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

[truegearhead]

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.

[Robert986]

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

[jaykay]

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.

[JayG]

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

[truegearhead]

Originally Posted by JayG

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.

[truegearhead]

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.

[truegearhead]

I started the flare install yesterday so far the $30 Amazon flares are working out

[itsnotanova]

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?

[truegearhead]

Originally Posted by itsnotanova

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.





In process shot showing the inside

[Stroked & Blown]

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?

[itsnotanova]

Originally Posted by truegearhead

Did you widen the front of your car with spacers? d. 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.

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

[Stroked & Blown]

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.

[steved0x]

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

[truegearhead]

Originally Posted by steved0x

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.



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

[truegearhead]

Originally Posted by Stroked & Blown

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.

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.

[steved0x]

Originally Posted by truegearhead

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?

[truegearhead]

Originally Posted by steved0x

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

[Stroked & Blown]

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.

[truegearhead]

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

[truegearhead]

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