The head temp gauges drop dramatically as the RPM gauge approaches 3000.
If I consistantly stay in a lower gear around town the dual head temp gauges read cooler. Is it less load on the engine? Will this add longevity? Will this add better gas mileage?
High RPM Equals Cool Head Temps
-
Joseph
- Posts: 593
- Joined: Sat Jul 01, 2000 12:01 am
High RPM Equals Cool Head Temps
Tiki,
There's a bunch of variables going here.
Your fuel mixture, timing, load, etc. Were
the engine in a "perfect state". A change
in mechanical speed like the fan and crank,
will blow air and cool the surface of the
engine, the engine heat (on the surface) will lag and the oil temp will spike even later than that. (Dem lazy oil gauges)
What RPM are you driving at? What's your
gear ratio and tire size?
A good example of what (could) be the problem
is a dirty engine. The cooling is not enough
until you increase the fan RPM at a lower
gear, but thats a wild guess..If it were a
stock Type 4 cooling system, the reverse
would be true- the fan blades are caked up
and loose their airfoil shape. The inside
curve of the blade catches the dirt and becomes flat and less effective. What temperatures are you reading in each head?
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud
There's a bunch of variables going here.
Your fuel mixture, timing, load, etc. Were
the engine in a "perfect state". A change
in mechanical speed like the fan and crank,
will blow air and cool the surface of the
engine, the engine heat (on the surface) will lag and the oil temp will spike even later than that. (Dem lazy oil gauges)
What RPM are you driving at? What's your
gear ratio and tire size?
A good example of what (could) be the problem
is a dirty engine. The cooling is not enough
until you increase the fan RPM at a lower
gear, but thats a wild guess..If it were a
stock Type 4 cooling system, the reverse
would be true- the fan blades are caked up
and loose their airfoil shape. The inside
curve of the blade catches the dirt and becomes flat and less effective. What temperatures are you reading in each head?
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud
-
Dave_Darling
- Posts: 2534
- Joined: Thu Apr 27, 2000 12:01 am
High RPM Equals Cool Head Temps
There are also rumors floating around that the stock cooling fan starts losing effectiveness over about 4000 or 4500 RPM.
Anyone know if this is true?
--DD
Anyone know if this is true?
--DD
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Joseph
- Posts: 593
- Joined: Sat Jul 01, 2000 12:01 am
High RPM Equals Cool Head Temps
Dave,
You're right, they are rumors. I've taken
a Type 4 fan past 7K RPM and although I
don't have a hot wire sensor, the paddle
indicator moved much further than at 4K RPM
at the fan. I can't tell you if the volume
is linear and in proportion with fan speed, but the change is significant. The fan
portion is stock, it was simply turned
faster than the crank. (1:1.
In a stock fan to crank set-up (1:1) as in
GT-3 914 racing car, the fan is always over
the 4K RPM level.
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud
You're right, they are rumors. I've taken
a Type 4 fan past 7K RPM and although I
don't have a hot wire sensor, the paddle
indicator moved much further than at 4K RPM
at the fan. I can't tell you if the volume
is linear and in proportion with fan speed, but the change is significant. The fan
portion is stock, it was simply turned
faster than the crank. (1:1.
In a stock fan to crank set-up (1:1) as in
GT-3 914 racing car, the fan is always over
the 4K RPM level.
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud
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Bleyseng
- Posts: 994
- Joined: Fri Apr 21, 2000 12:01 am
High RPM Equals Cool Head Temps
It's probably because you are moving the most cooling air across the heads (fan speed) due to the higher rpm.
Geoff
------------------
76 914 2.0L
Geoff
------------------
76 914 2.0L
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Tiki Tanner
- Posts: 126
- Joined: Fri Dec 08, 2000 12:01 am
High RPM Equals Cool Head Temps
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Joseph:
<B>Tiki,
There's a bunch of variables going here.
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud </B><HR></BLOCKQUOTE>
Joe,
I realize that there are variables involved, for example the cooling system is stock but has been totally cleaned. When I split the fan housing I found about 1/4 inch of grease and grime inside as well as a caked up fan. I sand blasted then POWDER COATED the inside of the housing and cleaned the fan blades.
Compared to my stock engine this thing is running cool as a cucumber neither HEAD TEMP gauge has gone over 200 yet. There is no problem besides the fact that I added the gauges. One side of the engine runs a tad bit hotter, the side with the number three cylinder. The air/fuel is at or near 14.7 according to my gauge. I am running a stock Vanagon tranny and stock 14 inch tires. Timing is no more than 30 degrees advanced.
The motor only has about 1000 miles on it. The farthest I have gone at high speeds is about 20 miles. I am not taching it out but I notice that if I lug it at all both of the cylinder head temps go up. I don't let the oil temp go up because I turn on the cooling fan when the oil temp passes 180 degrees.
IF KEEPING THE RPM UP WILL OVERHEAT THE HEADS WOULDN'T IT HAPPEN WITHIN 20 MILES OR SO?
FOR EXAMPLE, GOING SLOWLY UP A HILL IN A LOWER GEAR WILL NATURALLY REV THE ENGINE MORE BUT ISN'T IT SAFFER (FOR LONGEVITY) THAN STAYING IN HIGH GEAR AND LETTING THE ENGINE LUG DOWN BEFORE SHIFTING TO A LOWER GEAR? When I say rev I mean @ 3000 RPM.
JON
[This message has been edited by Tiki Tanner (edited 04-01-2001).]
[This message has been edited by Tiki Tanner (edited 04-01-2001).]
<B>Tiki,
There's a bunch of variables going here.
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud </B><HR></BLOCKQUOTE>
Joe,
I realize that there are variables involved, for example the cooling system is stock but has been totally cleaned. When I split the fan housing I found about 1/4 inch of grease and grime inside as well as a caked up fan. I sand blasted then POWDER COATED the inside of the housing and cleaned the fan blades.
Compared to my stock engine this thing is running cool as a cucumber neither HEAD TEMP gauge has gone over 200 yet. There is no problem besides the fact that I added the gauges. One side of the engine runs a tad bit hotter, the side with the number three cylinder. The air/fuel is at or near 14.7 according to my gauge. I am running a stock Vanagon tranny and stock 14 inch tires. Timing is no more than 30 degrees advanced.
The motor only has about 1000 miles on it. The farthest I have gone at high speeds is about 20 miles. I am not taching it out but I notice that if I lug it at all both of the cylinder head temps go up. I don't let the oil temp go up because I turn on the cooling fan when the oil temp passes 180 degrees.
IF KEEPING THE RPM UP WILL OVERHEAT THE HEADS WOULDN'T IT HAPPEN WITHIN 20 MILES OR SO?
FOR EXAMPLE, GOING SLOWLY UP A HILL IN A LOWER GEAR WILL NATURALLY REV THE ENGINE MORE BUT ISN'T IT SAFFER (FOR LONGEVITY) THAN STAYING IN HIGH GEAR AND LETTING THE ENGINE LUG DOWN BEFORE SHIFTING TO A LOWER GEAR? When I say rev I mean @ 3000 RPM.
JON
[This message has been edited by Tiki Tanner (edited 04-01-2001).]
[This message has been edited by Tiki Tanner (edited 04-01-2001).]
-
Joseph
- Posts: 593
- Joined: Sat Jul 01, 2000 12:01 am
High RPM Equals Cool Head Temps
Tiki,
Set the idle mixture to 12.5:1 Next thing,
how can you heads be at -200F ? Thats a
lower temp than a watercooled engine. Normal
head temp is in the 300F bracket. Where are
the head sensors located? The oil temp at
180F (which you will note is the same as the
head temp) is just starting to work at that
temp. You create water as a normal biproduct
of combustion and some gets by the rings
and into the oil. If the oil is well below
200F, the water in the oil won't gasify
(turn to steam). Its only in the gas state
that the water can be drawn out of the
crankcase through your crankcase breather.
Let the oil get to operating temp or it
won't work and you will be lubricating your
bearings with water. Go to 220F then go for
the fan.
Calibrate the head temp gauge against a
candy thermometer and put the sensors under
the spark plugs. You will get an low reading
if you put it any place else.
You did good cleaning the blower housing and
fan. The fan needs cleaning when crud builds
up on the blades. The blower housing gets
that way when the crank seal in front of the
fan leaks.
Lets see what your new readings come to. 160F
is hot to humans- 400F is hot to Type 4's.
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud
Set the idle mixture to 12.5:1 Next thing,
how can you heads be at -200F ? Thats a
lower temp than a watercooled engine. Normal
head temp is in the 300F bracket. Where are
the head sensors located? The oil temp at
180F (which you will note is the same as the
head temp) is just starting to work at that
temp. You create water as a normal biproduct
of combustion and some gets by the rings
and into the oil. If the oil is well below
200F, the water in the oil won't gasify
(turn to steam). Its only in the gas state
that the water can be drawn out of the
crankcase through your crankcase breather.
Let the oil get to operating temp or it
won't work and you will be lubricating your
bearings with water. Go to 220F then go for
the fan.
Calibrate the head temp gauge against a
candy thermometer and put the sensors under
the spark plugs. You will get an low reading
if you put it any place else.
You did good cleaning the blower housing and
fan. The fan needs cleaning when crud builds
up on the blades. The blower housing gets
that way when the crank seal in front of the
fan leaks.
Lets see what your new readings come to. 160F
is hot to humans- 400F is hot to Type 4's.
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud
-
Dave_Darling
- Posts: 2534
- Joined: Thu Apr 27, 2000 12:01 am
High RPM Equals Cool Head Temps
Actually, my understanding is that the water will outgas from the oil at 180F, it just takes longer. 180F appears to be considered the very bottom end of the "normal" temp range.
I do agree that letting the oil get up to 212F is the best idea. That's even where the "warm" viscosity for motor oils is spec'ed, and that is where they are "expected" to work.
I'd like more feedback on the fan stall myth, but I will move that to a new thread.
--DD
I do agree that letting the oil get up to 212F is the best idea. That's even where the "warm" viscosity for motor oils is spec'ed, and that is where they are "expected" to work.
I'd like more feedback on the fan stall myth, but I will move that to a new thread.
--DD
-
Tiki Tanner
- Posts: 126
- Joined: Fri Dec 08, 2000 12:01 am
High RPM Equals Cool Head Temps
O.K. time to move those sensor to underneath the spark plugs. Maybe I should take off one of my external oil coolers and stop turning the fan on so soon.
This is actually a good thing since I built this engine in order for my Vanagon to run cooler and faster.
This is actually a good thing since I built this engine in order for my Vanagon to run cooler and faster.
-
Joseph
- Posts: 593
- Joined: Sat Jul 01, 2000 12:01 am
High RPM Equals Cool Head Temps
Tiki,
I know your going to hate mr for this. BUT
don't just put the thermocouple (sensor)
under the plug. The spark plugs in a Type 4
head are in a "well" or deeply inset into
the head. In order not to distort the sensor
its best to remove the top tin (I know...)
and grind a slot at the outboard side
of # 3 or #4 cylinder spark plug hole. Cut it
down to the level of the spark plug gasket (about 1/4" wide). That permits the tail of
the thermocouple to stay flat. The rest of
the installation is in the instruction sheet.
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud
I know your going to hate mr for this. BUT
don't just put the thermocouple (sensor)
under the plug. The spark plugs in a Type 4
head are in a "well" or deeply inset into
the head. In order not to distort the sensor
its best to remove the top tin (I know...)
and grind a slot at the outboard side
of # 3 or #4 cylinder spark plug hole. Cut it
down to the level of the spark plug gasket (about 1/4" wide). That permits the tail of
the thermocouple to stay flat. The rest of
the installation is in the instruction sheet.
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud
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Marco Robert
- Posts: 43
- Joined: Wed Dec 20, 2000 12:01 am
High RPM Equals Cool Head Temps
Joseph,
Would it be possible somehow to hook-up a gauge to the stock cyl.head temp sensor for the injection control unit, wich bolts in the threaded hole on the injected heads ?
Would it be possible somehow to hook-up a gauge to the stock cyl.head temp sensor for the injection control unit, wich bolts in the threaded hole on the injected heads ?
-
stevestromberg
- Posts: 434
- Joined: Tue Mar 13, 2001 12:01 am
High RPM Equals Cool Head Temps
Tiki has two senders mounted in the stock location. Steve
-
Joseph
- Posts: 593
- Joined: Sat Jul 01, 2000 12:01 am
High RPM Equals Cool Head Temps
Marco,
Hooking up a VDO sender to where the original
FI is located won't work. The temperture on
the head changes as it goes from the
combustion chamber outward. You can guess
what the results would be if you hooked the
stock FI sensor under the spark plug. Sensors
are designed to operate in certain temps and convert some of the heat to low voltage. Even
the wires from the sensor to the gauge will
contribute a calculated resistance on the
way to the gauge and must not be altered.
Key to good monitoring is the correct
placement of the sensor and the accuracy of
the readout. Timeliness is also a factor
since the gauge will read out that which has
already happened. How long it takes to read
that information dictates on how fast you
can respond to it. That in itself seriously
handicaps oil temperature gauges as a vanguard of engine protection. They are
notorious for lagging back well past the
time of a serious engine temperature spike.
It is'nt the instrument that is slow, it the
oil that must first absorb the heat.
The CHT (cylinder head temp) will also lag
but not as long as the oil readout thus
making it the best insurance for your engine.
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud
Hooking up a VDO sender to where the original
FI is located won't work. The temperture on
the head changes as it goes from the
combustion chamber outward. You can guess
what the results would be if you hooked the
stock FI sensor under the spark plug. Sensors
are designed to operate in certain temps and convert some of the heat to low voltage. Even
the wires from the sensor to the gauge will
contribute a calculated resistance on the
way to the gauge and must not be altered.
Key to good monitoring is the correct
placement of the sensor and the accuracy of
the readout. Timeliness is also a factor
since the gauge will read out that which has
already happened. How long it takes to read
that information dictates on how fast you
can respond to it. That in itself seriously
handicaps oil temperature gauges as a vanguard of engine protection. They are
notorious for lagging back well past the
time of a serious engine temperature spike.
It is'nt the instrument that is slow, it the
oil that must first absorb the heat.
The CHT (cylinder head temp) will also lag
but not as long as the oil readout thus
making it the best insurance for your engine.
Joe
Oregon Performance Products http://www.spiretech.com/~opshroud