Humbug
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| posted on 10/12/07 at 01:01 PM |
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Rear diffuser qus
Just idly thinking about some stuff to keep me occupied over the winter.
It struck me that making a rear diffuser out of ali sheet wouldn't be too hard - could probably even make it out of a single piece if it was
folded right.
1. apart from looking go-faster, would it be likely to have any real effect on normal roads? on track?
2. I would probably have to make a cutout for the diff (escort live axle) - would that completely cock up any benefit? Would it be better to make a
cover for the diff instead of a hole?
3. would it be any use on its own if the tunnel and engine bay are still open at the bottom?
4. what would be the best way to fix it to the chassis? Rivets? Self-tappers?
Any other thoughts?
Cheers,
Simon
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Mr Whippy
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| posted on 10/12/07 at 01:06 PM |
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don't take it personally but your car is a brick, all there is at the back is turbulence
you'd be better smoothing the flow over the front.
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Mr Whippy
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| posted on 10/12/07 at 01:28 PM |
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quote:
Originally posted by Humbug
Just idly thinking about some stuff to keep me occupied over the winter.
now you've done that car, why not do another one, maybe design one from scratch?
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Humbug
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| posted on 10/12/07 at 01:48 PM |
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quote:
Originally posted by Mr Whippy
don't take it personally but your car is a brick, all there is at the back is turbulence
you'd be better smoothing the flow over the front.
Not taken personally but, given that a seven is a brick, would a rear diffuser help? Some air must be going underneath 
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Mr Whippy
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| posted on 10/12/07 at 02:45 PM |
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I doubt you'd see the effect, to sort it would really need a tapered tail or a smooth body shell. Really the 7 is about zipping around twisty
roads not motorways.
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procomp
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| posted on 10/12/07 at 03:05 PM |
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Hi it dose help prevent the air entering the rear area and acting as a parachute. But it dose give some small problems with increase in diff
temperatures so you need to allow some air venting to maintain a good working diff temp.
for short 10-20 lap races it is not such a problem but if doing longer testing / trackdays/race/ long road use ect it can become a problem. And
requires an air vent to the diff And an escape route for the hot air.
cheers Matt
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timex
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| posted on 10/12/07 at 03:29 PM |
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How about one of these?
http://www.fluke-motorsport.co.uk/product_info.php?cPath=1_59&products_id=182
Or if you dont have a F1 style budget to throw away then you could try these? Just down load there brochere.
http://www.plays-kool.co.uk/
Phill
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timex
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| posted on 10/12/07 at 03:37 PM |
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You may find this thread helpful
http://boardroom.wscc.co.uk/cgi-bin/ikonboard.cgi?act=ST;f=3;t=57712
Phill
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Humbug
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| posted on 10/12/07 at 05:15 PM |
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The WSCC thread was interesting... the Fluke option is definietly not Locost
So it sounds like:
- a diffuser panel on its own is not going to have much effect (other than visual and maybe to help keep cr@p off the under boot area)
- would need to have the tunnel pannelled over at least, and probably the engine bay
- may also need to have a front splitter
- even then the benefits are likely to be limited
Oh well, it was a nice diversion from having to work, for a few minutes
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Jon Ison
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| posted on 10/12/07 at 05:21 PM |
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I'm pondering this option to, mainly due to the "parachute" effect ?
Honest opinions, worth it ? Not worth it ?
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worX
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| posted on 10/12/07 at 05:43 PM |
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I think it's worth it on a couple of levels
Keeping crap out = worth it as long as it doesn't cost much!
Stopping Parachute effect = worth it, might gain a couple mile an hour?
Fitted with a full floor = Very worth it as long as you abide by certain rules...
quote:
Originally posted by Jon Ison
I'm pondering this option to, mainly due to the "parachute" effect ?
Honest opinions, worth it ? Not worth it ?
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procomp
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| posted on 10/12/07 at 06:04 PM |
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Hi it is definitely worth it but as said only if you do the whole car. It comes as std on our LA golds and on circuit it definitely makes a
difference. But we are doing 132 mph on some straights.
Butt on a road car possibly not worth the effort unless your feeling keen .
Cheers Matt
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RK
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| posted on 11/12/07 at 01:41 AM |
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I tried to make a couple, one for each side, and gave up. The fibreglass warped the foam cored paper I used. I don't think I want to get those
kind of headaches anymore, so I may try again using plastic or alu.
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timex
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| posted on 11/12/07 at 09:38 AM |
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My concern about fitting a front spliter, panneling under the engine bay/tunnle and adding a rear diffuser is that will the performance gain be
greater than the the performance lost by adding all that extra weight?
Also if fitting a diffuser without panneling under the engine and the tunnle they aint much point.
By panneling unnder the engine wont you just get the parachute effect in the engine bay from the air entering through the nose cone and not having
anywere to ascape?
Then you will start needing a ducted nose cone and side pannles that flare out to allow air to ascape!!
I personaly dont think that it is worth it if you are mostly using the car for the road with the odd trackday but unless it is an all out
trackday/race machine and the car is constantly being driven hard on its limets then they aint much point! 
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C10CoryM
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| posted on 12/12/07 at 01:05 AM |
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quote:
Originally posted by timex
Then you will start needing a ducted nose cone and side pannles that flare out to allow air to ascape!!
Well you should have that anyhow Properly ducted radiator exhaust is tops on my list. Once I get my car built I intend to play around with a
manometer and see. I have a sneaking suspicion that on a book locost you get a massive high pressure build up in the rear panel/boot area which trys
to get into the empty spot behind the car. Just a guess, but Id bet venting the rear panel could see a large decrease in drag.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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timex
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| posted on 12/12/07 at 12:18 PM |
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Or just dont even fit a rear panel
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