4wheelkillr

Installed my C&L and diablo from RPM a few weeks ago.

I've heard lots of good stuff about power and response from Brent and Fred but there are no SCT tuners in my area....

Anyway, right out of the box the so called "performance tune" from Diablo is just plain GARBAGE. IMMEDIATELY thru a CEL. Took in to my local Diablo tuner here and put it up on the Dyno.

First run a/f ratio was over 15:1...yeah that's WITH the tune from Diablo that's meant for the CAI. So of course we shut it down and started playing with the a/f ratio. At WOT, it sits perfectly at 13.0 a/f all the way thru the rpms to redline. What my tuner did he said is adjust the map volts? to get the closed loop fixed at WOT. He said that it will not de-tune itself over time becuase it's closed loop WOT settings. Adjusting the open loop a/f settings will detune because those are the parameters the computer adjusts at idle and acceleration without WOT.

Now the issue seems to be that when you're NOT at WOT it throws a CEL. At loafing inner city speeds it throws a CEL pretty quickly. And when I read the codes: system too lean bank 1, and system too lean bank 2. So I'm guessing it's the open loop settings that need to be adjusted also.

What's more, is that I friggin LOST power at rpms under 2750!. When comparing baseline dyno to tuned and adjusted dyno I gained 12 HP and 13 tq max! But the new power and torque curves dont cross and exceed stock power/torque curves until around 2800 RPMS.

My tuner said I just need to disable the REAR O2 sensors that are behind the cats because they do absolutely nothing and are responsible for reporting the lean codes.

My questions to you tuning pros out there: Does all of this make sense? Should we not also adjust the open loop idle and non-WOT settings? How does turning off the rear O2 sensors alleviate the problem? If they're reporting a lean condition at less than WOT, that's probably because there IS a lean condition? Does this really matter if it's NOT WOT? I've heard that a/f and timing is most important at WOT, but is a/f and time completely irrelevant at other throttle settings?

I can do mechanical work and turn wrenches all day long but when it comes to this computer and tuning...it's all over my head.....so help me out if you can!

Thanks,

Chris.

MusiccityGT

Wow, never heard of this many issues with a Diablo tune. The short and long term memories in your tune should have been saet at 0. This allows the computer to "learn" a/f settings based off of the 02 readings in open loop, or less than WOT. You are correct that the WOT depends on a/f maps and fuel curves programmed into the computer. Sounds like your fuel curves at lass than WOT need to be adjusted. The feeling of lost power in lower rpm ranges is due to aggressive timing settings. Your torque curve has moved up the range and it should pull like a bear at 2500 and above. I have an aggressive custom Diablo tune and have all of my 02's on and active. Never had a cel light. Get someone in the know to do a live time download on your Predator to check your A/F readings at WOT and less than WOT. Anytime I make a change, I swing by my tuner and have him do that to check my a/f and make any needed adjustments.