Any benefit to running a bigger battery ?

[Bullit]

I'm currently relocating my battery to the front of the car and was wondering if there is any benefit to running a bigger battery ?

[Petrus]

I'm currently relocating my battery to the front of the car and was wondering if there is any benefit to running a bigger battery ?

It will take longer to discharge.
A quick (dis)connector is more effective though and both cheaper/lighter.

More weight up front makes the car appear more stable because more mass is slower in responding and more weight op front increases understeer. Putting the battery up front will be noticeable, but a slightly bigger battery, mwah, think not.
Depends on your driving and use whether the effects are a positive or negative for you.


Out of curiosity; why are you relocating the battery?

[Bullit]

I was hoping to counteract the front end lightness i feel at speed.

[Petrus]

I was hoping to counteract the front end lightness i feel at speed.

There seems to be some controversity about that. Some experience it and some not, or say they don´t.

Imo putting more weight up front is adressing symptoms, not the ´problem´. Between brackets as the word seems to touch sensitivities.

I chose to go the aerodynamics route.
This is also not generally accepted as effective but at the same time the effectiveness of Mongos is haloed so... you decide for yourself.

My logic is that if aero mods change pressure differences even only by a small percentage it is over a rather large surface so easily more than the weight of the battery.
Furthermore it is speed dependent which is as you want it and not slowing down responsiveness because you don´t add mass nor change weight distribution which affects the behaviour at all speeds.

As the sensation is in the steering wheel it appears to be at the front so I first vented the bonnet and added a rubber strip under the chin like just about no modern car goes without and Toyota also fitted post face lift.
Both these reduce the air pressure under the front of the car.
It helped but I concluded that the turbulence behínd the car is also a major contributor to the sensation.

Adding a ledge behind the rear lid provided a tear off point for the flow and it had noticeable positive effect. The optional Toyota ´ducktail´ is such too.
With these three small mods I found my car a lot more stable, even when passing a truck in strong sidewind from the truck side.
I would say this was enough to deal with the ´issue´.

For varied resasons I next added a large rear wing. The effect on stability was as large as the wing.

[Bullit]

Thanks, That's really helpful.

[Topdownman]

I would not have moving the battery down as my first step.

I would look at the tyre pressures and wear, then maybe have the alignment checked, then check bearings/bushes/ steering UJ to make sure there is no play there (you might be able to get the alignment place to check the bushes etc). The under car spoiler that Petrus mentioned has a marked effect so check you do have one.

Then think about the age and condition of the shocks and springs, if they are originals then this may be the problem.

Bonnet vents are good but you have to remove the froot plastics so the air can flow (this makes it easier to check the steering UJ).

You could try adding some extra weight in the froot to see what the effect of moving the battery would be, say about 10 kgs? (But do secure it!).

[Bullit]

I've been chasing with for a while and have already replaced all bushes, 4 new types (toyo proxy) and an alignment. My car also has a trd front lip but i don't know how that compares to the facelift under spoiler.

[Petrus]

I've been chasing with for a while and have already replaced all bushes, 4 new types (toyo proxy) and an alignment. My car also has a trd front lip but i don't know how that compares to the facelift under spoiler.

The TRD lip is sufficient. I is meant to only slightly block/disrupt the flow of air pushed únder the car by the front bumper shroud. It will decrease the pressure under the only a bit.

The air flowing though the radiator can only escape underneath the car and thus increases the pressure and this gets worse as the speeds increase. This illustrates the car feeling lighter up front as speeds increase.
The sense in venting the bonnet is obvious ;-)  Yes, with the vanity plastic out.

Let´s assume that the pressure under the car without a lip is 1 bar = 1 kg./cm2 and fr calculating ease we take the under car surface a 1 m2 = 10.000 cm2.
If the pressure under the car at speed can be kept even only 10% lower, then that is 0.01 kg x 10.000 = 10 kilo of ´downforce´. This effect increases as the speed increases, counteracting part of the ´lifting´ effect.
Note that for the explanation it does not matter what the actual pressure under the car ís, but it is higher than atmospheric so a % reduction is more kgs too.
Ergo the lip easily equals the battery up front but without adding weight there.

Back to your car.
Try a lip behind the rear lid. A simple few cms high rubber stick on one is enough as it is not meant to work as a spoiler/air foil but only to provide a tear off point at the top rear edge of the round bum. This reduces the turbulence behind the car, in effect stabelising it. It´s like chasing off the big guy randomly pulling/pushing the back
If you like the effect but not the look then you simply pull it off and fit something you find more pleasing.

[Petrus]

About the silly big wing.
Again controversial because of the common wisdom that aero only works at high speeds.
The reasoning is founded on the truism that air resistance, aerodynamic drag is proportional to the square of velocity. In other words the faster you go, the more more air drag there is.

However...

First: There is drag as soon as there is ány movement of air past thus around an object, obstruction of the flow.
This is why bágs of money are spent on aero in cycling. Ccling aero bikes make a notable difference from some 25 km/h air speed.
Mind, that is small frontal areas, low speed and it makes surprisingly large differences in the power needed.
I have a Shimano AX bicycle from 1981 which was an aero showcase bike with oval tubes, trick pedals, aero bottle and other clever innovations to reduce drag. It took nearly four decades to get through to mainstream enthusiasts bicycles 



Whoever is still not convinced has neither been out cycling solo vs in a group nor watched cycling: Slipstreaming makes a world of difference at sub moped speeds!!


Secondly: The surfaces on a car are húge! A simple lip under the front of the Spyder is 480 cm2. Thry stick a large diner plate out of the window at 60 km/h and you will feel what drag it has.
That drag can be directed, modified, used.

Thirdly: The Bernoulli's principle, sometimes known as Bernoulli's equation, holds that for fluids in an ideal state, pressure and density are inversely related: in other words, a slow-moving fluid exerts more pressure than a fast-moving fluid.
Air to all extends and purposes behaves like a fluid concerning flow.
This is what makes airplanes fly: The speed difference of the air passing over vs under the wing.
A rear spoiler/wing is an inverted airfoil; inverted aircraft wing.
I became convinced of the effect of this from low speeds through my son´s model airplane hobby: 3-4 kg  airplanes with 2500 cm2 wing surface taking off at 20 km/h.
A silly big wing from ebay as I have mounted is almost 4000 cm2. Go figure how much that pushes down at 80 km/h even without the increased efficiency from the rear lip.

Lastly have a look at:
https://www.youtube.com/watch?v=9tvFcqV377I
By all means all of it but the crux is from 8:27.
Just watch the hands cornering at 80-90 km/h: Quite a lot more stable. I can totally confirm this pleasantly better planted rear end with a silly big wing costing less than 100€.

No, I am nót trying to convince anyone to fit a silly big wing. I ám trying to relativate the truïsm about aero only working at higher speeds. It wórks from zero BUT it has several effects, some ´contrary´ like the negative lift from an airfoil as a rule negatively affects the air resistance. Meaning that for rácing use whether it ´works´ (in lap times) is a trade off between traction and speed. On the road that is traction, or if you choose safety, and fuel economy.
Also we are not talking doubling G-forces through corners here. For thát you need air speed yes but for noticable effect it works at road legal speeds already.
The MX5 youtube is a good example imo.


Bottom line; Never mind the battery, try faffing with aero

[Petrus]

Dug through some info and a rough equasion taking ´worst case´ numbers is that the negative lift of my rear wing transcribes as  L = 0.4 x V2.
L in Newtons
V in m/s
meaning that at 100 km/h the wing pushes down with just over 30 kg.
Mind, that is rounding off everything down so at least 30 kg.

No, that does not sound like a lot in the perspetive of several Gs of F1.
BUT!! This not F1. This is about a bit more rear traction, a bit more stability at legal road speeds.

The weight distribution front/rear of the Spyder is 43/57.
I have taken about the same off front and rear so with rider and half full tank the weight on the rear is about 570 kg.
Making 30 kg. 5.3% extra downforce at the rear at 100 km/h.

Now the myth of needing a turbo to push the wing through the air.
The extra drag caused by the airfoil theoretically is a about a tenth of the negative lift.
The lip and wing reduce the turbulence though and this máy reduce the drag.
In any case the extra drag from the wing is not going to be noticeable in fuel economy in legal road use.
It wíll reduce the top speed and it will be noticeable at the pump if you empty the tank driving 160 km/h.
To put that into perspective, the extra traction improves accelleration to max highway speed more than the extra resistance slows it down. Especially accellerating from corners.

Oh, and as Mountain Girl is quick to point out, there is the braking. Reducing speed the extra resistance, added traction and increased stability work together in reducing stopping distance and it doés add up. Say 50 meter stopping distance from 100 km/h means 2% is a meter.  You can translate that to stopping on the edge of the tarmac versus in the ditch or to a cyclist scooped onto the bonnet or not.
Even when trundling along 1% reduction off 30 meter is stunning from just a silly wing.

So, the ham questions:

1. Does it work?
Yes ofcourse it works!

2. Does it work enough?
You decide. For mé it does.

Bonus question:
Ask the wife whether on average 2-5% less stopping distance is worth 100€....
Is a good one too when buying summer rubber.

[Beachbum957]

One factor to consider is the car is very light and the steering has considerable power assist.  So the basic characteristic will be light responsive steering.  However, if the front feels lighter as the speed increases, that is an uncomfortable feeling.

We have a 2002 Mr2 and a 2003.  Both are set up somewhat differently as far as suspension, and both behave differently as far as front end stability. Both have the factory front lip underneath and no other aero changes. Both have the same tire and wheel package.

One thing that helped both was the tire package with wider 16" wheels (7" front and rear) and slightly wider and lower profile front tires at 195/45-16.  Steering was more responsive with less "wander".  The stability was also greatly impacted by tire pressures and we ended at 28-29 psi front and 34 psi rear.  Anything higher in the front made the front a bit too sensitive

The 2003 feels very stable at speed, and the stability doesn't change much with increased speed.

The 2002 originally was is a bit "floatly" at highways speeds. It was lowered with Tein springs, and that improved front end stability considerably. Part of that was attributed to the increased rake as the front was lowered a bit more than the rear. This thought was reinforced when The front was raised slightly for ground clearance and the stability was reduced a small amount.

But the biggest impact after tires was alignment.  The 2003 has stock springs with Konis and runs cambers and front toe in right in the middle of the factory specs.  The rear toe is at 0 toe in.  The 2002 runs the same front toe in as the 2003 but a bit more rear toe in.  The 2002 also runs negative camber near the max negative in the factory specs. 

The 2002 is noticeably quicker responding but less stable at speed than the 2003.  Experimenting suggests setting the camber less negative and toe near the middle of the specs improves stability at the expense of the quick response

Overall, the car seems very sensitive to small changes, both in camber and toe.  If the alignment shop just gets it "in spec" (which is pretty wide), that may not be good enough

[Petrus]

One factor to consider is the car is very light and the steering has considerable power assist.  So the basic characteristic will be light responsive steering.  However, if the front feels lighter as the speed increases, that is an uncomfortable feeling.

I took the p.a.s. for way better steering response and less twitchyness.

The 2002 originally was is a bit "floatly" at highways speeds. It was lowered with Tein springs, and that improved front end stability considerably. Part of that was attributed to the increased rake as the front was lowered a bit more than the rear. This thought was reinforced when The front was raised slightly for ground clearance and the stability was reduced a small amount.

Yes, the rake improves stability a lot. This illustrates that in OEM set up the front ´lifts´.
when adjusting ride hight to the weight reduction, I did the back a few mm. less than the front.

Yes, the larger, wider 16" rear is just that wéé bit more stable, less quick.

[BahnStormer]

Surely better to ask the other question: can't you just fit a smaller, lighter LiIon battery in the rear?

[Petrus]

Better LiFe; way safer in car application.