[ajm8127]

N54_Fan,

I look forward to seeing your results. I agree that over cooling the ATF is unlikely. Where were you planing on installing the sensor?

Rismo,

It would have been interesting to compare an analysis of the fluid that came out of your trans vs. the fluid that went in.

[N54_Fan]

Originally Posted by ajm8127

N54_Fan,

I look forward to seeing your results. I agree that over cooling the ATF is unlikely. Where were you planing on installing the sensor?

Rismo,

It would have been interesting to compare an analysis of the fluid that came out of your trans vs. the fluid that went in.

The sensor kit I plan to buy has 2 sensors so I figured I would place one after the factory heat exchanger which is before the cooler and then one after the tranny cooler I'm going to install.

[enrita]

Originally Posted by N54_Fan

The sensor kit I plan to buy has 2 sensors so I figured I would place one after the factory heat exchanger which is before the cooler and then one after the tranny cooler I'm going to install.

looking very much forward to your testing results.

[ajm8127]

Originally Posted by N54_Fan

The sensor kit I plan to buy has 2 sensors so I figured I would place one after the factory heat exchanger which is before the cooler and then one after the tranny cooler I'm going to install.

So now I'm confused. I thought the fluid would flow out of the transmission, to the auxiliary cooler, then on to the factor heat exchanger and then back to the transmission.

I thought this routing was optimal because it would cool the ATF before the radiator, preventing the heat from the transmission from being absorbed by the engine coolant, keeping both the ATF and engine coolant cooler.

[N54_Fan]

.

[ajm8127]

Originally Posted by N54_Fan

Well I thought intuitively that would be best too...however, I have also found out that virtually every manufacturer of these coolers recommends AFTER the factory heat exchanger. Apparently this has been tested thorougly before and the conclusion is that AFTER the factory cooler is about 5% more effficient that before. So EVERY manufacturer recommends AFTER factory heat exchanger. Sorry if I didn't make that clear earlier. I found this out in the last few days.

Is that information specific to the BMW N54 platform?

One of the goals of placing the cooler before the exchanger was to minimize the heat transfer to the engine coolant, which triggers component protection as low as 117°C.

If placing the cooler after the stock heat exchanger, you may want to bypass the heat exchanger for racing.

According to the N54 2007 Engine Management PDF, the computer tries to keep the head at 90°C in what BMW calls "map-thermostat mode", which is the highest performance mode of four listed. This means the engine coolant must be at a lower temperature. Placing the ATF cooler before the factory heat exchanger should result in sub 100°C ATF temps as it flows back into the transmission, and it will limit the amount of heat introduced into the engine coolant from the transmission, minimizing the possibility of entering reduced performance modes related to elevated engine coolant.

[N54_Fan]

.

[rismo]

Originally Posted by enrita

as far as i know only BMW - ZF - Alpina can flash the TCU . nobody else can.

I can confirm after contacting almost everybody in the ZF business, that only BMW and Alpina can do it. Even ZF has no direct access to the BMW specific mechatronic software. Only to their own generic software stack.

[ajm8127]

If you are not having a problem with water temperature, then I don't see a reason to put the auxiliary transmission cooler before the stock heat exchanger. I would agree that placing the auxiliary cooler after the stock heat exchanger will result in lower ATF temperatures.

Let us know how everything works out.

[Orb]

If one looks at the problem will see that the limitation of the system is the water inlet temperature and the radiator size. The bases of all thermal problems like this will be about surface area in contact with the fluids.

The transmission is cooled by the radiator as it what rejects the heat to the air. The fluid to fluid AT heat exchanger is just intermediate step to transfer the load to another medium and in this case both ways. If the water inlet temperature at the AT heat exchanger is too high (due to engine load) the AT heat exchanger will have greatly reduced capacity to transfer the heat from the oil into the water. Hence, the transmission oil gets very hot.

Tuned AT/DCT car will at some point overheat under continues high load due the thermal limitation of the radiator. The OEM radiator is actually a really good high end production unit but is very small in size given the thermal load. The radiator can be improved upon and surface area can be increase by 30% in the same packaged size. The coolant run parallel paths for the main and AT coolant flows so any increase in radiator size means an increase in AT cooling abilities unless one wants tune it otherwise.

The technology available now means you should be able to reject about 35-43% more thermal load over the OEM design radiator.

The solution here solves two problems and doesn’t require additional space or other complicated hardware. The idea of solving this problem with another cooler is very much in the box idea and not understating what is needed. It is best to fix problems at the source instead of endless Band-Aids.

If one wants more cooling you can BMW PK 850 watt fan and AT would befit a great deal since the majority of parasitic losses are in gears 1 to 3.

[N54_Fan]

.

[ajm8127]

The amount of heat transfered is directly proportional to the difference in temperature between the water inlet and the atf inlet. If the water temperature is near the atf temperature, not much heat will flow, and the atf will not be cooled.

[N54_Fan]

.

[Orb]

Originally Posted by N54_Fan

Thats what I was understanding as well. So his point is that if the radiator outlet (ATF inlet) is too hot then the ATF will not be cooled much if at all.

Edit the post as I ment the AT heat exchanger water inlet. The relationship for heat transfer is non linear.

[ajm8127]

So what are the options for upgrading the radiator for AT cars? I was thinking simply adding another cooler for the ATF would be more cost effective, albeit less elegant.

[Orb]

Originally Posted by N54_Fan

Thanks Orb. (I always appreciate your engineering expertise) As you know I have the 850W radiator fan and dual oil coolers but do not have the aux radiator of the PPK. Are you suggesting that would be a good addition here? I dont think I understand you completely. I get that the radiator outlet fluid will flow to the inlet of the exchanger to cool ATF. Is it your premise that if the radiator is unable to cool anymore and is "saturated" essentially due to such high heat load then the heat exchnager will also be saturated and unable to cool the ATF further and thus cause high ATF temps? This would mean all the more reason to get the aux ATF cooler and as big as possible. Dont you agree?

If we can get the PWR or other radiator that will fit in OEM spot at a reasonable price I may get that as well.

Thanks

The best bang for the buck is going to be the 850 W fan and now you sorted it out other can do it as well. if we had software upgrade things would running a lot cooler as well.

I am not too sure I would use the aux radiator unless I had more info about the 335is water pump mapping and if the pump is different for the 335i version. The water velocity through the radiator is just above 1.5 m/s which far less than ideal. Adding a parallel path for aux radiator is going to drop the velocity of through the main radiator but it may be okay and maybe you are ahead of the game.

There are several things that need to be considered if one is going to add an AT oil cooler:
1. How much pressure drop does the system introduce? It will have effect on the oil flow rate. This issue should be taken very seriously.
2. Where are you going to put it? If you put in front of the radiator then you just dump the thermal load in the radiator…not smart and defiantly a job shop approach.
3. You need a thermostat control for sure. Over cooling the oil will shorten the life of the transmission and it will not work properly. It is important to bring the transmission up to operating temperature ASAP.
4. I would look a DCT M3 layout as it uses both aux cooler and heat exchanger.
5. Expect a non engineered solution from the majority of the vendors who will try this. The cost is going to be close to 1000.00

PWR does have the materials to make a high performance radiator but there are a lot of extra details to work out and getting the flow right and balanced was a lot of extra work. I know about the details since I designed it myself. You will never see a cheap radiator for this car as you need the best possible materials and design. In short there is no economy version radiator as they will never be made in qualities that justify a good cost reduction.

[boostaholic786]

This might be something a little off topic but I decided it had to do with it to some extent. I cant stand driving the car in D whatsoever. Especially if I'm on the phone just cruising and slow down to make a 10mph turn and the tranny doesnt like to downshift so I feel like I'm putting more load on the transmission since I have to push the throttle down more. I enjoy driving the car in S mode just because it keeps the revs where they should be, well in between 2k-3k rpm's. I also enjoy shifting myself because I came out of an M6 then to an M3 so Iam very use to the paddles on steering wheel and am comfortable using them on a day to day basis or drive the car in S mode most of the time. Does this put any additional strain on the tranny or cause the tranny to get more hot quicker? I would really like to have faith that if i keep it in S mode "most of the time" I feel like it takes the car to the rpm's it needs to go to....say 3k rpm's instead of in D and shifting under 2K rpm's? If I use the paddles more often is it going to shorten the life of the tranny instead of keeping it in D? I just cant stand D whatsoever unless I'm on the highway cruising for a good 25-30 min or more. Just curious at what the communities input is on this as I know I will be guided in the right direction.

[ajm8127]

Orb, you bring up some good points.

If a high quality cooler is used such as a Setrab or Earls (subsidiary of Holley) the pressure drop should be minimized.

I would install the transmission oil to air cooler in front of the driver's front wheel, opposite where the engine oil cooler goes.

The idea of placing the oil cooler before the stock water to oil heat exchanger was to keep the oil from over cooling. Now if you look at the documentation for N54 Engine Management, there is a thermostat built into the stock water to oil cooler. It must limit the water flow through the core if the oil temperature dips too low. Alternatively, there are a number of oil thermostats on the market that will regulate the temperature at 180°F or 82°C. You could use such a thermostat to bypass the air to oil cooler in the event that the oil temperature is too low. this would direct the oil to flow only through the water to oil cooler.

I found this information concerning the M3 DCT:
http://www.m3forum.net/m3forum/showthread.php?t=360259
http://www.bmw.com/com/en/insights/t...rivelogic.html

And here's a diagram

It seems the two heat exchangers run in parallel with the air to oil cooler having a dedicated pump. However, a parallel setup would be difficult to implement on the 335.

Boostaholic,

The more shifting that is done, the more heat will build up and the faster the components will wear out. I don't know the specific differences between DS and D except to say DS mode seems to let the RPMs raise higher before up shifting, and it downshifts sooner when slowing down. For M mode, it all hinges on when and how you choose to shift it.

[N54_Fan]

Originally Posted by ajm8127

Orb, you bring up some good points.

If a high quality cooler is used such as a Setrab or Earls (subsidiary of Holley) the pressure drop should be minimized.

I would install the transmission oil to air cooler in front of the driver's front wheel, opposite where the engine oil cooler goes.

The idea of placing the oil cooler before the stock water to oil heat exchanger was to keep the oil from over cooling. Now if you look at the documentation for N54 Engine Management, there is a thermostat built into the stock water to oil cooler. It must limit the water flow through the core if the oil temperature dips too low. Alternatively, there are a number of oil thermostats on the market that will regulate the temperature at 180°F or 82°C. You could use such a thermostat to bypass the air to oil cooler in the event that the oil temperature is too low. this would direct the oil to flow only through the water to oil cooler.

I found this information concerning the M3 DCT:
http://www.m3forum.net/m3forum/showthread.php?t=360259
http://www.bmw.com/com/en/insights/t...rivelogic.html

And here's a diagram

It seems the two heat exchangers run in parallel with the air to oil cooler having a dedicated pump. However, a parallel setup would be difficult to implement on the 335....

So looking into this further it seems I agree with what you and Orb are saying. The M3 uses a heat exchanger similar to ours and actually uses the same part number of our OEM factory oil cooler for their transmission cooler. It appears that a thermostat allows flow to the aux trans cooler when >203 F. IND distribution sells an M3 transmission cooler upgrade shown here. (MSRP = $1873). I have sourced most of the parts including an appropriate oil pump for much less in my attempt to mimic this M3 design. However, there would be no thermostat in the system. One could easily be added like the Earls Performance sandwich style thermostats that turn on fully at 180 F.

There are 2 things I cant decide how best to remedy:

1) How to get a thermostat to turn on the pump. Obviously we dont want to have the pump running when there is no flow to the cooler. We need to coordinate the pump and thermostat temp. I am sure some of you electrical wizards could figure this out easily. A temp sensor I plan to use has an analog output from 0-5 V so I assume we could use a relay to turn on the pump. The temp sensor output is Celsius temp/ 30 = Voltage output. So 90C is 3 V. It would be nice to use this since it would then be adjustable as desired but I cant figure out how to get the 3 V signal to turn on the pump.

Any ideas?

I do think a pump is needed as most of the Porsche and GTR guys use them and in speaking with the sales rep from IND Dist. they said the stock M3 transmission pump is not sufficient for an aux trans. cooler without one. I suspect our 335 has a similar or even weaker pump.

2) How to plumb this so that the cooler is in series as opposed to being plumbed in parallel. Parallel would bypass some fluid from the aux cooler. Ideally the pump would take over from the stock pump and overcome the resistance from the added transmission lines and cooler. As I understand the thermostats lines are still allowing flow through OEM route even if the thermostat is fully open and allowing flow to the aux cooler. I do NOT believe it completely diverts flow when open.

Any ideas on this?

Also, here is an interesting discussion of how and why its done from a Porsche forum.

http://forums.rennlist.com/rennforum...ler-setup.html

[N54_Fan]

Think I found an appropriate switch.

http://www.setrabusa.com/thermalswitches.html

[N54_Fan]

LOL,...I think I just found out that the Earls thermostats would be able to make it a series plumb and no flow goes back through stock system when thermostat is fully open.

[ajm8127]

That's an ambitious upgrade.

I do not think putting the two pumps inline is a good idea. In the M3 DCT, the air to oil cooler pump is not inline with the main pump. I think some very strange things could happen if the pumps were put inline.

To figure out if pressure drop through the cooler is a big deal or not, we really need to know what the flow rate through the cooling circuit is. Earl's has documentation comparing the pressure drop in three different types of coolers, but it does not tell you which of their coolers they used for the test, although they do say it is of comparable size to the other units tests. Interesting to note is that SAE 10 weight oil was used for the pressure drop test, which is close to if not slightly higher than the viscosity of LG6 ATF at 100°C.

The only way in my mind to add another pump is to not use the stock cooling ports in the transmission because they are in line with the stock pump. You would need to make new holes somewhere in the transmission to accommodate the new pump and air to oil cooler circuit.

If placing the air to oil cooler between the stock exchanger and the transmission (i.e. inline with the stock cooling circuit and stock pump), the inlets to the thermostat would go between the stock heat exchanger and the transmission, with the two other lines in the thermostat going to the oil cooler. In the PDF you posted, imagine the "engine" represents your transmission, and the "oil filter" represents the stock water to oil heat exchanger.

If you used the pump and had a completely different cooling circuit for the air to oil cooler, the temperature switch should go in the transmission oil pan, and this would activate the pump. You would not need the thermostat in this case because no oil wold flow through the cooler unless the temperature switch told the pump to turn on. You would need to put two additional holes somewhere in the transmission, probably in the pan. I would put the supply to the cooler by the temperature switch and the return from the cooler on the other side of the pan. Some sort of metal part (a bulkhead) would have to be fabricated to attach to the transmission pan and allow you to thread the extra lines in. I would not recommend drilling and tapping the plastic pan. As you can see, this solution would be difficult to implement.