Honda Ridgeline Owners Club Forums banner
1 - 20 of 72 Posts

· Premium Member
1,817 Posts
Discussion Starter · #1 · (Edited)
The graph below is a fairly accurate representation of the thermal management system in an 06 Ridgeline.

Text Line Font Parallel Paper

EDIT: Reposting resized chart

This graph was generated after logging data from short trip, bringing under hood temperatures to normal levels in a "bone stock" daily driven 2006 RL. (Bone stock = OEM Denso radiator)

As shown in the graph, we observe the running temperatures of:
- Engine coolant leaving the block, destined for the radiator.
- Coolant returning from the radiator to the block.
- Trans fluid entering and exiting the OTW trans cooler.
- Trans fluid entering and exiting the OTA trans cooler.
- Engine compartment ambient air.

Interesting, huh?

It's a safe guess you are questioning how this data was collected - and by extension, how accurate it might be.

Fair question(s).

Before explaining the test configuration, a quick description of an error in this data: the digital hardware used to probe temperatures have "addresses" stored in resident ROM. When initially configuring a network like the one described below, the first step in set up is: identify the unique address of each probe so the script running data logging can report the location of the probe. In support of that effort, multi-colored heat shrink was applied to the tail of each device. A map was then created to assign the probe color to a physical location, then each probe was connected one-at-a-time to the development board where its address and color were logged in a spreadsheet - as you'll see below.

This first pass chart reveals one of two problems with the data. As you may be able to see in the chart, the measured temp (supposedly) gathered at the hose connecting the OTA and OTW trans coolers is higher than the values measured at the send/return ports of those devices. Obviously, the fluid passing between these components cannot be hotter than the fluid on either side of them because there is no heat source to make that happen.

This means:
a) I flubbed the color coding/ROM address recording, OR
b) one of the probes is WAY out of alignment.
If a) turns out to be true, this means TWO probed locations are out of line. And that means understanding the effect of components of the trans cooling circuit is not yet available.

There's an easy way to detect which problem might be happening here, but I'm about to hop on a plane for a week long business trip, so diagnosing the root of this issue will have to wait for a couple weekends. Currently, the assumption is: I flubbed the color coding/ROM addressing. We'll find out soon enough.

Also note: the graph is the result of approximately 4 minutes of logging when the vehicle was operating at normal temps. After more tweaking on the script used to poll the probes, temperature "rise time" at each probe location will be logged and further data analysis will occur.

Following is a description of the test configuration used to gather this data.

Vktech DS18b20 Waterproof Temperature Transmitters (5 total)
LANMU® UNO R3 Atmega328p/16u2
Arduino SW version: 1.0.5
Custom OneWire script for Maxim/Dallas digital temp sensors
(Note, in Arduino land: "scripts" are refered to as "sketches".

The temperature "transmitters" (hereafter referred to as: "probes") are affixed to fluid hoses according to diagrams below:

Line art White Text Drawing Design

Diagram Automotive exterior Drawing Auto part

Graph trace labeled "Underhood" is captured via a probe mounted in "free air". It's location shown in this image:

Vehicle Car Auto part Automotive exterior Family car

Because these probes are surface mounted, thermo-coupling is a significant consideration. Three elements were considered here:
- maximum conduction from mounting surface to probe.
- rejection of external thermal influences on the probe.
- probes attached to "like" surfaces. In other words, all rubber or all metal - not a combo of the two.

To the degree that similar surface compositions predictably conduct heat, and because they are readily accessible, fluid hoses were chosen.

Each probe is wrapped in radiant/reflective closed cell foam core/double sided aluminum heat shield. The idea is to contain heat generated by fluids passing thru the hose - "concentrating" heat into the probe (so-to-speak) while simultaneously isolating the external environment influence on measured values. Each wrap was closed using aluminum tape and further affixed with a wire tie.

Probes shown in their mounted locations:

Auto part Pipe Fuel line Engine Suspension part

Auto part Fuel line Tire Automotive tire Pipe


· Premium Member
1,817 Posts
Discussion Starter · #2 · (Edited)
To the extent this methodology effectively captures temperature characteristics of the intended targets, concern over probe accuracy enters the equation. Info on that:

DS18b20 probes are spec'd @:
Operating temperature range: -55°C - +125°C (-67°F - +257°F)
Accuracy over the range of -10°C to +85°C: ±0.5°C

The spec above is a direct quote published by sensor OEM: Maxim/Dallas. Operating range is quite wide, the upper end aligning nicely with typical automotive transmission/engine operation. Of particular interest is sensor accuracy spec. I was curious why Celsius was listed & Fahrenheit seemed specifically omitted. I've yet to adopt mental conversions, web services to the rescue:

-10°C to +85°C / ±0.5°C converts to 14°F to 185°F / ±32.9°F

In all likely hood, the spec published by Maxim/Dallas originates from a VERY large number of devices. While the swing is real, "out-of-the box" device-to-device variance is likely much tighter than spec. Here's a graph from the MDS:

Text Line Parallel Diagram

The reason accuracy is published in narrow band (context: narrow compared to overall operating range) is: above and below 14 to 185°F, accuracy swings wider. Which is concerning to any project seeking comparative data.

Within the specified range, we have a potential ±19.3% swing!
One might conclude that - in raw form - these are not lab grade sensors. With that said, typical analog thermistors found throughout many (or most) automotive systems *may* fall into this range as well. Accuracy and dimensional tolerance of any component comes at a cost, and "good enough" often rules decisions made when product designers operate within a budget, so, as is true with everything else used in automotive manufacturing analog thermistors may - or may not be - "more accurate" than digital sensors. But I digress...

There are methods to individually calibrate digital sensors. With neither the tools to generate heat tp precise levels, nor calibrated measurement devices to verify reported results, I'll trust that the published spec is "worst case scenario" and opt to observe available data in stock form.

In order to satisfy personal curiosity about accuracy variance, a consumer level infrared scanner was used to measure the surface temp of a probe "in free air while running the OneWire sketch. The results were with 1/2 degree of each other.

With that info, it must be acknowledged that the infrared device has its own calibration and measurement errors, but geek momentum hasta stop somewhere and this is where I draw that line. This is my personal "good enough" line in the sand.

Another base line for accuracy: the same infrared scan was used to probe surface temps at each location prior to start up of the first test. Measured values reported by the network closely aligned (±0.5°F) with the infrared scan. I'm satisfied that @ 50°F, the probes are accurate.

Knowing this (and similar) project(s) will have both known and unknown variables stemming from components, methodology and human error, this project was not intended to measure absolute temperature at each probed location, rather, the goal is to measure the delta between each probed location, creating a meaningful "map" of the thermal activity in each component responsible for thermal management.

Another goal is to measure thermal performance in "stock" configuration compared a change to an aftermarket radiator/OTW assembly (in my case, replacing OEM Denso with aftermarket OSC).
That may not be a totally fair comparison because the OEM configuration has 114K on the clock.

In regards to pre rad swap test config, the 06 is up to date with service, having:
- (3) recent DIY D&F of trans fluid (recent = less than 3K ago)
- A shop supplied engine coolant change out approx. 16K ago. Depth of that procedure is unknown and questionable based on poor experience with that particular shop. Visually, fluid appears "OK".
- Engine oil is @ 30%.
- Air filter changed 3K ago.

The OSC aftermarket rad will be installed in the near future (later this month). At that time, she'll get another trans D&F and engine coolant exchange per FSM using OEM fluids. Test results to be posted upon completion. Personally, I don't expect significant deltas between pre/post swap out measurements, but we'll see.

Quick mention:
"OneWire" protocol doesn't literally mean One Wire. There are three wires required for each probe. They are:
- data
- 5VDC +
- 5VDC -
Each Maxim/Dallas chip has a unique "address" stored in ROM, as such, they identify themselves in polling by their unique address. This makes possible "one wire" (data) termination @ the UNO board. So... the 9 wires coming from 3 probes located @ the bottom of the rad are joined to a 3 conductor cable. 6 wires coming from the 2 probes located on the engine coolant send/return hoses are joined to a 3 conductor cable. The resulting 6 wire/2 cable pair run under the engine air intake throat, over/on top of the drive side wheel tub where those 6 wires join with 3 coming from the ambient probe located top of the firewall. The single/3 conductor cable now enters the grommet above and behind the brake booster where a previously installed 4 gauge cable enters the cab to power audio amps. All connection points are twisted/soldered/heat shrink wrapped. That was tedious work. FYI: a bench top/variable temp solder station operating outside, on a concrete driveway during a 50°F windy day is both physically and environmentally hostile to soldering!

That 3 conductor cable is loosely run to the front passenger seat, connecting to the Uno board which is USB connected into a laptop running the Arduino application.

The work done here is temporary in the sense that when measurements are completed, probes and wiring will be removed. It simply isn't practical to operate a daily driver with a lap top in the passenger seat. And I'm not going the route of a Jotto Desk or car PC. At least not yet. Although I have long romanced the idea of a car PC, but that's another story.

The goal of this project is to assist in understanding thermal behavior during "warm up" and provide (what should be) expected behavior under normal driving conditions. I would be interested in seeing what happens when the truck is loaded somewhere close to max_pay_load but not sure I have the means to accomplish that. I'd also like to see real world measurements under various climate conditions, so I may leave the network in place long enough to gather data in mountain snow and San Diego summer conditions.

None of the wiring was routed with the intention of being permanent. Nor were probes affixed to their assigned locations with permanence in mind. Having said that, if anyone has ideas on other locations to be monitored, I have several spare probes sitting around. If I can work up the gumption to tackle more soldering/cabling, perhaps an interesting project could be added to the future.

Other than conceptualizing a method for thermos-coupling, none of this was invented here. All that was required to put this together was an investment in researching available off-the-shelf solutions and a bit of physical effort.

Credit goes to:
ROC forum member Carsmak for squaring me up on probe locations. I had the idea of overkill, his perspective injected a large dose of reality to the project.

One Wire "sketch" authors from around the globe. These are the geeks that make all kinds of things possible for people seeking knowledge on any number of interests.

Arduino for making development boards available to hobbyists seeking knowledge.

"" for authoring an article putting these resources together in a way making it possible for dopes like me to pull of a project like this.

Reference material authors creating calibration techniques such as:

I hope someone finds value in this data. I found it personally rewarding to put together.

· Premium Member
1,817 Posts
Discussion Starter · #4 · (Edited)
Probes and Arduino development board:

Pink Material property Writing implement Stationery Mug

Cable management Electronics Wire Electrical wiring Technology

A bit more info on comparing probes hot/cold to infrared. OBD temp report from the Torque app for reference.

Text Font Line Number Document

Text Font

IMO: this info correlates accuracy sufficiently. I'm confident the digital devices are aligned to tight tolerance for the purpose of understanding the effects of heat management under the RL hood.

Looking forward to solving the snafu on the OTW/OTA thing.

· Premium Member
1,817 Posts
Discussion Starter · #6 ·
Wow, quite a lot of work, and I know that one probe issue is going to bother, you.
After a quick visual confirmation, probe color/location correlates with the diagram generated when ROM addresses were captured. So unless I really blew the import of addresses to the chart, measured results are a mystery.

When time is available, I'll unwrap probes on the trans fluid lines and use a heat gun to ensure addresses are correct.

Crazy part about the error is THIS is exactly what I was seeking: a better understanding of the effects both OTA and OTW coolers play on fluid leaving & returning to the trans. I hate making stupid mistakes!

· Premium Member
1,817 Posts
Discussion Starter · #10 · (Edited)
Thanks guys for the comments.
Hokie: I'm more than willing to let the data tell the story, and it bothers the chit out of me there is an error in the system - so I'll definitely run that issue to ground. I'm actually thinking this problem offers a yet-to-be-considered opportunity. Using a heat gun on ONE probe while the Arduino script is running will definitely reveal where the problem lies, but what about measuring "isolation" of the "closed cell foam/double sided ALU radiant heat deflector? Two aviaries/one test is what I'm thinking. :) Leave a probe wrapped, heat the outside, see results then un-wrap it - repeat and see results. Cool thing is: Arduino script can run while vehicle is OFF, so temp +/- can be logged under each scenario.

I have no idea if anyone is following this. But geek-momentum overrides that concern. :)

In the meantime, sitting on a 5 hour plane flight thinking about this issue made me nuts. I broke out the computer and stared at the numbers. Here's what I came up with:
1) Naming conventions specifically labeling probes with locations like "engine block coolant output" and "trans fluid output line" were intentionally avoided. The idea was throw out assumptions, any assumption, and let heat tell the story of what-is-happening-where.
2) Fair effort was put into verifying the accuracy of these 5 probes. It looks to me they ARE. So an out-or-spec probe is off the list of potential problems.
3) That leaves location/color coding/ROM addressing at the root of the issue.

With those things in mind: looking at the #'s, it occurs to me heat SOURCES are easily identifiable in flow of fluids. For example: Coolant is heated by the block, sent to the Rad to be cooled before being returned to the block. Can I get a DUH? So we can measure fluid temps and safely assume hotter is send and cooler is return.

In a vehicle operating at temperature, its safe to assume fluid leaving the trans to be treated externally before returning is warmer on the way out than the way back in.

SO: if we flip probe address #’s labeled “OTA/Trans” and “OTA/OTW” and change labels based on WHERE heat is coming from, look what happens:

Text Line Parallel Font

Here's what overlaying one row of numbers on an FSM image looks like:

Diagram Line Auto part

No comment from me. What do you guys think?

eurban: I too am VERY interested in temp rise time in other ambient environments. A trip to the snow, overnight stay to let thing cool all the way down followed by a timed log is most definitely coming in the very near future. Carsmak tells me its been way down in the low double digits up in the Big Bear area. Might be time to take the little lady for a ride and cabin stay. For the purpose of gathering data, of course. Temp rise times is another way of understanding the effects of OTA & OTW on trans fluid. And hyper cold weather should make that stand out like frost bitten finger.

· Premium Member
1,817 Posts
Discussion Starter · #15 · (Edited)
I don't think the last graphic (with temperatures on the radiator image) is correct, assuming we're still working with the same data. I can accept that the fluid leaving the transmission is ~140 deg F. Then it flows through the radiator's heat exchanger, which is surrounded by ~160 deg F coolant, and emerges at ~100 deg F?
Was wondering who would make that observation!

At this point, there is only one data set.

If we accept the temperature data itself is accurately captured by the probes, and forget about which probe is where, there are a limited # of conclusions to be drawn.

The spreadsheet snippet in the upper right corner of the graphic below shows 1st and last data columns in the data set.

The final column in the data happens to be the highest measured values resulting from a short/steep climb up a hill to my neighborhood. Transferring heat values to their most likely location, this is what you get:

Diagram Text Line Parallel

How could trans fluid entering the OTW exit @ lower temp than the engine coolant its immersed in? Far as I know, that can't happen.

One of the goals behind the project is to eliminate (or greatly reduce) speculation about what is happening in heat management, yet being here I am speculating further by trying to stuff what I think into data results in order to compensate for a human error in data collection.

Again, I'm confident the probes and measurements are accurate. Aside from the question of what's happening between the OTW & OTA, the effectiveness of the engine coolant seems weak. But then again - we don't know what we don't know, so perhaps a 5 to 14% temp reduction is "normal" while the trans circuit enjoys 24 to 42% reduction?

Line Text Parallel Font Diagram

Text Font Line Number Parallel

EDIT: (since we are entering deep into the world of speculation - end edit) For the moment, no more analysis on these numbers until the remaining questions about probe locations can be resolved.

· Premium Member
1,817 Posts
Discussion Starter · #18 ·
Even if you flip the fluid flow direction (based on FSM label "ATF Cooler Outlet") so that hose is actually feeding the transmission, that would mean the transmission itself is dropping the temp from 141F to 81F. There's no way that can be true - even if you posit that it's presence in the airflow under the vehicle allows for cooling effects, it's proximity to the engine and exhaust would make that implausible.

Yeah, there's something else wonky.

Chip H.
Without being able to lay hands on the probes to (re)verify addresses, color codes and locations, the best conclusion now is I REALLY screwed up the recording of those things, and the resulting temp values are completely whacked in their (now) assumed locations - thereby throwing them out.

Having said that, the procedure used to put that information together is pretty straight forward. Running the script with a single pre-color coded probe connected to the Lamu/Arduino board - and copy/pasting the alpha/numeric addresses reported by the script - along with the corresponding color code into a spreadsheet, then transferring each of those to engine drawings taken from the FSM. With that done, the diagrams were used as a guide to physically attach each probe in their assigned location. I'm more than open to accepting I totally whacked that process but rewinding the video in my head of doing that, it is a difficult pill to swallow. Especially in light of knowing the probe colors are - indeed - placed in their assigned places.

Auto part Tire Fuel line Vehicle Engine

So.... verification is the only way to end speculation of what-went-wrong-where.

· Premium Member
1,817 Posts
Discussion Starter · #19 ·
Very Nice work OhSix!

I think your numbers reflect flow and I think the FSM is a typo as the page before list that point as cooler inlet. (In the cooler flushing section)

A lot could probably be deducted from radiator efficiency also in reflect of the in/out temps.
I figure our radiators are single pass.
Food for thought...
Thanks skelly. Yessiree, our radiators are single pass. Here's a couple links to tear downs of radiators you might find interesting.

Anatomy of a Denso radiator

Radiator comparison: Denso/Spectra/OSC

· Premium Member
1,817 Posts
Discussion Starter · #21 · (Edited)
Update: Probes addresses, color codes and physical locations have been validated. Here's how:

- Removed heat shields from the lower 3 probes: OTW/Trans, OTA/Trans and OTW/OTA. Each probe was now in plain sight, still affixed to their original locations indicated in diagrams shown earlier in this thread.
- Engine off. Computer, LAMU board, and Arduino SW connected, configured and running.
- All probes report as follows:
Text Font Line Number Parallel

- With logging active, heat gun one probe at a time, starting with: OTW/OTA, then OTW/Trans & OTA/Trans
- Scroll probe file to find 1st probe temp rise, note address.
- Scroll probe file to find 2nd probe temp rise, note address
- Scroll probe file to find 3rd probe temp rise, note address.
- Compare addresses to map. Confirm all color codes, address notations & physical location match original sensor map.

Original plan called for color coding probes, connecting one at a time, logging each address and creating a visual map for location. The method used above reverses the original plan by heating each sensor while in place and allowing the script to log the results. SO... there is no error in terms of the probe map.

So what's up with the weird data? How come the fluid passing from the OTW to the OTA is hotter in between those devices than on either side? To hokie's point, how can fluid exiting the OTW be cooler than the engine coolant its sunk in? Good questions. Been stewing about that ever since putting the first pass data out there.

So, after confirming the probes are both accurate and located where the map says they are, I decided to more completely cover these 3 probes. In the first configuration, the shields were 2" - more than enough to cover their stainless heads but there was potential air flow could be contaminating measurements. When the lower probes were put in place, the apron/lower splash guard was removed - I've been driving around like that since. Turbulence causing air to alter temp readings? Maybe.

So new 3" shields were fashioned, aluminum taped in place and the ends were closed off with wider wire ties.

Auto part Pipe
Auto part Automotive exterior Bumper Metal Automotive lighting

Thinking I was going to capture the first "cold start" data set, I lit out for the office, making note of drive times/mile stones (like entering the freeway) and everything else I could think of. I'm still unfamiliar with the MAX_NUM of lines Arduino's serial monitor will retain, so I shut down logging at 15 minutes and finished the ride in. Murphy must of heard how much I was looking forward to capturing new/improved data cuz he did a drive by - in the form of the blue screen of death. So, I guess cold start data (should be somewhere under 45) will hafta wait til tomorrow.

In the meantime, had to make a bank run a few hours after getting to the office, so engine coolant was still over 90 @ start up for the results below.
Text Line Slope Diagram Plot

The spike seen between the 7 & 13 minute marks is the result of stopping at the bank. Couple of stop lights on surface roads between the office and bank - inside the bank for maybe 5 minutes, then minor surface roads to the freeway where the bulk of the 13 minute trip was @ 55MPH or better.

The grid at the top of the chart are the raw numbers taken from the last few entries at the end of the freeway run.

Looking at the last line in that data, what I see is:
- Trans fluid leaves the trans/enters the OTW @ 119.52
- Trans fluid exiting the OTW on its way to the OTA has been HEATED to 132.24
- Trans fluid exiting the OTA on its way to the trans has been COOLED to 99.5

Perhaps more data, LOTs more data will tell another story - but - based on this one run, under this very narrow driving scenario, this design is HEATING UP trans fluid only to cool it down before returning to the trans. EFFING CRAZY!

Same chart as above, but with engine coolant temps removed:
White Line Text Parallel Diagram

· Premium Member
1,817 Posts
Discussion Starter · #23 ·
Maybe.... but maybe not. It could be that in extreme cold (Hello Yellowknife!) it needs to be heated up before being temperature "stabilized" (cooled down to known temp) for return to the tranny. Just speculation, but it's certainly one theory as to why they might do this.

Too bad you can't get same readings up in Nome or ???
I dunno Dnick. Based on temp readings, fluid flow direction makes OTA last in the return path. By definition, external air is an unknown - from an engineering perspective - so OTA's influence over fluid temp is unpredictable. If flow was the opposite direction, engineers could rely on engine coolant being in a narrow range - therefore having a predictable influence.

For data samples in the cold, I'm toying with the idea of heading up to Big Bear for an overnighter. Carsmak is keeping an eye on weather up that way - sure would be nice to get into the low double digits.

I have a feeling some of our members farther north get a chuckle out of what us So. Cal residents call "cold".

· Premium Member
1,817 Posts
Discussion Starter · #26 ·
I think your data is good, and is what I would expect. The transmission engineers have to design to the worse case scenario, and that worst case scenario will send transmission outlet temperatures much higher than 119.52 deg F. The worst case will be towing a boat or something on a hot summer day, backing up and down a boat ramp where you have no torque converter lock and a lot of slippage due to high torque/low speed maneuvers. Or backing a trailer in and out of a camp ground space, etc. In this case, transmission outlet temperatures may be WELL over 200 deg F, or even closer to 300 deg F. In this case, the OTW exchanger will be receiving fluid much hotter than the engine coolant (since the coolant in the radiator will always be in the 160-180 deg F range once fully warmed), and the OTW exchanger will provide some cooling and the OTA exchanger will provide more cooling.

Certainly, the external OTA exchanger is WAY overkill for a gentle ride to work and the bank on a winter's morn. It's not needed at all...and you could say that it's actually counter-productive at this point, and keeps that fluid colder than it really needs to be (increasing its viscosity and internal drag).

It's probably not needed in most cases, but they have to provide that cooling capacity in case the truck is used to its full design capability (towing a 5000 lb trailer through a desert summer, for instance). In most cases, yes, the transmission outlet temperature is probably colder than the coolant in the radiator, so the OTW exchanger warms the fluid. This is fine -- if it gains heat through that, and then gains more heat through the transmission, then gains more heat through the OTW again, etc etc etc, it'll eventually reach the point where it's actually hotter than the radiator coolant, and it'll experience cooling in the OTW exchanger, rather than warming.

You could say that it acts like a thermostat to some degree. While, at the same time, the OTA exchanger is doing its best to not let the fluid get hot enough where it's cooled by the OTW exchanger in the first place.

Thanks Hokie. More data a little later. Currently, its 43-ish outside. 06 should be right around ambient since she's been sitting for nearly 12 hours. Looking forward to capturing thermal behavior at start up and rise to operation temps. I'll dice the data into smaller chunks, especially in the first 5 minutes. The results should be instructive.

Couple of things:
The last data set pretty much confirms fluid flow direction - and if that remains true, dispels the "rumor" that the OTW is a "pre-heater".

That flow direction conflicts with the experience of forum member bobcat20. He installed an in-line filter - in doing so - he had to confirm low direction - so by putting his hands on the plumbing, he observed flow in the opposite direction. This remains a ? for me. No explanation for that yet.

The FSM mentions a cleaning procedure for the OTW. The flow specified for that procedure is likely reverse of normal flow and if that's true, supports the flow suggested by thermal behavior. BUT... in that section of the FSM (which I have not studied) it mentions an "external filter" - as if it is a factory component. This further confuses the chit out of me as I'm totally unaware of that element.

On the topic of fluid viscosity... I get that OEMs are trying to eek out every last drop of efficiency as they struggle to conform with regulations, fleet management, ETC. But seriously, how much influence would "thick" trans fluid have in overall MPG average? Obviously, Honda is getting great reliability out of a properly maintained trans, so there's little question they've hit the balance fulcrum mark.

The reason I question the wisdom of OTW in the circuit is: I can't stop thinking that reliability - in every sense of the word - would increase if the OTW was capped in favor of a larger OTA. I'm probably stuck in street level lore here, but IF COOLER trans fluid = longer service life THEN removing potential for SMOD along with increasing cooling seems logical. Again, I'd like the data to tell the story by removing all rumor and opinion.

Without stress testing in different climates, terrain, load conditions, ETC, this data collection effort might not be complete, but I think we are at least more informed now.

With a trip to the mountains in the works, maybe that would be a good time to max out the truck bed, drive up, cool down and reverse the process. Any body have a a couple of engine blocks they can donate to the cause? How about a load of cinder blocks? LOL

· Premium Member
1,817 Posts
Discussion Starter · #33 ·
Data from this mornings start up. Haven’t had much luck with sizing charts so not sure how informative they are.

Total duration of this data set 12 minutes. At the 4 minute point, 06 is entering the freeway. For the next 8 minutes, she’s cruising between 55 and 70MPH.

Although I have no reason to be, I’m a bit put off by MAX_NUM’s in this data set. For example, filtering highest values measured at each probe:
- Coolant leaving the block only reached 124.9 at its peak.
- Coolant retuning to the block from the rad reached 79.57 at its peak
- Underhood ambient reached 104.79
- OTW/Trans reached 80.94
- OTA/OTW reached 89.37
- OTA/Trans reached 66.43
Mind you, those are HIGHs. Ambient reported by the gauge cluster varied between 50 and 54 during this run. Trans fluid anywhere in the flow measured between ~90 & 66? That’s cool fluid right there.
Anyhoo. The charts. Top is the total run, all sensors. Bottom is trans fluid only.
Text Line Parallel Font Document

In effort to display the same data a different way, here’s a slightly different perspective. You never know how these things will look until they post.
Text Line Plot Diagram Slope

I hear you guys about ending speculation. That's one of the goals of this project. Comments so far are based strictly in what the data suggests, and to that point, *speculation* is: any transmission operating under any load condition is going to produce heat, sometimes LOTs of it. IF that speculation is accurate, then the hottest side of the trans ports reveals flow direction. But I say again with all sincerity, speculation here needs to be squashed once and for all.

So far the data says one of two things: at full operating temp on a 60f day in So Cal, driving down a freeway, fluid exiting the trans is either 99.5 or 119.5.

BTW: those values seem pretty narrow and pretty low compared to what I thought I knew. Learning is like that sometimes.

The question now becomes, what happens to fluid temps passing thru external exchangers? Is it heating up or cooling down?

Under other load conditions, the answer would be self evident and unquestionable - but under these mild conditions, the answer remains fuzzy.

With that in mind, one of the goals tied to this project is pre/post results of swapping OEM Denso with aftermarket OSC. In other threads, I've dissected radiators, measured OTW capacity, counted OEM and aftermarket core passages, ETC. With the data collected up to this point (with more to come), measurements will be taken once the OSC is installed. Part of that process will include bobcats suggestion to run trans hoses into a bucket and see what happens when the trans pumps.

I'll record that. Post it on youtube, with witnesses standing by, sworn affidavits, armed guards, notarized documents, armed guards, signatures of authenticity that if falsified results in penalty of U.S. international law. ANYTHING to end the speculation! :act060:

bobcat: I hope you know, there is no reason to doubt your experience, it just conflicts with things mentioned in the FSM and personal long held assumptions/conclusions.

This is a good example of confusion in this area.
Note: the naming convention for column headers is intentionally non-committal. What I mean is, they are named to described location only. So these are describing the connection hoses between components. In the data set below, the most logical observance is fluid is reentering the trans @ 66.43f. Any other conclusion would mean that fluid leaves the trans/enters the OTA @ 66.43 but exits the OTA @ 89.15. Since the OTA is traveling down the road @ freeway speeds on a 55f day, it doesn't seem possible fluid is being heated by an air to oil device.

Text Font Line

· Premium Member
1,817 Posts
Discussion Starter · #35 ·
Making the file available for others to review.

Couple of notes:
This is a snippet of data created in the Arduino serial monitor:

Text Line Font Technology Screenshot

Once a string of data is collected, it is copy/pasted into an excel spreadsheet.

As anyone curious enough to look at the file will see, the task then becomes:
1) Deleting spaces and superfluous text
2) Filtering for address, changing the address numeric values to real name/location
3) Creating an indexed column for each measured value, keeping sequence in order.

The tab labeled "ColdStart_20160114" is the copy/pasted text from the Arduino serial monitor captured during this morning run.

The tab labeled "breakdown" is the result of processing the text as described above.

Once step 3 is completed, the data can be charted, sliced by time, ETC.

In this file, there are 115 events reported by each probe. Those events represent a total duration of (nearly exactly) 12 minutes of run time. Based on that, you can estimate time windows by # of rows.

Perhaps this will assist in assimilating the data.

EDIT: After describing the above, it turns out the upload function here won't allow upload of either an xlsx or xls file. The attached data is plain text.

View attachment 20160114_Raw.txt

· Premium Member
1,817 Posts
Discussion Starter · #40 ·
This link below from Bobcat agrees with the post above (my sincere apologies if I'm miss-quoting anyone) and also how my 06 is plumbed. Perhaps I'm not referencing the correct post since there are so many at this time, but there is no doubt that my 06 goes from the AT >> to radiator ATF cooler (OTW)>> to external (OTA) cooler >> back to the AT

Its possible that folks may have changed their thinking with time and data availability, but from this post it looks like we agree at this point. Am I missing something?

And of course continued thanks OhSix for the huge amount of work on this. Its all still very interesting for any gear-heads!!!
Holy Rabbit Trail Batman! Yes, indeed, we are all in agreement. You aren't missing anything, tis my error - misremembering/misrepresenting bobcat's contributions in that thread. His hands on experience aligns with measured values. Thanks for setting things straight schwejo. And apologies to all for the non-existent *issue* - especially Mr. Bob-Cat.

On the topic of thermal management in the trans fluid circuit...

Hokie mentioned engineering for the widest array of climates and loads. To his point, data gathered so far happened during of some of the mildest conditions imaginable. ~60f, ~50% humidity, unloaded RL, more or less flat roads, freeway cruising. None of these stress the drive train or demand peak thermal transfer from the cooling circuit.

Carsmak and I have been discussing throwing a few challenges on the calendar. Future data collection will include pulling mountain roads before and after winter leaves the region. And a trip or two out to the dunes where 120f is a regular thing. Perhaps a trailer pull or two. More to come.

· Premium Member
1,817 Posts
Discussion Starter · #43 ·

Finished building the project box for the Arduino board. No more clip leads & worries about sudden stops or corners or nuthin'.

Electronic engineering Electronics Circuit prototyping Circuit component Microcontroller

Electronic device Adapter Technology Product Electronics accessory

Product Electronic device Technology Electronics accessory Cable

Test run this morning with the new plug and play set up gathered a bit more data on a 20 minute run. This time, I ran the Torque App, logging OBD engine coolant and air intake.

Chart and numbers at the conclusion of the run below.

Line Map Text Ecoregion Slope

Text Blue Font Line Number

Referring to line 177, observe column D header "OTW/Trans" is the output from transmission to the "oil-to-water" heat exchanger buried in engine coolant at the bottom of the engine rad. Fluid leaving trans is 114.46.

Now observe column E header "OTA/OTW". This is the line connecting the "oil-to-water" exchanger to the "oil-to-air" exchanger. In this example, fluid leaving the OTW is HOTTER than fluid leaving the trans. Meaning, engine coolant is warming up trans fluid.

Now observe column F header "OTA/Trans". This is the line connecting OTA to trans. In this example, the fluid passed to OTA from OTW is COOLED to 95 before returning to the transmission.

More data coming. Next time, mountains, snow, bears and zombies will be thrown in the mix.

· Premium Member
1,817 Posts
Discussion Starter · #45 · (Edited)
In attempt to combine mountain climb & descent with exposure to cold, made a run up to the San Bernardino mountains yesterday. Weather forecast snow, so it seemed like a good time.

Unfortunately, weather didn't cooperate with NOAA. And it seemed like every Southern California resident with rubber and fuel had plans to be in the Big Bear area too.

Traffic was absurd towards the top of the mountain, coming to a complete stop right around 6,000 ft mark @ the intersection of 330 & 18. So grabbed the 18 and ran over to Lake Arrowhead, then back down the mountain to San Bernardino.

With the drive train at full operating temp, turned on logging @ 330 & 210, elevation 1,318 above sea level, made the 35 minutes run to 6.040 ft @ Running Springs. The 15 mile climb to 4,700 ft @ "normal" speed of a comfortable drive up the serious switchbacks. Not too fast, not slow. 06 was loaded with 2 passengers and regular junk people carry, just like every other day of the week. Ambient temp at the bottom of the hill 65, 50 @ Running Springs.

Bar chart of the last few temp samples before turning off logging.
Text Line Parallel Font Pattern

Nice slow cruise over to Lake Arrowhead. Stop for coffee and quick tour of the village, then back down the hill, descending from 5,500 ft to 840 ft. 25 minute run 17 miles. No D3 use of engine braking, just occasional tap on the brakes where needed.
Blue Text Line Diagram Font

So there you go, an average RL under moderate strain climbing a mountain in mild weather. That same RL coasting down a mountain.

Now, a storm has hit the So Cal area and its snowing like mad up there. Bummer that. It's not too unusual for snow to get down to the 3K ft level so there should be opportunity soon in the local mountains. Perhaps Mount Palomar or the Cuyamaca's. When that happens, an overnight stay in a cabin would facilitate a nice cold start scenario.

Thermal management #'s converted to % of influence in the chan.

Text Font Line Number

· Premium Member
1,817 Posts
Discussion Starter · #47 · (Edited)
Data is relatively simple to understand now, charts are still a PITA, to read, but maybe that's my 3yo iPad 2 tablet and the screen resolution.

Keep up the good work, Six!!!
Thanks Mak. Since we got hit with that huge storm last night, it got down right cool around here. Actually had to wear socks, shoes, long pants and everything.

Now that the Arduino board is safely contained in a box, setting up for logging is painless. This is what's happening under the hood @ start up on a 42 degree morning, idling in the driveway for 8 unnatural minutes, trans in neutral, HVAC set LO:

Line Text Parallel

Low/high values used to create graph above

Text Font Line Number Parallel

At the 8 minute mark, logging was turned off, data captured and saved. So, in the data set below start temps are higher than stop temps in the data above - only cuz of 3 additional minutes idle time while data was captured and loaded to a temp file.

Text Line Diagram Parallel Plot

Low/high values used to create graph above

Text Font Line Number Parallel

Even with a clear understanding of WHAT the OTW & OTA are doing in fluid flow, direction and thermal influence, WHY the OTW exists remains unexplained on the OEM side of the industry. SAE doesn't explain its purpose - at least not in public information I've seen. And Honda's FSM only adds to the mystery through odd syntax and reference to none existent components (like an external trans filter!).

So the door open to speculation remains open - which is what was to be avoided by this little project.

As long as speculation is on the table, I'll speculate the OTW exists for the singular purpose of incremental improvement to the almighty MPG prominently displayed on window stickers. Perhaps there is information to the contrary - perhaps service life is increased by X% through this thermal management design implemented by so many OEMs - but I doubt that is the real goal.

OEM's need that CAFE # - and to get it - they'll concoct designs that allow incompatible fluids to mix.
1 - 20 of 72 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.