Is there any advantage, esp. in a rear-engine car, in using a NASCAR style radiator/oil cooler combination?
Thanks
Thanks
Combined rad/oil cooler
- Thread starter toy264
- Start date
I have never fitted a cooler with hoses that long.
Would you get a pressure drop over that distance.?
Jim
Would you get a pressure drop over that distance.?
Jim
Lynn Larsen
Lynn Larsen
Jim C,
Undoubtedly, which is, I am sure, why Bill put the emphasis on the -12 hoses at a minimum. Personally, I don't think the hassle of the extra plumbing really buys you anything though.
Lynn
Undoubtedly, which is, I am sure, why Bill put the emphasis on the -12 hoses at a minimum. Personally, I don't think the hassle of the extra plumbing really buys you anything though.
Lynn
Might not be a problem - porsche 911's rely on oil as the sole method of liquid cooling and the external oil cooler is located at the opposite end of the car. Incidentally, the long runs of the lines are expected to provide a significant amount of the cooling. The difference is that the lines are brass. There is also a thermostat plumbed into the system so that the cooler doesn't start to operate until about 190 degrees. I'm not aware of any pressure problems with such a system (the cooler is plumbed in on the low pressure/return side of the system) but perhaps it's somehow different for SBF...
One common oil cooler that is used as an auxiliary cooler by the air cooled crowd is the Mazda RX-7 aluminum cooler - very nicely made and highly efficient.
One common oil cooler that is used as an auxiliary cooler by the air cooled crowd is the Mazda RX-7 aluminum cooler - very nicely made and highly efficient.
The 911 is a dry sump system too dont forget...
toy264 said:
John , Only in that it would add weight to the front end. In this day & age I would suggest a water/oil heat exchanger mounted in the bottom coolant line close to the front of the motor would be the best solution. The extra cost of this unit would be largely offset by the reduced amount of hose etc required to fit in this area. This location would also keep it away from damage in the event of an off course excursion which always seem to find conventional type oil coolers.
Jac Mac
There is another advantage of using an water/oil cooler - The engine coolant will help bring the engine oil up to temperature faster which will allow it (oil) to flow more freely and will also reduce the hp requirement to drive the oil pump.
These types of oil coolers are extremely efficient - much moreso than typical air/oil coolers..
These types of oil coolers are extremely efficient - much moreso than typical air/oil coolers..
Brilliant! Shorter lines, and oil/water transfer has got to be more efficient than oil/air. I might squeeze one in next to the accusump. I wonder if I ought to consider that for the transaxle oil cooling as well?jac mac said:
John, Randy,
A couple of seasons back after two near disasters as a result of conventional oil cooler failures I built a oil /water exchanger from scratch. This unit had the added benefit of being able to be dismantled completely for cleaning etc and was a lot more compact than those shown in the above post. Smaller units could be built for your T/A. The only commercially available unit's similar in size that I have seen are Laminova & Aeroquip. In the unit I made the Bottom Coolant pipe was only exposed to the exchanger element for 12" x 1.5" dia ( Simple plain bore- no fin's etc ) Temp drop of oil was approx 45 deg F.
Jac Mac
A couple of seasons back after two near disasters as a result of conventional oil cooler failures I built a oil /water exchanger from scratch. This unit had the added benefit of being able to be dismantled completely for cleaning etc and was a lot more compact than those shown in the above post. Smaller units could be built for your T/A. The only commercially available unit's similar in size that I have seen are Laminova & Aeroquip. In the unit I made the Bottom Coolant pipe was only exposed to the exchanger element for 12" x 1.5" dia ( Simple plain bore- no fin's etc ) Temp drop of oil was approx 45 deg F.
Jac Mac
toy264 said:
I've been mulling over this concept for a week or so...... Sounds good in theory, but......
Ultimately you still have to get rid of the extra heat that is going into the coolant water. In a GT40, radiator size is somewhat limited up front. Is an existing radiator going to be capable of handling the extra heat dissapation now demanded of it? Or will the radiator need to be upgraded/enlarged? Possibly not an easy task?
I seem to remember reading once that 50% of the engine cooling is provided by the oil. That strikes me as quite a high figure, but if it's right that would then mean that the radiator would be required to dissipate twice as much heat. However I am a little sceptical of that 50% figure.
One benefit of running a water/oil exchanger is that it would totally free up the side scoops for ducting to the rear brakes, eliminating the drag of snorkels. Too bad, I think the snorkels look horny, but function over form any day!
Anyone care to comment?
Cheers
Last edited:
Jac Mac, you're obviously trying to buy time before coming up with the reasoned and knowledgable technical comments that we all come to expect from you.
Or maybe you've just been at those tomato plants again? boomsmile
I wait with baited breath.
Cheers
Or maybe you've just been at those tomato plants again? boomsmile
I wait with baited breath.
Cheers
Still waiting.....
Can anyone confirm the approx % of engine cooling that is achieved by the oil on something like an SBF ?
Has anyone run a water/oil heat exchanger on a GT40 and what effect did it have on engine water temp? Did you need to upsize the radiator?
Failing that has anyone thought about doing it but discarded the idea? And why?
Thanks
Can anyone confirm the approx % of engine cooling that is achieved by the oil on something like an SBF ?
Has anyone run a water/oil heat exchanger on a GT40 and what effect did it have on engine water temp? Did you need to upsize the radiator?
Failing that has anyone thought about doing it but discarded the idea? And why?
Thanks
Lynn Larsen
Lynn Larsen
I'll jump in here with an opinion, just an opinion.
Why an oil cooler? IMHO, an oil cooler is employed to maintain the oil at a specified temperature (or range of temps.) And one may ask how this specified temperature is determined. It is determined by the clearances set in the bearings and the forces that the oil film must be able to withstand while keeping the two metal surfaces from coming into contact. Of course, this is a function of the viscosity of the oil and how that viscosity changes with temperature variations as well. The fact that a certain amount of heat will be moved out of the engine is a side effect. Bottom line, if the overall temperature of the engine is maintained by the coolant system such that the oil temperature keeps the viscosity of the oil in the proper range to handle the forces seen in the bearing gaps from the weight of the rotating assembly and the rpms that it rotates at, an oil cooler isn't even needed. With the advances in multi-viscosity oils, excepting the most extreme race conditions (or idling in traffic with the A/C running full blast
, this could very well be true for the vast majority of us.
So, if the oil cooler is used to maintain proper oil viscosity, that means the radiator/coolant system is used to maintain the overall temperature of the engine. But why do we do this? The commercials on TV tell us heat is the enemy of the engine, right? Well the fact of the matter is that an engine runs more efficiently at higher temperatures than we normally run, and only the heats effect on the density of air in the induction system is seen as a negative to the efficiency. Air cooled engines are more efficient than liquid cooled engines, BUT they are very difficult to maintain consistent cylinder/head temperatures in. When setting up a system (especially a mass produced and maintained system), consistency is a very important quality. Therefore, we have almost exclusively liquid cooled engines today that are very good at keeping cylinder/head temperatures consistent. So now that the decision has been made for liquid cooling, the characteristics of the coolant become the major factor in determining what the temperature of the overall system needs to be. At this point, the mechanical systems are then designed to run within those ranges, as well, putting even more emphasis on the importance of maintaining nominal engine temperatures.
So where does that leave us when setting up our cars. First we try to design the cooling system such that it can move enough heat at the extremes of the conditions it will run in to maintain the coolant system in its proper range. This means an excess capacity during most of its operation, so we put a thermostat in the system to "choke" it down in order to maintain as high a heat as possible without going over. If oil temperatures at the extremes jeopardize the proper oil viscosity, then an oil cooler should be employed. But this line of reasoning would dictate that a thermostat also be used to regulate that cooling system. Having oil with too high a viscosity for the bearing tolerances can be almost as bad as too low a viscosity; again, an oil thermostat seems the prudent thing to do.
At this point, IMHO, the KISS principal kicks in: what is the simplest, least problematic method to maintain the nominal temperature ranges. Only when a system that is the simplest is no longer sufficient to do the job, should a system that is more complex and/or more prone to damage or breakdown be considered. (Or, when it solves a logistical or packaging issue that the simple solution cannot solve.) I guess that is why I like Keith's signature line so much: "If it ain't broke, fix it until it is!"
Why an oil cooler? IMHO, an oil cooler is employed to maintain the oil at a specified temperature (or range of temps.) And one may ask how this specified temperature is determined. It is determined by the clearances set in the bearings and the forces that the oil film must be able to withstand while keeping the two metal surfaces from coming into contact. Of course, this is a function of the viscosity of the oil and how that viscosity changes with temperature variations as well. The fact that a certain amount of heat will be moved out of the engine is a side effect. Bottom line, if the overall temperature of the engine is maintained by the coolant system such that the oil temperature keeps the viscosity of the oil in the proper range to handle the forces seen in the bearing gaps from the weight of the rotating assembly and the rpms that it rotates at, an oil cooler isn't even needed. With the advances in multi-viscosity oils, excepting the most extreme race conditions (or idling in traffic with the A/C running full blast
, this could very well be true for the vast majority of us.So, if the oil cooler is used to maintain proper oil viscosity, that means the radiator/coolant system is used to maintain the overall temperature of the engine. But why do we do this? The commercials on TV tell us heat is the enemy of the engine, right? Well the fact of the matter is that an engine runs more efficiently at higher temperatures than we normally run, and only the heats effect on the density of air in the induction system is seen as a negative to the efficiency. Air cooled engines are more efficient than liquid cooled engines, BUT they are very difficult to maintain consistent cylinder/head temperatures in. When setting up a system (especially a mass produced and maintained system), consistency is a very important quality. Therefore, we have almost exclusively liquid cooled engines today that are very good at keeping cylinder/head temperatures consistent. So now that the decision has been made for liquid cooling, the characteristics of the coolant become the major factor in determining what the temperature of the overall system needs to be. At this point, the mechanical systems are then designed to run within those ranges, as well, putting even more emphasis on the importance of maintaining nominal engine temperatures.
So where does that leave us when setting up our cars. First we try to design the cooling system such that it can move enough heat at the extremes of the conditions it will run in to maintain the coolant system in its proper range. This means an excess capacity during most of its operation, so we put a thermostat in the system to "choke" it down in order to maintain as high a heat as possible without going over. If oil temperatures at the extremes jeopardize the proper oil viscosity, then an oil cooler should be employed. But this line of reasoning would dictate that a thermostat also be used to regulate that cooling system. Having oil with too high a viscosity for the bearing tolerances can be almost as bad as too low a viscosity; again, an oil thermostat seems the prudent thing to do.
At this point, IMHO, the KISS principal kicks in: what is the simplest, least problematic method to maintain the nominal temperature ranges. Only when a system that is the simplest is no longer sufficient to do the job, should a system that is more complex and/or more prone to damage or breakdown be considered. (Or, when it solves a logistical or packaging issue that the simple solution cannot solve.) I guess that is why I like Keith's signature line so much: "If it ain't broke, fix it until it is!"
Lynn-
Thanks for a very considered reply. From your analysis, I infer that the reason for using an oil cooler are obviouslyy more involved than just "keeping it from getting too hot", and the goal would be to keep the viscosity in the nominal range.
Surely by now there is a huge amount of both theoretical and practical knowledge on the subject, and I wonder if there is a consensus among the formula, NASCAR, and SCCA teams on the most effective way to meet that goal? Or perhaps it is governed more by factors like race distances and cubic $ available.
Off the top of my head, I would assume that a heat exchanger in the water line would keep the oil at something close to the engine temp, so a thermostat in the oil circuit wouldn't be necessary, but that's just a WAG.
On another thread, someone suggested a thermostat in the transaxle cooling circuit, and I assume the same considerations would apply to that application as well. Any thoughts on that? Or is this the wrong forum:shrug:
Thanks for a very considered reply. From your analysis, I infer that the reason for using an oil cooler are obviouslyy more involved than just "keeping it from getting too hot", and the goal would be to keep the viscosity in the nominal range.
Surely by now there is a huge amount of both theoretical and practical knowledge on the subject, and I wonder if there is a consensus among the formula, NASCAR, and SCCA teams on the most effective way to meet that goal? Or perhaps it is governed more by factors like race distances and cubic $ available.
Off the top of my head, I would assume that a heat exchanger in the water line would keep the oil at something close to the engine temp, so a thermostat in the oil circuit wouldn't be necessary, but that's just a WAG.
On another thread, someone suggested a thermostat in the transaxle cooling circuit, and I assume the same considerations would apply to that application as well. Any thoughts on that? Or is this the wrong forum:shrug:
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