[C38] engine temp

[Tom T.]

Hi Les,

You claim you don't want to appear stupid and then you go on to show you
are fairly astute about diesel engines.

As you pointed out, the thermostat should regulate the engine temperature
for optimum performance.  The problem we have is that the original heat
exchangers on many of our engines were just too small and if the water
returning from the heat exchanger is still hotter than the operating
temperature of the engine, the engine is gonna overheat, clear and simple.

You cannot have a heat exchanger too large but you can have one too small. 
If you had a heat exchanger ten times larger than you needed, it would just
mean your thermostat would regulate the coolant flow slower so that the
operating temperature would still be at the thermostat temperature.  With
the reduced flow from a very large heat exchanger, the flow would be slowed
to a trickle but the engine would still operate at the correct temperature.

Another plus of an oversize heat exchanger is that it gives a margin of
safety in case you pick up some debris causing a reduction of cooling
efficiency.  The little 2" heat exchanger that came with the 5424 had
absolutely no reserve cooling capacity at full throttle, especially in
tropical waters.  Add debris restriction and you have a meltdown, even at
moderate speeds.

Tom Troncalli




> [Original Message]
> From: Les <hlhowell at pacbell.net>
> To: <tdtron at earthlink.net>; Catalina 38 Listserve
<listserve at catalina38.org>
> Date: 9/1/2009 8:43:19 PM
> Subject: Re: [C38] engine temp
>
> Hi, everyone,
>
> 	I don't want to appear stupid, but I am.  
>
> 	Diesel engines are basically heat engines.  Most are designed to run at
> some temperature range.  If they don't get to that range, they become
> very "dirty", with carbon and so forth, including poor combustion and
> greater nasty air products.  Does anyone have any information about what
> the "design" temp was for the original engines (I have an XP-25B in JACE
> now and it came with a larger heat exchanger, but that is no indication,
> as the engines internals will determine how much cooling is right.)  If
> the thermostat is working right, the engine should maintain the right
> temperature I think, but I don't know for sure.  The mechanical
> thermostats are in essence a two element spring that holds them closed,
> with a waxy cap that will solidify when the engine is cold to keep it
> shut until the engine warms up enough to run right.  These thermostats
> are really simple, but a vital piece of equipment for a diesel.
>
> Regards,
> Les H
> On Mon, 2009-08-31 at 08:22 -0400, Tom T. wrote:
> >  
> > Ditto,
> >  
> > This sounds like my own experience.  That little original 2" heat
> > exchanger has to go to the Davy Jones locker for good!
> >  
> > Tom Troncalli
> > Renata #95 
> > 
> >  
> >         ----- Original Message ----- 
> >         From: Steve Smolinske 
> >         To: Catalina 38 Listserve
> >         Sent: 8/31/2009 2:33:21 AM 
> >         Subject: [C38] engine temp
> >         
> >         
> >         fyi
> >          
> >         as a follow up to earlier discussions on engine cooling, I
> >         replaced the 2" x 16" heat exchanger with a 3 x17 and dropped
> >         30 degrees off of my normal operating temp.  went from 190 to
> >         160 under way. With the larger exchanger I was also able to
> >         step up to 5/8 from 1/2 hose from the raw water pump to the
> >         exchanger.  Im amazed at how much smoother, quieter and less
> >         labored the engine sounds now.
> >          
> >         Steve
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