i was under a red ferrari today

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

I was at the auctions and in the back there was a ferrari up on the lift.

Fecking sexual it was. The onyl tiem I never took my camera, my sister thought it was a porsche Rolling Eyes

Front brake ducts with at least a 3 inch dia direct to the hubs.

What really interested me was the undertray the floor is perfectly flat pretty much, even more impressive was the venturis at the exhausts

trying to get a pic on the web but no luck.

Aerodynamic aids are great, the 19 really needs em!

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

nice....which one was it?

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

i'd love to see that!

Level 10 User Joined: 04 Nov 2005 Posts: 575

Would of mde a nice change from the old renaults anyway.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

I am trying to decide what it was!

i have pics of similar ones but cannae mind if its the right one, amber has gone to asda.

i'm so pissed I never took the camera though!

heres a ferrari F355 undertray, just look at it!

[img:200:158:2a72e7e815]http://www.autozine.org/technical_school/aero/tech_pic_aero_flatbottom.jpg[/img:2a72e7e815]

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

ferrari F355 coupe

this is the very undertray

[img:480:360:3608fb4e6a]http://www.ferraricars.org/img/ferrari-f355/structure-01.jpg[/img:3608fb4e6a]

it was all plastic

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

[img:480:360:f3c2ea4513]http://www.ferraricars.org/img/ferrari-f355/introduction-02.jpg[/img:f3c2ea4513]

the front grille, it was solid apart from 2 small oval holes at each end, these fed the brake ducts there was no form of expansion chamber just direct feed

if you look at the undere tray pic and this rear pic

[img:480:360:f3c2ea4513]http://www.ferraricars.org/img/ferrari-f355/introduction-03.jpg[/img:f3c2ea4513]

you can see the exhaust lie right on the exit of the venturi.

This creates a scavenge effect in the exhaust system which result in increased power the faster you go.

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Does every car have a Venturi or is it only on cars with a certain design?

If so how do you work out where it is?

Presumably this scavenge effect can be exploited to the max by correctly fitting an exhaust?

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Actually, I think I can see what you mean looking at the cars shape in relation to that image of the floorpan!

I take it the undertray is a vital part of creating a Venturi by allowing a more aerodynamic flow of air under the car?

Am I right?

Level 9 User Joined: 03 Jul 2006 Posts: 412

A 'Venturi' is essentially a system in which air (or any fluid for that matter) flows through a passage that narrows then widens. In this example, air flowing underneath the car makes the transition from atmosphere (open) down to the tiny gap between car and road, then opens back up into the big wide atmosphere to the rear of the car.

The point of this is that when the air is constricted into a narrower flow it is forced to move faster in order that it all gets through. This creates a lower pressure than had the air been travelling at its slower speed. Low pressure directly under a car creates a partial vacuum which helps keep the car forced onto the road.

Where the 'Venturi' shapes at the rear of the undertray come into effect is where you get the change from narrow car-road gap to open atmosphere... essentially the smoother you can make the transition, the less energy is lost and the greater the 'vacuum' under the car. Some nice complex geometry here can also lend a helping hand!

I'm not sure but i assume the scavenge effect here would relate to the exhaust feeding out into this lower pressure zone, the greater engine-atmos pressure difference helping to drive the exhaust gases out of the engine. Anyone know if this is correct?

/geek Cool

Site Subscriber Joined: 02 Oct 2004 Posts: 1575

sounds like you've got a degree in fluid dynamics Smile

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

what tom said.

airflow is a critical part of any car and its performance.

Motorbikes benefit greatly from positioning the exhaust exits int he right place and orientation.

also no POS 19, clio, vectra etc etc has anything like a decent underbody design.

theres loads of areas in aerodynamics and I find it intertetign but most find it boring.

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

No reason why you couldn't fabricate an undertray though?

I love the way you reference all the cars I've owned (19, Clio, Vectra) in the POS category!

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

well they are hardly M5's which have a lovely under body design and have fins at the rear to stabilise the car.

Fabricating an under tray isn't just 5 minute job

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

I'm sure it's not I was just ascertaining that it could be done if one so wished.

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

I designed one, and strtaed manufacturing it, for an Ariel Atom.

then i left :p

Site Subscriber Joined: 23 Jan 2005 Posts: 502

I think it only makes a difference over 100-150 MPH

Who can manage to keep a 19 over that speed.

Throw it round the corners. LOL

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

makes a difference at much lower speeds than that, big fuel economy booster.

As for sustatined speeds in a 19 over 100mph, erm theres a few on here that will agree that its possible on a daily basis...

Site Subscriber Joined: 23 Jan 2005 Posts: 502

Plywood

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

banana

Level 1 User Joined: 19 Aug 2006 Posts: 22

blackman would like to be under anybody m/f dont mind