Date: Sat, 29 Jun 2002 08:22:13 -0500
Reply-To: Stan Wilder <wilden1@JUNO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stan Wilder <wilden1@JUNO.COM>
Subject: Re: RX7 Aux Oil Cooler install...results Aircooled vanagon
Content-Type: text/plain; charset=us-ascii
I want to thank your for your in depth reply to this posting.
We've finally got some useful information into the archives that can be
used by several of the other people that are currently and will be trying
out this cooler.
If I have asked the right questions; your reply will be helpful in
guiding their installation.
I'm well satisfied with the operation of the RX7 cooler but am thinking
of adding a fan of sorts.
Since the results of changes in the cooler operation take as much as ten
minutes to register on the temperature gauge, it still holds some mystery
to me.
I'm confident that I'm consistently getting oil delivery in the 200
degree (f) range once my engine develops full operating temperatures. I'm
confident that the cooler is working very good at highway speeds under
intense loads as it maintains temperatures in the 220/230 range under the
harshest conditions (95 degrees so far) and 23 to 35 mph head winds for
two or more hours.
The proof of this thing will show when the temperatures here reach into
the 110 Degrees (f) range.
I never was shooting for refrigerated oil but just oil at the proper
temperatures to get full cycle out of the synthetic oils I'm now running.
The *Martha Stewart* candy thermometer readings was a real eye opener for
me since it gave me "here and now readings" after a long hill climb or
head wind assault. Previously I was waiting for ten minutes to get my
temperature readings.
Stan Wilder
On Sat, 29 Jun 2002 01:19:29 EDT Frank Grunthaner <FrankGRUN@AOL.COM>
writes:
> Stan,
>
> I'll try to answer some of the questions below. I'll precede my
> comments with
> $$!
> In a message dated 6/28/02 12:31:41 PM, wilden1@juno.com writes:
>
> << OK Frank now that we've got you on the soap box, I've got a few
> statements and then questions about this RX7 cooler I've been
> raving
> about.
> #1) Are you using the 148 degree (f) thermostat that comes in it.?
>
> $$ Yep, just fine by me! In my experience, 148 is the beginning of
> the bypass
> close and at 160 F it is fully closed. So I refer to it as a 160 F
> bypass
> thermostat.
>
> #2) The little plunger pushes the thermostat to position one cooling
> at
> 148 degrees (I boiled mine and it works) and directs oil through
> stage
> one in the cooler, the other oil surplus bypasses, True?
>
> $$ Well, close. The Mazda cooler has an entry chamber and an exit
> chamber
> which are coupled two ways. There is a bypass valve between the two
> chambers
> that is activated by temperature and pressure. The chambers are
> also
> connected to the crossflow radiator channels. So at all times, there
> are two
> parallel pathways for oil to flow - across the bypass and down the
> radiator
> circuit. The radiator channels are not just open tubes - they have
> a
> corrugated spring sheet inside to generate turbulence as the oil
> flows down
> the tubes. This increases the efficiency of thermal exchange when
> the oil is
> hot but really adds flow resistance at high viscosity. So, when
> cold, the
> bypass is fully open, 2 to 5% of the oil flows across the radiator
> and the
> remainder goes through the bypass port. As the oil temp exceeds
> 148-150 F,
> the bypass valve enters into the bypass port cutting down the
> effective
> diameter and therefore the flow. Now the bypass flow resistance
> increases,
> the viscosity is lower and perhaps 25% of the oil makes its way
> through the
> cooler radiator section. When the bypass valve is fully extended, the
> port is
> really occluded and as much as 90% of the flow is through the
> radiator
> cooling circuit. The spring and plate now help seal the bypass port.
> But if
> the oil pressure goes too high on the inlet side, the bypass port
> will be
> forced open again. I've stressed the end points, but the flow
> partition
> between the cooler and bypass circuit is a continuously varying
> function.
> Blither!
>
> #3) The RX7 Engine generates a full 60 psi at rpms over 2000 so it
> pushed
> the thermostat plunger to position two and actuates stage two of
> the
> cooler (but the spring causes the plunger to vacillate on my Westy
> that
> just puts out 48 Psi at 2400 rpms) giving me needle bump on the
> gauge.
> Normal ?
>
> $$ I never got around to measuring the oil pressure relief spring
> opening
> point. But throughout much of its operating range, the RX-7 exceeds
> 75 psi.
> This pressure relief is for safety reasons - not to overpressurize
> the
> cooling coil circuit and to pass oil in case the cooling circuit is
> blocked.
> It is not clear to me that the pressure relief valve has been
> actuated on my
> system which goes to 90 psi cold. I don't agree with your view of
> the
> operation here. But, I am doing this all off the top of the head, so
> won't be
> the first time I'm wrong. Nonetheless I get damn good cooling at 35
> psi.
>
> #4) Stans going full bore now at 70 mph, 3300 rpms and ginning out
> 60+
> psi and the third stage and full capacity of the cooler is active,
> True?
>
> $$ I would say that if Stan is processing Aluminum at 70 mph and his
> oil
> temperature is above 160 F, he is using the full capacity of the oil
> cooler.
>
> #5) Does the cooler still bypass some oil when the temperature is
> +160
> degrees (f) and the oil pressure is up in the 60 Psi range ?
>
> $$ Oil cooler always bypasses a small amount of oil at extreme
> temperatures .
> The closure between chambers is not a hard valve.
>
> The reason I ask these questions is that removed the thermostat and
> I
> tried a bolt between the inlet and outlet chamber and didn't get
> any
> better results than with the thermostat. I can only assume that the
> bypass ports were still open. Since this wasn't a junk cooler I
> didn't
> jury rig any slip in tubes or plugging devices to seal them off.
> Got a way to make it full bore cooling all the time?
>
> $$ Been there, done that. I put together a Viton O-ring seal and
> bolt so I
> could measure the pressure drop across the cooler as a function of
> temperature. In my current system, I have thermal probes at the
> entrance and
> exit of the cooler. I also have mounted pressure taps as well on
> occasion.
> With the temperature probes, it is very easy to see when the cooler
> turns on.
> The temperature difference first begins at about 150 F, is up to 10
> degrees
> by 155 and up to 35 degrees by 165. The pressure measurements were
> confusing,
> being related to both temperature and viscosity. More about pressure
> drops
> later.
>
> Its 98 here in Dallas and I know it won't hurt to have 100%
> capacity
>
> $$ Yeah, then Corpus (HOE) must be 108!
>
> useable soon. >>
>
> Frank Grunthaner
>
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