[Mk2] [Turbo] rear diffusers

[refo]

Here is my take on a diffuser for a mr2, let me know what you think.

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looks good. its not long enough to create any downforce, or close enough to the ground, but it could reduce drag caused by the rear bumper so would aid the car's slip through the air a little.

[refo]

Harry,

your car looks great! i think it's an all round good looking set of bits.

for a little less drag you need some sort of sharp end to the boot lid. so instead of the air falling off the back and trying to cling on to the flat section (creating drag) it can just fall off the back and into a void.



the red lip would add a small amount of rear down force, the bigger the lip the more force. but the price you pay is higher drag.

the yellow lip would add no down force but would make sure that any surface air would slip off the back of the car without clinging to the rear lights etc. making for a lower amount of drag on the car.

just a thought.

not sure about your side skirts. they will help prevent the side flow falling under the car a little and will help to reduce air to the rear wheels too. but there is a lower vent that is putting air into the rear arch!! unless it’s ducted to the brakes then this little vent is not helping one bit.

i can’t see from your pics, does the front part of the side skirt that goes up round the front arch have a duct behind it to take air out of the front arch?

the rear spoiler looks like its got quite a bit of angle on it. you should be feeling the force from that in grip and drag. you could make it a little more slippery by cutting them bolts down to length (weight saving too ) and by profiling the leading and trailing edges of the uprights. could also fill in the holes with clear perspecs for less drag.
also if you reduce the angle of the wing and put bigger end plates on you could reduce drag without losing down force.

is your normal front number plate a jap style square one? a uk style wide one would create less drag into the rad and help keep the intake speeds up a bit more.

wow that was fun looking at your car, thanks!

Randomr2,
are you sure you didn't imagine a 10mph corner speed aid in grip? not saying that you didn't get that much faster but maybe you only pushed that hard because you convinced yourself you had more grip??
how meaningfully was the diffuser fixed to the car?

the way you had it installed it would have been trying to push air that ran over it up but i don't think it's long enough to have any venturi effect under it. it should give a bit less drag as the angle isn't harsh and it's aiming some air up into the drag space behind the car.
for effect i think the height is about right (by eye) but you need to mod the rest of the car to make the most of it. like you have said, your waiting for your new kit.

do watch out for the exhaust. the fibreglass wont melt but the resin will. and many of the resins used in composites don't go out once they start to burn. even under water!

the mr2's underside is flatter than most cars. not perfect by any means but its not too bad. it wouldn't take much to get a full single layer of flat undertray on the bottom with some rubber vertical side skirts fixed to the flange under the sills. this would help to keep the flow under the car much neater.

as said above, there would still need to be air drawn into the engine bay from the underside but that can be done with NACA ducts (as said above) or a scoop of some sort. It would only need to be low profile.

then you could have a gap the entire width of the engine bay but not very high under the boot and out over the diffuser. this is basically just an exit path for the hot air as it cant all get out of the standard engine cover.

the rear subframe really gets in the way of the underside aero.. but you have to work with what you've got.

good luck to both of you. glad to see some people trying some new things. even if it really is just trial and error.

p.s. sorry for long post people

[zebidi]

I was going to make one for this when i was doing my motorsport engineering course in uni but never got round to it.

I even calculated a full underside venturi tray for the car to a ride height of 25mm. (not a too streetable height really when you consider that the venturi design is dipped)

The thing with a diffuser where it looks the absolute dogs bollogs is that you want it to funtion or you are just adding more weight drag to the car.

You also want to make sure that the diffuser is getting fed the low pressure air accordingly too or else it will not take effect.