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My autocross FD SM2 build up

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My autocross FD SM2 build up

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Old 05-09-18, 11:40 PM
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The in-depth answer.

The wing adds downforce at speed.
You can set the car to be rotate-y at low speeds with no/very little understeer and then at higher speeds the wing will help settle the car into neutral or understeer bias for the higher speed sweeping turns.

Basically, the wing can take the edge off the car.
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Old 05-10-18, 09:38 AM
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Originally Posted by Valkyrie View Post
How do you keep it from understeering with such a big wing compared to the relatively tame front aero?
The big wing was essential for the lower speeds that you see in autocross. We could do 78 mph in 2nd and never shifted to third. It is now gone as the car will also be seeing track duty and that wing would have produced way too much downforce at track speeds of 140-150 mph. I have opted to go with a 99 spec wing that should be delivered today. The series limits the wing height to 8" and chord length to 8" as well and the 99 spec wing is within those numbers without looking like an ugly afterthought.

Brian
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Old 05-10-18, 10:00 AM
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Hey Brian will you run it in the GTC or GTL class? Will you have to add weight to the car to get to their 95% of curb weight rule? Will you have to make significant exhaust changes to meet the 103db requirement?

Thanks for updating the thread and please keep us posted as you continue the build and take it to events. Are you targeting any specific events to kick it off?
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Old 05-10-18, 10:15 AM
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Nice seeing this car being worked on.
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Old 05-10-18, 03:28 PM
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Originally Posted by Smokey The Talon View Post
Hey Brian will you run it in the GTC or GTL class? Will you have to add weight to the car to get to their 95% of curb weight rule? Will you have to make significant exhaust changes to meet the 103db requirement?

Thanks for updating the thread and please keep us posted as you continue the build and take it to events. Are you targeting any specific events to kick it off?
GTC. The car had gotten down to 2522# at its lightest, so yes I have had to add weight, but a lot of that needed to go back as prep for the series. I have put the full size fuel tank back in, added back a stereo, speakers and antenna, put the factory seat belts back in, put the horn and rearview mirror back in, etc. I have not weighed the car yet, but will add ballast if required to get the car to around 2650#. That being calculated from the base weight of 2789 x .95% = 2650.

The exhaust is not an issue as the car was typically around 93db at the SCCA events.

I am signed up for NCM and Barber, both tracks that I have hundreds of laps at, but none in a car with more than 150hp!

Brian

Last edited by SBrian2; 05-10-18 at 04:07 PM.
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Old 05-10-18, 03:41 PM
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Sounds like an interesting racing series. Are you going to autocross anymore? Don't you have to have a roll bar at Barber?
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Old 05-10-18, 10:54 PM
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Originally Posted by BLUE TII View Post
The in-depth answer.

The wing adds downforce at speed.
You can set the car to be rotate-y at low speeds with no/very little understeer and then at higher speeds the wing will help settle the car into neutral or understeer bias for the higher speed sweeping turns.

Basically, the wing can take the edge off the car.
Is that a bad strategy for track cars?....

last year my car understeered pretty heavily at high speed with my new aluminum (steel?) wing.
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Old 05-10-18, 10:55 PM
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Originally Posted by SBrian2 View Post
The big wing was essential for the lower speeds that you see in autocross. We could do 78 mph in 2nd and never shifted to third. It is now gone as the car will also be seeing track duty and that wing would have produced way too much downforce at track speeds of 140-150 mph. I have opted to go with a 99 spec wing that should be delivered today. The series limits the wing height to 8" and chord length to 8" as well and the 99 spec wing is within those numbers without looking like an ugly afterthought.

Brian
Right... if you could event make it to 150 without tearing it off the hatch.
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Old 05-11-18, 10:36 AM
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Is that a bad strategy for track cars?....

last year my car understeered pretty heavily at high speed with my new aluminum (steel?) wing.


I don't have any experience on a real track, but I imagine it would work; you would probably just employ the same strategy to a lesser degree.

Probably not going to be able to compensate for huge amounts of high speed aero-understeer just by changing around the rest of the chassis settings- might have to add more front aero or reduce the rear.

You could try higher rear spring rate or putting in some pre-load so the rear downforce doesn't pitch the front up and create more front lift to exaggerate the aero imbalance. IDK what your set-up is now.

Check your lap times too.
If you still have faster lap times with the wing than without while driving under the limits of the front understeer- I think you just "slow down". There have been some really dominating cars with some serious handling "quirks" due to conforming with a rule-set.
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Old 05-18-18, 11:24 AM
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Originally Posted by evo_koa View Post
Sounds like an interesting racing series. Are you going to autocross anymore? Don't you have to have a roll bar at Barber?
it depends on the event.

If you are on the track racing for a timed lap then you usually have to have a bar. IE nasa, scca, bmw club, porsche club.

If you do a track day then usually cars with roofs do not have to have a bar. You can "self time" or record your sessions with the new data acquisition stuff, but you are not "racing" for a plastic trophy like the other events.
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Old 05-19-18, 12:24 AM
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How do you like the EFR 8374 for autocross? How much power are you running it at?
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Old 05-21-18, 12:16 PM
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Originally Posted by scotty305 View Post
How do you like the EFR 8374 for autocross? How much power are you running it at?
The 8374 is awesome. Everyone was saying it was too big when we spec'd it out, but it is the right turbo for these cars, very responsive down low. Actually more responsive than the 99 spec twins it replaced with having a lot more headroom up top and no quirky transition from when the 2nd turbo engages.

Best numbers were 430 whp on a DynoJet, that is at about 20 psi. There is probably more there, but we felt like that was as much as we could put down anyways. Now that I am switching from Hoosiers to 200TW tires, I may have to cut it back.

Brian
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Old 05-23-18, 08:23 AM
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Nice thread and build!

Subscribed
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Old 05-29-18, 11:09 AM
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Well, I think she is all ready except for checking corner weight and alignment. Here is the final product!




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Old 05-29-18, 12:48 PM
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man that looks great.
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Old 05-30-18, 11:15 AM
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agreed, looks great. Keep the updates coming. I'm interested to see how your intake temps do with what looks like a coolcharge II intercooler. You running any water injection? I use a PFS intercooler and without water the temps get out of control, but I'm also guessing your 8374 will be better on temps than my twins.
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Old 06-07-18, 07:56 AM
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Looking very good!!

Do you possibly have any pictures of the mounting of the front splitter?

Really looking into making one.

Cheers,
Kostas.
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Old 06-08-18, 09:52 AM
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Things went reasonably well at the first event last weekend. It took a bit to get used to the amount of throttle modulation required with the Rivals S tires, but finally got within .070 seconds of the fastest lap of the weekend on the autocross course, which I believe put me 6th or 7th overall. Design and Engineering went very well considering this has been a race car the majority of it's life and was just refurbished as best I could. I was 20th overall against many high end six figure cars. We did the Road Rally Saturday night without issue, except for burning about 5 gallons of 110 octane fuel. The car has amazingly good highway manners for what it is.

Sunday started with the Speed Stop Challenge and the car put up good numbers out of the gate and I wound up 4th overall in that segment. The road course was what I was most worried about since the car had never seen a big track. I have hundreds of laps at NCM, but all in a n/a Miata. After a few laps, I quickly realized the stock brakes with HP+ pads were just not up to the task, then oil started blowing out of the hood vents on the windshield from the catch can. I came in and assessed the situation and knew it was going to be a tough go the rest of the day. I decided to grid in the back of the pack for the next few sessions and take an easy out lap and make one flier, then shut it down. That worked well enough and got me a respectable lap, but still not where I wanted to be. I think I was 15th overall for the track sessions.

My main competition had clutch issues on Sunday and never left the garage, so I ended up taking the win in GTC, but put up good enough numbers to be 5th overall for all classes! Even if he had won both events on Sunday, he wouldn't have caught me. I accepted the invite to the Invitational this fall and the car will be on display all week at SEMA. Now to fix the catch can issues and get a set of Wilwoods for the front of the car and see if we can improve at Barber in August!

Here are a few shots from the event.



Brian

Last edited by SBrian2; 06-08-18 at 10:00 AM.
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Old 06-08-18, 09:54 AM
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Originally Posted by Smokey The Talon View Post
agreed, looks great. Keep the updates coming. I'm interested to see how your intake temps do with what looks like a coolcharge II intercooler. You running any water injection? I use a PFS intercooler and without water the temps get out of control, but I'm also guessing your 8374 will be better on temps than my twins.
I am running a Devil's Own water injection kit.
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Old 06-08-18, 09:59 AM
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Originally Posted by Nabu View Post
Looking very good!!

Do you possibly have any pictures of the mounting of the front splitter?

Really looking into making one.

Cheers,
Kostas.
I don't have any pictures, I'll try to snap some next time I have it off. It has an aluminum square tube frame riveted to the top of the splitter and all of that attaches to 4 members coming off of the frame of the car that are also aluminum square tube. The struts are then attached to the front rebar. Removing one end of the struts and 4 bolts will remove the entire splitter. It is easiest to do if the car is on the lift with the wheels off since it comes back all the way to the front tires and front cross member.

Brian
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Old 06-09-18, 02:53 PM
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Congrats on the strong showing, those photos look great. There have been a few threads of people discussing oil catch cans, please post what you find. I've heard of Radium Engineering as a maker of oil separating catch cans, but haven't tried one myself and haven't kept up lately to see if other rotary owners have tried them.
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Old 06-11-18, 11:20 AM
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Great to hear you had a successful event overall. I feel your pain with the catch can. The best results for catch cans have come on single turbo cars that put a 2nd vent line that vents from the unused oil drain from the twins.
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Old 08-10-18, 12:02 PM
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Here is a recap of event #1 at NCM:

We went to event #2 at Barber last weekend with a rerouted catch can and new Wilwood 6 piston brakes on the front and the road course was trouble free! Another good showing and Class win from that event. Now we are on the wait list for Road America to see if I can take the National Points Championship!
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Old 08-10-18, 12:30 PM
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Thank you! Thank you! Thank you for taking the time to make the video (subscribed of course).

Looked awesome.
I clutched at my keyboard on the track event when you went 2 over the curbing on exit, but the chassis soaked it up like a pussycat. Very nice.
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