Diffusers non flat underneath.
Discussion
carl carlson said:
Thought as much so why do Ferrari 599s come with a diffuser but if you stick you head underneath you can see the transmission tunnel, gearbox and other gubbings? Doesn't seem to make sense.
Fashion. Diffusers don't do much on road cars anyway, they tend to ride too high.
Sam_68 said:
kambites said:
Fashion.
Diffusers don't do much on road cars anyway, they tend to ride too high.
This. They're little more than chavtat bling unless you're running a 40mm ride height.Diffusers don't do much on road cars anyway, they tend to ride too high.
LukeBird said:
Hardly 'chavtat bling', just vastly less efficient given the raised ride height of road cars.
About as effective as those huge wings you see on the backs of 1.2 hatchbacks occasionally. 
I'm fairly convinced that mine does absolutely nothing, I've driven the car with the diffuser removed and I couldn't tell the difference.
I suppose the important thing is actually the ratio of the volume of air under the diffuser to the volume diffused by the diffuser?
kambites said:
LukeBird said:
Hardly 'chavtat bling', just vastly less efficient given the raised ride height of road cars.
About as effective as those huge wings you see on the backs of 1.2 hatchbacks occasionally. I'm fairly convinced that mine does absolutely nothing, I've driven the car with the diffuser removed and I couldn't tell the difference.
I suppose the important thing is actually the ratio of the volume of air under the diffuser to the volume diffused by the diffuser?
Having followed an SLR down the motorway, where cement (presumably) had been used to soak up oil on the carriageway, I could see the plumes of dirt being drawn up by the acceleration of air out of the diffuser.
Agreed though, most are just pointless!
LukeBird said:
A 'proper' aero developed car (any modern hypercar, CGT etc. or a fair few modern Ferraris etc.) will develop a fair bit of downforce at high speed, but obviously not a lot lower down and barely anything below 100mph.
Having followed an SLR down the motorway, where cement (presumably) had been used to soak up oil on the carriageway, I could see the plumes of dirt being drawn up by the acceleration of air out of the diffuser.
Agreed though, most are just pointless!
Don't most modern hypercars lower their ride height above a certain speed, though, for this very reason?Having followed an SLR down the motorway, where cement (presumably) had been used to soak up oil on the carriageway, I could see the plumes of dirt being drawn up by the acceleration of air out of the diffuser.
Agreed though, most are just pointless!
I remember reading that a diffuser isn't so ideal for road cars that actually DO make good use of them, mainly because roads are not flat/smooth enough to offer a consistent delivery of force from them.
Wings are better for fast road cars that need down-force.
A diffuser will work best on a race car on a smoother track...
I'm not sure a flat floor is essential to the diffuser concept really. Ground effect and low aero need a fairly flat floor.
Hmm
Dave
Wings are better for fast road cars that need down-force.
A diffuser will work best on a race car on a smoother track...
I'm not sure a flat floor is essential to the diffuser concept really. Ground effect and low aero need a fairly flat floor.
Hmm
Dave
rhinochopig said:
Not actually true. They have been proven in the wind-tunnel. Mitsubishi engineers actually published a paper on the subject.
Yeh I read the Corsa VXR has been proven in the wind tunnel too with all its slits and diffusers.They're hardly going to say "we fitted them to your car but its utter b
ks and they do fk all" are they?tyranical said:
rhinochopig said:
Not actually true. They have been proven in the wind-tunnel. Mitsubishi engineers actually published a paper on the subject.
Yeh I read the Corsa VXR has been proven in the wind tunnel too with all its slits and diffusers.They're hardly going to say "we fitted them to your car but its utter b
ks and they do fk all" are they?
Don't forget when Mitsi was doing this research they had a desperately uncompetitive WRC car so they were looking for every advantage they could gain.
tyranical said:
fk me,
If thats the case im going to buy some and stick them on the roof of my car. The benefits will be immense and i'll definately be lapping the ring in the mid 7's.
Who said anything about immense benefits? In motorsport it's all about 10ths of a second at the top level - like Tesco says every little helps. At the time in WRC, to implement a design change on the WRC car it had to be homologated on the road car. k me,If thats the case im going to buy some and stick them on the roof of my car. The benefits will be immense and i'll definately be lapping the ring in the mid 7's.
It's why Evo's have an inter-cooler water spray feature - utterly useless on the road car, but a boon in a car that is being driven balls out all the time, which tends to lead to heat soak.
Mr Whippy said:
I remember reading that a diffuser isn't so ideal for road cars that actually DO make good use of them, mainly because roads are not flat/smooth enough to offer a consistent delivery of force from them.
I'm not convinced that's entirely true - to me a road surface being locally not flat enough, given the ride heights that a road car diffuser operates at, would have to be a road surface that was essentially undriveable at any speed above 20 mph, at which point any aerodynamic effect is somewhat less than rolling resistance. The reason why racing cars with aerodynamics are so stiffly sprung is to maintain a stable aerodynamic platform (e.g keeping the diffuser at a fixed height from the road surface) with the minor compromise of less consistent mechanical grip. Provided the road surface isn't too full of craters, it should have a reasonably consistent effect.IMO, the 'diffusers' you see on road cars (like the Renaultsport Clios) are mostly fashionable tinsle, which may have some positive effect, but the biggest effect by far is to appear sporty and race-car derived. Especially when you consider something like a Mk2.5 1.6 Focus Zetec S - all show, no go. Most road cars generate lift; the spoilers, diffusers, wings and vortex generators found on performance models can help mititgate some of the lift to give a bit more stability, and also perhaps offer better cross-wind yaw stability, e.g. by giving consistent separation characteristics. The diffuser may also help reduce drag to meet emissions targets. Very very few generate actual, meaningful downforce - I believe either the TVR Tuscan or Sagaris is one of the few production road cars that does; I suspect some of the super/hyper-cars do as well, but the aerodynamic design will be biased more towards high speed performance.
Edited by RenesisEvo on Monday 1st August 14:47
RenesisEvo said:
Mr Whippy said:
I remember reading that a diffuser isn't so ideal for road cars that actually DO make good use of them, mainly because roads are not flat/smooth enough to offer a consistent delivery of force from them.
I'm not convinced that's entirely true - to me a road surface being locally not flat enough, given the ride heights that a road car diffuser operates at, would have to be a road surface that was essentially undriveable at any speed above 20 mph, at which point any aerodynamic effect is somewhat less than rolling resistance. The reason why racing cars with aerodynamics are so stiffly sprung is to maintain a stable aerodynamic platform (e.g keeping the diffuser at a fixed height from the road surface) with the minor compromise of less consistent mechanical grip. Provided the road surface isn't too full of craters, it should have a reasonably consistent effect.IMO, the 'diffusers' you see on road cars (like the Renaultsport Clios) are mostly fashionable tinsle, which may have some positive effect, but the biggest effect by far is to appear sporty and race-car derived. Especially when you consider something like a Mk2.5 1.6 Focus Zetec S - all show, no go. Most road cars generate lift; the spoilers, diffusers, wings and vortex generators found on performance models can help mititgate some of the lift to give a bit more stability, and also perhaps offer better cross-wind yaw stability, e.g. by giving consistent separation characteristics. The diffuser may also help reduce drag to meet emissions targets. Very very few generate actual, meaningful downforce - I believe either the TVR Tuscan or Sagaris is one of the few production road cars that does; I suspect some of the super/hyper-cars do as well, but the aerodynamic design will be biased more towards high speed performance.
Edited by RenesisEvo on Monday 1st August 14:47
What I read was from a supercar manufacturer... I can't remember who now though. Someone who had used a big spoiler rather than a diffuser... might have been an article by the Ultima team?
Dave
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