Disconnecting the battery

[pajeff02]

Kind of an oddball question:

When I transport our car to and from the track I always disconnect battery. Once at the track, I reconnect the battery and then drive the car a bit in the pits to let things settle in again. It always starts and immediately stalls, but on re-start things smooth out and she runs ok. I understand that the PCM has to adjust itself based upon engine sensor feedback and I think Frost once posted that it takes these things a while to really return to optimum. Obviously, rolling up to the line and standing on it after immediately reconnecting the battery is probably not a good thing.

What do you guys do?

[transamtom]

I don't tow my cars so I don't have that problem.

If I work on the 4th Gen and disconnect the battery I have a long drive to the track of 45min to 1hr with mixed city and higher speed country roads so I am usually good to go.

Although on the 5th Gen I always do the 5-20 fuse pull to reset the computer for high octane mode as even one batch of bad fuel with a round of spark knock will put them in 87 octane mode.

[pajeff02]

I installed a disconnect switch last night that I picked up at Carlisle over the weekend. I was getting nervous constantly removing and installing the bolt on the negative cable.

[Firebirdjones]

I don't disconnect the batteries when towing

Any particular reason you want to do that?

To answer though, I believe your fuel trims would take quite a while to settle in, enough that a simple drive around the pits wouldn't do. The way I understand it, even though WOT doesn't use the 02 sensors (open loop) It will however take the last 02 report (fuel trims + or -) at the moment you wack the throttle and add that figure to the set WOT AFR. So if your fuel trims aren't close and are taking big swings, you could have some wacky WOT AFR's that would contribute to the car not being very consistent from one run to the next. Might be rich on one run and not so much on another run depending on how far the 02's are swinging.
That's how it was explained to me on HPtuners website. So it's important to have your part throttle fuel trims spot on. Or do what I do, and run an SD tune in open loop all the time so I command the AFR's that I want, and the 02's don't fudge my WOT AFR's, so I don't have to worry about it. I find the car runs much better this way, and I like the snappier throttle response that comes with it as well.

[0rion]

have you done an idle tune on it? What cam are you running? I know on mine it'll sit all winter without the battery hooked up and then in the spring it fires right up and finds idle. It may idle like ass for the first 10 seconds or so but it never stalls and smooths right out. You could then put it in drive and let it idle there a minute or so and your idle should be good to go after that. I agree with FBJ.....I don't really see the reason or gains to be made from unhooking it in the first place for the drive. It's not like you would be in the position where the battery would tip over or anything....if so then having the battery hooked up would be the least of your concerns.

[Firebirdjones]

Lol, that what I was thinking, if I flipped that puppy over I wouldn't be crying about the battery

[pajeff02]

I definitely do not want to be posting pics like Jeremy did recently of the trailer laying on its side!

I just feel better going down the road knowing that all is ok with the battery unhooked. Plus, there are times when the car will stay on the trailer for a week or two between track outings. My trims all run real close to zero - been a while since I last looked at them. No cam or anything like that... yet.

[Firebirdjones]

Ooo, trailer on it's side doesn't sound good, hate to hear that.

I figure since I leave the batteries hooked up on the cars with tenders on them in the garage at all times, I figure it's okay to leave the batteries hooked up in the trailer when I tow. But certainly not a bad thing to unhook if it gives you piece of mind

[01badbird]

I have disconnect and have shut down to work on and also believe takes abit to relearn and wonder if the plug in 9volt thing they have when you change batteries so you don't have to reset everthing would work. heres a pic

[01badbird]

for more info but if some supporting company here has one I would go that way! Performance Tool W89203 - Computer Memory Keeper | O'Reilly Auto Parts

[pajeff02]

I am afraid my car would suck a 9 volt battery dry pretty quickly as we have a draw on the electrical system. I just haven't taken the time to track it down yet.