Td_d
Commander In Chief
Firstly - I would like to point out this is not my discovery - hence I am quoting the original poster, an old timer on Romraider.
This is however a very useful technique to keep EGTs safe in tuning open loop - particularly when looking for the effect of leaning out AFRs whilst keeping EGTs safe. I have personally used this for some time, and can confirm that (at least for the GR's) going below 23~24 ohm is looking for trouble - knock city.
This is however a very useful technique to keep EGTs safe in tuning open loop - particularly when looking for the effect of leaning out AFRs whilst keeping EGTs safe. I have personally used this for some time, and can confirm that (at least for the GR's) going below 23~24 ohm is looking for trouble - knock city.
By checking afr sensor 1 current and afr sensor 1 resistance you may verify whether EGT is safe or not.
ECU tries to heat AF sensor to 750-800C by means of a heater. If EGT is greater the current drops. When current is about zero (0.1-0.2-0.3 amp ) sensor resistance reflects EGT value.
I personnaly ( and first Denso 32 bit ECU as well) consider resistance below 20 Ohm (first Denso AF sensor generation, probably about 25 Ohm for recent) under zero current as EGT extreme. I suppose this is about 850C+, some users report those digits.
From the other hand in case when ECU is not able to reach needed AF sensor temperature and AF resistance is greater than 30 (35 for recent) Ohm you have extremely rich mixture\low EGT that cools down your sensor.
Such a tune with AF sensor resistance of 22-27 Ohm (25-30 for recent ) under WOT is proven safe.