Setting up new system

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steviewonder · #1 Post by **steviewonder** » Sat Mar 22, 2014 5:06 pm

Hi all, I now have my Astra fitted with a Bigas kit and have done an auto calibration so it is running on LPG. However, I need to fine time it and would appreciate some advice!

I understand that Tinj petrol needs to be the same on both fuels, should I be looking at Tinj gas for anything?

How do you decide on what the gas pressure should be set to?

I did an auto calibration, got the Tinj petrol times on idle the same and enabled the 'adaptivity' as I have the Bigas ECU connected to the OBD port. This caused the 'corr. gas' percentage at the bottom to increase up to about 15% and it pulled the Tinj petrol time down when on gas. Is this normal or why would it do that? Is it a useful feature or should I switch it off?

It's working out at just under 11.5p/mile so not all bad

Thank you as always

Tubbs · #2 Post by **Tubbs** » Sat Mar 22, 2014 5:37 pm

If your running a 15% correction then you need to be a bit richer.
Best thing to do is highlight the whole map. Add 20% and see what the correction factor is then. You can always -20 after.
Have a look at the fast trim. See what the figures are. Ideally -1.6, 0.8 , 3.2 and back to -1.6 again would be perfect. If the fast trim hits 15/20% then you need to adjust around the area where the dot is.
It needs to be gradual increases / decreases. No big jumps. So for example If one block is 110 you don't want the one next to it to be 255.

steviewonder · #3 Post by **steviewonder** » Sat Mar 22, 2014 6:28 pm

Thanks, so I need to focus more on fuel trims than injector times?

Any advice on what to set the gas pressure to?

Tubbs · #4 Post by **Tubbs** » Sat Mar 22, 2014 8:38 pm

What's your pressure set to. ?

steviewonder · #5 Post by **steviewonder** » Sat Mar 22, 2014 9:09 pm

It was 1.0 bar to start with but I turned it up to 1.4 bar because my instructions said it should be between 1.3-1.6 bar for turbo engines. No real logic behind my choice.

Just tried editing the map going off the correction factor and the fuel trims were getting much worse. Turned off the adaptivity, did an auto calibration and they're much better, fluctuating very close to zero so I will leave it there.

Tubbs · #6 Post by **Tubbs** » Sat Mar 22, 2014 9:49 pm

It's best to tune with the adaptivity off. Once you have the trims tight all the way up the rev range bar open throttle, where it's open loop. That's the time to turn it on.
1.4 bar would be about right. Nozzle size and gas pressure are a bit of a balancing act.
If your nozzles are too big, and you turn the pressure down your gas injector times would be longer. Pressure up and they will come up shorter on next calibration. As long as they are within. 1-1/2 ms of each other it's not a problem. If they are say 5 ms above then you are going to hit the injector duty cycle too early. So they will cause problems at the top end.
If your pressure is too high and the injection times are too short the injectors may not be able to physically open and shut quick enough. Your idle will become unstable engine could hunt stall or generally start cutting out or could put the eml on with fuel trim issues.

steviewonder · #7 Post by **steviewonder** » Sun Mar 23, 2014 7:57 pm

Had another go at this today and it definitely wasn't happy at 1.4bar, it gave all the above symptoms of pressure too high. Turned it down to 1.1bar and it's smooth again.

I maybe should have said I have a RI-21 double reducer, both outlets going into one injector rail. My thoughts are maybe if it's getting gas in at both ends the pressure doesn't need to be as high as it would with a single reducer, but I could be wrong.

Done another auto calibration and left it at that for now, hopefully I'll get it looked at by someone with a bit more know how in the near future.

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