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Sneaky Aero...any suggestions?

Old 08-23-2016, 08:58 AM
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Default Sneaky Aero...any suggestions?

I run in a "Classic Japanese" road race class. Rules are that it has to look "classic". It is slightly lenient so I would like to add a very small front splitter and do something to the rear to balance.

Looking for suggestions from the brains trust here to improve laptimes....

For example. I do like the car slightly pointy, is going to a softer rear sway bar likely to compensate for a 10 mm / 1/2 inch splitter.....? Is that likely to be faster....

Sorry for abrupt sentences...using phone.
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Old 08-23-2016, 09:38 AM
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Kind of vague guidelines as I have no idea as to what period is considered "classic japanese" and what is allowed or disallowed.

But the FB RX7's of the era are great examples of aero use. I'm sure you could take some cues from them.



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Old 08-23-2016, 04:44 PM
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I recommend against compensating for aero imbalance with suspension changes and vice-versa. You want each balanced independently, otherwise you'll have a car that changes balance dramatically based on the speed you're moving (and adding splitter only means more oversteer as speed increases - typically not desirable).

A rear spoiler (not wing) can get you pretty far to balancing a small 2" splitter, and that's a very classic aero device. Look up examples in classic motorsports for build style/materials to replicate the classic look to satisfy the spirit of your rules.

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Old 08-23-2016, 05:17 PM
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A flat bottom floor wouldn't change the car visually, and could be coupled with a mild diffuser, that is styled to match the car.
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Old 08-23-2016, 07:23 PM
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Post link to rule set
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Old 08-23-2016, 07:49 PM
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The Series will represent cars of original factory exteriors (Group 1 & Group 2). Only period or factory spoilers can be used. It is important that these cars retain their original factory “look”, including full width dashes. There is an “Invitation Class” to cater for more heavily modified cars with non-original components.
Okay, now im not on the phone i can give a better background...

The series is based around "Classic Japanese" road cars from pre 91 (25 years and older - ish...). Spoilers, and bodykits are allowed so long as they are or look "period".

Its run as a democratic dictatorship (the best way to run a series, business etc) so unusual decisions do sneak in....


I already, only just - sort of, scrape in with the turbo...however the hondas run late model engines and the rules are a bit loosey goosey (in a good way)....some cars are fully stripped with no dash's etc...

Engines within period or model range.....gearboxes within model range, wheels and brakes are open. tyres are DOT rated. Im one of the last staying with Nitto, everyone else is migrating to Hankook z214 or similar...

I presume I could go "invitation" with a more obvious aero but enjoy the group 1 class. I figure a small splitter will sneak by but balancing the rear with something that's not a full blown wing will be the trick.....

I would love to run more full aero with the new wings like The Pass is doing but it would be more than the class is really aiming for and possibly not within our countries overall governing rules re height and extending beyond bodywork etc...

Below are some photos for an idea of vehicles in the class.....The Nissan 260z is the fastest by about 2 seconds and is a full blown "invitation" class race car, The CRX and my MX5 are group 1 leading and usually vying for the second fastest (when i'm running full boost) and the sylvia is a close and improving 4th. The class runs handicap for the 2nd and 3rd races with a practice/qualifying session grid start for the 1st race which is a non handicap sprint race..










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Old 08-23-2016, 08:05 PM
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FYI- mine is the only road legal car in the series (and still the fastest lapping MX5 in the country ) and as such has a lot of weight to come off...reasons for the thread question is this summer we are building a ground up race car from a shell we picked up earlier in the year....

On the table for consideration are sneaky aero, Xidas, 10" wheels with flairs, OS Giken, adding side intrusion bars (the car is way to fast to not have these now). It will be a matter of picking one or two from the "goodies"list based on best value for money. Performance wise...

Aero seems like a very good cost to performance gain though the "rules" make this a difficult proposition.....

Below is the an example of the new (considerably lighter) front nose section I have ordered. Another non turbo mx5 runs this in the series...this is what i imagined a small splitter could be surreptitiously added to..





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Old 08-23-2016, 09:09 PM
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In terms of rear aero it sounds like a ducktail spoiler would be acceptable (given that the 260z is running one and rx7's etc from that era had them?). Supposedly the lexan one's like blackbird fabworx produce work well, although you might need something more integrated looking to look the part.

In terms of sneaky aero, underbody mods behind the splitter to reduce drag might be helpful. Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com is a good resource - the community's aimed at fuel economy, but a lot of it's still applicable to going fast.
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Old 08-27-2016, 07:40 PM
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So the S13 is running a 3D rear wing. Can you? That will balance your splitter...

A flat front is probably out, but I still think my car looks fairly classic, using the GV style lip with a ply splitter...

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Old 09-01-2016, 02:03 AM
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Yeah I need to sound people out on that Nissan and the wing.

What wing are you running ? (it looks like within body and height rules like we supposedly have by the National body)
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Old 10-02-2016, 06:56 AM
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Okay, I think I can get away with this (below) from Carbon Miata.... Can anyone advise or guess whether this will add any down force? (or enough to help reduce lap time).

My feeling is that it should though I am not so sure about the square ends and it not coming around the side and extending forward like the common Rx7 style does....


I am also only really interested in doing something that will add enough that will require a small front splitter to balance. I think I can get away with a 5-6 cm (2 ish inches) splitter without too much drama.

So educated guesses on the worth of this...





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Old 10-03-2016, 11:26 PM
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The Project G rear corner flares might be stealthy aero...

Project-G - www.projectgla.com
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Old 10-05-2016, 10:55 PM
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don't think it's big enough to make a substantial difference.
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Old 10-06-2016, 01:28 PM
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That spoiler will help a little bit, certainly. Noticeable/measurable around a lap, I can't say... but since you're pretty much excluded from doing things that make a big difference, a little bit here and there is exactly what you need.
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Old 10-06-2016, 02:38 PM
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This one made my car much more stable at speed and in the faster sweepers. Doesn't look like much but it definitely reduced aerodynamic lift in the area over the trunk.




Larger ones would obviously generate more effect. And this one is likely much more effective than the one on the white Miata you posted.

Definitely put wheel spats in front of the front wheels. And get whatever chin spoiler/splitter as low as you can.

Wheels and brakes are open? You can do a lot with that.

It also sounds like you can change to an MZR powerplant if you wanted to get crazy. 2.0/2.3/2.5
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Old 01-01-2018, 07:16 PM
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I'm resurrecting this thread as I'm looking for more MT brain trust advice regarding stealthy aero. My car is a 320 WHP do-it-all toy that's used as a daily driver, mountain carver, trackday toy and (soon) Nürburgring weapon.

​​​​Due to both legal and visual reasons I cannot run any significant form of aero. That means no splitters, canards or wing and that sort. Besides the need to stay road-legal (splitters and wings might harm pedestrians etc.) I also want to keep my car looking as unobtrusive as possible. Ergo no cut front wings, airdam front bumpers etc. At first glance it should still look like your average lowered MX-5.
So realistically I'm not looking into making baller downforce but rather reducing lift/drag instead. The goal is to improve high speed stability on track. This is not gonna happen.

i have made the switch from the R-package lip to a GV lip in hopes to achieve a slight splitter/air dam effect. I want to build a flat underbody to speed up any air going under the car.
The front should be doable using alumalite. This is a picture of Keith's car, for reference.


In the middle I want to leave a gap around the catalytic converter for hot engine air to escape. I already have frame rails and a butterfly brace installed. I suppose this will make the air flowing through the transmission tunnel and exiting around the cat even more turbulent. I took some pictures of a friend's 599. It has a perfectly flat underbody with a functional diffuser, only 1 small NACA duct to the differential and a fully functional rear diffuser. Still the underbody a has a huge hole around the cats.



as for my car I'm afraid I can't build a proper diffuser. It wouldn't be allowed to protrude beyond the car, and the muffler would probably get in the way anyway. I could try to build a flat underbody right up to the muffler (plus a NACA duct for the differential) and do a slight bumper cut, but that's about it.
​​​​​​
on the upper side I have a hardtop, that's it. I know a KG works rear spoiler isn't a wing and doesn't get a lot of clean air anyway. However I'm afraid that even without a proper splitter my flat underbody will make the car more prone to oversteer. This isn't that much of an issue on tight mountain roads, but it definitely will be an issue once I hit the Nürburgring (no pun intended).

questions that keep me up at night are:
1. I think I could live with the look of a KG works spoiler, but would it really help with balancing out the added front end grip from a flat underbody?
2. Will a GV lip together with a flat underbody make the car oversteer a lot? Or will I be OK as long as I don't add a proper splitter?
3. Is there any benefit in running a flat underbody all the way to the rear bumper if I don't add a diffuser, and have an opening around the cat?
​4. Would adding a gurney flap before the open middle section help?
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Old 01-01-2018, 09:18 PM
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Flat floor is the answer
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Old 01-02-2018, 04:43 AM
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Originally Posted by Goingnowherefast View Post
Flat floor is the answer
well... uhm... thanks for making that clear
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Old 01-02-2018, 05:42 AM
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Not many people are going to know the answer to those questions. There is a ton of experience with balancing a front airdam with various amounts of splitter stickout with different wing configs. However I have never seen anyone in the enthusiast world do any kind of meaningful before/after measurements that isolate the effects of a flat floor with or without diffuser. You'll have to build it in steps and see what the car needs to balance itself. I suspect even balancing out the gv-lip/undertray combo will prove difficult with just a spoiler.
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Old 01-02-2018, 09:35 AM
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As a sample size of one I can tell you that the KG Works rear spoiler did help to settle the rear end of my car on of the faster tracks. It was a notable difference in stability at turn one of Miami Homestead Raceway where turn in speed is above 100 miles an hour.

A spoiler works by slowing down the air moving over the surface immediately in front of it, thereby reducing the lift generated on that surface. In this case it reduces the lift created by the fast movement of air over the trunk lid. This differs from a wing in that a wing actually creates negative lift where is the spoiler is reducing existing positive lift. Fast air movement over surface is how a wing creates lift.

I'm currently using the imitation GV lip and brake ducts that go with it in combination with the spoiler.

You may also find that ducting your hood will reduce front-end lift by reducing air pressure under the hood pushing upward and by introducing a slower-moving air layer boundary at the outside surface thereby reducing surface lift.

Viel Glueck (no umlauts on this phone).
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