Fiddling about with my kit car- some ideas.

[aerohead]

Yep,the diffuser is like a two-dimensional diverging nozzle,where the fluid (air) is decelerated,building back static pressure as it travels,such that it imparts this higher pressure to the wake,raising its base pressure,and lowering the pressure drag (largest component of a vehicles drag).

[jondoeclsm]

Thank you - good answer!
I am going to try and make a fastback for it. rear diffuser is certainly on the list as well.

[jondoeclsm]

there are 3 bars going across the underside of the car, so I am shortly to do a simple flat bottom mod.

I have a rear wing on now and have a part finished front splitter. I still need to modify the height of the air dam as there is a gap between the top of the air dam and the bottom of the bumper.

I am yet to do a test run without the new mods on (I have changed wheel size, so this throws out my previous drag recordings) - I must do a few more runs keeping the mods on then take them off and see the difference, the car feels better with the smaller wheels and the mods. My thoughts are that the rear wing is helping organise the rear air flow (when I say organise, I mean in the same way as end plates on a wing 'organise' air flow). Only the results will tell me if these things work.. but just a wordy update to let you know I am still here.

[mcrews]

am I missing the pictures!!!!!?????

[aerohead]

Originally Posted by jondoeclsm

there are 3 bars going across the underside of the car, so I am shortly to do a simple flat bottom mod.

I have a rear wing on now and have a part finished front splitter. I still need to modify the height of the air dam as there is a gap between the top of the air dam and the bottom of the bumper.

I am yet to do a test run without the new mods on (I have changed wheel size, so this throws out my previous drag recordings) - I must do a few more runs keeping the mods on then take them off and see the difference, the car feels better with the smaller wheels and the mods. My thoughts are that the rear wing is helping organise the rear air flow (when I say organise, I mean in the same way as end plates on a wing 'organise' air flow). Only the results will tell me if these things work.. but just a wordy update to let you know I am still here.

The airdam will be most effective if there is zero gap between it and the bumper bottom.

[jondoeclsm]

Sorry not got pictures up yet.

[jondoeclsm]

Trying a side view of the actual car..

[jondoeclsm]

Ok, so after several runs on the new small wheels monitoring full accelleration from 4.5k revs to 6k revs with and without the rear wing and the front splitter on, the difference in this area is that:
it does this in 3rd in around 4.5 seconds and with the wing and front splitter it is on average 1/5th second quicker.

So if I have gained some downforce then great, it comes with a marginal difference in drag.

[jondoeclsm]

I was removing the old shocks on the rear today and had to make a small hole in the rear of the wheel arch in the boot space.. this got me thinking, would the rear wheels benefit from venting them inside the boot space and letting that air out of the vertical rear which is the boot?

My thoughts are that it may be beneficial as the very low pressure at the rear could be 'fed' from the wheel arches.

Also a lot of race cars now use vents rear of the front wheels, this would be a vent at the rear of the rear wheels.

[jondoeclsm]

Oh yes, and I managed to bridge the gap between the air dam and bumper by using the hard plastic strip used for worktop trim, 40mm high, attached by the non removable 'Tiger Seal' which I managed to use without getting on my fingers for the first time today.