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Posted by: SLITS Feb 19 2007, 01:50 PM

I have been told by a budding engineer type that using the Mazda RX7 Oil Cooler with internal thermostat will require removal of the thermostat.

My question is WHY?

The thermostat bypasses the cooler until operating temp is reached, so what is the difference between the internal one and an external one?

Oh, cooler will be installed on the scavenge line of a /6 as if it makes any difference.

Posted by: RON S. Feb 19 2007, 03:17 PM

Slits,

I am no expert on heat transfer,but I did acquire several xr7 coolers.


I cut one of them open for the same reason,and I found that the thermostat is a pretty big restriction if you cut it apart and look at it up close.

All the oil that passes thru it goes thru a hole less than 1/2" diameter.Also,every other tube has a aluminum strip thru it to slow oil flow even further.

I gutted mine and made removable end caps but I left the restriction strips still in the tubes.


If mine ever starts to run to hot,I will remove a few of the strips allowing more flow thru the cooler to help things out.

Also,if the oil is allowed to heat up to 180deg. up front at the cooler,how hot will it be up to back at the engine.

here's some pics of my setup.

Ron


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Posted by: PRS914-6 Feb 19 2007, 04:00 PM

I'm with Ron. This topic has been brought up before, that is where to mount the components of an oil system. I'm no expert but I like the thermostat mounted as close to the engine oil outlet as possible. That way you get the fastest response time after a hard run. Maybe I'm anal....

Posted by: SLITS Feb 19 2007, 04:14 PM

Thanks Ron ..... your cutaway shows what I wanted to know.

Most of the thermostats on the market I see are 1/2" and as such would present a restriction anyway.

When I was looking for this cooler, I was actually wanting an early RX 4 / 7 without the thermostat, but for $26 I couldn't pass it up.

I see that you must have been talking to Trekkor and visiting Home Depot (reference is the 1/2" pipe elbows).

The "strips" you mention are just for the purpose you described ..... to slow the fluid down allowing a longer contact time with the tube wall and in theory to enhance heat transfer. Same technology is used in many heat transfer devices.

It can also cause a breakup of laminar flow characteristics where the fluid molecules are attracted to the metal and form a barrier that doesn't move decreasing heat transfer of the flowing fluid ..... but that is just an interpolation on my part.

Posted by: Aaron Cox Feb 19 2007, 04:18 PM

yup... what they/you said.

my thermo stat is basically at the engine...
circulate less cold oil all the way to the front on startup, and i believe that makes it warm up faster.....

how you is ronster?

Posted by: burton73 Feb 19 2007, 05:05 PM

This is today from the hole. The thermo says Trottman on top. I think it is a thermostat or just a nice connecter box. What you see the 3 blue AN’s going into. All there is, is braded stainless up to the factory GT cooler. The cooler has male fittings for the AN’s

Bob



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Posted by: SLITS Feb 19 2007, 07:07 PM

I be well ..... tanks .....

Posted by: Crazyhippy Feb 19 2007, 07:36 PM

If you're gonna put a radiator up front, why not put some HP in the back??

Muahahahahaha.....

Posted by: plymouth37 Feb 19 2007, 08:35 PM

Posted by: kconway Feb 20 2007, 12:01 AM

Ron,
You blog says your done, your unloading that engine. Change of heart I hope.

Posted by: Twystd1 Feb 20 2007, 02:31 AM

Ronster...

I will reiterate what I said at Sharps... Toss the the little Mazda Bastid.
(Sell it to Howard. If it's really shiny.. he will buy it)

You can find a REAL cooler with the appropriate sized ends on it without the inherent restrictions of the RX-7 cooler easily.

Used is good.....

And you will still have to get it professionally ultra sonicly cleaned if it's used. Just like the Mazda cooler needs to be.

AND...... If'n ya run the cooler up front. I B thinking your oil temp problems will disappear.

I know you don't want to spend the bucks... or the time to do this.

OK....

Let me take you back to the old SCCA days when we were both running cars.

I remember that most of the DNFs that we all had......
Was when we cheaped out on one or two little things... And it came back to bite us in the ass......

This is another one of those times.... IMHO.

I B thinking you CAN swap sumpin out of your hoard to make a break even deal for all the goody's you need to do a complete front mounted cooler setup with a troutman T-Stat and all the goody's.

And if all of that doesn't work... No problems... Blame it on Eric or Aaron... I do.

I am here to help ya wrench it in if you ever ask... So ask dammit... I want an opportunity to give back.... Anyway your old and ugly... you need the help...

Claytonovich... East of Krackatoa

Posted by: michel richard Feb 20 2007, 09:46 AM

FWIW, I used a Mazda cooler too. Here's a thread I had on the subject. I ended up cutting a whole end off, and having a new one welded on. You do need to make sure there's a baffle in the end between the two connection fittings, to make sure the oil is forced through the radiator and does not simpluy use a shortcut inside the "end box"

http://www.914world.com/bbs2/index.php?act=ST&f=2&t=44825&hl=

Michel

Posted by: Matt Romanowski Feb 20 2007, 02:07 PM

Why do we have such a fascination with Mazda's ability to cool oil?

I would say buy a Mocal, Setrab, whatever that is the right size, with the right AN fittings, with the right mounting tabs, with the right flow...

With all the money and time everyone spends on hacking together a Mazda unit, you could have a real one.

Posted by: burton73 Feb 20 2007, 02:35 PM

Why did they put an angle on the opposite end from the fittings? To make to oil flow easier? The real deal it came with my car but how much does it cost?

Bob



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Posted by: nein14 Feb 20 2007, 02:55 PM

I recently scored a brand new RX-7 oil cooler, the drain plug when removed exposes the thermostat which can just be pulled out.

As far as it fitting in a GT shroud, the cooler is wider than the shroud and one hole is in the wrong place so I closed one of the side holes and put a new one on the top. Then split the fiberglass GT shroud down the middle and added a 2" piece of aluminum bent to the contour of the fiberglass and bonded the two 1/2's of the shroud to the aluminum and resined over the metal.

Posted by: michel richard Feb 20 2007, 03:01 PM

The fascination with the Mazda cooler, IMHO, is because it is really really close to the right size (within a quarter inch or so, in most respects) it is the same type of construction as the original coolers, it is readily available for cheap and can be modified fairly easily.

No doubt it ends up being not much cheaper than buying a new one, but there are other advantages, as noted above.

Michel

Posted by: Eric_Shea Feb 20 2007, 03:05 PM

Wiener...

Posted by: SLITS Feb 20 2007, 03:12 PM

Porcupine Penis Dick

Posted by: Twystd1 Feb 20 2007, 07:06 PM

I am not a dick...

Well.. Ok ........ Maybe....

It's still not my fault........

C