2013 Boondocker 3D box goes lean after 2 seconds

[jgw50]

I have a new to me 2010 Twisted Turbo M8 with a 2013 BD 3D turbo box. (The previous owner replaced the original attitude fuel controller)

If I do a wide open pull, the afr stays right around 11.8 for two seconds, then it swings lean to the point where it doesn't even read numbers on the afr. It does this on any boost level and with any fuel controller numbers.

You can watch the little leds on the afr swing from around 12, then shoot all the way lean.

The sled still pulls and runs awesome even when it reads lean (I didn't dare hold it for more than 1 second after going lean) with no popping, no Det light, no signs of running poorly (running straight 100ll avgas)

I upped my fuel numbers to 100 at higher rpm to see if I could bring it down and it had no effect.

I have two hypothesis...
One is that it is actually running rich enough for incomplete combustion and the wideband registers the extra o2 as being lean.

The second more likely one is that the fuel controller either isn't pushing the secondary injectors or doesn't have enough power. I found some old posts talking about power issues with the 2013 BD boxes.

Anyone ever seen anything similar?

 

[rcr1978]

Some things to check

O2 sensors read lean when they go bad, sometimes the junk ones will work ok when they are cooler but when they get a little heat they will read lean. Hook the the wide band controller up to a battery, pull sensor from the exhaust, let it warm up then try using a lighter and squirt the gas in the end of it (don't light) it should read way rich. It will go way lean when removed, if this appears to work ok then heat the end of the sensor with the lighter don't be conservative you may need a little butane torch to get enough heat, it should be reading rich when you cover the end with the flame if it starts doing weird things it's junk it's usually pretty obvious.

When the wide band says you go lean you should feel the sled lay over, backfire, and more then likely would get det codes that's why I suggested the above test or just go grab a new sensor from Vatozone I like to have a spare as a test anyways.

What kind of fuel pumps and regulator do you have?

 

[jgw50]

Thanks, I like the idea of just replacing the sensor. It reads so well most of the time I thought it was likely not an issue but I like the idea of ruling it out.

I'm running twisteds internal fuel pump with the msd external fuel pressure reg. Fuel pressure rises with boost and doesn't drop off so I don't think it's fuel pressure.