Battery relocation ideas

[mhoward1]

So after the first race after the upgrades and other changes it seems that there was too much weight taken off the front end of the car. This is a bit of a disappointment since the car was handling so well before hand, but I should have seen it coming considering how much lighter the new top end is. There is now significant under steer and the key indicator of the left front wheel locking up easily. Alignment was right so I think I can rule that out:

Left Total/Center Right
Front
Camber -2.9 -3
Caster 8.5 8.5
Toe - 1/16 - 1/8 - 1/16

Rear
Camber -0.1 -0.2
Caster
Toe 0 - 3/32 0.13


The car was balanced and cross weighted prior to the race and on paper looked to be decent, not great but almost perfect 50% cross weight.

Cross weight 50% 50%
weight Dist front 45% 44% 44%
weight Dist rear 55% 56% 56%

One thing I did not do though was account for fuel. The car has ~3 gallons in it when weighted. Once I added another 10+ gallons I know it threw it off, but even as the fuel went down there were issues.

Bottom line is I think moving the battery forward is the next step. Right now it sits in the rear. The easy answer is to move it to the passenger foot well, but I would like to keep the passenger compartment as is. So I would love to see other options that you guys have used. Posted pictures would be the best.

[CHOTIS BILL]

The best setup I found with my DSR was 47/ 53% front / rear with 61% roll couple in the front. With this setup no matter what spring package I ran the only change required at the track was adjusting the front sway bar 1/8” at most.

Bill Lomenick

[mhoward1]

Mark D just reminded me about no moving the battery


8.1 Battery
The battery must remain in the stock location on the passenger side of the lower trunk. The
battery must be 12-volt and may not be modified in any way. The battery has a minimum weight
of 25 lbs.

So now I need a different approach. Not sure if a spring change will solve all the issues I am seeing. I need to get access to a set of scales and remeasure with the correct fuel levels.

[FFRSpec72]

I don't like that rule would like to see this gone, as I should be able to meet minimal weight any way I can and need all the options I can to balance out the car.

[tirod]

It's a Challenge car issue - if extensive mods were allowed, then the class would become Open with no limits. Can Am cars could participate at the extreme, and budget racers would do just like they have at all the local dirt tracks - stay home. About 6 had to close because of the high end race teams taking 1st thru 6th and the back markers not even getting gas money to show up. So, they quit. If there's no chance of even breaking even, why bother?

On a street car, the rear battery location appeals to the "race car" motif buyers want. But, it is the point - the battery has no business being in the rear of a car with a rear weight bias to begin with. It's a case of monkey see monkey do, rather than understanding the real dynamics of how cars should be built.

I trunk mounted the battery in my '66 Mustang, where it would do some good, and should I be blessed to build a kit, I would put it under the hood on the Coupe where it balances better and works with more efficient, shorter wiring. For the Challengers, tho, the point is to build the kit as is and keep the costs down. The issue affects everybody, and that means it's fair under good rules of sportsmanship.

Otherwise, the $100,000 guys would dominate, and a few years of that would mean the death of the series. It also goes to the minimum weight of 25 pounds - keeps out the $250+ race batteries.

Besides, a good driver can make up the difference, right?

[mhoward1]

The series is filled with talented drivers. ;). The real issue is the upgrade takes about 80 lbs off the nose in an already rear bias car. When it was the stock 302 with iron heads and the like, the battery in the rear actually offset the weight a bit, especially the driver placement. It was still rear bias, but fairly close and allowed good off the corner acceleration. Now the bias has swung the pendulum and I don’t think I am the only one struggling with the issues. So now we are in a discovery and sorting phase. I am already over spec weight, but the option maybe to add ballast in the passenger foot well or other place in the car. I can also play with the rake to see how much effect I can get. My main goal is to make the car comfortable at the threshold limits again. We had gotten it nicely neutral at quick turn ins, and the braking was confidence inspiring this past season which made driving it a blast. With the brake lock up issue, and significant push it’s just not the same.

Give this though, I am open to suggestions.

[FFRSpec72]

It's a Challenge car issue - if extensive mods were allowed, then the class would become Open with no limits.

No there are already enough rules, we don't need rules like this, makes no sense to limit battery to a given weight which pretty much rules out the non lead acid batteries which are nasty when you get hit of they develop a crack. The placement should be a matter of balance. Time to toss the rule.

[avgjoe]

Everybody else has solved the problem, just ask around. In my opinion the rules need to remain stable. It may seem minor but so have some of the other changes through the years.

[mhoward1]

Everybody else has solved the problem, just ask around.

That’s why I am asking here. I am hoping some others will share their experience with this. By talking about it here, hopefully more people than just myself will gain value from the conversation.

[FFRSpec72]

Everybody else has solved the problem, just ask around. In my opinion the rules need to remain stable. It may seem minor but so have some of the other changes through the years.

Issues here is that there have been rule changes now folks are trying to recover from those rule changes, so when you change rules other rules may be affected that you have to consider changing. So I agree that rules should be stable but there have been changes and need to work through those and this is a case that needs to be considered.

[Jim Schenck]

On a street car, the rear battery location appeals to the "race car" motif buyers want. But, it is the point - the battery has no business being in the rear of a car with a rear weight bias to begin with. It's a case of monkey see monkey do, rather than understanding the real dynamics of how cars should be built.

A 50/50 weight bias is great for steady state cornering, but how ofter in a real situation is a car on track doing that? Certainly not more than 5 percent of the time. 80-90 percent of the time a car is either accelerating or decelerating and in both of those situations a rear bias is superior. Also for a car that can fit a much larger rear tire even the steady state balance works out better. On a car that can run a good tire split we usually shoot for a 42/58 front rear split, but on the challenge cars where the tire sizes are rules limited the 55/45 split allows a good balance between steady state turning and not giving up corner exit grip and great braking balance. (one of the cars strongest points)

Marty, on your car the reason you have developed a push is the inclusion of a front sway bar along with the new suspension, it may show up more with the additional power but it was there even before you changed the heads. The fast set up on the challenge cars seems to be migrating from about a 150-200lb spring split to about a 50-100lb split. I think that is what I would try first to get the car back to a good baseline and then fine tune from there. Something along the lines of 650 front and 550 rear is where I would start but it might depend on what you have sitting around and is easy to try.

[mhoward1]

Jim, What setting do you have the front sway on?

[mhoward1]

BTW, if a moderator would change the thread title please to what is relevant.

"Handling changes with the 2013 Spec Upgrades”

[Jim Schenck]

I run the bar on the soft setting for now but if you can get the car set-up the way you want it on the medium setting (one side on the short hole and one on the long) then you have a little room to adjust either way if conditions change. Just remember to disconnect the bar when you scale and only bolt it back on with the tires on the ground so you are not pre-loading the suspension in one direction.