Optima battery install changes handling

DByers · 07:08 PM

In my quest to lite'n my targa I recently (okay a few months ago) took out the two heavy batteries and went with the lite lb Odyssey in the smugglers box. The install was very easy and straight forward. I had done a CB and alignment before doing this (last fall) and I was hoping that I wouldnt have to redo that again. But those two batteries were HEAVY!!! And right over the front wheels. The relocation has now made the front a tad "light" as compared to before. It really showed up this past weekend when doing honey do's around the house I needed to get some tumbled rock for a planter project. That made a good excuse to get the 911 out for a quick drive. (Local dyi shop is 1.5 miles away, I was back just over a hour later

) Anyway the 40lb sack of rock sitting in the front compartment right where the spare would go made the front end "sit" again at hi speeds (over 70).
So I guess another CB/alignment is in order. Just goes to show you that one thing you thought would be a good upgrade can really upset the balance the 911 already has. Just some info for those who may think about this upgrade in the future.

edit to read Odyssey instead of Optima

AZNPLUMBER · 05-08-2006, 05:17 PM

I want to do the same upgrade, please give me some details.
Are u only using one battery now?

Thanx!

DByers · 07:08 PM

AZN-
Yes went form two heavy batteries to one lite battery. Shaved about 60lbs. Let me add that my 911 is a 71 so it had the two batteries from the factory that sat just ahead of the front wheels in the wheel well battery box's wired in series. These are/were extremely heavy. The install of the Odyssey(one battery)was very easy for my 71. I just took the passenger side line to the smugglers box. Dropped in the Odyssey and then tied the positve sides together in the drivers side battery box with a protected lug that allows for easy testing of the positve terminal (charge and draw) with out getting into the smugglers box. Overall a 30min task. The prblem is now my "balanced" 911 is no longer balanced as I have moved "polar weight" inward. This has led to the lightness I now have. I experienced the same feeling when I ran DE's with out my spare tire and tools years ago. 911's with a single battery may not experience the same effect as the earlier 911 may when doing this upgrade.
Perhaps someone with more knowledge on the lite vs. balance issue will chime in.

AZNPLUMBER · 05-08-2006, 06:15 PM

Thanx for the info! So Optima battery are u using?

DByers · 05-08-2006, 07:15 PM

AXN -
Had to edit, it was the Odyssey Battery PC680T not the Optima. Used that in my dads fishing boat when I wanted a lighter battery. The Odyssey is only 15lbs.
Also should note that my 71 is a has no power windows, no power locks, no power seats, no AC, no radio & all the extra that a radio brings, the heat is the early type. Never had a problem with the 680 cranking amps even after weeks of sitting. She starts right up.

Vipergrün · 05-08-2006, 08:43 PM

Hey Dan!! Wassup man? Is this with or without the duck? You have an "S" spoiler up front, dont ya? Maybe an ABS splitter from TRE? My car was really twitchy and light up front. I have added a 16th toe in to hold me over til I can get a real alignment. Much better feeling. Hope all is well.

anthony · 05-09-2006, 05:34 PM

Is the small Odyssey battery large enough to fully power an SC?

304065 · 05-09-2006, 05:51 PM

The handling is not necessarily better or more balanced, right?

My Hawker PC680 is going BACK in the port battery box from the smuggler's box after about five races with it there.

The pundits (I was one of those once) talk about "reduced polar moment of inertia" but it's BS, the factory knew what they were doing.

That being said, I have a fiberglass S spoiler up front and a fiberglass RS rear bumper so I've done all thee weight reduction I can and still remain legal (2249 minimum at all times during race weekends).

And I'm keeping the cast-iron weights in my '66, too!

Jim Sims · 06:14 PM

"Anyway the 40lb sack of rock sitting in the front compartment right where the spare would go made the front end "sit" again at hi speeds (over 70).
So I guess another CB/alignment is in order. Just goes to show you that one thing you thought would be a good upgrade can really upset the balance the 911 already has. Just some info for those who may think about this upgrade in the future."

Wait until you try driving 75 with a lightened front end and 1/4 tank of fuel in a good crosswind. Pulling the front condenser and guards, A/C lines and evaporator/blower from the smuggler's box is moving in the wrong direction too but for many it feels so righteous

One has to be careful or the "cool mods" one thinks they are making can move the car in the direction of a motorized wheelbarrow.

I have moved all my tools, spare parts, etc. as far forward in the front trunk as possible.

Vipergrün · 05-09-2006, 06:20 PM

Quote:

Originally posted by anthony
Is the small Odyssey battery large enough to fully power an SC?

Yes, I have the 680 in my clone and it's fine.

Vipergrün · 05-09-2006, 06:23 PM

Is the 60 lbs, especially since it was hanging out in front of the front wheels, enough to effectivley change the camber and toe? If not, that's why I am wondering if a splitter would help him, especially with a duck in the rear. I am guessing more neg camber and toe would help the 'lightness'...

DByers · 05-09-2006, 07:17 PM

Brad,WTF man!?!? Hows that green monster treating you? Ill have to PM you the latest on life.
I have to say the liteness of the car (she was 2150lbs before the battery change) has led to better response in cornering and braking. A planned roll bar will add some lbs but a fiberglass rear bumber and lite weight targa top should hopefully off set that. The CB and alignment that was done has also really brought the car to life. The balance is still there at low speed, its when we get above 70 that the "liteness" takes place. I havent run it with the duck tail in this config yet but plan to soon. I dont run the duck except for at the track and the fiberglasss S front does a decent job with or without the duck. 70 to triple digit speeds really bring out the lack of "down force" this 911T has but she does have a very balanced feel and predictable handling now and that makes her extremely fun to drive, even with the limited HP.