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Cindy'sRed3.7

Reflashing Tune, Alway Use Battery Charger

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Having read all the Bama and SCT instructions carefully and re-flashing my car quite a few times, along with reading numerous tune threads on that other forum, I thought I was pretty experienced and savvy at this. Today however thanks to FFM and Grimace I learned a critical fact that we all should've known, but it seems like only some of us did.

A good battery normally has a standing voltage of around 12.3 VDC without a load on it, but when you turn the key to the second stop to start loading your tune the load that is put on the battery drops the output down below 12 volts DC. Plus if you listen to the radio and don't turn off the Air Conditioning switch that will draw down the battery even further. If the voltage drops low enough you can ruin your PCM. The exact minimum voltage cutoff on our cars isn't know to me, but so far I've been lucky with an almost 3 year old battery in my 2011. Grimace recommends at least a 5 amp charger from years of experience doing this procedure, and that's what I'm doing from here on out. 

Just to check I hooked up my volt meter and checked my battery with no load and then with the ignition key turned to the 2nd stop. Even with the A/C off and Radio off the voltage immediately dropped considerably. Use a battery charger when loading a tune! Glad I learned this, It's not worth the risk.

 

 

 

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Yeah, before I even start the tuning process, all accessories and lights are off. I've never had a problem, but it's good just to be safe especially if your battery is a couple years old.

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That type of voltage change can start frying other compenents too, can't it?

What other components besides the PCM nastang? The engine isn't running and once you do start the alternator takes up the load.

 

Sent from my SPH-L720 using Tapatalk

 

 

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Having read all the Bama and SCT instructions carefully and re-flashing my car quite a few times, along with reading numerous tune threads on that other forum, I thought I was pretty experienced and savvy at this. Today however thanks to FFM and Grimace I learned a critical fact that we all should've known, but it seems like only some of us did.

A good battery normally has a standing voltage of around 12.3 VDC without a load on it, but when you turn the key to the second stop to start loading your tune the load that is put on the battery drops the output down below 12 volts DC. Plus if you listen to the radio and don't turn off the Air Conditioning switch that will draw down the battery even further. If the voltage drops low enough you can ruin your PCM. The exact minimum voltage cutoff on our cars isn't know to me, but so far I've been lucky with an almost 3 year old battery in my 2011. Grimace recommends at least a 5 amp charger from years of experience doing this procedure, and that's what I'm doing from here on out. 

Just to check I hooked up my volt meter and checked my battery with no load and then with the ignition key turned to the 2nd stop. Even with the A/C off and Radio off the voltage immediately dropped considerably. Use a battery charger when loading a tune! Glad I learned this, It's not worth the risk.

Thanks, I'm installing my 1st tune tomorrow.

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I always turn my accessories off before I turn the car off anyway, A/C, radio, headlights and fog lights, and disconnect my Aeroforce gauge...when I remember.

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Accessories are only a small part of the puzzle. Whenever the control units are awake they draw a lot of power.

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Robostang my Roanstang really likes the SCT 91 octane tune but, my speedo is high 10-15 mph? I returned to stock & "reflashed" using 755 rev per. I even changed the stock rear gear size to 3.08:1 thinking that might help but nope? Any suggestions ? My wheels are 18x9 on 245/45/18 and the revs chart says 756 revs, what gives?

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I replaced my stock Pirelli 235s to 245/45/18 Generals, it was actually cheaper to get the off size. Any way, when I adjusted the revs per mile on the tuner it didn't seem to take right, maybe it was the Bama tune. But I called Bama and had them rewrite for my 245 tire size and the shifting and MPH was spot on again. I wouldn't start messing with gear ratio, that will make for some crazy math equations to figure it out. If it helps as a temp. fix a little, but make sure to change it back to stock ratio.

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Ok, Cindy I did go back to stock, then used the "Skip" to preloaded tune, whatever that is? Now my speedo reads right but I don't know the parameters of the tune I have now?Thanks for your help,Alan

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also, if you have the navigation unit, you need to pull the fuse for it during the tune, otherwise when you try to use it, it will start complaining that you need to go to the dealer for a nav reflash (you dont, just pull the fuse for it in the passenger compartment floor.  top left, 1 down)

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