what size air comp. do i need to paint a car

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what size air comp. do i need to paint a car

Postby carcrz » Thu Mar 11, 2010 1:23 am

hello everybody.... i'm going to paint a car in a couple of weeks but i need to know what size air comp. i need to buy i will be using the iwata LPH400LVX, can somebody post what HP and cfm i need to get so it can keep up with the spray gun thank you
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Re: what size air comp. do i need to paint a car

Postby Hub » Thu Mar 11, 2010 3:10 pm

carcrz wrote:hello everybody.... i'm going to paint a car in a couple of weeks but i need to know what size air comp. i need to buy i will be using the iwata LPH400LVX, can somebody post what HP and cfm i need to get so it can keep up with the spray gun thank you


Good Morning Carcrz,
Welcome to our forum.
The LPH400LVX requires a constant air supply of 10 ACFM - but It would be only prudent that you give yourself a cushion of at least 5 CFM for line loss and other air tools you may want to use.
Good Luck,
"HUB" :)
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Postby carcrz » Thu Mar 11, 2010 4:02 pm

Goodmorning hub thank you for the quick responce the comp.that I'm looking at put out 6.5cfm at 40psi and 5.5cfm at 135psi do you think that would do me good if not can you point me inthe right direction I got limited space the biggest I can go with is around 30 or 40 gal. Thank you for your advise you are the man...
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HUB COMMENT

Postby Hub » Thu Mar 11, 2010 8:03 pm

carcrz wrote:Goodmorning hub thank you for the quick responce the comp.that I'm looking at put out 6.5cfm at 40psi and 5.5cfm at 135psi do you think that would do me good if not can you point me inthe right direction I got limited space the biggest I can go with is around 30 or 40 gal. Thank you for your advise you are the man...


No, that won't do the job. With out an adequate compressed air supply the gun won't function well - hence after all that work getting ready - bad or at best a poor paint job.
Try Home Depot or lowes ask for an upright their foot print is very small.
Refer to my first post for the CFM requirement.
Cheers,
"HUB" :)
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Postby jcclark » Fri Mar 12, 2010 8:45 pm

carcrz wrote:Goodmorning hub thank you for the quick responce the comp.that I'm looking at put out 6.5cfm at 40psi and 5.5cfm at 135psi do you think that would do me good if not can you point me inthe right direction I got limited space the biggest I can go with is around 30 or 40 gal. Thank you for your advise you are the man...


Pay no attention to that 40 psi rating-your compressor should never
get low enough that it's pumping against a tank that is only 40 psi.
It IS pumping against a tank that is above 90 PSI so the 5.5 is
what the compressor puts out-at best. 8)
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HUB COMMENT

Postby Hub » Mon Mar 15, 2010 6:22 am

jcclark wrote:
carcrz wrote:Goodmorning hub thank you for the quick responce the comp.that I'm looking at put out 6.5cfm at 40psi and 5.5cfm at 135psi do you think that would do me good if not can you point me inthe right direction I got limited space the biggest I can go with is around 30 or 40 gal. Thank you for your advise you are the man...


Pay no attention to that 40 psi rating-your compressor should never
get low enough that it's pumping against a tank that is only 40 psi.
It IS pumping against a tank that is above 90 PSI so the 5.5 is
what the compressor puts out-at best. 8)
.

Hello JC,
Take another look at the ratings - they are correct, that 40 PSI is down stream pressure being used - not receiver pressure. Remember we're talking compressed air.
Cheers,
"HUB" :)
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HUB COMMENT

Postby Hub » Mon Mar 15, 2010 6:23 am

jcclark wrote:
carcrz wrote:Goodmorning hub thank you for the quick responce the comp.that I'm looking at put out 6.5cfm at 40psi and 5.5cfm at 135psi do you think that would do me good if not can you point me inthe right direction I got limited space the biggest I can go with is around 30 or 40 gal. Thank you for your advise you are the man...


Pay no attention to that 40 psi rating-your compressor should never
get low enough that it's pumping against a tank that is only 40 psi.
It IS pumping against a tank that is above 90 PSI so the 5.5 is
what the compressor puts out-at best. 8)
.

Hello JC,
Take another look at the ratings - they are correct, that 40 PSI is down stream pressure being used - not receiver pressure. Remember we're talking compressed air.
Cheers,
"HUB" :)
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Postby jcclark » Mon Mar 15, 2010 1:10 pm

????????????

A compressors rating is what the pump puts out against a 40 psi
backpressure. And again against a 90 psi back pressure.
The more pressure it's pumping against-the lower the cfm output.
That pump has no idea what is being used or how much.
Even if you're spraying with 20 PSI,
It is always pumping against the pressure in the tank, period!
which is generally above 90 psi. (not the 20 psi of the user)
That's what the pump is pumping against no matter what is being used
at the downstream end,
So the 90 psi rating is the cfm the pump is actually delivering
when running normally, and even less if your pump stops at a
higher psi, which most do.
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HUB COMMENT

Postby Hub » Mon Mar 15, 2010 5:23 pm

Barometric pressure at sea level is 14.7 PSI and when put under pressure at 100 PSI it is compressed into a volume of .13 CFM thus the volume of air in 1 cubic-foot container would increase to 7.69 cubic feet - thus when released at a lower PSI there is more CFM to work with.

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Postby jcclark » Mon Mar 15, 2010 7:02 pm

That's true, but still,
the compressor never pumps out the higher cfm rating listed at 40 psi.
(unless the tank is empty)
The output of the compressor is the lower cfm number at the 90 psi rating.
The pump is not going to put out more or less cfm because of
which tool you're useing.
The pump is always pumping against the 90 psi (or higher)
tank pressure.
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Postby jcclark » Mon Mar 15, 2010 7:02 pm

dbl post
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HUB COMMENT

Postby Hub » Fri Mar 19, 2010 5:57 am

You made my case - but you didn't mention relative humidity, ambient, intake or discharge temperature or the resulting CAH :roll:
Cheers,
"HUB" :)
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Postby jcclark » Fri Mar 19, 2010 11:56 am

We're talking apples vs oranges hub (LOL)
You're talking about the air you can get out of a compressor,
I'm talking about the air the PUMP can FILL a compressor.

I agree with everything you've said, all good points and true! :D

GO back and read my original statement,
All I've said is the 40 psi "higher" CFM RATING of a compressor is
NOT ever produced by its pump, the 90 psi lower rating is the CFM you
compare by since that's the pressure the pump is pumping against.
that's the refill cfm rate-the lower one.
(refilling of the tank CFM)
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HUB COMMENT

Postby Hub » Fri Mar 19, 2010 4:24 pm

JC,
You are correct, I wonder if our discussion answered any question for any viewer along the way - hope so.
Cheers,
"HUB" :)
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Postby jcclark » Fri Mar 19, 2010 6:12 pm

Thanks Hub, for being such a gentleman.
Sometimes it's hard to discuss something on a forum
when you can't hear how it was said.
It's easy to take things the wrong way and
I really don't want to sound like a a-hole.
Staying professional, as you do, really helps.
Keeps everything good! :) :) :) :)
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