Determine what New Springs are Needed for Additional 500lbs?

[anhanymous]

Ppssssshhhh. Nahhhh. He has got this. I am sure a high output alternator was already on his short list along with some other supporting items.

Cannot wait to see how this turns out

lol yeah, if he is going as far as to modify spring rates and what not, this project had to be well thought out. Meanwhile... im over here and have no idea how to install an upgraded sub and amp

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[Micah]

Just a thought for OP. Why not pull the back seat entirely and install everything back there, possibly with a cage to help stiffen the chassis. This would help center the weight and offer better acoustics. Less trunk rattle issues too. Then you could either upgrade both front and rear suspension, or possibly get away with keeping the stock suspension.

 

[JW0914]

Yeah... that's way overkill and unnecessary.

The main reason for asking about beefing up the rear suspension is because it's electronically controlled, otherwise I'd do what I did with my other car and upgrade to coil overs.

 

[Micah]

"JL12W7s, 4 Slash amps, woofer box (100lbs on it's own due to having to be double walled for the W7s), extra battery, bat caps, amp rack" - arguably also way overkill and unnecessary. The affect on handling, braking, and acceleration from an addition of 500 lbs to a car in cabin vs the trunk.... definitely interested in how this turns out. Please post pics.

 

[JW0914]

"JL12W7s, 4 Slash amps, woofer box (100lbs on it's own due to having to be double walled for the W7s), extra battery, bat caps, amp rack" - arguably also way overkill and unnecessary. The affect on handling, braking, and acceleration from an addition of 500 lbs to a car in cabin vs the trunk.... definitely interested in how this turns out. Please post pics.

You clearly have no clue about custom car audio.

• 2x JL 1200/1V3s are 1200W/ea
  • 2x JL 12W7's are 1000W/ea
  • Woofer box must be double walled, else one risks literally breaking the box, and MDF is not light, and neither is 1" thick fiberglass

• Either 2x JL 300/4V3s will be bi-amped or a single VX800/8i
  • 4x 3-way C7's will be under-powered by ~100w

• JL FiX86 is required to remove the DSP that factory tuner has horrendously applied. I' haven't yet decided if I'm going to do the Twk-88 as well.

• Extra battery is to prevent stressing a single battery, of which would increase lead sulfate buildup rates, increasing the likelihood a battery will eventually short a cell or cells.

• BatCap is required as capacitors are made to charge and discharge current extremely fast, of which helps to offload large current spike requirements from the battery

• Motorized amp rack homogenizes the build with custom aesthetics

• Per Ohm's Law, an extra ~180A are required to run the wattage I'm tuning the system to (~2600W), hence the $600 custom built 280A alternator from Ohio Generator.

So yes, I know what I'm doing. As to how it affects a vehicle's drive ability, not a whole lot... it's no different than having 3 passengers in the car during every day driving. Again, I'm only concerned with the rear suspension because it's electronically controlled.

 

[erbee]

I mean , there are other cars better at this .

7screens total , neon lights inside

Used for mobile party karaoke station.

5 speed release series2.0

 

[Micah]

http://www.hendonpub.com/resources/article_archive/results/details?id=3486

 

[totopo]

How would I go about determining what new spring constant I would need for the rear suspension from adding an additional ~500lbs in the cargo area? Would I also need to upgrade to beefier shocks?

• This post states the OEM spring constant is 245.83lbf/in... I doubt it's as simple as adding 500 to that number.

So your goal would be to keep the same ride/wheel frequency.

from the formula: http://www.optimumg.com/docs/Springs&Dampers_Tech_Tip_1.pdf
You can see you can keep the same wheel frequency by matching an increase in sprung weight by proportionally increasing the spring rate.

So assuming the added weight is directly on top of the rear suspension, and ignoring the difference between right and left, and guestimating unsprung weight, we can calculate it from the front/rear weight distribution and the curb weight.

You don't say which model you have, but for example, an EX hatchback without honda sensing has a curb weight of 2950lbs and a rear distribution of 39.4% we get rear weight of 1162.3 lbs. Using a random guess of 50lbs x 2 as unsprung weight leaves about 1050lbs as sprung rear weight. So adding 500lbs is adding about 48%m so if 245.83 (dun wanna double check) is the spring rate, you want a spring rate of around 363 lbf/in

Adding all that weight in the rear will cause it to be way more neutral oversteer. You can do the math and get a weaker rear anti-roll bar or a stiffer front to bring it more to OEM spec...

edit: also, the shocks will then be horribly under-damped and the ride will feel super bouncy and be like crap. You need to get matchingly valved shocks for that ~50% increase in spring rate.

 

[Micah]

You clearly have no clue about custom car audio.

• 2x JL 1200/1V3s are 1200W/ea
  • 2x JL 12W7's are 1000W/ea
  • Woofer box must be double walled, else one risks literally breaking the box, and MDF is not light, and neither is 1" thick fiberglass

• Either 2x JL 300/4V3s will be bi-amped or a single VX800/8i
  • 4x 3-way C7's will be under-powered by ~100w

• JL FiX86 is required to remove the DSP that factory tuner has horrendously applied. I' haven't yet decided if I'm going to do the Twk-88 as well.

• Extra battery is to prevent stressing a single battery, of which would increase lead sulfate buildup rates, increasing the likelihood a battery will eventually short a cell or cells.

• BatCap is required as capacitors are made to charge and discharge current extremely fast, of which helps to offload large current spike requirements from the battery

• Motorized amp rack homogenizes the build with custom aesthetics

• Per Ohm's Law, an extra ~180A are required to run the wattage I'm tuning the system to (~2600W), hence the $600 custom built 280A alternator from Ohio Generator.

So yes, I know what I'm doing. As to how it affects a vehicle's drive ability, not a whole lot... it's no different than having 3 passengers in the car during every day driving. Again, I'm only concerned with the rear suspension because it's electronically controlled.

Riiiiiiiight.... personally I am very interested in how this turns out. But you posted all this in a thread about how the suspension is going to handle an additional 500 lbs and so far as the details of what you intend to put in there....

 

[JW0914]

@Micah If you don't care, then stop trolling =]

You don't say which model you have

I posted in the FK8 forum, so a CTR =]

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