HV Transaxle cooler/filter

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There was some discussion recently here and offline into the feasibility of a transmission cooler. I made one and it works but I am not totaly convinced of the need at this point (lack of unit failures). I did make an added bonus to the system with the use of an external sediment filter. The filter is clear so fluid color and condition can be easilly assessed during the 5k service. The installation time is about 40 minutes with no special tools, and only basic mechanical aptitude. It's on par with an EV switch. The ambient temps today were 75ish, low humidity. Test vehicle, 01 prius 74K. After a 45 minute road test at lunch and another after work, it seemd to cool MG2 by about 8-15 degrees over yesterday's run. Not very scientific I know. The oil is definately cooler...130 going out, 95 going in using digital thermometer. Does it work to keep MG2 cool? I think so. Is the oil cooler? Yes. Is it easier to keep clean? Yes. If the filter plugs will my gears starve for oil? No. Wiil the oil get to cold in winter? No.

Some initial pics.........
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Run the lines behind the radiator support.

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There was room for a filter so...

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Oil pump location, 4 screws removed to take splash shield out

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Version 1.0a

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This filter requires changing, and the oil needs serviced. Visual inspection at a 5k intervals prevent the "crude oil" look some Prius have experienced.

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This oil is clean.

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Oil will flow thru this drive shaft and help cool MG2 PM and bearings.

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Oil exits the planet carrier shaft and lubes the pinions (port is hidden from view), and MG1 sun gear, inner and outer bushings.

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Oil level is about 20mm below (to the right) of my hand and helps cool the windings, and lubricate the differential assembly and SDC. Your Input requested.

Regards, Mike

 

I agree. MG2 already seems to run 15* cooler than MG1. Now it's 20-30*. Inverter temps seem to spike easy, but come right back down. Circulating the oil should help to cool the oil and thus lower winding temps, but probably will have no affect on case or inverter temps. It's just not that big of a system. Belt/suspenders is funny, I was thinking maytag repair guy that came up with a better dryer sheet. I'm not sure this qualifies for belt status because belts work by themselves.

I think (FWIW) that extended ev will not be an issue. The diff carrier sits immersed in oil, so the SDC should sling oil onto the Planet assy anytime the veh is moving ice on or off.

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Looks like a far better idea for cooling, but I like being able to see the oil, sticking a finger in the hole is hard to get a good color reading. You have probably more time looking at prius data than anyone else including Toyota techs (me). We are after specific problems or working on camrys. I especially appreciate your input Doc.
Regards, Mike

The cooler is not higher than OEM oil level, so drainback should not be an issue. It took .6 quarts extra.
Regards, Mike

I went sorta cheap on the first one because I bought the parts for my customer ( sans oil) so I went with rubber oil hose. There is a bypass mod in the pump so that if a line got pinched you will not starve it for oil. I used a plastic A/T valve body check ball from old previa vans and the dual stage sping found under the flint in a bic lighter. I was quite scared of this actually, starving the guts that is.
Regards, Mike

 

<div class='quotetop'>QUOTE(sub3marathonman @ May 17 2006, 06:21 AM) [snapback]256800[/snapback]</div>

There is one plug (bolt) for checking oil presure...all blistering 5-13 psi of it. I replaced that with a cold start injector bolt from a 22re or 3vze I'm not sure. I then put a cold start fuel line on it and connected a hose. The second hose home needed drilled and tapped to accept my new fitting, modified an internal pump passage and there it is. First one in captivity. It cost me $7 for the bolt, 5 for a fitting, the cold start line was floating around here. The cooler and hoses were $36. Pretty cheap mod...wish it worked better, but it still has some upsides to it I think. The customer is a great guy, and has multiple hybrids. I think this Prius was one of the first the dealer sold. I appreciate everyones input.
Regards, Mike

 

<div class='quotetop'>QUOTE(rick57 @ May 17 2006, 08:40 PM) [snapback]257313[/snapback]</div>

(Long response)

I started to see a few Pri's with dark oil on my finger at lower than expected mileage. Hdrygas who is a local to me, posted not long ago about the same thing. I was recently at a Toyota new model class and some of us were talking about it there in a side conversation. Turning dark has no established pattern as to use yet. Some cars have had EV mods and others without and low MPG history. Often that is an indication of less load in the motors and more ICE time than EV + Pulse and Glide folks. There is no indication at this time that P&G is harder on anything yet.

My observations have been that it looks "not good" on the finger and "horrible" when drained. It gets dark purple or even black once it starts to come out. You can see what appears to be trace metal in it because it sparkles in the light. In my 22 years (15 at this dealership), I have noted this: not all toyota transmissions that look this way fail, but all that fail look this way. Camry, corrola, sienna, van...they all had the silver flake in the oil. So Prius oil is expensive, but labor is cheap. It's an easy DIY for those that do. My logic would follow that its a good idea to exchange the fluid, Prius or other platform. The box has a strainer but no filter, and several small wafer magnets the size of a nickel. The only MG2 magnet I have seen also had metal on it.

The common thread may end up to be the differential failing and contaminating the oil. This is not the customers symptom of failed yoda fwd boxes but it is usually the root cause. I was the only tranny guy the shop had for many years. I am still the go to question guy and if it an A/T gets O/H I did it. I have more experience inside toyota and GM transmissions than 95% of the "technicians" out there. Simple cure is to change the oil early and often. 30k would not be a bad idea and definitely by 60K is what I am starting to think. Differentials, by their nature, must make metal. Unfortunately the metal is such a fine powder it never comes out of solution and settles in the pan. The magnets do what they can as it floats past. Valve body and cast hard parts but not the aluminium case is where you find most of the the grey film. I think all the magnets do is polarize the metallic oil. An easily changed filter might capture some of this. You can now flat tow your prius with an electric pump and my system behind your diesel pusher RV. :lol:


There has always been tempered concern with inverter temprature spikes for those that have the ability to see the data (buy a can-view now!!). The heat created in the use and generation of the amperage is dumped to the case to be cooled via air , oil, and primarily by a dedicated cooling system. There are cooling system mods for both cooling and mpg. Frank has a classic mod for mpg that I love. Henry's Gen 2 mpg mod is stealthy like the car. The oil cooler and filter mod I tried was an attempt to address ease of accurate 5k fluid inspection as well as case cooling. I think one worked well and one so-so. I am going to have him come back in a few weeks or 1k. I might see if he is willing to make a R/T with a cell phone and THHS in each car on a good long run. Perhaps a local would come out to play, or I wait for a trade in. I can also shorten the cooler loop to a few inches total system length easily in the field. Thats what will probably happen. I need more scan time to look at nominal winding and inverter spike temps. Locally they seem to run warm but not hot, and everywhere they run a little hotter on MG1 side.

Actually it's an expensive, simple but well made box. I did not have my hopes up of improving much on the prius initial design. I don't think many will fail, but the fewer the better for us all. FWIW I did this off the clock and if the system fails, I will be FixenEm after hours with parts on my dime. Why did I do it? I like the product platform and many of the customers are fun to hang with.
Regards, Mike