|
|
On 19 Mar 2003, at 17:17, 13brv3@mchsi.com wrote:
SNIP
My current question, is about oil/water heat exchangers. It
seems
that I've read where someone tried this, and gave up on it, but I
can't think of who that was, or how hard they tried to make it work. In other words, did they just try an existing auto trans cooler, or
did they have something special built. Does anyone know any
specifics?
Hi Rusty,
Funily enough, I have done JUST that with our road going tarmac rally car. (See attached pic). Over on the left guard you will see a big rectangular box. That houses a bar & plate oil/water heat exchanger. This was proof of concept - the car is currently in bits and the body is at the 'beaters getting IMSA flare kit and a new [paint job. The plumbing will all be done in braided SpeedFlow hose and fittings when re-assembled. (The photo shows it with cobbled together with ordinary rubber hose and ends). It is also getting an FD engine and a new inlet manifold and thpottle body, and 10:1 RX8 rotors. Plan is to mount the heat exchanger across wise between the radiator the front of the engine. The mechanical water pump is going and will be replaced by an EWP. Thenew fibre bonnet will have a duct to vent the cooling iar from the rad upwards.
The oil/water heat exchanger has it's own separate booster pump that is actuated at times of prolonged and severe load. It is necessarily large as the engine puts out 650 BHP at full noise. It has 2 "V Spec" GTR ball bearing turbos - one per rotor. they spool up a lot quicker and the is little turbo lag - current rotors are 9.4:1.
I chose this method as mounting 2 separate water & oil heat exchangers was a pain and quite complicated, especially getting air through the oil cooler. . It also allowed me to use one HUGE radiator, and made the ducting a lot simpler. (The car also has a HUGE Nissan GTR sized bar & plate intercooler down the front) so air flow and space was at a premium.
Other advantages of water/oil heat exchangers is that the engine warmup is FAR more rapid, the oil & water always stay at the same temp (more or less anyway) and particularly in sub zero early winter mornings (even in Sydney, we often have temps down to -3 -5 Deg C in Winter - moreover, up in the Blue Mountains and on the Western Slopes, it has been known to make choir boys from alloy anthropoid apes!!). Tasmania can be even worse!! And I can't really have "cowl flaps" (}:>) on a race car!!
So using a properly engineered oil/water heat exchanger allows the engine to run at it's optimum design temp.(If you use a thermostat that is!!).
Of course, all of this is either extremely "revisionist", "radical", "extemist" or "revolutionary' thinking (depending on your current mind-set). To be sure, it would be "anathema' to SOME+ of the more influential mathematically challenged rocket scientists of that "other" place. However, as I have already been pronounced a heretic, (and a lunatic!) and suffered the wrath of HIM on more than one occasion, AND have recently been summarily ex-communicated from the ACRE communion, further heresy won't matter a damn!. Now I feel comforted in knowing that we have a "broad church" here, that will tolerate other heretical ideas like "Plugs Up" and EWPs, so I feel safe from any inquisition of latter day Troquemadas. So I shall expound the new doctrine and see if I can pick up a few proselytes!! (}:>)
My current (laternal) thinking for aircraft use is to use an evaporator core IN the sump (custom made of course), and run the oil OVER the outside of it (where the air normally goes - this will also assist in de-aerating the oil). This has the added advantage of acting as a baffle to discourage oil surge in the sump. The water is then run THROUGH the evap cooler where the gas normally goes.
Now this means that you only need external WATER heat exchanger(s), and there is no need for 70 -90 PSI hi pressure oil lines running all over the engine bay to burst, spray oil everywhere, and catch fire (I keep on thinking of poor Chuck Halbert and his Velocity problems - part of this idea was in response to Chuck's experiences). So one simple pressure PIPE from the font cover to the back housing is all that is necessary. It also cuts down on the number of sharp bends and fittings which also add to the oil temp. (Somebody pointed that out some time ago - the racers always try to use smooth fittings, not banjo bolts - every 90 degree bend causse tutbulence, and creats heat and a pressure drop).
For sure, it does mean that the water radiator(s) must be bigger in capacity to reject ALL the engine heat, but is NO bigger than the COMBINED area of the water and oil coolers together.. Have a look at the Series III ('83 - '85) RX7 setup. They have a full length rad and a small oil'water unit between the back housing filter mount and the filter. Works a dream (at least on a road car). I have one on my "mule', and my good lady June's car as well (It's a series I '79 model brought up to later specs with an '89 NA engine).
Anyway, have a careful think about this.. As always, I'm happy to accept peer review, and if my ideas are indeed "beyond the Pale', I shall always be ready to recant and seek absolution from my fellow experimenters!
Cheers all,
Leon
Best Wishes & Kindest Regards,
Leon Promet
Aerota.com
leon@aerota.com
0408 223 675
The following section of this message contains a file attachment
prepared for transmission using the Internet MIME message format.
If you are using Pegasus Mail, or any another MIME-compliant system,
you should be able to save it or view it from within your mailer.
If you cannot, please ask your system administrator for assistance.
---- File information -----------
File: RD7EngiBay7OS.jpg
Date: 1 Jan 2003, 16:34
Size: 90721 bytes.
Type: JPEG-image
|
|