Merli's R32 Track Bitch

[nfi]

:) Looks the goods.

Thanks Dane.

Edited June 3, 2009 by nfi

[Merli]

Yep... as I thought... Front undertrays are mostly (and in this case... COMPLETELY) flat.

I'm still interested on the fundamentals in aero design that Troy was talking about though!

[Ant97GTR]

Nice work Dane!

Merli....I think Troy was talking about possibly incorporating a splitter and making it flatter. From what I know the flatter and closer to the ground the better....I think that design you posted caters more to the ricer with the moulded ducts.

If you have a look at the Top Secret one :drools: it is pretty flat and I think that central duct is there to suck the hot air out of the engine bay after the radiator. Either that or I have my airflow mixed up and it supplies cold air from under the car into the engine bay

[phunky_monkey]

I thought it was a good design from what I know admittedly not much), and shows how to do it yourself without super expense and will be an inspiration for my car when I get it back. The guy who did it also report a massive improvement in the handling of the car, and when he smashed the front splitter off the performance of the car dropped off markedly.

Here is the thread for anyone interested, with some good trial and error and real world experience. Get past some of the dicks that inhabit the site and there's some good info.

http://www.ziptied.com/forums/index.php?PH...v_next=prev#new

[Beer Baron]

well ones like the HKS Kansai one, and the garage kagotani one we use on marks R34 are NOT flat. they incorporate what is essentially an upside down wing. it provides front downforce. and plenty of it.

have a look again at the kansai one, and the garage kagotani one. they are acutally diffusers unlike undertrays. splitters are a whole different thing again and are very useful too.

Ant, they are not ducts. they are sealed. they don't extract or introduce air to the engine bay. they are aero devices.

have a look at the shape. particularly the garage kagotani one (bottom pic). you can see the same is basically like an imprint of a wing. the kansai one looks like it's a little steep to my naked eye but I could be wrong, I'm no aero expert.

[Roy]

Baron is on the money. Look under the FIA GT3 cars etc

[benm]

Waste of time doing just that front section if you aren't going to do the rest of the car...

[Merli]

  benm said:

Waste of time doing just that front section if you aren't going to do the rest of the car...

You're basing this opinion on what prior qualifications and/or industry experience?

Aero is a gradual trial and error process... Too much downforce here, too little there, change this, change that... Just ask John Pelican who's been constantly refining his aero mods for hte past two years...

I'll get there eventually, but everyone needs to take first steps

[benm]

What I meant was if ur going to all that trouble putting a car on a hoist and making templates etc etc an extra few hours and u could have the entire car done underneath.

[Merli]

Ahhhh yep... I hear you.

Thing is, I bought this diffuser design already made... It wasn't a car on a hoist with template after template affair. That'll come much later when I have the time to really read into aero theory.

For now, it's just a little something to smooth out the air traveling under the car and protect the sump against those nasty ripple strips!

[benm]

Lemme know when ur ready and i'll make my wind tunnel available for you

[Ant97GTR]

Thanks Baron. Agreed about the garage kagotani one that you pictured as you can clearly see the 'wing' shape mould, however I would like to see the kansai one. It looks to me like it may be a cutout or vent of some sort due to the shape of what I can see in the that pic.

[Beer Baron]

  Ant97GTR said:

Thanks Baron. Agreed about the garage kagotani one that you pictured as you can clearly see the 'wing' shape mould, however I would like to see the kansai one. It looks to me like it may be a cutout or vent of some sort due to the shape of what I can see in the that pic.

nope, it's definitely not a cut out or vent. it's the same dealie as the kagotani one. a negative pressure scoop/inverted wing type thing and it's all sealed, no hole anywhere. trust me I have held one in my hands... I just think the angle of it may be a little to severe for best results but again I could be wrong on that point.

[Ant97GTR]

  Quote

nope, it's definitely not a cut out or vent. it's the same dealie as the kagotani one. a negative pressure scoop/inverted wing type thing and it's all sealed, no hole anywhere. trust me I have held one in my hands... I just think the angle of it may be a little to severe for best results but again I could be wrong on that point.

How did I know you would be one of the only people in Oz to have had one in your hands

Fair enough....it wuld be interesting seeing it perform in a wind tunnel to see how it changes the airflow.

[BezerkR32]

ill think youl find that its illegal to run undertrays past the rear of the front bar in some classes.

  benm said:

Waste of time doing just that front section if you aren't going to do the rest of the car...

[Neil]

Nice little debate we have going here boys on under-body aero. I'm not going to post whos wrong and whos right because like all of us it's mostly bloody quess work and I'll put money the Japs are doing the same. Ben's right though,,,you really need a wind tunnel.

What I will say is my Radical runs a flat floor 3/4's of the car and then tapers into the rear diffuser, here's a pic of an SR3 with add ons. Radical does use a wind tunnel so they must be doing it right.

If you are not going to cover the whole under car then you must be waisting your time. From what I've read it's all about clean smooth air under the car and then the rear diffusor adds down force for the rear. Which brings us to another little problem,,,if you do the whole lot properly,,,it will be a pain in the arse to work on at the track and in your garage. The other problem is getting all that GTR heat out from under the car,,,I have spent many hours thinking how to do it to the "Raceworx" nugget,,,I still am undecided.

Stuart,,,if Andrews logging it as a S/Sedan he can cover the whole lot.

Andrew have you read Racecar Engineerings mags??? Duncan loaned me 1 months and I have another and I have to read the same friggin article 3 times,,,but I still don't quite totally understand what they are on about.

Neil.

[JAGR33]

Neil's on the money, the amount of heat emmitted from the engine, gearbox and rear diff during racing conditions is astounding. Covering the whole underside of the car would creat serious heat issues. I'd say having a front diffuser/undertray would suffice, can't really be a bad thing could it??

And Beer Baron is right too, having a completely flat undertray is no good, I've seen a few diffusers on race cars and they all have the centre cavity. Why does it have to be there? NO IDEA!!!!

I'm sure Roy knows all the technical information on why it works, so c'mon Troy, enlighten us!

[Roy]

Way to involved a topic, need pictures and face to face time and trial and error. A high level snapshot, the best palce to start to get an understandign of what you should look for...

Since we drive road cars or at least track cars based on road cars we are never going to get the sort of ride heights you need to get real downforce from under car aero. So all we can hope for is to eliminate postive lift.

Numbers vary, but its not unusual for at speeds of around 180km/h you can have 40-60kgs of lift. You want to get that to zero or even to the point where you are getting -20kgs lift. So you need to look at airflow.

The heat is an issue, but consider how do mid engined cars cool engines? They are predominantly cooling the engine using radiators and coolers for engine oil and coolant, they are not cooling the engine or exhaust. Though you need to keep an eye on that as well for obvious reasons. Good bonnets for radiators and sides of bumpers for oil coolers excel here

As for the rest of it, there are plenty of good texts around and its too hard to explain without pictures graphics. But seriously, if you read up and get yor head around Bernuolli equation then you are half way there.

Apllied to cars and the topic, basically the Bernoullis equation says that if air moves fast it has less pressure. If air moves slow it has more pressure. The classic example being the blowing air accross the top side of a sheet of paper making it rise. The higher velocity air you are blowing accross the top surface creates a low pressure zone. The pressure on the underside of the paper is higher so the paper is forced upward by the higher pressure.

This is obviously the opposite of what we want. So we want air to flow quicker under the car then over the top. The pressure on the upper surface of the car where the flow is moving faster is lower than the pressure on the lower surface, giving you lift like a wing.

[G_T_R]

Most mid-engined cars also have strategically placed NACA ducts in various sections of the underbody as well as corresponding venting in the rear to promote cooling airflow through and around the heat prone areas.

[bigmikespec]

  Roy said:

Since we drive road cars or at least track cars based on road cars we are never going to get the sort of ride heights you need to get real downforce from under car aero. So all we can hope for is to eliminate postive lift.

Forgetting the impracticalities of having a car that is so low on the road for a second...

There seems to be two issues when it comes to lowering a GTR too much, poor driveshaft angle and suspension geometry issues (which I do not understand completely). However, what could you do to fix the driveshaft and suspension problems and lower the car enough to make a desirable difference to underbody aero. How is it that cars like the Mspeed R34 and Prostock R34 have such a low ride height...?

Sorry, may be a dumb question but I am still learning too