hi

I've got a sierra 2WD with some modifications :
L8
lambda sensor
knock sensor
BD10 (inlet + exhaust)
swedish plenum
RS500
mongoose
T35 + 0.48
siemens 55 injectors and everything required (map waste gate ....)
new water sensor (true magneti marelli)
thermostat 82
fuel pressure 3.5

I ask msd an eprom with the close loop

the first time, I do as required 5 turn right and 1,5 left
it was really bad, car was really too rich
and plug where "dead" after 40 km ; unable to start the car, plugs dark dark

the max value for the exhaust temp (my egt is fitted on the turbo A/R 3cm after the end of the exhaust manifold
was 720 °C with is really low

I ask msd and he tell me to do 1 more turn left to lean the car (the CO value at 4000 rpm should be between 2,5 and 5)
4000 rpm = out of the close loop range

first I do 0,5 ; car sames a little better and max exhaust temp is 810 °C


I'm been to a garage doing a check with the CO (before I do the 0,5 turn left, so I have 1 turn as required with msd)

results :
CO at idle is arround 3,5-4 (I have the close loop)
CO at 4000 rpm is 7,5 (with is more than 2,5-5)

and the gas temp at idle is arround 330°C (normally should be arround 450)


I ask again msd, but to be honnest the person answer really shortly (2 sentences) and he just tell to check with the afr (for sure but it's the price of the eprom)

2 friends of me tell me the had problem with the 82°C thermostat and put back the 88

I will do this to check, but I really doubt of the results

can someone help me


any idea ??

would be nice if someone can give me with an L8 and close loop
the CO value at idle
CO value at 4000 rpm
gas temp at idle

thanks

 

co on closed loop is normally around 0.90%

it is vital all base settings are correct like fuel pressure etc, and that there are no air leaks

is it deffo going into closed loop? have you tried a muliti meter at the ecu terminals to check the lambda sensor is working corectly?

 

have you fitted a PF09 TPS (4x4) or do you have the (2WD) TPS still fitted
as if you fit a L8 on a 2wd loom you need to swap the wires over for this when fitting a PF09 TPS

so you ECU night be seeing full throttle@idle and idle@full throttle

 

yes

4WD fitted and wire reversed

fuel pressure ok
and no air leak


regards

florent

 

If the thermostat is at all suspect just change it anyway, I always use 88C.
tabetha

 

it's a brand new 82°C

but 2 friend had problem with the 82


any idea for the CO at 4000 rpm ???

thanks

 

I had no end of grief with 82C stats of various makes, so now use WAHLE, it's the only one that worked perfect and stayed working.
tabetha

 

what problem they had with the 82 mate?

 

1 friend had engine power problems

with the 82 --> dyno = 327
with the 88 --> dyno = 380 (with is normal with the car configuration)

the second had problems with the rev, with the 82, the car "cut" arround 4000 and more
after with the 88 .. no problem


to be honnest I do not understand why a simple thermostat can change something

but I prefer to be sure and remove 1 doubt so I change it

 

The most influential factor for CO/fuelling is the temperature, other things offer a trimming of this, but CTS is most deciding factor by a long way, maybe yours for some reason is/was running far too rich ?
tabetha