U7137- return to stock before tune?

[HoustonHemi]

Im sure this has been asked before but cant seem to find it. Do I need to return my truck to stock before I change between 91 and 93 tunes and also modifying them?

[Quick]

Short answer: No.

Just select the other tune you want to load and load it. The Predator will see that a different tune has been selected and ask you if you want to reset parameters. What it's talking about is whatever parameters you may have changed for the previous tune. If you reset parameters the changes are cleared and the new tune is loaded as is. If you do not reset parameters then those same changes will be applied to the new tune you're loading.

So... the difference between the 91 and 93 tunes is basically timing (maybe a/f? but I don't think so). If you made fuel and/or timing changes to the 91 then you might want to reset them and start over with the 93. If you only made fan changes for your 180* T-stat to the 91 then you might want to leave them since you'd want the same for both tunes.

[HoustonHemi]

Thanks for the response. I didnt think so but wanted to make sure. As the AFs being different between the different tunes, that may be true. I know before the prediator my AFs were in the 13s then whith the 91 installed it went straight to 12.2. After a while I installed the 93 tune and my AFs were back to the 13s, added fuel and got it back to 12.2. But I did not really allow much time between the two tunes so that could also be the cause.

[Quick]

Thanks for the response. I didnt think so but wanted to make sure. As the AFs being different between the different tunes, that may be true. I know before the prediator my AFs were in the 13s then whith the 91 installed it went straight to 12.2. After a while I installed the 93 tune and my AFs were back to the 13s, added fuel and got it back to 12.2. But I did not really allow much time between the two tunes so that could also be the cause.

I think you need way less than a minute after it's warmed up .

[HoustonHemi]

Thanks for the response. I didnt think so but wanted to make sure. As the AFs being different between the different tunes, that may be true. I know before the prediator my AFs were in the 13s then whith the 91 installed it went straight to 12.2. After a while I installed the 93 tune and my AFs were back to the 13s, added fuel and got it back to 12.2. But I did not really allow much time between the two tunes so that could also be the cause.

I think you need way less than a minute after it's warmed up .

Lol. I had about 20 miles in between.

[Quick]

Once you get past the initial startup mode and the PCM starts monitoring the narrowbands you can see the a/f moving up and down on your a/f gauge. The short term adaptives are updating at least that fast (every so many milliseconds). It constantly cycles between rich and lean (for the narrowbands that's somewhere between low 14s and high 15s). It appears to cycle about 2 times a second. The long term adaptives are updated off of the short term adaptives. I think they're fully adjusted in under 6 seconds?

[HoustonHemi]

Once you get past the initial startup mode and the PCM starts monitoring the narrowbands you can see the a/f moving up and down on your a/f gauge. The short term adaptives are updating at least that fast (every so many milliseconds). It constantly cycles between rich and lean (for the narrowbands that's somewhere between low 14s and high 15s). It appears to cycle about 2 times a second. The long term adaptives are updated off of the short term adaptives. I think they're fully adjusted in under 6 seconds?

Yes it does seem that way. I had my afrs dialed in then it changed on me guess it learned my short terms. Changed it again and the afr is straying the same around 12.2.

[Quick]

Just in case you're not clear on this.

You have some base injector pulse width (base). That's some constant value in the PCM image.

In closed loop operation (cruising mode for example) the PCM uses the narrow bands to adjust for 14.7:1 AFR. It uses the short term and long term fuel adaptives to do this. (base + long term + short term) should get you to 14.7:1. Actually the short term ocillates so you bounce around approximately 1 under and 1 over but you can ignore this. Basically the PCM is just setting the long term adaptives to adjust to 14.7:1. It does the ocillation because the narrowbands cannot tell you how much you're above or below you are so the pcm constantly adds and subtracts fuel to drive them from rich to lean. Average that out and you have the adjustment to put in the long term adaptives. This way your car runs fine in closed loop at sea level or 2 miles up in the mountains, in summer heat or winter cold.

In open loop operation (WOT mode for example) the PCM does not monitor the narrowbands and does not update or use the short term adaptives (and therefore does not update the long term adaptives either). In WOT operation the PCM adds the fixed amount of fuel specified in the PE table (It's the PE table that you are modifying with the Predator when you add or subtract WOT fuel). (base + long term + PE table gives you your WOT AFR).

Outside of torque management, shifting, etc, etc, the tunes are mainly changing WOT timing and fuel and the car takes care of itself in closed loop operation. The main difference between the CAI and non-CAI tunes is fuel. The main difference between the 91 and 93 tunes is timing. Both can effect your AFR.

But once you get a WOT AFR with a tune you would not expect it to change without a significant change in altitude or weather. I only have 91 octane fuel available so I've never tried the 93 octane tune.

By the way, if you're in the mood to experiment you might try going 11.9 - 12.0