thermostat question?? now i did my research
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03-17-2007, 12:48 AM
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03-17-2007, 03:40 AM
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03-17-2007, 04:09 AM
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#5
03-17-2007, 04:23 AM
Champion
RE: thermostat question?? now i did my research
ORIGINAL: Dodge Tech
who said it was good to go lower temp??? My thinking on it is if the car maker makes something with the engine set to a certan temp and u lower ot make it hotter it will infact change how the truck runs and burns the air fuel mixture.
who said it was good to go lower temp??? My thinking on it is if the car maker makes something with the engine set to a certan temp and u lower ot make it hotter it will infact change how the truck runs and burns the air fuel mixture.
Manufacturers use 195 degree thermostats because hotter engine temps help reduce emissions, but you increase the chance of detonation. By running a lower temp thermostat you may increase your emissions, but you'll run cooler which reduces detonation and allows you to run more timing advance, creating more power. In addition, your intake manifold will be a little cooler, causing the intake charge to be a little more dense, allowing more fuel to be burned, which also increases power.
160 degrees is far too low, your engine will think it's in warm-up mode (choke on) causing your A/F mixture to be less than optimal. 180 degrees is widely thought to be about the best temp.
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03-17-2007, 05:04 AM
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#7
03-17-2007, 10:20 AM
RE: thermostat question?? now i did my research
from the FAQ:
----
Coolant temperatures and thermostat settings
There is controversy about MPG and thermostat temperatures but there
seems to be a clear trend that higher coolant temperatures controlled by
195-203 setting thermostats improve MPG slightly.
Sadie Carnot's 200 year old thermodynamic theory says
that cooler air intake temperatures would give improved fuel economy
because cooler air takes slightly less work to compress, and if a
140-180 thermostat is used on an old fashioned iron or aluminum
intake manifold with coolant cross-over passages there will
be less temperature rise in the intake air as it passes through.
Modern intake manifolds such as the ones on the 4.7V8 and 5.7 Hemi
are made of insulating Nylon66 plastic so this does not
apply as much - although the incoming air can still pick up
heat from the metal walls of the cylinder head ports.
But hotter oil on cylinder walls has less viscosity and creates less
friction against the piston rings - which can also mean better MPG. The
Cummins 'Secrets of Better Fuel Economy' white paper listed at the top has a
graph showing this on page 12. Theory also predicts that hotter block walls
and cylinder heads will absorb less heat from combustion and permit a greater
pressure 'push' on the piston.
The new four cylinder 'World Engine' in the 2006 Dodge Caliber has two
thermostats: one to feed lots of cooler coolant flow to the cylinder heads
so that pinging will be reduced and an MPG improving higher compression
ratio can be used - but another separate thermostat setting to adjust the flow
to the engine block walls so that they stay hotter and ring friction will be
lower. This may be the best of both needs.
Some Dakota owners who switched to 180 degree thermostats have reported less
ping, peppier acceleration and about +1 mpg, although most reports like this
are just about what their next tank of gasoline yielded - not a careful test
that you can trust. Other Dakota owners reported no mpg change or a loss.
Four Wheeler magazine reported +0.8 mpg gain with a 192 to 180 deg
thermostat swap in a 454 Suburban. Take these reports with a grain of salt
considering who did them and how magazines live on advertising.
My own experiments with a failed thermostat that cracked and stayed open at
around 140 degrees, then later thermostats of 180, 195 (stock) & 205 showed
no significant improvement in MPG at steady 60 mph highway cruise
on a 1995 5.9V8 Ram CCab shortbed, although the 205 did measure a
0.2 MPG gain in one 300 mile test run.
The 180 degree thermostat also did not reducing pinging at least 'by ear',
nor did the 205 thermostat increase pinging by ear, but a better test would
have been to measure with a MSD aftermarket knock sensor, or better yet
read the memory of a J&S aftermarket anti-knock ignition system with its
twin knock sensors and better knock detecting software & chip.
Why would this be if you have read a thousand internet postings that
180 degree thermostats reduce detonation? This may be because the
Dodge PCM computer senses coolant temperature and either
advances or retards ignition timing as necessary according to the
tables in the memory of the computer's software. The cracked
thermostat that stayed open at about 140 did reduce pinging by ear.
When you read that 180 degree thermostats reduced pinging on old
carburetor engines that might be true, but consider that today's
computer controlled engines 'have a mind of their own'
inside the PCM that carb'ed engines did not.
The Fuel Economy Calculator from Performance Trends software predicts that a
change from a 195 degree thermostat to a 175 worsens MPG by about 0.20 at a
steady 70 mph.
Respected tech editor Marlan Davis of Hot Rod magazine has reported that
all things considered, fuel economy is better with coolant at 210 degrees F.
Perhaps that is why the factory thermostat on the 5.7 Hemi is now marked 203
F, which is were it begins opening. Note that on 4.7 and 5.7Hemi engines the
thermostat position and function has been totally redesigned to control the
coolant in, rather than the coolant out temperature. This would lead one to
guess that the coolant coming out of a 5.7 Hemi is hotter still. The 5.7V8
now also has a closing bypass post sticking out from it that closes off the
bypass passage and results in greater coolant flow to the radiator once the
engine is up to designed temperature. This allows the water pump to be run
slightly lower in rpm and saves a bit of fuel.
Coolant temperatures also affect bore wall wear,
according to experiments run by aircraft engine manufacturer Continental Engines in the 1960s.
Bore wear is relatively high at 140-160 degrees but begins rapidly leveling
off at 180 and shows no improvement above 205. It is thought that this wear
effect is due to acidic liquids condensing on the metal bore walls and
corroding them. Above a certain coolant temperature the liquids never
condense and remain gases. A similar problem happens in the chimneys
of power plants.
----
Coolant temperatures and thermostat settings
There is controversy about MPG and thermostat temperatures but there
seems to be a clear trend that higher coolant temperatures controlled by
195-203 setting thermostats improve MPG slightly.
Sadie Carnot's 200 year old thermodynamic theory says
that cooler air intake temperatures would give improved fuel economy
because cooler air takes slightly less work to compress, and if a
140-180 thermostat is used on an old fashioned iron or aluminum
intake manifold with coolant cross-over passages there will
be less temperature rise in the intake air as it passes through.
Modern intake manifolds such as the ones on the 4.7V8 and 5.7 Hemi
are made of insulating Nylon66 plastic so this does not
apply as much - although the incoming air can still pick up
heat from the metal walls of the cylinder head ports.
But hotter oil on cylinder walls has less viscosity and creates less
friction against the piston rings - which can also mean better MPG. The
Cummins 'Secrets of Better Fuel Economy' white paper listed at the top has a
graph showing this on page 12. Theory also predicts that hotter block walls
and cylinder heads will absorb less heat from combustion and permit a greater
pressure 'push' on the piston.
The new four cylinder 'World Engine' in the 2006 Dodge Caliber has two
thermostats: one to feed lots of cooler coolant flow to the cylinder heads
so that pinging will be reduced and an MPG improving higher compression
ratio can be used - but another separate thermostat setting to adjust the flow
to the engine block walls so that they stay hotter and ring friction will be
lower. This may be the best of both needs.
Some Dakota owners who switched to 180 degree thermostats have reported less
ping, peppier acceleration and about +1 mpg, although most reports like this
are just about what their next tank of gasoline yielded - not a careful test
that you can trust. Other Dakota owners reported no mpg change or a loss.
Four Wheeler magazine reported +0.8 mpg gain with a 192 to 180 deg
thermostat swap in a 454 Suburban. Take these reports with a grain of salt
considering who did them and how magazines live on advertising.
My own experiments with a failed thermostat that cracked and stayed open at
around 140 degrees, then later thermostats of 180, 195 (stock) & 205 showed
no significant improvement in MPG at steady 60 mph highway cruise
on a 1995 5.9V8 Ram CCab shortbed, although the 205 did measure a
0.2 MPG gain in one 300 mile test run.
The 180 degree thermostat also did not reducing pinging at least 'by ear',
nor did the 205 thermostat increase pinging by ear, but a better test would
have been to measure with a MSD aftermarket knock sensor, or better yet
read the memory of a J&S aftermarket anti-knock ignition system with its
twin knock sensors and better knock detecting software & chip.
Why would this be if you have read a thousand internet postings that
180 degree thermostats reduce detonation? This may be because the
Dodge PCM computer senses coolant temperature and either
advances or retards ignition timing as necessary according to the
tables in the memory of the computer's software. The cracked
thermostat that stayed open at about 140 did reduce pinging by ear.
When you read that 180 degree thermostats reduced pinging on old
carburetor engines that might be true, but consider that today's
computer controlled engines 'have a mind of their own'
inside the PCM that carb'ed engines did not.
The Fuel Economy Calculator from Performance Trends software predicts that a
change from a 195 degree thermostat to a 175 worsens MPG by about 0.20 at a
steady 70 mph.
Respected tech editor Marlan Davis of Hot Rod magazine has reported that
all things considered, fuel economy is better with coolant at 210 degrees F.
Perhaps that is why the factory thermostat on the 5.7 Hemi is now marked 203
F, which is were it begins opening. Note that on 4.7 and 5.7Hemi engines the
thermostat position and function has been totally redesigned to control the
coolant in, rather than the coolant out temperature. This would lead one to
guess that the coolant coming out of a 5.7 Hemi is hotter still. The 5.7V8
now also has a closing bypass post sticking out from it that closes off the
bypass passage and results in greater coolant flow to the radiator once the
engine is up to designed temperature. This allows the water pump to be run
slightly lower in rpm and saves a bit of fuel.
Coolant temperatures also affect bore wall wear,
according to experiments run by aircraft engine manufacturer Continental Engines in the 1960s.
Bore wear is relatively high at 140-160 degrees but begins rapidly leveling
off at 180 and shows no improvement above 205. It is thought that this wear
effect is due to acidic liquids condensing on the metal bore walls and
corroding them. Above a certain coolant temperature the liquids never
condense and remain gases. A similar problem happens in the chimneys
of power plants.
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#8
03-17-2007, 04:10 PM
Champion
RE: thermostat question?? now i did my research
Well that's interesting. Speaking from personal experience though I can tell you that I've gained highway economy, but it's not just the tstat doing it - I swapped in a 180 t-stat, went 1 heat range cooler on my spark plugs, switched to 92ish octane, and I'm running the 93 octane tune from a hypertech tuner. Obviously all things being similar, the thermostat isn't going to produce much of a difference on its own, and it sounds like the newer engines are even more high tech - making old school train of thought a little obsolete. The LA based magnums are pretty old school themselves though.
#9
03-17-2007, 04:59 PM
Grand Champion
