Fuel quality switch on race car
09-21-2017, 08:36 PM
#1
Burning Brakes
Thread Starter
Fuel quality switch on race car
Hi All
Just pulled the DME from my 1991 944 S2 RHD race car which supposedly has a standard DME in it 944 618 124 05. Now, it has no O2 sensor and I found that the dme is set to position 6 which is -3%fuel and -2.77% spark adjust.
Now, I have done a lot of research and it seems there are questions whether -2.77% actually means that the timing is retarded, or that there is a negative value added to the retard, i.e the ignition is actually advanced.
So, would there be any reason why the FQS would be set to 6 (like maybe for the cut off O2 sensor)?
THe car runs only high octane fuel with a standard engine and fuel pressure regulator.
Just pulled the DME from my 1991 944 S2 RHD race car which supposedly has a standard DME in it 944 618 124 05. Now, it has no O2 sensor and I found that the dme is set to position 6 which is -3%fuel and -2.77% spark adjust.
Now, I have done a lot of research and it seems there are questions whether -2.77% actually means that the timing is retarded, or that there is a negative value added to the retard, i.e the ignition is actually advanced.
So, would there be any reason why the FQS would be set to 6 (like maybe for the cut off O2 sensor)?
THe car runs only high octane fuel with a standard engine and fuel pressure regulator.
09-21-2017, 10:43 PM
#2
Rainman
Rennlist Member
Rennlist Member
its -2.77 or however much degrees, timing retarded.
speculation here, but in the 80s Porsche built "detuned" versions of their cars for the Australian market and I would imagine NZ cars got the same treatment.
this is why Oz got the 928 with the US-type (EU optional) 32v 5.0 288hp in 85-86 instead of the 4.7 16v 310hp like the rest of the world.
the reason was suspect quality of unleaded gas available at the time in those countries. while i would imagine they could accomplish that purely by retarding the timing a little maybe the reduced fueling was to complement the lesser timing. maybe your FQS setting is factory/dealer prep for your country. since your petrol is surely higher quality these days i'd imagine you could set it back to 0 timing 0 fuel and see how it runs...
speculation here, but in the 80s Porsche built "detuned" versions of their cars for the Australian market and I would imagine NZ cars got the same treatment.
this is why Oz got the 928 with the US-type (EU optional) 32v 5.0 288hp in 85-86 instead of the 4.7 16v 310hp like the rest of the world.
the reason was suspect quality of unleaded gas available at the time in those countries. while i would imagine they could accomplish that purely by retarding the timing a little maybe the reduced fueling was to complement the lesser timing. maybe your FQS setting is factory/dealer prep for your country. since your petrol is surely higher quality these days i'd imagine you could set it back to 0 timing 0 fuel and see how it runs...