel

I've just done some fiddling along these lines. Although my car has a problem with the revs dropping off after about 3500rpm (and this fiddling didn't help it), hopefully there is also something to be learnt about idle and mild throttle scenario's.

I find that the more i use the bypass, the smoother things are (possibly more responsive as well). With the ISC off, the bypass out 1 turn, and the sensitivity *all* the way in, it actually idles fine. However, i then reconnected the ISC and tried to restart the engine and it wasn't keen, though i think i had put the air con on. I'm not sure if the ecu needs some time with a new tune to learn how to run it (i fine tuned the timing recently and it ran like a dog on LPG straight afterwards, but later ran well). Maybe as you say it needs sensitivity as well as bypass.

In my short runs i couldn't detect a difference in power between the different tunes, or a difference in economy, of course, but that's not to say there wasn't one.