Air to Turbo

[David Brady]

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 temp 68degF, I found

this nifty pipe airflow calculator:



http://www.pipeflowcalculations.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

>

>

>

__________________________________________________________

> Connect with friends from any web browser - no download required.

Try the new Yahoo! Canada Messenger for the Web BETA at

http://ca.messenger.yahoo.com/webmessengerpromo.php

>

No virus found in this incoming message.

Checked by AVG. Version: 7.5.524 / Virus Database: 270.3.0/1500 - Release Date: 6/12/2008 4:58 PM