[C320-list] ENGINE SPACE VENTING

[John Frost]

WOW! Actual facts that we can use. Great research job Don

Thanks,
John

John C. Frost
President
Safety Engineering Services, Inc.
2627 Trailway Rd.
Huntsville, AL 35801
(256) 650-0335

-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf
Of Donald Lawson
Sent: Saturday, March 17, 2018 5:14 PM
To: C320-List at Catalina320.com
Subject: Re: [C320-list] ENGINE SPACE VENTING

Jeff & Graeme
Rather than have a debate, I thought I would give all the data I could
collect and let everyone make their own decision as to use/removal of the
blower Some of you will have to convert to english/metric where I did not.
Also, this is for a 3YM30 Yanmar only but I expect it applies somewhat to
all diesels.

This 66 cu in (1.115 l) engine needs air at about 50 cu ft/min at 3000 rpm..
Assumes a .9 volumetric efficiency for this engine (under 1000 hours).
Older diesels are above or near .8.

Per the Yanmar Installation Manual (not owners manual):  1) Maximum engine
room Temp shall be 140 deg F (60 C) and 2) Minimum Engine Room Ventilation
Fresh Air Exchange
    (Ventilator Capacity) shall be 194 cu ft/min (5.5 cu meters/min).

Per Yanmar Installation Manual horsepower decreases from 30 to 29, at rated
rpm,  when temp at the fuel pump increases from 25 C to 40 C. Expect lower
hp at 60C.

Rule and Shurflo ventilators have about 250 Cu ft/min capacity with a 4in
hose.  I think I have a 4in dryer hose crushed to 2 in.

ABYC Diesel Ventilation Standard H-32, from 1987, states:
H-32.4.
PURPOSE
These recommended practices and engineering standards establish requirements
for ventilation of boats using diesel fuel.
SCOPE
These recommended practices and engineering standards apply to boats using
diesel fuel only for electrical generation, mechanical power and propulsion.
NOTE:	Ventilation requirements for boats using gasoline as fuel are
contained in ABYC H-2, "Ventilation ofBoats Using Gasoline".
DEFINITION
Ventilation - The changing of air within a compartment by natural or
mechanical means. Ventilation may be effected by dilution of contaminated
air, by introduction of fresh air, or by local exhaust of contaminated air.
REQUIREMENTS -IN GENERAL
a Ventilation Principle - Ventilation cannot be relied upon to remove all
vapors that are pos- sible from the presence of liquid fuel resulting from
fuel system failures or fuel spillage. (See ABYC H-33, "Diesel Fuel
Systems") b Storage Batteries - Compartments containing storage batteries
shall be vented to provide for the escape of hydrogen in accordance with
ABYC E-lO, "Location and Installation of Storage Batteries".
c Diesel Fuel Vapors - Due to the characteristics of diesel fuel and the
closed nature of the diesel engine fuel system, neither mechanical nor
natural ventilation, as prescribed for gasoline powered vessels, is
necessary to remove diesel fuel vapors. (See ABYC H-2, "Ven- tilation of
Boats Using Gasoline") d Removal of Fixed Gaseolls Fire Extinguishing System
Discharge - Ventilation means shall be provided to remove the discharge from
ftxed gaseous ftre extinguishing systems.
e Combustion Air - Ventilating provisions and openings to the machinery
space provided for supplying combustion air shall accomodate the air
requirements required by the engine manufacturer(s) for each propulsion and
auxiliary engine in that space. These openings may also function as means of
providing natural ventilation.
f Additional Uses of Ventilation - Power or natural ventilation is not
required on a diesel boat, but may be used to control compartment
temperature. power ventilation may also be used in the machinery space for
odor control and personnel comfort while servicing equipment.

Note c and e above.   Could not find the current standard without paying
money, expect it to be unchanged?

Based on the above the blower is not there to cool the engine but does
exchange air for engine room cooling and combustion. 

Therefore I will:
Continue to run my blower during engine operation per Yanmar's requirement. 
Change the dryer hose to something more substantial to keep it from being
crushed when I work in the aft areas.
Install an electric head

Happy Boating
Don Lawson





On Mar 15, 2018, at 2:09 PM, Jeff Hare wrote:

> Don,
> 
> Per what Graeme said, that's how ours was configured as well from the
factory.  For a bilge blower to really serve its intended purpose, it would
have to suck air in and vent it outside, as it's supposed to remove residual
flammable "gasoline" fumes prior to starting the engine to prevent awesome
dockside entertainment.  
> 
> So, if you really run the blower when you run the engine, that probably
only serves to validate the point that the engine gets what it needs just
fine through many places like the front and aft engine cover cracks, all the
places where hoses and bilge drain holes exist in addition to the pair of 4"
holes.
> 
> So, generally no need to sweat this.  To my knowledge I've never heard 
> of a 320 having overheating or efficiency issues due to the way the it 
> was installed by the factory.  On the bonus side, without the bilge 
> blower hoses clogging up the transom vent holes, your fridge might run 
> a little cooler.  :)
> 
> There's really nothing stopping you from drilling another 3" or 4" vent
hole near the existing ones to increase air flow except that you'd be hard
pressed to show made any measurable difference.
> 
> Cheers!
> -Jeff
> 
> -----Original Message-----
> From: C320-list <c320-list-bounces at lists.catalina320.com> On Behalf Of 
> Graeme Clark
> Sent: Thursday, March 15, 2018 5:20 AM
> To: Catalina list <C320-List at Catalina320.com>
> Subject: Re: [C320-list] ENGINE SPACE VENTING
> 
> Don
> 
> I may be being stupid, but cant see how running the blower improves the
airflow *to* the engine? It sucj=ks air away from the engine and is pretty
inefficnet at that according to Jeff). The suction from the air intake on
the engine itself when the piston is drawing in air probaly exceeds the
suction from the blower by a factor of about 50 at a guess.
> 
> Only if your blower was reversed to pump air INTO the engine compartment
would any possible benefit be accrued, surely?
> 
> Just a thought
> 
> Graeme
> #366
> 
>> On 15 Mar 2018, at 04:26, Donald Lawson <dnclaws at aol.com> wrote:
>> 
>> IMO.
>> When I rebuilt/ replaced my engine(s) I learned a lot about the Amount of
air a Diesel needs to run.  It needs a lot of cold air to run efficiently. 
>> I run the blower while the engine is running, not to cool the engine, but
to ensure that I provide the engine with enough cool combustion air. 
>> I agree with Jeff that the blower is not used for cooling the engine 
>> although I don't quite agree about better paths of air for engine run.
>> My aft cabin mattress pretty much precludes that. HOWEVER If you 
>> removed the hoses there may be enough SQ area of opening to get rid of
them.  Will do the math and get back to ya'll, but I seem to remember a 3in
dia hole is enough for a 2GM20.  We have 2, so may not be an issue.  I will
rid myself of them in the future. I pretty much crushed them working on the
fridge anyway.
>> Don Lawson
>> #1104
>> On Mar 14, 2018, at 4:35 PM, Jeff Hare wrote:
>> 
>>> Not to be critical of anyone's answers, because it's great to bounce
these thoughts around to help refine your logic, but seriously don't
over-think this.  
>>> 
>>> The engine doesn't need cool ambient air to keep it cool, that's what
the raw water heat exchanger is all about. Otherwise they would not put it
in an insulated box with a couple lengths of dryer hose.  It also doesn't
need any duct work to feed it air to run because there are SO many better
paths for hull-cooled bilge air to get into the engine that it's simply a
non-issue.
>>> 
>>> If you really believe that the blower reduces the heat in the aft cabin
with the stock hoses, awesome, but it really doesn't.  No way you're moving
that much heat out through those crinkled half crushed hoses with our anemic
blower. LOL!  You'd have to run the blower till the engine block cools down
quite a bit to make any real difference or it'll just reheat the air again.
By then someone sharing the mooring field with you would have launched a
torpedo at your boat because of all the racket that thing produces.
>>> 
>>> If you really want to help remove any excess aft cabin heat, I'd suggest
that you open the aft cabin access door at the foot of the bed and aft
cockpit locker above the fridge compressor and let convection take over.  If
you really wanted to use hoses for some reason, you'd need 4" smooth wall
hoses that have fewer bends and a more powerful blower to actually get any
reasonable airflow.
>>> 
>>> I'm pretty certain that the blower and the hoses were only installed to
satisfy outdated requirements for a bilge blower (which diesels are exempt
from now in the US anyway).
>>> 
>>> Cheers!
>>> #809   stay'n hoseless  :)
>>> -Jeff Hare
>>> 
>>> -----Original Message-----
>>> From: C320-list <c320-list-bounces at lists.catalina320.com> On Behalf 
>>> Of John Meyers
>>> Sent: Monday, March 12, 2018 3:23 PM
>>> To: C320-List at catalina320.com
>>> Subject: Re: [C320-list] ENGINE SPACE VENTING
>>> 
>>> John
>>> 
>>> If thing for convection to work you may need one of the openings to be
connected to a hose with one end lower than the one without a hose. The one
with the hose will let cold/fresh air in when the hot air rises to the vent
without the hose.
>>> 
>>> John Meyers (The other John M)
>>> 
>>> On Mon, Mar 12, 2018 at 10:08 AM, John morrison 
>>> <sail-ability at sympatico.ca>
>>> wrote:
>>> 
>>>> I attended a surveying seminar on the weekend, and for those who 
>>>> may not know ( I didn't) diesel engine spaces do not require forced 
>>>> ventilation in order to pass a survey. You may want to have it for 
>>>> other reasons as has been mentioned in this forum. I intend to 
>>>> remove the vent hoses from the cowls and let the space vent by
convection.
>>>> The cowls are high up in the stern so warm air should exit pretty 
>>>> well, we'll see  how that works. When the hoses are attached the 
>>>> cowl holes are blocked and hot air from the engine, fridge 
>>>> compressor, cannot escape; unless of course the blower is r