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Originally Posted by Quinn A
Ive had my Jb4 in for about a month now on my M8, on map 1 no issues, i only have BMC filers and secondary cat delete as of now but the car is notably faster.
What issues have owners been seeing?
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Won't see much issues reported on map 1. When you start pushing it harder is where you can get in trouble if your not careful. I am no expert but what I have learned is If you want try the higher maps/custom maps start logging on the jb4 app and look at your timing, afr and trims. Look for timing dips that indicate the DME is lowering timing because it's detecting knock (timing going to zero during shifts is normal though). At this point you can mix in some E85 gas to raise the octane, start with a few gallons and then watch your trims.
The trims are the short term Fuel Trims, the DME can raise or lower the air fuel mixture this way, since E85 has less energy density then normal gas due to the ethanol content, the DME will adjust fuel trims to compensate. It only has so much headroom to adjust however. That is why you just want to start with a few gallons and work your way up. E85's ethanol content can vary also (55-85 percent in many states).
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