36 replies to this topic

[Steppenwolf1980]

Hi guys,

 

maybe some remember my first project in 2008, where I designed and produced aluminium diffusers matching the VX's design. I also sold some here. What still annoyed me over all the years was that due to the wobbly aluminium, there was always a gap between the metal sheet and the rear clam. Also, the diffusers looked way too filigrane.

 

Since I am an industrial designer and now have connections to companies with 3D scanners and CNC mills, I developed a new diffuser during winter and spring. My main goal was to make a part that can be installed free of gaps and remains on the clam when you have to work in the engine bay from below. I took 3D scans of my Speedster and used the data for 3D modelling to achieve that perfect fit. I had a prototype milled and laminated it over by hand to test the fit and the new mountings on my car. As you can see on the last picture (the white-pink diffuser), it worked out great. Unfortunately, this prototype would have been way too expensive to be copied, since it is hand laminated due to its form. Also I found it then a bit too bulky and not OEM style looking. That's why I took all the proven data according shape and fit to redesign it as a one piece vacuum forming plastic part, which is of course a bit smaller and less aggressive, but way cheaper to make and looking like a factory part.

 

Since you can imagine that the form costs are quite high, please excuse that I can only show computer renderings and photoshop fakes at this point. Producing this diffuser only makes sense for at least 10 pieces, that's why I am currently looking if there are some people interestend in having one. Here are the pictures (click to enlarge):

 

 

The diffuser is made of 4-5mm ABS plastic, vacuum formed and then cut out with a 5-axis CNC mill. This should make the edges very precise (as long as this is necessary for a hand laminated rear clam with tolerance, of course). The plastic is black gloss, so no respray is necessary unless you want a different colour. Since it is replacing the original rear bottom cover, I also designed a new cover bridging the gap between the big cover under the engine and the diffuser. This cover is laser cut from 1,5mm aluminium, bent and powder coated. It will have ventilation cut outs in the final version to keep the engine bay cooler.

 

The set consists the diffuser, the new aluminium cover and the installation material and costs 490 Euro plus shipping (about 380 pounds). It might get even cheaper depending on how many are produced, since the costs vary on the amount. Shipping the parcel to the UK is about 20 pounds. So if you have questions or are interested in one of these, please feel free to post here or send me a message here or on Facebook (This topic can be found in the German Opel Speedster Club group).

 

Cheers from Austria, Marcus

 

P.S.: These are pictures from the first, bulky prototype and the installed new cover:

 

[JG]

Top one looks excellent.

 

I suppose I ought to try one

[JG]

The clam holes looks quite close to the edge, and not where the current holes are. does it require additional drilling? (that would be less good)

[techieboy]

Me likey. Much better than your initial prototype which was a bit too fussy (though not helped by being white).

 

No idea what the characteristics of ABS plastics are but will it stand up to the heat of the exhaust silencer without deforming?

[Steppenwolf1980]

@JG: Well, I would say that the diffuser needs additional drilling, since it weighs around 2 kg (4 pounds, I think?) and also must touch the upsloping surface of the clam. That's why I made those two little aluminium stripes you can see on the picture with the aluminium cover. The screw clips from the original cover can be installed there and you just lay these mounts under the aluminium heat shield from the exhaust box. Then you must drill three holes left and three right from the exhaust and put the screws through. It is kind of a sandwich construction. Maybe you could also glue the diffuser on the rear clam, if you prefer (and have a strong glue), but I prefered this method since it is really strong and you can't see the new holes anyway, since they are facing the road. We could think about reducing the new holes from 3 to 2 per side, since the moulds are not milled yet and I tested the white prototype on the German highway up to about 220 km/h without any incident. It held place really strong. Also I would take some black silicone and make a fine seam around the upper edge of the diffuser, closing every little gap or split it might have to the rear clam. My front splitter has that, too, makes it perfect.

 

@techieboy: I think so - ABS can deal to about 100°C and since there is the aluminium heat shield and the rear clam between the exhaust and the diffuser, there shouldn't be any issue with that. Those two layers are keeping the heat off the diffuser like a shield.

 

 

Edited by Steppenwolf1980, 23 May 2016 - 09:42 AM.

[techieboy]

@techieboy: I think so - ABS can deal to about 100°C and since there is the aluminium heat shield and the rear clam between the exhaust and the diffuser, there shouldn't be any issue with that. Those two layers are keeping the heat off the diffuser like a shield.

 

I know my TAT diffuser gets quite warm if the car has been given a beating on track or sat idling for a while. That may just be because it's metal and a good conductor of heat plus there's not much space between the mahoosive Tullet silencer, the insulation and the clam. Sounds like I have a mission for a couple of temperature indicator strips...... 

 

Would it not have been better to extend the two outer sides down to pick up the OEM attachment points for the wheelarch trims/spats/mud guards/whatever?

[Steppenwolf1980]

Yes, in fact I also still think about that. Frankly, it just need to have that triangular flap left and right with a hole in it to reinstall the plastic rivet. But this is a detail I would have to discuss with the guy from the plastic company who would produce them. Can be that there occur problems for the deep drawing (vacuum forming) with such a long geometry. If you would test the temperature on the outside of the clamshell below the silencer, that would be for sure a big help. To be honest, I don't dare to promise that the diffuser might work on any VX or Speedster, since there are some heavily modified monsters out there with custom exhaust systems whose temperature range I can't know. My own turbo is LEH setup, 280hp and Blue Flame 70mm exhaust system, and I never had issues with temperature down there.

[fezzasus]

Yes, in fact I also still think about that. Frankly, it just need to have that triangular flap left and right with a hole in it to reinstall the plastic rivet. But this is a detail I would have to discuss with the guy from the plastic company who would produce them. Can be that there occur problems for the deep drawing (vacuum forming) with such a long geometry. If you would test the temperature on the outside of the clamshell below the silencer, that would be for sure a big help. To be honest, I don't dare to promise that the diffuser might work on any VX or Speedster, since there are some heavily modified monsters out there with custom exhaust systems whose temperature range I can't know. My own turbo is LEH setup, 280hp and Blue Flame 70mm exhaust system, and I never had issues with temperature down there.

 

However if i'm interpreting this correctly, you have only ever tested your fibreglass (?) hand produced version. i would propose mounting a sheet of ABS where the diffuser would go to confirm that it can take the heat.

[Steppenwolf1980]

I can do that. I only said that I never encountered any warm aluminium diffuser anyway and surely not a hot one (100° would burn your hand). So I would just be confident with that By the way, if it was so hot there, the hand laminated diffuser would also have taken some damage or at least visible colour change.

Edited by Steppenwolf1980, 23 May 2016 - 01:51 PM.

[techieboy]

I'll stick some indicator strips in a few places on my diffuser and see what kind of temps it sees. Won't be particularly scientific as my TAT diffuser is full length and obviously see's much more of the exhaust system than your much shorter version as well as being metal. TAT did have to fit heat reflective insulation to his carbon diffuser version because the heat melted/deformed it. 

 

Probably won't get a chance to do anything until the weekend though.

[JG]

It'll be fine

 

[smiley]

TAT did have to fit heat reflective insulation to his carbon diffuser version because the heat melted/deformed it. 

 

 

My vx-performance CF one also did that, but it was within an inch of the cat. Near the round clam holes it just has some miscoloring due to heat.

Keep in mind that the clam itself is also close to those holes.

  

[techieboy]

It'll be fine

It's a valid concern, given I've seen 3D printed ABS gauge pods and other things melt inside car interiors. Granted, that's probably more of a reflection on the limitations of 3D printing and probably too thin construction but at £400 (pre-Brexit Sterling crash  ) I'd rather be more certain about what conditions it's likely to encounter before committing.

[JG]

tell you what i'll be a test case. (it will sit in the garage for a year and be fine )

[techieboy]

Yeah, my two days in the VX a year probably won't overly tax it either.

[Steppenwolf1980]

Yeah, that's a good point. I will also take some ABS and put it under the clam for a testride. But the dangerous spots are only directly under the silencer, where those 8 holes are. Since my diffuser is ending with the clam, it is quite away from the cat, where the new aluminium cover is. The heat shouldn't reach that far, but that's about to be tested anyway. My old diffuser was entirely made from 1,5mm aluminium, going from the main undertray (with the nacas) all the way back to the exhaust and only got a little melt at the cutout for the cat, since I forgot to put some distance there and the cat touched the edges of the hole. The rest was fine.

 

Frankly, I am in no hurry with the production of the diffuser, so there is enough time for some additional tests. The production time itself would be around 4-6 weeks, so still time to get it this season anyway.

[Shmern]

ooo like the look of the Black one.... Interested in this as well.....

 

[FLD]

Looks great

[Steppenwolf1980]

Due to the lack of interest I will put this project on hold... I'll have a prototype made some time in July or August and will post the result here. If everything turns out good, the diffusers can then be ordered on demand for a slightly higher price.

[techieboy]

 

I'm still interested in one, if it helps....