>
       > Hi Paul,
       >
       >
       > You may be aware of serious overheating problems on the RX8.
       > Putting a turbo on exacerbates this. We did one for Mazda and,
      although
       > it can work if you are VERY careful, there are systemic
      weaknesses that
       > a larger radiator does not address. I have no problem with turboing
       > the engine, but until someone figures out a way to cool it (I
      have tried
       > several aero devices without enough success), It is a poor idea in
       > my mind.
       >
       > Jim
       >
       > ----------------------------------------------------------
       >
       > I was unaware of any cooling problems on the RX8. My 2003 stick has
       > 30,000 miles on it and I have never ever experienced the slightest
       > over heating. Under what conditions does it occur? Idle? City
       > driving? Or high speed? In my previous five rotary powered
       > cars that I have owned, starting with my new RX2 in 1973, I
       > occasionally experienced cooling problems. So far no cooling problems
       > at all with the RX8. No other problems either since they fixed
       > the flooding on start problem up with a flash to the PCM.
       >
       > I see some mistakes in the RX8 cooling system design but no
       > more so than some other new cars. I also see some improvements
       > over the RX7. The frontal area of the rad core is larger
       > and the core thinner. That is an improvement. The rad is laid
       > over about 30 degrees I would guess. This allowed the larger
       > core frontal area. I see some improvements in the RX8 water pump
       > compared to the 3rd gen water pumps as well. Less restriction
       > in the water flow coming out of the block.
       >
       > IMHO cooling mistakes are as follows: The duct feeding air to the
       > rad is not sealed. The duct shape is not of the Kuchemann and
       > Weber streamlined diffuser design. Namely trumpet shaped.
       > The back of the rad air path is restricted by the battery box and
       > the air filter. It could use an air vent in the hood placed
       > directly over the battery box and air filter if those objects
       > were not placed there. Getting free flowing air out of the
       > back of a rad is as important as getting air in the front.
       >
       > Scott and Harley, have you guys had any cooling problems with
       > your RX8s?
       >
       > The bottom line is the metal temperature within 1 mm
       > of the combustion chamber just below the lower spark plug.
       > Sort of cylinder head temp.
       >
       > I have written a small book on the subject of cooling
       > rotary powered airplanes. Here it is in html format.
       >
       > http://www.rotaryeng.net/how-to-cool12.html
       >
       > We have been through hell cooling the rotary
       > in airplanes for the last seven years but we are asking
       > for (and getting) a continuous 150 to 200 HP hour in and hour out.
       > The aircraft cooling system must be designed and done right.
       >
       > Paul Lamar ...No rotor no motor.
       >
       > Hi Paul,
       >
       > I don't know how you monitor the eng cool temp but you cannot use
       > the stock panel gage - it stops moving about 165 F and doesn't start
       > again until 205~210 F. If you see any movement above the "normal"
       > range, your engine is seriously overheated. Mazda has bought back a
       > number of RX8's in Vegas for engine failures. We did a considerable
       > amount of testing and on a 93 F OAT day it is easy to see 215 F
      Eng Cool
       > Temp. After a lot of testing, I am convinced at one large obstacle is
       > the lack of an engine driven fan - noisy, but powerful. The FD
      was much
       > the same. The FC never had a serious problem. We have tried turning
       > vanes, lip spoilers and closing the underside vents with minimal
       > effect. In our RX8 flash, we move the electric cooling fan on temps
       > from 98/101C to about 8 C lower. This helps avoid heat build-up but
       > does not cure the problem.
       >
       > Jim
       >
       > -------------------------------------------------------
       > A thicker rad is harder to blow air through. Only helps
       > if you are doing 200 MPH.
       >
       > Sounds like the gage is defective. Is Mazda fixing that?
       > I have never seen mine move beyond the half way point.
       > Do I need to install an aux temp gage? Do you sell anything
       > that will work? If not do you have any recommendations for
       > parts that will work and installation instructions?
       >
       > I think I have a DVM around with a temp function.
       > I'll see if I can hook it up to my RX8. I know I have a tire
       > temp gage but the cable is not long enough to reach into
       > the cockpit.
       >
       > You are right about elect rad fans in general. They are wimpy.
       > Time to check the volume flow of those fans. Also check the
       > amp drain on the stock fans. A 20 amp fan is only .36 HP electrical
       > HP in. Net mechanical HP is only about .3.
       > Here are some specs on the Spal fans that Ferrari uses I think.
       > First attachment.
       >
       > Sounds like the electric water pump thing all over again.
       >
       > Paul Lamar ...No rotor no motor.

      Jim, I just thought of something. If the CAN turns on the RX8
      fan without a relay, putting more powerful (higher current drain)
      fans in there might blow the FETs (transistors) or the relay.
      In that case it seems like the simplest thing to do is use a temp
      switch many elect fan kits come with. Have you checked the current
      drain on the stock RX8 fans? If ten amps or so a twice as powerful
      (20 amp) Spal fan is going to help.

      Paul Lamar ...No rotor no motor.

      Hi Paul,

          The CAN bus does not run the fans.  The signal comes directly
      out of the box, to a set of relays.

      Jim


That is a good sign. If the 5 volt relays blow with a higher
current fan they can be replaced cheaply unlike the PCM.