User0083 Posted December 29, 2013 Share Posted December 29, 2013 I would like the Strakes, but i'm sure the whole thing looks a lot better, than performs. guest - I think this will just be in your head surely? I don't believe the car will handle any better with this attached. I honestly noticed a pretty big difference with mine. I thought I had wheel balance out, all balanced, then had tracking and camber done. Then swapped front wheels to rear and rear to front... Still vibrations at 55-60 and above. Continuing right through to what I went to, over 100, at 95-100 started feeling really light on the front and I didn't feel safe. So eased off pretty quickly. A few weeks later the diffuser was fitted and the vibrations went completely. The only change was putting my diffuser on (you could argue wind direction or speed as a possibility, but not noticeable) a few weeks later I got free run of an airfield again and went well above 100 and the car felt much more planted. I have now fitted bonnet pin's to secure it and next time I get runway time I'll do a comparison. Quote Link to comment Share on other sites More sharing options...
peet Posted December 30, 2013 Share Posted December 30, 2013 Steve if it doesn't handle any better why are they fitted? (Newbie question I know...) Quote Link to comment Share on other sites More sharing options...
Steve_Farrimond Posted December 30, 2013 Author Share Posted December 30, 2013 guest - I’ll take your word for it as I’ve had no chance to test my car since (weather etc...) Peet - they are fitted for down force. The theory is the front end of the diffuser is lower than the rear. say for example the front is 2 inches from the floor, there is a gap filled with air. as the car travels forward, the same air is then moved in to the area at the back, maybe 6 inches, this generates a negative air pressure and pulls the car down. Hope that makes some sort of sense. Personally, like I say I would be surprised if it would make any difference, but I am happy to become corrected. I simply fitted one because I feel that it looks better. Quote Link to comment Share on other sites More sharing options...
Dave Eastwood (Gadgetman) - Club Chairman Posted December 30, 2013 Share Posted December 30, 2013 There's really two questions here; how do diffusers work, and why fit one to a Westfield. They aren't necessarily the same thing! How they work is somewhat complicated and tricky to sum up. It's partly controlling the speed of the air flow under the car, creating low pressure zones etc, but also key is how they manage the air flow and importantly it's separation from the car, as it leaves the rear of the car: it's why most decent ones extend some distance from the rear bodywork. Googling the subject will get you some good, proper, explanations, with the vital pictures! (It will also waste a good while, if you start reading in depth ) Why fit them on a road-going Westfield though, that's a very different matter. A Westfield, as it comes from the factory, just doesn't have the aerodynamics or suspension set up to really let a diffuser work as intended. (The ride is too high/soft, meaning the diffusers uprights are too high off the road.) Most also don't exit far enough behind the car bodywork. However, if we think laterally, Westfields have a huge void where the diff and petrol tank sit and around the rear suspension. This has been shown to give something of a parachute effect. (You've also got a smaller opening beneath the prop shaft, and another larger opening beneath the engine). From the results of those that have experimented, it would appear that most of the benefits come from closing these openings. The "diffuser" just be a more "attractive" (in a petrol head sort of way) method of enclosing the rear opening. Whereas the engine bay and tunnel are typically just enclosed with aluminium or carbon fibre sheet. (Be aware though that this introduces issues of its own, such as cooling). But it's interesting, if you look at many reasonably modern cars that have been developed for any sort of performance/economy at motorway speeds, you'll find most have full length under trays. And this of course is the final "nail" in the coffin of the average road going* Westfield with a diffuser. (Mine included, if I ever get round to fitting it!). Apart from the height issue, to work as a diffuser, they also need good air flow management leading up to them. This means as smooth a floor as possible from the nose of the car, (excepting any special treatments in and around the splitter) back. The floor of the car also needs to blend smoothly into the splitter itself, otherwise, the airflow is already detaching, uncontrollably, before it's even got to the splitters Venturi section. Mine, if ever fitted, will be there to reduce the parachute effect and because I like the look! *Don't confuse some of the competition Westfields such as Speed Series cars you see with them, with regular road going models. Some are running fully flat floors, minimal ride heights, stiff springing etc. Quote Link to comment Share on other sites More sharing options...
peet Posted December 30, 2013 Share Posted December 30, 2013 Hi Steve, that was what I understood them to do but wasn't sure on a Westy. So it should improve the handling but doesn't much unless the cars lowered, tunnel and engine are closed in and is a bit longer is that correct Dave? More confused than ever now! Lol Quote Link to comment Share on other sites More sharing options...
Dave Eastwood (Gadgetman) - Club Chairman Posted December 30, 2013 Share Posted December 30, 2013 On the "average" road-going Westfield, i suspect it's best to think of them more as undertray with "styling"! As un undertray, they definitely do something, even when just used on their own. As an undertray, it would appear that at the very least, they reduce drag somewhat*. It's possible, but I can't say I've ever seen anything definitive, that they may reduce rear lift somewhat. But, as they don't work in the way diffusers are intended, the chances of them actually creating downforce would seem slim. *In measurable terms, a number of those that have fitted them do report improved range/fuel consumption for motorway style use. Very little has been done wind tunnel wise with Seven style cars, although there are some interesting articles based on some Caterham experiments. Attached is a summary of some tests done privately at Mira by a Caterham racer. Interestingly,part of his conclusion involved ditching the typical seven style splitter! But it's important to note the underfloor area of the Caterham is quite different to a Westfield in the diff/tank area. - Caterham is now here near as open, from what i can see. There's also an article based on some of Caterham's own work - some of which was used on the CSR available on the web. Page 1 Page 2 Page 3 miratest.doc Quote Link to comment Share on other sites More sharing options...
peet Posted December 30, 2013 Share Posted December 30, 2013 Thats an interesting read Dave, thank you. Think i'll stick with the simple style though... Quote Link to comment Share on other sites More sharing options...
Dave Eastwood (Gadgetman) - Club Chairman Posted December 30, 2013 Share Posted December 30, 2013 Agreed. Quote Link to comment Share on other sites More sharing options...
SootySport Posted December 30, 2013 Share Posted December 30, 2013 An interesting read Dave and as the MIRA engineers say it's easy to improve aerodynamics on a completely no aerodynamic car. The problem is, the car ceases to have the appeal of a simple 7 style car with all the aero bits fitted. I guess this why no 7 car producer goes all out to market aero packages. Lets leave them alone and enjoy the retro sports car look -----------well, maybe a tweak here and there . 1 Quote Link to comment Share on other sites More sharing options...
peet Posted December 30, 2013 Share Posted December 30, 2013 Yeah keep ya fancy aerodynamic cardboard bits! Diffuser does look good though... Quote Link to comment Share on other sites More sharing options...
Dave Eastwood (Gadgetman) - Club Chairman Posted December 30, 2013 Share Posted December 30, 2013 I agree Bernie. Fine if you're competing/building a track car etc, of even if that's just what floats your boat. But these days, from a road going Westfield, I want something a little different! Not necessarily retro, but not the track refugee look either Quote Link to comment Share on other sites More sharing options...
SootySport Posted December 31, 2013 Share Posted December 31, 2013 Just add power to push it along a bit faster Dave, Argh, you're doing that already. Quote Link to comment Share on other sites More sharing options...
alexander72 Posted December 31, 2013 Share Posted December 31, 2013 very good thread this - great article Dave - thanks mate My road legal SE sprint car needs all the help it can get in terms of going quicker and has a home made diffuser, enclosed tunnell and flat c/fibre floor. IMO the diffuser serves as a very effective small stone collector Quote Link to comment Share on other sites More sharing options...
Steve_Farrimond Posted January 2, 2014 Author Share Posted January 2, 2014 yeah I agree with all the above. I got mine just to look good and to keep the diff/tank area cleaner, as I tidied it al up at the back of the year. 1 Quote Link to comment Share on other sites More sharing options...
Dave Eastwood (Gadgetman) - Club Chairman Posted January 2, 2014 Share Posted January 2, 2014 yeah I agree with all the above. I got mine just to look good and to keep the diff/tank area cleaner, as I tidied it al up at the back of the year. Same me reason I bought one, and if it helps cruising milage a little, so much the better! (Saves getting off the motorway/dual carriageways after the drive to Wales and immediately hunting for the petrol stations!) Quote Link to comment Share on other sites More sharing options...
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