Diffuser for rear of Griffith
Discussion
Quinny said:
Ah but the arse end on a Chim probably needs a bit of help
Wheras the Griff, well let the photos speak for themselves really
Does it really need somthing adding? I just don't see it.
Wheras the Griff, well let the photos speak for themselves really
Does it really need somthing adding? I just don't see it.
You reckon
Everybody I know loves the rear end of the Chim over a Griff,if it was a bird i'd shag it.
Markh - who's working on your Chimaera diffuser? I was going to talk to Tim at ACT about designing and making one in Carbon Fibre.
Quinny - Don't worry - I think the Griffith rear looks fab too - I'm talking about something very discrete - it would span the full width and incorporate the twin tailpipes. Hopefully give some real downforce so would have to be physically attached to the chassis.
I would also like to design a better spoiler for under the nose as well - hey let's make a full smooth undertray in CF - anybody got access to a wind tunnel?
Ricardo
Quinny - Don't worry - I think the Griffith rear looks fab too - I'm talking about something very discrete - it would span the full width and incorporate the twin tailpipes. Hopefully give some real downforce so would have to be physically attached to the chassis.
I would also like to design a better spoiler for under the nose as well - hey let's make a full smooth undertray in CF - anybody got access to a wind tunnel?
Ricardo
No problem doing it for looks, but if you're doing it for aerodynamics you'd need to overcome a few issues to get it to work. The main ones are that for it to diffuse effectively you would need attached flow through the diffuser, which means providing a smooth air flow to the front of it, which means you need to smooth over the underneath of the car. That's doable but you'd probably need to allow some cooling for the sump, exhaust and transmission which means you'd be limited to two channels down the sides rather than a full width undertray. The next problem is to avoid obstructions within the diffuser itself. The exhaust is right in the way and you'd need to either run a central exhaust or put the diffuser completely under the exhaust (which limits the size of diffuser you can fit. Then you need to find a way to reduce the entrained air coming in past the sills, presumably you aren't willing to drop the ground clearance to almost nothing so you'd have to see how far you could get with spoilers along the sills. To get any really dramatic benefit you'd need to connect the back of the diffuser up to the low pressure area of a rear wing, but realistically that isn't going to happen. So if you're lucky and it works after all that, the benefits would be small until you get to three-figure speeds. If you're unlucky you could end up increasing lift and drag. A far safer bet is simply to fit a front air dam.
Yep I'm with Pete on this one. I have played with rear diffusers and getting them to work is really difficult as Pete says. In the end I went with a splitter and front air dam and some other tricks and that reaped a lot of benefit. The downside is that ground clearance starts to become an issue as the better the seal, the bigger the benefit.
There is certainly a Chimaera that has had one fitted but it is more cosmetic than anything.
There is certainly a Chimaera that has had one fitted but it is more cosmetic than anything.
Aren't TVR Power working on aero mods for the Griff to go with the supercharging developments?
www.tvrpower.co.uk/sc.supercharger.php
www.tvrpower.co.uk/sc.supercharger.php
shpub said:
Yep I'm with Pete on this one. I have played with rear diffusers and getting them to work is really difficult as Pete says. In the end I went with a splitter and front air dam and some other tricks and that reaped a lot of benefit. The downside is that ground clearance starts to become an issue as the better the seal, the bigger the benefit.
There is certainly a Chimaera that has had one fitted but it is more cosmetic than anything.
There is certainly a Chimaera that has had one fitted but it is more cosmetic than anything.
Why hasn't a diffuser worked?I'm presumming this is on your racecar,have you a full undertray?
It was due to difficulties getting a flat undertray without introducing overheating problems and controlling air spilling out from the sills. I couldn't get the car low enough as well. Looked at my I spy book of aerodynamic aids and went the front splitter and air dam route instead. Current system has a splitter and underneath that is a rubber airdam that virtually touches the ground. The air dam stops any air from getting under the car. I removed the rear under spoiler so that there is as clear an exit route as possible but that is it. The splitter then has a big vent in it so that air that hits the front of the air dam but under the splitter is directed up and through the radiator and out over the top through another big vent in the bonnet. The normal front radiator intake is very small or even completely blocked off. This helps with maintaining the high pressure zone for the splitter.
Overall effect is to gain downforce from the splitter and to remove lift. It also helps get a very good air flow through the rad without flowing the air into the engine bay where it can struggle to escape.
It does work well as when I have broken bits of it, the effect is quite noticeable. The splitter is now made of ply as it is very cheap to replace. BTW the Le Mans racer also had its splitter made from ply.
Not against defusers but they are a lot of work to get working right and there are other ways of gaining aero advantages or creating a low pressure zone under the car.
Overall effect is to gain downforce from the splitter and to remove lift. It also helps get a very good air flow through the rad without flowing the air into the engine bay where it can struggle to escape.
It does work well as when I have broken bits of it, the effect is quite noticeable. The splitter is now made of ply as it is very cheap to replace. BTW the Le Mans racer also had its splitter made from ply.
Not against defusers but they are a lot of work to get working right and there are other ways of gaining aero advantages or creating a low pressure zone under the car.
GreenV8S said:
If you're unlucky you could end up increasing lift and drag. A far safer bet is simply to fit a front air dam.
This is the bit that worried me, I saw a cerbera a few years ago (christof)that had an interesting splitters front and rear which I assumed worked properly (did I hear the body kit was £5k>? so I hope it worked for that money!).
I know it wold look wrong on the Chimaera but dose the rear splitter on a Tamora do any good? or just cosmetic
Edited by markh on Thursday 23 November 09:57
Edited by markh on Thursday 23 November 09:58
richb said:
It's been done on a Griff that races but I can't remember which one, I'm sure someone will post up a picture.
Marc Hockins car ( the one that came second
) has a rear diffuser, marc reckons it makes a noticable difference. There'll be a pic on the tuscan challenge forums somewhere
G
shpub said:
air that hits the front of the air dam but under the splitter is directed up and through the radiator and out over the top through another big vent in the bonnet.
The splitter is well worth having of course, and a pretty safe bet because it will always work if you make it big enough. I suspect you're getting massive gains from the big bonnet vent you have and these probably outweigh the other features by a large margin. That area of the bonnet is one of the lowest pressure areas on the car, and connecting it to the underbonnet area means you reduce the suction above the bonnet, reduce the pressure below it, and this will carry back to a smaller degree over the whole floorpan. You only need a small pressure difference over a big area like that to do something useful. Even with that sort of thing you will be lucky if you manage to overcome the lift let alone produce net downforce, and you will need to be well into three figure speeds before the benefit is enough to matter. And if you do start to get significant forces you need to worry about the balance as well as the amount, many of the bigger easier wins that produce downforce at the front can result in increased lift at the rear. For a road car I think the performance benefits of aero mods like this are negligeable and the only reason to do it is for the looks.
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