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Originally Posted by Ron O, 1984/2010 IM, B.C. Canada:

If it had an air cooled engine you'd be saying,"air jets plugged here.....got towed there.........strange noises everywhere."

Whoops, I didn't read your post correctly.  I thought you drove your new speedster 2800 miles in four days.

Where is the radiator?

I think Phil's statement above regarding rad placement oversimplifies the problem.  On a car designed for front engine and a radiator, it's a no-brainer, since there will be a grill or opening of some kind to allow unobstructed air to pass through the radiator.  In addition, with modern, after-market rads, fan shrouds force all the air to pass through the rad, increasing cooling efficiency, due to better design and fan efficiency.

 

Same goes for top mount inter coolers on Subi's.  The ram effect of a hood scoop increases air flow, which increases cooling potential.  With rear or mid engine mounting, those options are eliminated.  It may be possible to enlarge the horn grills significantly for sufficient air flow to qualify as a ram effect, but you still add lots of water tubing, water volume and weight, and the air inlets are small.  Since our cars are low, placing an unobstructed rad below the body is asking for road damage.

 

That would seem to leave the rear of the car for radiator and/or inter cooler placement.  Modern, after market rads, like Ron Davis and others make, offer cross flow contruction, efficient heat removal, bar & tube construction, and pressurized, aluminum end tanks.  Couple that with 2.5" silicone hose to reduce friction loss, a t-stat on the rad suction side, and efficient ceramic coating on exhaust components, and you have significantly reduced under hood temps.

 

Heat soak in stop n go after coming up to temp is the ultimate trial to determine engine temp efficiency.  For turbo engines, it becomes even more of a challenge, due to turbo heat.  A turbo blanket is a necessity, and it also helps to have the hot side of the turbo ceramic-coated, as well as up & down pipes, headers, and exhaust.

 

It is evident that Porsche partially solved the problem by adding fender vents using a NACA duct style of inlet and tubing.  To my mind, it's an interesting, but annoying, problem, since much of it seems counter-intuitive to a layman, such as myself.  Fluid dynamics, air boundaries, laminar flow, etc, and the choices of blowing vs. sucking (WHOA, easy, Vince) air into or out of the engine compartment are beyond most of out testing abilities.  Am I going to cut out a fender section for a test regarding air dynamics?  Not at present, but it may come to that.  I have tried to follow the conversation on several websites, but I don't have a science background, so I get lost in the explanations.

 

There is no cookie cutter answer.  We need to do 2 things: reduce engine heat on the output side by enclosing it in the exhaust system and keeping it in the exhaust pipe, and get more fresh, ambient temp air into the engine compartment.  Since almost all of us want to increase available HP by tuning, bolt-on's, or rebuilds, excess engine heat is a given.  Maybe one of us will stumble across an answer.  I know this much: if the answer was simple, we would all know it by now.  

got most of the mahogany in last night and this morning--then took 180 mile ride-she ran great-lots of power-handled well--I might have my left leg removed--nice sound-the VS motor in my last car was much louder- I much prefer this Subie motor-- shake from the rear at 70-80 Ill have the rear wheels re- balanced, hi beam indicator light not working--no storage clip for the prop rod-haven't figured out the radio yet-also needs an amp--

I only inquire about radiator location because of a disappointing result I had with my Suby Spyder.   I had the first Vintage Spyder ever built with a Suby in 2003. Radiator was mounted in the back  with 2 large fans pushing air out of the 2 grills in the rear bonnet. In traffic or at cruising speeds the temp was fine. However I set the car up to race with 4 point restraints role bar etc.  When I took the car out to the track it would always overheat. I switched the radiator so it would pull air into the engine compartment. Same thing. During aggressive high rpm driving it would not cool. BTW had my first Spyder with the air cooled 1915 on the track a couple times with no cooling problem.  Greg Leach at Vintage now puts all radiators in the front. Beck also puts Spyder radiators in front.  I know Henry at IM puts radiators in front. I am curious about the Beck, Vintage and JPS water cooled cars. Are the radiators going in the front like Porsche and God intended?  I don't know but I would like to. I talked to the owner of SAS about buying an outlaw speedster before I realized I'd be collecting social security before I got the car. I was very impressed about all aspects except about the radiator placement in the wheel wells. I know that SAS folks with turbo engines have had cooling problems.  I firmly believe that anyone with a non turbo engine who does not engage in aggressive high rpm driving will have no problem with a rear mounted radiator that has powerful electric fans. However those who wish to push their engines to the limit will require a front mounted cooling system...IMHO. 

So, is the rad mounted horizontally, in front of the front suspension beam?

If so, is there a protecting grill between it and the road?

I imagine the fans are mounted on the top and are pullers?  If so, where do the vent to?

What's the ground clearance under the rad?

Ted, sorry for so many questions-I'm curious and may go this route on another project.

 

FWIW, here's a couple of pics of my front rad. It's a mid '90's Saab rad mounted to welded brackets between the bumper support brackets. I built a rough aluminum box with integral vanes to ensure cooling air got distributed to the full surface of the rad face, fore and aft and left to right. The rad is mounted a little off horizontal with the front end up about three inches. Two 9" fans pull air up thru the rad. Two 1 1/2" aluminum tubes bring coolant from the stock Soob coolant manifold outlet up to the front and it must hurdle up and over the front torsion beam. Likewise, the return line must hurdle the axle beam and runs back then over to the stock Soob stat housing. For this reason, bleeder screws are fitted on either side at the high points over the front beam. I put a bleeder on the highest point of the coolant manifold too, like shown in Jerry's engine pics.

 

I fitted a heater too and it's up just on the front side of the engine firewall behind the rear seat back. It also has a bleeder. There is plenty of turbulent air up there and even without the heater fan on, it blows plenty of heat into the cabin through outlets on the rear bulkheads just behind your hip location when seated.

 

One must understand that the Soob's stat location is on the coolant "inbound" side of things rather than the "hot coolant going out " side of things. To that end, the thermostat must feel an unobstructed supply of heated coolant to do it's job properly. On a Subaru car, the coolant flows directly from the engine through the heater core then directly back to the stat as I understand it. For that reason, my heater coolant runs full time. There are several fixes for this and one is an aftermarket thermostat housing built and supplied by Bill Shiels. Google his name. He discovered that in cooler climates, the front mounted radiator and the heater ( another radiator really ) cooled the coolant too much and tricked the thermostat into closing more than it should, thus the engine needed cool coolant but the stat would not supply it.

 

My car is a driver, not a show car and the quality of the components and workmanship thru this testing of cooling systems and it's various iterations shows it. YMMV

 

 

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  • Speedster cooling April 2014
Last edited by David Stroud IM Roadster D
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