Rear diffuser?

[Rob Bell]

Just come across a very interesting thread on the VX220 forum - http://www.vx220.org.uk/forums/index.ph ... 65408&st=0

Before diffuser, the airflow at the back of a VX220 is modelled thus:


And after fitting a 12 degree diffuser, things are smoothed out a bit:


Lots more detail in the above mentioned thread. Would be interesting to see whether this might work on an MGF/TF - packaging the rear exhaust box is the trickiest bit!

[colintf]

interesting thoughts Rob

[Kasper]

The MGF has this aeroplane like "wing" at the back, I played with the thoughts of using it to have a low mounted rear spoiler long before the time of diffuser. Never dared to change however. I guess there are too many obstructions at the underside of the car

[David Clelland]

I hate to tell you Rob, but if can think of anything to do on an MGF Mr Hiorns has probably already tried it -

[adrianclifford]

David, I remember seeing Goldenwheels in that guise, I would love to have seen the air flow diagram on that. My eldest boy, Michael, has a 2 litre Clio 197 with a rear diffuser fitted as standard it's absolutely awesome by the way (would have loved one of those when I was 21 !), working with Renault daily I spoke to the engineers recently and they took a 197 out on the track without the rear wing and diffuser, it was all over the place they said. The one fitted to the Clio is similar to the second picture. Definitely an interesting mod if it became available I think. May be a bit concerning about heat build up around the silencer and exhaust though and it may hang down too low at the back for daily road use ?

[Rob Bell]

Gerry had certainly 'been there, done that' with many things, but I think with the rear diffuser, his won't have worked too well with the back box interrupting the air-stream. In fact the position and size of the silencer is a real problem, but it may be possible to package something, but I suspect that some rear bumper surgery is going to be necessary... not a problem on a car like the Shed - but for a road car, well, depends on how extreme you'd want to be.

Gerry's rear spoiler however was certainly in the best position to be actually functional

[J13UTM]

Im an aerospace design studen right now - for my next project im using my car....

My intention is to reproduce the cars outer skin - to my best accuracy and then run a simulated airflow over the car, examing boundary layers and stagnation points on the car. The plan is to be able to understand exactly where the MGF could do with a diffuser,and the optimum size for air scoops. Watch this space guys

[Rob Bell]

I'm looking forward to this!!!

[colintf]

Im an aerospace design studen right now - for my next project im using my car....

My intention is to reproduce the cars outer skin - to my best accuracy and then run a simulated airflow over the car, examing boundary layers and stagnation points on the car. The plan is to be able to understand exactly where the MGF could do with a diffuser,and the optimum size for air scoops. Watch this space guys

hey nice one. well done!

[J13UTM]

Yes, the plan is for me to create a CAD model of the outer shell, to the best of my abillity - with simple wheels and undercarriage. Then run a CFD program etc to look at the airflow. Suprisingly all i need to do is get the CAD model right and the rest is easy.

[Rob Bell]

3D models may already exist - there are a few models here: http://www.ppcmag.co.uk/forum/viewtopic.php?f=37&t=7538

Basic MGF and TF dimensions are listed - but not sure whether the vector diagrams are available?

[J13UTM]

TBH solidworks - my software - is pretty easy to use so i may just start from scratch -ive got over a year to start this project anyways so it will be the modelling phase that takes a while.

I saw a few blue prints on that sie which i may be able to use so I have logged onto that one.

[J13UTM]

but not sure whether the vector diagrams are available?

thats going to be the hard part - and modelling the fabric roof

[Rob Bell]

Can you model the roof down as well? MGF Cup cars race without a roof fitted... which is why rear spoilers are often pretty pointless on these cars. But a diffuser on the other hand...

[J13UTM]

That could be difficult to do due to how the canopy folds - at least would be hard for my skills. Ill try. The priority for me will be getting the frame of the car and then model each panel

[colintf]

Can you model the roof down as well? MGF Cup cars race without a roof fitted... which is why rear spoilers are often pretty pointless on these cars. But a diffuser on the other hand...

several of the Trophy TF's have hardtops on (Dreadnought's Paul Luti, Luffield's David Woods spring to mind)

[Rob Bell]

Much better to run with the hard tops - but they're hard to come by or are very expensive (B&G have some I believe). I'll just have to bide my time and wait to see whether a sheddy second hand example ever turns up...

But back to the roof down- I think that this would be a useful exercise - as let's face it, most of us drive with the roof down much of the time - and that ruins air flow over the rear of the car. Would be nice to see how engine bay cooling might be improved with the roof stowed?

But that said - getting the car modelled at all is the first vital step - so over to you. I'll break out the pom poms and start cheering you on!

[J13UTM]

Well to bring everyone up to date with the car modelling item, i have put it in a bikini but i dont think we will win any competitions just yet.


No seriously i will try and model it with the roof down - for simplicity i may just not add the hood on for that model - just remove it from the assembly. In terms of the car im going to try and model each panel and then create an assembly of them and mate them together - it wont be as exact as I would like but it will be a great excercise - mainly for the rear diffuser and air intakes.

Im hoping to get started next week at some point if work allows. Should probably start a new thread for the project once the ball gets rolling

[Rob Bell]

Yes, that's all we need really - just model the windscreen and perhaps the side windows for the roof down model

Very exciting project - really looking to seeing how this comes together

[Mark L]

Pointless and ugly!....

Unless you do lots of very high speed track work then these diffusers are little more than cosmetic.

Interestingly, I owned a VX220 and lots of owners fitted aftermarket diffusers, the most popular was a brand called 'TAT' which pretty much sums it up for me!.

Would you really want to nail one of these things to the rear of your car?..