Trip Computer & LPG

[autickfordfairmont]

Hey guys,

Just a quick question, just had my car converted to injected gas system. Now the LPG isnt hooked up to the fuel gauge so my DTE wont work, which is fine at this stage, but when on LPG my instant L/100km & average L/100km still work. Where does it get the readings for these??? and are the readings im getting accurate???

Cheers

Col.

[RavenLS1]

the car dosent know its running on LPG, so it takes the mesurement as if your running on petrol.
the readings wont be correct for LPG because it uses more gas the petrol.

[FGII-XR6]

injected gas uses the same amount as petrol you only use more with the mixer system this came straight from a major LPG importer/installer

[au2sw]

as stated above, your instant and average L/100km is still running as if on petrol. it is actually taken from petrol level sensors, TPS, tacho and a couple of other things. SVI uses about the same literage as petrol, and the mixer style systems will use a little more. if you want, the DTE and literage readings can be changed to suit LPG if you like, but it involves a bit of stuffing around, mainly electrical work, same as getting your dash guage to read both fuels. i believe that doing this, you may lose petrol readouts, but im not sure. and if going with the dash guage setup for both fuels, it will take a few minutes to change readings between fuels, so you dont get an instant reading of levels.
hope this has helped confuse everyone further info and help can be found in the LPG forums in the workshop section of the main forum page.
col

[robbo_yobbo]

Its pretty straight forward to make your cluster guage and DTE read on gas and petrol.
All you need is a relay switch. just cut the level sender wire in the boot and put the open relay curcuit in between the 2 cuts. then have your gas switch give the relay power when its switched to gas (youl need to run a single wire up to your dash) and have the closed circuit send the gas level senders wire from your gas tank to the dash side of the cut you made on the fuel sender wire. then the relay fits nice and neatly under the carpet hidden away on top of the fuel pump and you dont have to mess around under the dash.

I probably made that sound allot more complicated then it realy is, if you cant figure it out I can draw up a diagram for you. but as said above, it takes 10 seconds or so to change the display when switching fuels because of the level buffer (which stops the needle from flying all over the place around corners and hard acceleration/breaking)

[robbo_yobbo]

one thing I should mention though, is it will only be acurate if the resistance on your gas sender is the same as on your petrol sender. If not it will think there is more gas then there realy is, and it will tell you your very uneconomical, or it may be the other way and think that you dont have much gas but it will tell you that your very economical, either way though empty will still be empty!

[blownba]

Originally Posted by robbo_yobbo

Its pretty straight forward to make your cluster guage and DTE read on gas and petrol.
All you need is a relay switch. just cut the level sender wire in the boot and put the open relay curcuit in between the 2 cuts. then have your gas switch give the relay power when its switched to gas (youl need to run a single wire up to your dash) and have the closed circuit send the gas level senders wire from your gas tank to the dash side of the cut you made on the fuel sender wire. then the relay fits nice and neatly under the carpet hidden away on top of the fuel pump and you dont have to mess around under the dash.

I probably made that sound allot more complicated then it realy is, if you cant figure it out I can draw up a diagram for you. but as said above, it takes 10 seconds or so to change the display when switching fuels because of the level buffer (which stops the needle from flying all over the place around corners and hard acceleration/breaking)

This WILL NOT WORK THIS WAY.
You will need to change the gas tank sender to an AU type than the VSI programming for level gauge will have to be changed to suit the new sender resistance at full empty and half way. Then the gauge wire can be cut in the RHF kick trim and a 5 pin CHANGEOVER relay can be used to allow gas level to be read off the dash.
Please note that if you change the level sender without reprogramming the VSI computer in alot of cases it will not run on gas cause it does not recieve the standard 0-90 ohm signal anymore.
I'm sorry but it is a little more complicated than you state but is not impossible. Really whoever fitted the system shoulda done it for you cause I do.

[robbo_yobbo]

Dude It does work this way, I hooked it up like that on my car with no problems at all, All you gotta do is make sure the gas sender is the same rating as the original petrol one, otherwise your readings are higher/lower than they should be.
if you do it right, All your doing is switching the input on the cluster from the fuel tanks sender to the gas tanks sender.

It doesnt make any different where the wires are cut weather it be in the boot, kick panel or behind the clustrer itself, it all does the same thing, I just found it easier to find which wire was which in the boot because there were less of them, and it hides away easily and neatly.
you might not have understoodd what I meant, Ive put a diagram (a little crude but does the job) below so theres no confusion

[blownba]

Originally Posted by robbo_yobbo

Dude It does work this way, I hooked it up like that on my car with no problems at all, All you gotta do is make sure the gas sender is the same rating as the original petrol one, otherwise your readings are higher/lower than they should be.
if you do it right, All your doing is switching the input on the cluster from the fuel tanks sender to the gas tanks sender.

It doesnt make any different where the wires are cut weather it be in the boot, kick panel or behind the clustrer itself, it all does the same thing, I just found it easier to find which wire was which in the boot because there were less of them, and it hides away easily and neatly.
you might not have understoodd what I meant, Ive put a diagram (a little crude but does the job) below so theres no confusion

Once again you have missed the point. This gentleman is running injected LPG, by my understanding, and the injection computer WILL NOT register the new senders resistance when full/ empty ect WITHOUT being reconfigured ie. reprogrammed. It is fairly easy to do but he will have to go back to who fitted the system to get reprogramming of the VSI unit.
If this is not done in alot of cases the car will not run on LPG because the VSI computer will not be able to read the fuel level so it will not switch to LPG and will log a fault.
Also it once it is programmed correctly it will read the correct level on the gas switch/ gauge as well.
Mate I do this for a living and I think I know what has to be done and as a matter of fact with the system I fit on the AU's I do fit the AU sender and reprogram the VSI so the DTE and trip computer work seamlessly.

[robbo_yobbo]

I dont know much (correction *anything) about injection gas systems, but I dont understand why the fuel guage side of things would be any different on an injection system compared to a mixer ring setup.

If Im wrong Ive got no problems standing corrected but I am now seeking further info.

even if the gas injection computer thought the tank was running bone dry (no signal), why would that stop it from working? The settup wouldnt cause problems on the dash cluster/guage side, so what I am interested to then know, is why would the injection system be designed to not work when the tank is low (or completeley empty for that matter) or with no fuel sender signal. the standard petrol ecu will keep trying to fire the injectors even if the petrol sender says EMPTY. It will fire away if there is no signal at all. Even if the system logs fault codes like the standard ECU, it doesnt make sense as to why that kind of fault would stop it from working.

IMO if the gas injection computer needs a fuel sender signal to work, it seems like a floor in the design - what if your sender becomes dicky, your whole system shouldnt stop working because of this. Is this situation (must have sender signal to work) brand specific or across the board, and if across the board do you know the reason for this?

Im not having a go, but it just doesnt sound right (based on my limited knowledge), and am now curious for you to explain what it is that stops the system from working when setup like that.

Cheers.

[RavenLS1]

Originally Posted by au3xr6

injected gas uses the same amount as petrol you only use more with the mixer system this came straight from a major LPG importer/installer

The fuel economy of LPG-powered vehicles depends on a range of factors but on average, late model vehicles running on LPG use approximately 30 percent more fuel than petrol-powered equivalents. However, some high consumption petrol vehicles may in fact use only 20 percent more LPG.

Remember, however, that this is more than offset by the much lower cost of LPG, which is typically half the price or less of unleaded petrol. The introduction of improved performance LPG injection systems will see this 30 percent figure reduced even further.

[blownba]

I'll find out exactly why but I know that if the thing has no gauge signal it will not switch over to gas. It logs a fault code and the switch beeps at you. This has been my experience with the gear I fit but I will not say its the same for all brands.
Its really not that hard to change the parameters of the gauge signal in the ecu's program as the system is designed to run any sender other than the standard 0 - 90 ohm as long as ya tell it what the empty resistance is and full and half way.
Its a 5 min job for whoever fitted it.

[robbo_yobbo]

If you could find out that would be great, this has got me more than curios now.

also, what brand computer do you guys fit? I have been looking at gting a svi setup, but dont want one thats going to potentialy have that kind of issue if (and when) the sender fails if I can avoid it.

Even still, sureley you could easily trick the svi computer into thinking theres a sender singnal by running a straight 90ohm resistor (for 20cents) off a positive line which would then still allow you to set the guage and dte set up as I described above on the original cluster without the svi computer knowing anything has even changed.

Only reason I suggest this, is even though its reletiveley simple, when I had my gas installed, I was quoted somewhere around the $200 mark to set it up on the original cluster guage. if you do it yourself, it cost a couple of dollars in wire+switches+solder and 10 mins puting it together which is well worth the saving imo

[autickfordfairmont]

Thanks for all the replies.

Now if it is taken from Petrol Level sensor etc etc etc, how can it show that i am using an average of 14L/100km (after driving 100km) when i was running on gas for 99.5km of that. If my fuel level hasnt changed, how can it give average consumption??? or is it calculating instant consumption of injector pulse timing, TPS, tacho, etc etc, and works its average consumption from that??

Getting the gas hooked up to the DTE & Fuel guage would be great, but i will leave that one for now.

Cheers.

Col.

[robbo_yobbo]

must be an instant readout based on the injector pulse and odo??? I didnt think it worked that way, but you learn something new every day!