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Old 02-28-2015, 04:41 PM   #9 (permalink)
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Originally Posted by jondoeclsm View Post
Yes, glad you mentioned the fastback, I almost have a solution planned for that (should, if it works be useful for other fastbacks).

There is one of these cars up for sale, with one of the only 3 hardtops I know of in existance:
onyx firecat with hard top | eBay

Look at me posting links!

My fastback would stretch back to the end of the bootlid. Hopefully with a sharper tip/ flat horizontal plane as I have read this is better.

Ok, so regarding front air flow, I need to let go of a lot of air out of the top of the bonnet. I do need plenty of flow.

The rear lower section is going to be the most awkward to sort out but pretty vital. Is there any data (I will google but as yet have not) for adding a rear diffuser and drag reduction achieved? My car is front heavy and light, the addition of a little weight, especially at the rear is no issue at all.

It will gain a front air dam, splitter and rear wing for track handling. The rear beam has been stiffened up and polybushed to give a lot more anti-roll, so the wing is needed to stick it back down at the rear.
*For the bonnet you might check out modern cars like Corvette/Camaro/Mustang etc. to see how they handled under bonnet airflow.All these designs were targeted foe high-speed stability.
*For the diffuser to work you need a smooth belly pan which has shown a drag reduction of 0.045 on an Audi 100 III.With a diffuser they got - 0.07.
*Also,check out the BMW Z1 with aerofoil-shaped muffler and venting slots into the rear bulkhead.This setup was mostly for high-speed stability at the track.Here's a link
*For the boot,the fastback would be what Kamm would recommend.He did this for one of Briggs Cunningham's LeMans race cars in the 1950s.
*If you need more rear downforce,you could incorporate a spoiler,or add one.A smaller wing,mounted up into the clean air would provide more downforce with less drag.And it could be directly over the rear axle so as not to aggravate front lift.
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Last edited by aerohead; 02-28-2015 at 04:43 PM.. Reason: add link
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