[Diy_efi] RE: Timing and dyno pulls

[M. Claywell]

On 24 Dec 2002, Grant Beaty wrote:
> I was wondering if cooling system pressure effected the heat exchanged
with
> all other things being equal, including radiator inlet temps. I noticed
no
> higher coolant temps (the probe is where the coolant exits the block)
with a
> 19-21 psi cap compared to stock 16 psi.

What was the system pressure getting up to? If the system pressure was NOT
blowing off the 16psi cap, then putting a higher pressure cap is not going
to change the pressure that the system gets to, provided the same
temperature. Getting to a certain temperature is the mosst part of what
generates the pressure. 

With that said, I would run the highest pressure cap that you feel you can
safely run on your system. For motorcyles I usually buy something over
25psi. Most decent systems on cars and bikes that I have seen tested have
never seem to have any problems going to 35psi or more, and would hold
pressure. 

Mark 




> > Particular engines seem to have a coolant temperature
> > that they "like" best for best power.  I know a little
> > of the science behind it, but not enough to really
> > talk about it seriously.  I'd definitely be interested
> > in knowing more about that.
> 
> On my car, doing dyno runs with cold coolant didn't change the HP output
at
> all - although I didn't exactly try and optimize timing and fuel maps for
> the cold temps. On the street, I don't see any more knock with the stock
> (180F) thermostat than a colder one. Of course this is veeery far from
> scientific testing :)
> 
> Grant Beaty
> '97 Supra T
> 
> ----- Original Message -----
> From: "Adam Wade" <espresso_doppio at yahoo.com>
> To: <diy_efi at diy-efi.org>
> Sent: Monday, December 23, 2002 4:58 PM
> Subject: Re: [Diy_efi] RE: Timing and dyno pulls
> 
> 
> > --- Grant Beaty <gbeaty at ufl.edu> wrote:
> >
> > > Ah, so its all from the better transfer from engine
> > > -> coolant.
> >
> > Yeah, as you raise the coolant temp, the pressure
> > rises (of course), but as you have more heat going
> > INTO the coolant, you won't be able to get it out as
> > easily as you get it in (because air is a lot harder
> > to heat than metal or coolant).  Theoretically, you
> > want the coolant as hot as possible, since it'll shed
> > heat more quickly if it is hotter, but then you run
> > into design issues with the cooling system's pressure,
> > what to make the hoses from, etc.
> >
> > > I already knew that heat transfer is proportional to
> > > delta T ;) I was talking about pressure alone.
> >
> > I'm not sure what you mean by that...  Again, the
> > hotter the coolant temp, the more heat will be shed to
> > air of a given temp, but to get coolant temps higher
> > without reducing radiator area, you're going to
> > itroduce heat more quickly than you can shed it (from
> > additional coolant temp), meaning there's actually a
> > disadvantge in the real world in most cases.
> >
> > Particular engines seem to have a coolant temperature
> > that they "like" best for best power.  I know a little
> > of the science behind it, but not enough to really
> > talk about it seriously.  I'd definitely be interested
> > in knowing more about that.
> >
> >
> > =====
> > | Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
> > |   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=/   |
> > | "It was like an emergency ward after a great catastrophe; it  |
> > |   didn't matter what race or class the victims belonged to.   |
> > |  They were all given the same miracle drug, which was coffee. |
> > |   The catastrophe in this case, of course, was that the sun   |
> > |     had come up again."                    -Kurt Vonnegut     |
> >
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> 
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