Front Splitter

[Keith Jones]

Has anyone in Auckland got an NA with a factory (or an MX5Mart) front lip spoiler I could look at?

I want to see whether it's possible to fit an effective splitter.

Thanks

Keith

[sprsta]

heres a link to one

http://hikickracing.blogspot.com/2011/0 ... itter.html

[Growler]

I have one loose if you want to take a look.
There is a flat section on the base where you could mount a splitter however I would look at redesigning from the swageline down.
PM me if you want to come and have a look though.

Looking at the link above the splitter he is building is just overkill!
It might be splitting the air but whats the the air doing after that. The front as it stands would be very turbulent.

[dynofiend]

Almost all the aero benefit will be lost in the extra weight you carry, especially if you use alloy or as ive also seen, MDF!

[hikickracing]

Hi guys. I'm the author of the blog linked above. Greetings from the USA!

I'm not sure if the material is available in NZ or not, but alumalite composite, or the alumacorr brand name composite is very light and very strong. Short of going to a proper wood/carbon/fiberglass/foam composite, it probably has the best weight to strength ratio. The added weight is minimal, however, the added benefit is incredibly big. Overall weight including the mounts, I believe were well under 15 pounds (6.81kg>) I'd say its under 4.5 kilos but I can't remmebr what the exact number was..

1. Turbulence behind the splitter comment
The splitter acts also as a partial undertray, so the effects of drag in that area is minimized. Now, as seen in many NASCAR studies, sometimes when air is acellerated through a device similar to mine, sometimes a significant amount of drag is created from the flow of air hitting the various structures of the undercarriage. However, from my DAQ and track data the splitter only serves to decrease drag at this point; much of the air is redirected to above the car, decreasing overall drag. Of course, the main purpose of the device is not to decrease drag.

2. Size of the splitter
You are right in your assesment. The splitter is HUUUGE for this car. It has to be paired up with an appropriate rear aero device or else the car will (and was, before my rear spoiler) be an oversteering, undrivable car. The rear aero device I chose is a modest spoiler. The car was slightly undeersteery mechanically, probably due to the fact that my front sway bar is somewhat undersized. I wanted to balance that out. With a 7" spoiler at maximum angle the car was balanced.

3. Practicability
If the device is for daily driving enjoyment, I would advice you to make a much smaller one (perhaps 5cm extruding from the lip), or not make one at all. If you don't have a laptime goal, even though the effects are very noticeable above 35mph, it isn't worth it. Furthermore, you WILL be scraping that thing everywhere, especially if your ride height is as low as mine! plan to replace it every once in a while, and be sure to make your mounts WEAK enough so that it doesn't pull anything from your structure off when you hit a solid object. But you have to be sure to brace the front-center area of the splitter very well, as it sees anywhere from 20-70kgs of downforce spread in an area of about 30-50cm^2 at miata highway speeds.

The end results were incredible. At my home circuit, there is an increasing radius turn that you have to take carefully. You come out of a chicane, and have to keep the car balanced enough to make the sharp right hander that is the beginning of the increasing radius turn. From there, you have to pick a spot to gradually get on the acellerator and eventually full-throttle all the way down the straight.

After the aero mods and wheel/tire updates, the corner is driven differently. Now you enter turn 9 (this is the turn's number) much faster, get the car turned around, and then immediately get on the gas all the way to full throttle. Its become a point and shoot affair.

Now, thats partially due to the new tires, but don't dispair! I tested and recorded data of the car's performance with just the aero devices and the same, old worn tires my car used to have. significant increase in lateral grip across the board. I'm sure my acelleration was hurt a bit because of my rear spoiler, but at that point air conditions were more ideal than my last data point, so I could not conclusively measure how slower the car acellerated.

Thanks for linking and reading the blog, if you have any questions please leave a comment on the blog. I stopped updating the blog temporarily but I still get notifications from it.

I encourage everyone to try out modifications, experiment, fail and succeed. That is what has made my car hobby more enjoyable! Cheers.

PS: I apologize for the horrible spelling and grammar.

[hikickracing]

Some of the posts above indicate that this explanation may be warranted:

A splitter works in two different ways.
First one is by splitting the air, as its been posted above. The main benefit is reduction of drag. As I've said above, sometimes it can actually increase your drag at very high speeds (think of oval car speeds here).
Secondly, and most importantly, a splitter increases downforce. This is achieved in two ways. Firstly, the air above the splitter builds up at the part where the air dam (or lower bumper in this case) meets the splitter. This creates positive pressure, which presses "down." At most miata ride heights, this is probably the main contributor to increased downforce. The other part of the equation is acellerated airflow under the splitter. Due to the wing-in-ground effect (check google) and the brunelli effect, the air under the splitter gets acellerated, creating negative pressure. This "pulls" the splitter "down." End result is very appreciable negative lift (lift force pointing down). Positive pressure on top, negative pressure below.

Some prototype sports cars get to use devices that resemble actual airfoils up front, though it is most of the time hidden by bodywork. It interacts with other aero devices built into the car and produces very very serious downforce. (think 5000+lbs of combined front and rear downforce) For most production based cars however, a simple air dam, splitter, and canard is the best you can do and is what you see on your typical televised touring car race.


Alumalite material is really ideal for hobbists: its been rated up to 140mph with properly designed mounts. However, if it is unavailable, the following are my recommendations:

1. ABS plastic
It has been used safely to 120mph by others. Slides very well when it scrapes the ground, cheap, and easy to work with!

2. Plywood
if you use a sufficiently thick piece of plywood, even if you do not sandwich it in other material, is often strong enough. Its heavier than any of the options above, but it gets used by all sorts of racers and the benefits definitely outweigh the costs.

3. Aluminum
A sufficiently thick piece of aluminum can be used too. 2-4mm should be good enough, but its just my hunch. It will be pretty expensive though.

[hikickracing]

I can't link to the spoiler build yet but if you look in the table of contents on the blog, everything is there.

[Keith Jones]

Thanks to all for their comments and suggestions.
I am currently running a splitter/undertray that covers the underside of the engine back to the rear end of the sump. This, together with the rear wing, is giving me a stable car at up to 230km/h and good lateral grip (around 190 km/h round the sweeper at Pukekohe for those that know it). However, the race class I am currently running in is now insisting on standard bodywork, so the aftermarket nosecone will have to go (at least for the summer season).

It's going to be an interesting exercise to see how close I can get to the current performance with a standard nosecone + add-ons and a smaller rear wing.

For anyone wanting to try a splitter, aluminium/plastic composite sheet (sold as Signbond) is good. It's stiff and light.

[hikickracing]

Keith,
very quick car! I think my miata would top out at 125mph. Its amazing your car can do over 160.

Signbond must be the same material as Alumalite in the US. Alumalite is mainly sold to sign makers.

You probably already thought of this but if you are limited to standard bodywork, as long as your class allows it a rear diffuser may help add some rear stability, that way you can run much more aggressive front camber.

Another thing that I wanted to experiment with before I sold the "broke-core" (broke as in not a lot of money, core as in hardcore) miata was running some vortex generators on the front end of the undertray. I hypothesized that it would help airflow stick a bit better through the imperfect underside (I had planned to run a partial, but complete undertray) out through the diffuser.