Wondering if anyone has done a few on the same bench

 

Look for a thread KMook did on LT1 or Advanced tech about this he has all the flow numbers.

Bret

 

It was LT1, but those are flow #s that companies just advertise. I am not sure if LTOne4Fun was looking for that...

 

I have 612 cfm for the 48mm and 644 cfm for the 52mm.

Best Regards,

Daren

 

Wish I had a flow bench to test a few. The numbers I always used were...

48mm = 512cfm
52mm = 658cfm
54mm = 742cfm
58mm = 936cfm
Monoblade is like 1200.


I got these numbers from EA3 a long time ago. It had a utility that allowed you to punch in the number of TB blades, and their diameter and it kicked out a flow rating at 1.5" HG 20.4" H2O. So I assume that this is a pretty rough (using some constants for Reynolds numbers etc.) calculation. But it should be pretty close to reality as really it should just be a mathematical calculation and roughing in a couple constants I wouldn't think would make a large error rate (guessing maybe 5%ish).

Would be nice if someone actually had real flow bench numbers though.

 

I did some research on this topic awhile back and found this web site at the univeristy of northern ohio that flow benched some TB's.. here is the link..

TB flow numbers from flow bench - click here

Also, here is a link to a thread I started on this topic awhile back on corvetteforum.com

vette forum link

 

Wow if those numbers from that university are correct then the theory about the maf not being a restriction are out the window I would say.

 

I can get in the area of 750-800 depending on what I do to my 52mm throttle bodies

-Shannon

 

Thats good to know Nomad, I'm using one of yours

I really like the work you did

 

Just gotta make sure both flows are taken at the same " h2o. The University numbers are taken at 28" h2o, and if approx converted to 20.4" (which iirc is standard for rating carb and TB flow measurements) the numbers are similar to what I posted above.

University stock 48mm @ 783 28" h2o is ~566 20.4" h2o
University 52mm with airfoild @ 899 28" h2o is ~650 20.4 h2o

I don't think I've ever seen a MAF flow tested, and if you ever do see one make sure they were flowed at the same pressure or try to work up a conversion.

BTW, anyone know if there is a formula to get a close approximation conversion between flow rates? I found a site that said to go from 28" h2o to 10" h2o you mult by .598. From that I extrapolated that to go from 28"h2o to 20.4"h2o would require a multiplication of .723, assuming linearity though which may be a very false assumption.

Anyway, always fun to chat with you guys.

 

At what pressure Shannon? Think pressure is correct, 20.4"h2o, 28" h2o? Something else?

{Edited for content, very tired lol}

 

Thats what the chart on the back of the AFR catalog has as well.

 

From what I know carbs and throttle bodies are flow rated at a pressure drop of 1.5" Hg, you need to convert this to 1" Hg. So use this formula-

sq root (new pressure drop / old pressure drop) x flow at original pressure drop

So a 58mm TB that is rated at 1050cfm would flow 857cfm actually.
sq root (1.0/1.5) x 1050 = 857cfm

BTW Wile where have you been?

 

Although carburetors CFM is rated at 20.4" of water it should be noted that that rating is a wet flow number.. meaning air AND fuel through the venturi.. Rating a Throttle body the same would seem to me to produce a conservative CFM rating since a TB is a dry flow apparatus.

according to my datalog files my car regularly sees 28" of vacuum at WOT (28" is around 100 kpa which is atmospheric pressure at sea level)

besides I would have a tough time trying to explain how chevy got 502hp out of the 502cid RamJEt crate motor using the stock LT1/L98 48mm TB...

 

BTW: Here is the link to the check 502 Ram Jet engine..

http://www.sallee-chevrolet.com/ChevyBigBlockV8s/Ram_Jet_502.html