Time Trial Build Thread (aero, widebody, any other nonsense)
 

Instead of filling this forum with individual threads I'll just keep this post updated.

I've been reading way to much about aerodynamics (if you couldn't tell from my aero hood post or diffuser post) and decided to try and increase airflow to the rear wing (and to the intake in the rear window) by installing vortex generators on the hood just ahead of the stall line on the roof (or where the airflow leaves the roof's skin). I've never really been a fan of how these look but they turned out pretty good.

The diffuser and the widebody are progressing too. I'm still waiting on the last pieces of hardware but decided to limit it a 4" increase (no spacers in the front 2" spacers in the rear. I should have update on Wednesday.

:cheers:

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Pretty sure this will be a great thread.. Keep it coming!! :dance:

Any thought to ducting air directly to the filter from the outside rather than the round louvers in the rear screen? I have seen side NACA ducts on either side piped to the top of the engine where an oil cooler sat. This arrangement could work for engine intake air.

You are doing proper analysis.
Kudos to not just throwing stuff on your can and using a butt dyno
Aerodynamics is at least a little complicated and without modeling or wind tunnel testing, you can easily do something that makes it worse

Well done

Thanks, I can’t take any credit for the aero model though. Nine8Six Shared it with the forum months? Years? Ago. I should have given him credit. It’s incredible
To have this available. Aero is very tricky, I’m sure what I’m doing isn’t anywhere near as effective as it could be (or maybe even at all) but it’s time consuming which is exactly the kind of thing we all need now.

I'm really getting into the danger zone now I've started another project while I wait for parts. The first picture (credit to Eric who took the photo) is what I'm after. Flares are arriving on Friday and I'm going to incorporate this vent into them. I have a replacement for this banged up fender so worst case I have a backup. :cheers:


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I started the flare install yesterday so far the $30 Amazon flares are working out
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I have fender flares and wider tires on my rallycross boxster. I had to do some trimming on the rear wheel well for clearance. For the front I also had to cut the rocker panel back flush with the wheel well and some of the bumper cover. I don't have the side radiators anymore but the wide wheels would not have fit in the front if I still had them.

I notice you have a wing and a large spoiler on the rear. I've never seen anyone have both and I've never seen anyone use such a large spoiler on a boxster that races at a high speed. The only guys I see using large spoilers are in autocross where they rarely even get out of third gear.

I forget what they're called but that picture of the cup car has them in front of the front tire. I've been told you can find them on eBay for cheap. Do you have those on yet?

Did you widen the front of your car with spacers? I widened mine by extending the control arms, thrust arm, sway bar links, tie rods, raising the strut in the hub and moving the shock tower mounting points out. Not the easy way to go but this avoided increasing the scrub radius and will avoid having to move the radiators and cut the rocker panel.

As far as the wing and spoiler go they look silly but accomplish two different things. The spoiler reduces lift and drag and the wing provides downforce. Take a look at Porsche’s factory wings, they all incorporate both. I run the car in time trials at tracks like VIR and summit point so yes high speed. Back to back runs the wing reduces VIR lap times by 3 seconds, there isn’t a single car in my group without a huge wing running time they’re critical.

Finally if you’re referring to the canards on the cup car I don’t have them. I do though have a large splitter and a hood extractor (you could almost crawl through it). The hood extractor creates downforce by forcing air through it with a longer path than the air traveling over the bumper (same idea as wing). Here’s some photos, I’m going to redesign this to be fed with a diffuser in the splitter instead of a hole in the bumper.

The NACA ducts in the headlights are brake ducts in case you’re wonder.

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In process shot showing the inside
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I like that spoiler - willing to share any details on how you made it?
Also - have you tried slathering flowviz over the panels to see what the surface structures look like?

I used very thick wheel spacers. It's not something I plan on using for long. I'm testing out some tire theories and the wheel/tire combo wouldn't clear the struts without them.

Hard to argue with the spoiler if it shows it improves lap times. I might try it for my too

Have you thought about finding a wheel with the right width + offset?
Here's a handy calculator: https://www.1010tires.com/Tools/Wheel-Offset-Calculator

As a reference point, the 997 Cup came with the following (EXPENSIVE) wheels:
Rear 18x12 ET30 (997.362.140.97)
Front 18x9.5 ET37 (997.362.136.96)

These dimensions would get you +4" in the rear but you would need some hefty spacers (which it looks like you already have) as the inside has 42mm less clearance.

Do you have a thread with details of your wing (brand, size, etc) and how you mounted it? If not please provide details :)

Sure! Unfortunately I have no idea what kind of wing it is, I bought it second hand. The only thing that was important to me was that it was no wider than the car (Time Trial doesn't allow it) and that the support were no wider than the trunk. Most people mount their wing to the trunk however my trunk is actually a thin piece of clear lexan from Lowes that I cut out with a jigsaw and then wrapped so I mounted mine to the trunk floor instead. The wing mounts weren't long enough so I cut some aluminum plates with the same jigsaw and used them to extend the mounts that came with the wing. The spoiler is made from a composite aluminum/plastic sheet that I made with...a jigsaw. :cheers:

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Here's the "trunk lid". Super lightweight and super cheap.

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I do eventually want to put some wheels on the car that fit, unfortunately (as you pointed out) 911 wheels won't work. I actually have 18x12" wheels on the back on my 911, all of the extra width is on the inside of the wheel. This is possible on 911s since they have a multi-link rear suspension and don't have the long track arm that gets in the way of the wheel. If anyone knows of a cheap 17" wheel that can be ordered in custom offsets please let me know.

I don't know how these offsets would work or how "cheap" but here is one wheel you can get in configurable offsets:

https://momo.com/en/product/heritage/road-wheels-heritage/heritage-6/

I have a different set of Momo 3 piece wheels (I haven't been able to identify the model #) that have a pretty big "back" barrel, you could possibly reassemble with the barrels reversed and have the bigger barrel be out the outside, they would be pushed out more than 4", and I could take a measurement and see. They are approximately 17x10 and 17x9 (from a Cayman IMSA GT 2.9), I was going to run them on my Cayman but doesn't look like I am going to have my tire trailer hitch resolved anytime soon and so these are just sitting, $800 plus shipping (what I paid) Next time I get to my storage I'll measure the barrel widths and send them to you, if that might work?

Hell ya! Let me know

You can search available wheels by size bolt pattern offset, etc here: https://www.1010tires.com/Wheels?activetab=bysize

Boxster bore is 71.6 so you could do anything that size or larger w/ hub centric rings.

While I'm waiting for the flares to come back from the wrap shop I installed the fender vents that I made a couple weeks ago. The fender flares fit right up against these so you won't be able to see the thin strip between the vent and the wheel well

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Over the weekend with tons of time on my hands I decided to redesign the hood extractor. When I was at VIR a couple months ago the air coming through the bumper opening was enough to cause the hood to bow up about an inch which shows just how much air and resistance this design was creating. To reduce drag I decided to close the bumper opening, cut a hole in the bottom of the car and built a front mounted diffuser so the hood could pull air from underneath the car (the splitter in not installed in these pictures). If only there was a track to test this out on... Its hard to tell from the photo but air would flow to the hood from the other side of the curved aluminum piece. I probably need to install a plate over the front of the bumper to hide the curve piece since air cannot escape into the hood or anywhere else


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pretty cool stuff. I love that you are willing to try **************** out, even if its unorthodox.

Talk to me about those naca ducts in the head lights. What size hose do they run to and how are you ducting to the brakes?

also, it seems you don't have a center radiator. What sort of temps are you seeing.

One thing I've thought of is using a WRX hood scoop on my trunk lid running to the trans and up to the heat exchanger. Might be a pain to route the hoses, but my car is not full track yet, so I haven't gone full nutso.

The NACA ducts use 2.5" (I think, I'll confirm later) hose to connect the rotors to the ducts. I hollowed out the back of the lights to make them work and then rewired the head lights to the fog lights so I can still see when driving around at night in the paddock. The turn signals also still work.

You're right I don't have a third radiator, my first approach on the car was to make it as light as possible so I wanted to avoid it. It doesn't overheat at all even on 100 degree days though. I don't have AC condensers blocking the flow and I cut the wheel wells out to let the air flow through the radiators right into the wheel wells (the factory design requires the air to turn and exit under the car) so I'm sure this helps out as well. Oddly my 911 (996 3.6) has the same radiator setup (no center radiator) and temps start climbing on the track on really hot days. I can't believe they didn't put a third radiator on all the 911s.

I'm trying to picture your WRX scope idea, are you trying to cool the transmission fluid?

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Did you strip the wheel well area of everything? charcoal canister, washer fluid bottle and liners?

Yep, the car is stripped of just about everything.

I finally got around to checking the front track width and found I made some serious miscalculations. The front track width (hub to hub) is now 66"s, factory is 56.89. So the front is over 8"s wider than the stock design (10" wider with the larger wheels and tires). The problem is the rear is only 4"s wider, I can order 3" spacers but the front will still be 2" wider than the rear. I wonder how problematic this will be.

EDIT: I'm finding conflicting info on factory hub to hub measurements, but it seems the rear from the factory is almost 3 inches wider than the front. So if put 3" spacers on each side of the rear everything will shake out to being square (66"s width in the front and 66"s in the rear). In other words, crisis averted...maybe

woof, 3" spacers.

Your wheel bearings are gonna LOOOOVE you

The reason I ask is if you had thought about air pressure behind the front tire? I see lots of race cars where that area has been notched. It seems like an easy thing to do if you've removed the charcoal canister and windshield wiper fluid reserve.

Quick update, I got the flares back from the wrap shop. Turned out alright

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Looking good, but are those James Bond Effect flares?

Haha, love it! I can’t believe I didn’t get flares with built in ground effect lights. What an amateur move.

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I'm really running out of things to do but I had another idea last night and made a louver cover for the hood. Its not done yet and still needs to be wrapped but you get the idea. I'm going to try and copy the livery underneath the vent with the wrap. So the teardrop and numbers will be printed on the wrap.

Its all starting to come together! The suspension arms have all been extended (this was a horrible pain to get right and the sway bar linkage is still questionable) and the hood and wheel well vents have been wrapped

:cheers:

Here's everything I did to extended the suspension on the front of the car.
-Extended Elephant racing control arms using longer collars and hardware
-Installed rear toe arms (which are longer than tierods) on the front to replace and extend the tierods. These needed to be extended even more with adjustable end links
-Since the arms are longer the strut also needed to be extended, I drilled new holes in the strut and raised it in the hub
-Moved the strut mounts out by drilling and grinding a spot for them into the chassis
-modify strut bearing to fit in new location of the chassis
-Install adjustable toe links
-install spacers on the swaybar linkage and extend hardware
-cut fenders and install flares

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some interesting stuff going on. The hood looks good.

the suspension is a little dodgy in my eyes. There are just too many things changed from how they were intended to function. I'm not sure if you have an engineering background, but I'd want it looked over by someone with a suspension design background before going out and pushing it on the track.

Maybe it will be fine. Either way, would be interested to hear your impressions after some time on the track.

Those sway bar extensions seem like they might act like a soft extension, if they flex it may have the effect of softening the front bar.

Maybe you could attach higher up, maybe on that notch where the brake sensor wire used to go? Although I don't know how string that is. Maybe the Tarett extended front links?

Car looks great, can't wait to hear how it does :cheers:

What’s happening under the hood? Did you add another duct that feeds the hood louvers from the underside, raise the front edge to split the flow, or something else?

Originally I had an opening in the bumper but I changed that design and now have a diffuser in the splitter that exits through the hood vents. The diffuser isn't installed in the photos.

ya.. I'm a little worried about it. I am a mechanical engineer but I'm not a suspension engineer. I've had a lot of people who build race cars look at it but who knows. We'll just have to see how it does.

I would LOVE to see pics of the underside when you get a chance

The governor just lifted the state inspection requirement so look who now has a street car! It attracted a little too much attention to be an enjoyable drive and its loud as hell but it was still great to get it out. With the exhaust on (which doesn't do much) the in-cabin air filter is deafening. I guess I've never heard it without a helmet on. Its incredible how much air engines take in.
:cheers:

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Some of you have probably seen my "Wild Japense Racecars" post earlier this week, I can't get over how great these things looks (if you haven't seen the post here's a teaser)
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http://986forum.com/forums/boxster-racing-forum/77859-wild-japense-986-racecars.html#post617405

Last night I played around with some cardboard and mocked up some rear flares that would be make out of aluminum. Getting the template right will be really really tough but cutting and bending the aluminum. The idea is they would sit against the flares I already have on the car and the openings in the new flares would be used to the engine intake (I'd move it again) and an oil cooler on the other side. There is of course absolutely no good reason to do this except to save me from going made during the Quarantine

:cheers:

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