Guinness
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| posted on 10/2/08 at 06:44 PM |
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Fitting Rear Diffuser
Finally managed to get some time in the garage today. I tried fitting the diffuser I got off Graham / Scotlad to the back of my MK.
The front edge seems pretty easy, a few strips of aluminium angle and a few dzus should see it right. But the sides and back are more tricky. Any
advice gratefully received.
Obviously I'm going to have to find something slightly more durable than masking tape to hold it on:
.jpg)
It seems to stick out the back quite a bit. Should I trim it back or leave it long?
.jpg)
If I leave it long, then I'll have to turn the no plate light round and relocate the plate:
.jpg)
Close up of the excess length:
.jpg)
Cheers
Mike
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welderman
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| posted on 10/2/08 at 06:53 PM |
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It doesn't need to stick out that far.
It also doesn't need to stick out at all over the whole of the width (if you didn't want it too!).
It also depends on whether you are going to put any "channelling" under the main body of your car to duct air toward the centre of the
diffuser.
That also depends ( ) on whether you have a full flat floor (in your engine bay too).
Cheers,
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Guinness
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| posted on 10/2/08 at 07:25 PM |
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Cool
I think I'll trim it back then.
Yes the car is getting an undertray under the engine bay, along with ally angle the full length of the chassis.
Cheers
Mike
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caber
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| posted on 10/2/08 at 09:57 PM |
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Deffo reccomend chaging masking tape to gaffer tape, make ure you get good stuff with a fine cloth weave
Caber
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rick q
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| posted on 10/2/08 at 11:19 PM |
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I didn't want to drill holes to mount mine so fitted al angle down the side of the car using large "P" clips (on the frame member
below the rear axle) which sorted the sides. For the middle I was able to pick up some existing holes.
In every case, I just used nutserts - though I wish now I'd used Dzus fasteners
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Kaspa
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| posted on 10/2/08 at 11:33 PM |
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A very profesional job i must say Mr Jones, looks really good, now about my royalty cheque 
Kaspa
[Edited on 10/2/08 by Kaspa]
understeer= when you hit the wall front first
oversteer=when you hit the wall back first
HP= how fast you hit the wall
Torque= how far the wall moves when you hit it
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britishtrident
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| posted on 11/2/08 at 08:23 AM |
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A diffuser angle of more than 10 degrees won't produce downforce only more induced drag.
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Phil.J
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| posted on 11/2/08 at 09:00 AM |
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Britishtrident is right, the angle of that is much to steep and sudden to work. You'll get mainly drag and turbulance.
I always work on a maximum of 7 1/2 degrees rising to a maximum of 10 degrees from horizontal over a distance of 2-3 ft. length. But these cars have
the aerodynamics of a brick anyway so who knows!
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rick q
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| posted on 12/2/08 at 12:41 AM |
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The upwards angle on mine happened to be 15 degrees (same as the frame). On the weekend I blew the rear seal on the gearbox which covered underneath
the car (full width) with oil. It was interesting to see that the oil flowed in straight lines from the rear of the gearbox all the way to the tips
of the diffuser [before tumbling out all over the back of the car!!]
The Fraser also has a flat tray under the engine as well which no doubt helped keep it all flowing smoothly.
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Grintch
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| posted on 22/2/08 at 08:11 PM |
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quote:
Originally posted by Phil.J
Britishtrident is right, the angle of that is much to steep and sudden to work. You'll get mainly drag and turbulance.
I always work on a maximum of 7 1/2 degrees rising to a maximum of 10 degrees from horizontal over a distance of 2-3 ft. length. But these cars have
the aerodynamics of a brick anyway so who knows!
While 8 - 12 degres seems to be when airflow separates on a flat plate, in ground effect with the wake (or even better a wing) to help activate it 15
- 20 degress is not uncommon. When in doubt, do an oil or yarn test to look for separation.
Looks very nice Rick.
Guinness, personally I would cut yours back a bit. But probably not all the way flush with the rear panel.
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