Bigas problem?

[a11mcr]

hi all i have a bigas system fitted to my mg zt 190 which is running rough but when i try to auto calibrate it just keeps saying "impossible to continue gas temp to low" i have tried everything even fitting smaller resistors in the temp sensor but still nothing, when running normal the gas temp is between 50-70oC is this normal?
i need to get this sorted as the car runs @!## on gas and i beleive some of the settings are out (Fitted the system myself second hand its from about 2002)
please help?

[redzed]

The components used are actually NTC thermistors where their resistance decreases as the temperature increases. You might think that by replacing the thermistor with a resistor of the correct value in order to fool the ECU into thinking that the temperature is within range would do the trick but I suspect that the ECU is looking for a changing resistance/temperature so the fixed resistance of a resistor would not work.

BTW, the temp sensors supplied with the Bigas kits are rubbish quality. I've now made 2 of my own.

[tommo2009]

there are two temperature sensors on the bigas system, one on the vapouriser and one on the injection rail. the one that is causing you your problem is the one on the injector rail. Get a heat gun (paint stripper gun) and gently warm the sensor up.
once this has seen a higher temperatuire it will run through it's calibration.

[a11mcr]

Thanks, what type of thermistors would i need to make my own (quite good with electronics)
also could the vaporizer be faulty as it looks about 200 years old and covered in crud as the gas pressure changes sometimes its 1.1 bar and other times its 1.8 bar and can go down to 0.7 bar?

[Gilbertd]

could the vaporizer be faulty as it looks about 200 years old and covered in crud as the gas pressure changes sometimes its 1.1 bar and other times its 1.8 bar and can go down to 0.7 bar?

You've got a regulator that isn't. Looks like it's well beyond retirement age.......

[rossko]

Thanks, what type of thermistors would i need to make my own

5K NTC probably. But why would you want to do that, nothing said here suggests that they are broken. What can you see?

Have a close look at vacuum pipes before throwing out vap too.

[tommo2009]

why not listen to advise and try and warm the injector rail temp up to a point that it will calibrate.
what are your temperature values reading on the software?

Lets change everything before trying the simple things

why do we try to help??????

[a11mcr]

hi i have warmed it up even to 100 0C but still says to low sometimes it will start to auto calibrate then just shut off and says gas temp to low?
cheers
mark

[rossko]

What readings do you actually see reported on the laptop? How do they behave over time e.g. after starting the engine? During your calibration attempt?

[tommo2009]

which one have you warmed up to 100. the vapouriser can be at 300 but if the injector rail is too low it will not calibrate.

what temperatures are being read when the system is connected to a laptop.

[tommo2009]

if the temperature drops while calibration is in progress then you have insufficient coolant flow. could be a plumbing issue, or could be a dodgy water pump

[a11mcr]

hi all took it out for a run today and somtimes it seems to loose power after a few minuites but if i switch to petrol and back again it fine for a few minuites then goes funny again, just fitted a set of brisk plugs and still does it, i have saved some aquistions if anyone can make them out? (can email them to anyone) also when running on gas the gas temp drops to around 25oC but on idle its arround 40oC is this normal?

[redzed]

also when running on gas the gas temp drops to around 25oC but on idle its arround 40oC is this normal?

I would imagine that the differing flow rates explain this, as when on idle the liquid/gas is going through the vapouriser more slowly and therefore has the ability to have a greater increase in temperature. A person walking very slowly past an electric fire would get much warmer than a person running past it.

[rossko]

when running on gas the gas temp drops to around 25oC but on idle its arround 40oC is this normal?

Yep.

Have you fixed your erratic gas pressure ?

[a11mcr]

yes sorted the gas pressure out (split pipe), what would make it feel like its dieing on me but then sometimes runs ok? i have played about with the gas pressrue and it seems to pick up better the lower the pressure (does anyone know what it sholud be for this engine mg zt 2.5 v6 190+)
i have it set to about 1.15 bar at the moment, also i would like to know what these graphs mean? (but would like to know how to upload them?)

[alexf2828-2]

if your good with electronics its not hard to spoof the temp sensor-a 1000 ohm resistor in place of the sensor used to fool mine into thinking the engine was upto full running temp. I think the water temp should be 80-90 degrees C so your readings sound low

[tommo2009]

if your temp drops when the car is being driven then you have insufficient coolant flow or a knackered vapouriser.

what are the heaters like in the car, do they blow hot, warm or cold. could be a head gasket, quite common on that engine.