Contemplating FRS for track car

[GrandSport]

Water to oil isn't much use at the track. Your coolant temps are probably going to be around 240-250 so you're not going to get much cooler than that. Furthermore, it doesn't actually add any "net cooling." All you're doing is transferring energy into the coolant, not out of the powertrain system. So unless your coolant cooling system is very overbuilt, it's not going to do much.
Plus, in the event of failure, you don't want your oil AND coolant both overheating together, nor do you want coolant in your oil.

On a street car, water to oil is better because it cools better, costs less, easier packaging, weighs less and even warms up the oil faster. They are far more efficient, and the cooling system has plenty of cooling capability left for street driving- it's not stressed. On the track they can't cool oil down to anything below coolant temp. That's fine if coolant is 220 or so (ideal temp for oil, cooler is worse for longevity), but it's not very helpful if your oil is coming in at 300 and coolant is 250 and already stressed itself.

edit: obviously, if your cooling system is "overbuilt" and not stressed, it's a different story. Very few factory cars will run below 250 at the track when driven hard these days. Frontal area on inlets = big aero sacrifices. My grand sport is about the coolest running car I've ever owned, and it hits 240 or so easily. Keep in mind, it has the same cooling as its supercharged +200hp Z06 big brother (which, ironically, has inadequate cooling). It has ducts and scoops everywhere.

[GrandSport]

Originally Posted by GrantedTaken

Funny to think of GM ownership being so costly.

Heh, it's not so much the GM part as it is the Michelin and brembo parts.

Originally Posted by Sleepless

Every water cooled Porsche as far as I know. You don't see them cooking their oil at the track!

The physics works in favor of water-to-oil coolers due to the way higher density of water compared to air.

Porsche is really impressive with their powertrain cooling. They also have ducts and scoops all over. They also have 3 radiators so effectively they overbuild the cooling and put the heat from the oil into the cooling system. Do the RS cars have dedicated coolers?

Originally Posted by kch

stu already pretty much covered it, but i was mostly referring to the delta between oil temp and coolant temp.

and edit: for DD, my air-to-oil OC keeps things around 180 in the summer, and dangerously low in the winter. i usually tie some cardboard over the rad to keep things warmer.

You don't want the engine oil that low. You want it above the boiling point of water or else water in the oil (condensation, etc) will accumulate and never boil off. You want your engine oil around 220. On my truck in Michigan, I added external dedicated trans and engine oil coolers, but I ran them before the in-radiator coolers. This way I got extra cooling but if I over cooled them when I wasn't towing in the winter, the coolant would heat them back up.

[kch]

Originally Posted by GrandSport

You don't want the engine oil that low. You want it above the boiling point of water or else water in the oil (condensation, etc) will accumulate and never boil off. You want your engine oil around 220. On my truck in Michigan, I added external dedicated trans and engine oil coolers, but I ran them before the in-radiator coolers. This way I got extra cooling but if I over cooled them when I wasn't towing in the winter, the coolant would heat them back up.

yeah i know, that's why i block it off for winter. but the temp sensor is post-cooler, so the oil gets warmer than indicated. my UOAs always come back dry.

[CSG Mike]

Originally Posted by Sleepless

Every water cooled Porsche as far as I know. You don't see them cooking their oil at the track!

The physics works in favor of water-to-oil coolers due to the way higher density of water compared to air.

Kind of.

Water can absorb more heat energy, but it means that heat energy eventually also has to be dumped... back into the air via the radiator.

[CSG Mike]

Originally Posted by GrandSport

Water to oil isn't much use at the track. Your coolant temps are probably going to be around 240-250 so you're not going to get much cooler than that. Furthermore, it doesn't actually add any "net cooling." All you're doing is transferring energy into the coolant, not out of the powertrain system. So unless your coolant cooling system is very overbuilt, it's not going to do much.
Plus, in the event of failure, you don't want your oil AND coolant both overheating together, nor do you want coolant in your oil.

On a street car, water to oil is better because it cools better, costs less, easier packaging, weighs less and even warms up the oil faster. They are far more efficient, and the cooling system has plenty of cooling capability left for street driving- it's not stressed. On the track they can't cool oil down to anything below coolant temp. That's fine if coolant is 220 or so (ideal temp for oil, cooler is worse for longevity), but it's not very helpful if your oil is coming in at 300 and coolant is 250 and already stressed itself.

edit: obviously, if your cooling system is "overbuilt" and not stressed, it's a different story. Very few factory cars will run below 250 at the track when driven hard these days. Frontal area on inlets = big aero sacrifices. My grand sport is about the coolest running car I've ever owned, and it hits 240 or so easily. Keep in mind, it has the same cooling as its supercharged +200hp Z06 big brother (which, ironically, has inadequate cooling). It has ducts and scoops everywhere.

You should never see more than 200F (at speed) or so with a NA FRS, even in Texas heat and humidity. If you park a hot car, then you'll see higher.

Vettes run hot; I would not call it a cool running car at all.

The issue with most oil/water coolers for this platform is the lack of exchange area between water and oil. With enough heat exchange, (e.g. a large laminova), the stock radiator is plenty; the car is MASSIVELY overcooled from the factory.

For example, my car (at 360whp) is still on the stock radiator without heat issues (but with a properly developed cooling stack).

[CSG Mike]

Originally Posted by GrandSport

You don't want the engine oil that low. You want it above the boiling point of water or else water in the oil (condensation, etc) will accumulate and never boil off. You want your engine oil around 220. On my truck in Michigan, I added external dedicated trans and engine oil coolers, but I ran them before the in-radiator coolers. This way I got extra cooling but if I over cooled them when I wasn't towing in the winter, the coolant would heat them back up.

The 180 he is quoting is post-cooler. At 180F, at some point in the system, the oil is over 212F.

Additionally, you don't have to be above the boiling point of water to accelerate evaporation. Observe a pot of water on a stove, warming up. Note the increased evaporation (you can see the vapor!) as the water heats up, but before it is boiling. Also remember that with elevation and vacuum (e.g. negative crankcase pressure), you lower the vapor pressure and boiling point of water below (far below) 212F.

160F is enough heat to safely redline; this is the threshold used by virtually every manufacturer that uses a variable temperature based redline (BMW M cars, Lamborghini, Mclaren, AMG, etc.)

[Tristor]

Originally Posted by CSG Mike

160F is enough heat to safely redline; this is the threshold used by virtually every manufacturer that uses a variable temperature based redline (BMW M cars, Lamborghini, Mclaren, AMG, etc.)

I guess this is somewhat off-topic, but I'm curious if you can expand on this. Right now, because I am using an engine oil cooler it takes longer for oil to come up to temperature on the street, especially in cold weather. Typically my process right now is to baby the car, but keep it rolling, until the blue cold engine indicator turns off, then to begin driving normally keeping the RPMs below 5k. Usually coolant temperature rises rapidly at this point until it hits the thermostat open point and then dips, until it levels out around the thermostat open point (192-195F I think). By the time the coolant has leveled out, my oil temp is usually still just around 160F, but I'll maintain keeping RPMs below 5k until oil temp hits its thermostat open point (190F), at which point I will begin using the full rev range.


My observation has been that oil temperature is directly correlated to RPM and time (or RPM over time, I guess). Despite that, I have always been concerned about abnormal/premature engine wear if I were to redline the car before the oil is fully up to temp. I tend to drive well into the redline because my feel of the car is that this engine prefers being pushed into the top end. I make it a point to bring the engine fully up to temperature and give it a few redlines on every trip before parking it (sometimes driving farther and making a loop if necessary, to ensure I am not short-tripping it at low temps).


Given that I'm tracking the car, I am trying to be judicious in how I treat it when it's not on the track to ensure as long of a life as possible before I have to replace the engine (which I assume will eventually happen no matter what). If 160F is warm enough to redline, am I doing more damage by waiting so long before giving it the revs since it holds the oil temp below its effective operating temperature longer? Would it be better to start giving increasing revs as soon as I cross 160F on the oil temperature to get it into operating range as quickly as possible?

[GrandSport]

Originally Posted by CSG Mike

The 180 he is quoting is post-cooler. At 180F, at some point in the system, the oil is over 212F.

Additionally, you don't have to be above the boiling point of water to accelerate evaporation. Observe a pot of water on a stove, warming up. Note the increased evaporation (you can see the vapor!) as the water heats up, but before it is boiling. Also remember that with elevation and vacuum (e.g. negative crankcase pressure), you lower the vapor pressure and boiling point of water below (far below) 212F.

160F is enough heat to safely redline; this is the threshold used by virtually every manufacturer that uses a variable temperature based redline (BMW M cars, Lamborghini, Mclaren, AMG, etc.)

that's different than boiling off water though.

180 to 200 is the typical "ideal" (depending on engine, oil, etc). In the winter I want it on the higher end because there is more condensation going down to -10 degrees than 90 degrees. It also depends on if you're taking long drives or (like I was) short drives from you apartment to class or the grocery store.

[CSG Mike]

Originally Posted by Tristor

I guess this is somewhat off-topic, but I'm curious if you can expand on this. Right now, because I am using an engine oil cooler it takes longer for oil to come up to temperature on the street, especially in cold weather. Typically my process right now is to baby the car, but keep it rolling, until the blue cold engine indicator turns off, then to begin driving normally keeping the RPMs below 5k. Usually coolant temperature rises rapidly at this point until it hits the thermostat open point and then dips, until it levels out around the thermostat open point (192-195F I think). By the time the coolant has leveled out, my oil temp is usually still just around 160F, but I'll maintain keeping RPMs below 5k until oil temp hits its thermostat open point (190F), at which point I will begin using the full rev range.


My observation has been that oil temperature is directly correlated to RPM and time (or RPM over time, I guess). Despite that, I have always been concerned about abnormal/premature engine wear if I were to redline the car before the oil is fully up to temp. I tend to drive well into the redline because my feel of the car is that this engine prefers being pushed into the top end. I make it a point to bring the engine fully up to temperature and give it a few redlines on every trip before parking it (sometimes driving farther and making a loop if necessary, to ensure I am not short-tripping it at low temps).


Given that I'm tracking the car, I am trying to be judicious in how I treat it when it's not on the track to ensure as long of a life as possible before I have to replace the engine (which I assume will eventually happen no matter what). If 160F is warm enough to redline, am I doing more damage by waiting so long before giving it the revs since it holds the oil temp below its effective operating temperature longer? Would it be better to start giving increasing revs as soon as I cross 160F on the oil temperature to get it into operating range as quickly as possible?

You just asked enough question to actually write quite a few technical papers on.

To make it short, you have to balance pressure vs flow. At too low a temp, there's too much resistance to flow, which is why the pressure is high. While the pressure is technically good, the flow is very bad, and the lack of flow can lead to a lack of lubrication at the end of the oil system.

The viscosity difference between 160F and 190F is fairly minimal, whereas the viscosity difference from 70F to 100F is very large. Viscosity is not linear with temperature.

Here's a chart for you, which I think will outline for you why 160F vs 200F is something considered fairly insignificant.



Another graph, "more zoomed in" showing the relative difference in scale vs the big picture graph above.

[CSG Mike]

Originally Posted by GrandSport

that's different than boiling off water though.

180 to 200 is the typical "ideal" (depending on engine, oil, etc). In the winter I want it on the higher end because there is more condensation going down to -10 degrees than 90 degrees. It also depends on if you're taking long drives or (like I was) short drives from you apartment to class or the grocery store.

Even with a 160F oil temperature, you will not accumulate water in your oil unless something is wrong with your engine, due to the reasons stated above in my post.

[Tristor]

Originally Posted by CSG Mike

You just asked enough question to actually write quite a few technical papers on.

Heh, I tend to ask a lot of questions like that. Probably why I spend far too much time reading technical papers. Thanks for your answer and the graphs, that mostly cleared up what I was trying to understand.

[rice_classic]

Originally Posted by CSG Mike

To make it short, you have to balance pressure vs flow. At too low a temp, there's too much resistance to flow, which is why the pressure is high. While the pressure is technically good, the flow is very bad, and the lack of flow can lead to a lack of lubrication at the end of the oil system.

Sorry for butting in Mike I just wanted people know that in a "constant flow machine" like our positive displacement oil pumps, a slightly higher viscosity doesn't exactly equal less flow except for when another factor is involved like the PRV at startup or unintended system or pump leakage.


edit: truncated the post, removed unnecessary blah blah blah.

[GrandSport]

Originally Posted by CSG Mike

Even with a 160F oil temperature, you will not accumulate water in your oil unless something is wrong with your engine, due to the reasons stated above in my post.

I disagree, especially if you're doing short trips.

[Joesurf79]

Originally Posted by rice_classic

Sorry for butting in Mike I just wanted people know that in a "constant flow machine" like our positive displacement oil pumps, a slightly higher viscosity doesn't exactly equal less flow except for when another factor is involved like the PRV at startup or unintended system or pump leakage.


edit: truncated the post, removed unnecessary blah blah blah.

Positive Displacement pumps in fluid service care not about your silly system pressure, they'll produce flow or die trying