[OhSix]

A tear down of the OEM Denso & aftermarket Spectra radiators, New OSC included. Thanks to forum member Carsmak for the OEM and Spectra donations. The new OSC to be installed in the 06 in the near future. Out of box impressions of the OSC in this thread: http://www.ridgelineownersclub.com/forums/showthread.php?t=122650

First tear down of the OEM Denso in this thread: http://www.ridgelineownersclub.com/forums/showthread.php?p=1709089

By now, most everyone is aware of the dreaded SMOD. This comparison focuses on the trans fluid heat exchanger and observations of general construction of OEM vs. aftermarket.

The first stand out between OEM and aftermarket designs is the mechanical attachment of the heat exchanger to the lower tank.

The OEM design relies on the trans fluid ports serve two purposes. One is to isolate engine coolant from trans fluid. The other is to serve as clamping mechanism holding the exchanger to the tank. The "problem" with this design is when a port fails at one task, it fails at both allowing incompatible fluids to mix, causing potentially serious damage to the transmission.

The aftermarket appears to have solved that issue by separating tasks. The clamping of heat exchanger to tank is discrete from fluid passages. The clamping of port to heat exchanger is a male/female flare, similar to plumbing in home/industrial construction. For fluids to mix in this design, the failure mechanism would involve two points of failure, which statistically speaking is much less likely than the single point of failure in the OEM design. Score a point for the aftermarket (IMO). And this distinction is not trivial considering the gravity of SMOD catastrophes.



Comparing inner tank seals for the heat exchanger, the Spectra appears to be die cut where the Denso is an O-Ring



Heat exchangers:
Denso (left) is aluminum stacked plates, the Spectra (appears to be) brass concentric.



Comparison of core rows:



Although there are fewer rows in the Spectra, the tubes and ports on the braised plates are definitely larger. Micrometer wasn't available to measure:



On a side note: when the lower tank was removed from the Spectra, the interior was caked with this debris. WOH! Wasn't sure what to make of it. Spoke to Carsmak who explained whe the Spectra was removed from his RL, he performed a pressure test to ID the source of a leak. He used a garden hose as the fluid and pressure source, so it turns out this flaky debris is calcium resulting from evaporated city water. Let this be a lesson to anyone who's ever used tap water to top off their engine coolant. This crap gets into every nook and cranny of coolant passage ways. So Cal tap water is notorious. EEW.

 

[OhSix]

Couple more shots comparing drive/pass side trans fluid ports between the 3 samples.

Although there is no suggestion it matters, the drive side trans port nut is pot metal. The passenger side port nut appears to be same material as the heat exchanger - which *might be* brass.



Passenger side:

 

[Carsmak]

Here is the Video I uploaded when I pressure tested the Spectra, I had primarily done this to test if I could somehow "franken radiator" the OEM and the Spectra. After testing and making some calls to local radiator shops (none of which wanted to attempt the task, I set them both aside.

Short Video of Leaking Spectra seen above. I removed the upper and lower radiator hoses from the Ridgeline used 4 hose clamps to connect the upper and lower hoses together with a 1 1/8" socket. I wish now I had some pics of that backyard engineering, then again maybe not

 

[Dnick]

Nice info OhSix.... thanks for sharing. Indeed looks like "clamping" approach is more robust with aftermarket design. Definitely less likely to get the SMOD phenomenon.

 

[speedlever]

Great info OhSix. Thanks for the pictorial comparison.

 

[bulwnkl]

Great pics; thanks!

To me, it looks like the Denso is a very significantly better (and more expensively-made) radiator, both as a coolant heat rejector and also the oil-to-water exchanger. Except for that exchanger connection...

 

[eurban]

I would be interested to know if the OSC rad has a stacked plate or a tubular exchanger.

Most certainly, the aftermarket approach to the exchanger spiggots dramatically reduces the chances of coolant being drawn into the transmission.

You may have a coolant leak, a transmission fluid leak, but it would take the exchanger tube itself to fail for coolant to be pulled in.

That said, there is no way that a tube will exchange heat as effectively as the OEM stacked plate design. Disappointing in my mind but it is hard to say how much cooling capacity is lost and if it will really matter.

 

[rollinhonda]

I would be interested to know if the OSC rad has a stacked plate or a tubular exchanger.

Most certainly, the aftermarket approach to the exchanger spiggots dramatically reduces the chances of coolant being drawn into the transmission.

You may have a coolant leak, a transmission fluid leak, but it would take the exchanger tube itself to fail for coolant to be pulled in.

That said, there is no way that a tube will exchange heat as effectively as the OEM stacked plate design. Disappointing in my mind but it is hard to say how much cooling capacity is lost and if it will really matter.

I was thinking the same thing, but being a simple tube, and of course depending on the type of metal and gauge, it might well be more robust than the plate design. Certainly there are pluses for simplicity. And it kind of supports our homespun theory about the rad being a relatively small player in regulating ATF temps.

 

[eurban]

This thread was linked by another ROC (I think is was OhSix?) member and may indicate that the radiator cooler is actually doing the lion's share of the cooling work. . .

http://www.thenewx.org/forum/showthread.php?t=30287

 

[rollinhonda]

This thread was linked by another ROC (I think is was OhSix?) member and may indicate that the radiator cooler is actually doing the lion's share of the cooling work. . .

http://www.thenewx.org/forum/showthread.php?t=30287

I don't know enough about thermodynamics to understand all the reasons 'why'. Maybe we need to think about the exchanger more as a heat sink.

 

[OhSix]

Decided to look a little deeper into the OTW designs. A couple more observations:

Had the idea to check out fluid capacity between the two designs. The idea was to weigh each design, pour water in calculate the delta. Info on that below. To ensure the cavities of both were staring as empty as possible, I settled on the idea of cleaning them with denatured alcohol.

When the OEM OTW was being handled, this fluid came out of it:



There was a fair amount of fluid inside but it emptied very slowly. The speed with which it came out of the OTW exchanger didn't seem to be related to viscosity. It seemed more like the flow was being impeded. I let it stand on end until no more came out. When loading it with alcohol, it seemed to flow into one side slowly and took an inordinate amount of time to appear in the port on the opposite side. This got me to wondering what's inside. Anyhow, once the fluid began appearing on the opposite opening, a little agitation made a few bubble appear in both ports. Once satisfied the cavity was filled completely, it was left to sit awhile. This is what came out:



Did the same with the Spectra OTW. One thing for sure, fluid flowed from one end of the chamber to the other very quickly, easily. Left it sit, this is what came out:



Rinse, repeat until fluid was clear. The OEM OTW exchanger never got any faster letting fluid run from one side to the other.

Once clean, both were blown out with dry compressed air and left for about an hour. Let the weighing begin:




Next post: wet weights and calculations.

 

[OhSix]

Loaded with water:





Calculations:



Curious about why there was such an obvious difference between OEM and Spectra, it was time to look inside:




Well, there you go. Fluid movement in the OEM gets pushed thru a complex set of veins inside the stacked plates, while the Spectra gets pushed thru a sealed inner/outer tube with a grated wrap. Interesting, no?

And the port diameters are quite different too.



It appears to me Honda has purposely choked the ports and fluid passages, perhaps to slow it down for thermal reasons. It's doubtful the aftermarket has such depth of thought into there design(s). Most likely because they deploy a single design across everything they build - when Honda engineers pump pressure, fluid flow, thermal transfer of materials and a whole mess of other factors no one else is privy to.

What do you guys think?

 

[OhSix]

Last couple observations.

While filling the OEM exchanger with alcohol, the black ring present on one port began to run. I noticed that before but paid no mind until I saw the black surface beginning to dissolve and run down the exchanger body. Started wondering if perhaps the heat exchanger is designed for a specific flow direction but I see no evidence of how that might be in the cross sections.

Then I remembered the Spectra had (what appeared to be) a pot metal nut on one of the ports, could there design be directional too? Perhaps, the Spectra might be set up that way to denote pass/drive side, but that's easy to ID by the ports angle, so I dunno.



close up of the chain mail style Spectra grating inside their concentric heat exchanger.



OH, and I took the hit for getting this stuff to the forum. See what I do for you guys?

 

[Carsmak]

OUCH!

I often wondered why the Denso, which has been out for over 2 years would still leak ATF.

This seems like from your chart, the 0.0041, ml of fluid seems small, but may explain why we (after the change) are getting more fluid out than the OEM spec?

 

[rollinhonda]

We do appreciate what you do, it is enlightening and an education < the best kind; Hands On... no pun intended.

 

[OhSix]

OUCH!

I often wondered why the Denso, which has been out for over 2 years would still leak ATF.

This seems like from your chart, the 0.0041, ml of fluid seems small, but may explain why we (after the change) are getting more fluid out than the OEM spec?

Was surprised by that tiny amount of fluid capacity in both OTW samples. And a bit confused - but totally fascinated - by the flow constraint in the OEM exchanger. I have a buddy with a water jet, thinking he might be able to cut thru the core more smoothly than my crude non-ferrous blade on a chop saw. Would be interesting to see the composition of the passages undistorted.

This is about as clear an image as I can get with my crappy camera. If you stare at it long enough, you can see how all 88 star constellations would have appeared from the vantage point of Mare Nubium in the year of our Lord 918. I'm telling you, those Honda guys are magicians. LOL.

 

[Carsmak]

It would seem that the Denso would slow the flow out of the Trans Drain plug? Just a thought

 

[hokiefyd]

I very much appreciate your time and pictures dedicated to this. Thank you!

 

[OhSix]

OK, the end of the geek rope has been reached. Taken this inspection as far as tools and imagination allow. Last night I was looking into the OEM OTW cross section and was seeing variations in the fluid passages that seemed odd. I really wanted a better idea of whats going on inside there, but cutting was distorting the surface and interior of the channels. After speaking to my pal with the water jet about cutting a cross section, it was determined turbulence would damage/distort the tiny veins inside the passages. So that was off the table.

Before leaving for the office this AM, a thought bubble appeared over my head: "cross cut the tube port!" That way there would be a clear view into unaltered passages. TADA.

These images were taken with an inexpensive AVEN USB microscope. What I thought I was seeing thru a jewelers loop turned out to be even more complex that imagined. Each passage looks to contain a wild staggered array of U channels. It occurs to me fluid passing thru these channels must have some pretty intense pressure behind them. And they are so small, any gunk in the trans fluid is definitely going to lodged in here.

Fascinating!



Edit: Adding this image:



For reference, here's a close up of the grating inside the Spectra OTW.




Geek, over and out.

 

[Dnick]

My brain hurts.......