Functional flat underbody and rear diffuser design

[team_v]

just a thought, but wouldnt it be better to make a series of single changes instead of a heap all at once - that way each change can be evaluated on its merits.

e.g. first try different anti sway bar settings, then put seats in, then rear wing, then splitter, etc and work out which things in your case make marked improvements, vs which things make little or no gain. An extensive process, but the end result is more informed...

I think the problem is that there are so many variables (air temp and humidity, tyre wear, amount of fuel, potential boost leak from DV etc) that it is almost impossible to tell the differnece that one change will make.
You also have to bear in mind tht the more you drive the same circuit you are going to be more comfortable with it so you may end up going quicker by your own practice rather than any modification.

[Stuwey]

just a thought, but wouldnt it be better to make a series of single changes instead of a heap all at once - that way each change can be evaluated on its merits.

e.g. first try different anti sway bar settings, then put seats in, then rear wing, then splitter, etc and work out which things in your case make marked improvements, vs which things make little or no gain. An extensive process, but the end result is more informed...

And, ultimately faster. After all, isn't that what we're trying to achieve?

You all say the Mazda has heaps of aero. Don't forget the hi-tech leaf springs and recirculating ball steering!

I think you lot need to sort some things out.
-Is it a race car, or a street car?
-Can you actually afford to do this? Both monetary and emotionally (if you get it really, really wrong)
-if you can't afford to leave it in a crumpled mess at the track, you can't afford to take it there!
-Sam, there really is something incredibly satisfying about driving essentially average cars, very fast.

Change one thing at a time. Money and stick-on things won't make your car fast, developing it over time with well thought-out additions and adjustments will.

[s4mmie]

Good points Stuwey, and obviously some of the limiting factors when trying to build a street x track car.
I think that before going any further, my money would be best spent on getting a driver in the car with more experience and seeing how that goes.

Who knows, maybe I just need to learn to drive it the way it is? I like how it handles at the moment. It could maybe do with a little bit more turn in. I figure you want the car to want to rotate rather than understeer like a pig.

[Redliner]

If you don't want to soften the rear roll stiffness or increase the front, raise your front ride height or lower the rear. With a torsion beam rear end/mac strut front end, this shifts the bias of the grip slightly towards the rear.

I did this after I spun at turn 1 Phillip Island with lift off oversteer and I only lifted off for a moment at turn in. Since then, the car is much more stable under brakes too (the dive under brakes exacerbates the situation).



+100 (and kudos for being brave enough to state what I feel)

Totally agree.
When I installed my Kw coilovers the front was lower than the back.
I took the car out for a test drive and the tail was all over the place.
Played around with heights and the handling changed dramatically.

If the car is too low it could also affect how it handles. (spring pretension, roll centres etc).
I would think that fine suspension tuning would have the greatest effect on lap times
combined with testing and practice.

[Eddy]

Hoyhoy.



Folks watch this video of Warren Luff (he can drive) in Guy Hardings new Polo @ 2011 June Motor Magazine Shootout, he ended up doing
a damn good time.
You'll see what I mean in the first 1.5 minutes.
It behaves just like the Little Blue Girl, Its only after I got that sort of behaviour in the Pog that I got my fastest times.
If I go out too hard on the first lap, I'm a goner, I know, been there many times, thats why I like Wakefield Park.
It has run off everywhere, good for OLD FARTS like me, plus it lets ya go 110% & taste the dirt, but after a wash all is good.
Me started late in life with tracking, 2007 in the Dutton Rally I achieved 1'18" @ Waky in a powerfull car, now with practise
I've obtained a sub 1'10" in a wee Little (Blue) Polo.

What I'm trying to say is,,,,, things can get scary out there,,,,,PRACTICE.

[seangti]

Those with coil overs, perhaps also have a look at corner weighting so you know where the weight is sitting. I believe there is a place down at slackscreek with corner weighing ability. They may also be able to offer input as to rebound/spring rates. Some changes could assist balance.

I'm a fan of making incremental changes and measuring. From total stock to adding lowered springs gave me less consistent lap times, but much the same and few more "moments", added the bilstein struts and dropped 2secs a lap on flogged out continental tyres but had great adjustability. Put kumho ku31, lost 1 sec a lap and some on the limit adjustability. This was at QR sprints on their timer, not the gtech. If I did tyres and suspension together I wouldn't know how each affected the other. I also know my max braking g-force and cornering force so can compare forces with speed and time as I make changes to the car and my driving.

It's really just trying to optimise your current set up and ensure you can get everything from it.

Hope this isn't a rant, sorry if it is.

[clicht]

Just get on to a track day and drive, Clint. You've done open wheelers in the past which is far more than most of us here, so don't bother with driver training unless you feel something is "missing" when you get out there.

Yeah, you right...its just the polo is rather different from my race cars, but the basics are the basics....sure I'll see you soon on the track or a good Hill climb

[kaanage]

A road car will be a lot more forgiving and less responsive than an race car so you don't have to worry about being caught out as long as you don't leave the pits and then try to brake and turn in on the first corner like in the open wheeler

seeya out there soon, I hope

[pologti18t]

Have a look at the autospeed.com site. Julian has done a few stories on aerodynamics. He has a Skoda Roomster and sometimes posts in that forum.

His aim was for improve economy though
AutoSpeed - Trialling a Rear Undertray
AutoSpeed - Modifying Under-Car Airflow, Part 1
AutoSpeed - Modifying Under-Car Airflow, Part 2
AutoSpeed - Reducing the drag on square-back cars

[blackbetty]

Have a look at the autospeed.com site. Julian has done a few stories on aerodynamics. He has a Skoda Roomster and sometimes posts in that forum.

His aim was for improve economy though
AutoSpeed - Trialling a Rear Undertray
AutoSpeed - Modifying Under-Car Airflow, Part 1
AutoSpeed - Modifying Under-Car Airflow, Part 2
AutoSpeed - Reducing the drag on square-back cars

As i have a huge interest in land speed racing (i especially hope that they can approve racing on lake Omeo in country Vic) i very much enjoyed reading these articles, thanks for posting the links.

I have articles at home on aero tricks for cars - i'll try to go through them on the weekend and find some relevant stuff for this thread.

As the GTI is a hatch the sudden drop ver the rear window is probably the single biggest area to make aero gains. the undertray would be second (mainly because of the tray thats already there from the front bumper). the polo bluemotion (not sure if that was the model name) also had some good areo ideas