Mr. Adair

Why do I not see more talk about matching the rear wing settings, spring rates, dive planes, camber etc. of the 4.0 to the 3.8? Or do most track guys just eventually end up there anyway? Please hold the learn how to drive first comments . I'm actually very curious. Here is the Excellence Mag info from AP. Educate me..

https://www.excellence-mag.com/issue...3#.Wt5EQWbMz6Y

adi_d

I think aero makes a huge difference, which is why it's so tightly regulated in motorsports. Part of the issue is setup and proving it's effectiveness. Unlike mechanical grip you just have to trust it, which opens it up to variables like driver skill, tire choice, etc.. While logically the process seems straight forward (i.e. more downforce in the back, requires more downforce in the rear) the reality is that it impacts many components of the car, including suspension geometry, required spring rates, specific tire settings/sizing and so on. It seems that for DE most people just stay away from the headache and on the street you can't really feel it regardless.

From my experience, on our NorCal tracks, which do not have huge/high speed straight-aways, the addition of aero made a huge difference in lap times but was a bear to balance properly before the car became really enjoyable.

Mr. Adair

Agreed and thanks Adi. AP pretty much spells out the what they did to improve high speed aero on the 4.0 from the 3.8. The factory pretty much gets this stuff right. I'm just surprised I don't see more people adopting that set up if it's proven, on to a 3.8. Then again I see guys with Cup wings and no dive planes and every combo under the sun. So I was just curious to see if it was plug in play. It's not lost on me that these changes only make a difference in drivers much much further along the me! I am curious about this stuff however and love to learn..

adi_d

You are right, the factory figured this stuff out. My guess is that 3.8 to 4.0 setup is somewhat cost prohibitive as those OEM parts are pricey. I went the cup route and just purchased all the motorsport parts, again assuming the factory has it figured out. However, some people could not deal with that look as it is rather extreme. Even with cup parts not everything is plug and play, including springs, alignment, etc. as the street cars are heavier and don't have all the setup options, nor do they run the same tires. When i first setup the aero, the car had massive understeer and it took a while to set it up and re-learn some of the driving dynamics.

CRex

On the assumption that the driver is there to take advantage of the aero:

1. The front splitter is the most important aspect of these cars' aero. Lose that and the car will noticeably understeer in anything beyond low/mid-speed corners.
2. The front dive planes on the 4.0 help. But not nearly as big of a deal as the splitter
3. The two rear wing positions on the street car don't make much difference. More about balancing the FvR if you've added a cup lip or dive planes to the front.
4. 4.0 end plates are larger and increase efficiency by limiting the roll-off from top of your wing to the bottom. Trivial in real life.

So there you go: (1) is the same in the 3.8 and the 4.0; (2)(3)(4) are really marginal improvements.

Now whether a non-pro driver can objectively tell the aero difference between the 3.8 and 4.0 just from driving--that's a completely different matter.

Mr. Adair

ilko

So what I've done on my car is to install the Cup front splitter and 4.0 dive planes in the front. I raised the rear wing by 4" using the Cup uprights but did not change the angle. The wing now operates in much cleaner air and is more efficient even at the stock angle. I'd like a set of the larger 4.0 wing end plates and started a group buy thread to have replicas made (OEM are NLA last time I checked) but there was very little interest...

a_Y

I would be interested in the 4.0 wing end plates in CF!

Mr. Adair

Thanks ilko..

I remember your thread...

I'm still interested in 4.0 end plates if they can be painted. How many do you need to make it work? My guess is helluva lot more than 2 or 3. In terms of the 4.0 dive planes Suncoast still has them but a crazy *** prices. FVD has copies which I am considering if they are really accurate copies and I can paint them I would consider...

ilko

When I spoke with the fabricator, they needed 10. Do you have a link to the FVD copies? Thanks!

Mr. Adair

Here you go..

https://www.fvd.net/us-en/FVD505997G...-40-style.html

If you give them your blessing I'll pick up a set as well..

isv

Polesitter

I think Crex's comments are correct. I am unsure what you are trying to achieve, but assume it to be better aero grip and balance in general. I still own and have raced 997 cups in IMSA and have a 4.0 street car which i do not track. Both cars chronically understeer. If you think the splitter isn't critical, try losing one mid race at a high speed track and you will come to appreciate it mightily. I've had this happen at Road America and Mosport, the latter particularly unpleasant. I have always wanted to use 4.0 type front dive planes on a cup car to see that they would do, but never could per the regulations. I think any additional downforce up front would help

We have generally found rear wing adjustments to have a modest effect on rear aero grip. A rake adjustment might help you somewhat and we have found a gurney helps stabilize 997s under heavy braking at high speed.

All that said, my experience is limited to the tightly regulated envelope in cup cars and some limited toying around with the 4.0. With an anything goes approach you may have more options. Just bear in mind that each adjustment may solve or improve one problem but induce another. Only trial and error can help you optimize.

ilko

Ah, I misunderstood you. Thought FVD had end plates. I bought a set of the FVD dive planes 3-4 years ago but the CF quality was poor. Rhonda took them back, she's great. But they might work for you if you plan on sanding and having them painted red or other color. My current set was purchased from GMG and I picked them up from someone on this forum. Theirs retail for double what the FVD ones go for but the quality is superb!