Fan of a fan
07-17-2018, 01:48 PM
#16
Rennlist Member
Stock US 16V's engine don't go past 6,000rpm (don't make any additional power much past 5,500). These bottom ends are capable of much, much more. Point is, these engines are so over developed and under powered, a bone stock unit is not going to benefit from running a bit cooler, especially on the street.
The idea of running an engine cooler to make more power absolutely has merit, but you are not going to see such gains with a bone stock US 16V car. You also have to remember these are fuel injected, which means there is a temp sensor dictating the fuel usage. If you run the engine cold enough to fall into a richer area of that sensor, your car will never run with proper air / fuels unless you adjust things.
The cooling system on these cars is very, very efficient and oversized. No need to reinvent the wheel unless you are also planning some other big modifications to increase power. The stock belt driven fan is just as capable of keeping temps under control as the later electric fans and the cooling system is the same capacity as later cars making 100+ more HP.
Do what you want, doesn't really matter to us. Most of us respond to such threads for the benefit of others following along at home who see such threads and start to ponder if they too should be trying to increase the cooling efficiency of their cars.
If a slow moving car is overheating, the fan is failing, the radiator is clogged, impeller on the pump loose etc......something is preventing or not moving enough air through the radiator or coolant flow compromised.
Fix the problem and you'll be fine. A stock 16V US 928 sitting in the Sahara Desert will not overheat at idle if all systems are working as the factory intended.
The idea of running an engine cooler to make more power absolutely has merit, but you are not going to see such gains with a bone stock US 16V car. You also have to remember these are fuel injected, which means there is a temp sensor dictating the fuel usage. If you run the engine cold enough to fall into a richer area of that sensor, your car will never run with proper air / fuels unless you adjust things.
The cooling system on these cars is very, very efficient and oversized. No need to reinvent the wheel unless you are also planning some other big modifications to increase power. The stock belt driven fan is just as capable of keeping temps under control as the later electric fans and the cooling system is the same capacity as later cars making 100+ more HP.
Do what you want, doesn't really matter to us. Most of us respond to such threads for the benefit of others following along at home who see such threads and start to ponder if they too should be trying to increase the cooling efficiency of their cars.
If a slow moving car is overheating, the fan is failing, the radiator is clogged, impeller on the pump loose etc......something is preventing or not moving enough air through the radiator or coolant flow compromised.
Fix the problem and you'll be fine. A stock 16V US 928 sitting in the Sahara Desert will not overheat at idle if all systems are working as the factory intended.
"be trying to increase the cooling efficiency of their cars."
I don't think this changes the efficiency, just _maybe_ and doubtful, funs it cooler, which has no benefit. A distant benefit to leaving as is, is oil temps. They -can- be too low...but hard to do with this. Just part of the "I can make it better!" concept.
Thermostat gunna' thermostat...
And any thread...this..
Idling in the sahara?
It was 49 degrees in this photo. So...
Last edited by Speedtoys; 07-17-2018 at 02:12 PM.
07-17-2018, 02:52 PM
#18
Burning Brakes
Thermo-safety factor, good idea. more considerations....
Dont rely on the dash gauge, they are not ideal for getting an actual sense of what is going on temp wise. To know for sure install a digital gauge.
Make sure your fan clutch is good and your fluid is topped up. Running the fan locked out will be noisy and reduce efficiency.
Make sure you have the lower under tray to prevent hot air re-circulation.
Perhaps upgrade the electric pusher fan to a higher CFM unit. A modern newer fan should, quieter, use less current and move more air.
Dont rely on the dash gauge, they are not ideal for getting an actual sense of what is going on temp wise. To know for sure install a digital gauge.
Make sure your fan clutch is good and your fluid is topped up. Running the fan locked out will be noisy and reduce efficiency.
Make sure you have the lower under tray to prevent hot air re-circulation.
Perhaps upgrade the electric pusher fan to a higher CFM unit. A modern newer fan should, quieter, use less current and move more air.
07-17-2018, 02:56 PM
#19
Rennlist Member
With a good fluid clutch, no elec fan will move more air that it will. They'll just be in the way.
No need to install a digital unit, just get a temp gun, and validate proper operation, calibrate that to what you see on YOUR gauge, and never suggest that someone else's should look like yours.
"thermal safety factor"
There is no such thing, that argument would require the existence of a lack of cooling, which means something is broken.
No need to install a digital unit, just get a temp gun, and validate proper operation, calibrate that to what you see on YOUR gauge, and never suggest that someone else's should look like yours.
"thermal safety factor"
There is no such thing, that argument would require the existence of a lack of cooling, which means something is broken.
07-17-2018, 03:39 PM
#20
Rennlist Member
Thread Starter
Boy, some of you guys go beyond the "benefit to others" and tend to seem to want a guy to feel as though he has his head up his own ***. Ideas like "thermal safety factor" goes from "I agree" to "there is no such thing".
If a mechanism is designed to survive a 290 degree temperature, but is designed to run at 190 degrees, that is the thermal safety factor. Very similar to elastic limits, yield strength, and ultimate strengths when designing a structure (but what do I know?).
I figured that since the car does have electronically controlled fuel injection, running cooler would be accounted for and would keep oil temperatures down, among other things. Theory is fine, but actual real world circumstances dictate your day. I would not assume that everyones cars are functionally as they were the day they came off the assembly line. For those that might glean a solution or a bit of insight into their concerns, this is for you.
Smart *** responses are for those that have entirely nothing else to do.
If a mechanism is designed to survive a 290 degree temperature, but is designed to run at 190 degrees, that is the thermal safety factor. Very similar to elastic limits, yield strength, and ultimate strengths when designing a structure (but what do I know?).
I figured that since the car does have electronically controlled fuel injection, running cooler would be accounted for and would keep oil temperatures down, among other things. Theory is fine, but actual real world circumstances dictate your day. I would not assume that everyones cars are functionally as they were the day they came off the assembly line. For those that might glean a solution or a bit of insight into their concerns, this is for you.
Smart *** responses are for those that have entirely nothing else to do.
07-17-2018, 05:35 PM
#21
Boy, some of you guys go beyond the "benefit to others" and tend to seem to want a guy to feel as though he has his head up his own ***. Ideas like "thermal safety factor" goes from "I agree" to "there is no such thing".
If a mechanism is designed to survive a 290 degree temperature, but is designed to run at 190 degrees, that is the thermal safety factor. Very similar to elastic limits, yield strength, and ultimate strengths when designing a structure (but what do I know?).
I figured that since the car does have electronically controlled fuel injection, running cooler would be accounted for and would keep oil temperatures down, among other things. Theory is fine, but actual real world circumstances dictate your day. I would not assume that everyones cars are functionally as they were the day they came off the assembly line. For those that might glean a solution or a bit of insight into their concerns, this is for you.
Smart *** responses are for those that have entirely nothing else to do.
If a mechanism is designed to survive a 290 degree temperature, but is designed to run at 190 degrees, that is the thermal safety factor. Very similar to elastic limits, yield strength, and ultimate strengths when designing a structure (but what do I know?).
I figured that since the car does have electronically controlled fuel injection, running cooler would be accounted for and would keep oil temperatures down, among other things. Theory is fine, but actual real world circumstances dictate your day. I would not assume that everyones cars are functionally as they were the day they came off the assembly line. For those that might glean a solution or a bit of insight into their concerns, this is for you.
Smart *** responses are for those that have entirely nothing else to do.
Get your car running the way it should be from the factory and quit worrying about things people were paid 40 years ago to figure out. Might as well toss on a low pressure coolant cap to keep your radiator from having a leak.
07-17-2018, 06:29 PM
#22
Rennlist Member
Boy, some of you guys go beyond the "benefit to others" and tend to seem to want a guy to feel as though he has his head up his own ***. Ideas like "thermal safety factor" goes from "I agree" to "there is no such thing".
If a mechanism is designed to survive a 290 degree temperature, but is designed to run at 190 degrees, that is the thermal safety factor. Very similar to elastic limits, yield strength, and ultimate strengths when designing a structure (but what do I know?).
I figured that since the car does have electronically controlled fuel injection, running cooler would be accounted for and would keep oil temperatures down, among other things. Theory is fine, but actual real world circumstances dictate your day. I would not assume that everyones cars are functionally as they were the day they came off the assembly line. For those that might glean a solution or a bit of insight into their concerns, this is for you.
Smart *** responses are for those that have entirely nothing else to do.
If a mechanism is designed to survive a 290 degree temperature, but is designed to run at 190 degrees, that is the thermal safety factor. Very similar to elastic limits, yield strength, and ultimate strengths when designing a structure (but what do I know?).
I figured that since the car does have electronically controlled fuel injection, running cooler would be accounted for and would keep oil temperatures down, among other things. Theory is fine, but actual real world circumstances dictate your day. I would not assume that everyones cars are functionally as they were the day they came off the assembly line. For those that might glean a solution or a bit of insight into their concerns, this is for you.
Smart *** responses are for those that have entirely nothing else to do.
"Smart *** responses are for those that have entirely nothing else to do"
Maybe our goal is to help you how to get your car "functionally as it was the day they came off the assembly line".
Dumb example...nobody cares what one person with a partial understanding of how a thing works, if they 'make it better' on a car where it has zero brand significant value.
But here..when many of us know what its like to "De Previous-Owner" a nice/savable car and bring it back to its unique brand significance again...we show it different ways that we care enough to help correct the initial misunderstanding of how a thing works. And you have a nice car.
07-17-2018, 10:46 PM
#23
Rennlist Member
Hi Walt,
My car is heavily modified, but it sounds like yours is closer to stock. I think the best way to achieve safe, efficient cooling would be to make sure your stock cooling components are up to original specs. The fan clutch needs to work properly, the radiator must be clear, the thermostat correct and working properly, and the water pump as new. If some of these are sub-par, you may be able to mask the problem by some means, but I don't think you would want to do that. The fuel injection is calibrated to normal running temp, as achieved by the standard thermostat. Below that temp, it will think you need cold enrichment until you come up to temp and you will be running rich for no good reason. I think the original system, when working perfectly has a thermal safety factor built in, as evidenced by the extreme climate testing of the original car. That safety factor will decline with age and wear and tear, but it can be restored.
Good luck, and I don't really think anyone is trying to be a true smartass, certainly not me,
Dave
My car is heavily modified, but it sounds like yours is closer to stock. I think the best way to achieve safe, efficient cooling would be to make sure your stock cooling components are up to original specs. The fan clutch needs to work properly, the radiator must be clear, the thermostat correct and working properly, and the water pump as new. If some of these are sub-par, you may be able to mask the problem by some means, but I don't think you would want to do that. The fuel injection is calibrated to normal running temp, as achieved by the standard thermostat. Below that temp, it will think you need cold enrichment until you come up to temp and you will be running rich for no good reason. I think the original system, when working perfectly has a thermal safety factor built in, as evidenced by the extreme climate testing of the original car. That safety factor will decline with age and wear and tear, but it can be restored.
Good luck, and I don't really think anyone is trying to be a true smartass, certainly not me,
Dave
07-18-2018, 11:27 AM
#26
Rennlist Member
Thread Starter
I dont doubt that some of you guys have more to share than me when it comes to a 928, but I have gotten smart *** responses on other posts from some of the same posters to this thread. The responses serve no constructive purpose and for someone who does not like small talk, is an annoyance....sorry.
As far as running cooler, I think the perception is that I want the car to run at 99 degrees....Im talking 10-20 degrees cooler (which is the coolant temp, remember)... The engine temp will be higher in the cylinders. I have this car running stronger than I imagined and have been working on it (off and on) since 1997.
Just a thought, but try not to be so tight. We arent driving spacecraft, just well engineered cars.
Oh, and as a last thought on this, the early 928 engineers could not tell the future. They had no idea what would be in the fuels we use today.
As far as running cooler, I think the perception is that I want the car to run at 99 degrees....Im talking 10-20 degrees cooler (which is the coolant temp, remember)... The engine temp will be higher in the cylinders. I have this car running stronger than I imagined and have been working on it (off and on) since 1997.
Just a thought, but try not to be so tight. We arent driving spacecraft, just well engineered cars.
Oh, and as a last thought on this, the early 928 engineers could not tell the future. They had no idea what would be in the fuels we use today.
07-19-2018, 07:19 PM
#28
Nordschleife Master
Its not
overheating as the stat is new and the engine is not exceptionally hot after a ride. The gauge is at the high-middle mark when it previously was just high of middle overall. Could be the sender, but I tend to like my engines running cooler, rather than hotter like modern engines do.
The gauge is notoriously vague.
If your engine is running at the correct temp, you are fine. Trying to run it '10 or 20 degrees cooler' is just going to exercise the thermostat. The engine won't run any cooler than thermostat temp. It's not supposed to.
The fan clutch is supposed to let the fan slip above a certain engine speed (at least that's my understanding). Once it's pulling a certain amount of air, it doesn't need to pull any more. A direct drive fan would just take engine power away at higher rpms.
As was noted, the cooling system in these cars (presuming it works correctly) is more than adequate. I took mine across California's Central Valley at 90+. Stop & go in Sacramento due to construction. No issues. I have been on a 125 mile each way round trip a couple weekends this month. Quite hot. Coolant temp rock solid right where it always is. Oil temps between 190 & 210.
Although some answers are a bit smarmy, everyone is saying this is not necessary. Think about that.
07-19-2018, 11:03 PM
#29
Rennlist Member
according to greg brown, my sensor, wiring, cluster, and gauge work unusually well.
It will visibly cycle between just over the lower white line, and to juuuuust below the upper white line on a hot day stop & go.
And my temp gun (the proper tool for this as mentioned a billion times) confirms that what I see there is matching where the different fan speeds are supposed to be working, and gauge reading.
Looking up the fan controller engagement steps up, and then down was interesting too.
It has taken a while to get used to.
It will visibly cycle between just over the lower white line, and to juuuuust below the upper white line on a hot day stop & go.
And my temp gun (the proper tool for this as mentioned a billion times) confirms that what I see there is matching where the different fan speeds are supposed to be working, and gauge reading.
Looking up the fan controller engagement steps up, and then down was interesting too.
It has taken a while to get used to.
07-20-2018, 01:06 PM
#30
Shameful Thread Killer
Rennlist Member
Rennlist Member
This post pretty much sums up the lack of knowledge on this topic. If you get the engine running cooler, exactly what benefit are you going to get? Nothing except a richer running mixture which causes poor gas mileage, quicker ruination of things like the O2 sensor and cats, for some perceived notion that you might be ahead if you are stuck in traffic in 200 degree heat.
Get your car running the way it should be from the factory and quit worrying about things people were paid 40 years ago to figure out. Might as well toss on a low pressure coolant cap to keep your radiator from having a leak.
Get your car running the way it should be from the factory and quit worrying about things people were paid 40 years ago to figure out. Might as well toss on a low pressure coolant cap to keep your radiator from having a leak.
The good folks in the 996 world suffer from various M96 engine failure modes. Universally, the low temp 160F thermostat is recommended for cars although of course, Porsche cannot recommend it because it results in different NOX generation. It's a matter of operational limits, but keeping the engine cooler, and suffering a slightly higher NOX production is fine with me, which is why I put in the 160F thermostat. Intake air is cooler, and my fuel economy actually improved. I got ~1/2 bar better oil pressure(indicating better viscosity control) in summer, and the AC was more robust. So - notwithstanding the increase in NOX production, I'm a big fan of cooler rather than warmer, and certainly better than overheating. The same results were discovered on the 968 when I changed that from 182F to 160F. It had a black int, and the AC finally could keep up with the outside heat, and I no longer needed to pull over in traffic on a hot day.
The original block of the 928 was designed for thermal stress of ~200HP, or so in the beginning. By the S4, the block dimensions had not changed hardly at all, the cooling system was basically unchanged(maybe a bigger rad, I don't know), the water jacket got larger, but the cylinder walls got smaller, and the passages in the heads were possibly slightly larger, but not significantly. However, there was a 50% increase in HP(heat) with the S4/GT at over 310HP. All that heat needs to be dissipated from the same basic mass as in the 1978 model. I'm sure various things were improved a bit along the way, but it's my opinion that the S4/GT suffers the most from thermal stress, and a full cooling system will still not dissipate the work of the S4/GT engine sufficiently from it's beginnings of around 200HP(I have one data point on this, but it was a very costly data point).
A proper running S4 with a low temp thermo shouldn't run richer, and I'm pretty sure will have similar fuel economy as stock. I know it will have better oil viscosity/pressure, and there will be safer margin from operating, to failure limits. The downside is higher NOX, although I have no idea how much higher, but possibly high enough that it won't pass a state smog check, which is a bummer.