tank size question?

[Lombardi]

Hey guys new to the forum and to air ride so i had a question. I have a 2010 camaro I'm currently in the process of bagging with a air lift kit with V2. I've been planning how I'm going to setup my trunk and I really want to still be able to utilize my trunk space. I saw a setup in another camaro I liked and was wondering if I would have any issues with a smaller tank? Its a 3 gallon tank and fits in the spare tire space perfectly. Let me know what you guys think or if you have any other ideas to help me out.

If people are interested I might start a build thread as well.

Thanks

[Oh Damn, it's Sam]

You might be able to get away with a 3-gallon tank if you run it at 200 psi, but it depends on your setup and your expectations. I run a 2.5 gallon tank at 200 psi on my W124, which is a very heavy car, and I get away with it, though I am constantly wishing I had more air.

If you're willing to dig up some specifications, we can actually calculate whether that tank size will be sufficient, and at what pressure you'll need to fill it to. For this, we need bag diameter and height, and whether there's any through hole for a shock or strut (or even better, part numbers), vehicle curb weight, weight distribution, and the motion ratio of the suspension at the bags. If you can get that data, the calculations are relatively simple.

EDIT: It would also be helpful to know the maximum rated pressure of the tank you're looking at.

[Lombardi]

You might be able to get away with a 3-gallon tank if you run it at 200 psi, but it depends on your setup and your expectations. I run a 2.5 gallon tank at 200 psi on my W124, which is a very heavy car, and I get away with it, though I am constantly wishing I had more air.

If you're willing to dig up some specifications, we can actually calculate whether that tank size will be sufficient, and at what pressure you'll need to fill it to. For this, we need bag diameter and height, and whether there's any through hole for a shock or strut (or even better, part numbers), vehicle curb weight, weight distribution, and the motion ratio of the suspension at the bags. If you can get that data, the calculations are relatively simple.

EDIT: It would also be helpful to know the maximum rated pressure of the tank you're looking at.

thanks for the reply. when I get home from work tonight I'll gather all the information I can find on my kit. thanks

[Oh Damn, it's Sam]

When you've got that data, the calculations are as follows:

Get your approximate bag pressure at ride height for all four bags with the following function:



where:
wc is the corner weight.
rm is the motion ratio of the suspension at the springs / bags for the corner you're interested in.
a is the area of the cap of the bag.
pb is the approximate bag pressure at ride height.

Do this for all four bags and record the values.

Next, compute the following function to see whether your tank will have sufficient capacity. I'm assuming you're in the States, since you have a Camaro, so I added a correction factor which allows you to use Imperial units. If you're using SI, you can convert your units or I can provide a different function:



where:
hf is the interior height of the front bags in inches.
wf is the weight of the front of the car in lbs.
rf is the motion ratio of the front suspension.
hr is the interior height of the rear bags in inches.
wr is the weight of the rear of the car in lbs.
rr is the motion ratio of the rear suspension.
vt is the volume of the tank in gallons.
p0 is the turn-on pressure for your compressor in psi.
p1 is the approximate pressure in psi that will be in your tank after airing all the way up from zero.

So long as p1 is greater than any of the four pbs you calculated above, your tank should be sufficient in size if filled to the pressure vt to fully inflate the bags from zero. If you don't think full inflation from zero is a necessary requirement, you can plug in a guess for how high your bags will be at ride height for hf and hr and get a result from that. In either case, if your p1 is very close to your maximum pb, I would add at least another gallon of air capacity, if not more.

[Lombardi]

When you've got that data, the calculations are as follows:

Get your approximate bag pressure at ride height for all four bags with the following function:



where:
wc is the corner weight.
rm is the motion ratio of the suspension at the springs / bags for the corner you're interested in.
a is the area of the cap of the bag.
pb is the approximate bag pressure at ride height.

Do this for all four bags and record the values.

Next, compute the following function to see whether your tank will have sufficient capacity. I'm assuming you're in the States, since you have a Camaro, so I added a correction factor which allows you to use Imperial units. If you're using SI, you can convert your units or I can provide a different function:



where:
hf is the interior height of the front bags in inches.
wf is the weight of the front of the car in lbs.
rf is the motion ratio of the front suspension.
hr is the interior height of the rear bags in inches.
wr is the weight of the rear of the car in lbs.
rr is the motion ratio of the rear suspension.
vt is the volume of the tank in gallons.
p0 is the turn-on pressure for your compressor in psi.
p1 is the approximate pressure in psi that will be in your tank after airing all the way up from zero.

So long as p1 is greater than any of the four pbs you calculated above, your tank should be sufficient in size if filled to the pressure vt to fully inflate the bags from zero. If you don't think full inflation from zero is a necessary requirement, you can plug in a guess for how high your bags will be at ride height for hf and hr and get a result from that. In either case, if your p1 is very close to your maximum pb, I would add at least another gallon of air capacity, if not more.

Wow that gets pretty technical. pretty cool. I never was go at math I'll post what information I found and I'll try and figure it out myself but if you could take a look that'd be great as well.

so far I've found

2010 Camaro curb wreight - approx 3741 lbs
2010 camaro weight distribution 52% front / 48% rear
I don't know to much about suspension but I found the camaro has approx 1.1 motion ratio in the front and 1.5:1 in the rear from factory (this information may or may not be correct)
Front bags are air lift part #75575
http://bumpersuperstore.com/i-113431...pring-kit.html. (Can't find to much info on these)
Rear bags are air lift part #78601
http://www.airliftperformance.com/product/78601/

This is the tank I'd like to use
http://store.baggedlife.co/specialty...m-air-tank-18/

SPECS:
18" Long
6.625 Diameter
4-3/8" Ports
1-1/4" Ports
200 PSI Rated
Industry Labeled Size 3 Gallon
Actual volume 2.2 Gallons

[Oh Damn, it's Sam]

Great research! Half the people that ask questions on here immediately disappear or bitch and moan when they're told they need to get some specifications.

It looks like you have almost everything we'll need here. You might e-mail Air Lift and get the center hole diameter for those bags, as well as the cap size and the overall maximum diameter. They should be easily able to provide that data to you.

As for motion ratio, what you've got there looks like it might be right. Because of how your source stated it, we'll actually have to use the inverse of those numbers in the equations above, but that's no big deal.

[Lombardi]

Great research! Half the people that ask questions on here immediately disappear or bitch and moan when they're told they need to get some specifications.

It looks like you have almost everything we'll need here. You might e-mail Air Lift and get the center hole diameter for those bags, as well as the cap size and the overall maximum diameter. They should be easily able to provide that data to you.

As for motion ratio, what you've got there looks like it might be right. Because of how your source stated it, we'll actually have to use the inverse of those numbers in the equations above, but that's no big deal.

oh no if i ask a question I intend to find the answer. Really trying to finish the car for spring and have a lot to do so can't waste time.

I emailed air lift and this is what I got.
"The airbags in the front kit, part number 58523, have a lower end-cap hole diameter of 2.220" and max diameter of the airbag is right around 7". I'm not sure what you mean "cap size". The rear bags, part number 58537, lower end cap is a 2.05" diameter (internal thread diameter is 1.91") and max diameter is also around the 7" mark."

seems they didn't know what the cap size meant (not that I do ether) but hopefully this is enough info to figure it out. just let me know thanks for ALL your help!

EDIT - now that I look at it it seems he gave me specs for the wrong part number. let me check to make sure.

[Lombardi]

Ok I think those are the part numbers for the bags. the part numbers I supplied are the whole unit together so the data should be correct.

[Oh Damn, it's Sam]

What I'm calling the end cap (there may be a technical term for the piece that I don't know) is just the aluminum cap that forms the top and bottom of the bag. On a bellows bag, it's often a hair smaller than the overall diameter of the bag. We're interested here in how much the bag can lift at a given pressure, so we need to know how large the cap is, since the flexible sides don't contribute much to the ability of the bag to lift the car.

It looks like for the 58523, the numbers we're interested in are as follows:
End cap diameter: 6.0"
Through hole diameter: 2.220"

I'm not finding good specs on the 58537, but looking at the pictures of the whole part and going off the specs supplied by Air Lift, I think we can make some educated guesses that will serve our purposes:
End cap diameter: Let's guess at 6.0"
Through hole diameter: 2.05"

From those numbers, you should be able to calculate the end cap areas for both bags to plug into the first equation.

It doesn't sound like Air Lift is handing out blueprints on those bags, and I don't blame them, but could you get maximum extension and compression on those bags from them? We can subtract one from the other and get a good guess at what the internal height of the bags looks like.