Where to locate cooling inlet?

[ReynardF1000]

All,
A few years ago I built an F1000 from a Reynard that had been turned into a DSR. Confusing history but great fun and especially enjoyed building the project. Raced in the SF Region a few times with reasonable success. It's gone now and been replaced with an old fashion laydown roadracing kart.
I'm completely rebuilding the kart and installing a water-cooled gearbox engine.
The question is: Where to put the cooling intake and therefore radiator? I'm building/modifying a full body (wheels covered sports-racer style) with open cockpit area (required by rules).
1) My first thought is to install the radiator in the nose and allow the air to run past my feet and out of the open cockpit. The air will not be too hot, given 120F maximum water temp's. Testing indicated a 10 - 30F rise in air temp from front to rear of radiator. In this scenario air mass passing over/around the outside bodywork and possibly entering the cockpit opening would be reduced. Air mass to feed the very conservative rear diffuser would be very slightly reduced. There will be an ~3" splitter around the front nose.
2) A second approach is to locate the radiator ahead of the RL wheel and feed air from a side intake. Air would be fed from the high pressure, flat sided bodywork and exit past rotating axle, brake rotor, seat side, etc. to the rear, low pressure area of the kart.
3) A third approach is to locate the radiator at the very rear behind the driver's head. Air would be ducted by vents protuding into the airflow each side of the driver's head.
Of course, there are other mostly mechanical considerations involved with location and routing of coolant, but the first consideration is lowest drag.
Any thoughts or additional ideas?
Thanks,
Greg

[racerdad2]

Second option seems logical... I'm no engineer & dont play one on TV

[Steve Demeter]

Diffuser on a kart. Pretty sophisticated.

I have laways been told to locate air intakes in a high pressure area. Option 2.

[S Lathrop]

I cooled a water cooled FSV with radiators mounted at the end of the tub beside the engine and just forward of the rear wheels. The radiators were parallel to the center line of the car and several inches inboard of the wheels. That car cooled great. The air exited the radiators and passed out the rear of the car. This also gave good air flow through the engine compartment.

So I would vote for option 2. You might consider 2 thin radiators vs one thick one. I would think that 2 radiators that were not much higher than the tires and definitely below your shoulders would work best. I am assuming a very low driving position.

As to the front radiator, I don't see how you are not going to be in the radiator exhaust air. Now that might work fine for the few days you get snow at Willow Springs.

[Mike Devins]

Front option with the air passing thru the cockpit always scares me, if you have a radiator failure where does the hot water go!

[Neil_Roberts]

Here is what the wake from a front wheel well cutout looks like. The whole side of the kart is bathed in that wake, so the effectiveness of the cooling will be marginal.

Steve's water cooled SV approach worked because the car was an open wheeler, and the local flow direction near the tires is quite different from straight downstream. A sports racer type body does not do that.

My preference would be for an intake in the nose feeding a big flex hose routed through the bodywork to the radiator mounted near the engine. Next best would be a pitot scoop like these.

[flat tappet]

Here is what the wake from a front wheel well cutout looks like. The whole side of the kart is bathed in that wake, so the effectiveness of the cooling will be marginal.

Steve's water cooled SV approach worked because the car was an open wheeler, and the local flow direction near the tires is quite different from straight downstream. A sports racer type body does not do that.

My preference would be for an intake in the nose feeding a big flex hose routed through the bodywork to the radiator mounted near the engine. Next best would be a pitot scoop like these.

How are the rest of the folks with a laydown karts doing their cooling.Try going to the forums on ekartting and ask.

[ReynardF1000]

Thanks everyone for your thoughtfully replies.

Neil, Like the idea of front opening and ducting to rear radiator. If I can find enough area for ducting this would locate the radiator weight in the best location AND draw air from a high pressure area. The wheel wells are open under the bodywork. Don't know what the flow looks like. Plan to test wheel well openings on the top of the bodywork in the future. If the openings create less lift, therefore more load on front tires, I'll be able to tell if the air is free to flow, creating neutral lift.

Flat Tappet, I'm active on eKarting and have found the level of technical knowledge to far lower than here. Very few racers study technical information available in books and periodicals. That said, this application is not exactly like either an open wheel or closed wheel full size car and I don't have access to the technologies necessary (wind tunnel/CFD/100 channel logger) to gain the insights that is in the group of educated/experience people here at this site.

[flat tappet]

Thanks everyone for your thoughtfully replies.

Neil, Like the idea of front opening and ducting to rear radiator. If I can find enough area for ducting this would locate the radiator weight in the best location AND draw air from a high pressure area. The wheel wells are open under the bodywork. Don't know what the flow looks like. Plan to test wheel well openings on the top of the bodywork in the future. If the openings create less lift, therefore more load on front tires, I'll be able to tell if the air is free to flow, creating neutral lift.

Flat Tappet, I'm active on eKarting and have found the level of technical knowledge to far lower than here. Very few racers study technical information available in books and periodicals. That said, this application is not exactly like either an open wheel or closed wheel full size car and I don't have access to the technologies necessary (wind tunnel/CFD/100 channel logger) to gain the insights that is in the group of educated/experience people here at this site.

Don't know if this might help...but here are a bunch of pictures of a laydown kart that might help.

http://s189.beta.photobucket.com/use...17367255650872

[JLS Crossle 42]

Here is what the wake from a front wheel well cutout looks like. The whole side of the kart is bathed in that wake, so the effectiveness of the cooling will be marginal..

I have noticed that the radical SR3 uses side cooling intakes, I am doing a CSR and plan on using something similar, what you think?

[ReynardF1000]

Thanks Flat Tappet.
I like the front opening and will see if there's enough room for ducting from front to side mounted radiator.

[DaveW]

When I had that, IIRC, the cooling inlet was along the flat body side exiting through the body to the low pressure engine compartment. The inlet was rectangular, but similar in concept to a NACA duct. Again, IIRC, the radiator was at ~ a 30-degree angle to the sides (fins 60-degrees from direction of motion) and the inlet was shrouded so that the inlet area was ~ 1/3 of the radiator area.

This worked very well with a large thin radiator. Never had a cooling issue.

Photo of a similar Shrike inlet (not my car) from the Internet...

[John LaRue]

Years ago (1979 era) a very bright guy named Doug Henline built several H20 cooled karts. These are a couple of old photos. He located the radiator low behind the driver and to my knowledge never had cooling issues.

BTW, Doug began producing kart wheels and eventually founded Douglas Wheel (DWT) which I believe produces wheels for the F500 class.

[BURKY]

Very cool, knowledge...

[Smittty]

Hey Greg, Once had the opportunity to put my Reynard FC in a wind tunnel (if you are from Mestec, stop reading here...!) and was surprised by the results - not what I had imagined ....the tufts and smoke didn't lie. The home built, subaru conversion, aircraft guys have wrestled with this for years - in aviation they tend to be anal about testing and data collection, try searching them out for extensive articles/test logs. Opening size/mass airflow/turning vanes/ delta t and the like. Also remember what the fastest fish look like as you search out mounting locations! Do it, fix it, try it. Smitty

[Charles Livingston]

Here is what the wake from a front wheel well cutout looks like. The whole side of the kart is bathed in that wake, so the effectiveness of the cooling will be marginal.

Steve's water cooled SV approach worked because the car was an open wheeler, and the local flow direction near the tires is quite different from straight downstream. A sports racer type body does not do that.

My preference would be for an intake in the nose feeding a big flex hose routed through the bodywork to the radiator mounted near the engine. Next best would be a pitot scoop like these.

Every sports 2000 made after '86 or so has the side intake setup like the shrike (but with open-sided front wheels) referenced by Dave W. Lola's, Carbir, etc. These seem to work fine, what am I missing?
Charles

[Neil_Roberts]

Every sports 2000 made after '86 or so has the side intake setup ... These seem to work fine, what am I missing?
Charles

The main reason they work is the strong vacuum in the engine bay. That sucks in part of the wake through the radiator. Of course the radiator airflow that dumps into the engine bay is a giant leak that reduces downforce.

None of the current Le Mans prototype sports racers have side radiator inlets. That's an indication.

[DaveW]

The main reason they work is the strong vacuum in the engine bay. That sucks in part of the wake through the radiator. Of course the radiator airflow that dumps into the engine bay is a giant leak that reduces downforce.

None of the current Le Mans prototype sports racers have side radiator inlets. That's an indication.

When I ran the Shrike, it at first had no undertray. We made one out of aluminum. Even with that installed, and the large amount of drag reduction and rear downforce it produced, the side inlet still worked very well. The undertray covered the under-engine area and extended all the way to the rear, filling the area between the rear tires, but did not totally "seal" the bottom from the engine compartment.

[ReynardF1000]

Thanks everyone!
I really appreciate the ideas and theory/reasons why the ideas work. It sounds like "Horses for courses" and my horse is slightly different from each and all are compromises to fit the course.
Doug Henline's kart was very innovative and a friend had one of his engines on a different kart with rear mounted radiator. At the time, methanol was used at nearly 100%. With methanol's very large cooling effect, little cooling was required. One dual engine Hartman kart in that era layed its air-cooled engines out of the airflow and, with methanol, ran fine.
At the moment, I'm most likely to mount the radiator in front of my feet (~five pounds with H2O, hoses and mounts) with an ~40% (conservative) opening at the nose. Opening to radiator distance is 3 - 6 inches. If all works correctly, water temp is ~120F in and ~105F out and there will be a backside deflector directing flow upward to the opening above my feet.
There is very little room anywhere else in the footprint of the kart for ducting from front to rear, as I had hoped to use a front duct/rear radiator solution. Overall width is 42". Wheelbase is 45". Right side is engine with expansion chamber in front near floor, with pipes to direct exhaust through silencer to rear exit. Left side contains the 2.6 gallon fuel tank between the tires with a 12" opening between the rear of the tank and the front of the rear tire. In between these items is a seat ~15" wide. Bodywork is just above most of this "stuff". Water hose/pipe much easier to route than air ducting!
The rear diffuser is very conservative, fitting within the competition rules. The rules state that bellypans must not extend beyond the end of the rear main frame rails but nothing about frame rails that slope upwards...

[ReynardF1000]

Stan Clayton had a look yesterday (thanks, Stan!) and had his usual great insight into things aero.
Given the very tight packaging for fuel tank/engine/exhaust/driver, the radiator will most likely end up on the side with side ducting. With a total width of 38", there's very little room for anything but the essentials. As Stan said (paraphrazing), "race cars are just one big compromise".