Quote:
Originally Posted by shags
as a new 2015 lfx owner i have heard many conflicting things.. iv'e always used 91 in mine for the last month since i have bought it then someone told me the motor is only tuned for 87 and putting 91 or higher in won't do anything unless you do a fuse pull with 91 in and let it set then the computer will change is this true ?
|
I've tuned both Camaro V6 engines, the LLT and LFX. The LFX tune has 2 octane tables, high and low. When a fresh tune or ECU is reset (fuse pull) the Knock Learn Factor is at 0.00, meaning it uses 100% High Octane timing table. When knock is detected, the knock learn factor increases based on the amount of timing being retarded and starts to blend the 2 tables together. If the knock retard has to be constantly active, the knock learn factor will hit 1.00 and the low octane table will be used all the time. If the knock sensors are deactivated, the low octane table is used.
On the LLT, it is only tuned for 91 octane (99% can't understand the Bosch ECU) and uses the knock sensors to run on 87. It will remove timing till it doesn't see knock, but the problem is it has a huge recovery time. The max timing removed can be 12 degrees (below 6000 RPM, higher RPM's is 15 degrees) and can take over 2 minutes to remove that knock retard.
The LLT is 11.3:1 compression ratio, the LFX is 11.5:1, the only reason they can run 87 octane is direct injection and very sensitive knock sensors.