Aero Questions & Clarifications

[boomn29]

Hello all. Looking into some aero on my new build and want to be sure everything is built to the rules. I know a lot of people have been dinged over the years with extra aero pts so I wanted to gather some expert (loosely used!) opinions.

 

My questions relate to rules #1 and #2 of the updated Aerodynamics section of the 2011 rules. I'm wanting to build a front splitter (#2), and create it as large as I can within the ruleset without creeping into more pts. The pare I'm worried about creeping into is #1 which is modification of the front fascia or air dam.

 

G. AERODYNAMICS:

1) Add, replace, or modify front fascia or air dam +3 (except as provided for in I.c.3), I.f.3), I.h.14) of the No-Points Modification list) (note: Additional points must be assessed below for any component of the added/replaced/modified fascia or air dam that performs the functions listed in G.2) and G.4) below)

2) Add, replace or modify a single front splitter/spoiler/wing/foil +3 (note: This part may extend horizontally past the side of the vehicle no greater than five inches. If any portion of this part that protrudes from the side of vehicle is not parallel to the ground, then additional points must be assessed for canards in G.4) below.)(note: No material or part may extend the vertical reach of the OEM front fascia without taking fascia modification points above.)

Here's what I'm thinking to qualify for a splitter / #2 only:

- Retain stock bumper

- max 5" extension outward from bumper

- no vertical (up/down) canards at any point

- must be flat; nothing that extends the vertical (up/down)

- attached to? - bumper directly?? How far can I drop it down from the bumper without it counting as an air dam?

[yakisoba]

I read this as:

You can build a splitter, but it can't extend beyond (in front of) the stock fascia of the car. It can't extend more than 5" beyond the side of the car (width). It can't have anything but a flat shape, or you take points for canards.

 

When you say "5" outwards from bumper" that might bring you into conflict with the not past the stock fascia provision, if it's your intention to extend it forwards.

 

But I'm not an expert. C5 generally don't do aero in TTA (no points left).

[Greg G.]

I read this as:

You can build a splitter, but it can't extend beyond (in front of) the stock fascia of the car. It can't extend more than 5" beyond the side of the car (width). It can't have anything but a flat shape, or you take points for canards.

 

When you say "5" outwards from bumper" that might bring you into conflict with the not past the stock fascia provision, if it's your intention to extend it forwards.

 

But I'm not an expert. C5 generally don't do aero in TTA (no points left).

Not correct.

2) Add, replace or modify a single front splitter/spoiler/wing/foil +3 (note: This part may extend horizontally past the side of the vehicle no greater than five inches. If any portion of this part that protrudes from the side of vehicle is not parallel to the ground, then additional points must be assessed for canards in G.4) below.)(note: No material or part may extend the vertical reach of the OEM front fascia without taking fascia modification points above.)

 

There is nothing that prevents the splitter from being in front of the OEM fascia.

 

- attached to? - bumper directly?? How far can I drop it down from the bumper without it counting as an air dam?

 

It must be attached directly to the OEM fascia. If you drop it down from the OEM fascia/bumper at all, it will incur points for Air Dam/Fascia modification.

 

(note: No material or part may extend the vertical reach of the OEM front fascia without taking fascia modification points above.)

 

Vertical means "up and down". If you drop the splitter down below the OEM fascia, you are creating a non-OEM air dam.

[boomn29]

There is nothing that prevents the splitter from being in front of the OEM fascia.

For Clarification 5" laterally on either side is permitted correct? And I don't see any limitations on the longitudinal length in front of OEM Fascia listed so sounds like it's unlimited.

 

It must be attached directly to the OEM fascia. If you drop it down from the OEM fascia/bumper at all, it will incur points for Air Dam/Fascia modification.

 

(note: No material or part may extend the vertical reach of the OEM front fascia without taking fascia modification points above.)

 

Vertical means "up and down". If you drop the splitter down below the OEM fascia, you are creating a non-OEM air dam.

Ok, going to take this a step futher for clarification:

Essentially if we hold up a flat splitter to the underside of the OEM fascia but can also mount to the Rad support for added strength. this is a +3 mod. A +6 mod would be if we had a new 90 deg close out panel between the splitter and OEM Fascia. What if we had a flat splitter but it was mounted lower than OEM Fascia but no close out panel was installed between the OEM Fascia and new splitter(air gap is between the two? Lastly if we did the latter and had a small 90 vertical panel mounted to the splitter but it did not touch the OEM Fascia in any way (air gap between the two) how many points for this?

[Greg G.]

Ok, going to take this a step futher for clarification:

Essentially if we hold up a flat splitter to the underside of the OEM fascia but can also mount to the Rad support for added strength. this is a +3 mod. A +6 mod would be if we had a new 90 deg close out panel between the splitter and OEM Fascia. What if we had a flat splitter but it was mounted lower than OEM Fascia but no close out panel was installed between the OEM Fascia and new splitter(air gap is between the two? Lastly if we did the latter and had a small 90 vertical panel mounted to the splitter but it did not touch the OEM Fascia in any way (air gap between the two) how many points for this?

 

Yes, you can mount it to the radiator support for added strength.

Yes, it would be a +6 point mod if you put in a 90 degree panel between the splitter and the OEM fascia.

If you mounted the flat splitter with an air gap then it would be a worthless as a splitter, and you would have to angle it and basically make a front wing/foil out of it.

If you put the splitter low, with a 90 degree panel, and it did not touch the OEM fascia, then you have just entered the realm of this:

A permitted item cannot be modified to perform either a prohibited function, or the function of an

item that would otherwise be assessed points under the modification rules.

 

Let's say you left a 1 micron air gap between the OEM fascia and the 90 degree panel. You have just functionally created a new air dam. Widening that gap is just a matter of semantics. You would still take the +3 for air dam/fascia.

[boomn29]

All making sense - thanks Greg.

 

I see it noted in #6 of the Aero rules that a rear diffuser can have vertical panels up to 5" built in it.

 

6) Add rear diffuser (note: additional points must be assessed for any vertical panels incorporated into a rear diffuser that are greater than five inches in height---G. below) +2

I know the front splitter itself needs to be flat and not angle up at the sides to represent a canard or anything. But in reference to the parts of the splitter that do NOT stick out from the bumper, can we do what we want? Are we free to angle the front splitter or incorporate veins or vertical panels in it specifically underneath the car?

 

Here's an example of some angles built into a splitter. The angled part would be 100% underneath the car.

[Greg G.]

I don't see anything in the rules that would make it legal, which would make it illegal (or at least an item that could be protested as being illegal).

[MSP608]

This counts only as an airdam/fascia modification right?

 

 

No part of it sticks out, it mounts flush with the vertical plane of the fascia.

[jvetthead]

Wait a sec... Last year there was a line in the rule that said may not extend PAST the verticle reach of the oem facia.

 

I read this as:

You can build a splitter, but it can't extend beyond (in front of) the stock fascia of the car. It can't extend more than 5" beyond the side of the car (width). It can't have anything but a flat shape, or you take points for canards.

 

When you say "5" outwards from bumper" that might bring you into conflict with the not past the stock fascia provision, if it's your intention to extend it forwards.

 

But I'm not an expert. C5 generally don't do aero in TTA (no points left).

Not correct.

2) Add, replace or modify a single front splitter/spoiler/wing/foil +3 (note: This part may extend horizontally past the side of the vehicle no greater than five inches. If any portion of this part that protrudes from the side of vehicle is not parallel to the ground, then additional points must be assessed for canards in G.4) below.)(note: No material or part may extend the vertical reach of the OEM front fascia without taking fascia modification points above.)

 

There is nothing that prevents the splitter from being in front of the OEM fascia.

 

- attached to? - bumper directly?? How far can I drop it down from the bumper without it counting as an air dam?

 

It must be attached directly to the OEM fascia. If you drop it down from the OEM fascia/bumper at all, it will incur points for Air Dam/Fascia modification.

 

(note: No material or part may extend the vertical reach of the OEM front fascia without taking fascia modification points above.)

 

Vertical means "up and down". If you drop the splitter down below the OEM fascia, you are creating a non-OEM air dam.

[Greg G.]

Wait a sec... Last year there was a line in the rule that said may not extend PAST the verticle reach of the oem facia.

 

No, there wasn't. The wording is the same as it was in 2009 and 2010. The word "past" is not there.

[jvetthead]

Of course you are correct.

So I went through the archives trying to find the source of my confusion. not an easy task.

Needless to say I could not find anything, but I did find this little gem that I thought was funny... I think it will be a good sig.

 

Greg G. wrote:

The aero rules are simplified this year, as you will see.

 

http://www.nasaproracing.com/rules/2009/pt.pdf

[boomn29]

There is nothing that prevents the splitter from being in front of the OEM fascia.

 

- attached to? - bumper directly?? How far can I drop it down from the bumper without it counting as an air dam?

 

It must be attached directly to the OEM fascia. If you drop it down from the OEM fascia/bumper at all, it will incur points for Air Dam/Fascia modification.

 

(note: No material or part may extend the vertical reach of the OEM front fascia without taking fascia modification points above.)

 

Vertical means "up and down". If you drop the splitter down below the OEM fascia, you are creating a non-OEM air dam.

Got a pic for reference. Here's a splitter attached directly to the oem bumper/fascia. No gap, no vertical canards - just a flat piece that is < 5" extended. Should be about as simple as we can get for a 3pt 'splitter' correct?

 

 

And installed:

[Greg G.]

correct.

[GeneSplicer]

Hmmm, so what classifies as OEM fascia? I had added an OEM lip to my miata, but it was not a base option. Added venting for brake and radiator cooling (then the splitter), but since it was added, does it fall into the airdam category? If so is this a 6pt mod? Pic for clarification:

 

[Greg G.]

Yes, with the aftermarket fascia/Air dam mod, and the splitter, it is +6 points. It doesn't matter who makes the aftermarket part, whether it is the OEM (Mazda, Mazdaspeed), or someone else. If the base trim model of the vehicle does not come with it, then it is assessed points.

[GeneSplicer]

Bummer - that's what I was thinking. Please be kind to my reclassing Mr. G - Top of TTA is only a couple points away should you class me in TTB**

[clydesdale]

Had this undertray/splitter not extended forward or laterally at all from the fascia and not extended backward past the front axle line, it would indeed be a zero points undertray correct? Even if it already makes sense, sometimes I just need to ask to make sure I didn't miss something.

 

And installed:

[Greg G.]

Had this undertray/splitter not extended forward or laterally at all from the fascia and not extended backward past the front axle line, it would indeed be a zero points undertray correct? Even if it already makes sense, sometimes I just need to ask to make sure I didn't miss something.

 

And installed:

Randy,

 

Beside not extending forward of the fascia, it would have to attach such that the leading (front) edge would have to be flush with the bottom of the fascia. From the photo you have show, if you moved that splitter backward 3 inches and trimmed off the outside edges, even if the leading edge would not be in front of the fascia, it would still catch air between the bottom of the fascia and the "undertray", and would take points. An undertray should not have air dam or splitter properties. It should be flush to the bottom of the vehicle.

[clydesdale]

So just getting rid of the gap by making it flush horizontally at all points across the fascia will suffice (as shown below)? Are there limitations as to whether the undertray is flat, formed or vented?

 

[2bars]

wow! are you being sarcastic or are you jotting down all the false statements from this thread?

 

i can tell you guys one thing for sure. if your splitter doesn't stick out past the furthest point of your bumper at all, you lose effect bigtime. this is from articles in GRM, racecar engineering, and personal experience. it doesn't have to stickout alot, just an inch or two makes a big difference. on my miata, 2'' past the furthest point (in this case the bumpers beltline) meant that my splitter stuckout nearly 6'' from the bottom of the bumper where it makes contact. don't get me wrong, on a car that gets "light" upfront at high speeds, a small splitter still makes a noticeable reduction of lift. but when i had it protude past the beltline, i found that i didn't have enough wing on high speed corners. i'm going to add a gurney flap to see if i can get the balance back how i like, if not i can trim the splitter back a little.

[clydesdale]

Here is Simon MacBeath with a short paper in which he writes about using CFD on airdams and splitters:

http://www.nptec.com/imgsti/aerobytes.pdf

 

I don't want a splitter, I want a no-points undertray to replace my tattered plastic one.

[MSP608]

So just getting rid of the gap by making it flush horizontally at all points across the fascia will suffice (as shown below)? Are there limitations as to whether the undertray is flat, formed or vented?

 

http://www.nptec.com/imgsti/undertray.jpg

I'd like to hear the answer to this.

 

I'm assuming if Greg says undertrays must be flat, then you would have to trim it so it would fit flush in the middle, but fit behind the little extensions on that fascia. If that explanation makes any sense.

[clydesdale]

I'd like to hear the answer to this.

 

I'm assuming if Greg says undertrays must be flat, then you would have to trim it so it would fit flush in the middle, but fit behind the little extensions on that fascia. If that explanation makes any sense.

 

What you say makes complete sense. I was tempted to draw a dotted line at exactly the position you suggest. The problem I'm having is that portions of the engine and engine mounting will actually interfere with a flat undertray if it needs to be tucked in behind the raised center of the fascia. The OEM undertray curves upward to mount in that spot as it is.

[Greg G.]

I.g.1:

1) Undertray/ belly pan forward of the centerline of the front axle

 

Since you cannot put a piece such as the splitter shown directly under the center section of the fascia without taking points for "splitter", and you cannot just block off that area without taking points for "fascia/air dam mod", It would seem that on your vehicle, you would either have to fashion an undertray that does follow the shape of the OEM lower fascia edge, or move it back and raise it sufficiently that it would be behind the center of the fascia and high enough to not not cause a splitter or fascia mod points assessment. In the first case, it would seem that it would necessarily have to be a shape other than flat, at least at the most forward aspect. The rule does not specifically state flat, although most conventional wisdom would be that the other name for putting on an undertray or belly pan is to "flatbottom" the car. I would see this as an item that could potentially get protested if the build is such that it violates the cardinal rule in TT/PT:

If a performance modification is not specifically allowed by the rules, it is prohibited. A

permitted item cannot be modified to perform either a prohibited function, or the function of an

item that would otherwise be assessed points under the modification rules.

So, there is no mention of fancy vents or shapes in the rules, so be cautious. I would think that a simple formed tray, that starts with the shape of the bottom of the OEM fascia, and blends into a flat piece (or retains the OEM fascia shape back to the front axle) would be legal.