Quote:
Originally Posted by guybo
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What they say looks correct but it depends on how the ecu interprets the signal from the 02 sensor.
The 02 sensor reads lamda, it reads amount of residual oxygen in the exhaust gass, it does not know anything about afr.
The ecu get a signal from the 02 sensor aboit the residual oxygen, as a voltage or current reading this is converted by the ecu into an afr value by the ecu, have a look at the 02 sensor scaling table in ecu.
In our ecu its scaled to PETROL afr, and the ecu calculates everything reliative to petrol afr, these calculations are coded in the ecu program and not changeable by just changing tables
this is a rescaled table but for the exercise its ok
So the when your on 100% petrol the ecu calculated the amount of fuel to inject to get say lambda 1 (14.7 petrol afr) and all works fine and everything easy to understand.
When you run say full E85 and the ecu targets lamda 1(9.8 afr for e85) the 02 sensor doesnt know the difference as it reads lambda so it signals ecu lambda 1 and the ecu interprets this as 14.7 gasoline afr, but the ecu has to inject far more fuel to achieve this hence you need to alter the injector scalings to run e85 without huge fuel trims.
But when your on e85 the ecu or 02 sensor doesnt know it calculates everything same as it did for petrol, the afr tables are all still based on petrol afr and at stoic it will read 14.7 afr, even though the real afr is 9.8, as the ecu still thinks your running petrol.
When you run E10 fuel all that happens is your ltft, long term fuel trim will move slightly positive so ecu injects more fuel to keep the afr same as on straight petrol.
ive been on e85 for years and used torque and ecutek and tactrix and oft but they all read 14.7 cruising jist like petrol, jist the injector scaling is bumped up 30% to get the ecu to add the extra fuel without running 30% fuel trims.
