Mazda Rotary Club

De spoiled Rx with standard bodykit how and where can i now get downforce suttliy eg with splitter and rear diffuser anyone know of any that can do this and got piks?

I would take any splitters and diffusers downforce claims with a pinch of salt.

I doubt if any aftermarket products get tested properly in a wind tunnel, with downforce measurements taken.

I would go into this with the view that any product \'may\' do this, rather than \'will\'.

Good luck in your search!

Max

yes but they obviously do work or hypercars wouldnt have then for example TVR have no spoliers they produce all there downforce from a splitter and diffuser and chasis shaping so surley they work.

i just want to know what ones will work at high speed around the 180 mark! i know that cresent suzuki have a wind tunnel so you can test you bike is there one available in the uk for cars?

QuoteOriginally posted by Mr_7
i just want to know what ones will work at high speed around the 180 mark!

What, for when you\'re on the A25 or something???:eek:

no for when im pulling out of my drive

Most spoilers etc on road cars simply clean airflow or are cosmetic.  

Clean airflow is actually very important, affecting stability, cooling etc but im not gonna pretend I would have a clue about it beyond that :D

i know most of them cosmetic thats why im trying to find ones that work its produces the stabilty through the vortex that it leaves but im not into that i want downforce at high speeds so quest continues thanx any way J4P RX

Ok then. you\'re right - I\'m wrong, slap a splitter on your fd and it will work ;)

"Ok then. you\'re right - I\'m wrong, slap a splitter on your fd and it will work "

oh sarcaism how bout your right and TVR and koinskegg and maclaren f1 amoung many other hypercar builders are wrong try that!

No, they are right - more than likely.

Have you grasped what I\'ve said before?

Those cars are (I hope) designed with them in mind, and tested (I hope).

Can\'t say the same for any aftermarket FD splitter.

Max

PS I\'m not nasty, honest - just trying to keep you pointing in the right direction. How would I feel if I told you to slap one on, and you lost control at high speed, becuase it doesn\'t function as you hoped?

thats the reason for the post so that i can have some feedback and someone might of actually designed one and they could let me know also if i could get the car in a tunnel then i would try that

the koinskegg apparently is the quikest car at 242mph and has no spoilers cause of drag

Mazdaspeed test all their stuff in a wind tunnel i heard, but the new kit (R-Spec) that has a really nice rear diffuser is $$$$$$$$$$

(http://www.jt-imports.com/Mazdaspeed%20rear%20bumper%20diffuser.jpg)

oh that rear diffuser looks nice what sort of money are they is there an official mazda front splitter as well?

Many of the recent TVR\'s don\'t use anything and rely on the chassis capability. For example the chassis from the Griff is directly drawn from the Tuscan race cars and develops huge levels of grip at all speeds.

I\'ve owned 2 Griffs, 2 Tuscans and 1 Cerbera and the only splitters/diffuser type arrangement was one designed to push cold air into the bottom of the engine. This tends to get knocked off on most of them as they are held on with three screws. In fact only my second Tusc still had it intact.

Some of the later cars use splitters and diffusers (Sagaris/Typhon/Tuscan S et al) and indeed some cars from the 80\'s such as the Wedges (450 SEAC springs to mind with it\'s surfboard glued to the boot).

Unless I had a seriously modified RX I would feel pretty sure that I could de spoiler it without adversley affecting the handling.

All the best

DC

Oh my dream car is a cerbra 4.5 what did it drive like? i understand what you say but at high speeds downforce will be critical in breaking and sweeping bends the Sagaris of tvrs is probablt the best best example of spliteers and diffusers as they are clearly visably but when they are devolped they do incoperate airpockets into the chasis

I had the 4.5 Cerbie, in fact if you go to //www.davidgeraldtvr.com and look under used cars the one pictured is my old one. It\'s sold again now but it\'s one mighty motor.

Whilst I can drive the RX and it is more then a match for Tuscs and Griffs, nothing beats that Cerbera. 180mph on the way to Le Mans was easy for it. In fact once over 140 it pushed down into the road even more. And the noise - mine was decatted with a sports exhaust and it was measured at 128.9db at 4500 rpm standing 1m away. Mind blowing.

If ever funds permit every petrol head should own one. Absolutely stunning to drive.

Ahhhh I miss it - must get the RX out tonight...

All the best

DC

QuoteOriginally posted by Mr_7
but when they are devolped they do incoperate airpockets into the chasis

I\'m not sure on that one - it\'s not something I\'ve heard mention before. There\'s an interview with one of the designers in Sprint (the TVRCC mag) I\'ll see if there\'s any mention...

Cheers

DC

i was in a chipped a TT 225 when i went up against one it was 4.5 round a corner on to a dual carriage way he missed third then found it on the straight it was level untill it came on cam i have never seen a car like it in my life ever it was mad the fastest car i have seen a challange for a stallion

You must be a hell of a  driver to get the full potential out of a FD and then ask for more down force!

Heres a few pics of whats out there, not sure you going to gain much using them but here you are.

Scott

and another

heres another

You dont have to be much of a driver to hit the top speed in a car just need bollox and that sort of speed they both look lovely particually like the black one but looks like cosmetic the top one looks usefull fins to it straight and high level exit do you know the makers of those diffusers

last one.

mmm, you just mean straight line speed not going around a track let you off then.

They are both RE Amemiya but im not sure if they make the first one anymore (yellow car). The lastest one is carbon fibre or you can get it in fibre glass also has an adition to it called some thing like a bow tech generator.

I think your wrong about just being cosmetic though.

Definitely no expert but just read a magazine piece about this by Lotus aerodynamics guy.  Said that rear aerofoils need to be high and to rear of body to develop any useful downforce.  (Like the Exige - all designed around the aerodynamics) It means even the biggest rear spoilers on RX\'s are of dubious benefit except possibly the ones that sit up and back on the alloy uprights.

The front splitter on the RX was included to improve low speed cooling - especially on twin oil cooler cars according to the Brian Long book (I think) so probably not much ground effect intended out of that.

If you are talking about ground effects to generate negative lift under the car, from (very) limited experience with a Le Mans car, you need to design/build the whole underside of the car with this in mind - not just add the exit venturi that most of the aftermarket bits seem to be.  Is there some benefit to smoothing airflow just around the back axle?

Be interested if anyone can say if the RX\'s rear spoiler actually delivers downforce based on their experience of running with and without.
A

If you want a good place to start with aerodynamics then the following books may be of use:
Race car aerodynamics:designing for speed   by Joseph Katz
isbn no. 0-8376-0142-8
Competition car downforce by Simon McBeath
isbn no. 1 85960 662 8
and mainly aerofoil design but very interesting
Theory of wing sections by Abbott and Doenhoff
isbn no. 0-486-60586-8
these are all available in the uk try amazon for the top two the other one i ordered from waterstones.
Bear in mind aerodynamics can be a minefield even for experts.
You can hire a wind tunnel in this country, and no not with a formula 1 budget either. I saw a peice in a magazine (i think it was Race Car Engineering?) about a hill climber with an elise who hired a tunnel for a day. Don\'t quote me but i think it might have been at MIRA the vehicle reserch bods.
 Or instead of a day at a wind tunnel buy a CFD programme and play to your hearts content without making anything. Then when you figure out what you want, go ahead and make it/have it made.

I had my FD with and without spoiler and the rear end was lighter without the wing. It depends alot on the angle of the wing as to how much downforce is applied. I currently have a RE Amemiya rear diffuser as well as an Auto Exe rear wing and the Feed front canards - the car is stable at high speeds but nothing drastically different to running without them. The rear wing made the most difference I noticed as said above.

I think that sorting the suspension will help masses, which will reduce body movement of the car when accelerating, although this would place more strain on the trailing arms etc..

As said earlier the Mazdaspeed kit was tested for high speed usage, but RE Amemiya, Feed, Pan Speed all test their products on track in Japan. Even my Feed Canards where tested before being sent over to me, the first batch I was gonna get broke when they tested them so I had to wait for the next batch!

thatnks everyone for your help i will look in to it more and let you know what i go for

How much would a vented bonnet affect the downforce by allowing the air in the engine bay to pass over the car rather than exit out underneath it. Any thoughts as to the overall affect on the car?

If you think about it its not going to affect it at all im wondering if your being sarcastic

QuoteOriginally posted by Mr_7
If you think about it its not going to affect it at all im wondering if your being sarcastic

It most certainly will affect it.  How I dont know, otherwise I would be an aerodynamicist on a load of money making racing cars and stuff :p

Its more likely to affect engine cooling though.  Theres bound to be a few vented FD bonnets out there that do more harm than good.  Its all about air speed and high and low pressure areas.

QuoteOriginally posted by wookie

 Or instead of a day at a wind tunnel buy a CFD programme and play to your hearts content without making anything. Then when you figure out what you want, go ahead and make it/have it made.

don\'t forget the high end cad system that can cope with free form surfaces oh and better get a degree in aerodynamics too so you know how to use that CFD system and what to do with the data it chucks back at you !  I\'d say it would easilly be cheaper to hire a wind tunnel and make some wing / splitter mock ups :D

QuoteOriginally posted by Mr_7
If you think about it its not going to affect it at all im wondering if your being sarcastic

So you don\'t think moving significant airflow from UNDER the car to OVER the car (and possibly changing the degree of turbulence too) will change the lift / downforce on the car?

I am starting to think this is a troll...

OTOH if you are getting to speeds where downforce matters on UK roads, you probably need a RoadAngel before a spoiler... and you need a wheelbarrow to carry your cojones. :D

Well for starter i have a road angel and secondly i dont have a plate you work it out if you cant use the potentail of your FD sell it buy soimethin u will be happy with. speeds of 150+ occur every weekend you have no point and no leg to stand on your just ruining a perfectly good thread. and i know that bonnet lourves would not make a difference unless your bonnet is like a siv

let me know which roads u are doing this 150+ every weekend so i can keep out of the way for when u have ur accident..and please dont tell me u are such a good driver it is safe for u to do this speed

QuoteOriginally posted by Mr_7
Well for starter i have a road angel and secondly i dont have a plate you work it out if you cant use the potentail of your FD sell it buy soimethin u will be happy with. speeds of 150+ occur every weekend you have no point and no leg to stand on your just ruining a perfectly good thread. and i know that bonnet lourves would not make a difference unless your bonnet is like a siv

Mr sarcastic back again...
Now I speak with no detailed knowledge of areo dynamics so someone please correct me where I am a bit off beam but...

Down force is affected by the velocity of air passing under the car relative to the velocity of air flowing over it. As most cars are not flat at the top then the air will have a tendancy to flow faster over the roof line and this will inherantly provide lift at speed. All any areodymics expert can to, without providing positive pressure with Front and rear spoilers is to reduce this lift.

Now to speed up air flow under the car the ride height is commonly dropped. this has the effect of push air under the car at a higher rate with highest velocity, and hence negative lift, coming as the ride height approaches zero. This makes it tricky to negociate speed bumps on street cars but this principle was used on F1 cars in the 80\'s and 90\'s to increase downforce. This resulted in the death of Aryton Senna of course...

So consider the frontal area of the car. It has an intake for the radiator which allows air into the under bonnet cavity for cooling and intake, however not all of this air is used and it has to come out somewhere. Presumably by cirulating around the engine and belhousing before passing into the airflow passing underneath the car. As speeds increase and the airflow naturally passing under the car increase then it becomes harder for this air to pass out into this fast flowing stream and when it does it creates turbulance that increases drag and will, inevitably slow down this air flow thus creating lift.

Now it seems to me that a vented bonnet with vents correctly designed will act as a venturi sucking air out above the car thus reducing the total amount of air underneath the car. This would have the effect of reducing the natural lift generated at speed by creating a "vacuum" for want of a better word. (see ferrari f50, f60 etc etc)

As an aside you will of course have notice on all f1 cars that cooling air exits above the body work and not underneath it. (including the exhausts!)

Now onto rear spliters. These this are designed to improve the airflow from the rear of the car by reducing eddies and hence drag, thereby affecting top speed. Without the benefit of a larger smooth undertray the affect on lift will be limited.

Like most things on street cars it\'s as much to do with looks and personal preference, as a street car is inherantly compromised. If you want loads on downforce then I think a RX7 is not your thing! Even a F60 is compromised.

I have removed my rear wing and have not had a problem with a light rear end but then I don\'t do 150mph around corners where I would need the grip. but again it\'s horses for courses.

:)

mikeeech

thank you for sharing your knowlege this post is not meant to start a fight but instead for me to learn what i can by researchin this topic, your last post has tought me quite alot i satnd corrected and therefore apologise to you for what i said in the previous post.

The little other school girl comments from other members leaves alot to the imagination like should they have bought a french chav mobile and joined saxosportsclub.com?

if any of you would like to go for a drive out just a cruise or blat or meet il be happy to get to know some of you as i am a new member and do not want to start by making enimies. i attended the ace cafe meet and will be attending the reading meet tomorrow

I\'ll see you there tonight Mr 7, I\'m the bald one in the silver FD ;)

Max

Here\'s a good solution for rear downforce. I have a sneaking suspicion that it may create a little turbulence and adversely affect the handling.

QuoteOriginally posted by mikeeech
Now it seems to me that a vented bonnet with vents correctly designed will act as a venturi sucking air out above the car thus reducing the total amount of air underneath the car. This would have the effect of reducing the natural lift generated at speed by creating a "vacuum" for want of a better word. (see ferrari f50, f60 etc etc)

Hard to tell on an FD where the air that enters the engine bay goes to without vents but the undertray certainly keeps it from exiting underneath too quickly.  A few guys running without them had big cooling problems.  From what I remember of the underside of mine most of the air will leave at the bottom-rear of the bay on either side.  

Adding vents to the bonnet might have a small effect on air-pressures but not enough to create significant \'vacuum\' as all road cars are far too high.

Iain

I have a vented bonnet too! Some may say I\'m going for looks but it\'s just not true... it\'s all for downforce I tell ya!;) :D

We should get a wind tunnel day going and see what some of these options really do for the cars apart from making em look nice, would be quite interestuing and may be able to get a feauture in a mag too perhaps??

i have a vented bonnet too & wots more if you can supply the tunnel i have the wind lol
Si

Yes a wind tunnel day would be good but do they advertise such a day to joe public? i know suzuki cresent motorbikes do but never heard of car ones.

P.s that would solve the downforce problem maybe veliside should put it into production on the basis it increases it lol

you can hire MIRA\'s wind tunnel for the day, not sure how much it costs like. Maybee a mag like practical performance car might do a feature ?

http://www.mira.co.uk/site/what_research_facilities.asp

EDIT ... piccy of the CFD screenshot looks very much like an NB mx5

in the words of the great philosipher...

heres my 10 cents coz my 2 cents is free.

we all know that F1 cars can drive upside down at speeds of 130 ( or whatever it is) and this is all due to down force provided the the \'inverted wing\' on the back.

the problem is that there are three forces in play here and it seems to me they are getting confused...
firstly as I mentioned is downforce

secondly is drag

think of a plane... ( firstly I must state that my misses works for Airbus)  this has lift provided by the wings and secondly very low drag co-efficient provided by the aerodynamic shape of the plane.

thirdly is thrust...

if the drag goes up you need more thrust  to get it off the ground, and if the lift goes down you need more thrust or lower drag.

now on a car you want it to stick/push down to the ground, hence we have the problem of lift/drag/thrust (BHP).

now I am sure that even the FD was subjected to CFD ( thats computer fluid dynaimcs fro those that dont know ) plots and wind tunnels to maximise the effect of these three elements, and I am certain that the downforce as standard is such that it is in the capabilities of the car, or 15% over, depending on the margin of safety, so If you go and put another spoiler on the back, some big whale tail or something this will effect two of the three elements ie. drag and downforce( DF).  for straight line speed you want as little DF as possible. and as little drag as possible.

splitters between the back wheels will reduce drag by making the flow of air out of the back of the car smoother , but this will also make the down force greater, or have a greater effect as the drag will ahve dropped, adding an inverted wing will increase DF and will have a negative effect the amount of trust needed to get to a certain speed... as it will change the airflow over the top of tha car... increasing hte surface area it has to go over...

to an end... all of this make no difference when going round a corner as the direction of the forces invloved changes and the whole car pitches and so the airflow under the car will alter as will the flow over the car so this whole thread seems a little pointless!!!

Hurrah!

So, what happens if you strap an airbus upside down to the rear of an FD?

if its an A380 you end up with the worlds first waifer thin FD those things are going to be massive !

Airbuses aren\'t natural flyers as I understand it - they only stay up because the fly-by-wire is clever enough to keep attack angles correct!