What is the Heater blower CFM?

[Joe Bob]

Anyone know what is the engine area heater blower and footwell blower is rated CFM wise?

[Joe Bob]

Nobody knows?

[sailchef]

Don't know why your asking, but, A few years ago I took my old OEM blower to a guy who rebuilds electrical motors. Thats all he does. He had a catolouge there and by looking at the numbers on the old motor matched it up with another, exact same size, even looked the same, cost about $200.00 less.

[Targa Me]

The stock blower has an rpm of 5000. you can buy similar blowers from Grainger but they spin at 2400 rpm.

[Flat Six]

I'm guessing Joe Bob is considering some sort of alternative blower mechanisms like in-duct/in-line fans and wants to figure out whether the units he's looking at will move sufficient volumes of air. Am I close?

I think if you take some rough measurements of the size of the 'squirrel cage' in each blower (diameter X height) and use the 5K rpm estimate from Targa Me, it shouldn't be too hard to find references to comparable squirrel cage blowers that have CFM ratings provided.

Dale

[Flat Six]

Joe Bob, maybe this will help:

McMaster-Carr

[JJ 911SC]

According to my frozen toes, in a SC with no footwell blower... not much!

[Jonny042]

The total air moved by the 3 in my car is 0... so if you divide 0 by 3 you get... oh wait a second I'm getting an error.

Sorry, I haven't even started drinking.

[Joe Bob]

I have two marine bilge blowers sitting on my shelf......I was curious of the rated cfm of the blowers was near the cfm rating of the original single engine one or the foot well blowers in the Carreras.

[mkc1962]

Joe Bob,

Were you going to fab up some kind of reduction collar for using that 3" or is it 4" bilge blower? I assume your using these in place of the footwells that use, what is it a 2.5" duct.

I recently back dated my 87 by fabbing up my own left side ductwork that looks totally diff from any other Ive seen. Mine does not have to deal with the Distributor issue. My intent was to also use a bilge type blower. Mounted somewhere in the engine bay, and have it blow into my new duct at an angle forcing the air downward near the heat exchanger tie in/ toward the cabin. This way giving the slow engine fan air a boost if needed. In doing so remove the footwells as I wont be needing that extra air. Also to install a resistor bank for 3 speeds and have the old rotary switch between the seats be the control point for that bank. Probably use an old AC resistor bank I have, and have it mount in place of the old heater relay. My challenge at the moment is how to reduce the 3-4" of the blower down to about 1.5". Just wondering if you were considering a similar type reduction collar for your usage.

[Joe Bob]

They are 3 inch and I was going to use them in the engine compartment.

[mkc1962]

Gotcha...just assumed as you were saying you had 2 that you were maybe going to use them up front. I also thought of using one in the rear in place of the main one that failed. But after seeing a few with all the extra stuff out of the way decided to go the backdate approach. But, with added fwd air that the new bilgeblower will provide.

[Wil Ferch]

Even if you try to compare CFM's... the flow rating is measured against a known piping resistane rating....like fractions of inches of water column (WC). A 500 cfm fan at "0 inches" may blow 350 cfm at the first-increment of ___" WC......then 200 CFM at the next increment.
Meaning....you need to compare fan curves....not one number.

[burgundyben]

I'm just about to buy a 3 inch bilge blower to fit in the engine bay on my 3.6.

Seems that the 3 inch ones pull about 3 amps of current, so its gotta help right! The one I want says its 120 cfm, sounds like quite a lot of air to me!

I'll let you know if it helps.

[BK911]

Is it installed? Measure the air velocity and multiply by the area. Hot wire anemometers are pretty cheap. Somebody in HVAC or Test and Balance will have one. Or pay for shipping and I can send you one to borrow.

If it isnt installed you can still measure air velocity. But as Wil said, the volume will decrease as the pressure drop of the system increases. It will give you a general idea, but wont be that accurate.

Maybe you can see how long it takes to fill a 5 gallon bucket?

[DaddyGlenn]

Originally Posted by burgundyben

I'm just about to buy a 3 inch bilge blower to fit in the engine bay on my 3.6.

Seems that the 3 inch ones pull about 3 amps of current, so its gotta help right! The one I want says its 120 cfm, sounds like quite a lot of air to me!

I'll let you know if it helps.

Watch out for temp ratings. The one's McMaster-Carr has are only rated for 200 degrees.

[burgundyben]

Originally Posted by DaddyGlenn

Watch out for temp ratings. The one's McMaster-Carr has are only rated for 200 degrees.

I'm gonna fit mine in the hose from the shroud down to the HE's, its on a 3.6 in a 78 and the motor has lost the OEM blower.

[mkc1962]

DaddyGlenn

Point well made about the temp rating....and something I did think about when planning out my backdate approach. But, if you dont suck in the hot air the way the old one did, then its not much to worry about. My plan, I think is the same that burgundyben is referring to...that being the blower will intake only ambient engine bay air then assist, when desired in forcing more across the heat exchangers....Bilge blowers are designed for average enine bay heat.

As for the cfm question....the bilge blower I have pushes a fair amount of air based on feel...if I compare it to my old engine bay blower, its similar...as long as more air than just the alt fan provides makes it fwd, I dont really care what the cfm value is....as most will tell us, that have alredy done a heater backdate...just the alt fan alone does darn good unless you live in extreme north....the only reaon I am adding this fan is so I can get a more efficient defrost when I want it and not have to rely on those noisy footwell blowers.

[burgundyben]

Originally Posted by mkc1962

DaddyGlenn

Point well made about the temp rating....and something I did think about when planning out my backdate approach. But, if you dont suck in the hot air the way the old one did, then its not much to worry about. My plan, I think is the same that burgundyben is referring to...that being the blower will intake only ambient engine bay air then assist, when desired in forcing more across the heat exchangers....Bilge blowers are designed for average enine bay heat.

I think it'll work. Will know in a few days!

[DaddyGlenn]

Anybody measure the temp of the air coming out of the heat vents?