[Diy_efi] RE: Timing and dyno pulls

[Grant Beaty]

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.

> 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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