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What started out as getting the splitter level, straight and plugging up the gap between the splitter and the lap turned into another project. The splitter in now level still need to plug the gap, that will be another post...

Been a project of mine for a while to build a duct that makes all the air flow through the radiator. The car has had no heat issues with respect to oil/water getting cooler air into the intake has been a priority.

Another job was to remount the internal splitter support rods due to the bending of the brackets.

Whilst the car does run a splitter, the air is not channelled as it was designed to do, the OEM undertray has sides that causes the air to exit at the back of the engine and not at the sides of the engine bay as my splitter does.

This photo shows what it was like. The air could spill out from the engine bay anywhere it wanted to.
DSCN2619 by Eipeip, on Flickr

There is no photos of the gap between the bottom of the radiator, but it was rather large and uncontrolled air. I had previously attempted to manage this air by cutting down the OEM undertray, but I it was a failure and did very little.

First was to relocate the splitter brackets as there current mounting points did not suit my thinking/developing plans...
Where the rods were connected to, part of the OEM undertray can be seen, but this stops before the radiator.

DSCN3004 by Eipeip, on Flickr

One of the bent brackets, the fact that they are bent suggests that there is downforce being developed.
DSCN2995 by Eipeip, on Flickr

Brackets relocated. The brake duct hose needs to be replaced, the air hose is different (part of future plans) and the sway bar have changed since the photo at the start of the post. The extent of the previous mod to the undertray can be seen, a slot had to be cut for the location of the previous mounting rod.
DSCN3005 by Eipeip, on Flickr

Now to the radiator duct.
There was some 50 x 50 aluminium angle in the shed that proved to be just enough to close the gap between the OEM undertray and the radiator. Good thing the red shell was at home as it was a great source of parts to play with...

Test fit photo, not exactly straight but foam will be used to sell the gap up.
DSCN3024 by Eipeip, on Flickr

From the bottom. There was only 2 screws holding on the angle at this time and the slots for the splitter mounts were done.
DSCN3026 by Eipeip, on Flickr

From the right hand side. The hole still needs to be cut to bring the air duct through. However this looks like it will be effective.
DSCN3027 by Eipeip, on Flickr

The only issue will be getting to the splitter nuts with the OEM undertray on. Maybe a case of putting access flaps in like on the OEM undertray.

Splitter mount
DSCN3002 by Eipeip, on Flickr

Good stuff!!

I went down a slightly different path. I had bought some "L" section plastic strip which was lying around waiting to be used, around about 150 X 75, and I cut that up to seal up most of the gaps, including the gap at the bottom of the radiator. My ducting now is basically horizontal from the opening of the intake to the top of the bottom tank. I used the same strip to clean up the edges, and combined that with aluminium duct tape to complete the job. Having also removed the plastic inner bumper thingo, I also used some plastic sheeting to stop any incoming high-pressure air escaping upwards, although the sealing of this leaves a little bit to be desired. I will see if I can get some photos later.

The end result was that, on a reasonably hot day, I was unable to get the water temperature to come up to its proper temperature, and as a consequence of running an oil/water heat exchanger, the oil would not reach its minimum operating temperature. I had to jury rig some masking of the radiator intake to reduce the amount of air entering before I could get my temperatures to come back up to normal. This on a hot day, even if it wasn't the hottest, goes to show the efficiency of the stock cooling system when the gaps that allow incoming air to bypass the radiator are eliminated. I should add, I am also running the stock undertray. My splitter looks like it is shorter than yours, it cannot extend further back than the front of the front wheels.

The inability of my thermostat to regulate the temperature is a bit of a worry, although it may have more to do with the placement of my sensors than anything else. That is something which is a high priority for me, given that at the same event I lost a cylinder. I am only now starting to strip the engine down so I am not sure what the exact problem is, but it is a bit of a coincidence.

On a related note, how expensive is that material that you are using for your splitter? It certainly looks like it can handle the job, but looking at their website it appears that the sheets are very large. May be we need to organise a cooperative buy, and cut up one sheet between several of us

Thanks Greenmachine. I'm going to refine the shape of it in the future, seeing how other have done it will help. Since I have a small leak in the radiator I may as well remove the radiator to get it fixed and seal the gaps on the side of the radiator.

Another consideration for this mod is to reduce the amount of dirt that can get sucked up into the intake especially if doing dirt sprints again. The plan is to have a bellmouth on the front bumper to get cooler air into the airbox, but being ale to block this off, remove a piece of hose and get the air from inside the wheel arch. Not sure when this plan will happen...

In the rules I run in the splitter can not extend past the wheel centreline, but may extend 50mm out from the bodyline at the front. Hence why I have 2 splitters. Thinking of getting thinner stuff and making a rear diffuser as Monopan can be shaped rather easily, again a project for another day.

The monopan cost is about $125 a sheet, however only 1 splitter per sheet Full details are here http://mx5cartalk.com/forum/viewtopic.php?p=849484#p849484

greenMachine - my Integra uses 6 or 8mm ply for the splitter. It's strong enough and only about $30 per sheet. It's had quite a few chunks taken out of it mostly front clipping the ramps on the trailer.

I did look at Monopan and Alumalite for the same purpose but ply is cheaper, reasonably light, and much easier to work with.

I too use ply... It's a good compromise between price / weight / strength. Mine has survived well over the last 18 months that I've run it. It has a few big chunks missing now due to getting on and off the trailer, but other than that it still looks good.

With splitters, in most classes that restrict the length to the leading edge of the front wheel, or to the center line of the wheel, you can still mount it past this point as long as you pepper it with 50mm holes on 150mm spacings.

Did this on the Sunday evening, intake for the airbox. This gives a much cleaner airflow. Thinking of making an air box inside the front to act as additional air capacity or fitting a pre-cleaner for dirt sprints.

IMG_1286[1] by Eipeip, on Flickr

Ok, I promised photos ...

As mentioned above, this setup seems to be working well, if not a little too well! The plastic used is from Bunnings Racecar Supplies, it is (shhh, don't tell anyone ) a building product used for skirtings I believe. It is thin, flexible and easily cut. Pair that with aluminium duct tape, a pop rivet gun, and hey presto, why didn't I do this ages ago ...

This photo shows the plastic sheet installed with the long arm horizontal, and the short one vertical against the front face of the bottom tank (see next photo), secured with pop rivets. You can see bits of the side ducting as well, installed the opposite way - short arm horizontal, long arm vertical.


This shows the bottom of the plastic duct, the deep vertical section is to provide rigidity and prevent bowing of the plastic when duct pressure rises.


This is looking up at the front of the bumper, and shows some relatively rudimentary sealing of the gap behind the bumper.


Sealing of the gap in front of the radiaror. The power steer cooler is secured by the two bolts between the bonnet pins, and it needs access to a modicum of cool air.


That composite splitter material is interesting. To date I have used the special racer grade ply ( ) from one of the aforesaid Bunnings Racecar Supplies outlets here. My preliminary opinion is that for me I don't think the advantages of the composite outweigh it's handling requirements and added cost. Having said that, I should weigh mine - that may change my perception of the value equation.

Thanks, have some ideas now. Since the radiator is out I may spend the weekend getting the ducting in. I have an OEM radiator I can fit to get it close.

Too slow to edit my post : To be clear, in picture 2 the factory ducting behind the radiator has been removed for maintenance access, so that photo does not show the 'as raced' ducting setup.

Got it all back together on the weekend. The biggest pain was attaching the splitter as normally the nuts are done up by access through the wheel arches, not possible now due to the OEM tray being installed. However the left hand side bolts can be done from above with a really long socket arrangement and the drivers side can be done through the hole for the air intake.

Did not get to seal around the sides just yet, plan for another day, however the top has been sealed very well since I don't have the bonnet release catch anymore.

Will see what the temps are like after Morgan Park. Be interesting to see if there is more downforce being developed on the front as the splitter is now level and the air in the engine bay is no longer entering the wheel arches. This should also decrease the air intake temps.

My 12mm structural ply splitter weighed 3.2kg. My newer marine ply splitter is a shade under 4kg.

NICE, Plan is to decrease the size of the Monopan next time to about 10mm.

The plywood splitter I first made is still at home, it weights a bit more than yours because I put 3 layers of fibreglass on the bottom and 2 on the top to protect/waterproof it. It is still looking good!

Biggest issue I have found is getting it level in all directions, it leaves a big gap at the front that needs to be filled. Does not help with the other add ons I have on the front.

Magpie wrote:NICE, Plan is to decrease the size of the Monopan next time to about 10mm.

The plywood splitter I first made is still at home, it weights a bit more than yours because I put 3 layers of fibreglass on the bottom and 2 on the top to protect/waterproof it. It is still looking good!.

My 12mm ply splitter is just sprayed with $2 black paint (so its less obvious..) and 18mths on doesnt look any different to when its was newly done. (except for a few scrapes/dents.. from hitting kerbs, trailers, etc) Has run 4or5 wet meetings in that time and gets soaked each time I wash the car and hasnt lost any shape or swelled..

I'd say fibreglassing is overkill, and just extra weight (and time/effort) you can skip...