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Various MG Winter Issues

To: MGs <>
Subject: Various MG Winter Issues
From: Michael Chaffee <>
Date: Wed, 31 Jan 1996 19:09:49 -0600
On Wed, 31 Jan 1996 wrote:

> My problem with heating seems to be 2-fold:
> 1. Car takes > 10 miles to heat up (even though I have aluminium
>    foil blanking off 100% of the oil cooler and 50% of the radiator.
> 2. Cold air leaks in around the fresh air vent behind the dash (the plate
>    than can be opened and closed by a handle attached to it).

1.  At least one person has posted suggesting replacement of the
thermostat.  I would test the thermo before replacing it, or perhaps not
bother.  Fact is, if the car is warming up when it's cold outside with the
heater on, the thermo is probably OK.  Second, ten or so miles isn't that
bad.  It takes longer than that for my Midget (180F thermo) or my BMW
(190F thermo) to warm up if it's below freezing out, and I know both
thermo's are good.  In theory, blanking off the radiator should not affect
warm-up, since there is theoretically no water flowing through the
radiator until the thermo opens.  The first (and only) winter that the 
Midget served as my daily driver (did great starting, needed better 
tires), I tried blanking off most of the radiator.  Result: Water temp 
ran 160F without the blanking (this was before I put in a 180F 
thermo), about 180-200F with the blanking.  With the water a little 
hotter, the oil warmed up more quickly and the heater worked a little 
better.  So blanking off the radiator does have its benefits, but it 
shouldn't affect how long the car takes to reach thermostat temperature.  
Also, note that if it is cold enough outside, and you have the heater on, 
the engine may not be able to sustain thermostat temperature.  My BMW 
runs right on the thermo absolutely all the time, except when it's really 
cold, the heater is on, and I'm going faster than 55 and slower than 85.  
In that range, the heater (not bypassed by the thermostat) sucks more 
heat out of the coolant than the engine generates, and the temp. sinks to 
maybe 150F or so.

        Blanking off the oil cooler (if you don't already have an oil
thermostat) will make a big difference in the oil temp, and probably some
difference in the water temp as well.  You do want to blank off the oil
cooler if it's cold anyway, because running with too-cold oil is a Bad


On the same day, Fellow Fiend Will Zehring asked a number of questions 
about starting Old Whitesides in the cold.:

>Okay, to the question(s).  I hope those of you who majored in EE are paying
>particular attention.  

The fact that I am majoring in English Lit/Bio-PreMed should serve as a 

> Why
>can't I install two 12 volt batteries in parallel?  I would still have 12V
>but I would double my amp supply (yes/no?).  

I'm not going to start on physics or any of that smarty-pants stuff, but
simply put, yes, you would have more juice, provided that the two 12V
batteries are healthy, good-sized units.  If we're talking about two
12-volters that are small, to take the place of two small 6-volters, you
might get the same or better results from the 6V's.  I don't know how much
room there is back there on a B.  Many Diesel cars and trucks use two
full-size (and in some cases bigger than full-size) 12V batteries in

>Would my conventional charging
>system handle it or would it freak at the extra amperage?  

I'm pretty sure that, provided we're talking about two healthy, newish 
12V batteries, they wouldn't pull excessive current.  

>Would my starter
>motor and/or regulator explode?  Has anyone done this successfully?  

The current in the starting circuit is normally limited by the starter 
motor; having more "juice" on tap shouldn't change the max. current, 
provided that the voltage stays the same.

>do I
>just want a new/reblt. dyanmo and a better set of batteries?

Let's look at that part of the system.  Suppose that your hypothetical 
BGT is unbelievably difficult to start and cranking times are usually in 
the range of 60 seconds.  Assume that the starter draws around 50 amps or 
so.  Now, we can find out how much juice a start takes:

(1 min)(50 A)(12 V) = 600 watt-minutes, or 10 watt-hours.

Now, suppose your dynamo puts out a max current of 30 A.  I'm just 
pulling this number out of the air, but I'd be surprised if it was much 
lower.  Suppose that the ignition and fool pump (if so equipped) draw 10 
A (I think this is on the high side, but hey, we're in theory-land.).  
So, then, we have:

(600 W-min)/[(20 A)(12 V)] = 2.5 minutes fast-idling in the driveway 
before the battery(ies) is(are) recharged.

Put another way, if the dynamo is sufficient to maintain charge in the
summer, why would it not be enough in the winter?  The battery suffers
more drain on cold starts, but otherwise it's the same situation.  Unless
I'm not understanding things, the battery will charge until it is full. 
Provided that it is a good battery, and provided that the electrical system 
isn't pulling more current than the dynamo can supply, the battery will 


        On another note, one of our BSGC's (Big Sinister German Cars) 
just blew out the oil filter when it started up.  I think this was due to 
the fact that it was running 20W50 oil and it was about 3F out at the 
time.  The moral:  Run the right oil for the season!

"Central Illinois Experiences Record Cold: Hell Freezes Over"
Keep warm,

Michael Chaffee

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