Home » Public Forums » GMCnet » [GMCnet] Fan Clutch
| Re: [GMCnet] Fan Clutch [message #61517 is a reply to message #61277] |
Sat, 24 October 2009 21:16   |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Rick
I don't know where your got your Hayden (2797?) I got mine some time ago from Pep Boys. It has a life time guarantee and I have brought back at least a half a dozen that I had a problem with over the years. The last one is the best of the lot,I can hear it come on but it doesn't roar so loud that it drives you nuts. It is just loud enough that I know it is working then it shuts off. When I first start the engine it doesn't come on like the prior ones did, all I know is it works. The 2797 that I have is definitely different then the ones I had in the past.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Fan Clutch [message #61518 is a reply to message #61517] |
Sat, 24 October 2009 21:19 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| roy1 wrote on Sat, 24 October 2009 21:16 |
Rick
I don't know where your got your Hayden (2797?) I got mine some time ago from Pep Boys. It has a life time guarantee and I have brought back at least a half a dozen that I had a problem with over the years. The last one is the best of the lot,I can hear it come on but it doesn't roar so loud that it drives you nuts. It is just loud enough that I know it is working then it shuts off. When I first start the engine it doesn't come on like the prior ones did, all I know is it works. The 2797 that I have is definitely different then the ones I had in the past.
Roy
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I got my 4 troublesome Haydens from Pep Boys. I also got my refund from Pep Boys when I took them back.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Fan Clutch [message #61521 is a reply to message #61518] |
Sat, 24 October 2009 21:38 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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That thought entered my mind when I was having trouble with them
but the original cash out lay was so little that it wasn't worth the trouble and I got so good at changing it in a short time that I figured maybe the next one would be a good one. So far I am happy with the current one. It is relatively quiet and it comes on at just the time I start thinking is it working. The last one came on way too early,the one I have now is definitely a different unit. I guess time will tell.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| [GMCnet] Horsepower and Torque Converter Efficiency [message #61530 is a reply to message #61445] |
Sun, 25 October 2009 04:55 |
Gary Casey
Messages: 448
Registered: September 2009
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I was digging through some old GM test data and thought I would share the following:
Olds 455 test data with an uncertain pedigree (Toro or not? Test conditions?) and it showed a torque at 2800 and below of about 398. No data below 2000, but other tests implied a peak torque at 1200 to 1600 rpm. Peak hp was 234 at 3600.
Cadillac 500 EFI - peak torque 395 at 1200 and 1600 rpm. Peak hp 225 at 3600. The engine was knock limited and spark was retarded about 10 degrees from MBT at most rpms. Both of these are consistent with other big GM engines built at the time(except for the knock-limited part). Max torque was always below 2000 rpm and peak hp was never above 4000. That's not counting performance engines like the Chevy 427 or the Chrysler Hemi, of course.
Olds 350 EFI (Cadillac Seville) - peak torque 290 at 1200, peak power 190 at 4400 and still rising. Not knock limited.
If the Cad 500 were tested on today's fuels would it be knock-limited? Don't know.
Here is some examples using a typical fixed-pitch torque converter with a 2.05 stall torque ratio:
Stall speed, assuming 400 ft-lb input - 2253 rpm.
The efficiency rises with increasing speed, so I picked a couple of operating conditions to look at - one was for a "high-load" cruise with 150 ft-lb input. I think actual loads might a little less for a coach without a trailer. The efficiency rises, and the torque ratio drops and reaches a peak of about 92% efficiency. Then there is a dip at the coupling point where the torque ratio becomes 1.0 and from then on the efficiency continues to rise. I haven't made a chart of this to post, so I hope you get the idea. In the cruise assumption the efficiency reaches 88% at an engine speed of 1491 and finally climbs over 92% at 1890. At 2500 it is over 96%, so at a normal cruise speed the efficiency loss is probably 4% or less. Not too bad, but not good.
At full load as might be used climbing a hill I assumed an input torque of 360, not quite full throttle, but close, and on a hot day at any normal elevation that might be all there is. The converter reached 88% efficiency at 2310 engine rpm and finally climbed over 92% at 2930. What that says is that if you are running with your foot in it you want to have the rpm over 2930 or you can expect to be putting about 10% of the engine hp into the transmission oil. Really not good, unless you have a direct pipeline to a refinery and have a really big oil cooler. Better to downshift.
Hopefully this data will be useful to somebody.
Gary
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| Re: [GMCnet] Horsepower and Torque Converter Efficiency [message #61534 is a reply to message #61530] |
Sun, 25 October 2009 06:29 |
GMCWiperMan
Messages: 1248
Registered: December 2007
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Good information, Gary,
The Cad 500 numbers are surprising considering the enthusiastic
performance reports from those who've made the conversion. The retarded
spark must have made a BIG difference.
Don't Lug!
Thanks,
Ken H.
Gary Casey wrote:
> I was digging through some old GM test data and thought I would share the following:
>
> Olds 455 test data with an uncertain pedigree (Toro or not? Test conditions?) and it showed a torque at 2800 and below of about 398. No data below 2000, but other tests implied a peak torque at 1200 to 1600 rpm. Peak hp was 234 at 3600.
>
> Cadillac 500 EFI - peak torque 395 at 1200 and 1600 rpm. Peak hp 225 at 3600. The engine was knock limited and spark was retarded about 10 degrees from MBT at most rpms. Both of these are consistent with other big GM engines built at the time(except for the knock-limited part). Max torque was always below 2000 rpm and peak hp was never above 4000. That's not counting performance engines like the Chevy 427 or the Chrysler Hemi, of course.
>
> Olds 350 EFI (Cadillac Seville) - peak torque 290 at 1200, peak power 190 at 4400 and still rising. Not knock limited.
>
> If the Cad 500 were tested on today's fuels would it be knock-limited? Don't know.
>
> Here is some examples using a typical fixed-pitch torque converter with a 2.05 stall torque ratio:
> Stall speed, assuming 400 ft-lb input - 2253 rpm.
> The efficiency rises with increasing speed, so I picked a couple of operating conditions to look at - one was for a "high-load" cruise with 150 ft-lb input. I think actual loads might a little less for a coach without a trailer. The efficiency rises, and the torque ratio drops and reaches a peak of about 92% efficiency. Then there is a dip at the coupling point where the torque ratio becomes 1.0 and from then on the efficiency continues to rise. I haven't made a chart of this to post, so I hope you get the idea. In the cruise assumption the efficiency reaches 88% at an engine speed of 1491 and finally climbs over 92% at 1890. At 2500 it is over 96%, so at a normal cruise speed the efficiency loss is probably 4% or less. Not too bad, but not good.
>
> At full load as might be used climbing a hill I assumed an input torque of 360, not quite full throttle, but close, and on a hot day at any normal elevation that might be all there is. The converter reached 88% efficiency at 2310 engine rpm and finally climbed over 92% at 2930. What that says is that if you are running with your foot in it you want to have the rpm over 2930 or you can expect to be putting about 10% of the engine hp into the transmission oil. Really not good, unless you have a direct pipeline to a refinery and have a really big oil cooler. Better to downshift.
>
> Hopefully this data will be useful to somebody.
> Gary
>
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| Re: [GMCnet] Horsepower and Torque Converter Efficiency [message #61547 is a reply to message #61534] |
Sun, 25 October 2009 09:13 |
Gary Casey
Messages: 448
Registered: September 2009
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Yes, the Cad 500 was sort of a standing joke around GM. They started with about 420 cu. in.(I forgot what) and went to 472 and then 500 every time Ford came out with a bigger engine for the Lincoln. Every time they made the engine bigger the power went down. They actually had a 600 on the drawing board, but the gas crisis saved us all from that.
But is the 500 a better engine than the Olds 455? No idea, but some seem to be happy with the 500. As for me, I had this daydream about a twin turbo 350....then my sanity returned. Actually, a smaller displacement higher rpm engine coupled with a higher final drive ratio could work well, if only because of the increased converter efficiency.
Gary, not lugging, Casey
________________________________
Good information, Gary,
The Cad 500 numbers are surprising considering the enthusiastic
performance reports from those who've made the conversion. The retarded
spark must have made a BIG difference.
Don't Lug!
Thanks,
Ken H.
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| Re: [GMCnet] Horsepower and Torque Converter Efficiency [message #61557 is a reply to message #61530] |
Sun, 25 October 2009 10:59 |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
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Gary;
What this says to me is the higher numerical final drives will provide
the 92% efficiency on hills, with less attention by the driver. I have
experienced the sudden increase in transmission oil temperature on every
hill as I was allowing the rpm to drop to 2400 before down shifting. I
have also adopted the habit of turning on the twin electric fans on my
oil cooler when I see a hill coming, as this will keep the trans oil
temperature below 185*F on the steepest, longest hills I have
encountered. I will now pull all hills @ 3000 rpm. Back to driving a
gas powered standard shift truck. 3000 rpm seemed to be the "sweet
spot" with GM 366/427/454 Class 5 trucks.
Thank you for the information;
Gordon
Gary Casey wrote:
> 92% at 2930. What that says is that if you are running with your
> foot in it you want to have the rpm over 2930 or you can expect to be
> putting about 10% of the engine hp into the transmission oil. Really
> not good, unless you have a direct pipeline to a refinery and have a
> really big oil cooler. Better to downshift.
>
> Hopefully this data will be useful to somebody. Gary
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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| Re: [GMCnet] Fan Clutch [message #61566 is a reply to message #61560] |
Sun, 25 October 2009 11:52 |
emerystora
Messages: 4442
Registered: January 2004
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On Oct 25, 2009, at 10:30 AM, Roger P. Gleason wrote:
>
> Now for a question, several have lowered their engine thermostats
> from the recommended 195 degree to 185 degrees, what is the purpose
> of this? The newer gasoline’s are formulate where it takes
> higher temperatures to burn them completely some of the newer
> engines are using as high as 210 degree thermostats to accomplish a
> complete burn. Engines I have seen torn down with too low of
> thermostat leave unburned deposits in the heads leading to
> catastrophic failures.
>
Roger
I agree with you totally on this. I think that many have put in lower
temperature thermostats thinking that they would result in less
overheating. This perhaps is an attempt to mask a radiator problem or
other such engine problem that has resulted in their overheating.
I first posted this back in 2003:
> In the old days thermostats used to all be 160-180 degrees. Now they
> are 20 or 30 degrees hotter. Why was this done? Its fairly common
> knowledge that heat is the worst enemy of engines and oils. -- right?
> It's true that heat can be hard on an engine, but in the opinion of
> most automotive engineers, the benefits of hotter-running engines far
> outweigh the negatives. Engines burn fuel more cleanly and
> efficiently at higher temperatures. With the coolant at 195 degrees
> (instead of 160 to 180), you'll get better performance. less
> pollution overall, and greater fuel economy.
>
> While 30 years or so ago, using a 195 degree thermostat might have
> shortened the life of an engine, oils have gotten better. Now they
> perform much better in extreme heat, and give the engine plenty of
> protection without breaking down. Especially with the Mobil 1
> synthetic that you are using. Modern big block engines such as the
> 403 and 455 are optimized to run at 195 to 200 degrees and at that
> temperature no harm is done.
>
> Race cars are designed to run at even hotter temperatures with the
> result that higher compression ratios are possible as well as more
> aggressive ignition advance curves and leaner mixtures for greater
> fuel efficiency. While our GMCs are certainly not race cars, the
> same fundamentals apply.
>
> I will continue to use my 195 deg. thermostat. I rely on a 50/50 mix
> of antifreeze coolant, an operating 9# pressure cap (these usually go
> bad within two years) and a clean radiator and engine block to keep
> me from overheating. If your cooling system has problems, using a
> 160 or 180 thermostat will only give a very slight edge to slowing
> down an overheating problem. The engine can quickly pick up 30 or 40
> degrees when under load at high speeds or up grades.
>
> Another potential problem with running too low an engine temperature
> is that any condensation in the engine block must be evaporated by
> the heat of the engine to prevent the water from floating around in
> the oil pan and being picked up by the oil pump and getting into the
> bearings, etc. Water is not a good lubricant. It also will rust
> parts in the engine block.
>
> All engines will pick up water. When an engine cools the air in the
> crankcase shrinks and air is drawn into the block. Air contains
> water vapor which will condense into the engine. Most people that
> live in cold climate areas use higher temperature thermostats in cold
> weather to keep their heaters putting out enough heat to the
> interior. People in warmer climates often feel that they don't need
> as high a temperature thermostat but those living in the south where
> there is high humidity or even in the humid north still have water
> condensate in their engines which must be dried out. A hotter engine
> will do a better job of quickly evaporating this water before it does
> any harm.
Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] "six-speed" transmission [message #61570 is a reply to message #61556] |
Sun, 25 October 2009 12:02 |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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Emery,
I wish I had some of my old converter data, but I can't find anything on variable pitch units. In one position they increase the stall speed and stall torque ratio (useful for backing up a hill). That has a byproduct of reducing the load on the engine at idle, which can be an advantage with a carburetor(easier to get a smooth, no-stall idle). Then the other pitch extends the torque multiplication out further in the speed range at the price of a lower stall torque ratio. Unfortunately, that reduces the efficiency as well. So, at 25 to 35 mph up a grade do you want to run full throttle at 90% efficiency with a torque ratio of 1.1, or run part throttle at a slightly higher engine speed at a torque ratio of 1.48(second gear) and 97% efficiency? At the higher efficiency the engine will have to put out less torque to do the same work. The converter characteristic in that mode is very similar to modern cars with converter clutches. Quite often they will
be programmed to disconnect the converter clutch going up a hill to give a perceived performance increase, when most of the extra engine power is just going into heat. My car has a throttle-by-wire system and I swear they program the throttle to open when the converter clutch is disengaged, to make you think you are getting something for nothing. No free lunch, I'm afraid.
Gary
________________________________
From: Emery Stora <emerystora@mac.com>
To: "gmclist@temp.gmcnet.org" <gmclist@temp.gmcnet.org>
Sent: Sun, October 25, 2009 9:54:04 AM
Subject: Re: [GMCnet] "six-speed" transmission
On Oct 25, 2009, at 9:31 AM, Gary Casey <casey.gary@yahoo.com> wrote:
> I'd respectfully consider the variable pitch stator to make the 3-
> speed transmission into a "3 1/2 speed" transmission. Or maybe "3
> 1/4". As I said before, the low pitch might enable you to back out
> of a steep downhill parking spot, but that's about it. Just my
> opinion again.
> Gary
>
I find the main advantage of my switch pitch is the help it gives in
keeping up RPMs when going up hills. It allows one to pass that truck
that is slowing down in front instead of forcing you to drop behind
and slowing down to perhaps 25 mph where you loose all rpm and drop
way down on the torque curve.
Emery Stora
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| Re: [GMCnet] Fan Clutch [message #61575 is a reply to message #61566] |
Sun, 25 October 2009 12:32 |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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Senior Member |
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I agree with Emery on every point but one. Certainly whether the engine has a 180 or 195 thermostat the overheat margin will be the same. The coolant will boil at about 250 and by then either thermostat will be wide open, so it just doesn't matter. Sure, if the engine was running at 180 before you got to the hill, there is a little more time before it overheats, but it will still overheat if it's going to.
But the lower the engine temperature the more resistant it is to detonation and the more power it will have. The latter because heat is transferred to the intake charge and the inlet temperature will be lower if the engine is running cooler. At Mercury Marine we used "blow-open" thermostats that would open at high engine speeds, dropping the temperature(unlimited cooling water available. We got more power and, very important for the 502, more margin to pre-ignition. Hydrocarbon emissions will be lower at higher temperatures.
Gary
________________________________
From: Emery Stora <emerystora@mac.com>
To: gmclist@temp.gmcnet.org
Sent: Sun, October 25, 2009 10:52:56 AM
Subject: Re: [GMCnet] Fan Clutch
On Oct 25, 2009, at 10:30 AM, Roger P. Gleason wrote:
>
> Now for a question, several have lowered their engine thermostats
> from the recommended 195 degree to 185 degrees, what is the purpose
> of this? The newer gasoline’s are formulate where it takes
> higher temperatures to burn them completely some of the newer
> engines are using as high as 210 degree thermostats to accomplish a
> complete burn. Engines I have seen torn down with too low of
> thermostat leave unburned deposits in the heads leading to
> catastrophic failures.
>
Roger
I agree with you totally on this. I think that many have put in lower
temperature thermostats thinking that they would result in less
overheating. This perhaps is an attempt to mask a radiator problem or
other such engine problem that has resulted in their overheating.
I first posted this back in 2003:
> In the old days thermostats used to all be 160-180 degrees. Now they
> are 20 or 30 degrees hotter. Why was this done? Its fairly common
> knowledge that heat is the worst enemy of engines and oils. -- right?
> It's true that heat can be hard on an engine, but in the opinion of
> most automotive engineers, the benefits of hotter-running engines far
> outweigh the negatives. Engines burn fuel more cleanly and
> efficiently at higher temperatures. With the coolant at 195 degrees
> (instead of 160 to 180), you'll get better performance. less
> pollution overall, and greater fuel economy.
>
> While 30 years or so ago, using a 195 degree thermostat might have
> shortened the life of an engine, oils have gotten better. Now they
> perform much better in extreme heat, and give the engine plenty of
> protection without breaking down. Especially with the Mobil 1
> synthetic that you are using. Modern big block engines such as the
> 403 and 455 are optimized to run at 195 to 200 degrees and at that
> temperature no harm is done.
>
> Race cars are designed to run at even hotter temperatures with the
> result that higher compression ratios are possible as well as more
> aggressive ignition advance curves and leaner mixtures for greater
> fuel efficiency. While our GMCs are certainly not race cars, the
> same fundamentals apply.
>
> I will continue to use my 195 deg. thermostat. I rely on a 50/50 mix
> of antifreeze coolant, an operating 9# pressure cap (these usually go
> bad within two years) and a clean radiator and engine block to keep
> me from overheating. If your cooling system has problems, using a
> 160 or 180 thermostat will only give a very slight edge to slowing
> down an overheating problem. The engine can quickly pick up 30 or 40
> degrees when under load at high speeds or up grades.
>
> Another potential problem with running too low an engine temperature
> is that any condensation in the engine block must be evaporated by
> the heat of the engine to prevent the water from floating around in
> the oil pan and being picked up by the oil pump and getting into the
> bearings, etc. Water is not a good lubricant. It also will rust
> parts in the engine block.
>
> All engines will pick up water. When an engine cools the air in the
> crankcase shrinks and air is drawn into the block. Air contains
> water vapor which will condense into the engine. Most people that
> live in cold climate areas use higher temperature thermostats in cold
> weather to keep their heaters putting out enough heat to the
> interior. People in warmer climates often feel that they don't need
> as high a temperature thermostat but those living in the south where
> there is high humidity or even in the humid north still have water
> condensate in their engines which must be dried out. A hotter engine
> will do a better job of quickly evaporating this water before it does
> any harm.
Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] Fan Clutch [message #61578 is a reply to message #61560] |
Sun, 25 October 2009 13:05 |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
Karma: 0
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Senior Member |
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Roger;
I see I am not totally alone in my finding that a Light Duty fan burns
less fuel. That a Heavy Duty fan is close coupled tighter that I found
in my research.
I wonder if you actually have exhaust gas temperatures to indicate the
difference in the cylinder while using a 185 or 195* thermostat.
After working with 427 and 454 GM gravel trucks that burned valves on
long hard pulls, we installed twin EGT gauges and put a red line on them
for the drivers. This solved the problem of every time we had a new
driver, we had burned valves and/or burned pistons. The first attempt
at solving the problem was to lower the thermostat temperatures. This
had no effect on burning valves as it only controls the low engine
temperature. It also had very little effect on lowering the EGT when
the engine was not at WOT. I was always under the impression that EGT
and cylinder temperature is a function of compression ratio and water
temperature has very little effect on it. If water temperature was able
to control cylinder temperature, we could all increase our compression
ratio and just change thermostats to get away from ping. Conversely we
can increase our compression ratio one full point if we switch to
aluminum heads, as they can transfer the heat to the water faster and
eliminate the hot spots that appear in cast heads. Changing the water
temperature does not change the rate of heat transfer. Changing the
material does. I guess what I would like to know is does changing the
water temperature 10* change the temperature of the fuel burn, 20*, 50*
or 100*?
What is the correlation between thermostat temperature, EGT and cylinder
temperature? I only know the correlation between CHT AND EGT on
aircooled aircraft engines and they are very linear. I have been not
been able to observe the difference between water temperature and CHT.
Some people mistakingly believe that a 185*F thermostat will cause
moisture to accumulate in the oil. As the oil temperature in a
naturally aspirated engine is at least 50* hotter than the water
temperature due oil picking up this heat from the bottom of the piston,
this is clearly nonsense. With a turbocharger this oil temperature is
at least 100* hotter.
Thank you for the information;
Gordon
Roger P. Gleason wrote:
>
> Having read the message link I think Tin Gerbil provided a very good
> description as to the differences in the fan clutches. The only thing
> I might add to his input is that the 65% vs. the 95% stands for the
> decoupling when the temperature of the thermostat in the clutch is
> below the engagement temperature. This explains why the standard
> clutch is less noisy when it is satisfied. On the other hand, the 95%
> clutch only slows down 5% between being satisfied and to hot. Most
> probably would not be able to notice a difference in the noise level.
>
>
> This also explains why GM chose the 65% clutch since gas mileage was
> a major issue at the time. This is a rather large fan and the larger
> the fan the more horsepower it takes to move the fan. All that
> translates to is lower gas mileage. As long as the radiator system is
> rejecting the heat of the engine it is doing its job any additional
> heat rejection simply closes the engine thermostat retaining the
> water in the engine longer.
>
> Now for a question, several have lowered their engine thermostats
> from the recommended 195 degree to 185 degrees, what is the purpose
> of this? The newer gasoline’s are formulate where it takes
> higher temperatures to burn them completely some of the newer engines
> are using as high as 210 degree thermostats to accomplish a complete
> burn. Engines I have seen torn down with too low of thermostat leave
> unburned deposits in the heads leading to catastrophic failures.
>
> _______________________________________________ GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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| Re: [GMCnet] "six-speed" transmission [message #61583 is a reply to message #61570] |
Sun, 25 October 2009 13:39 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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On Oct 25, 2009, at 11:02 AM, Gary Casey wrote:
> Emery,
> I wish I had some of my old converter data, but I can't find
> anything on variable pitch units. In one position they increase the
> stall speed and stall torque ratio (useful for backing up a hill).
> That has a byproduct of reducing the load on the engine at idle,
> which can be an advantage with a carburetor(easier to get a smooth,
> no-stall idle). Then the other pitch extends the torque
> multiplication out further in the speed range at the price of a
> lower stall torque ratio. Unfortunately, that reduces the
> efficiency as well. So, at 25 to 35 mph up a grade do you want to
> run full throttle at 90% efficiency with a torque ratio of 1.1, or
> run part throttle at a slightly higher engine speed at a torque
> ratio of 1.48(second gear) and 97% efficiency? At the higher
> efficiency the engine will have to put out less torque to do the
> same work. The converter characteristic in that mode is very
> similar to modern cars with converter clutches. Quite often they will
> be programmed to disconnect the converter clutch going up a hill to
> give a perceived performance increase, when most of the extra engine
> power is just going into heat. My car has a throttle-by-wire system
> and I swear they program the throttle to open when the converter
> clutch is disengaged, to make you think you are getting something
> for nothing. No free lunch, I'm afraid.
> Gary
>
>
I never said that there was a free lunch. Unless one has one of these
on their GMC they usually really don't understand the benefit. In
fact, the torque converter begins to generate a lot of heat and you
can watch the tranny temp gauge start to climb so it should be watched
closely so you don't overheat the transmission.
However you get about 300 or so more RPM in Drive which can keep your
speed up going up a grade. The Roe electronic controller that I use
with my switch pitch turns it off in about 30 seconds. I then look at
my temperature gauge and sometimes move the switch to the override
position if the temperature is not too high so that I can maintain
speed to the top of the grade. However, if it is a long grade and my
speed starts to drop off I turn the switch pitch off and downshift to
second on the transmission.
Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] Fan Clutch [message #61612 is a reply to message #61580] |
Sun, 25 October 2009 17:38 |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
Karma: 0
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Senior Member |
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Emery Stora wrote:
Another potential problem with running too low an engine temperature
> is that any condensation in the engine block must be evaporated by
> the heat of the engine to prevent the water from floating around in
> the oil pan and being picked up by the oil pump and getting into the
> bearings, etc. Water is not a good lubricant. It also will rust
> parts in the engine block.
What water boils off significantly faster at 195* than at 185*? What we
need to pay attention to is the oil temperature, which on the bottom of
the pistons, is at least 50* hotter than the water temperature. We are
looking at 235* VS 245*, both of which will take care of any
condensation. I guess it is conceivable that if one is using their GMC
as a grocery getter and only going 10 blocks to the store, with ambient
air temperature of 0*F, the build up of condensation could occur with
either a 185* or 195* thermostat, THAT NEVER OPENED? If the engine
water temperature never got over 150* condensation will build up. This
was a damaging factor with a propane powered 1978 GMC Suburban grocery
getter using a 160* thermostat. The oil was always clean so I seldom
changed it. The acid built up and ate the main bearings. Luckily it
burned a valve before the crank went. This is when I went back to using
Litmus paper on dipsticks of propane powered vehicle and on engines with
FRANZ oil filters that keep the oil clean for 25,000 miles.
With normal use of a GMC, the entire idea of water rusting an engine
because of a 185* thermostat is just a little silly. Yes, I also
realize no one ever said such a thing. Just broad meaningless, mixed up
statements as in "too low", "higher temperatures", "high temperature
thermostats",etc. It is very hard to understand if you are speaking of
water temperature or oil temperature? You seem to use them
interchangeably?
I have drained the oil from engines which have sat abandoned, unused for
20+ years. There was no sign of water in the oil pan. There was fly
rust on the crankshafts, in the blocks and rust on the valve trains. No
sign of rust in the rings, bearings or the wrist pins. I currently have
a 1979 Moto-Ski snowmobile with 300 original miles on it that was
abandoned in 1980. I'm now very anxious to open it up to see what it
looks like inside. The blackberry vines were 8' high over it and have
grown into the seat. I will look very carefully for water collected in
the dry sump of this 2 cycle engine. There is also a 1979 Honda CBX
1000 (13,000 miles) abandoned in 1980 and a 1984 Honda 450 (1200 miles)
abandoned in 1985. The CBX is seized but the 450 runs well after I
cleaned the carbs and fuel tank. Too many opportunities!
Gordon "From the Cold Damp North, 185* thermostat, with no sign of rust
in the valve covers or water in the oil"
> On Oct 25, 2009, at 12:05 PM, The Tin Gerbil, Ad Nauseum wrote:
>>
>> Some people mistakingly believe that a 185*F thermostat will cause
>> moisture to accumulate in the oil.
>
> Strange, but I have never heard anyone say that.
> What I and others have said was that a 195 deg temperature will take
> the moisture out of an engine quicker than 185 deg.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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