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Discussion Starter #22
Material for the final version of the spoiler was ordered, so that should be finished next weekend. We also got confirmation that we will have access to a wind tunnel. No specific date set yet. We are asking for at least four hours of tunnel time. Hopefully we get more. One requirement of the wind tunnel is that the car is painted one color. We started sanding the terrible paint job that the previous owner gave the car.





A quick test of the paint we were thinking of using.



Diffuser is mocked up. Still undecided on final material, but this is generally how it is going to look. Need to rethink the mounting because it's a little hard to put on and is flexing in the middle. The fences also fold in more than I would like.





 

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Discussion Starter #23
Decent progress on the car

Mocked up the splitter so I could add the center support rod and brainstorm on some aero fenders.







Still not set on a design, kinda want to make it stretch further back on the fender and maybe some work on the attachment to the splitter. The center splitter mount means I can stand on the splitter though.

Some more weight reduction. Took out the blower motor and AC evaporator. Around 13 lbs





Today was the day!























Still need to paint the trim black and give it a polish, but not bad for $30 of spray paint.
 

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Discussion Starter #25
First event was today. Ended up 4th in class out of 16. Even beat a couple of people on Hoosiers. 3rd through 7th were within half a second of each other.

 

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Discussion Starter #27
First event with the spoiler on. Not sure on how much it helped. This surface isn't as grippy as the parking lot at ZMAXX. More and more do I feel the need for an LSD. It loves to spin the inside wheel at the exit of every corner even with 275 NT01's. The little bit of extra power from the new engine also made that problem worse

 

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What are you doing for springs and sway bars? A very light or no rear bar plus fender springs in the rear tend to make problems like that go away. Really stiff single springs on light cars are bad because you’ll run out of travel quickly. A short tender spring that’s like 150-200 lb/in will be bound in normal suspension movement, but on the inside corner it will unbind and can give you quite a bit of travel at a lower rate. It really stops inner wheel spin in my experience.
 

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Discussion Starter #29
What are you doing for springs and sway bars? A very light or no rear bar plus fender springs in the rear tend to make problems like that go away. Really stiff single springs on light cars are bad because you’ll run out of travel quickly. A short tender spring that’s like 150-200 lb/in will be bound in normal suspension movement, but on the inside corner it will unbind and can give you quite a bit of travel at a lower rate. It really stops inner wheel spin in my experience.

Stock sway bars with 5k front/ 8k rear springs. No helper springs.
 

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Discussion Starter #30
What are you doing for springs and sway bars? A very light or no rear bar plus fender springs in the rear tend to make problems like that go away. Really stiff single springs on light cars are bad because you’ll run out of travel quickly. A short tender spring that’s like 150-200 lb/in will be bound in normal suspension movement, but on the inside corner it will unbind and can give you quite a bit of travel at a lower rate. It really stops inner wheel spin in my experience.

Stock sway bars with 5k front/ 8k rear springs. No helper springs.
 

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Might want to look at tender springs (this is different than a helper spring). Tender springs have a rate much higher than helper springs, which are typically closer to a zero spring rate.
 

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Discussion Starter #32
First event running the full rear aero package. It felt more stable, but because the aero balance was now thrown off and the fact that the tires are heat cycled out and the the front are corded meant that the turn in felt worse than usual. still managed to be in the top 25.


F40 style engine cover installed. Right now it is not easily removable, but I have an idea for easy, tool less removal.





New tires for the rest of the season.



Car is now waiting for it's wind tunnel appointment next week
 

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Discussion Starter #33
Wind tunnel Day!!!

Biggest takeaway is the spoiler is super inefficient, as expected. It made decent downforce, but lot's of drag to go with it. We chose that route because of the cost and ease of manufacturing, but I think it's worth it to switch to an actual wing. The spoiler alone basically doubled the drag coefficient.

The engine cover is helping the flow stay attached to the body, but adding vortex generators on the roof allowed the air to stay attached for a little while longer. Also the engine cover needs more supports, and maybe even bow out a little.

The Diffuser didn't really do anything. The flow vis showed the air being directed upwards, but no noticeable change in downforce or drag. I assume this is partially due to the ride height of the car. It's as low as i can get it while still having tire clearance. Only way to lower it is cut out some of the fenders.

We are a bit mixed on which size splitter to use. My idea was to max out the front downforce and add rear to match. Autocross is so much about being able to turn in quickly I want the front end to get as much help as it can get. Others are worried about the loss of downforce in the rear, but I think the difference is so minimal that the more front we can get the better. The bigger splitter also gave it a pretty good aero balance.

Lastly the fender extensions, I don't think they add enough to warrant the extra 4 inches or so added to the width of the car.

A closer look at the data is needed to decide on the final set up.














 

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Discussion Starter #34
Some more weight reduction

Dash and AC/Heat removed. The bar behind the dash has a ton of surface rust on in. Luckily it simply unbolts so I can take it to work and blast it and paint it.

Overall it took 38 lbs, plus the AC evap and blower motor makes ~50 lbs removed. Hopefully this and removing the engine lid and side panels, and the removing the stock spoiler will more than make up for the added weight from the aero kit. The massive spoiler actually weighs less than the stock one. The biggest weight gain was the plywood splitter.





 
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