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GC8 Track Aero - Double Deck Rear Diffuser

Old 10 October 2017, 12:57 PM
  #31  
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Originally Posted by MY94BlueWRX View Post
Sounds like a good idea, what modelling software do you use Sunny?
Generally use Solidworks for modelling from scratch, going to start experimenting with lightwave to draw on top of existing scanned objects.

Figured I can only see how they turn out, if all else fails i'll put the originals back on haha.
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Old 10 October 2017, 07:03 PM
  #32  
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If you can export your 3D Scan in IGES, STEP or X_T format then you should be able to use Solidworks to surface them further?
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Old 11 October 2017, 04:07 PM
  #33  
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Originally Posted by MY94BlueWRX View Post
We had a very busy day yesterday... set off at 2:30am for sunny Plymouth, 5 hours later we were sat outside Enginetuner waiting for Martyn.

As soon as he arrived he was straight onto it, and a few hours later we weíre all mapped and setup... the results speak for themselves and the new Wideband Alcatek was a pleasure to map (Martynís words). The Anti Lag was also set up, more for a nice Ďtoyí feature than an actual positive pressure system, but it sounds so nice on overrun! 😜

Then a long drive back last night made for a very long day, but the big smiles on our faces more than made up for it... enjoy!



https://youtu.be/aMgGMWwKhq4

https://youtu.be/it1cxBxfciw
No kidding, this car is one of the very best we've seen period. Not only does it look great, but it works in the best way possible. We're seriously chuffed to have built the motor for such a thoroughly well prepped car.
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Old 18 October 2017, 07:06 PM
  #34  
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Originally Posted by MY94BlueWRX View Post
If you can export your 3D Scan in IGES, STEP or X_T format then you should be able to use Solidworks to surface them further?
I'll certainly give this a go, i'm more competent with Solidworks too.

I use the word competent loosely

I'll get some pics up when I get time to sort it all out.
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Old 18 October 2017, 07:24 PM
  #35  
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Originally Posted by Alan Jeffery View Post
No kidding, this car is one of the very best we've seen period. Not only does it look great, but it works in the best way possible. We're seriously chuffed to have built the motor for such a thoroughly well prepped car.
Thanks Alan,

We’ve spent lots of time getting our car just right, and we’re so pleased with the results, and the complements it receives.

It’s been a complete pleasure to deal with you guys from the very beginning, and would recommend anyone to use your services.

Cheers,
Kim

Last edited by MY94BlueWRX; 08 November 2017 at 09:11 PM.
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Old 07 November 2017, 10:18 PM
  #36  
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Default Splitting hairs... Maybe?




After a little break, we got to work on a few parts for the front end... namely some front wheel deflectors and the beginnings of the splitter end plates.

The deflectors were fabricated from some Aluminium after a little bit of cardboard engineering, then wrapped in carbon vinyl. Ideally Iíd of liked them out of actual carbon fibre, but composites are one skill Iím yet to learn!
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Old 07 November 2017, 10:27 PM
  #37  
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These are the early stages of the splitter end plates, with the idea being that the vertical plate will stop air from spilling over the edge of the front splitter, creating a high pressure region on top of the splitter.

Whilst the longitudinal channel and quarter cone will allow a vortice to form and expand, that will aid in creating a low pressure region along the front wheel to help evacuate turbulent height pressure air from within the wheel well.

Thats the theory anyway?! 🤔

Last edited by MY94BlueWRX; 07 November 2017 at 10:30 PM.
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Old 08 November 2017, 10:16 PM
  #38  
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Nice work did you get my pm a couple of months ago mate
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Old 27 December 2017, 08:37 PM
  #39  
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Some good ideas in this thread

First vid has been removed
Airflow in second vid looks very turbulent, is there a fan running up front?
from the pictures, it looks like most of the rear diffuser is flat? Is that the case or are the upper surfaces curved? If they are curved, are the curves constant?

By splitting the rear into 2 sections, you're putting a barrier in the way and stopping it working as effectively as it could
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Old 27 December 2017, 08:48 PM
  #40  
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Originally Posted by sunny1989 View Post
I'll certainly give this a go, i'm more competent with Solidworks too.

I use the word competent loosely

I'll get some pics up when I get time to sort it all out.
I'm a CATIA guy, spent 12yrs on it full time at work. If you're struggling with anything then give me a shout.
I'm interested in your scanner, as that is the first source of data, and a lot of them produce very poor quality point data which can be a ballache to produce nice surfaces from. I did the AW189 outer surfaces a few years ago
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Old 27 December 2017, 09:25 PM
  #41  
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Hi Tom,

Not sure whatís happened to the first video... bloody YouTube!! Iíll try and fix it.

The airflow seems a little turbulent as weíre moving a leaf blower from side to side, unfortunately these are the limitations of our resources, but itís much improved over the first video.

The idea behind splitting the diffuser into two decks is because if we ran it as a single opening, we would end up with separation as the ceiling of the upper deck is at too steep of an angle. We have improved this angle be adding Venturi tunnels into the flat floor leading up to the diffuser throat, which makes the transition smoother.

However, we have only been able to add the tunnels either side of the rear diff, so the centre of the floor (in between the Venturi tunnels) leads directly to the lower deck.

This setup hopefully makes use of all available airflow, and directs it to where it can be used most effectively. We could just run the lower deck and join its entire width to the processing floor, but the tunnels would be useless then as they start too early. Conversely we could ditch the lower deck, but weíd struggle to deal with the rear diff being in the way, unless I ran the tunnels all the way to the back of the diffuser.

More than one way to skin a cat I guess?
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Old 01 January 2018, 01:14 AM
  #42  
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Hi BlueWRX,
I've been a bit absent from the forum for a bit so only just spotted this this thread... I must tip my cap to the exemplary level of work on your car. I wish my car was so well presented!

I also have a GC8 track car (1999 Turbo 2000) which I'm designing a flat floor & diffuser set up for. So this thread has lit a fire in me!
I'm wondering about how you've mounted the main floor panel; is your new floor spaced down from the original chassis rails or tight against them? Is it raked from front to back or just level up to the diffuser?

I've found a very useful youtube channel from an Aussie engineer that gives some excellent insight into aerodynamic design, I think you'd find it very interesting if you haven't seen it already...
https://www.youtube.com/user/Kyleengineers


PS I'm a design engineer by trade so work in solidworks all day long, let me know if I can be of any help, and if you feel like sharing any files I'd be forever in your debt!
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Old 01 January 2018, 02:19 PM
  #43  
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Hi Jonny,

Thanks for the message, itís always nice when someone connects with what youíre trying to achieve.

The main floor is actually spaced from the chassis by the exact amount to line up with the side skirts, and the proceeding front splitter/undertray... The floor is held up with titanium fasteners that screw into billet aluminium bosses that have been machined to specific lengths, such that each one is different (due to their respective mounting points on the chassis etc) but provides a level mounting point/surface for the floor to attach to. I can send you some pictures of exactly where Iíve mounted these to if you like?

Ironically iím a design engineer too, and work in both Inventor and Solidworks... so it must be in the blood! 😉

Iím sure we can share some thoughts/ideas and files on various things, so ask away and iíll see what Iíve got.

Like you, iíve seen every one of Kyleís videos and have found them very useful, another chap to look up is Andrew Brilliant, as his aero work is stuff of legends in the Motorsport arena! 👍

Regards and happy new year!
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Old 01 January 2018, 03:07 PM
  #44  
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P.S. The car/floor is raked from front to back by 20-25mm, but this is dealt with via the suspension ride height rather than the floor itself. Was too complicated to get the floor to be at a different angle to the straight side skirts without introducing further step transitions...
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Old 03 January 2018, 02:38 PM
  #45  
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How funny you're also a designer. Makes sense I suppose.
Thanks for the tip on Andrew Brilliant, I’ll be mining the web for his knowledge.

I've had another look back through your photos and spotted the spacer studs you mentioned, I think I'll definitely be doing something along those lines.

Originally I was thinking of dropping the side skirts lower than the floor to create more of a tunnel. But I've come to the realisation that unless the skirts actually slide on the floor its a waste of time & effort. So flat floor at skirt level it is!

Our car (its a syndicate between a mate and myself) if much more of a low budget affair than yours, so rather than aerolam I'm using 4mm Dibond panels that I got for free. I just hope its rigid enough

I do wonder if having the car 20mm lower at the front doesn’t upset the already forward bias weight distribution? Or have your done anything to offset that?

On a non aero note, I've surprised that your car still have the original single coil & HT leads.
We had misfire problems at 340bhp with the stock setup, but it was totally cured with some surefire coils & a conversion loom.

PS, our car is road legal too, do you know the legalities of cutting the bumpers and having a diffuser hanging out the back?!
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Old 03 January 2018, 05:42 PM
  #46  
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The side skirts being lower is an advantage, as they will aid in sealing off the underfloor from high pressure air from outside... however jacking up the car is also an advantage, so it's all a compromise. Air jacks are on our list but it's a £2k expense that isn't warranted at the minute.

If you are going to use the dibond, just make sure you brace it on the upper surface to improve the deflection, with aluminium L section or similar. You may have to create more mounting points than us, as the Aerolam is very stiff so 8 mounting points is sufficient, depends on you bracing strategy I guess?

The small amount of rake in the suspension makes no difference to the handling in our experience, as the COG change with 1-2deg of rake is very minimal.

The misfire issue may of been down to your ecu, as we are using the latest Alcatek ecu and Martyn has had no issues with the ignition when mapping, even at 422bhp?

Regarding the road legalities, I don't believe the addition of a diffuser would cause any issues, providing the car still passes an MOT I believe you'll be fine.
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Old 03 January 2018, 06:52 PM
  #47  
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A few pics from our track day at Oulton Park in Nov 2017... enjoy!










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Old 03 January 2018, 07:48 PM
  #48  
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that looks evil!

can you draw a diagram to show how the splitter/tunnels work?

A thread full of design engineers! we are a breed of our own!
just finished designing my front uprights, 2kg saving each, and geometry corrected for running 50-75mm lower, rear's next.....
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Old 03 January 2018, 08:00 PM
  #49  
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Thanks Tom,

I'll draw something up at work tomorrow, side profile sketch to explain things.

Are you machining the uprights from billet aluminium? Would be interested to see what you've come up with there, what is your bearing choice?

Regards,
Kim
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Old 03 January 2018, 08:48 PM
  #50  
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Originally Posted by tom-r33 View Post
that looks evil!

can you draw a diagram to show how the splitter/tunnels work?

A thread full of design engineers! we are a breed of our own!
just finished designing my front uprights, 2kg saving each, and geometry corrected for running 50-75mm lower, rear's next.....
Come on Tom, we need pictures or screenshots at least. Very intriguing!
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Old 04 January 2018, 09:48 AM
  #51  
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That looks great have to say, Top work !
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Old 04 January 2018, 11:21 AM
  #52  
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WHAT A MACHINE!!! Great work
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Old 04 January 2018, 12:34 PM
  #53  
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What kind of lap times were you doing at oulton and on what tyres?
Thanks
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Old 04 January 2018, 09:23 PM
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Originally Posted by Jonny Cut Corners View Post
Come on Tom, we need pictures or screenshots at least. Very intriguing!
i'll start a thread
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Old 04 January 2018, 10:30 PM
  #55  
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I’m loving this thread. Great to see folk with good technical knowledge sharing. I would love to have the ability to do what you guys have done.
I would say post on here Tom to keep it all in one place but also another thread would be welcomed
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Old 04 February 2018, 08:59 AM
  #56  
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Apologies for the delay in answering, the lap times we have got to are 1m 54s around the full international circuit at Oulton.

We are aiming for mid 1m 40s so still a fair way to go yet, but we started at 2m 10s so have made good progress... all with sub 400bhp too!

That was on Yokohama slicks, we have now moved to a wider Avon slick but the construction of the tyre is different so setup has to change by a surprising amount.

Last edited by MY94BlueWRX; 04 February 2018 at 09:03 AM.
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Old 04 February 2018, 06:38 PM
  #57  
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So I've been thinking... With an FMIC and a flat floor, do you think there's any benefit to fitting a scoopless bonnet from a non turbo model?
The stock scoop location is in a high pressure area, so it doesnt work very well as a vent.
Somebody has done some half scientific research on engine bay temps with scoops vs reverse vents and the vent saw a rise in engine bay air temps in almost all areas.

But with a flat floor, the air entering the scoop wouldnt really have anywhere to go. Making a dam effect. Surely not great?

I suppose the ideal solution is to use the OEM scoop as your air intake like the Nur RA car.
But I'm not sure I can face trying to fabricate that!

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Old 04 February 2018, 07:39 PM
  #58  
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With a sealed off flat floor and a front mount, you are correct in that a scoop is no longer required. The question is whether you go with a vent or not... this is all down to pressure differentials!

We carried out some rudimental testing with a magnahelic guage, to establish where we were at with under bonnet pressures and above bonnet pressures.

Because we have a few ram air type inlets into the engine bay, and itís more or less sealed off with the undertray/floor, we are creating high enough under bonnet pressures to allow the reverse scoop vent to work. The above bonnet pressure in this region is lower than the under bonnet pressure, so we have a negative pressure differential... hence higher pressure air will flow out of the engine bay to the lower pressure region above the bonnet.

My head hurts now... more red wine is needed!! Lol
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Old 04 February 2018, 09:24 PM
  #59  
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Flat floors just change everything don't they!
Thanks for sharing your findings, very interesting.

We've currently got our bonnet raked up with 10mm spacers under the hinges. Do you think that would allow enough air out up the windscreen?
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Old 04 February 2018, 09:43 PM
  #60  
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We were running with them until I did the testing, and they actually were causing air to enter the engine bay... not the other way around!

This is because the area right by the bottom of the windscreen is a high pressure region, much higher than under the bonnet... thereís a reason why 99% of manufacturers put the HVAC inlets in this location.

Now if you were to seal off the windscreen scuttle panel to bonnet gap, and just leave the sides open... then youíd be better off, but a reverse scoop or a couple of well placed vents are much more effective!

Last edited by MY94BlueWRX; 04 February 2018 at 09:44 PM. Reason: Typo
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