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Discussion Starter #1 (Edited)
With all my suspension and braking work done I though it was time to work on the aero on my MR2.

The local track here is small and do not have much high speed turns with the exception of one corner, turn 8 which is notoriously difficult to power through. In the case of my MR2, my speed as I approach the turn would be just a little too fast that I need to either ease off the throttle a little for a few seconds before I enter the turn or give the brakes a quick dab if I approach with WOT. The corner itself is a sweeping medium/high speed corner followed by a long straight so the exit speed is key to getting a good lap time. However, if you enter the corner a little too hot or get on the throttle a little early, you are almost guaranteed to spin. I have crashed into the barrier once and so have many others. Half the crashes on the track actually happens here.

My goal is to generate enough down force so that I could power through this corner at WOT and my first move was to order a large GT wing that would hopefully generate enough down force to glue the rear end down to prevent my car from entering into a spin. I know putting on a huge wing at the rear end would give me balancing issues and will unload the already light front end so a front splitter is a must if I want to install a rear wing.

The first material that came to mind was alumalite which seems to be material that everyone is using. However, it seems to be impossible to source here in Hong Kong so I've ended up asking a body shop to make one out of 4mm thick fiberglass instead. I was expecting just raw panel and to work out the mounting method myself but the body shop was kind enough come up with a simple mounting solution by adding brackets to the bottom radiator mount to bolt the splitter on directly and also adding two mounting tabs to the end of the splitter which extends to my bottom strut bar.
The twos pictures below are actually taken after I have done further modifications on the splitter (more on that below) but still shows the mounting brackets.




The front edge of the splitter is simply secured to the OEM lip by drilling holes along the bottom of the lip and secured by push pins.




After installing the splitter onto the car I discovered two flaw with the design. Firstly the bottom of the OEM lip bumper was actually at a slight angle to the ground slanting upwards towards the front to prevent scraping of the lip and since my splitter is sitting flat against the lip, it follows the angle and had an upward rake which will direct additional air into the bottom of the car. Secondly, the splitter still sits quite high off the ground and also does not look to be too effective without an air dam directly above it to build pressure.




To improve the splitter, I have used a 40 x 20 cm rubber strip to create an air dam between the OEM lip and the splitter. The ends going to the side of the lip/bumper is cut roughly to a taper to counter the rake on the OEM lip/bumper. Due to the thickness of the rubber air dam going in between, the lip is now needs to be secured using screw and nuts making installation more of a hassle as the splitter completely blocks off access to the inside of the bumper and lip. Lowering the splitter also created a gap between the splitter and the original tab attached to the bottom radiator support (as seen in the second picture at the beginning of this thread). I will be fixing that problem in the future by placing a cylindrical spacer between the splitter and the mount. The overall result after the modification looked much better aesthetically and hopefully performs more effectively.




The current attachment method actually felt pretty strong but I will be running in excess of 130 miles per hour at the track so it is better to add additional reinforcements to the lip. I was initially think of adding splitter rods but that would offer no flex to the splitter should it hit the ground. Using wire cable appears to be a better alternative which tugs on the splitter preventing it from flexing downwards when pressure is applied from the top while allowing flex when the splitter is pushed upwards. Attaching eyebolts to the car was surprisingly simple. There is actually a long piece of reinforcement strip running along the bottom of the top section of the bumper to secure it to the bottom of the bumper beam. The reinforcement strip is actually attached to the bumper beam via push pins. By removing the push pins, I could tap their hole an attach eyebolts to the bottom of the beam. There are actually four of such mounting mounts along the bottom of the bumper and I chose to use the middle two that is hidden behind the license plate. The second pair of attachment points I used where the fog light mounting brackets a long eyebolt is needed as the mounting point is hidden quite far back.
 

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Discussion Starter #2
Lastly it seems like the side of the splitter may not be as effective at towards the two sides as the curve of the bumper will direct air away to the sides so I have simply cut two aluminium sheets and attached them to the sides to block off the air's escape path. Those end plates looked mean!!


Went for a track day after the aero mods for the first time last week and unfortunately the weather was not cooperating and it rained for the full day so I really could not test it fully. However, the front end did felt more plated at speeds. Normally the faster you go the lighter the front end would feel but with the splitter increased speed seem to have no effect on front end lift. I guess the theory would be, the increase lift generated by the increased pressure of air entering the under side of the car/vacuum pulled on top was countered by the increased pressure pressing down onto the splitter. There was no noticeable lift on the front end at speeds even with the huge wing at the back. Looking at pictures taken at the track, there is no significant distortion of the lip even at high speeds so the mounting is definitely strong enough.



 

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Just a hair more than 3 inches but if I could it all over again I would add an extra inch. Three inches looked plenty when I am sitting at my desk staring at my ruler but its not much at all when placed on a car.

As mentioned in my very first post, yes I considered Alumalite. Unfortunately I am unable to source it here in Hong Kong so I had to use fibreglass instead which is very costly when made in one large piece!
 

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Just a hair more than 3 inches but if I could it all over again I would add an extra inch. Three inches looked plenty when I am sitting at my desk staring at my ruler but its not much at all when placed on a car.

As mentioned in my very first post, yes I considered Alumalite. Unfortunately I am unable to source it here in Hong Kong so I had to use fibreglass instead which is very costly when made in one large piece!
If i go 2" with thick alumnalite sheet. Do you think I can get away without the support/hang thingy ?
 

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Discussion Starter #6
I do not have access to alumalite so I cannot comment directly on its stiffness.

However, I have driven the car on the highway before installing the cables with the fiberglass piece. Although I cannot see the bumper of my car while driving and therefore cannot visually confirm whether there is any flex, the front end felt planted while driving and there were no signs of bending upon inspection after the drive. I think it should be fine without the cables as long as you stay below 100 mph. The mounts below the radiator support beam and the bottom strut bar is definitely needed though given the size of the piece.

2" will be way too short, I would stay with 3".
 

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I made mine out of a thick sheet of ABS plastic. Super durable! can cut with jigsaw and only costs $180 for front sides and back. I made a video here:

youtube.com/watch?v=Xk5D3H_3NAM
 

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Discussion Starter #10
Nice work and looks good. Can't wait for a full test with no rain and the results.
Hit up the track again last month under dry conditions. Rebuilt the engine but the tune was rushed to make it to the track in time.

It did not work out too well.

Track temperature was moderate but I was having some serious overheating problems. Coolant temperature would hit 110C after 2 laps on the track. I did not make a cut out on the splitter as it hangs a little lower than the bottom of the car and I though that gap would vent sufficient air for the radiator. I guess that's not enough and I'll be making a cut out on the splitter to let more air out.
 
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