22 replies to this topic

[sonikk4]

 

Saved this photo from somewhere, I don't know who's car it is or anything about it though but shows an idea of what you want.
rear under tray.jpg

This is exactly what I'm looking to do. Nice one! Just got to figure out the best of attatchin it to the subframe

 

 

Rivnuts, anchor nuts, captive nuts, Zeus fasteners. Maybe some standoffs / brackets at the front to keep everything flat.

[Hegnirst]

erm why?! the mini is shaped like a brick and has more issues than the subframe. would stop valence rotting though

If you think that the subframe is the issue than I'm addressing then there's no point me trying to explain to you?!?!?!?!

[Hegnirst]

Mine is partly done because, as a rally car, it has a long battery box shield on one side and a long fuel pump shield on the other side to protect the two Facet fuel pumps. I can't say I have noticed any difference in performance though, but it keeps the mud off of the subframe.

It's more for motorway travel if anything and just something ide to try as the rear valance is like an umbrella in the wind. I'll probably never do it but why not ey!

[Hegnirst]

Saved this photo from somewhere, I don't know who's car it is or anything about it though but shows an idea of what you want.
rear under tray.jpg

This is exactly what I'm looking to do. Nice one! Just got to figure out the best of attatchin it to the subframe

Rivnuts, anchor nuts, captive nuts, Zeus fasteners. Maybe some standoffs / brackets at the front to keep everything flat.

The flatness is the key but equally don't want to slaughter my subframe in aid of trying this out. Welding some little brackets might be the best way maybe

[coopertaz]

 

erm why?! the mini is shaped like a brick and has more issues than the subframe. would stop valence rotting though

If you think that the subframe is the issue than I'm addressing then there's no point me trying to explain to you?!?!?!?!

 

as i was explaining to you that the issue with aero dynamics is about more than the floor, therefore i was not stating that the subframe is a main issue rather the whole mini shape. Does this explain my point enough for you!!

Edited by coopertaz, 31 December 2024 - 02:21 PM.

[Cooperman]

It must clean up the airflow under the car and thus reduce the drag somewhat. How much would need wind-tunnel testing to determine.

In addition, it would cut the mud getting onto the sub-frame and reduce corrosion of sub-frame and battery box.

To do it requires a centre-exit exhaust box.

I fitted my battery-box guard and fuel pump guard using M5 Riv-Nuts with dome-head bolts onto the sub-frame and 1/4" UNF dome head bolts at the forward edge with a quality sealant along the front edges. The material I use is 2 mm aluminium sheet and the front edges are chamfered slightly towards the front.

[stuart bowes]

I can't see it making an ounce of difference to be honest, in theory yes you'll reduce drag by some immeasurable amount but I'm sure that will only be noticeable at very high speeds and even then only if you're trying to save a couple of tenths off a lap time

It will give you some protection against elements which the rear frame does suffer from but like an engine undertray it will also be in the way whenever there is a job to do and all those fiddly little screws will be a pain when you're upside down holding it up in the air trying to get it back on

You could just as easily coat the underneath with lanoguard or something and save yourself a load of ball ache

I base this largely on the fact that you don't see it being done all the time after all these years so it's unlikely to be worth doing other than in special cases where the car is already improved at the front, where its being raced, and where tenths of a second are critical (and if its even allowed in the regs)

[unburntfuelinthemorning]

I've always fancied trying to smooth out the underside on mine but it's a little more tricky with the van's side exit exhaust.  I see it as a way to gain a touch more MPG for long journeys.  It's the obvious thing to improve aerodynamically as the subframe acts like a parachute otherwise.  Maybe the gain wouldn't be noticeable or measurable but it would be an enjoyable exercise for those of us who like messing around with such things.