2G Rear Diffuser Design

[gofer]

The mock-up photos look like you've got something there, I'm curious to see an underside shot of it once you get everything installed.

Andrews kit uses a Lotus Elise diffuser, you'd have to talk to John about how it bolts up but I know that it wasn't part of the aero kit.

 

[Atuca]

The way they mounted the lotus one wasn't adjustable; something that may or may not be beneficial to have. Andrew has already designed his own functional rear diffuser, though I do not know if he is using it or not yet. It is much more functional then the lotus one. You can see the lotus one is actually lower then the bottom of the car, and has a gurney flap on the trailing edge, which indicates to me it is being used almost as a low air foil. Functional diffusers are very specific to the car they are installed on; there's no need for some of the bumps and shapes to the lotus diffuser on a DSM, though I am sure they made sense on the Lotus body. Andrew used this because it filled the void in the back of the car.

I started this project before I got the aero kit, so the whole race version may or may not come to be; I may just use Andrew's designed one for our body so I don't have to do all this work again for a potentially "one of" diffuser, and still not have any CFD data to back up the design. It's really still up in the air, I know a few people here have expressed interest without the limitation of a stock rear end (sawzal ppl, im looking at you) so we'll see.

Let's get more input on the diffuser at hand though

 

[snowborder714]

He was still using the Lotus piece for WTAC.

 

[Apache]

Sorry to go off topic on this, but does anyone know what that cooler is that Andrew has mounted right above his Lotus diffuser?

As for on topic conversation, it would be interesting to see how much more of that area around the subframe spacer could be filled up. I know you said that the swaybar has to go through there, but I wonder how much of that gap could be closed up and allow "just enough" room for the swaybar. Just throwing out ideas.

 

[snowborder714]

Fuel cooler.

 

[mitsumikey]

I will try and find time to ms paint a pic of yours to show my ideas. Although I do understand you would be disregarding them at this stage for the most part. And I don't blame that
Could use a few natural pics of it when your further along and at a few angles

 

[Atuca]

Strakes are done! That's a whole lotta strakes! Now need to figure out the best way to mount them to the panel.

I was thinking, and over the course of months, I forgot why I kept the diffuser panel flat at the forward side: I don't know how it will mount to the fwd sub frame! The fwd sub frame may have a different shape than the awd, and make it impossible to copy the contour of a shaped diffuser. I think for that reason I will keep the inch or two over hang so that I am future proofed.

I got the subframe panel mounted. Uh.. going to be honest and say.. you can tell a machine didn't percisely place these holes. Some of them were a bit elongated to fit correctly, and I documented the exact(ish) locations to drill next time. I'll probably send the second tester my revised drill locations and have him verify if they were right on the dot. It was really hard trying to measure under the car and than translate that to a perfectly drilled hole. Anways, sanded the holes with a dremel and now I'll get the diffuser panel molded. I'll prep and paint this sub frame panel for you Angel, right after I figure out how to fit my exhaust through the middle of the diffuser and sub frame panels (speaking of which.. we gotta figure out if your exhaust routes the same way as mine, and how close we want to cut the diffuser to my exact exhaust, increasing the chances you'll have to cut more when you get it if your exhaust has different bends/angles.

Anywas, I got the strakes on the diffuser panel and then got a call from my best friend, he is finally buying his first DSM: 98 GSX That hosed me the rest of the day, but I got a few pictures of today's progress!

 

[91-GS]

Strakes are done! That's a whole lotta strakes! Now need to figure out the best way to mount them to the panel.

Pop rivets

 

[greengoblin]

Pop rivets

NO.

Either Dome heads with fender washers and nylocks.

Or 120* counter sunk heads with fender(large) washers and nylocks.

Assuming the panel is still going to be composite.

But for now just use your Cleco's for mock up.

 

[Atuca]

NO.

Either Dome heads with fender washers and nylocks.

Or 120* counter sunk heads with fender(large) washers and nylocks.

Assuming the panel is still going to be composite.

But for now just use your Cleco's for mock up.

I totally forgot about the clecos!! Thanks for reminding me!

 

[snowborder714]

I vote countersunk if feasible.

 

[AngelOfPassion]

If it helps... I have an Apexi N1 AWD catback hooked up to an RRE test pipe. Hopefully that gives you an idea of how it is routed.

 

[Atuca]

Take some photos for me from right as it comes under the sub frame to the exit. Say a few from straight from the back, and a few from the passenger side looking at the driver side. No rish, you got at least two weeks before I cut into a fiberglass panel I'm guessing. Measurements would be even better, but I bet that be pretty hard to recreate on my side even knowing them.

 

[AngelOfPassion]

I need to get out and take those pictures. This time of the year just flies by sorry man.

 

[Atuca]

You hurry up? Haha you're funny!

I am remaking the diffuser panel mold out of MDF so I can make the groves without fraying, has to be done on a grainless wood. I didn't have the tools to do this though and had to wait on my boss to get his tools back from someone borrowing them.

Anyways he got them back finally this week. I'm going to try to do it Sunday, should be a one day project, and then we'll be molding it. Trying to mold the panel I been using for mock up just wasn't going to produce a professional mold.

That's the update for now. I'm aiming for before the end of the year, but you know how the holidays can be!

p.s. I am making the strakes 1 inch shorter, cutting the point at the tip that can't be formed in bulk runs. Nothing major and there will still be the end that sticks out the back a bit to be used for w/e, but the 5 inch will be kept still for strake height.

 

[Atuca]

Happy Holidays everyone!

As expected it took longer then just one day to redo the diffuser panel plug. Well, to make the plug just takes a day, but messing up one took us back an entire day, and as this was my boss assisting me, I didn't want to keep him held up for longer then needed in short bursts. The issue and confusion stemmed from the fact the DADO blades I had access to were 7/8 inch, not a full inch, so all the measurements and passes over the MDF took two passes, and the math and 1/8" margin of error was pretty tight for a tolerance.

That said, we are pretty much done with it and I am going to be turning it into the final mold. We got the idea to use "wall repair" paste to go over tiny irregularityies in depth btween the two passes of one strake indention, but I am extremely happy with everything. This will make a much better final product and make it easy to have repeatable results.

Here are some picture of the plug forming process!

 

[TheRaspberryKing]

Kind of a phantom around here, and have been watching this for quite some time. Looks awesome so far, cant wait to see the final product.

 

[TurboRacerGSX]

you ever get this done im interested in one.

 

[Atuca]

Positive plug is finished. Now to be fiberglassed!

 

[Archer Fabrications]

Is this gonna be produced or is this a 1 off

 

[Atuca]

It will be produced after it goes through testing with a few members on these forums.

 

[Archer Fabrications]

Shit I'll test it

 

[untouchablecc]

I think its awesome people are going out of there way to design stuff for our older platform, members no less. Thank you sir. I always though it would be cool to have/make one because of the space available back there.

 

[greengoblin]

What? Your not building this using a CNC router? Sheesh....

 

[Archer Fabrications]

If we were all so lucky