This seems to be something for which no one can give a definitive answer. I=
=20
have wanted to know the real answer for quite some time. Here is what I am=
=20
doing to resolve the question.
I have (for the past year) had my timing set strobascopically (sp?) at 14=20
degrees advance - which should be the ideal setting. In the environment=20
that I live in, my engine coolant temperature has frequently hit 212=B0F=20
(100=B0C). Occasionally the temp has gone above, but not very often - my=
'67=20
MGB, that I use for daily summer transportation has a temperature marked=20
gauge - not one that shows 'normal.'
This evening I retarded the timing from 14 degrees to 12 degrees of advance.=
=20
I will drive the car to work and back (30 miles each way) at 80mph (our=20
speed limit is 75) for the next two days. The following day, I will set the=
=20
timing to 16 degrees of advance. I will drive to work and back at 80, and=
=20
see if there is a difference.
Now, several things may effect my engine temp. First, and foremost will be=
=20
the outdoor temperature. Where I live - desert Idaho, the weather will=20
probably not change significantly for about the next 3 weeks. The=20
temperature will be a low of 55 or so, and a hi of 92 or so. The relative=
=20
humidity will be steady (and low) also, as we do not get much, if any, rain=
=20
here at this time of year. My elevation is 4800ft, so the boiling point of=
=20
water is 204=B0F, and the air is thin. Due to the thin air, a change in=20
barometric pressure could change the outcome of this test - I'll try to=20
check the weather channel. Also, wind is a large factor. =20
Going over mountain passes, I can say that the single most significant=20
factor I have seen was the load on the engine. Going up the pass, I have=20
seen my MGB hit 220=B0F, and within a half mile of going down the pass, it=
=20
comes right back to 185=B0F. This tells me the load (and hence the wind in=
=20
this test) may be a big factor. I can kind-of monitor this because I have=
=20
an intake manifold vacuum gauge installed on my car - don't ask why, it is a=
=20
long story.
Theoretically, a little retard seems that it should help, BUT (that's my big=
=20
butt) you loose the power, and thus increase the load for the same speed, as=
=20
indicated on the manifold vacuum gauge by a lower vacuum. This may cause a=
=20
hotter engine. A little advance, on the other hand, should give you more=20
power, and decrease the load, BUT as someone else mentioned, the ingnited=20
fuel is in the cylinder chamber longer. So, there must be a balance - I=20
plan to find it!
On other cars, I have used the old "set it by ear" method, and it worked=20
well. The method is to over-advance a little, find a good parking lot, and=
=20
floor the car in 1st gear. If you get pinging, you have to back it off. =20
Keep the maximum advance you can, and you get the best balance of power and=
=20
economy. If I remember right, a little too much advance gave good=20
acceleration, but poor top speed, and a little too much retard gave better=
=20
top speed, but poor accleeration. Anyhow this was on an air cooled=20
volkswagen, with no vacuum advance, so I really couldn't moniter coolant=20
temperatures.
If pinging occurs at either the 12 or 16 degree setting, I will not continue=
=20
to test, I will go back to my 14 degree advance setting.
Phil Bates
58 MGA
67 MGB
75 Jaguar XJ12C
66 Land Rover
52 MG TD replicar (VW)
86 Peugeot 505 Turbo Gle
86 Honda Accord LX-i
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