When will saxo owners be able to buy a DECENT DIFFUSER?!

[DanGT]

Oh and the only other piece of information worth noting is that at castle coombe, they made all the 205's in thier championships cut the rear bumper away as when they were going over avon rise (I think) the rear bumper catching so much air that the rear of the car lifted off the track and people were nearly killing themselves as they couldn't brake in time for the next corner!

But again, I have never heard about this on a saxo or 106 there.

[KamRacing]

To be honest I'd bet money on the diffuser being used to combat lift rather than active downforce. In which case it does it very well. I doubt anyone can expect more without a windtunnel.
Personally I find my clio RS fast but a little dull. The power is very linear and therefore lacks character. This is due no doubt to the VVT.
Back to aerodynamics. If you look at modern touring cars theres lots done to the front of the cars to help lower drag. A few run quite intricate undertrays to control airflow under the engine. I'll speak to a friend about the underside. He is chief mechanic on the Chevrolet WTCC cars

[hard_corejoeboy]

Interesting stuff! Soon i will be saxoless but hopefully this thread has given some food for thought etc

Kam i thought the clio was for fun in the corners not for speed

[DanGT]

Originally Posted by KamRacing

To be honest I'd bet money on the diffuser being used to combat lift rather than active downforce. In which case it does it very well. I doubt anyone can expect more without a windtunnel.
Personally I find my clio RS fast but a little dull. The power is very linear and therefore lacks character. This is due no doubt to the VVT.
Back to aerodynamics. If you look at modern touring cars theres lots done to the front of the cars to help lower drag. A few run quite intricate undertrays to control airflow under the engine. I'll speak to a friend about the underside. He is chief mechanic on the Chevrolet WTCC cars

The under trays will be designed to direct airflow to rads and brakes for cooling mainly. The cooling drag is considerably higher on a race car due to this. It would be great to hear his thoughts on it, WTCC is a big boys game. I used to know a couple of people who worked with BTCC but neither do now

I thought another reason for directing air in funky ways under tourings cars is because they aren't allowed to utilise ground effect, and its just a way of proving they aren't. Correct me if i'm wrong though. The aero of the spolier will be acting on the net lift, so I suspect thier 40kg @ 70mph will be the weight of the car at that speed, say 95% of its static weight or something is will be 40kgs more than that with the spoiler, which means it may be 98% of its static weight. Anywho all of this will be done in a wind tunnel and therefore the angle/veins/length/sweep/width/exhaust can all be fine tuned to make a difference.

Interesting fact, an F1 car generates more drag than a VW camper van. This is due to the downforce, the more you have the more air you are displaceing, therefore the more drag you have caused. This is why they have big HP to overcome the drag, and also why they are much slower in drag races than older F1 cars with less aero, but the trade off is higher cornering speeds.

I would say the best things you can do aerodynamically on a saxo for not much money are bonnet lifters (to help relieve pressure in the bay), possibly a flat floor (depending on material for cost), and a roll of duct tape for sealing panel gaps

Oh and I agree with you about the clio RS engine, it does lack a little. But the same can be said of much faster and more expensive machinery. M3 seems a fair comparison, but this is much more expensive. BMW nailed it with the CSL tho. We need a Clio RS200 CSL, for about £15k

[axsaxoman]

Originally Posted by hard_corejoeboy

Performance French Car Magazine Clio 200 Review October 2009 Page 52.

I quote:

'As per the 197, found on both models is a rear diffuser. For those who look at this as a gimmick, it creates 40kg of rear downforce at 70mph and up to 70kg as speeds increase'

When said car reviewer is going to be be team mate to Walter Rohl driving a GT3 RS at the Nurburgring 24hrs i think im going to listen to him and his opinion on cars not someone thats a member of sax-p to be honest.

Anyway if we could please move on as all this thread seems to be is an attack on my beliefs and opinions.

I think I will suffer no downforce and not effectually carry a passenger when on the track ,thank you
,only upside is it will help the braking ,or feel like you have applied a little braking on over -run
or look at it another way

all the time you spent making it lighter has just been wasted by fitting the aero device ,and you have had to pay for it as well to make it go slower.LOL

[hard_corejoeboy]

I don't think anyone can genuinely say whether aero works or not lol
Im assuming some ridiculous degree and a wind tunnel would sort this.

[adamskiTNR]

I find it very hard to comprehend that a diffuser on any hatchback could even be used solely to reduce lift. as to do so would need to produce net downforce. And the ONLY way it does this is by accelerating air travelling under the car through a "small" void, small enough to keep the boundary layers laminar while travelling under the car to keep the pressures reliable in pressure. This does not exist on a saxo without a flat floor and all sorts of geometry changes to get it low enough. And with a standard underfloor the fluid paths will become erratic and the flow turbulent.
And before anybody starts saying that it assists other aerodynamic devices then again, a flat floor would be needed to assist the front splitter, and their would be no relationship between a diffuser and a rear spoiler on a hatchback, as there would be on the lower beam wing of a formula car.

One of the most overlooked purposes of a diffuser is just to reduce drag by rejoining the flow from under the car to the upper flow, and delivering it in a laminar form so as to keep drag to a minimum. (this is what the strakes in a diffuser are for).

ermm, that's about all i have to say

[hard_corejoeboy]

I didn't understand half of that mate but nice try!

If a clio can be made to have an effect then surely someone out there must be better than renault!

[adamskiTNR]

To be fair i would like to know what renault did for the test and what they used as the "control" rear end to verify the results.
I would like to know the facts before i took it with any seriousness.
They could have made a really shit rear end to start with and then the weights suddenly go up by 40kg.
a bit like DFS sale prices.

[hard_corejoeboy]

lol yeah i would also like to know how they did it. Can i just say i only use the clio as an example as most 'normal' people can afford one. I could have brought up the Ferrari FXX but that would be pretty pointless!

I'd assume its true though as they are a big car maker and they can't just go round making false claims. Saying that they did it with their power figures with the 172 and 182 lol

[adamskiTNR]

If there's is one thing that i can leave you with, let it be this.

No, being so big and having so many intelligent people employed, they cannot lie.
However, being so big and having so many intelligent people employed, they can deceive.

[kristel10589]

Originally Posted by DanGT

The under trays will be designed to direct airflow to rads and brakes for cooling mainly. The cooling drag is considerably higher on a race car due to this. It would be great to hear his thoughts on it, WTCC is a big boys game. I used to know a couple of people who worked with BTCC but neither do now

I thought another reason for directing air in funky ways under tourings cars is because they aren't allowed to utilise ground effect, and its just a way of proving they aren't. Correct me if i'm wrong though. The aero of the spolier will be acting on the net lift, so I suspect thier 40kg @ 70mph will be the weight of the car at that speed, say 95% of its static weight or something is will be 40kgs more than that with the spoiler, which means it may be 98% of its static weight. Anywho all of this will be done in a wind tunnel and therefore the angle/veins/length/sweep/width/exhaust can all be fine tuned to make a difference.

Interesting fact, an F1 car generates more drag than a VW camper van. This is due to the downforce, the more you have the more air you are displaceing, therefore the more drag you have caused. This is why they have big HP to overcome the drag, and also why they are much slower in drag races than older F1 cars with less aero, but the trade off is higher cornering speeds.

I would say the best things you can do aerodynamically on a saxo for not much money are bonnet lifters (to help relieve pressure in the bay), possibly a flat floor (depending on material for cost), and a roll of duct tape for sealing panel gaps

Oh and I agree with you about the clio RS engine, it does lack a little. But the same can be said of much faster and more expensive machinery. M3 seems a fair comparison, but this is much more expensive. BMW nailed it with the CSL tho. We need a Clio RS200 CSL, for about £15k

Cooling for rads etc and brakes is done above the floor of most race cars. All they use the underside for is to create downforce.
I doubt Renault would have even imagined testing the clio in a wind tunnel, hell it costs thousands to run a wind tunnel, let alone prototyping,developing/testing and 'fine' tuning it LOL. thats just obsurd.it would have just been done on computer program simulators.

Originally Posted by hard_corejoeboy

lol yeah i would also like to know how they did it. Can i just say i only use the clio as an example as most 'normal' people can afford one. I could have brought up the Ferrari FXX but that would be pretty pointless!

I'd assume its true though as they are a big car maker and they can't just go round making false claims. Saying that they did it with their power figures with the 172 and 182 lol

Who would go out and buy a car because the manufacture said the car produces x amount of downforce at x amount speed?
So i doubt anyone going to be sueing if they found out that renaults facts were incorrect.
The ferrari fxx I believe will have an ground effect that is more suitable then the clio.

The ferraris diffuser I would imagine would start alot nearer the front of the car then the clio would and alot better in design and will actually work. Your comparing a clio to a race bred ferrari!

[axsaxoman]

Originally Posted by hard_corejoeboy

I don't think anyone can genuinely say whether aero works or not lol
Im assuming some ridiculous degree and a wind tunnel would sort this.

sorry you are wrong .
yes we can say that fitting a spoiler to rear of car will cause downforce +drag
and we can say for sure that you cannot get a saxo close enough to the ground for any flat floor to work .I have tired it 10years ago+lap tmes were not different +we fastest car in the class with the lap record for class
that is fact ..
If these things were not subject to the laws of physics then ti could be doubted .but they are not .
you might as well say theat you cannot prove if an aircraft wing will work ,but its very simple ,you make the air travel further over one side than the other and you get lift ,
quantifyinh is another matter .
and there is no way you can run a road car with 2" or lless ground clearance .you will find nearly all race series have a minium height of 50mm --that is because you cabnnot get any appreciable amount of effect from a flat floor above that height .
its not a single seater its a the shape of a brick shithouse ,so all you really get is downforce by creating drag and not remove drag by cutting turbulent aie from underside .
drag means more bhp to push to forward
drag goes up by the suare of the velocity ,so to get anything worht having means faster speeds and more bhp to push onto the ground .
you fit diffusers for bling---nothing else on a road /track day car

[KamRacing]

Originally Posted by adamskiTNR

I find it very hard to comprehend that a diffuser on any hatchback could even be used solely to reduce lift. as to do so would need to produce net downforce.

What I'm saying is its may not be enough to give positive downforce, but it produces enough to limit lift and stabilise the rear end.
Now we have people saying you have to have a perfectly smooth underside, but is that to be at optimum or can a nearly flat underside work? Obviously we can read our books and speculate based on theory as last time I looked not many people can afford a full scale windtunnel in their shed, but considering the size of the diffuser on the clio, i'd expect there to be some difference over none, but maybe not a lot. Its never going to be optimised as its been styled to suit the look of the car.
In summary I would not expect a clio or saxo to get a proper diffuser fitted and then suddenly romp into the distance with epic handling, but a more stable car is easier to drive consistently on the limit but maybe more likely that you will just scrap your ankle on it, and never notice anything when in the car..

[c7borg]

Originally Posted by kristel10589

There is a difference between an effective diffuser and and cutting body work to reduce drag. Totally two different and seperate issues lol.

Ummm der.. fear not I have read


So I appreciate the difference. The post has established you won't get a diffuser making any difference on a Saxo due to ride height and lack of flat underside, so I was commenting on the only thing that might help a Saxo and that was to reduce drag.. ie my point helping the air exit through the rear bumper although I think I know the answer

[kristel10589]

Originally Posted by c7borg

Ummm der.. fear not I have read


So I appreciate the difference. The post has established you won't get a diffuser making any difference on a Saxo due to ride height and lack of flat underside, so I was commenting on the only thing that might help a Saxo and that was to reduce drag.. ie my point helping the air exit through the rear bumper although I think I know the answer

sorry I thought this thread was about diffuser and therefore creating downforce/positive pressure/ground effects, not anything to do with just reducing drag. Can I add to your list that other things you could do to lower drag lol, Take wing mirrors off, enclose the wheels so the air isnt going into them, remove arieal......You see the list is endless and will give a total of advantage of nil!

Also aerodynamics to actually work, needs extensive testing, actually cutting the rear bumper could hinder then help. But hey you must be an expert, you read the haynes lol.

[kristel10589]

Originally Posted by axsaxoman

sorry you are wrong .
yes we can say that fitting a spoiler to rear of car will cause downforce +drag
and we can say for sure that you cannot get a saxo close enough to the ground for any flat floor to work .I have tired it 10years ago+lap tmes were not different +we fastest car in the class with the lap record for class
that is fact ..
If these things were not subject to the laws of physics then ti could be doubted .but they are not .
you might as well say theat you cannot prove if an aircraft wing will work ,but its very simple ,you make the air travel further over one side than the other and you get lift ,
quantifyinh is another matter .
and there is no way you can run a road car with 2" or lless ground clearance .you will find nearly all race series have a minium height of 50mm --that is because you cabnnot get any appreciable amount of effect from a flat floor above that height .
its not a single seater its a the shape of a brick shithouse ,so all you really get is downforce by creating drag and not remove drag by cutting turbulent aie from underside .
drag means more bhp to push to forward
drag goes up by the suare of the velocity ,so to get anything worht having means faster speeds and more bhp to push onto the ground .
you fit diffusers for bling---nothing else on a road /track day car

+1, hell even wrc cars don't run diffusers, even on ashphelt and people here think that the clio diffuser works lol

[axsaxoman]

then there is the what they do for fuel economy competitions --tape all the door ,bonnet + boot gaps + remove the wipers,but is it worth the bother ,when you can just keep your foot off the brake pedal for another 10yards before the corner and gain much more in a lap time.If every time you brake the car is not starting to sqirm about or just on the edge of locking the rear wheels --you ain,t braked late enough,and another 10-20 yds at 40mph quciker will do alot more to lower your lap time than anything else

[hard_corejoeboy]

The clio diffuser DOES work the corsa vxr's etc don't do anything. Even if it does precious little, every little helps. Besides why spend all that money designing a large rear diffuser that does bugger all? Renault can't even be assed to design a new dash for the cup models so they won't waste monye on something that does nothing im sure.

I think it was in PFC that the Clio Cup guys were saying that with the new front bumper and diffuser on the 200 they could really feel the difference and these guys race for a living...

Anyways bored of the clio, bored of the drag, bored of it not working on a saxo.

Is anyone actually going to design one that looks good and maybe does a little?

[kristel10589]

Originally Posted by hard_corejoeboy

The clio diffuser DOES work the corsa vxr's etc don't do anything. Even if it does precious little, every little helps. Besides why spend all that money designing a large rear diffuser that does bugger all? Renault can't even be assed to design a new dash for the cup models so they won't waste monye on something that does nothing im sure.

I think it was in PFC that the Clio Cup guys were saying that with the new front bumper and diffuser on the 200 they could really feel the difference and these guys race for a living...

Anyways bored of the clio, bored of the drag, bored of it not working on a saxo.

Is anyone actually going to design one that looks good and maybe does a little?

how do you know them drivers werent paid to say it? it could be a million n one things that they could have contributed to the handling.

does the clio diffuser start at the front of the car?

no one is going to waste there money,time and resource for something that will do nothing. in this section we dont care what things look like over function.