Moderator help please-Predator tune and altitude

[dylzsrt]

I've got a 2009 chrysler 300 SRT8, and going to be running the AFE stage 2 intake and magnaflow highflow cats with the stock exhaust. My predator currently has the 9VR17 tune (i might be wrong in the order of numbers there).
I live at approximately 3500 feet above altitude.My question is,with the SRT8's running pig rich from the factory and with me being at high altitude which richens further,would I be better off running the 91 Performance tune with my CAI, instead of the 91 CAI tune (I'm assuming the CAI tune gives it more fuel)??? My theory is I might need things a bit leaner if anything as opposed to adding more fuel. The computer may compensate for all this but i'm not sure how much altitude changes that.
Any help would be appreciated

[duster360]

Altitude compensation for fueling is a pretty easy calculation for the PCM. I seriously doubt you'd have any problems.

I'd start with the 91tune and see how it goes. Simply add or remove fuel with the DSP in response to Knock retard.

[Quick]

Altitude might change WOT a bit... small bit.

In closed loop operation (partial throttle) the PCM will adjust the fuel using the narrowbands. This adjustment move the long term adaptives. In open loop operation (WOT) the long term adaptives are factored in.

Now... at WOT the PCM uses the base injector pulse width + the long term adaptive adjustment + a fixed amount of additional fuel from the PE (Power Enhancement) table. That fixed amount would be the same at any altitude. If you're running leaner to begin with due to the PCM adjustment that fixed amount might be just a little bit more than what you need but I would expect it to be a very small amount. You should be just fine. A little rich is better than a little lean.

You should get a wideband. Then you'd know for sure.
If you don't have a wideband and want to fiddle with it then log for knock retard.
If you don't see any then take out maybe 5% fuel and log for knock retard again. Once you start to see some measurable knock retard then add a little bit back just until it goes away. If you get a wideband you're looking for something around 12.0 (11.8 to 12.2) at WOT.
As above, the PCM will take care of closed loop.

[dylzsrt]

Altitude might change WOT a bit... small bit.

In closed loop operation (partial throttle) the PCM will adjust the fuel using the narrowbands. This adjustment move the long term adaptives. In open loop operation (WOT) the long term adaptives are factored in.

Now... at WOT the PCM uses the base injector pulse width + the long term adaptive adjustment + a fixed amount of additional fuel from the PE (Power Enhancement) table. That fixed amount would be the same at any altitude. If you're running leaner to begin with due to the PCM adjustment that fixed amount might be just a little bit more than what you need but I would expect it to be a very small amount. You should be just fine. A little rich is better than a little lean.

You should get a wideband. Then you'd know for sure.
If you don't have a wideband and want to fiddle with it then log for knock retard.
If you don't see any then take out maybe 5% fuel and log for knock retard again. Once you start to see some measurable knock retard then add a little bit back just until it goes away. If you get a wideband you're looking for something around 12.0 (11.8 to 12.2) at WOT.
As above, the PCM will take care of closed loop.

great info,thanks. I'll run the 91 CAI tune and then log for KR. Stock,my car took to the 91 performance tune very well, so hopefully with these mods it will be even better with the 91 cai.Gonna add a catch can as well.