Originally Posted by bmw335idizzle
So I've been reading a lot regarding the Vishnu flex fuel kit and how it's really safe compared to the other piggybacks out there when it comes to mixing e85 with 91. Is the Vishnu flex fuel kit better and safer than using jb4 map 5 when mixing?
The JB4 is held back by the OEM fuel table's (which means E30-E60 depending on the particular car) w/o their back-end flash and relies on simulated lamda feedback to adjust OL to keep target A/F ratio. The target boost is adjusted base on monitoring (but not adjusting) the ignition timing curve on cyl 1. IIRC, E85/91 octane + DCI put down about 420rwhp on a dynojet, below what Vishnu's flex-fueled vehicles are putting down with their ability to run higher ethanol content.
Both are safe, but the Vishnu is easiest because it's a set it, and forget method. The JB4 requires some monitoring every once in awhile, but I've set it and forget it for the past 4 months after finding a reliable E85 source. Auto adjustment on the JB4 only occurs in 3rd-4th gears between 4,000-6,000rpm at WOT, something that I recommend 10 mins after every fill-up if you decide to keep the JB4.
Poor some in the tank and enjoy, start off slow. From my testing w/o methanol:
E20 cleans up timing up to 14.5 psi
E30 cleans up timing up to 15.5 psi
E40 cleans up timing up to 16.5 psi
E50 cleans up timing up to 17.5 psi
Power from any up'd ethanol content will bring a smile to your face. Take your pic and don't make the decision get complicated, it's a very simple task, this is from an "experienced" E85 user.