1969 S2 Europa Hill climb car - 700whp Turbo Honda K24 swap

[Clifton]

There's a low pressure area on the front hood area, it's why every one with a choice vents the radiator out there. Same reason you see vents on top of wheel wells of prototype cars. GRM had a few airflow/drag/lift/downforce articles testing spliters, wings, hood vents, etc with CFD.

[Taimoshan]

There's a low pressure area on the front hood area, it's why every one with a choice vents the radiator out there. Same reason you see vents on top of wheel wells of prototype cars. GRM had a few airflow/drag/lift/downforce articles testing spliters, wings, hood vents, etc with CFD.

Not sure i entirely agree, however agree exiting into the low pressure through the top of the bonnet may draw air through the rads nicely , but it will also add air vol to the high speed air travelling over the car which adds lift, not what I am looking for. 

Exiting air under the car into the low pressure in the transition under the front cross member is also effective  for rad cooling and also adds to the high velocity air moving under the car's flat floor and therefore adds downforce (providing you don't use a front splitter to block the airflow, which I won't be. )

What you can't easily see is that the body is raised 40mm on the chassis to create a completely  flat floor and a 3-4deg incline of that floor from front to back + a large rear defuser , in principle  generating some downforce without running a wing
 
 This same config is also used successfully on the many Porsches and Ferrari road cars.  My car will be road registered and not a dedicated track car and so extreme front splitter and rear wings and ultra low ground clearance are not options.

The principles I have followed are nicely explained in this video if interested.  https://www.youtube.com/watch?v=OHuTDc2cVCY

This article also explains the principles with some CFD on a Europa.  http://lotus-europa.com/manuals/misc/aero/Europa%20Aerodynamics.htm

Thanks :-)

[Chuck Nukem]

I am curious to see how your floor pan takes shape. I am putting some thought towards doing mine in a similar manner. I have a few S1 cars that have the factory flat floor. I think one could fabricate a removable floor panel for later cars, possibly with honeycomb to add some rigidity (and peace of mind) to the structure. At a bare minimum sealing off the holes for the fuel tank and the engine compartment would help to promote flow and some ducts could be used to route air through the engine bay in a way that would increase downforce and promote cooler air in the engine compartment. I would think that would be more effective than the 47 style NACA ducts on the sides...even though they look way cool.

The bonnet definitely has a higher pressure under it which is lifting it off the car... I am not sure if I understand how directing that air under the car would promote downforce though. In my mind the path it would have to take would still disrupt the flow and add more pressure under the car. I am not an aerodynamicist and I don't pretend to be one! I would love to learn more and get some software one of these days.

[RonPNW]

Have you selected a radiator?
I'm following a similar path and have found that a Jeep XJ radiator will fill in the front when slightly tilted.

Ron

[Taimoshan]

Have you selected a radiator?
I'm following a similar path and have found that a Jeep XJ radiator will fill in the front when slightly tilted.

Ron

Hi Ron , have you got a link to the project you are building, one that you can also share? 

Re my rad decision, I ended up buying a radiator with dual spal fans, for a Ford GT40 , it is the right shape and size to fill the front section of the car, with the inlets and outlets in a convenient location, this unit is also able to support around 1000hp of cooling, I will have 700hp max I think.

https://www.ebay.co.uk/itm/153282221482

I also bought an air to water intercooler rad for the turbo heat exchanger.

 https://www.ebay.co.uk/itm/264852818177.

These 2 rads will sit stacked with the turbo heat exchanger core in front of the main engine rad.

The rads are much larger in frontal area than the opening of the Europa grill (double the area) , this is really important in order to slow the airstream as it flows through the rad core, as it gives more time for the heat transfer, once the air is through the rads  you need to speed the air up again towards the outlet, so that it can rejoin the main under car airstream at a speed as close to the main air flow speed, so that you minimise the turbulence of the merging air streams. You are trying to keep the airflow  as  laminar or "attached" the to underside of the car's flat floor as possible.

To slow the air then speed it up again you need to go from a small x sectional area of the std lotus grill to the larger x section area of the rad and then back to a small x sectional area of the outlet again. 

Being specific, the outlet x sectional area should also be slightly larger than the x sectional area of the grill inlet, so you ensure a pressure drop across the system internal system, to encourage airflow through the system. This setup will also minimise the Cd (drag) of the radiator cooling system which in effect minimised the stagnation zone in the front of the car and therefore minimises that Cd of the whole car.  As you can imagine, the coeficient of drag (Cd) in fluid dynamics is a square function of fluid velocity . So by reducing the air velocity across the rad core even a small amount can significantly reduced the drag caused by the radiator in the airflow. While significantly   improving the cooling efficiency.

 

[Taimoshan]

Managed to do a little more glassing on the first rear arch.

There was a lot of grinding and trimming to get to universal wide arches to take the shape of the Europa.  Its ok, but the second one will be much better, as I can take the measurements from the first one.

Anyway I got the width and the taper I was after, now its a bunch of glassing and filling to get the final shape.
 
Also the fibreglass front brake ducts arrived today, I'll post some pics in the next few days, now got to work out the exact location and fit them with out interfering with the rad cooling ducting

[TurboFource]

Love your build!

You need to resize your pics as they are too large to see the whole pic at once....

[Taimoshan]

(firstly Thanks to TurboFource for the advice on resizing the images. :-) )

Had a few hours on the arches again today. Made the width extension for the LH Arch and also did a few tweaks to the RHS, I think I am honing in on the shape I am after.

I also did a bunch of patch filling of the cracks in the old glass.  Still need to grind/sand the new glass flat, but its get more stable.

Also if you notice I trimmed the lower rear joining lip that used to hang down in the air stream, so I am starting to clean up the airflow for the underside.

[TurboFource]

 

[Taimoshan]

After a couple of weeks away for work, I got some time in the garage today to do some more work in the rear wheel arches etc.

I trimmed the LH Arch and then did some filling and also started rebuild the license plate section that had been modified to take a square plate vs the UK rear long single row plate.

Lots of filling and sanding today.