Air to Turbo - Printable Version

Wow,this will take a while to absorb LOL.

Thanks David

Bill 84 FC 35 SB "$quanderlodge"
Terrace, B.C. Canada

----- Original Message ----
From: David Brady
To: WanderlodgeForum@yahoogroups.com
Sent: Monday, June 23, 2008 2:26:55 PM
Subject: Re: [WanderlodgeForum] Re: Air to Turbo

Bill, I'm by no means an expert in this area, like that ever stopped me before , so I yanked these little gems off the web. Based on the Ideal Gas Equation (PV=nRT) and this nifty engine volumetric flow rate equation, we have the following mass air flow calculation for your engine running at full tilt:

volume of air (cu ft/min) = engine rpm x engine cid (1728 x 2)

Mass air flow(lbs/min) = P(psia) x V(cu.ft./min) x 29(10.73 x T(deg R))

For your motor at the exit of the turbo compressor: CID = 636 cu.in. (engine displacement) RPM = 2200 (engine rpm at max power) P = 14.7 + 20 (max turbo boost pressure) = 34.7 psia V = 405 cu ft/min, (engine volume rate of air) T = 250 degF + 460 = 710 deg R (air temp at turbo output) mass air flow(lbs/min) = 53.5 lb/min

Based on squeezing 53.5 lb/min of air thru your intake plenum, which I'm modeling as a pipe with bends, at standard air pressure 14.7psi and temp68degF, I found this nifty pipe airflow calculator: http://www.pipeflow calculations. com/airflow/ index.htm Plugging in the mass air flow, pipe diameter and length, 14.7psi ambient air pressure, and 70 degF, I get the following pressure drops across the pipe:

Diameter Length Pressure Drop across pipe 3" 72" 0.67 psi 4" 72" 0.19 psi 5" 72" 0.075 psi 6" 72" 0.035 psi 7" 72" 0.019 psi

Based on this I would say that your 5" air filter intake is adequate and that your 40 sq.in. ram air intake is also adequate, as long as the plenum length from ram intake to turbo is no longer than 72", I'd restore the system to original. If your intake is longer than 72" we'll have to redo the calculation. Most likely the air filter element is the largest restrictor in the system.

As far as turbulence in the 5" dia air intake plenum, well the air velocity there is 87 ft/s, so it does appear that turbulence is a concern, but the above referenced caculator takes that into account via it's roughness index (Kr) which I set to .00177 inch for steel pipe. There's another constant in the above calculator, (Ksi) the minor loss coefficient. This I set to one which accounts for bends in your intake plenum: 3 long radius flanged 45's and 2 long radius flanged 90 deg's. So you can see, modeling the pipe is a real pain. The pressure drops across the pipe are quite sensitive to this parameter. Hope this helps

Please someone, crap detect this. :-)

David Brady '02 LXi, NC

Gregory OConnor wrote:

Bill, like in our topic of door wind noise, turbulance of air causes
restriction of flow.Wind noise is a visual result of air
turbulance?? ? I removed a big acordian scoop from a tractor that
collected cleaner air from out of the hot engine compartment and
reduced the black smoke immediatly?? ??? I learned that there was no
restriction in the pipe but my thinking is the air restricted its
self. you may notice corrigated 2 foot drain pipes stay cleaner than
smooth and bigger concrete pipe. the turbulant flow of water
restricts flow and uses the energy to work up otherwise settling
silt. I am sure air flow has major diffs than hydrodynamics? ?? But
turbulance causes heat and I wonder if 'just heated air' has
density lost??

I am not sure 'hot air 'is that much less dence than cooler air. I
understood the advantage to be 'air just cooled'.???? ?

Now DavidB and PeteM can add some math to
convince you to look for
another project... Dig a pit and wait for the WhatsHisName' s kids.
it's more fun than knocking beer cans off'a fence.

GregoryO'Connor
94ptRomolandCa

--- In "WanderlodgeForum%40yahoogroups.com", Wilhelmus Schreurs
wrote:
>
>
> When I purchased my coach, I noticed that the top of the air
cleaner (cage) and the ducting to the intake was removed. I believe
this was done as it is commonly believed to be known, that it does
not appear to get enough air from the outside.
> Some quick calculations show that the intake is 27in by 1 1/2
inches = 40 sq in.
> Intake to filter is 5 in round or equivalent to 20 square inches,
this should be adequate air flow, or maybe the intake to the filter
should be
increased say to 7 inches. (38 square inches)
> Also does the turbo not suck the air in as well??
> What I am planning to do is to restore everything, as right now it
is getting the very hot air from around the engine, and I believe it
should be getting the colder air from outside?
> Any advice, pros and cons would be appreciated.
> Thanks in advance.
>
> Bill 84 FC 35 SB "$quanderlodge"
> Terrace, B.C. Canada
>
>
>
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