[Diy_efi] RE: Timing and dyno pulls

[efi student]

What about the effect of a higher system pressure on localized boiling =
and
surface wetting for thermal transfer?  Isn't a higher cap pressure going =
to
reduce the size of the steam bubbles around the exhaust ports and =
improve
thermal transfer?  That seems to be the concensus from a number of sites =
I
have seen discussing cooling system performance and from empirical
experience.

lance

-----Original Message-----
From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org] On =
Behalf
Of Adam Wade
Sent: Monday, December 23, 2002 11:25 PM
To: diy_efi at diy-efi.org
Subject: Re: [Diy_efi] RE: Timing and dyno pulls


--- Grant Beaty <gbeaty at ufl.edu> wrote:

> I was wondering if cooling system pressure effected
> the heat exchanged with all other things being
> equal,

With a non-compressible (like coolant, for all
practical purposes) you can do two things by
increasing the pressure; you can increase the flow
rate through the system, which may or may not make the
system able to move more heat (depends on how fast the
coolant can pick up and shed heat), and you can raise
the boiling point of the coolant (which is probably
the most important bit).

> 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.

Well, if you're not blowing off the valve in a
lower-pressure cap, putting on a higher-pressure cap
won't change a thing.  It would only make a difference
once coolant pressures got ABOVE the blow-off point
for the lesser cap.

> 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.

I was meaning more something along these lines; GSX-R
motors seem to make best power at right about 200 F
coolant temp.  At 180 they are down a bit, and at 220
they are down a LOT.  They seem to do best at 200 F,
when tuned for best power at a given coolant temp.=20
That sort of thing.

> On the street, I don't see any more knock with the
> stock (180F) thermostat than a colder one.

Would a slightly hotter one make better power?  LEss
pinging?

> Of course this is veeery far from scientific
> testing :)

Gotta start somewhere.  ;)

=3D=3D=3D=3D=3D
| Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
|   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=3D/   |
| "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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