Rescued attachment alan.jpg
got bored made a diffuser
Rescued attachment alan.jpg
ooh lookin good 
whats it made of?
Interesting, seen a couple today out on our blat and am wondering if they actually do anything or just look bling.
Whats the benefit of having one on the car?
Steve
creates lots of downforce and reduces drag i believe
1.2mm ally some rivits and satin black paint and around an hour out of the mad house i call home , just bling as far as im bothered
and
cost £11
[Edited on 12/4/09 by afj]
i'd quite like one on the truck, to fill up an ugly space under the back panel, thing is, i don't really want to put a floor under the whole car... there's a lot of space to cover
Very nice i wonder where you got that idea from and who you copyed that of
ive spent the last two days making something for the car hopefully when they are finished they will look very 
will be at least another
couple of weeks till there finish thats all im saying for now apart from top secret
how far under the rear tub have you gone with it, is it all the way to the cookpit or just for the bling. v cool by the way.
rob
I hope it's within the regulations
Regardless of whether it actually does generate downforce or not, it must at least help in some ways on a seven. The rear panel with the space
beneath open must act at least in some way as a parachute, so covering it up has to be an improvement. Whether it actually generates downforce is
surely just an added bonus if it does?
All you need to do now is stencil Brawn GP on it and it'll be even quicker
Very nice in black!
There must be something in the air 
, I've just fitted one also, covers all the parachute area and fills the empty space at the rear. Got the
idea from Snetterton a few weeks ago.
Description
[img][/img]
quote:
Originally posted by A1
creates lots of downforce and reduces drag i believe
quote:I'd beg to differ.
Originally posted by mr henderson
quote:
Originally posted by A1
creates lots of downforce and reduces drag i believe
Only if they can overturn the laws of physics.
Either lots of downforce, or reduce drag. Not both.
John
just noticed snap off we must have got regestered almost together just 6 plates out
[Edited on 12/4/09 by afj]
oh underneth its as big as the rear panel area the only gap in the floor now is the curved section under the diff
[Edited on 12/4/09 by afj]
Yes, Matt.c is one number from mine too.
quote:
Originally posted by afj
just noticed snap off we must have got regestered almost together
[Edited on 12/4/09 by afj]
quote:
I'd beg to differ
Actually diffusers add down force without producing much drag. Wings create drag for obvious reasons, this being that there is basically a big plate
at an angle to the airflow. Because it is a wing it has a high pressure area above it and a low pressure area below it creating the downforce. Also
because of this the high pressure trys to get into the low pressure area and creates a vortice, (seen in Malaysia due to the high humidity). This is
also drag as its dirty air. (why all passenger aircraft have the vertical winglets on the end of the wings, reduces the drag so they use less
fuel).
A diffuser is used by making the entire bottom of the car flat, (making the air move faster under this area due to being compressed), when it reaches
the diffuser which turns upward the air decelerates creating low pressure which is the downforce. All the vertical winglets stop the air from
seperating and all this creates very little in the way of drag. Cant get something for nothing!!!
Hang on a minute, are we talking about aerodynamics and sevens in the same thread here Come on guys, do you really think that making your own
diffuser and sticking it on is going to increase your downforce? They make an otherwise dull but very visible area look interesting, that's
about it.
Phil
I think generally speaking underbody aerodynamics such as these are designed to employ ground effect principles and therefore are very favourable as
they induce very little drag for the downforce that they create and possibly can even can reduce drag by preventing turbulent air from exiting the
rear of the car.
By increasing downforce you do not inherently increase drag as downforce is, broadly speaking, a vertical force and the drag induced by it
horizontal.
Very simple explaination from a non-aero engineer there , better info here:
http://www.symscape.com/blog/secrets_of_diffusers
Andy
Edit: Damn, been beaten to it.
[Edited on 12/4/09 by andylancaster3000]
I agree with Phil wholeheartedly. Though I must say and I'm not trying to start an argument , it is something that interests me having studied it in the RAF (and was crap at!) just a conversation but your explanantion sounds not quite right in a few places iiyama.
i made it in the shed, sprayed it black and rivited it on. i for one dont care if it does anything but the diffuser serves 2 perposes 1. it
kept me out the house for a bit and 2. it looks nice
To add actually, I think in a practical sense a diffusery looking thing can be useful but maybe not in the normal manner. In most situations the under
axle area of 'seven' is unskinned. By having something there like a 'diffuser' to stop the air going up there I would have thought
it'd help out quite a bit. Yes this isn't going to solve all seven type car aerodynamic issues but every little helps
[Edited on 12/4/09 by andylancaster3000]
[Edited on 13/4/09 by andylancaster3000]
quote:
Originally posted by iiyama
when it reaches the diffuser which turns upward the air decelerates creating low pressure which is the downforce. All the vertical winglets stop the air from seperating and all this creates very little in the way of drag. Cant get something for nothing!!!
We made ours to keep the diff and driveshafts clean I reckon it smoothes the airflow just about as much as washing and polishing the bodywork
panels which altogether, should equate to a 2 second reduction in our lap times at Teeside.
Phil
[Edited on 12-4-09 by Hellfire]
Without any modelling, my gut feeling is that the increase in drag due to a diffuser (not disputing that there is) is less than the reduction in drag
from skinning the boot floor. The nett result being an overall increase in downforce and an overall decrease in drag.
Question for those with soft boot covers (or those that follow mates who have a soft boot cover) - Does the boot cover get pushed up, sucked down or
just flap about aimlessly at speed?
quote:
Originally posted by Ivan
quote:
Originally posted by iiyama
when it reaches the diffuser which turns upward the air decelerates creating low pressure which is the downforce. All the vertical winglets stop the air from seperating and all this creates very little in the way of drag. Cant get something for nothing!!!
I don't agree with this, basically you have to accelerate air to reduce pressure, not decelerate it.
I think what the diffuser does is exactly what it's name suggests, gives the air an easy escape from under the car without the turbulence the suspension etc. would cause and "diffusing" it into, the hopefully, low pressure slipstream at the back thus increasing the airspeed under the flat bottom before it and hence lowering pressure and hence increasing downforce.
In fact it might even reduce drag by reducing the turbulence behind the car.
:
I have a soft boot cover and to be honest its the last damn thing i look at when i am driving, but as far as the diffuser , i think it looks great and
should work by smoothing the air flow out the back, and as said before any little thing helps, i would'nt mind one.
Right then, thats enough, I'm going out to make one. Two reasons now, looks cool and keeps the diff and shafts out of the air and
clean
Ta,Steve
Can you do some back to back testing in a wind tunnel Steve and let us know the drag co-efficients before and after fitting the diffuser?
Phil
Made mine purely for the same reasons a Alan 1, i think it looks nice 2, i had a sheet of carbon look abs left over from trimming the car 3, gave me
something to do on a wet weekend last winter. really don't give a monkeys if it dose anything apart from look nice
More importantly Moto Gp on soon
Rear diffuser
Get in the garage, MotoGP cancelled...
Wind tunnel testing?? Your kidding, 8K along the local B roads is my kinda testing
as been said - when i decided to make my diffuser there were a few benefits for very little downsides
for -
air travelling under the car in a narrow space speeds up (venturi effect - narrowing of a space the same air mass moves through at the same speed
makes the air speed up - hence jet engines - carburettor venturi's) - so if the air is travelling faster it creates lower pressure under the car
as it is moving faster than the air above the car - the air pressure above the car then pushes more down on the top of the car..
it also helps stop the rear boot box area being a 'parachute' effect - air under the car gets snagged on the rear end
the air on a car without a diffuser creates votices which create drag on the vertical boot box area - by forcing the air further away from the back of
the boot box area (diffuser sticks out from the back on mine by about 8" or so) it helps to stop the vortice drag
it also has the benefit of stopping the crud build up on the suspension etc
the diffuser has to be level with the bottom of the car really to work - so its keeping the narrow floor / road gap but just extending it.
when you look at a seven type car there really isnt that much difference between a single seater car - the biggest being the open cockpit acting like
a parachute - the front wings cause a lot of drag - headlights.. roll bars are not good either..
lol the whole car then...
the only real downside is the ground clearance - it needs to be low to work right - but going low can compromise speed bump clearance.. depends on
your individual car suspension travel
Terry, yours looks very purposeful indeed, however I will make mine a bit more discrete.
Just one more question.. do you need to cover the WHOLE of the rear boot place? including the area where the wishbones are??
Steve
you cant cover it all really - with the bones going droop on 'errrr airborne' sections they may catch.. i just put some small bends in the
ally to miss. the diffuser goes the width of the floor
better pics
[Edited on 12/4/09 by :{THC}:YosamiteSam]
[Edited on 12/4/09 by :{THC}:YosamiteSam]
Mmmm they look good.
There are various ways of conducting the air around a car, and some of them are better than others, and produce different results.
Never-the-less, if a car is pushed downwards that push has to come from somewhere, and there can only be one source of that push, the engine Unless,
of course, the wind happens to be blowing from a convenient direction
John
made one for mine... decided not to fit after reading other threads.
Main thing bothering me is, what about the air that goes thru radiator circulates around engine then squeezed down tunnel?
If you practically cover boot floor with diffuser how doe s this "dirty air" escape?
Might look nice, but i want to go faster not slower!
quote:
Originally posted by skippad
made one for mine... decided not to fit after reading other threads.
Main thing bothering me is, what about the air that goes thru radiator circulates around engine then squeezed down tunnel?
If you practically cover boot floor with diffuser how doe s this "dirty air" escape?
Might look nice, but i want to go faster not slower!
Anyone got some pics of the part before fitting? Saw this today at Detling and thought it looked very smart
Damn i should really worry about finishing the car and getting it tested before i start with mods
[Edited on 13/4/09 by bassett]
quote:
Originally posted by :{THC}:YosamiteSam
quote:
Originally posted by skippad
made one for mine... decided not to fit after reading other threads.
Main thing bothering me is, what about the air that goes thru radiator circulates around engine then squeezed down tunnel?
If you practically cover boot floor with diffuser how doe s this "dirty air" escape?
Might look nice, but i want to go faster not slower!
because the boot floor isnt covered over completely - there are gaping holes where the suspension arms attach
thanks for the invite - didnt see the thread till now! just come out of garden - workshop all day and goosed.. cars broken too.. need a gear selector spring.. will sort one out tomorrow
Hi
Just a quick word of warning. By covering up the diff etc. You do run the risk of getting the oil rather hot. On the Kit race cars we can run the
diffusers for the short 15-30 minute races. But when testing in 1hr sessions the diff oil gets way to hot. Just be wary when on those long road trips
or when blatting for a length of time.
Cheers Matt
A vent in the rear panel would be a good way of releasing traped air,when using a diffuser,as Caterham did with there RST V8
Rescued attachment 94E76095E5AC217AC253645F27E2B.jpg
Another pic of the Caterham:
Description
quote:
Originally posted by iiyama
Actually diffusers add down force without producing much drag. Wings create drag for obvious reasons, this being that there is basically a big plate at an angle to the airflow. Because it is a wing it has a high pressure area above it and a low pressure area below it creating the downforce. Also because of this the high pressure trys to get into the low pressure area and creates a vortice, (seen in Malaysia due to the high humidity). This is also drag as its dirty air. (why all passenger aircraft have the vertical winglets on the end of the wings, reduces the drag so they use less fuel).
A diffuser is used by making the entire bottom of the car flat, (making the air move faster under this area due to being compressed), when it reaches the diffuser which turns upward the air decelerates creating low pressure which is the downforce. All the vertical winglets stop the air from seperating and all this creates very little in the way of drag. Cant get something for nothing!!!
quote:
Originally posted by nstrug
quote:
Originally posted by iiyama
Actually diffusers add down force without producing much drag. Wings create drag for obvious reasons, this being that there is basically a big plate at an angle to the airflow. Because it is a wing it has a high pressure area above it and a low pressure area below it creating the downforce. Also because of this the high pressure trys to get into the low pressure area and creates a vortice, (seen in Malaysia due to the high humidity). This is also drag as its dirty air. (why all passenger aircraft have the vertical winglets on the end of the wings, reduces the drag so they use less fuel).
A diffuser is used by making the entire bottom of the car flat, (making the air move faster under this area due to being compressed), when it reaches the diffuser which turns upward the air decelerates creating low pressure which is the downforce. All the vertical winglets stop the air from seperating and all this creates very little in the way of drag. Cant get something for nothing!!!
^^^^^
All spot on...
Diffusers (and ground effects in general) increase downforce without significant drag.
Nick
quote:
Originally posted by locoR1
Made mine purely for the same reasons a Alan 1, i think it looks nice 2, i had a sheet of carbon look abs left over from trimming the car 3, gave me something to do on a wet weekend last winter. really don't give a monkeys if it dose anything apart from look nice
More importantly Moto Gp on soon
Rear diffuser
To bend it use a heat gun to warm it up sounds easy but like most things its not
The most important thing is start of practising on small off cuts i did a lot of 90deg bends when trimming the car radius's are harder you only
want to heat the bend not the surrounding abs otherwise it ripples.
To do the diffuser i made a former out of wood to bend it over clamping wood ether side to protect the sheet and just warmed and folded the bend.
quote:
Originally posted by locoR1
To bend it use a heat gun to warm it up sounds easy but like most things its not
The most important thing is start of practising on small off cuts i did a lot of 90deg bends when trimming the car radius's are harder you only want to heat the bend not the surrounding abs otherwise it ripples.
To do the diffuser i made a former out of wood to bend it over clamping wood ether side to protect the sheet and just warmed and folded the bend.
Its the thinner of the two sizes usually available its about 3mm if i remember right!
can you recomend anywhere to get some on line, gooled ABS sheets and for a sheet 1800mm wide 1000mm long, enough for the side drops and centre flaps
etc £80 for 3mm in carbon 
Its not cheep! i think i payed just over £100 did all my interior and the diffuser for that and ive still got some small bits left mine came from
esp-plastics the main page of the link below works but not the sub pages so not sure if they are still trading!
http://www.esp-plastics.co.uk/kitcar.html
Cheers mate, i was wasn't sure if £80 was a bit much or the going rate,