Thanks for all of the excellent data! It is so much more useful than speculation or hearsay "from Nissan engineers."

 

Jeff, more good info ... glad to have this knowledge out there in the public domain. Thanks for taking the time, both to collect and interperet the data.

 

Good info and data Jeff.

I think I am going to install a fan on my factory ATF cooler similar to what you did to help bring the temp down during during slow speed high-load situations.

 

i love how much detail you go into everything, even a m205 without even lifting ur rig. when you gonna lift it tho?

 

Amazing! Thanks for the great info.

Every plot showing the AT pan temp shows that it remains the most stable of all the temperatures, surprisingly, even in stop and go traffic. It hardly ever gets over 170 or so. Also clear is that the rad ATF cooler regularly drops the fluid temp by about 20*.

This post makes me really glad I just installed a new radiator and put the ATF cooling back to stock. I did drive for over a year with it bypassed -- definitely time to do the PMF and get some fresh fluid in there.

BTW, good to see you are in NM! I was looking at the plots and suddenly starting recognizing all the street names hahaha. I live in ABQ.

 

No questions, just a comment. Great post and lots of useful information there. Thank you sir!

 

Thanks for the interest and compliments.

I want to remind everyone that the ATF temperatures can rise to dangerous levels in cool weather. The data collected last year in Colorado demonstrated that long uphill grades in too high a gear, even though it is an automatic, can generate heat.

While the “Auto vs. Manual” mudslinging continues, I’d like to remind those with automatics that the broad power band of the VQ40 and the factory programming of the auto controller does allow for excessive converter slippage under some conditions. The computer between the drivers ears needs to override the Nissan programming under these conditions. The shift lever is easy to use to select the appropriate gear to maintain sufficient rpm to minimize heat build up.

From the first installment of this topic, http://www.thenewx.org/forum/showpost.php?p=474945&postcount=35:
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I'm definitely changing the way I drive the X. The engine has so much torque at low rpm that it masks the need to downshift. The auto calibration doesn’t let a lower gear to be selected when it would be easier on the trans and converter. I suspect it is to maximize gas mileage, even if it happens at the expense of trans life. To be far to Nissan engineers, these conditions are more extreme than most owners would subject the X’s and these conditions are outside of the design requirement parameters. It's too bad the trans doesn't have a selectable performance mode for challenging trails and roads.

I think that as long as a gear is selected to keep the engine rpm above 2200, the stock cooling system with both Rad-ATF and Air-ATF coolers working is adequate. Not all of the logs have both cooler data, but those that do show the effectiveness of the Rad-ATF cooler, especially at low speeds. The Air-ATF cooler is providing cooling at lower speeds but nothing like the Rad-ATF cooler. It is worth noting that the ambient temperatures were typically in the 50 - 60F range, not high by any standards. The trail and highway grades are also high and need to be considered when reviewing the data.
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We’re traveling to Ouray, CO, in a few weeks and will be able to collect temperature data with the cooling fan operational. We’re planning on visiting some of the same trails so we should have data to compare.

Cheers,
Jeff

 

We’re traveling to Ouray, CO, in a few weeks and will be able to collect temperature data with the cooling fan operational. We’re planning on visiting some of the same trails so we should have data to compare.

Awesome, can't wait for the trip report (and a look at the comparison).

 

Something I am considering is to reverse the ATF flow between the air and rad coolers. I’d run the ATF through the air cooler first and then the rad cooler. The higher temperature ATF in the air cooler should improve the heat loss and lower the heat load on the engine cooling system. When it would be a wash because the hotter air from the air cooler would be flowing through the radiator is a reasonable question. To swap the hoses requires the NXRocks rad skid to be dropped which is a job. Based on my data there doesn’t appear to be any cooling issues for me that require additional modifications, but it is something I’m thinking about.

I’ll try to answer any questions.

Cheers,
Jeff

Jeff,

I haven't had time yet to examine all of your data (I will), but I wanted to address this first. I wouldn't recommend doing this, as I believe it will lower the overall heat transfer efficiency.

While you will gain some heat transfer in the air / air cooler due to the higher DeltaT, recall that a portion of that heat is then carried into the radiator behind it, lowering the deltaT of the air / coolant.

You would also lower the deltaT between the ATF cooler in the radiator and the coolant, thereby lowering the heat transfer rate at that point of the system.

The engine radiator and cooling system has plenty of design margin in its ability to remove enough heat from the system. Recall that the boiling point of the system pressurized to 14 psi would be around 236F.

 

BTW, with my Bullydog measuring the ATF temperatures, I've observed my highest temps at highway speeds going up long, steep grades, when the transmission has downshifted to 4th and the TC isn't locked. All that slippage and the fluid temps climb. Manually turning on my electric fan (lo speed though) doesn't help in this situation. Then engine coolant temperature doesn't change a bit here though...

 

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gpz, reversing the flow direction makes for an interesting thought experiment for all of the reasons you mention. It’s difficult to predict the outcome because there are so many unknown factors. Regardless, it makes for an interesting discussion.

There isn’t a performance problem that is driving the thought process, just an intellectual interest. If it was easier to get at the hoses I’d probably do the experiment. R&Ring the NXRocks rad skid is too much like work to do it just for the information.

The auxiliary fan has improved the cooling performance of the ATF cooling system enough that I’m satisfied. The fan has sufficient power to move air through the AC condenser and radiator. Even at 50-65mph the fan improves cooling. No question that towing uphill is severe use that stresses the engine and trans cooling systems. A fan is easy to add to the air cooler if trans temperatures are a concern.

Jeff

 

gpz, reversing the flow direction makes for an interesting thought experiment for all of the reasons you mention. It’s difficult to predict the outcome because there are so many unknown factors. Regardless, it makes for an interesting discussion.

Not that difficult to predict. Remember that heat transfer rate, (Qdot), is equal to the mass flow rate (Mdot) X the specific heat of the fluid (Cp) X the difference in temperatures (DeltaT). Its linear, and some of the terms can simply be neglected, e.g. the mass flow rate is the same for both the radiator ATF cooler and the air ATF cooler, and the specific heat is the same since it is all ATF. So it all comes down to the DeltaT.

I'll neglect discusion of the specific heats of the engine coolant and the air, and the differences in surface areas of each heat exchanger. With this in mind, and mindful of the conditions that I previously stated, (that the increased heat exchanged in the air ATF cooler goes into the air that goes into the radiator, etc.), it becomes intuitively obvious for me... but then again, heat transfer is one of my disciplines. The math will support my argument, as would an actual experimental run with your data acquisition system.

 

I probably ought to look into getting a pusher fan like yours. Right now all I've done is tap a power circuit into the electric puller fan behind the radiator so I can manually initiate the low speed via a switch on my dash (all automatic functions still work). It helps at slow speeds, but not so much at high speeds. I was thinking about adding a second power circuit so I could activate the high speed too.

If I recall, the fan you added is only thermostatically controlled?

 

The fan and controller are purchased separately. The fan can be controlled with a switch alone, or with the thermostatic controller and an override switch. The 10" fan draws less than 6 amps according to Derale's specs.

Jeff

 

Some of the data collected in Colorado. I'll just present the data where there is a similar log from last year to allow for ease of comparing data, showing the comparable plot from last year first.

We did the same stretch from Ouray up the Mineral Creek trail to Mineral point, similar to last year. We did not take the trail up to Engineer Pass so that tough section is missing. The ambient temperature this year was about 20 degrees warmer, but the ATF temepratures were still lower. Consistently, when the fan turns on, the ATF temperatures would drop; and when it turned off, the ATF temperatures would rise.

In higher ambient temperatures, the ATF temperatures may not drop but there is definitely increased cooling capacity.

We made the trip to the East Portal on the Gunnison River at Black Canyon Of the Gunnison NP. The road is posted at a 16% grade. The ambient temperature was similar to last year so the data is more directly comparable. Again, the fan kept the ATF temperature from rising as high as just normal airflow.

Something worth noting is the coolant temperature entering the engine. After the coolant flows through the radiator and loses heat, the ATF-rad heat exchanger adds heat. The temperture of the coolant tracks the temperature of the ATF entering the rad. As the ATF temperature rises, the coolant temperature rises also. Reducing the temperature of the ATF reduces the heat the cooling system needs to manage.

I'm pleased with the added cooling capacity from the fan. Changing my driving to use lower gears to reduce the slipping of the torque converter also reduces the heat generated in the transmission. While this doesn't increase the performance of the driveline, it does help keep the ATF temperatures in a better range and does reduce the cooling load on the cooling system.

Cheers,
Jeff

 

Jeff, I would figure the trip up California Pass would have significant info as well. I don't remember your logging memory filling up til we had descended Corkscrew. Did you just choose to omit that or was that data unusable? Maybe since you didn't have that trip last year to compare to....

 

Compare by-passed rad cooler?

I would be curious to see a graph showing temperatures in a by-passed rad/tranny cooler with the added cooling fan, compared with a factory set-up . Even just for a driving around town comparison... How much higher would the ATF run without the rad cooler.

 

Good info Jeff