Air to Turbo

[Pete Masterson]

While I worked at NASA Ames Research Center, I learned that "fluid dynamics" often applies very directly to air flow. So, observations about hydrodynamics very often directly applies. 

Air for combustion is best obtained from the coolest source. On my DD Series 60 (and I think the 8v92s) there is an "air charge cooler" that is used to cool the air after it passes through the turbocharger and before it goes into the combustion chamber. Cooling the air makes it denser. Compressing air makes it hotter. 

I've heard a fair amount of anecdotal reports of improved 3208 performance by routing air intake to the front of the engine compartment, away from the behind the radiator. (Other FC owners with experience on this point would be far more help.) With a naturally aspirated front engine, a proper shape of the air inlet can result in "ram air" that gives a slight power boost.  Ram air is much less of an issue with a turbo charger, but would have a minor positive impact. 

On the PT models, getting air from outside the engine compartment is ideal. I believe my coach has its combustion air inlet on the curb side above the large grate side access door. There is no scoop or other effort to increase air flow -- but my DD Series 60 shows no signs of lacking sufficient air.

I've seen some sort of scoop at the top rear on some coaches with the 8v92. The problem is that if it faces forward (for the ram air effect) it tends to pick up undesirable debris. I think the main effort is to ensure that the engine has good access to fresh air from outside the engine compartment. Since the 8v92 (and 6v92) are all turbocharged, the ram air effect isn't especially important. Sufficient cross section and control of air-movement restrictions for what ever reason are important for ideal combustion.

FWIW, I often wonder how the generator manages to work with its very restricted source of combustion air inside the sound compartment. (Indeed, my generator starts putting out tons of black smoke when the air cleaner is only a little dirty...)

Pete Masterson

'95 Blue Bird Wanderlodge WBDA 42

El Sobrante CA

"aeonix1@mac.com"

On Jun 13, 2008, at 7:15 AM, 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@yahoogroups.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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