Re: alfa-digest V8 #62 - 86 Spider overheating up hills: pusher A/C fan?

[AlfaNeely@domain.elided]

       Where is this really long steep hill you keep driving up?  If it is 
long enough and hot enough (90 degrees F) and you are running at full 
throttle all the way up, then your spider is going to over heat.  Maybe you 
should quit driving up that hill <grin>.
       I mentioned this earlier, but perhaps you missed it.  My 84 Spider 
SCCA Improved Touring race car runs a stock Bosch engine as required by the 
rules.  It has the stock radiator.  In any race when the temperature is over 
90, it will run at 212 degrees the whole race.  It has not hurt anything yet.
       In one race when the ambient temperature was 105 degrees, the temp 
went to about 240.  I backed off a bit and short shifted until the 
temperature came back down.
       Also when the temperature goes up to 212 and stays there for a while, 
the oil pressure starts to drop.  That is with Red Line racing 40 weight 
synthetic.  The oil is just getting thin.  And when the temperature returns 
to normal, the oil pressure goes back up and the engine will run at 180 
degrees again.  My race car has done this for numerous cycles with no 
evidence of damage to the engine.  But it can be disconcerting.
       So if your spider overheats only on a really long hill, do not worry 
about it.

       My stock fan and shroud were removed to free up some horsepower.  I 
have rigged the stock air conditioning fan to push through the radiator.  The 
air conditioner condenser has been removed.  The stock AC fan was remounted 
close to the stock radiator and the opening below the stock AC condenser was 
blocked off.  At speed, I am not sure that the fan is really necessary or 
helpful.  The fan does not really help that much during a race, but is nice 
for cooling down afterward.
       There is some thought that pusher fans block part of the air flow to 
the radiator and that puller fans are better in that respect.  There is a 
good article on radiators in the current Grass Roots Motor Sports magazine.  
There was also a good article in Hot Rod Magazine a month or two ago.  Either 
of these magazines may be available at your local library.
       The stock air conditioning fan runs from the little button shaped 
sensor on the fan shroud.  When air coming off the fan is hot enough, the 
electric fan turns on.  If you want to experiment, run a separate wire direct 
to the fan.  Use a toggle switch to activate it when you want it.


Ciao,
Russ Neely
Oklahoma City

In a message dated 09/19/2001 9:51:47 PM Central Daylight Time, 
owner-alfa-digest@domain.elided writes:



> Date: Wed, 19 Sep 2001 14:12:42 -0700
> From: Brad Karp <bkarp@domain.elided>
> Subject: 86 Spider overheating up hills: pusher A/C fan?
> 
> Many thanks to the several generous souls who responded to my earlier note, 
> inquiring about my 86 Spider Quad's overheating while going uphill.
> 
> Suggestions included:
> 
>     - thermostat
>         *** I should have mentioned that it was replaced when the
>             engine was rebuilt in the summer of 2000--sorry.  ***
>     - bypass restrictor in hose from heater (hmmm, still need to check this)
>     - mixing coolant/oil (head gasket?)
>         *** No problem here; no discernible mixing, and again, the
>             whole engine was rebuilt, with new cylinder head and new
>             head gasket, in summer of 2000. ***
>     - pusher fan in front of AC condenser
>         *** possible eureka, read on... ***
> 
> (Again, the radiator was refurbished and the water pump is new.)
> 
> The last suggestion, the pusher fan in front of the AC condenser, seems 
> promising.
> 
> This morning, I turned on the AC (I hardly ever use it here in the 
> beautiful Berkeley weather)--fan to max, cooling to max. The compressor 
> came on, and cool air came out of the interior vents. (I had the belt 
> replaced and system charged by Monza when they did the engine rebuild in 
> the summer of 2000.)
> 
> But the pusher fan in front of the AC condenser did not come on! So I 
> assume it also fails to come on when the temperature sensor on the radiator 
> fan cowling should trigger it (to help with cooling when conditions are 
> causing the engine to run hot).
> 
> Two questions for the list, now:
> 
>     1) Is it certain that the pusher fan should be on whenever the
>        compressor is on? (I think it should, but just making sure.)
> 
>     2) When I'm driving uphill for a few miles in hot (>90 F) conditions,
>        AC turned off, would not having the pusher fan helping airflow to
>        the radiator make a big enough difference to cause the car to
>        overheat?
> 
>        I presume that having the AC condenser in front of the radiator
>        makes the radiator less efficient, and the temperature sensor to
>        trigger the AC fan would not have been added by the factory if it
>        weren't really necessary, but I suspect people on the list may have
>        concrete experience with how much of a difference the pusher fan
>        makes for engine cooling when the AC is off.
> 
> Many thanks again,
> - -Brad, bkarp@domain.elided
> 86 Spider Quadrifoglio, daily driver

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