Re: P&H Injector Interface

["nacelp" <nacelp@bright.net>]

> Bruce,
> being the tester that you are, have you measured the underhood

Yep,
funny you should ask.  Was just doing some the other day.
This gets into a whole bucket of worms, and varies tremendously,  I mean a
bunch.
Dr Jacobs mentions thermal mapping an engine compartment for installing
ignition boxes, and that got me going on this about 7 years ago.  I'm going
to splain what I've seen, and heard from a few guys, that I trust, and what
I do.
    Most of the oem engine temp lights come on in the range of 250dF.  So
running at 230dF is to be expected in stop and go traffic with the A/C on.
The radiator fan does a good job of assuring every noke and cranny gets to
the same temp on a hot day.   Then oil temps get even hotter, 350dF is not
the least bit uncommon, and I've heard of as much as 400dF and these are oem
applications, where the engine are lightly stressed.  So with the oil pan
radiating heat from the hot oil, and fan ensuring that things are at least
at 230dF, 300dF in a hot soak is not the least bit of a surprise.   I'm
almost amazed there ain't more paint bubbles on hoods.   I personally do
ever thing I can to get under hood temps down.
   Also, after some extensive testing the hottest temp., I've ever gotten
for a gm ecm is 110dF.   That was running numerous non oem TBI injectors
(static) onna ecm that had some huge drivers in it.   The hottest oberved
temp for a oem gmecm had been about 98dF.  All temps were in my kitchen with
an abient temp of about 75dF.  So this would indicate to me that it should
be mounted where the temp rarely exceeds 95dF.   I want the ecm as cool as
possible so that it's giving off heat rather then absorbing heat from it's
surroundings...   I even try to ventilate it's mountings when possible.  I
can see a CPU fan being used in some applications (race car even with
interior mounted ecm).
   Back to engine compartments.   Some of the things I do are, remove the
seals from around the hood closure.  If at all possible run a cowl induction
hood, not for the "ram" air, but to allow the engine compartment heat to
chimney out on a hot soak.  If I run a Cowl hood then, then I try to run a
3d angle of attack (as measured on the rocker panel), with a front lip
spoiler, to help generate a low pressure area under the car to help
circulate air thru the egnine compartment.  While folks like to credit these
hoods with cold air for the engine, there are lots of factors.  Ie headers
with all there surface area generate heat, the higher the ambient air temp
under the hood the higher all the operating temps go ie coolant oil power
steering brake fluid.  Yes were getting really anal when we worry about
power streering fluid temps., but run it at 240dF and see how long the front
seals last and how noisythey get.  Fords used to use a little single loop
cooler that can drop the temps 30dF.   If it's realy bad then, I'll run the
water to the heater to circulate, full time (although with a restrictor), to
help take a slight load off of the radiator (on newer stuff with the 3% air
leakage, can be challenging to turn the air alll the way off).
   Of course this is all race car stuff.  I'd never recommend any of this
for street use.  ie blocking off and sealing the heater box meaning CO2 can
accumulate, yada yada.  You need to think out all the related details when
doing this sorta thing.

and 'heat
> soak' temps on a car. numbers have been bandied about..around 250degF. I
am
> wondering about electronics survivability issues here, specifically..is
this
> why the actual board in a '727 is upside down in the box?

I'm not at the $100K engineering level the boyz at the gm design area get,
so I don't have a clue.  Might be the ol saying about a "A camel is a horse
designed by committee" <g>......
Grumpy
   Ugh, there was another incident at CSH, HQ..  Details pending <g>......
> Swayze
> mswayze@truswood.com
> kswayze@bellsouth.net
> .........
>
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