Air / Oil cooler Vs. Oil / Coolant cooler?

[fenwick458]

ok so i finally got my oil cooler today, theres a sandwich plate with a thermostat in it and the bolt that came with it is too short to fasten the 150PD heat exchanger and the plate, i called the mocal dealer and they "assumed" that i was going to ditch the heat exchanger?

is there any point retaining the heat exchanger? what heats up faster, coolant or oil? if its oil then i don't see why i can't ditch it but if the coolant warms up first then obviously i'll want to retain it so that the oil is brought up to temp quicker.

they are sending me a longer bolt for free anyway but i just wanted some advice/opinions about the best thing to do.......

thanks

 

[Rub87]

I'd keep the heatexchanger so the oil will get hot sooner especially in winter.. you could also use a smaller type of HX, maybe then the bolt is long enough?

 

[Drivbiwire]

Oil to coolant is superior. Cold oil is the WORST thing you can do to an engine.

Ideally oil temps in the 180-210F range are ideal for the motor. Coolant just so happens to remain within that range.

Coolant to oil heat exchangers also reduce the complexity and require a fraction of the size to perform BETTER than an air to oil cooler.

Air to oil coolers haven't been used in decades on high performance engines for all of the above reasons...Air to Oil is obsolete.

DB

 

[Rub87]

For track or heavy duty use on a modified tdi air to water ain't suffucient, because the water itself will be over 100°C already, and the oil will be also need to remove alot of heat form the pistons..

With an oil to air you can keep the oil at 90° under any load.. but I'd use a thermostatic sandwish plate an a small oil to water HX to heat the oil up sooner..

just my 2c

edit: on the other hand, the audi R8 uses a sexy oil to water cooler, it's mounted at the left hand side behind the carbon insert plate..

 

[fenwick458]

gotcha.

so i'll fit the 150PD heat exchanger on, fit the sandwhich plate inbetween. the plate has a built in thermostat that opens at 80degrees and i have a 10row cooler to mount in the wing where the SMIC was.

 

[mojogoes]

gotcha.

so i'll fit the 150PD heat exchanger on, fit the sandwhich plate inbetween. the plate has a built in thermostat that opens at 80degrees and i have a 10row cooler to mount in the wing where the SMIC was.

Yes this is the way i have it fit.......after reading your first post i thought that you were having problems fitting it to the oe exchanger , if that don;t fit i was going to suggest using the same slimmer exchanger from an older model and then screwing the sandwich to that........(both is the perfect combo!!)

 

[Drivbiwire]

For track or heavy duty use on a modified tdi air to water ain't suffucient, because the water itself will be over 100°C already, and the oil will be also need to remove alot of heat form the pistons..

With an oil to air you can keep the oil at 90° under any load.. but I'd use a thermostatic sandwish plate an a small oil to water HX to heat the oil up sooner..

just my 2c

edit: on the other hand, the audi R8 uses a sexy oil to water cooler, it's mounted at the left hand side behind the carbon insert plate..

A 1000 hp engine uses a similar water to oil heat exchanger, do you really think a little TDI can saturate the original oil cooler? NOT!

Take readings from the OUTLET of the oil cooler going into the engine. Reading oil SUMP temperatures isn't telling you anything other than heat is transferring to the oil then to the sump.

If for some reason your oil is exceeding 220-240F entering the motor, add a larger oil to coolant heat exchanger such as the one from the Audi A6 or V8, this will far and away exceed any amount of heat you can throw at the oil system.

DB

 

[Rub87]

now what if you coolant is already 110°C, talk with the people running a 80° sandwish plate with oil to air and ask about the difference in temp they measured BEFORE the cooler.. I could peg 135°C on track use with a afn with about 150hp.. it had stock afn heat exchanger, offcource the PD150 one etc would keep it down a bit, but still if the water also is quite hot, you'll see not that much of a gain..

 

[mojogoes]

Well put Rub.......its best to have both if you can.

 

[Drivbiwire]

now what if you coolant is already 110°C, talk with the people running a 80° sandwish plate with oil to air and ask about the difference in temp they measured BEFORE the cooler.. I could peg 135°C on track use with a afn with about 150hp.. it had stock afn heat exchanger, offcource the PD150 one etc would keep it down a bit, but still if the water also is quite hot, you'll see not that much of a gain..

The problem is you are measuring the oil temp at the wrong location.

The temperatrures you are seeing are BEFORE the heat exchanger and not the oil temps going into the engine.

Simply drilling and tapping the housing post cooler would be the best place to read your temps. I suspect the oil even under extreme loads will seldom be above 110-120C which is a very good operating range for synthetic oils.

If you are seeing oil temps of 160C+ post heat exchanger (Oil temperature entering the engine) then you would need to consider alternatives to lowering the oil temp.

Again if you are only seeing oil sump temps of 135C your oil is already at optimum temperatures when entering the engine. I suspect that you are only getting a 15-20C rise or increase by the time the oil works thru the engine and removes heat.

You guys are chasing problems that don't exist.

DB

 

[Rub87]

For good full synth oil, 135°c is no problem, but if you use the regular half synth oil, like most VP tdi's do, these temps make the oil go bad in short time, you can smell if the oil has been too hot .. I would want to consider the full synth and a PD150 HX as antother solution yes, especially because I've very limited space in my application..

 

[validius]

DBW, you're incorrect. According my my gauges, at freeway speeds my coolant runs at 190F and my oil runs at 220F. My temp sensor is right AFTER the head exchanger. My oil temps have gotten as high as 240F under hard driving. For a proper synth like im running (Excellium DID) this isnt a huge problem but there is room for improvement. For summer use an oil-air cooler would be great. For a Michigan winter where its guaranteed to be sub zero at least a few days i would keep the oil-coolant system. There are a number of upgraded units you can buy that are OEM. Look into those.

Bottom line: On the track, oil to air cooler is the way to go. On the street, use the oil to water.

 

[Drivbiwire]

DBW, your incorrect. According my my gauges, at freeway speeds my coolant runs at 190F and my oil runs at 220F. My temp sensor is right AFTER the head exchanger. My oil temps have gotten as high as 240F under hard driving. For a proper synth like im running (Excellium DID) this isnt a huge problem but there is room for improvement. For summer use an oil-air cooler would be great. For a Michigan winter where its guaranteed to be sub zero at least a few days i would keep the oil-coolant system. There are a number of upgraded units you can buy that are OEM. Look into those.

240F? And you are worried why? FYI thats a very good operating range for a synthetic oil. If you have another sensor in the sump and subtract the incoming from the sump temp it will give you a good indication of how well the heat exchanger is working.

Again, you guys are chasing problems that don't exist.

This takes us back to the importance of HT/HS which is measured at 150C...302F. This tells you how well the oil can peform (to a certain extent) at the upper 3/4ths of the operating range of the oil that being a maximum of around 400F (Synthetic group IV or Group III).

And FWIW, Unless you are towing a 2500# trailer at 75+ in the mountains (chipped and injectors) your cars aren't anywhere close to running hard! Of course I would only recomend that using a good quality oil (Total, D1 etc).

DB

 

[Keith_J]

Pistons need to be kept cool. Oil is the only way.

Hot oil and a HP diesel is a bad combination. Ever seen a crown melt? Well, the hyper-eutectic Al-Si alloy doens't really melt, it just loses most of its strength. Yes, aluminum LOSES STRENGTH AT TEMPERATURE!!!

Oil has a really crappy specific heat, meaning it is about 1/4 as efficient at removing heat than our friend, water when viscosity, thermal conductivity and density are compared. And this means your oil NEEDS TO BE KEPT BELOW 300 F. Sure, the sump/oil pump may be in the 220 F range but what is the temperature of the piston?

 

[validius]

240F? And you are worried why? FYI thats a very good operating range for a synthetic oil. If you have another sensor in the sump and subtract the incoming from the sump temp it will give you a good indication of how well the heat exchanger is working.

Again, you guys are chasing problems that don't exist.

This takes us back to the importance of HT/HS which is measured at 150C...302F. This tells you how well the oil can peform (to a certain extent) at the upper 3/4ths of the operating range of the oil that being a maximum of around 400F (Synthetic group IV or Group III).

And FWIW, Unless you are towing a 2500# trailer at 75+ in the mountains (chipped and injectors) your cars aren't anywhere close to running hard! Of course I would only recomend that using a good quality oil (Total, D1 etc).

DB

Your right, there is nothing to be worried about, the oil is within the correct range. My point is only that there is room for improvement.

 

[Keith_J]

Just because the sump is at an acceptable temperature does not mean all the oil is at this temperature. If the oil is at 300 F, the coolant is at 190 F, somewhere the oil HAS to be HOTTER than 300 F. And it is a safe bet the temperature is over 400 F.

 

[fenwick458]

still not fitted it, not got a long enough bolt to go through the HX and sandwhich plate!
heres a pic anyway: