Bit of advice for a veteran LPG installer please.

[Forrests Speedshop]

Oh yes also something i noticed is when i go down the road trying to get a graph saved,the connection to the ecu keeps dropping out which is annoying.Could this just be a dodgy cable?Im guessing with it being cold and it not wanting to bend much its getting mardy.

[luke123]

Regarding you planting your foot and it's hesitant add gas on your map but add abit at a time, as to me it sounds like your not getting enough gas when you want it, the gas pressure on the table looks good to me

[Forrests Speedshop]

Excellent thanks.I will have a play shortly.Regarding the gas pressure.In the settings part where you select the vapourizer/reducer pressure mine is set at 0.9bar but the Zavoli Zeta s reducer i have is rated at 1.4 bar.I just wondered if i had to alter this setting?

[luke123]

Excellent thanks.I will have a play shortly.Regarding the gas pressure.In the settings part where you select the vapourizer/reducer pressure mine is set at 0.9bar but the Zavoli Zeta s reducer i have is rated at 1.4 bar.I just wondered if i had to alter this setting?

Yeah set that to 1.4 bar, You will probably have to auto calibrate it again

[Forrests Speedshop]

Ah bugger,i was hoping not to have to auto cal it again as thats when it started popping under hard accelleration.Ive got it on the stock map atm and it runs alright bar the slow pick up.I will go have a play.

[Lpg Monkey]

You really shouldn't need the pressure that high 1 to 1.1 bar should be more than enough don't just randomly add gas as has been suggested above. You need to look at your fuel trims on the vehicle ecu most eobd readers will give you the info you need then add or remove gas as is needed remember too much gas will sometimes give you the same symptom as not enough

[Forrests Speedshop]

Good advice thanks Monkey.I have various scanners,mostly strap on but the Jeep Ecu is very basic and i struggle to get any trims on any of the scanners i have.Its only just obd2 on this chassis.

Would you suggest i drop the pressure on the reducer?

[Lpg Monkey]

I ran a grand Cherokee 1996 for over 6 years I now run a 4.7 v8 neither of them have ever needed more than 1 bar. if you wind it up to 1.4 it might say 1.4bar at idle but it will almost certainly not sustain that pressure when actually needing to deliver the fuel in any real amount so you will get the pressure dropping to 1 bar under load anyway imo turning it much past 1.1 is pointless.
As long as the rpm's are reading correct according to the lpg ecu, your nozels are placed correctly, the nozel sizes in the rails are correct ( think there is a box that appears in the display section of the software after auto cal ) and the firing order is correct there is no reason why that car should not run fantastic straight off an auto cal, that dosent mean you shouldn't map it properly using the obd port whilst watching the trims lol. you can also do it with the pinj timigs run it on petrol see how long the injectors are open for then switch to gas it the petrol injector timing falls then remove gas it they increase then add gas you can do this throughout the map at set road speeds lets say 30, 40 ,50 ,60 , 70 and maybe 80 just keep adjusting the gas map so the petrol timings are the same weather on petrol or gas and youll not be too far away. to give you a better idea of nozel sizes at idle round about 4 -5 milliseconds of lpg injector timing give or take and much past 25 milliseconds on hard throttle under load and your pretty much just tipping fuel in its not that important on acceleration as long as its revving clean and not switching back to petrol then your motor should be fine.
If your really stuck message me and ill pm you my number and see if I can help you better as its hard to explain everything properly through typing.

[Forrests Speedshop]

Great stuff thanks monkey!So.Just so i have it right in my head.

Petrol map at idle


Gas map at idle



Because the fuel trim reads higher percentage when on gas,this is because the petrol ecu is seeing a lean mixture and it wants more gas adding on the map.

More so at 2000rpm

Petrol map


Gas Map


Again,because the fuel trims are a higher percentage on gas than they are on petrol and ALSO because the petrol injection time is 3.67ms on petrol and reads 4.17ms on gas this also means that it requires an addition of gas at that particular point on the map?
Bare in mind these were taken at a standstill but ive got the basic concept right i can shoot up the road as you say and read the trims and also the petrol injection times at various speeds and adapt the map to suit?

I think ive got it now!If not feel free to call me a tosser and i will try again
Thanks for your help

[Lpg Monkey]

I see you have connected the obd wires you should leave them disconnected until you have calibrated it properly the map numbers don't seem quite right the idle boxes are normally somewhere around 100 ish then gradually increase anywhere up to 255 as rpms and load increase once you have the map correct then you can connect the wires and activate the obd adaption. Looking a that map it needs resetting and recalibrating without the O2 or obd wires connected. You are correct when the fast trim is a positive number you need to add gas when its a negative then it needs removing however you can only adjust the idle part of the map whilst stationary. If its adding on the trims say at 2500 rpm but your just revving it in the workshop then it will need loads more gas when actually under load and it will be in boxes that are lower on the map as it will be under load

[Lpg Monkey]

Drop your gas pressure too its running a 1.5 bar if its at 1 bar ish and you bed a bit more or less there is adjustment if you calibrate it at 1.5 bar and need a bit more you haven't got it also its better to run the reducer in the middle of the range rarther than flat out all the time it will last longer

[Lpg Monkey]

Lol also remember you must reset the ecu to base parameters every time before you run an auto calibration otherwise it can cock up

[Forrests Speedshop]

Im on it thanks very much!I shall disconnect the lambda and the obd wire and run an auto cal and reduce the pressure in the reducer.

Edit:I didnt know that lol thanks

[Lpg Monkey]

Reduce the pressure before you auto cal it 1-1.1 bar is more than enough

[Forrests Speedshop]

Reduce the pressure before you auto cal it 1-1.1 bar is more than enough

Ok will do thanks.
Just so im correct i want to be adjusting it at idle on gas reading this figure (circled blue)

Until i get it set to 1-1.1 bar and then in the settings tab i want to set the reducer to 1.0 or 1.1bar which is here?



Wow my M/S paint hasnt had this much use for years.

[Lpg Monkey]

That's the one probably a touch higher but that should do nicely

[Dave K]

Regarding you planting your foot and it's hesitant add gas on your map but add abit at a time, as to me it sounds like your not getting enough gas when you want it, the gas pressure on the table looks good to me

Bit confused here. If the gas pressure looks ok, why suggest turning it up ?...

'Yeah set that to 1.4 bar, You will probably have to auto calibrate it again'.

[Lpg Monkey]

My thought exactly especially when the graph said it was at 1.5 most of the time

[luke123]

Regarding you planting your foot and it's hesitant add gas on your map but add abit at a time, as to me it sounds like your not getting enough gas when you want it, the gas pressure on the table looks good to me

Bit confused here. If the gas pressure looks ok, why suggest turning it up ?...

'Yeah set that to 1.4 bar, You will probably have to auto calibrate it again'.

On the config he was on about as it was set to 0.9, if you read his posts properly and look at the images he has provided!

[Tubbs]

Seems to be looking ok on the map. But you need to tell the gas ecu what pressure the gas is at. It can then make adjustments accordingly overall to the map. Turn off the adaptivity. When you have matched the fuel trims on gas and petrol by highlighting the blocks and adding / taking away 5 % at a time and seeing what effect you are having on the fuel trims. - is rich and positive figures are lean. Really you want to see the trims go from - to + always fluctuating.
I would say you could get away with highlighting the whole map and adding 10 %. Seeing what effect it has on the trims. And then take it from there.
You want the figures to be a gradual transition. So for example, one block at 76 and the one next door reading 255 would not be good. That's why it's better to use percentages rather than absolute or linear.