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rb 25 running poor

Mason Lockyer

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Hi there I have just put a G3 into a rb30 block/rb25 head with 260cc injectors .Got it running with a few issues but nothing related to ecu just owner of vehicle using old coils/old coil/ignitor loom/and a ignitor that would stop firing number 2 coil after it got hot.Got all that sorted and got vehicle running ok with a base map i had from a rb20. Drove it and found injectors were maxing out at about 4000rpm and only about 7 pounds of boost owner then got some 550cc 13 ohm injectors from a rx7 for me to fit. fitted injectors and now cant get engine to run any good.with the old injectors i was running about 22 on the master fuel but now to even to get it to just run master needs to be around 15 if i go up to 20 engine floods and if i go below 11 engine back fires like antilag. my worker said it was running like that before injectors were changed that morning but i never heard it before i changed the injectors but it was ok the night before when driven into the shop?. Do you need to change the master and complete fuel map as soon as you put bigger injectors in to even get it running i have gone through all of the config and cant see anything has changed i have decoded cas again with no luck. One thing i noticed looking at the nissan cas wiring diagram on your website is the 12volt power feed i have only the link 8v feed to the sensor as per G3 manual says do i need 12volts i have also put trig 1 and trig 2 earths together on cas earth wire is this ok. why did it run ok the day before

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My first advice would be to go back to the old injectors and master number and fix the running problem if there was one.  At least that rules out the injectors. 

RX7 injectors are known as being a little odd due to their spray pattern, but often used in upgrades...   Ideally you will correct your map for the new injectors by decreasing the numbers in the fuel table by the percent increase in injector size and entering the correct deadtime numbers. 

BUT, due to the large change in injector size, you will have to change the master as the numbers in the fuel table would get too small.  Once you change the master that far, change the dead times and go to injectors that have a different atomisation characteristc generaly you will need to do a reasonable amount of retuning.

As far as I know, the ECCS CAS is supplied by 12V from the ECCS relay, not from the ECU's 8V supply.  When the ECU turns on the ECCS relay, the CAS gets powered up.  It may run OK at 8 volts, but you will need to test to prove it.  Check for trigger errors in the triggers tab of the runtime values.

Hope that helps...

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I am using the link loom as the factory loom is in real bad shape and i have removed from vehicle and started again. So there is no 12v feed to the cas sensor from relay anymore so i used the 8v link feed to cas. Going to sync the ecu is picking up trig 1 and 2 and zero. Should i us rb20 cas or select other when decoding sensor

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