Starting/Fuel Problems
 

I have a 6 port with a t4 turbo 1000 secondaries and 680 primaries, and recently had my lt8 reloaded with the base turbo tune. The car was very hard to start but finally ran. After being shut off, it would not start again, and continues to foul the spark plugs. Even after wiping them off it will crank with spark for the first few turns then you no longer hear spark and it cranks without firing. Despite having low compression could it be that an injector is stuck open, or is this something i should be able to fix with tuning?

its cranking thinking its got stock injectors when in fact there is X % larger ones so the cranking and idle maps are going to be X % richer

what did you expect?

find the factor of difference between all injectors now ( it cranks on all four injectors ) and the stock injector setup

remove that factor as a % from the mix trim

the car will now start provided the timing is correct and the plugs good

take note of the real time number generated while idling,,,
this is the target value you shoot for when you take out that mix trim and fix the staging % value
( both will alter that real time crank and idle number )

any factor you pull or push from the mix trim can be directly applied to the bin value of the cranking maps
and staging % factor corrections can be zerod and can be directly applied to the idle and pre staging map bin values


if that isnt coming through clear ,, the idea is to aim to get that real time idle number back to what it was once you fix the staging % and mix trim factors

so like would i
take

550/1000
550/680

average those two values and thats my % increase?

stock FC turbo is 550 X 4 = 2200 cc
stock FD is 550 x2 + ( 850 x 2 ) = 2800 cc

which of these stock fuel maps have you uploaded?

you claim you have 680 x 2 + ( 2 x1000 ) = 3360 cc

so if you have the s4 13bt map you are 3360 /2200 ,, or 1.5 times the volumes of fuel intended

reduce the mix trim 33 % and see if it starts

( i expect it will start but stall out as with -33 % trim it will idle lean )

now,,,the original 550 map is for even injectors,,,the staging split is set for 50 %

you need to shift the staging % up to deal correctly with the moment the ECU stages from 2 to 4 injectors

without giving away directly the long math,, 680 cc is going to amount to being 65-70 % on the staging value

that will restore mostly the idle and low down mixtures up till staging

from that point and higher loads ,, all corrections go back to that initial 33% volume correction applied with the mix trim
( which is compensating for the difference in flow volumes between s4 injectors and yours )


NB
if you have s6 map uploaded ,, disregard
NB
this is serious shit and is intended only to get you started and idling,,and provide the correct basis to start building a map from
proceed at your own risk

thanks for the help, I have the fc turbo fuel map 550 x4 loaded