The type, style, or condition of the radiator cannot affect the temperature
differential of the heads.
Since there is only one water pump with one inlet, all coolant from either
bank is thoroughly mixed and enters the engine at one temperature. The outlet
temperature for each bank is entirely dependent of what goes on inside that
cylinder bank and the individual head. How many passes through the radiator
or the placement of the tap for the heater core won’t effect the head
temperature differential.
If we want to fix a temperature differential look in the engine, if we want
to fix how much cooling there is look at the radiator and fan system.
To be able to tell which problem a car has, we probably need a three sensor
water temp system. One sensor on each head outlet and the third at the water
pump inlet. That way a person could determine if the temperature problem is
too much heat in the engine (and which bank it’s coming from) or not enough
cooling by the radiator / fan system.
The type, style, or condition of the radiator cannot affect the
temperature differential of the heads.
Yes, it can, and it does. In the case of the stupid 2-pass design
used in the Jaguar XJ-S and XJ12, the left bank will always see a
lower coolant flow rate than the right bank. ALWAYS. And a lower
coolant flow rate means a higher temp.
– Kirbert | Palm’s Postulate:
| If anything is to be accomplished,
| some rules must be broken.
| – Kirby Palm, 1979From: GAPMe@aol.com
Robert Warnicke wrote:
So would adding a restriction to slow down the rate of only the A bank
to make it the same as that of the B bank, cause the A bank to run hoter
or the B to run cooler?
Every time I try to figure that out, my head starts to hurt. The direct
result, obviously, is that the A bank flow will be reduced to the same
as the B bank, which would make it run warmer. But making it run warmer
would mean that the thermostat would open up, which means the bypass
port would be closed off a little more. Which means, I think, that
the TOTAL amount of coolant flow through the system may be reduced, but
that reduction may be nearly all in the bypass, and the flow through the
rad will remain fundamentally unchanged. And since the flow through the
rad is actually what determines the total cooling, the total cooling
should remain basically unchanged – except that now it is equally
divided between banks, rather than preferring the A bank.
Despite how confused I am on the nature of that change, I am pretty
convinced of one thing: whatever the restrictor in the RH radiator hose
does, it’s good. I don’t believe it can cause cooling problems (unless
it is way too restrictive, obviously!), and having the two banks running
at the SAME temperature should actually have a bunch of benefits. The
ECU will provide better fuelling to the A bank, the AAV will probably
work better, the gauge on the dash will read reality!
– Kirbert | If anything is to be accomplished,
| some rules must be broken.
| - Palm’s Postulate
G’Day
I am particularly interested in this thread.
Earlier it was suggested that the left bank outlet should be piped across
and tee’d in with the right bank then into the radiator.
Surely that is basically what already happens.
The top third of the radiator is in fact the pipe going across to the RHS.
Albeit this pipe has the advantage of cooling provision. It would be handy
to know how many tubes and their effective cross sectional area are in the
top third of the rad. Then calculate how that compares to a piece of pipe
going from Left to Right.
The problem surely must be more apparent as the rad. blocks up. I can
imagine the rad. would have two main blockage sites. One would be at the
bottom RHS and the other at the bottom of the top third of the LHS. This
then would create a progressively extra back pressure, or flow restriction
to the Left bank.
I figure the thermostats would compensate for this until such time as one
reaches fully open, then the temperature differential would take place.
One can draw an interesting equivalent electrical cct. for this whole
dilemma. A series parallel network.
Regards
Ken
Kirby Palm wrote:
Robert Warnicke wrote:
So would adding a restriction to slow down the rate of only the A bank
to make it the same as that of the B bank, cause the A bank to run hoter
or the B to run cooler?Every time I try to figure that out, my head starts to hurt.
Despite how confused I am on the nature of that change, I am pretty
convinced of one thing: whatever the restrictor in the RH radiator hose
does, it’s good. I don’t believe it can cause cooling problems (unless
it is way too restrictive, obviously!), and having the two banks running
at the SAME temperature should actually have a bunch of benefits. The
ECU will provide better fuelling to the A bank, the AAV will probably
work better, the gauge on the dash will read reality!
So Kirby has a restriction in the A bank Gano filter, and Mark Young
has a temp gauge in both sides, what we need is to have one or the other
of you to put the two mods together…
What I would also like to know is if Chad’s heads are running at
different temps. If he has a really long pipe crossing over from one
side to the other, would that essentially be creating the same problem,
or is it different because the top 1/3 of the radiator is more
restrictive than his cross over pipe?
Now I have the headache…–
Robert
73XJ12 (to be HE)
87XJ-SC
My Jaguar page at: http://members.home.net/obstinate
Ken Gray wrote:
Earlier it was suggested that the left bank outlet should be piped across
and tee’d in with the right bank then into the radiator.
Surely that is basically what already happens.
The top third of the radiator is in fact the pipe going across to the RHS.
Good theory, as long as the top 1/3 of the core has comparable flow
resistance to a 1-1/4" hose. I’m betting it doesn’t. And the 1-1/4"
hose won’t get plugged with Barr’s Leaks.
It would be handy
to know how many tubes and their effective cross sectional area are in the
top third of the rad.
Yes, it would. Somebody cut one open!
– Kirbert | If anything is to be accomplished,
| some rules must be broken.
| - Palm’s Postulate