Hi folks,

As I have been researching and getting advice on track day preparation it has struck me that what I assumed was 'go fast' stuff such as low profile tyres, is actually slower!!
So thought I'd start a list of the differences;

Looks Fast
----------
low profile tyres
big rims eg 17"
wings, scoop, bodykit
v. low suspension

Actually is fast - Reason
--------------- -------
higher profile tyres - bigger sidewall = more flex & less skipping
small rims eg 13" - less rolling weight & gearing (I think!)
minimalist bodywork - less drag, weight & FWD not needing rear downforce!
moderate suspension height - better suspension travel for traction (& kidneys!)

Anything else?!

Love this new forum BTW - thanks Mods!!

bodywork kit is a broad term.

Basically its about reducing airflow here, and accelerating it there.

The basics of some aftermarket bodykits are sound. air dam, side skirt to reduce the side entry or airflow under the car and diffusers at the back of the car. But there is more to aero then how the look on the outside. And often apart from added weight contribute very little.

True - I was generalising!

Yes - I remember on Top Gear when they were racing that BMW that the car was several seconds a lap slower when the Diffuser came off!

Does anyone have any experience of undercar aerodynamics for Swifts, or is it another thing that is very minor in the scheme of things?

It's actually very important but is generally quite difficult for a lot of people to make/utilise.
The most important thing is to get the car lower, using smaller wheels helps, a 185/60/13 is going to make your car sit 20mm lower than a 205/50/15 etc.
A splitter on the front bar/bumper will make a huge difference, there are a few of us working on solutions for this at the moment, (but don't expect anyone to market and sell it), most involve plywood or aluminium attached to the front bumper extending back 400-500mm underneath the car. this helps split the air cleanly to go thru the radiator and reduces lift, helps turn in on high speed corners.

Cutting part of the rear bumper/bar out helps trapped air under the car to get out and reduces lift, a rear diffuser helps too but is hard to build due to the shape of the swifts undercarridge.

Not to mention some of us are restricted in what we can do with rules.

For aerodynamics I suggest you might look at some of what is being done on ecomodder.com

There is a guy (basjoos) there who has modded his civic to bring the Cd from 0.34ish to around 0.17 (also see it at aerocivic.com). While this was done for fuel economy (he now uses 3L/100km's not all due to the aero mods) it also resulted in the cars top speed going from 95mph to around 140mph.

A lot of this is not really practical for motorsport at entry level but look at most high end sports cars and you will see these aerodynamic processes are being applied to the cars as well.

Interestingly more sports cars are heading towards low drag higher downforce setups by using better undertray designs. What is often missed by the ricer crowd is that the wing they have is doing nothing except increasing their fuel bill at the speeds they travel.

You will also find that small geo metro's are a popular base for modding for the eco crowd and useful insights for the GTi.

There is also some practical stuff down about this on autospeed.com

Personally, I think stuff that could make the GTi feel a little more planted at speed would be nice!

was wondering if anyone could design an undertray cover for our car cos THAT would definitely clean up the airflow and help us gain some top speed and @ the same time save fuel!!

yes saving fuel is important, ......... stick your head under the back of your swift and you will soon realise how difficult it is to achieve rear splitter in a swift.

My aim is 250hp at the wheel and highway economy around 6L per 100km's...

thats only possible in your dreams

let me introduce you to the concept called sarcasm

sar·casm
Pronunciation:
\ˈsär-ˌka-zəm\
Function:
noun
a mode of satirical wit depending for its effect on bitter, caustic, and often ironic language that is usually directed against an individual b: the use or language of sarcasm

Keep it up guys. I am really starting to enjoy this series of posts.
Steve

It is possible to have a car that is powerful and economical but not both at the same time.

You are not normally on boost when cruising on the highway.

If you have electronic boost control and set a minimum TPS of say 50-60% before it turns on and increases boost beyond wastegate setting you can trundle around quite economically untill your right foot goes down and stays down.

well of course on highway driving, thats why trucks use turbos. Economy (and torque). But to achieve 250bhp in a swift you are talking redline rpm stuff. At those RPM forget about economy.

Considering this is Motorsport section any mention of "economy" should be deleted by the mods as soon as it is posted. (Neo are you listening?) If economy is what you are after, feel free to petition the mods for your own separate section on this forum.

LOL!!